Paragon Clinical Factors of Importance to Successful Implant Therapy by Dr.Niznick

I .•·

�Clinical Factors of Importance to Successful Implant Therapy

' 1 )

�

7 ' J )

J '

Supplement to Journal of Oral and Maxillofacial Surgery Volume 55, Number 12 Supplement 5, December 1997 Official Journal of the American Association of Oral and Maxillofacial Surgeons

Journal of Oral and Maxillofacial Surgery EDITOR-IN-CHIEF Daniel M. Laskin EDITOR EMERITUS James R. Hayward ASSISTANT EDITORS Leon A. Assael

Raymond P. White Jr

SECTION EDITORS Edward Ellis Ill

Robert D. Marciani

Oral and Maxillofacial Surgery

Jeffrey B. Dembo

Clinical Controversies

Thomas P. Williams

Anesthesiology

Clinicopathologic Conferences

Ellen Eisenberg

Michael C. Matz.kin

Charles Liebow

Janie Dunham

Pathology

Research

Current Uterature

News

Joseph E. Van Sickels Current Therapy

EDITORIAL BOARD R. Bruce Donoff Raymond J. Fonseca Steven M. Roser INTERNATIONAL CONSULTANTS Jose Luis Ferreria

Buenos Aires, Argentina

Christian Lindqvist

Helsinki, Finland

Gyorgy Szabo

Budapest, Hungary

STATISTICAL REVIEWER Alvin M. Best PUBLISHER W.B. Saunders Company

A Division of Harcourt Brace & Company

Philadelphia, PA

Harry A. Dean Jr,

Vice-President and Director, Periodicals

Leonard B. Charles Bertola:rrti Felice S. 0

PREFACE

and human resources between the Department of Veterans Affairs, Office of Dentistry and private industry to support independent clinical studies on dental implants. These studies document the influence of critical variables associated with the clinical performance of endosseal implants of various designs and mate rials. The DICRG is pleased to have its stage I stage II results published in this special issue. The comprehensive nature of the information, made possible by the large database and number of vari-

ables, makes this issue a valuable reference for den tal implant professionals. HAROLD F. MORRIS, DDS, MS SHIGERU 0cm, PhD

References 1. National Institutes of Health: National Institutes of Health con sensus development conference statement on dental implants, June 13-15, 1988. J Dent Educ 52:824, 1988 2. Morris HF, Oehl S, Dental Implant Clinical Research Group (Plan ning Committee): The influence of implant design, application, and site on clinical performance and crestal bone: A multicenter, multidisciplinary clinical study. Implant Dent 1:49, 1992

J Oral Maxillofac Surg 55:4-6, 1997, Suppl 5

Acknowledgments

These ongoing clinical studies are being supported by the Department of Veterans Affairs (DVA) and the Gerald A. Niznick Foundation, Los Angeles, CA. Spectra-System dental implant materials-Screw Vent, Bio-Vent, Micro-Vent and Core-Vent Im plants-were donated by Core-Vent Corporation, Las Vegas, NV. Limited donations of other support products were made by the following: Peridex oral rinse was supplied by Procter & Gamble, Cincinnati, OH; Reach tooth brushes were supplied by Johnson & Johnson Dental Products, New Brunswick, NJ; Interproximal brushes, toothbrushes, and dental floss were supplied by Lac tona Corporation, Montgomeryville, PA; Interplak toothbrushes, toothpaste, and replacement brush heads and Interprobe system materials were supplied by Bausch & Lomb, Oral Care Division, Tucker, GA; scaling gel and disposable prophy angles were supplied by Dentsply ASH-USA Division, York, PA; impres sion materials were supplied by 3M Health Care Dental Products Division, St Paul, MN, GC America, Chi cago, IL, and Parkell Products, Farmingdale, NY; pre cious metal alloys were supplied by J.P. Jelenko & Co, Armonk, NY; freeze-dried demineralized bone was supplied by Michigan Tissue Bank, Lansing, MI, and Pacific Coast Tissue Bank, Los Angeles, CA (Dembone and Lambone); and resorbable hyclroxyapa tite (OsteoGen) was supplied by Impladent Ltd, Hol liswood, NY. A multicenter clinical study requires the cooperation and enthusiastic support of many people over an ex tended period of time. This project has benefited from the dedication of many participants and supporters in terested in conducting a well-designed and executed scientific investigation. This coordinated effo11 has re sulted in valuable implant therapy for patients, collec tion of relevant data, development and analysis of a large database, and release of significant results to the dental implant community. Initiation of these studies entailed the efforts of many people, not only those now directly involved but also those who offered their advice in numerous planning sessions. Some of the members of the original

planning committee continue to serve on a committee that makes executive decisions. This project was first reviewed and approved by the Research and Development Committee and Human Studies Committee of the project office (V AMC Ann Arbor). In addition, appropriate local review and ap proval were received by each participating medical center. The efforts of members of these committees in this research endeavor are gratefully acknowledged. This project has been fortunate to have an external review/scientific advisory committee that has been most helpful in providing guidance to this project. This committee, which reviews the studies annually, is an independent body with the power to stop or modify these studies if it determines that patient safety or sci entific conduct is compromised. The members of this committee, well-recognized authorities in their respec tive fields, have monitored data trends and offered val uable suggestions on specific analyses. To prevent po tential conflicts in reporting outcomes, the database and masked treatment data remain under control of the DICRG project office. Those providing financial support have not had access to the database. We gratefully acknowledge the dedication and con tributions of the clinical investigators, who have often spent time outside of assigned duties to collect and record data. Former clinical investigators include John R. Blankenship, Michael Buckley, Steven Dannenberg, Bruce M. Davenport, Robert E. Davenport, Daryl J. Detwiler, Tim Donley, Bennie S. Dukes, Sam E. Far ish, Eugene E. Fischer, Daniel D. Gammage, Norman Glasscock, Allen F. Goldberg, Richard K. Gangloff, Foster V. Hall, J. Theodore Jastak, Donald Kalant, J.H. Knight, Howard L. Lapidow, Felix R. Lawrence, Michael T. Mackey, Donald J. Manthe, Terry G. O'Toole, James L. Pansch, Lawrence E. Scheitler, Coleman J. Spector, William J. Synan, Victor P. Terra nova, Kenneth V. Visconti, and Cullen C. Ward. The project office also acknowledges the contributions of former administrative assistant Beverly Barnes. The Journal of Oral and Maxillofacial Surgery ac knowledges the support of Gerald A. Niznick, DMD, MSD, which has made the publication of this supple ment possible.

ACKNOWLEDGJ\IIENTS

Clinical Centers and Investigators, Group A Los Angeles VA Outpatient Clinic-Robert J. Dent, DDS,* and Mark L. Monson, DDS University of Louisville (KY)-Connie Drisko, DDS, Zafrulla Kahn, DDS, MS, and John W. Olson, DDS, MS* University of Pennsylvania (PA)-Dexter Barber, DDS,* Keith M. Phillips, DMD, and Robert J. Seck inger, DMD VAMC Hampton (VA)-Thomas Forgeng, DDS,* and Val Gibberman, DDS VAMC Huntington (WV)-Damon E. Coffman, DDS,* Stanely E. Dixon, DMD, and Winfield C. John III, DMD VAMC Iowa City (IA)-Robert J. Luebke, DDS,* MS, and Sherwood H. Wolfson, DDS VAMC Louisville (KY)-Paul X. Dattilo, DMD, John T. Dominici, DDS (following patients at Lexington VAMC), John W. Olson, DDS, MS,* and James W. Shaughnessy, DMD VAMC Manhattan (NY)-Gregory K. Kazandjian, DDS, Eileen B. Kronenberg, DMD, Steven N. Ro senberg, DDS, and Jeffrey L. Tarlow, DDS* VAMC North Chicago (IL)-Peter A. Bidny, DDS,* B. Frank Kepley, DMD, and Terry R. Schmidt, DDS VAMC Pittsburgh (PA)-Roger B. Cwynar, DMD, Peter N. Demas, DMD, and Warren M. Stoffer, DMD* VAMC Portland (OR)-Larry B. Thompson, DDS, MS, and J. Ernest Weinberg, DMD, MSD* VAMC Richmond (VA)-C. Daniel Dent, DDS, Wil liam E. Hunter, DDS,* and Lawrence E. Masters, DDS VAMC San Diego-George W. Carroll, DDS, MS, and John H. W. Gelles, DDS* VAMC San Francisco-Richard Navarro, DDS, MS, Rebeka G. Silva, DMD, and Dennis J. Weir, DDS, MA* VAMC San Juan (Puerto Rico)-Antolino Colon, DMD,* and Manuel A. Ortiz, DMD VAMC Seattle (WA)-Randall R. Sobczak, DDS* VAMC Sepulveda (CA)-Mark L. Monson, DDS, and Lori A. Walker, DDS* Clinical Centers and Investigators, Group B Hines VA Hospital (IL)-Eugene M. Riehle, DDS,* and Charles H. Stuever, Jr., DDS Honolulu VA Outpatient Clinic (Hl)-Gilbert H. Lar son III, DDS, and Boyden S. Yamashita, DDS, MPH* VAMC Ann Arbor (Ml)-James F. Pikulski, DDS* VAMC Bronx (NY)-Ira H. Orenstein, DDS,* and Thomas E. Porch, DMD * Principal Investigator

VAMC Brooklyn (NY)-Sidney R. Kupfer, DDS,* and I. Michael Postol, DDS VAMC Buffalo (NY)-Frank R. Lauciello, DDS,* John F. Mozrall, DDS, and William V. O'Neil, DDS VAMC Dayton (OH)-John A. Bucher, DMD, James R. Cole, DDS, Ralph Eichstaedt, DDS, Lisa M. Gor man, DDS, and Paul M. Lambert, DDS* VAMC Houston (TX)-Allan W. Estey, DDS, Harry D. Gilbert, DDS,* and George V. Goff, DDS VAMC Indianapolis (!NJ-Samuel Campbell, DDS, William B. Gillette, DDS,* George E. Lanning, DDS, Robert Matthews, DDS, MSD, and Steven Porter, DDS VAMC Kansas City (MO)-James L. Beatty, DDS, John Bellome, DDS,* Richard J. Crosetti, DDS, Douglas A. Pearson, DDS, Rosa B. Solomon, DDS, and Amos R. Williams, DDS VAMC Little Rock (AR)-John J. Gary, DDS, Arthur G. Howe, DDS,* Jerry L. Neidlinger, DDS, and John R. Spray, DDS VAMC Northport (NY)-James J. Cancro, DDS, An thony J. Casino, DDS,* and Richard S. Truhlar, DDS VAMC Northport (NY)-James J. Cancro, DDS, An thony J. Casino, DDS,* and Richard S. Truhlar, DDS VAMC St Louis (MO)-William E. Rowe, DDS, and John J. Wahle, DDS* VAMC Washington DC-Michael T. Curran, DDS,* and R. Dale Welch, DDS* William Jennings Bryan Dorn Veterans' Hospital (Co lumbia, SCJ-George A. Brooks, DDS, James R. Sanner, DMD, and John C. Stuart, DMD* Laboratories Den-Tee Laboratory Inc., Westland, Ml-Alan R. Helisek, CDT, and Stacy Ziecina DVA Central Dental Laboratory, Dallas, TX-Eugene Jones, DDS, MS DVA Central Dental Laboratory, Washington, DC John McCartney, DDS Project Office and Data Management Center VAMC Ann Arbor (Michigan)-Harold F. Morris, DDS, MS,t Shigeru Ochi, PhD,t Michael Manz, DDS, MPH, Jeanne Middlebrook, Leigh Ann Rad cliffe, and Janet Tarolli, RN, BSN. Project Faculty Gerald A. Niznick, DMD, MSD, Core-Vent BioEn gineering (Calabasas Hills, CA); and Daniel R. t Project Codirector

ACI0iOWLEDGMENTS

Patrick, DDS, MSD, Dentsply/Implant (Encino, CA). Planning Committee William B. Gillette, DDS, VAMC Indianapolis (IN); Norman D. Glasscock, DDS, VA Central Office, Washington, DC; Alan R. Helisek, CDT, VAMC Ann Arbor (MI); Eugene Jones, DDS, VAMC Dallas (TX); Paul Lambert, DDS, VAMC Dayton (OH); Frank R. Lauciello, DDS, V AMC Buffalo (NY); Gregory Movsesian, DDS, VAMC Allen Park (MI); Richard Plezia, DDS, MS, VAMC Allen Park (MI); Eugene M. Riehle, DDS, Hines VA Hospital (Hines, IL); Warren Stoffer, DMD, VAMC Pittsburgh (PA); and Dennis Weir, DDS, MA, VAMC San Francisco (CA).

Scientific Advisory/External Re iew Committee

Voting Members-Jack E. Lemons, PhD, University of Alabama (Birmingham) (Chairman); Charles English, DDS, VAMC Augusta (Georgia); Daniel M. Laskin, DDS, MS, Medical College of irginia (Richmond); Robert E. Lorey, DDS, MS, niversity of Michigan (Ann Arbor); Chester Paczko ski, DDS, VA Central Office (Washington, DC); W. Eugene Roberts, DDS, PhD, Indiana University (Indianapolis); Charles ShipÂ man Jr, PhD, University of Michigan (Ann Arbor); and Dennis P. Tarnow, DDS, Te York University (New York); Observers-P.L. Fan, PhD, American Dental Association (Chicago); George McCarthy, DDS, National Institute of Dental Research (Bethesda); and Wayne ozniak, PhD, American Dental Association (Chicago)

J Oral Maxillofac Surg 55:7-11, 1997, Suppl 5

Introduction that clinical trials should define "success" and "failure" clearly, standardize reporting methods and treatment out come measures, and document all implant failures com pletely. In 1991 the Dental Implant Clinical Research Group (DICRG) began a prospective, multicenter project using two independent study groups to provide scientific data directly relevant to Spectra-System endosseous root-form implants (Core-Vent Corporation, Las Vegas, NV). The DICRG project, which runs through 1998, considers the relationship of implant design, application, and intraoral location as it relates to quantitative measures of clinical performance and crestal bone height. 5

In 1988 the National Institutes of Health Consensus Conference on Dental Implants found some aspects of the existing evidence for the long-term effectiveness of dental implants to be deficient. 1 For proper compari sons between implant designs, research protocols such as those found in randomized and controlled trials are necessary, but such comprehensive clinical trials had not been performed. When case series studies capable of providing ''limited evidence when proper methods are used'' were examined, they were found generally not to follow the rigorous principles recommended by the consensus conference panel. Research and technology related to root-form im plants were judged to have advanced in several areas. Results showed that keeping the temperature of the bone below a certain critical level during site prepara tion and protecting the newly inserted implant from functional forces were important. 2• Also, the best long term survival rates for root-form implants had been achieved with systems that had bone at the interface. 2.4 Case series studies, some of which had lasted 10 years or more, had shown that dental implants could be suc cessful in the long term. 1 Inadequacies in the knowledge base related to mate rials and designs were identified, specifically the fol lowing:

Method

Participants

Veterans eligible for dental tTeatrnent at 30 Department of Veterans Affairs Medical Centers nationwide and pa tients from two dental schools were entered into these studies between January 1991 and August 1995. They ranged in age from 20 years to more than 80 years and constituted a largely white male sample, with representa tion of blacks, Latin Americans, Asians, and Native Americans (Table 1).6 Comprehensive medical and dental histories were taken. Patients had to be able 1) to benefit from treatment by endosseous dental implants and 2) to give informed consent and sign the study consent form. In addition, patients had to have adequate bone for the placement of endosseous implants. In general, a patient with severe systemic disease, termi nal illness, or moribund status was excluded. Specific rea sons for exclusion included insulin-dependent or uncon trolled diabetes; collagen disorders, such as lupus erythematosus or scleroderma; hepatitis; leukemia; mental incompetence; hemodialysis; long-term steroid therapy, ra diation therapy in the past or planned for the future that would affect the site of implant placement; heart surgery in the last 6 months; extraction at the site of the implant within the last 6 months; or bone grafting within 12 months. Discretionary factors that could exclude a patient were altered manual dexte1ity, psychiatric problems, sub stance abuse, unrealistic expectations, poor motivation, poor oral hygiene, a metabolic disorder, chronic nephritis, or anticoagulant therapy.

• characteristics of implant surfaces • health risks related to the release of trace elements from implants • wound repair at the implant-host interface • tissue adaptation in the peri-implant region • the transfer of force to the tissues In addition to these basic research problems, the con ference identified the following factors related to the long-term effectiveness of dental implants that would be best investigated within prospective, multicenter clinical studies: • • • • • •

implant characteristics operator skill tissue management patient characteristics prosthetic considerations causes of implant failure-medical, psychologi cal, and periodontal

Administration The 32 clinical centers were divided into two inde pendent study groups, A and B. Clinical investigators

At the consensus development conference, it was agreed 7

10 Table 3.

Prostheses in the DICRG Study Strata

Completely Edentulous Maxillary Anterior

Prosthesis Bar-retained overdenture Fixed detachable denture Single crown

Mandibular Anterior

Maxillary Posterior

edentulism, and single tooth rep�et::10:li same over the 5-year period. c. The success rates for implan in and maxilla versus mandible ,,ill period. ·tind. The losses of crestal bone around lll)it:a::,, der, grooved, and basket designs ,,ill pe1iod. e. The complications and ad,·erse respocse:, � with different implant designs will be the� period.

location. For most of the articles in this issue, analyses were performed on data up to and including sw-gical un covering. Results are given separately for stage I and stage II of implant treatment as well as stage I and II combined. The time between surgical placement and surgical uncov ering is stage I; the time of sw-gical uncovering is stage II; the time between sw-gical uncovering and occlusal load ing is stage Ill; and the time after occlusal loading is stage IV. One interim report includes data collected after functional loading. Whereas outcomes such as failure rates are analyzed by stage of n·eatment (I, II, or both), the data in the interim report on bone loss is presented by follow up visit. Standardized radiographs were used to evaluate the height of the crestal bone adjacent to the implant and to evaluate the changes in the architecture of the supporting bone at the bone-implant interface. Comparative analyses of these radiographs were performed at a central location and include both qualitative and quantitative components. Statistical techniques have been described in a previous report.5 From a statistical viewpoint, the primary unit is the prosthesis, the secondary is the implant. The primary hypothesis provided the basis for the development of the experimental design and the estimation of sample size. Together with the secondaty hypotheses, it will guide the reporting of outcomes after 5 years of follow-up:

c:·

A prosthesis is considered uccessfuJ ·- ·. ·- functional for 5 years. Failure of a prosthe is is fined i removal when it is no longer functional. of function of the prosthesis is associated with the I plants. Implant failw-e is defined implant for one or more of the follm,ing reas<xlS: implant mobility when tested, evidence of complete pen-implant radiolucency, or persistent pain, discomfort. or infection that is not resolved with the use of antibiotics or local n·eatment and occurs more than three times and requires treatment during the first year after loading. In rrea.trnent of edentulism, the removal of an implant may not jeopar dize the placement or survival of the prostb is because as many as five or six implants may have been placed for its support. In the case of single-tooth replacement. failure of the implant results in failure of the prosthesis. Because dw-ing stage I and at stage II uncovering sw-gery no pros thesis has been placed, "case" refers to that group of implants for which a prosthesis is planned. Most articles present results for the preload period, from implant placement through second-stage uncov ering sw-gery. However, in one article, the one dealing

Primary- The implant-suppo11ed prosthesis will be func tional over a 5-year pe1iod in at least 90% of the cases treated in this study regardless of implant design, application, and location. Secondary-a. The success rates among implants with screw, cylinder, grooved, and basket designs will be the same over a 5-yeat· period. b. The success rates for implants used for edentulism, partial Table 4.

Partial!

Patients Excluded by Results of the Screening and History Form

Study Status

Patients in Study Group A (n = 402)

Patients in Study Group B (n = 427)

Total Patients, Group A+ B (n = 829)

Excluded Inclusion criteria not met Met one or more exclusion criteria Met one or more discretionary exclusion criteria Excluded for reason(s) on medical/dental history Included (on-study)

14 3 7 0 4 388

12 2 7 0 3 415

26 5 14 0 7 803

Source:

DICRG Form QI-Patient Screening and History.

J Oral Maxillofac Surg 55:12-18, 1997, Suppl 5

Positive Effect of Surgical Experience With Implants on Second-Stage Implant Survival PAUL M. LAMBERT, DDS,* HAROLD F. MORRIS, DDS, MS,t AND SHIGERU OCHI, PHO+ This Dental Implant Clinical Research Group study defined a learning curve for dental implant placement. Implants placed by inexperienced surgeons ( <50 implants) failed twice as often as those placed by experienced surgeons (2c50 implants). Implants placed during the first 6, 8, 10, 12, and 16 cases were compared with all others. The greatest difference was seen between the first nine cases and all others (P = .001), with later cases failing significantly less often. Inexperienced surgeons had more failures in the first nine cases (5.9%) than more experienced surgeons (2.4%). Surgeons with little or no previous experience must expect a definite learning curve. Previous experience may transfer and result in a shallower learning curve for subsequent systems. The number of dentists who place dental implants and the average number placed have grown clramati cally in the past decade. Between 1986 and 1990, the number of periodontists placing implants rose by 300%, the number of oral and maxillofacial surgeons by 72%, and the number of general dentists by 21%. The number of implants placed by each group in creased by 99%, 121%, and 129%, respectively.1 Only 89% of dentists in this survey who had actually placed implants reported receiving formal training in the pro cedure. Based on these data, it follows that every year practitioners with little or no dental implant experience begin placing dental implants. Although the effect of provider experience has been widely studied in medi-

cine and surgery, research conducted into its effects on outcome of dental implant therapy has been very limited. Several authors have reported significant learning curves for various surgical procedures, including lapa roscopic cholecystectomy, angiography; femoral ar throplasty, colonoscopy, carotid endarterectomy, and transurethral lithotripsy. 2·7 Callaghan et al8 measured acetabular and femoral fit, femoral canal filling, and acetabular cup angle in two consecutive groups of 50 primary, uncemented porous-coated anatomic hip ar throplasties. They found a significant improvement in these parameters in the second group and concluded that there is a definite learning curve in mastering the technique. There have also been reports comparing hospital volume, surgeon production, and treatment outcome. When more treatments of a particular type are provided by hospitals, these hospitals experience better patient outcomes than do hospitals that treat fewer patients.9• In a recent report, Hannan et al 11 pointed out that six studies found significantly lower mortality rates for hospitals performing higher volumes of coronary sur gery, and one study found that the mortality rate de creased significantly with increasing surgeon volume. In their own study, crude mortality rates for the three hospital volume ranges decreased from 5.38% (for hos pital volumes 1 to 199), to 4.09% (for volumes 200 to 889), to 3.08% (for volumes 890 and greater). Simi larly, risk-adjusted mortality rates decreased from

* Chief, Dental Service, Department of Veterans Affairs Medical Center, Dayton, OH; Assistant Professor, College of Dentistry, The Ohio State University, Columbus, OH; Assistant Clinical Professor, School of Medicine, Wright State University, Dayton, OH. t Codirector, Dental Clinical Research Center; Project Codirector, Dental Implant Clinical Research Group, Department of Veterans Affairs Medical Center, Dental Research, Ann Arbor, Ml. :j: Codirector, Dental Clinical Research Center; Project Codirector and Biostatistician, Dental Implant Clinical Research Group, Depart ment of Veterans Affairs Medical Center, Dental Research, Ann Arbor, MI. Address correspondence and reprint requests to Dr Morris: De partment of Veterans Affairs Medical Center, Dental Research (154), 2215 Fuller Rd, Ann Arbor, MI 48105.

This is a US government work. There are no restrictions on its use. 0278-2391/97/5512-5008$0.00/0

LAMBERT ET AL

7.25% to 2.85%. They also showed a similar impact of surgeon volume on mortality rates. Crude rates de creased from 9.09% (for surgeon volumes 1 to 54), to 6.01% (for volumes 55 to 89), to 3.31 % (for volumes 90 to 259), to 2.89% (for volumes above 260). Risk adjusted mortality rates followed the same monotonic decrease for the same four groups, decreasing from 8.14% to 2.43%. As a result of these so-called volume outcome measures, some hospitals with inadequate volume have already ceased to provide some services, and others are beginning to require members of their medical staffs to document completion of a specified number of certain procedures on an annual basis as a measure of current competence to maintain privileges to provide those procedures. The Dental Implant Clinical Research Group (DICRG) is conducting an 8-year, randomized, pro spective clinical study in cooperation with 30 Depart ment of Veterans Affairs (DVA) medical centers and two dental schools. 12 The participating centers are di vided into two independent but parallel study groups, A and B. Each study group functions under the leader ship of separate co-chairs. This study investigates the influence of implant design, application, and site of placement on clinical success and crestal bone height. The extensive data collected by this study on each participant include dental histories, details of implant insertion, subsequent uncovering, periodontal evalua tions, prosthesis fabrication, oral function, and compli cations. In addition, at the beginning of this study, information was collected regarding the training and experience of providers placing implants. We pre viously reported our initial findings on the relationship between surgical experience and failure rate of im plants at second-stage surgery (uncovering). 13 At that time we reported results based on 1,836 implants fol lowed up to 4 years. In that report, experience was categorized based on the number of implants placed by the responsible surgeon before the study. It was found that implants placed by surgeons who had pre viously placed fewer than 50 implants failed twice as often as implants placed by surgeons who had placed 50 or more. It was also shown that there was a learning curve for this implant system and that the failure rate for implants placed early in the study (first nine cases) was nearly double the failure rate of all cases placed later in the study. By the study's fifth year (April 1995), an additional 805 implants had been uncovered. This article compares current data with our earlier findings and discusses the implications of the changes seen (Fig 1). Patients and Methods

An "Investigator Profile" form was completed at the outset of the study by all participating investigators.

2000

-[ 1500 E

1000 500 0

1994

Year

1995

■

FIGURE 1. Data sets used for original and current analysis ( implants uncovered; implants integrated).

□

The experience (number of implants placed before this study) of the principal surgeon placing implants at each medical center or dental school was determined by the data from the ''Investigator Profile.'' Experience with respect to the implant system(s) used was not identified by the form. The system(s) previously used may not have been the same implants used in this study (Spec tra-System, Core-Vent Corporation, Las Vegas, NV). Two of the participating centers had more than one person placing implants, but information relating only to the principal surgeon has been documented. The success/failure from implant placement surgery to time of uncovering is reported in this analysis. Mo bility, peri-implant radiolucency, or persistent pain, discomfort, or infection attributable to the implant are criteria for implant failure. 13 Implant failures were doc umented on standardized forms that recorded implant location, type of implant, stage of treatment at removal, and reason for removal. The data were tabulated and analyzed at the DICRG Data Management Center in Ann Arbor, Michigan. Second-stage observations were compared to a sur geon's previous experience with implant placement by analyzing pooled data from all participating medical centers and dental schools. To determine whether there was a correlation between implant success at uncov ering and experience gained by a surgeon while partici pating in this study, outcome by order of implant place ment in the study was also examined. Results

In this analysis, 2,641 implants had been uncovered, representing 909 cases in 595 patients. Data were ini tially analyzed for each independent study group. In group A, 1,255 implants were uncovered. Of these, 1,228 (97.8%) were found to be osseointegrated. In group B, 1,386 implants were uncovered. Of these, 1,344 (97.0%) were osseointegrated. Those responsible

14 Table 1.

SURGICAL EXPERIENCE AND IMPLANT SURVIVAL

Analysis of 2,641 Implants in 1995 Survived

Failed

Experience Category

(%)

Many (2:50 implants) Few ( <50 implants) Total

1,356 1,216 2,572

98.2 96.S 97.4

25 44 69

1.8 3.5* 2.6

Total %

1,381 1,260 2,641

51.3 46.0 100.0

* P < .OS.

surgeons who had placed 50 or more implants before this study's initiation were designated as having placed "many" implants, and those who had placed fewer than 50 implants were designated "few." There was an identical number of responsible surgeons in both experience groups (n = 16). There were nine hospitals from group A and seven hospitals from group B in the "many" group; the "few group" included eight hospitals from group A and eight hospitals from group B. Because the number of surgeons in both experience levels was identical, the ratio of hospitals with both "few" and "many" surgeons was closely matched, and there was no statistically significant difference be tween the two groups for integration or any other anal yses, all data were pooled and results are presented for the combined study groups. Most failures were reported to be attributable to fail ure of osseointegration that was discovered at stage II surgery. Table 1 shows the outcome of implants through second-stage surgery compared with implant placement experience of the surgeon. Implants placed by less experienced surgeons failed almost twice as often as those placed by more experienced surgeons (P < .05). An analysis was performed to determine whether a learning curve existed with respect to placement of implants. This was examined by dividing the implants placed during the first 5, 7, 9, 11, and 15 cases from the rest and comparing success rates. The results, shown in Table 2, show that an increasing success rate for im plants placed in the later period was most significant when those placed before the 10th case were compared with those placed with the 10th case or after (P = .001). The distribution of the 69 stage I and II failures among the 2,641 implants is shown by hospital in Fig ure 2. It should be noted that, although the failure rate for all centers was only 2.6%, seven centers had higher failure rates (between 5.4% and 10.3%)-more than twice the failure rate of the study. The seven centers with failure rates above 5% accounted for 35 of 69 (50.7%) of the study's failures (Fig 3). The distribution between the two study groups of these higher failure centers was very similar, with three of them in group A and four in group B.

The order of surgery and implant survival is shown in Table 3. All of the implants placed for case 1 at all hospitals were grouped together, and the number of implant failures and survivors were shown as "order number 1.'' In like fashion, each of the other cases was added across hospitals and reported. Note that there were 30 hospitals that started together at study initiation and that two were added later. The number of cases should total 32 for the first few cases, except that case numbers were assigned to some patients who were subsequently terminated without placement sur gery. Thus, cases 1 and 2 show only 31 cases, whereas case 3 shows 32. A few cases were reported beyond case 39 and are lumped together as case 40. The order of implants placed was separated by the experience level of the surgeon at the start of the study. Figure 4 shows the status of implants placed by those with more experience (surgeons who had placed 50 or more implants before this study began) by order of placement. Figure 5 shows the status of implants placed by those with little experience (surgeons who had placed fewer than 50 implants before this study began) by order of placement. Discussion

We have previously shown that success or failure may be influenced by prior surgical experience with implant placement. At the outset of the DICRG study, 30 centers were chosen to participate. These centers had a mix of dentists with a wide variety of past im plant placement experience. Some participants had never placed implants and were ''coached'' by experi enced operators during their first cases. Some had con siderable experience with other implant systems but not with the implant system used in the study. Still others only had experience with the implants used in this study. With the existing data forms, the particular

Table 2. Implant Survival Experience Among Hospitals: Early Versus Later Cases at Various Division Levels Failures Division Less than 6 Less than 8 Less than 10 Less than 12 Less than 16

Cases Before After Before After Before After Before After Before After

Surviving

20 49 28 41 36 33 39 30 47 22

4.32 2.25 4.09 2.10 4.11 1.87 3.66 1.90 3.40 1.75

443 2,129 656 1,916 839 1,733 1,027 1,545 1,336 1,236

Total

95.68 97.75 95.91 97.90 95.89 98.13 96.34 98.10 96.60 98.25

463 2,178 684 1,957 875 1,766 1,066 1,575 1,383 1,258

.011 .005 .001 .006 .008

LAMBERT ET AL

250,---------------------, I

200

■ Failed CJ Survived

.!!! 150 C: n,

.§ 100

50 0 '--""......................."-"'"-"'._................

L..1,i; ....... "'-"'................"'--"'"-'"...... "-'

01 03 05 07 09 11 13 15 17 02 04 06 08 10 12 14 16 Clinical Centers in Group A

250.--------I

200

■ Failed

---

CJ Survived

--�

.!!! 150 C: 0. .§ 100

50 01

FIGURE 2.

04 06 08 10 12 14 Clinical Centers in Group B

Implant status at stage II uncovering by clinical center:

(A) study group A, 1,255 implants; (B) study group B, 1,386 im

plants.

experience of each surgeon was difficult to ascertain, and any conclusions regarding transfer of experience across different implant systems drawn from these data must be considered with that caution in mind. It should be noted that almost half of the failures that occurred took place at only 7 of the 32 centers. According to data taken from the Investigator Profile form, responsible surgeons at six of these seven centers with the highest failure rates were inexperienced (had placed fewer than 50 implants before entering this study). To determine whether the effect of provider experi ence previously reported persisted, two measures of volume-outcome relationships (previous experience and experienced gained during study) were reexam ined. Table 4 illustrates the provider's surgical experi ence reported in 1994. 13 Surgeons were arbitrarily di vided into two categories based on the number of implants previously placed. The ''many'' category rep-

resented 50 or more implants, and the ''few'' category indicated fewer than 50 implants. The implant failure rate for surgeons who had placed fewer than 50 im plants before this study was more than twice the im plant failure rate for surgeons who had placed 50 or more implants. Using the chi-square test, there was a statistically significant difference (P = .001). Current analysis shows a slight decrease in the dif ference seen earlier. Table 1 shows that the failure rate for surgeons with less experience before this study now only approaches twice that of those with more experience. The failure rate for the more experienced surgeons has remained static at (1.8%), whereas for those with less experience, it has fallen from 4.7% to 3.5%. Between the previous analysis and this one, surgeons with more experience placed 375 additional implants, whereas those with less placed 430 more. This difference may have influenced the decrease in significance, because those surgeons with less experi ence had more opportunity to gain additional experi ence than did those with more experience. It may be reasonable to assume that, as more experience is gained, both groups would eventually approach a com parable level beyond which no further improvement can be achieved. Figure 2 shows the distribution of the 69 stage I and II failures among the 2,641 implants by individual hospital. To provide an idea of how clustered the fail ures were with respect to the order in which they were placed, the implants were divided into groups before and after an arbitrary dividing line, and the percentages of failure and success were compared. These divisions were for "less than 6," "less than 8," "less than 10," "less than 12," and "less than 16" cases. From Table 2, it appears that the division of implants by cases 1

40�- - - - - - - - - - - - - �

Ill

�

'cij

0.5% to 3.9%

5.4% or Higher

30 201-----

--ll -

0. .§

j-- -

o�---

19 Centers

7 Centers

FIGURE 3. Implant failures through stage II uncovering among 26 of 32 DICRG clinical centers by high and low failure rates. Six clinical centers had no implant failures through stage II.

SURGICAL EXPERIE'-CE

Order

Cases (n)

Implants (n)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 and higher Total

31 31 32 31 31 31 31 31 31 31 30 30 28 28 26 27 25 24 23 23 22 23 22 19 19 17 16 15 15 13 11 10 11 11 12 11 11 7 6 63 909

124 91 98 97 84 105 116 103 88 90 100 75 76 78 84 80 73 76 73 55 59 56 58 57 50 49 46 28 40 32 36 23 28 28 27 28 32 15 14 169 2,641

Survival

Failure n

6 0 5 5 5 4 4 5 3 1 1 4 2 0 2 1 4 3 0 0 0 0 2 1 0 2 0 1 1 0 2 0 0 0 1 1 0 1 69

4.8 0.0 5.1 5.2 6.0 3.8 3.4 4.9 3.4 1.1 1.0 1.3 1.3 5.1 2.4 0.0 2.7 1.3 5.5 5.5 0.0 0.0 0.0 0.0 4.0 2.0 0.0 7.1 0.0 3.1 2.8 0.0 7.1 0.0 0.0 0.0 3.1 6.7 0.0 0.6 2.6

118 91 93 92 79 101 112 98 85 89 99 74 75 74 82 80 71 75 69 52 59 56 58 57 48 48 46 26 40 31 35 23 26 28 27 28 31 14 14 168 2,572

95.2 100.0 94.9 94.8 94.0 96.2 96.6 95.1 96.6 98.9 99.0 98.7 98.7 94.9 97.6 100.0 97.3 98.7 94.5 94.5 100.0 100.0 100.0 100.0 96.0 98.0 100.0 92.9 100.0 96.9 97.2 100.0 92.9 100.0 100.0 100.0 96.9 93.3 100.0 99.4 97.4

through 9 versus case 10 or after results in the sharpest difference in failure rates. This effect was still evident with the dividing line set at less than 16 cases. This finding is consistent with our previous report, which showed a significantly lower percentage of failure for implants placed after the first nine cases (Table 5). This comparison was based on analysis of all im plants placed. However, if experienced surgeons (many) and less experienced surgeons (few) are ana lyzed separately, there is a clear distinction between the two groups (Table 6). Experienced surgeons' fail ures for the first nine cases (2.4%) closely approached their overall failure rate for all cases entered into the study that have been uncovered (1.8%). Conversely, the failure rate for less experienced surgeons' first nine

I•

60 50

cca 40 fl)

l3o 20 10 0

L.U.JLIUJLlWc.lUUllll.11.LlIJL.!:..._.______.__.L...1.-L-.....JlJULJ

Order of Surgery: ' FIGURE 4. Implant status at cal case for surgeons who had pb:cl! : study began.

cases (5.9%) was almo t l. ri:ces rate (3.5%). Although this diffcre::ice significant, it does suggest a for more experienced sur0 These findings are similar to and Kent. 14 They compared iheii- cc:��1-ve rates for all implants placed in A "developmental period.. beol was compared with a ''recen peri \-elopand 1991. The cumulati e u mental period was 86.51¾. Thar iI::pro -ed to 97.6% for the recent period. The amhc:Rs eoucf:!rled diat a learning curve does exist for tal imp dierapy. 15 Adell et al also have published - comparing "developmental" groups with l --roorine·· groups.

70..---------- - ---� I

■ Failed

StlM'l'ed

cca 40 fl)

E 30 -

20 _ 10 I 0 �� 3

Order of Surgery: Less Experienced Centers FIGURE 5. Implant status at stage II uncovering by oroer of surgi cal case for surgeons who had placed fewer than -o implants before study began.

LAMBERT ET AL

Analysis of 1,836 Implants In 1994

Table 4.

Survived

Failed

Table 6. Implant Failures for Experienced Versus Less Experienced Surgeons: First Nine Cases

Total

Experience Category

Many (;,,:50 implants) Few (<50 implants) Total

988 791 1,779

98.2 95.3 96.9

18 39 57

1.8 4.7 3.1

1,006 830 1,836

54.8 45.2 100.0

They reported 5-year survival rates for stable prosthe sis-supporting implants in the mandible for the devel opmental group to be 75%; however, routine groups I to ill were 91%, 98%, and 99%, respectively. Routine group m represented those patients completed in the most recent period, when providers had achieved the most experience. In contrast to results we report here, their data reflect completed cases with functional pros theses, and the experience of the surgeon may be masked by that of the restorative dentist. However, it remains clear that experience does affect outcome. Subsequent DICRG reports will begin to study the relation between the combined experience of the sur geon and restorative dentist and the overall success of dental implant therapy. The Armitage-Cochran test was used to determine whether a trend in the proportion of failures by the order of surgery existed. For this analysis, only the first 40 cases were considered. Beyond that point, the number of cases was much smaller and was the result of only two hospitals accounting for the additional data. A test assuming that the underlying distribution is asymptotically chi-square results in a one-sided P .006. That is, the decreasing trend is significant. These results suggest that with increasing experience, the pro portion of implant failures for stages I and II decreases. Figure 4 illustrates the implant outcome of the hospi tals where the surgeon had placed more than 50 im plants before the initiation of the study. Using the trend test, the asymptotic inference provides a P-value equal to .59. This suggests that a trend for a low failure rate as more implants were placed does not exist for this subgroup. Figure 5 shows those hospitals whose re sponsible surgeon had placed fewer than 50 implants before this study began. Using the Armitage-Cochran Table 5.

Previous Implant Analysis in 1994 Survived

Failed

Total

Case Order Division

First nine cases Later cases Total

806 973 1,779

98.2 95.3 96.9

35 22 57

4.2 2.1* 3.1

841 995 1,836

45.8 54.2 100.0

* P = .016.

Survived

Failed

Experience Category

Many (;,,:SQ implants) Few (<50 implants) Total

456 413 869

97.6 94.1 95.9

26 37

Total

2.4 5.9 4.1

467 439 906

51.5 48.5 100.0

trend test, the asymptotic inference provides a P-value equal to .002. The results are statistically significant for a trend of decreasing failures as experience is gained by surgeons with little prior experience. The above comparisons were for subsets dividing hospitals by experience. When all hospitals are consid ered together, as noted earlier, the trend test shows a reduction in failure rate as the case numbers increase, with a P-value of .006. Therefore, when all data are pooled, the results are significant, agreeing with the conclusion reached in 1994. To further confirm this trend analysis, we looked for a trend of decreasing failures after experience with placing 50 implants in this study was gained by both experienced and inexperienced surgeons. There were, on average, 3.5 implants placed per case. Therefore, surgeons would have had experience with this implant system after 15 cases were completed. Experienced surgeons had a significantly lower failure rate (P = .022) for the first 15 cases (2.1%) compared with that of inexperienced surgeons (4.4%). For experienced surgeons, the failure rate did not significantly improve for cases completed after case 15 (1.6%), whereas it improved to 2.0% for the inexperienced group. After case 15, there was no statistically significant difference between groups (P = .547). It is widely accepted that any new procedure that requires new hand-eye coordination, instrumentation, and cognitive and technical skills is associated with a learning curve. This study found that when placing a new type of implant, inexperienced practitioners had a definite learning curve and a significantly higher rate of failure than that of experienced surgeons. There was no comparable early clustering of failures seen in the experienced surgeon group (Fig 4). These data suggest that experience gained during an initial learning curve with an implant system may be transferable to other clinical situations and may result in fewer total failures and an essentially flat learning curve in a different setting. One must also keep in mind the need to allow for individual differences. It has been noted that the success of the technique depends on careful and scrupulous adherence to the prescribed clinical protocol by the combined surgical prosthodontic team. Failure of dental implants to os-

DENT ET AL

Table 4. Success and Failure of Dental Implants During the Healing Period (Stage I Outcome), Pooled Totals of Groups A and B, by Preoperative Antibiotic Dosage Level Implants Failed

Preoperative Antibiotic Dosage Comparison I-Antibiotic Versus No Antibiotic No antibiotic All dosage levels Total Comparison II-Peterson's Criterion Insufficient Sufficient Total Comparison ID-AHA Criterion Insufficient Sufficient Total

Survived

(n)

(%)

(n)

(%)

Total

17 2 19

(1.4) (0.1) (0.7)

1,176 1,446 2,622

(98.6) (99.9) (99.3)

1,193 1,448 2,641

.001

17 2 19

(1.1)

(0.2) (0.7)

1,557 1,065 2,622

(98.9) (99.8) (99.3)

1,574 1,067 2,641

.008

17 2 19

(1.0) (0.2) (0.7)

1,763 812 2,575

(99.0) (99.8) (99.3)

1,780 814 2,594

.049

criterion showed the greatest significant difference. Stage II survival was significantly improved if an ade quate level of antibiotic (as defined by Peterson2 or AHA 1 ) was given preoperatively, although lower doses of antibiotics still appear to enhance success at stage II surgery. Implant survival rates among the participating insti tutions varied widely (data not shown); however, a test for homogeneity showed that variations among institutions were within statistical norms, and therefore conclusions regarding antibiotic use could be drawn. The percentage of failures varied from none-for six of the institutions-to as high as 10.3%-for one cen ter. Five of the institutions had a failure rate higher than 6%. Fifteen of the institutions had failure rates under 2%. From these results, it appears that among those centers where an odds ratio can be computed (Table 2), there is overall approximately a 2: 1 risk of

failure if preoperative antibiotics are not used, and 2.5 to 3 times the risk of failure if levels recommended by Peterson2 or higher are not used. However, the 95% confidence interval is wide. A logistic regression analysis considering all of the factors that were significant on a univariate basis showed that the use of preoperative antibiotics is a significant contributor to implant survival.20 Postopera tive antibiotics do not appear to influence the results attributed to preoperative antibiotic usage. Implant fail ure rates were 2.7% with postoperative antibiotics and 2.9% without postoperative antibiotics. Discussion

The analysis of the 2,641 implants placed and un covered has shown that there is a higher implant failure rate in patients who did not receive preoperative antibi-

Table 5. Success and Failure of Dental Implants Found To Have Failed at Scheduled Uncovering (Stage II Outcome), Pooled Totals of Groups A and B, by Preoperative Antibiotic Dosage Level Implants Failed

Preoperative Antibiotic Dosage Comparison I-Antibiotic Versus No Antibiotic No antibiotic All dosage levels Total Compari on II-Peterson's Criterion Insufficient Sufficient Total Comparison III-AHA Criterion Insufficient Sufficient Total

Survived

(n)

(%)

(n)

(%)

Total

31 19

(2.6) (1.3) (1.9)

1,145 1,427 2,572

(97.4) (98.7) (98.1)

1,176 1,446 2,622

.014

39 11

(2.5) (1. 0) (1.9)

1,518 1,054 2,572

(97.5) (99.0) (98.1)

1,557 1,065 2,622

.007

41 9 50

(2.3)

1,722 803 2,525

(97.7) (98.9) (98.1)

1,763 812 2,575

.038

(1.1)

(1.9)

24 otics. An adequate level of antibiotics at the time of surgery significantly increases the survival rate of end osseous dental implants up to and including stage II surgery. If preoperative antibiotics were not used, the risk of implant failure increased approximately two to three times. Based on these data, there appears to be a trend of reduced implant failure when antibiotics are administered preoperatively in appropriate doses. Administration of any antibiotic carries with it in creased costs; the risk of side effects, including ana phylaxis; and the possibility for development of resis tant microbial strains. Therefore, the decision to use preoperative antibiotics should be made only after careful evaluation of benefits and risks. References 1. Dajani AS, Bisno AL, Chung KJ, et al: Prevention of bacterial endocarditis: Recommendations by the American Heart Asso ciation. JAMA 264:2919, 1990 2. Peterson LJ: Antibiotic prophylaxis against wound infections in oral and maxillofacial surgery. J Oral Maxillofac Surg 48:617, 1990 3. Page CP, Bohnen JMA, Fletcher JR, et al: Antimicrobial pro phylaxis for surgical wounds: Guidelines for clinical care. Arch Surg 128:79, 1993 4. Burke JF: The effective period of preventive antibiotic action in expe1imental incisions and dermal lesions. Surgery 50:161, 1961 5. Stone HH, Haney BB, Kolg LD, et al: Prophylactic and preven tative antibiotic therapy: Timing, duration and economics. Ann Surg 189:691, 1979 6. Jasper MT, Little JW: Infective endocarditis: A review and up date. Oral Surg Oral Med Oral Pathol 57:606, 1984 7. Altemeier WA, Burke JF, Pruitt BA, Jr, et al (eds): Manual on Control of Infection in Surgical Patients (ed 2). Philadelphia, PA, Lippincott, 1984 pp 26-29

INFLUENCE OF ANTIBIOTICS O.'.\ IMPLANTS 8. Sabiston DC (ed): Textbook of Surgery (ed 14). Philadelphia, PA, Saunders, 1991 p 222 9. Olson M, O'Connor M, Schwartz ML: Surgical wound infec tion: A 5-year prospective study of 10,193 wounds at the Minneapolis VA Medical Center. Ann Surg 199:253, 1984 10. Kaiser AB: Antimicrobial prophylaxis in surgery. N Engl J Med 315:1129, 1986 11. Gorman LM, Lambert PM, Mon-is HF, et al: The effect of smoking on implant survival at second-stage surgery: DICRG interim report no. 5. Implant Dent 3:165, 1994 12. Lambert P, Moms HF, Ochi S, et al: Relationship between implant surgical experience and second-stage failures: DICRG interim rep01t no. 2. Implant Dent 3:97, 1994 13. Truhlar RS, Moms HF, Ochi S, et al: Second-stage failures related to bone quality in patients receiving endosseous dental implants: DICRG interim report no. 7. Implant Dent 3:252, 1994 14. Lambert PM, Moms HF, Ochi S, et al: Positive effect of surgical experience with implants on second-stage implant survival. J Oral Maxillofac Surg 55:12, 1997 (suppl 5) 15. Lambert PM, Manis HF, Ochi S, et al: Influence of 0.12% chlorhexidine digluconate rinses on the incidence of infec tious complications and implant success following placement. J Oral Maxillofac Surg 55:25, 1997 (suppl 5) 16. Casino AJ, Harrison P, Tamow DP, et al: Influence of type of incision on the success rate of implant integration at stage II uncovering surgery. J Oral Maxillofac Surg 55:31, 1997 (suppl 5) 17. Truhlar RS, Farish SE, Schei tier LE, et al: Bone quality and implant design related outcomes through stage II surgical uncovering of Spectra-System root form implants. J Oral Maxillofac Surg 55:46, 1997 (suppl 5) 18. Olson JW, Dent CD, Dominici JT, et al: The influence of maxil lary sinus augmentation on the success of dental implants through second-stage surgery. Implant Dent 6:225,1997 19. Mon-is HF, Ochi S, Dental Implant Clinical Research Group (Planning Committee): The influence of implant design, ap plication, and site on clinical perfotmance and crestal bone: A multicenter, multidisciplinary clinical study. Implant Dent 1:49, 1992 20. Moms HF, Ochi S, Stoffer W, et al: Clinical treatment variables that significantly influence stage I-II implant survival. J Dent Res 75:181, 1996 (abstr 1305)

LAMBERT ET AL

Table 1.

DICRG Postoperative and Home Care Protocol for Toothbrushing and Antimicrobial Rinses Group A

Stage I-II ill-IV

B 2

Chlorhexidine rinses x 2 wk postoperatively Electric toothbrush but no chlorhexidine rinses

Chlorhexidine rinses x 2 wk postoperatively Electric toothbrush and chlorhexidine rinses

Chlorhexidine rinses X 2 wk postoperatively Manual toothbrush but no chlorhexidine rinses

ChJorhexidine rinses x 2 wk postoperatively Manual toothbrush and chlorhexidine rinses

OTE. Stage I starts with the placement surgery and continues until the time of surgical uncovering; stage II is the point of surgical uncovering; stage ill is the time between surgical uncovering and occlusal loading; and stage IV starts with occlusal loading.

alloy screw, HA-coated screw); HA-coated endosseous implant with a cylindrical body and internal hex-thread connection (HA-coated cylinder); titanium alloy en dosseous implant with a basket design, externally threaded body, and internal hex-thread connection (Ti alloy basket). All are available in two diameters except the screw, which is available in one diameter, and in four lengths, ranging from 7 or 8 mm to 16 mm. These implant designs constitute the Spectra-System (Core Vent Corporation, Las Vegas, NV). The type of im plant used for a given location was determined by a randomized assignment of implant design as described in the study design; however, length and diameter were chosen by the treatment team. 19 Chlorhexidine digluco nate 0.12% (Peridex, Proctor & Gamble, Cincinnati, OH) was provided to the clinical investigators for use by their study patients. Clinical investigators in each study group were ori ented to the clinical protocols, evaluation criteria, and data collection procedures. Although the study proto col recommended the use of chlorhexidine rinses im mediately before implant placement surgery and un covering surgery, and twice daily for 2 weeks after surgery, clinical investigators were free, according to their own practice pattern, to prescribe it or not to prescribe it. Clinicians choosing to prescribe chlorhexi dine and those who chose not to prescribe it were divided so that the number of implants in each group was similar and sufficient for analysis. Standardized forms were used to collect data. The prescribing of chlorhexidine was documented for each study case on the Implant Placement form (form 03) and on the Im plant Uncovering form (form 04). Once prescribed by the surgeon, patient compliance was monitored by re quests for another bottle of chlorhexidine. Mandibular implants were to be surgically uncov ered at least 4 months after placement and maxillary implants at least 6 months after placement. At the time of uncovering, the following were documented: the status of the implant (osseointegrated, integrated/non functional, not osseointegrated); the distance between top of implant and crest of bone; Periotest value of the

implant (Periotest, Siemens AG, Bensheim, Germany); type of incision (crestal, remote, tissue-punched); and medications prescribed. Complications and their treatments were docu mented during all phases of treatment. For this analy sis, several fields on the Complication form were combined to form the category ''infectious complica tions." These fields were "peri-implant infection," "peri-implantitis," "infection of soft tissue extra orally," "systemic infection secondary to implant," ''persistent febrile condition,'' ''osteomyelitis acute," and "osteomyelitis-chronic." All reports of infectious complications were based on clinical obser vations and not on rnicrobiologic testing, with the ex ception of one report that did include the results of such testing. No cases of systemic infection, persistent febrile condition, or chronic osteomyelitis were re ported. Data entry was done by staff of the data management center, and analysis of data was done by the DICRG study biostatistician. For the analyses presented, ''treatment'' means use of perioperative chlorhexidine rinses, and "control" means perioperative chlorhexi dine was not used. This clustering has no relation with the home care groups (row 2 of Table 1) to which clinical centers were randomized at entry into the study and which were implemented after uncovering of the implants. Results

The results for the treatment and control groups were analyzed on an implant basis and a patient basis both by study group (A and B) and by pooled data. The varying number of implants in the different study strata, and the fact that one patient could have several study cases (prostheses), placed the results in many different combinations for analysis. Although implants could be considered independent experimental units until uncovered, there is always a debate about whether the experimental unit is the implant or the patient; therefore, the results for both units are presented in

CHLORHEXIDINE EFFECT Q_ - �IPL-\,'\1 SUCCESS

Table 2. Infectious Complications of Implants With and Without Chlorhexidine Use (A & B Pooled)

Treatment Control Total

Infection (%)

No Infection

Total

57 (4.1) 109 (8.7) 166

1,330 1,145 2,475

1,387 1,254 2,641

of 1,387 implants (4.1%) in which chlorhexidine was used and 109 of 1,254 implan { . %) in which chlor hexidine was not used. These resul indicate a highly significant reduction in the number of infectious com plications in patients who received hlorhexidine dur ing the immediate postoperative period after stage I surgery (P = .001 using the chi-square teSt).

Patients this article. The first comparison focuses on the use of chlorhexidine by each experimental unit and the rate of infectious complications recorded. The second com parison is the influence of the presence of an infectious complication on the failure of implants to integrate. CHLORHEXIDINE AND INFECTIOUS COMPLICATIONS

Implants Data collected on 2,847 implants placed and 2,641 uncovered in the DICRG database as of May 1995 form the basis for the statistics reported. Of the total 2,641 implants, study groups A and B placed and un covered 1,255 and 1,386 implants, respectively. Group A investigators prescribed chlorhexidine rinses slightly more frequently than did the investigators in group B. Of the implants placed by group A, 60.8% (763/1,255) were in the treatment group, and 39.2% (492/1,255) were in the control group. In group B, 45% of implants (624/1,386) were in patients using chlorhexidine rinses and 55% (762/1,386) were not. Investigator preference created a treatment group and control group of almost identical size when the data were pooled. A total of 2,641 implants were placed, and 52.5% ( l ,387/2,641) were analyzed as the treatment group and 47.5% ( l,254/2,641) as the control group. In group A, the rate of infectious complications was 2.8% (21/763) for the treatment (chlorhexidine) group versus 6.7% (33/492) in the control group. The control group experienced a rate of infectious complications more than twice that of the treatment group. This difference was statistically significant (P = .001, chi square test). In group B, the rates of infectious compli cations for the control and treatment groups were simi lar to those in group A. The control group experienced about twice the number of infectious complications that the treatment group did, 10% (76/762) versus 5.8% (36/624). This difference was statistically significant (P = .004, chi-square test). The relation between the use of chlorhexidine and the incidence of infectious complications (pooled data) is shown in Table 2. Chlorhexidine rinses were pre scribed perioperatively (implant placement surgery) for 1,387 implants and not prescribed for 1,254 im plants. An infectious complication was reported for 57

During the accrual period. group A enrered 290 pa tients and group B, 305. In group A I {61%) were provided chlorhexidine, and 113 ( 9'i) were not. In group B, 148 (48.5%) patients were ided chlorhex idine and 157 (51.5%) were noL In group A, an infectious compli on \\ recorded for the treatment group in .-% of me patients which was slightly more than half char of ihe <it: complica tions in the control group (P = _-, . chi-square test). The infectious complication rare ihe patients in group B was very similar to that of parien in group A. The treatment group reported comptic2ri for 7.4% compared with 10.2% for the corurol group. When the data for the two groups were pooled ffable 3), the patients in the treatment group ha! - . 4 infectious complication rate, compared with 9 in the control group (P = .397, chi-square Although infectious compli'-4..nh.::. quently when chlorhexidine rinses held true for preoperative anu-11·100ics.. tive antibiotics were used. the

INFECTIOUS COMPLICATIO.

�;-J" FAILURE

Implants When an infectious recorded, there was an increase in i1=1:il'.'!:hiliw� of implant failure. In study group A.. heo =-ei:rious complication was reported, 7 of I % ) failed to integrate, compared \\ith - L I (1.7%) when

Table 3. Patients Hh ln:l'ec&IUS Complications (Pooled] Infection Treatment Control Total

19 C.:: 25 9_: �

Total 325 270 595

30 bleeding sites, normal pocket temperature, no peri odontopathic microorganisms, and normal BG activity at baseline. All of these parameters are consistent with absence of disease, and it should not be surprising that differences could not be detected. The authors hypothesized that chlorhexidine irrigation may have had a preventive effect, because no other professional treatment was performed, and none of the indices worsened over the 8 weeks of the study. A major cause of tooth loss is periodontal disease, and it has been shown that the risk of development of further disease is highest in patients with a history of periodontal disease. Therefore, successful dental im plant treatment must include strategies to reduce this risk. Antimicrobial therapy with chlorhexidine has been shown to reduce periodontal disease and surgical complications. In this study we have shown that chlor hexidine rinses were beneficial in reducing infectious complications when routinely used in the perioperative period. In view of the potential for development of resistant strains of microorganisms as a result of using systemic antibiotics, it may be more prudent to protect against infectious complications with topical antimi crobial therapy. Reducing these complications could ultimately reduce the number of failures at stage II uncovering. A well-controlled prospective clinical trial is suggested to confirm these findings.

References 1. American Dental Association: Surgical Dental Implants: Data from the 1991 Special Version-Survey of Dental Practice and the 1990 Survey of Dental Services Rendered. Chicago, IL, The Association, 1993 2. Grbic JT, Lamster IB, Rommanita SC, et al: Risk indicators for future clinical attachment loss in adult periodontitis: Patient variables. J Periodontol 62:322, 1991 3. Ponitz DP, Gershkoff A, Wells H: Passage of orally adminis tered tetracycline into the gingival crevice around natural teeth and around protruding subperiosteal implant abutments in man. Dent Clin North Am 14:125, 1970 4. James RA: Peri-implant considerations. Dent Clin North Am 24:415, 1980 5. McKinney RV, Steflik DE, Koth DL: The epithelium dental implant interface. J Oral Implantol 13:622, 1988 6. Brownstein CN, Briggs SD, Schweitzer KL, et al: Irrigation with chlorhexidine to resolve naturally occurring gingivitis: ·A methodologic study. J Clin Periodontol 17:588, 1990 7. Beiswanger DD, Mallat ME, Jackson RD, et al: Clinical effects of a 0.12% chlorhexidine rinse as an adjunct to scaling and root planing. J Clin Dent 3:33, 1992 8. Cumming B, Loe H: Optimal dosage and method of delivering chlorhexidine solutions for the inhibition of dental plaque. J Periodont Res 8:57, 1973 9. Aziz-Gandour IA, Newman HN: The effects of a simplified oral hygiene regimen plus supragingival irrigation with chlorhexi-

CHLORHEXJDINE EFFECT ON IMPLANT SUCCESS

10.

11. 12. 13. 14.

15. 16. 17.

18.

19.

20. 21.

22. 23. 24. 25.

26. 27. 28.

dine or metronidazole on chronic inflammatory periodontal disease. J Clin Periodontol 13:228, 1986 Hammerle CHF, Fourmousis I, Winkler JR, et al: Successful bone fill in late peri-implant defects using guided tissue re generation: A short communication. J Periodontol 66:303, 1995 Larsen PE: The effect of a chlorhexidine rinse on the incidence of alveolar osteitis following the surgical removal of impacted mandibular third molars. J Oral Maxillofac Surg 49:932, 1991 Ragano JR, Szkutnik AJ: Evaluation of 0.12% chlorhexidine rinse on the prevention of alveolar osteitis. Oral Surg Oral Med Oral Pathol 72:524, 1991 Bonine FL: Effect of chlorhexidine rinse on the incidence of dry socket in impacted mandibular third molar extraction sites. Oral Surg Oral Med Oral Pathol 79:154, 1995 Fotos PG, Koorbusch GF, Sarasin DS, et al: Evaluation of intra alveolar chlorhexidine dressings after removal of impacted mandibular third molars. Oral Surg Oral Med Oral Pathol 73:383, 1992 Lang NP, Schild U, Bragger U: Effect of chlorhexidine (0.12%) rinses on periodontal tissue healing after tooth extraction. I. Clinical parameters. J Clin Periodontol 21:415, 1994 Lang NP, Schild U, Bragger U: Effect of chlorhexidine (0.12%) rinses on periodontal tissue healing after tooth extraction. II. Radiographic parameters. J Clin Periodontol 21:422, 1994 Ferretti GA, Ash RC, Brown AT, et al: Chlorhexidine for pro phylaxis against oral infections and associated complication in patients receiving bone marrow transplants. J Am Dent Assoc 114:461, 1987 Thomson-Neal D, Evans GH, Meffert RM: Effects of various prophylactic treatments on titanium, sapphire and hydroxyap atite-coated implants: An SEM study. lnt J Periodontics Re storative Dent 9:300, 1989 Morris HF, Ochi S, Dental Implant Clinical Research Group (Planning Committee): The influence of implant design, ap plication, and site on clinical performance and crestal bone: A multicenter, multidisciplinary clinical tudy. Implant Dent 1 :49, 1992 Lambert P, Morris HF, Ochi S, et al: Relationship between implant surgical experience and second-stage failures: DICRG interim report no. 2. Implant Dent 3:97. 1994 Ochi S, Morris HF, Winkler S, et al: Patiem demographics and implant survival at uncovering: Dental Implant Clinical Research Group interim report no. 6. Implam Dent 3:247, 1994 Mombelli A, van Oosten MAC, Schtirch E, et al: The microbiota associated with successful or failing osseointegrated titanium implants. Oral Microbiol Immunol 2:145, 19 7 Ong ES-M, Newman HN, Wilson M, et al: The occurrence of periodontitis-related microorganisms in relation ro titanium implants. J Periodontol 63:200, 1992 Loesche WJ, Syed SA, Schmidt I, et al: Bac1erial profiles of subgingival plaques in periodontitis. J Periodontol 56:447, 1985 Apse P, Ellen RP, Overall CM, et al: Microbiota and crevicular fluid collagenase activity in the osseointegrated dental im plant sulcus: A comparison of sites in edentulous and partially edentulous patients. J Periodont Res 24:96, 1989 George K, Zafiropoulos G-G, Murat Y, et al: Clinical and micro biological status of osseointegrated implants. J Periodontol 5:766, 1994 Ciancio SG, Bourgault PC: Clinical Pharmacology for Dental Professionals (ed 3). Chicago, IL, Year Book Medical Pub lishers, 1989, p 231 Lavigne SE, Krust-Bray KS, Williams KB, et al: Effects of subgingival irrigation with chlorhexidine on the periodontal status of patients with HA-coated integral dental implants. Int J Oral Maxillofac Implants 9: 156, 1994

J Oral Maxillofac Surg 55:31-37, 1997, Suppl 5

The Influence of Type of Incision on the Success Rate of Implant Integration at Stage II Uncovering Surgery ANTHONY J. CASINO, DDS,* PATRICK HARRISON,t DENNIS P. TARNOW, DDS, MS,+ HAROLD F. MORRIS, DDS, MS,§ AND SHIGERU OCHI, PHD 11 In 1991, the Dental Implant Clinical Research Group comprising 30 Depart ment of Veterans Affairs medical centers and two dental schools initiated a long-term clinical study to investigate the clinical performance of implants within the Spectra-System (Core-Vent Corporation, Las Vegas, NV). This article focuses on a portion of the study database related to incision type, implant success rates, and response of crestal bone up to the time of surgical uncov ering. The crestal incision was used for 1,705 implants (381 patients) and the remote incision for 593 implants (141 patients). No statistically significant difference (P = .092 chi-square statistic) was found in implant integration or the response of crestal bone.

Dental rehabilitation with osseointegrated root-form implants is highly successful, although failures do oc cur at all stages of treatment. Many subtle, but very important, variables associated with the placement of endosseous implants continue to be debated because of the lack of data gathered in scientific prospective clinical studies. One in particular is the method of surgical incision used to expose the site of implanta tion. Most oral surgery textbooks list the basic require ments of incision and flap design. 1 These include main taining a good blood supply, maintaining the base of

the flap wider than the apex, maintaining the length no more than twice the base, and closing the suture line over bone. In implant dentistry, the mucobuccal and crestal incisions are two of the most commonly used. Both appear to be based largely on personal pref erence, experience, and logic, because little scientific data currently exist to support superiority of one design over the other. In perfecting a reliable surgical protocol for implant placement, Branemark, the pioneer of root-form endos seous implants, used a surgical technique incorporating a mucobuccal incision. This incision (Fig 1) is de scribed by Branemark as "a buccal, horizontal incision at about half the height of the alveolar process, with preparation of lingually or palatally pedicled mucoper iosteal flap. " 2 Branemark et al3 suggested that this method keeps the mucobuccal incision epithelial mar gins away from the implant surgical site. It was pro posed that it also maintains complete coverage of the implants after closure so that the suture line will not represent a threat to the healing implant' s autonomy from the oral cavity. 3 Acceptance of this incision design is widespread, and the proponents include respected implantologists such as Lekholm and Jemt.4 Proponents also can be found worldwide at such dental schools as the Nippon Dental University. 5 The Nippon manual describes the surgical incision design as being marked in the buccal sulcus parallel to the alveolar crest. In addressing ''pre-

* Chief, section of Oral and Maxillofacial Surgery, Dental Service, Department of Veterans Affairs Medical Center, Northport, NY; chief, Division of Oral and Maxillofacial Surgery, University Medical Center at Stonybrook; Clinical Associate Professor of Oral and Maxillofacial surgery, School of Dental Medicine, SUNY at Stonybrook. t Student, University of Michigan Dental School, Ann Arbor, MI. Clinical Professor and Chairman, Department of Implant Den tistry, College of Dentistry, New York University, New York, NY. § Codirector, Dental Clinical Research Center; Project Codirector, Dental Implant Clinical Research Group, Department of Veterans Affairs Medical Center, Ann Arbor, Ml. 11 Codirector, Dental Clinical Research Center; Project Codirector, Dental Implant Clinical Research Group, Department of Veterans Affairs Medical Center, Ann Arbor, MI. Address correspondence and reprint requests to Dr Morris: De partment of Veterans Affairs Medical Center, Dental Research (154), 2215 Fuller Rd, Ann Arbor, MI 48105.

This is a US government work. There are no restrictions on its use. 0278-2391/97/5512-5005$0.00/0

CASINO ET AL

ental history (Form 01) and dental evaluation (Form 02) were completed. The inclusion criteria generally required that the patient benefit from the implant treat ment, whereas the exclusion criteria focused on ensur ing that the patient would not be ''put at risk'' and chat the patient-related conditions wou.Jd not influence data outcomes. 12 After careful medical and dental reening, cases were reviewed to determine if they - tisfied the requirements for entry into one of the five earch strata: 1) upper completely edentulous (UCE); -) upper partially edentulous (UP); 3) lower comletely edentulous (LCE); 4) lower partially edentulous 'LP); and 5) anterior single tooth (UST). Each stratum ·as subject to the same rigid experimental design re quirements. The implants used were from the Spectra-System Core-Vent Corporation, Las Vegas, NV); they in luded the Core-Vent basket, the Screw-Vent, the Bio ent bullet, and the Micro-Vent grooved implant igns. These implants were composed of either commercially pure titanium (Ti-CP), titanium alloy i-6Al-4V), or hydroxyapatite-coated titanium alloy. Different implant designs and materials were used in each of the research strata. Randomization of the im plants assigned to each stratum was used to determine the location of each design relative to the other im plants to be included in each case. Eighty-five clinical investigators were trained in the use of standardized clinical evaluation methodologies, the application of specific evaluation criteria, and data collection procedures. Of these investigators, 32 were urgeons with different skill levels, experience, and training. Each of the surgeons, one from each center, had been provided training in the preferred surgical procedures and instrumentation associated with the Spectra-System of implants. 13 Although the Dental Im plant Clinical Research Group (DICRG) protocol rec ommended the mucobuccal incision for each patient or case, the surgeon was allowed to deviate from the protocol based on preferences developed from many ears of experience with various existing anatomic characteristics that may be encountered in the treat ment of patients. Standardized forms were used to collect data. Data collected at implant insertion included implant type, diameter, and length; site (tooth number and jaw); res toration planned; type of incision (crestal or remote); whether a bone tap was used in site preparation; medi cations prescribed; snugness of fit (firm or loose); bone quality (1, 2, 3, or 4); and crestal bone measurements in relation to the top of the implant on the mesial, facial, and distal aspects. The distance was measured to the nearest millimeter with a plastic probe. Muco buccal incisions and lingualized or palatal incisions were documented as ''remote.'' It was recommended that 3 to 4 mm bone separate one implant from another

rim to rim. Crestal bone (pinnacles of bone less than 1 mm in width) was reduced in the mandibular anterior area, if necessary, so that a minimum of 1 mm of bone was present on the buccal and lingual surfaces. Buccal and lingual bone widths were measured only after crestal bone reduction. Date of suture removal was not entered. At the time of uncovering, the status of the implant was assessed ( osseointegrated, integrated/nonfunc tional, not osseointegrated). It was suggested that clini cians test for osseointegration by tapping the implant firmly with the handle of a dental instrument, which will result in a ringing sound (osseointegrated) or a dull sound (not osseointegrated). In addition, when placing the healing caps, clinicians were to try to rotate the implant and lift it out of the bone. Complications and their treatments were documented during all phases of treatment. Implants that were removed were documented on a Complication form and a Failure form. ''Failure'' was defined as the lack of osseointegration as evidenced by mobility or complete peri-implant radiolucency. Chronic pain or infection were also reasons for implant removal. Information recorded for failed implants in cluded implant type, diameter, length, location, mobil ity, ease of removal, and mechanical integrity; reasons for removal (pain, infection, mobility, peri-implant ra diolucency, etc); treatment stage at removal; and dispo sition of the site. If a failure was attributable to peri implant infection, cultures and radiographs were used to determine the local extent of the infection. Treat ment stages were defined as stage I (after surgical placement but before uncovering); stage II (at uncov ering); stage III (after uncovering but before occlusal loading); and stage IV (after occlusal loading). Data entry was done by staff of the data management center, and analysis of data was done by the DICRG staff biostatistician. The analyses were done as a whole for the two groups and also by study group (group A has 17 clinical centers; group B, 15 clinical centers). Both groups used the same randomization plan and study strata. The differences between the groups were the amount of prior surgical experience with im plants, 14 type of alloy for restorations (each assigned four alloys), and home care regimen (manual or electric toothbrush with or without antimicrobial rinses).

Results IMPLANTS PLACED AND INCISIONS USED

DICRG data collected on 2,847 implants placed and 2,641 uncovered as of May 1995, less 343 implants missing incision data, form the basis for this analysis (2,298 implants). Data regarding type of incision used at implant insertion were not available for 343 implants

INFLUENCE OF INCISION TYPE ON IMPLANT SUCCESS

Table 1. Patients and Implants by Incision Type at Implant Placement and Research Stratum (Study Group A) Cresta! Incisions

Remote Incisions

Implants (n = 826)

Total Incisions

Implants (n = 315)

Implants (n = 1141)

Stratum

Patients

Failed

Survived

Palients

Failed

Survived

Patients

LCE LP UCE UP UST Total

43 59 26 30 36 194

9 5 5

242 228 154 120 62 806

12 16 14 6 23 71

1 3

107 71 72 30 30 310

55 75 40 36 59 265

Failed

Survived

10 8 6

349 299 226 150 92 1116

NOTE. LCE, lower completely edentulous; LP, lower posterior partially edentulous; UCE, upper completely edentulous; UP, upper posterior partially edentulous; UST, upper single tooth.

because "type of incision used" was not pait of the original form. Of the 2,298 implants, 593 were placed with a remote (mucobuccal or lingualized/palatal) inci sion, whereas 1705 were placed with a crestal incision. The crestal incision was preferred by the DICRG investigators from both study groups. Data by study group were further broken down by research stratum (Tables 1 and 2) because the research strata involved placement of implants in different jaw regions, each with its own problems as far as ease of access, which may contribute to the distribution of type of incision used and the number of implant failures. The data from study groups A and B were similai· enough that they were pooled for additional comparisons (Table 3). Overall, the crestal incision was used three times as often as the remote incision, and in each stratum the crestal incision was preferred (Table 4). In the mandi ble, for completely edentulous cases, the crestal inci sion was used 2.6 times as often as the remote incision (489/185), and for the posterior partially edentulous cases, 3.4 times as often (442/131). In the maxilla, for the completely edentulous cases, the crestal incision was used 3.6 times as often (399/112); for the posterior

partially edentulous cases, 2.2 times as often (243/ 111); and for the anterior single tooth cases, 2.4 times as often (132/54). OUTCOME AT STAGE II

The failure rates of implants placed with a crestal incision and those with a remote incision were 2.3% and 2.4%, respectively (Table 5, pooled data). There was no significant difference in failure between the remote and crestal incision designs (P < .92, chi square test) when the data were pooled. For the LCE, the failure rates were 2.5% for the crestal incision (12 of 489) and 1.6% for the remote (3 of 185) (P < .52). The LP stratum experienced a failure rate of 2.7% (12 of 442) in the crestal incision group versus 3 .1% (4 of 131) in the remote incision group (P < .84). In the UCE stratum, the implants in the crestal incision group failed 2.5% (10 of 399) of the time versus 6.3% (7 of 112) for the remote incision group (P < .07). Implant failures in the UP stratum were not statistically significant (P < .57), with 0.8% (2 of 243) in the crestal incision group and no failures

Table 2. Patients and Implants by Incision Type at Implant Placement and Research Stratum (Study Group B) Total loci ions

Remote Incisions

Cresta! Incisions

Implants (n = 1157)

Implants (n = 278)

Implants (n = 879) Stratum

Patients

Failed

Survived

Patients

Failed

Survived

Patients

LCE LP UCE UP UST Total

30 46 37 35 39 187

3 7 5 1 3 19

235 202 235 121 67 860

12 14 8 23 13 70

2 1 6

75 56 33 81 24 269

fuilcd

5 II I

Survived

310 258 268 202 91 1,129

NOTE. LCE, lower completely edentulous; LP, lower posterior partially edentulous; UCE, upper comple1ely edenmlous: UP. upper posterior partially edentulous; UST, upper single tooth.

CASINO ET AL

Table 3. Patients and Implants by Incision Type at Implant Placement and Research Stratum (Pooled Data, Study Groups A and B} Cresta! Incisions

Remote Incisions

Implants (n = 1705)

Total Incisions

Implants (n = 593)

Implants (n = 2298)

Stratum

Patients

Failed

Survived

Patients

Failed

Survived

Patients

Failed

Survived

LCE LP LlCE CF (.;ST Total

73 105 63 65 75 381

12 12 10 2 3 39

477 430 389 241 129 1,666

24 30 22 29 36 141

3 4 7

182 127 105 111 54 579

97 135 85 94 111 522

15 16 17 2 3 53

659 557 494 352 183 2,245

. OTE. LCE, lower completely edentulous; LP, lower posterior partially edentulous; UCE, upper completely edentulous; UP, upper posterior p:mially edentulous; UST, upper single tooth.

in the remote group. The UST stratum experienced a failure rate of 2.3% (3 of 132) in the crestal group and no failures in the remote group (P < .56). The recommended postoperative healing periods be een placement and second-stage surgery uncovering as 4 months for mandibular implants and 6 months for maxillary implants. This period allowed for ade quate bone healing around the implant. To reduce the oncern or possibility that an implant was uncovered early, thereby contributing to its failure, we are re porting the mean duration of healing time allowed for each research stratum. For mandibular implants in DICRG study group A, the mean elapsed time between implant placement and uncovering was 162 days (edentulous cases) and 194 days (posterior partially edentulous cases); in study group B, it was 179 days (edentulous cases) and 184 days (posterior partially edentulous cases). For maxillary implants in study group A, the mean time to uncovering was 226 days (edentulous cases and posterior partially edentulous cases) and 251 days (anterior single tooth cases); in tudy group B, it was 202 days (edentulous cases),

Table 4. Distribution of Implants by Incision Type Used at Implant Placement and Research Stratum (Pooled Data of Study Groups A and B} Stratum

Cresta! Incision

Remote Incision

Relative Abundance, C:R

LCE LP UCE UP UST Total

489 442 399 243 132 1,705

185 131 112 111 54 593

2.6 3.4 3.6 2.2 2.4 2.9

OTE. LCE, lower completely edentulous; LP, lower posterior partially edentulous; UCE, upper completely edentulous; UP, upper posterior paitially edentulous; UST, upper single tooth. Data are missing on incision type used at surgical placement for 343 implants.

213 days (anterior single tooth cases), and 233 days (posterior partially edentulous cases). With pooled data by study stratum, the mean time to uncovering was 173 days (5.7 months) for LCE (mandibular completely edentulous stratum); 187 days (6.1 months) for LP (mandibular posterior partially edentulous stratum); 212 days (7.0 months) for UCE (maxillary completely edentulous stratum); 230 days (7.6 months) for UP (maxillary posterior partially edentulous stratum); and 232 days (7.6 months) for UST (maxillary anterior single tooth stratum). The bone loss around all implants in the study be tween stage I and stage II surgeries was compared with the type of incision used at the time surgical placement. Findings showed no statistically significant differences based on data recorded for the facial and distal aspects of the implant, and only a very slight difference on the mesial aspect (Table 6). Discussion

The data indicate that the crestal incision was pre ferred by the DICRG surgeons about three times as

Table 5. Implant Outcome at Stage II, by Study Group and Incision Type at Implant Placement Implant Outcome Study Group

Succeed(%)

Fail(%)

Crestal Remote

97.6 98.4

2.4 1.6

Cresta! Remote Pooled Crestal Remote

97.8 96.8

2.2 3.2

97.7 97.6

2.3 2.4

A B

INFLUENCE OF INCISIO

Table 6. Bone Loss Between Implant Placement and Surgical Uncovering by Study Group and Incision Type Bone Loss (mean mm :!:: SD) Study Group A

Mesia!

Facial

Implants

Distal

Cresta! Remote Other Total

-0.93 -1.04 -2.83 -0.99

:!:: :!:: :!:: :!::

1.62 1.62 2.69 1.69

-1.08 -1.12 -3.75 -1.16

:!:: :!:: :!:: :!::

1.80 1.98 2.95 1.91

-0.84 -0.94 -2.43 -0.89

:!:: :!:: :!:: :!::

1.52 1.75 2.69 1.60

1,152 53 38 1,243

Cresta! Remote Other Total Pooled data Cresta! Remote Other Total

-1.05 -1.06 -0.86 -1.04

:!:: :!:: :!:: :!::

1.72 2.69 1.69 1.73

-1.25 -1.44 -1.22 -1.25

:!:: :!:: :!:: :!::

1.94 3.50 1.89 1.95

-0.96 -0.67 -0.93 -0.96

:!:: :!:: :!:: :!::

1.62 2.54 1.72 1.63

1,298 9 55 1,362

-0.99 -1.04 -1.67 -1.02

:!:: :!:: :!:: :!::

1.68 l.78 2.35 1.71

-1.17 -1.17 -2.25 -1.21

:!:: :!:: :!:: :!::

1.88 2.23 2.68 1.93

-0.90 -0.90 -1.54 -0.92

:!:: :!:: :!:: :!::

1.57 1.86 2.28 1.62

2,450 62 93 2,605

mucobuccal incision as the inci ion of choice, and ini tially the surgical data collection form did not record this information. Between the two study groups, there were 32 dental surgeons ith rnrying le,-els of training and implant experience. en me im-e tigators indi cated a preference for the cresta.l inci -on_ the surgical data collection form wa modified to allm recording of the incision design used. Before re,; ion of the form, 343 implants were placed_ and the inc- ion data were not recorded. In spite of this o ---ion.. cbe large num ber of implants placed and parie - rreated overcame the limitations of the Scharf/Tamo" ::rudy. Also, pa tient screening requiremen were DO{ tringent as those reported by Scharf and T mow in chat patients were not entered in the DICRG � uni their den-

NOTE. There were 2,605 readings with both the placement and uncovering data recorded. "Other" category is a mixture, with some indicating that both types of incision were used in the surgery and some omitting the incision type. A plastic probe was used to measure bone heights to the nearest millimeter at placement and at surgical uncovering.

often as the remote incision. This can be attributed to its simplicity; the crestal incision is made in keratinized tissue, full-thickness flaps are reflected to expose the underlying bone, and suturing is easily accomplished. As Scharf and Tarnow9 noted, there are numerous ad vantages to using the crestal incision technique. The patient suffers less discomfort from excessive edema and, from the clinicians' viewpoint, crestal incisions are quicker to make and easier to work with, blood supply to the reflected flap is not as compromised, and the patient's existing prosthesis flange is less likely to iITitate the incision line. The prospective nature of this study, with its well controlled clinical research procedures, facilitated sci entific comparison of the implant success rates ob tained when mucobuccal incision and crestal incision designs were used. The findings show that the ability of an endosseous implant to osseointegrate was not affected by placement of the incision line. Further more, there was no difference in crestal bone response to the implants used in this study when the mucobuccal (remote) or crestal incisions were used for implant placement. The percentage of implants that failed in either study group or with either incision type was not excessive. By study group, implant failure rates for DICRG group A and group B from implant placement through surgical uncovering were 2.0% and 2.8%, re spectively; with pooled data, the failure rate was 2.4%. 15 By incision type, the implant failure rates re lated to crestal and remote incisions at implant place ment were 2.3% and 2.4%, respectively. The DICRG research protocol recommended the

TYPE Q_ - [\[PLANT SUCCESS

be attained with eicber based surgical techniq � References

6. 7. 8.

incisions on

J Oral i\ia; - "

I 0. Patrick DR: The G

1)10 ET AL

Implant Prosthodontics: Surgical and Prosthetic Techniques for Dental Implants. Chicago, IL, Year Book Medical, 1990, pp 123-136 11. Misch CE (ed): Contemporary Implant Dentistry. St Louis, MO, Mosby, 1993, pp 1-779 L Morris HF, Ochi S, Dental Implant Clinical Research Group (PlanÂ ning Committee): The influence of implant design, application, and site on clinical performance and crestal bone: A multicenter, multidisciplinary clinical study. Implant Dent 1:49, 1992

37 13. Implant Division of Dentsply International: Spectra-System SurÂ gical Manual. Encino, CA, Dentsply, 1993 14. Lambert P, Morris HF, Ochi S, et al: Relationship between implant surgical experience and second-stage failures: DICRG interim report no. 2. Implant Dent 3:97, 1994 15. Truhlar RS, Farish SE, Scheitler LE, et al: Bone quality and implant design related outcomes through stage II surgical uncovering of Spectra-System root form implants. J Oral Maxillofac Surg 55:46, 1997 (suppl 5)

J Oral Maxillofac Surg 55:38-45, 1997, Suppl 5

Distribution of Bone Quality in Patients Receiving Endosseous Dental Implants RICHARD S. TRUHLAR, DDS,* IRA H. ORENSTEI HAROLD F. MORRIS, DDS, MS,+ AND SHIGERU OCH. Knowledge of the distribution of bone quality in the various assists the clinician in dental implant treatment planning. Bone assessed with radiographs and tactile sensation for 2,839 irr. time of placement into four anatomic regions of the jaw. Th10 classification system was used. Overall, bone quality types 1 and - � much less frequently than types 2 and 3. Although variations in a-s;: in each region, quality 2 bone dominated the mandible, and was more prevalent in the maxilla. For both anterior and post� ::. types 2 and 3 bone predominated. The anterior mandible had followed by the posterior mandible, anterior maxilla, an pos:e -

The long-term clinical success of dental implants is highly influenced by both the quality and quantity of available bone. t-s Reports indicate a higher survival rate of dental implants in lower jaws, which has been ascribed to better bone quality and quantity in the ante rior mandible. 6• • Dense bone increases the percentage of bone-implant contact and provides greater initial stability to the implant during the healing period after surgery. Furthermore, such bone structure permits bet ter distribution of the stresses that occur at the implant bone interface during function. Stimulation of bone within physiologic limits may produce an increase in osseous density at the implant-bone interface. 10-15 Physiologic stimulation of less dense bone, with its numerous marrow spaces, does not result in the same 7 9

* Clinical Investigator, Dental Implant Clinical Research Group; Staff Periodontist, Department of Veterans Affairs Medical Center, Northport, NY; Clinical Assistant Professor, Department of Periodontics, School of Dental Medicine, State University of New York, Stony Brook. t Clinical Investigator, Dental Implant Clinical Research Group; Staff Dentist, Department of Veterans Affairs Medical Center, Bronx, NY; Assistant Clinical Professor, Columbia University School of Dental and Oral Surgery. :j: Codirector, Dental Clinical Research Center; Project Codirector, Dental Implant Clinical Research Group, Department of Veterans Affairs Medical Center, Dental Research, Ann Arbor, MI. § Codirector, Dental Clinical Research Center; Project Codirector, Dental Implant Clinical Research Group, Department of Veterans Affairs Medical Center, Dental Research, Ann Arbor, MI. Address correspondence and reprint requests to Dr Morris: De partment of Veterans Affairs Medical Center, Dental Research (154), 2215 Fuller Rd, Ann Arbor, MI 48105. This is a use.

encoun of bone of the plannin= In 1991. (DICRG

government work. There are no restrictions on its

0278-2391/97/5512-5009$0.00/0

-T

-D§

�CHI.AR ET AL

· r, multidisciplinary long-term clinical study to inves tigate the influence of implant design, application, and ·te of placement on clinical success. 19 The study con ii ts of 30 Department of Veterans Affairs Medical Centers and several research universities. An interim ill.Idy report, published in 1994,20 reported on stage I data for 1935 implants. The aim of this report is to describe the final distribution of bone quality in the ,·arious regions of the jaws for all enrolled study cases, totaling 2,839 individual implants.

As part of the comprehensive studies by the DICRG, the quality of bone at each implant site was recorded at the time of placement surgery, and the prevalence of various bone qualities was later tabulated. The Lek holm-Zarb classification system21 was used to assess quality of bone. In their system (Fig 1), there are four different categories: quality 1 (Q-1) bone is composed largely of dense, homogenous cortical bone with a small core of trabecular bone; quality 2 (Q-2) bone exhibits a large, dense layer of cortical bone that sur rounds a dense trabecular core; quality 3 (Q-3) bone has a thinner layer of cortical bone around a dense trabecular core; and quality 4 (Q-4) bone has a thin cortical layer surrounding a low-density trabecular core. The surgeon evaluated the quality of bone using both radiographs and tactile sensations of cutting resis tance and force required during the preparation of the osteotomy site (Fig 2). Bone quality classification was recorded, along with type of implant, its approximate tooth location, and its length and diameter. Randomization determined the im plants assigned to each case in the five research strata (Table 1), designated as UCE, maxillary completely ede ntulous cases; UP, maxillary posterior partially edentu lous cases; UST, maxillary anterior single tooth cases; LCE, mandibular completely edentulous cases; and LP, mandibular posterior prutially edentulous cases.

Patients and Methods

Results

Selection of the 30 participating VAMC implant reearch centers followed careful screening of 55 inter ested medical centers using the following criteria: 1) the training credentials and experience of each member of the implant team were adequate to conduct the tudy; 2) the team must consist of no less than two trained investigators; 3) the investigator who placed the implants was not the one to complete the follow up evaluations; and 4) all study participants would undergo comprehensive training and standardization essions before placing, restoring, and maintaining im plants. Furthermore, investigators must continue to un dergo annual retraining and standardization testing. After selection of the medical centers, more than 85 clinical investigators were trained and standardized in 1) clinical protocols, 2) application of the project eval uation crite1ia, and 3) data collection procedures. As part of the project design, the 30 medical centers were randomized to one of two independent study groups to aid in later statistical analyses of the data. Two dental schools were subsequently added to one of the tudy groups. All potential patients were carefully screened before entry into the study. Both a comprehensive medical/ dental history and a dental/clinical evaluation were completed. Inclusion and exclusion criteria have been reported previously.19

A total of 2,910 implants have been placed and re corded in the DICRG database as of May 1995. Sixty three of these implants were replacements for those that failed. The remaining 2,847 implants placed at first surgery are used as the denominator in all compu tations of percentages in which characteristics at im plant placement are tabulated. The total number of implants tabulated was 2,839, after eight implants were dropped from the study analysis because of missing bone quality data. Percentage bone quality distributions for the mouth as a whole, and broken out by study groups A and B, are presented in Table 2. Q-2 and Q-3 bone were found at most implant sites, with Q-1 and Q-4 bone found infrequently. To promote simplicity, data for study groups A and B are combined for the remainder of this report.

R FlGU E 1. Bone quality as defined by Lekholm and Zarb.21 Q-1, e homogenous cortical bone with a small trabecular core; Q-2, � . dense layer of cortical bone surrounding dense trabecular core; 3. thinner layer of cortical bone around dense trabecular core; Q -. thin cortical layer stmounding low-density trabecular core.

BONE

QUALITY BY

ARCH AND POSITION

Table 2 summarizes the distribution of bone quality by arch and position of implant placement. Bone qual ity prevalence by jaw arch shows Q-2 bone predomi nated in the mandible (mean bone quality of 2.14, SD = 0.65) and Q-3 in the maxilla (mean bone quality of 2.83, SD = 0.65). In anterior and posterior jaw posi tions, Q-2 and Q-3 bone were most prevalent.

J Oral Maxillolac Surg 55:46-54, 1997, Suppl 5

Bone Quality and Implant Design-Related Outcomes Through Stage II Surgical Uncovering of Spectra-System Root Form Implants RICHARD S. TRUHLAR, DDS,* SAM E. FARISH, DMD,t LAWRENCE E. SCHEITLER, DDS, MPH,+ HAROLD F. MORRIS, DDS, MS,§ AND SHIGERU OCHI, PHD II Failure rates at second-stage surgery were reported for the ongoing Dental Implant Clinical Research Group studies of the Spectra-System (Core-Vent Corporation, Las Vegas, NV) implants. As of May 1995, 69 implants failed out of 2,633 placed and uncovered. The overall failure rate was 2.6%, with 3.6% in bone quality 1 (BQ-1), 2.4% in BQ-2, 2.5% in BQ-3, and 3.1% in BQ-4. HA coated cylinders had the lowest number of failures and titanium alloy baskets the highest. The basket design failed more often in the posterior jaw areas; 9 of 32 clinical centers (28%) accounted for 72% of these failures. vival. Misch10 states that the most important parame ter determining the rate at which an implant can be loaded is the density of the surrounding bone, the factor under least control of the surgeon. Lekholm and Zarb11 established a widely accepted classifica tion of the morphologic features of implant sites based on bone quality and residual jaw shape. This classification has been somewhat modified and sim plified by several authors. i, 0, Several studies have related implant failures to bone quality and ridge form. Jaffin and Berman13 reported that type 4 bone implant loss rates greatly exceeded that in other types of bone: 44% in the maxilla; 37% in the posterior mandible; and 10% in the anterior mandible. This is a total failure rate of 35%. Engquist et al placed 191 maxillary and 148 mandibular im plants to support overdentures. In that study, 78% of their failures occurred in quality 4 bone, whereas only 3% of implants were lost in types 1, 2, and 3 bone. There was a 35% loss rate for implants placed in type 4 bone. Presurgical determination of type 4 bone was recommended to decrease implant failure.1 The purpose of this article is to analyze the relation between bone quality and the incidence of implant failure from the time of implant placement through second-stage surgery and to describe the patterns of early failure of the various root-form designs of one system in various types of bone.

There are numerous reports in the dental literature on the failure rates of root-form implants of various types. 1-9 These studies show wide variation in failure rates and attribute failures to such factors as surgical technique, infection, premature loading, and bone quality at the site of placement. According to Friberg et al,7 jaw shape and bone quality must be regarded as the most influential factors affecting implant sur-

* Clinical Investigator, Dental Implant Clinical Research Group; Staff Periodontist, Department of Veterans Affairs Meilical Center, Northport, NY; Clinical Assistant Professor, Department of Peri odontics, School of Dental Medicine, State University of New York, Stony Brook. t Chief, Oral and Maxillofacial Surgery, Department of Veterans Affairs Medical Center, Atlanta, GA. t Chief, Dental Service, Department of Veterans Affairs Medical Center, Gainesville, FL; Clinical Professor of Periodontology, Uni versity of Florida College of Dentistry. § Codirector, Dental Clinical Research Center; Project Codirector, Dental Implant Clinical Research Group, Department of Veterans Affairs Medical Center, Dental Research, Ann Arbor, Ml. 11 Codirector, Dental Clinical Research Center; Project Codirector and Biostatistician, Dental Implant Clinical Research Group, Depart ment of Veterans Affairs Medical Center, Dental Research, Ann Arbor, MI. Address correspondence and reprint requests to Dr Morris: De partment of Veterans Affairs Medical Center, Dental Research (154), 2215 Fuller Rd, Ann Arbor, MI 48105.

This is a US government work. There are no restrictions on its use. 0278-2391/97/5512-5004$0.00/0

TRUHLAR ET AL

Table 1.

Implants and Prostheses in the DICRG Study Strata Number of Implants Placed

Implant Design

Implant Brand Name*

Maxillary fully edentulous (UCE)

5 or 6

Maxillary posterior partially edentulous (UP) Maxillary anterior single tooth (UST) Mandibular fully edentulous (LCE)

2 or 3

Grooved Screw Screw Grooved Cylinder Grooved

Micro-Vent Screw-Vent Screw-Vent Micro-Vent Bio-Vent Micro-Vent

HA-coated HA-coated Titanium-CF HA-coated HA-coated HA-coated

Mandibular posterior partially edentulous (LP)

2 or 3

Basket Screw Cylinder Basket Cylinder

Core-Vent Screw-Vent Bio-Vent Core-Vent Bio-Vent

Titanium alloy Titanium alloy HA-coated Titanium alloy HA-coated

Study Stratum

5 or 6

Implant Material

Prosthetic Application Bar-retained overdennire (implant supported only) Fixed-detachable partial denture Single crown (temporary cement) Fixed-detachable complete denture Fixed-detachable partial denture

* Micro-Vent, Screw-Vent, Bio-Vent, are Core-Vent are Spectra-System products (Core-Vent Corporation, Las Vegas, NV).

Method STUDY DESIGN

In 1991, the Dental Implant Clinical Research Group (DICRG) initiated two long-term, randomized, pro spective, multidisciplinary clinical studies (with study groups A and B) to investigate the influence of implant design, application, and site of placement on clinical success and crestal bone height. 14 In these studies, the primary statistical unit is the prosthesis (case), and the secondary unit is the implant. Cases were assigned to one of five study strata, which facilitated data analysis by implant location, degree of edentulism of the pa tient, and a multitude of baseline variables. The type of implant used in a certain location was determined by the study design (Table 1), with length and diameter chosen by the treatment team. 14 The study groups used the same strata and randomization plan. Differences between the two groups included the use of different alloys for restoration (each assigned four alloys) and different home care regimens (each assigned two regi mens for antimicrobial rinse and type of toothbrush). One group entered the study with more implant surgery experience. PARTICIPANTS

Participants are veterans eligible for dental treatment at Department of Veterans Affairs Medical Centers nationwide and patients at two university dental schools. They range in age from 20 years to more than 80 years and are, for the most part, white and male. Initial screening ensured suitability for treatment with endosseous dental implants, and extensive medical and dental histories were taken. 15 Adequate bone was one inclusion criterion, so patients with implant sites that would require augmentation were excluded by study

design. However, provision was made for the inclusion of sites that needed to be augmented or needed guided tissue regeneration because of a problem that devel oped at the time of surgery. These sites are usually jaw shapes D and E, per Lekholm and Zarb.11 Therefore, implant sites in the database included those with nor mal ridges or various degrees of ridge resorption, but with intact basal bone. MATERIALS

Implants used are part of the Spectra-System (Core Vent Corporation, Las Vegas, NV) (Fig 1). The follow ing designs were randomized: • Hydroxyapatite (HA)-coated grooved (Micro Vent Implant): HA-coated endosseous implant with ledged body design, vertical grooves, and internal hex-thread connection; lengths 7, 10, 13, and 16 mm; diameters 3.25 mm (3.5 mm collar) and 4.25 mm (4.5 mm collar); finishing drills 2.5/ 3.2 and 3.0/4.2 mm diameter • Ti screw, Ti alloy screw, and HA-coated screw (Screw-Vent Implant): Endosseous implant with externally threaded body and internal hex-thread connection with three materials options: commer cially pure titanium, titanium alloy, and HA coated; lengths 8, 10, 13, and 16 mm; diameters 3.5 mm (3.75 mm collar); finishing drill 3.2 mm • HA-coated cylinder (Bio-Vent Implant): HA coated endosseous implant with cylindrical body and internal hex-thread connection; lengths 8, 10.5, 13, and 16 mm; diameters 3.5 mm and 4.5 mm; finishing drills 3.5 and 4.5 mm • Ti alloy basket (Core-Vent Implant). Titanium alloy endosseous implant with basket design and externally threaded body, and internal hex-thread connection; lengths 8, 10.5, 13, and 16 mm; diam-

EFFECT'S OF

�-\_"ff DESIGN

5% 4%

c.2% 1% 0%

3 2 Decreasing Bone Quality -

FIGURE 2. Implant failure rates by bone quality: Pooled data from study group A and study group B (n = 2,839). The distribution of bone qualities for failed implants was similar (P = .528).

FIGURE.:. qualil)· (n =

:ulla, by bone

400 ,-------------------� Ill Stage I Ill Stage II

501-----------------...L.-40

i----------------

.!i 30 t----------§

B Study Group

Pooled

FIGURE 3. Distribution of 69 failed implants by study group and stage of treatment at failure.

5%r-------------------�

FIGL"RE qualil)

"ble, by bone

Ill Stage I Ill Stage II 4% � 3% I'll

roupA Group B = Pooled

c.2% § 1%

Decreasing Bone Quality

FIGURE 4. Implant failure rates by bone quality and stage of treatment at failure: Pooled data from study group A and study group B (n = 2,633).

300

360

\·ering times, I were not

TRUHLAR ET AL Table 3. Implant Failures (Failed/Uncovered; Percent): Timing of Failure and Bone Quality of Implant Sites Stage of Treatment

BQ-1

BQ-2

BQ-3

BQ-4

Stage I (n = 19) 5/224 (2.2) 8/1196 (0.7) 5/986 (0.5) 1/227 (0.4) Stage II (n = 50) 3/224 (1.3) 21/1196 (1.8) 20/986 (2.0) 6/227 (2.6) NOTE. 69 implant failures; 2,633 implants uncovered.

FAILURE PATTERNS

For each type of bone, implant failures through stage II surgical uncovering were categorized by jaw loca tion, application, and implant type (Table 4). Reasons for failure of implants in each type of bone are summa rized: Type 1 Bone In type 1 bone, 8 of 253 implants uncovered (3.2%) failed in the early treatment stages, with five (2.0%) occurring at stage I and three (1.2%) at stage II. Seven failed implants were located in the anterior mandible and planned for the treatment of complete edentulism, and one was in the posterior mandible (partially eden tulous). Failing implants were made of uncoated tita nium alloy, either of the basket or screw design. Six were medium length (10.5 or 13 mm), and two were

long (16 mm). No HA-coated implants placed in type 1 bone failed in treatment stage I or IL At stage I, four failures were associated with soft tissue and cortical plate defects without inflammation or pain, and one was associated with peri-implant infection. At stage II, two failures were mobile but asymptomatic; in one of these the mandible was perforated. One implant failure was associated with infection of soft tissue. Type 2 Bone In type 2 bone, 29 of 1,196 implants uncovered (2.4%) failed in the early treatment stages, with eight (0.7%) occurring at stage I and 21 (1.8%) at stage II. Six of 29 (21 %) were HA-coated, and 23 of 29 (79%) were uncoated commercially pure titanium or titanium alloy. Among designs, the 29 failed implants included 17 baskets (59%), eight screws (28%), two cylinders (7%), and two grooved (7%). Four failed implants were short (<10 mm), 20 were medium length (10, 10.5, or 13 mm), and five were long (16 mm). Seventeen (59%) were placed for the treatment of complete edentulism, 11 (38%) for partial edentulism, and one (3%) for max illary anterior single tooth replacement. There were 18 failures in the anterior jaw (62%) and 11 failures posteriorly (38%). During stage I, seven failures involved inflammation or peri-implant infection; three of these were associ ated with cortical plate defects and one with pain and paresthesia. One failure involved cortical plate defects with a history of dehiscence. At stage II, 11 failures involved inflammation or peri-implant infection; five

Table 4. Implant Failures Through Stage II Surgical Uncovering by Location, Prosthetic Application, Implant Design, and Bone Quality Location, Application, and Design Maxillary anterior Single tooth HA grooved Fully edentulous HA grooved Ti screw HA screw Maxillary posterior Partially edentulous HA cylinder HA grooved Mandibular anterior Fully edentulous HA cylinder Ti alloy basket Ti alloy screw Mandibular posterior Partially edentulous HA cylinder Ti alloy basket

BQ-1 (n = 8)

BQ-2 (n = 29)

BQ-3 (n = 25)

BQ-4 (n = 7)

Total (N = 69)

1 1 0

2 11

0 0 0

1 4 2

0 6 3

0 0

0 5 2

7 2

0 1 3

13 8

1 23

J Oral Maxillofac Surg 55:55-61, 1997, Suppl 5

The Influence of Bone Quality on Periotest Values of Endosseous Dental Implants at Stage II Surgery RICHARD S. TRUHLAR, DDS,* FRANK LAUCIELLO, DDS,t HAROLD F. MORRIS, DDS, MS,+ AND SHIGERU OCHI, PHO§ Periotest values (Periotest, Siemens AG, Bensheim, Germany) were recorded as a baseline variable at surgical uncovering in the ongoing multicenter, pro spective clinical studies of the Dental Implant Clinical Research Group, which uses implants from the Spectra-System (Core-Vent Corporation, Las Vegas, NV). For 2,212 osseointegrated implants, the mean Periotest value (PTV) of mandibular implants was -4.14 (anterior, -4.22; posterior, -4.06) versus -3.24 for maxillary implants (anterior, -2.91; posterior, -3.91). Implants in the densest bone (quality 1) had the lowest mean PTV (-4.13), followed by quality 2 (-4.00), quality 3 (-3.58), and quality 4 (-2.64). When a team of dentists is involved in treating a patient, as in implant dentistry, an objective, reproduc ible method of evaluation of the status of the bone implant complex is desirable. Clinicians generally agree it is important to verify the status of osseointegra tion of dental implants before attachment of abutments, before insertion of the implant-supported prostheses, and at various times during the maintenance phase. 1• As originally defined, the term osseointegration de scribed the direct bone-implant contact seen under light microscopy around rigidly fixed, immobile implants.2•3

Because the status of the interface has been impossible to assess in any reproducible manner short of resec tion,4-7 Albrektsson et al 8 suggested redefining osseoin tegration on the basis of a clinical examination in which implants are evaluated for clinical stability and freedom from complications, with rigid fixation achieved and maintained in bone during functional loading. If one accepts this paradigm shift, what is the best technique for determining rigid fixation clinically? Traditional methods are not sufficiently sensitive to quantify the amount of bone in contact with an implant and may not always be safe. Routine evaluation by radiographs, probing, and mobility have not been uni versally accepted. 9 Evaluation by serial radiographs poses certain safety questions associated with the use of ionizing radiation. Additionally, because radio graphs are only capable of a maximum resolution of 0.1 mm, they are not sufficient for evaluation of the direct bone-implant contact that exists on the micron scale. 10 Probing of an implant remains controversial because of the concern for disruption of the integrity of the soft tissue seal and possible penetration of the probe tip to alveolar bone. Clinically detectable mobil ity is a parameter of low sensitivity and high specific ity. 11 With a clinical mobility index, only two evalua tions are possible-mobility or no mobility. Evaluating osseointegration by the type of sound produced when the implant-abutment complex is tapped with the blunt end of a metallic instrument has not been validated scientifically. ' 0 A "ringing" sound

* Clinical Investigator, Dental Implant Clinical Research Group; Staff Periodontist, Department of Veterans Affairs Meclical Center, Northport, NY; Clinical Assistant Professor, Department of Peri odontics, School of Dental Medicine, State University of New York, Stony Brook. t Co-chair study group B, Dental Implant Clinical Research Group; Staff Prosthodontist, Department of Veterans Affairs Medical Center, Buffalo, NY; Clinical Associate Professor, Department of Restorative Dentistry, School of Dental Medicine, State University of New York, Buffalo. t Codirector, Dental Clinical Research Center; Project Coclirector, Dental Implant Clinical Research Group, Department of Veterans Affairs Medical Center, Dental Research, Ann Arbor, MI. § Codirector, Dental Clinical Research Center; Project Codirector and Biostatistician, Dental Implant Clinical Research Group, Depart ment of Veterans Affairs Medical Center, Dental Research, Ann Arbor, Ml. Address correspondence and reprint requests to Dr Morris: De partment of Veterans Affairs Medical Center, Dental Research (154), 2215 Fuller Rd, Ann Arbor, MI 48105. This is a US government work. There are no restrictions on its use. 0278-2391 /97/5512-5003$0.00/0

TRUHLAR ET AL

Table 1.

Implants and Prostheses in the DICRG Study Strata Number of Implants

Implant Design

Implant Name*

Implant Material

Upper completely edentulous (UCE)

5 or 6

Upper posterior partially edentulous (UP) Upper single tooth (UST) Lower completely edentulous (LCE)

2 or 3

Grooved Screw Screw Grooved Cylinder Grooved Basket Screw Cylinder Basket Cylinder

Micro-Vent Screw-Vent Screw-Vent Micro-Vent Bio-Vent Micro-Vent Core-Vent Screw-Vent Bio-Vent Core-Vent Bio-Vent

HA-coated HA-coated Titanium-CP HA-coated HA-coated HA-coated Titanium alloy Titanium alloy HA-coated Titanium alloy HA-coated

Stratum

5 or 6

Lower posterior partially edentulous (LP)

2 or 3

Prosthetic Application Bar-retained overdenture (implant supported only) Fixed-detachable partial denture Single crown Fixed-detachable complete denture Fixed-detachable partial denture

Abbreviations: CP, commercially pure; HA, hydroxyapatite. * Micro-Vent, Screw-Vent, Bio-Vent, and Core-Vent are Spectra-System products (Core-Vent Corporation, Las Vegas, NV).

mented on separate forms. ''Implant failure'' was de fined as the removal of an implant for one or more of the following reasons: implant mobility when tested; evidence of complete peri-implant radiolucency; per sistent pain or discomfort; or infection that is not re solved with the use of antibiotics or local treatment and occurs more than three times and requires treat ment during the first year after loading. Data entry was done by the staff of the data manage ment center, and data analysis was performed by the DICRG staff biostatistician. The distribution of Peri otest values at the time of implant uncovering was skewed, and therefore the data were transformed to a log distribution before analysis because the results were similar to those without such transformation. They are reported here as the untransformed data set. Because it was assumed that implant materials, implant lengths, and healing collar lengths were randomly dis tributed, the influence of these variables was not taken into consideration in this study. As of May 1995, the DICRG database had 2,910 implants. Sixty-three replacement implants and 206 implants that were still covered were not included in this analysis. Of the 2,641 implants placed and uncov ered, PTVs were recorded for 2,351. The Periotest

A - -1�mm1� - - --

B Glnglval tissues

Glnglval tissues

value (PTV) distribution curves for the two study groups were quite similar, except for Periotest +3 for group A (Fig 3A). One of two hospitals that entered the study after the first group of 30 had Periotest mea surements that differed significantly (Fig 3B). This sta tion was found to be following incorrect procedures, and the readings (123 implants) were excluded from this analysis. Additionally, 16 implants that had failed at uncovering had PTVs recorded. Subtracting these 16 and the 123 implants from the one clinical center noted above brought the database for these analyses to 2,212 implants. Periotest values for 2,212 integrated implants at the time of uncovering in study groups A and B were similar and, when combined, gave a mean PTV of -3.75 (Table 2). For the 31 centers, 92.2% of the readings were PTV O or less, and 99.0% were +09 or less. PTVs by jaw arch for both study groups were also similar. The mean PTV of mandibular implants (-4.14) was lower than that of maxillary implants (-3.24) (Table 3). Implants placed in the anterior man dible had the lowest mean PTV (-4.22), followed by the posterior mandible (-4.06), posterior maxilla (-3.91), and the anterior maxilla (-2.91) (Table 4). By treatment category, single implants in the ante rior maxilla had the lowest mean PTV (-4.74), and implants in the completely edentulous maxilla had the highest mean PTV (-2.22) (Table 5). Based on bone quality, implants in the densest bone (quality 1) had the lowest mean PTV (-4.13), followed by quality 2 (-4.00), quality 3 (-3.58), and quality 4 (-2.64) (Ta ble 6). Discussion

FIGURE l. The correct angle of the Periotest device relative to the surface of the abutment is 90 degrees. A, Co1Tect. B, Incon-ect.

The 1994 report by the DICRG25 reported PTV means ± SD by quadrant and bone density. The rela tionships identified in that report remain consistent in

60 in qualities 2 through 4 bone as well as variations in cellular remodeling cycles that determine the rapidity of bone formation. As the bone-implant interface con tinues to mature, the change in PTVs may be more favorable in the latter group than in the former. An other potential source of variation for PTV readings includes abutment length. Olive and Aparicio26 con cluded that longer abutment lengths result in less favor able PTVs. However, in their design, when the coronal edge of the abutment was covered by gingival tissues, an additional 3-mm gold cylinder was attached to pro vide a surface for the Pe1iotest to percuss. In their analysis, this deviation in protocol was not addressed. Teerlinck et al27 also concluded that abutment length significantly affected PTVs, but this was only when measurements were made without removing a Dolder bar that splinted the two implants. When the fixture abutment complex was measured with the Dolder bar removed, abutment length had no significant effect on PTVs. Van Steenberghe and Quirynen33 have implied that the prognostic value of the Periotest remains unproven with regard to implants, because too few failures have been studied and reported in the literature. However, recent reports in the literature have suggested that the Periotest is sensitive enough to discriminate longitudi nally among implant responses to loading forces. 34-36 Van Steenberghe et al reported that over 5 years the mean PTVs and standard deviations for 62 mandibular and 157 maxillary Branemark implants initially placed both decreased. It is anticipated that the current long term clinical investigation by the DICRG will provide a sufficient quantity of prospective data to confirm the value of the Periotest in oral implantology. The clinical significance of the PTV numbers to clinicians and researchers is anticipated not only to be in determining whether an implant has properly integrated at uncovering, but also in monitoring the status of the bone-implant complex when individual implants are functioning under a prosthetic load. In the event a complication occurs that results in the failure of an implant, an accurate series of PTVs could help identify at what point in the treatment process the pathologic process started. Future data may show a correlation between an optimal PTV at uncovering and long-term clinical performance of the implant. References 1. Adell R, Lek:holm U, Rockier B, et al: A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 10:387, 1981 2. Branemark P-I: Introduction to osseointegration, in Branemark P-I, Zarb GA, Albrektsson T (eds): Tissue-Integrated Prosthe ses: Osseointegration in Clinical Dentistry. Chicago, IL, Quintessence, 1985, pp ll-76 3. Branemark P-I, Hansson BO, Adell R, et al: Osseointegrated implants in the treatment of the edentulous jaw: Experience

STAGE II EFFECTS OF BONE QUALITY O

4. 5. 6. 7. 8. 9. 10. 11.

12. 13.

14. 15.

16. 17. 18. 19. 20. 21.

22. 23. 24.

25. 26. 27.

PERIOTEST

from a 10-year period. Scand J Plast Reconstr Surg 11: 1, 1977 (suppl 16) Johansson C, Albrektsson T: Integration of screw implants in the rabbit: A 1-yr follow-up of remo al torque of titanium implants. Int J Oral Maxillofac Implants 2:69. 1987 Tjellstrom A, Jacobsson M, Albrektsson T: Removal torque of osseointegrated craniofacial implants: A clinical study. Int J Oral Maxillofac Implants 3:287, 1988 Roberts WE, Smith RK, Zilberman Y, et al: Osseous adaptation to continuous loading of rigid endosseous implants. Am J Orthod 86:95, 1984 Roberts WE, Turley PK, Brezniak N, et al: Bone physiology and metabolism. J Calif Dent Assoc 15:54, 1987 Albrektsson TO, Johansson CB, Sennerby L: Biological aspects of implant dentistry: Osseointegration. Periodontology 2000 4:58, 1994 Smith DE, Zarb GA: Criteria for success of osseointegrated endosseous implants. J Prosthet Dent 62:567, 1989 Albrek:tsson T, Albrektsson B: Osseointegration of bone im plants: A review of an alternative mode of fixation. Acta Orthop Scand 58:567, 1987 Buser D, Weber HP, Lang NP: Tissue integration of non-sub merged implants: I-Year results of a prospective study with 100 ITI hollow-cylinder and hollow-screw implants. C!in Oral Implants Res 1:33, 1990 Roberts WE, Helm FR, Marshall KJ, et al: Rigid endosseous implants for orthodontic and orthopedic anchorage. Angle Orthod 59:247, 1989 Carr AB, Larsen PE, Papazoglou E, et al: Reverse torque failure of screw-shaped implants in baboons: Baseline data for abut ment torque application. Int J Oral Maxillofac Implants 10:167, 1995 Sullivan DY, Sherwood RL, Collins TA, et al: The reverse torque test: A clinical repmt. Int J Oral Maxillofac Implants 11:179, 1996 d'Hoedt B, Schulte W: Moglichkeiten und Langzeitergebnisse bei der Anwendung TUbinger Implatate (Frialite) [possibili ties and long-term results of use of Tubingen implants]. ZWR 96:118, 1987 Manz MC, Morris HF, Ochi S, et al: An evaluation of the Periotest system. Part I: Examiner reliability and repeatability of readings. Implant Dent 1:142, 1992 Manz MC, Morris HF, Ochi S, et al: An evaluation of the Periotest system. Part II: Reliability and repeatability of in struments. Implant Dent 1:221, 1992 d'Hoedt B, Lukas D, MUhlbradt L, et al: Das Periotest ve1fah ren-Entwicklung und clinische PrUfung [the Periotest® research and clinical trials]. Dtsch Zahnartzl Z 40: 113, 1985 Schulte W, Lukas D: The Periotest method. Int Dent J 42:433, 1992 Schulte W, Lukas D: Periotest to monitor osseointegration and to check the occlusion in oral implantology. J Oral Implant 19:23, 1993 Morris HF, Ochi S, Dental Implant Clinical Research Group (Planning Committee): The influence of implant design, ap plication, and site on clinical performance and crestal bone: A multicenter, multidisciplinary clinical study. Implant Dent 1:49, 1992 Lambert P, Morris HF, Ochi S, et al: Relationship between implant surgical experience and second-stage failures: DICRG interim report no. 2. Implant Dent 3:97, 1994 Schulte W: The new Periotest® method. Compend Contin Educ Dent Suppl 12:S410, 1988 Lekholm U, Za.rb GA: Patient selection and preparation, in Branemark P-I, Zarb GA, Albrektsson T (eds): Tissue-Inte grated Prostheses: Osseointegration in Clinical Dentistry. Chicago, IL, Quintessence, 1985, pp 199-209 Truhlar RS, Morris HF, Ochi S, et al: Assessment of implant mobility at second-stage surgery \ ith the Periotest: DICRG interim report no. 3. Implant Dent 3:153, 1994 Olive J, Aparicio C: The Periotest method as a measure of osseointegrated oral implant stabili . Int J Oral Maxillofac Implants 5:390, 1990 Teerlinck J, Quirynen M, Darius P. et al: Periotest®: An objec-

MICHAEL C. MANZ

studies will assess implant survival along with specific complications and adverse responses associated with dental implant treatment. Other aspects of treatment, including plaque and calculus accumulation, soft tissue response, and patient satisfaction, will be monitored. Some special considerations usually apply when conducting dental-related clinical research. Most stud ies of dental outcomes of interest are by necessity lengthy. Caries and periodontal disease are slow in progression, and therefore long periods are required to evaluate preventive or treatment regimens. Similarly clinical evaluation of restorations-or, as in these studies, dental implants-requires sufficiently long pe riods to follow physiologic changes and evaluate lon gevity. Additionally, large sample sizes are required in situations in which safety is already well established and when studies are planned to investigate marginal differences. Methods STUDY POPULATION

The subjects for these studies have been recruited from 32 sites, 30 of which are DVA medical centers with patients recruited and treated in the Dental Ser vices of these centers. The other two sites, the Univer sity of Louisville and the University of Pennsylvania, are university-based dental implant research clinics. Patients are initially screened for general health or oral conditions that disqualify them from participation in the studies; patients who meet the study criteria and agree to participate are entered into the studies. Several study case types are being investigated, in cluding mandibular and maxillary fully and partially edentulous cases, and maxillary anterior single tooth replacement cases. Depending on the case type, differ ent implant designs from the Spectra-System implant system (Core-Vent Corporation, Las Vegas, NV) are randomly assigned to the sites for implantation in each case. The appropriate length and diameter for the im plants are determined by the surgeon placing the im plants. If alterations are made that deviate from defined study treatments, the cases are assigned to an alternate study stratum for separate analysis. Sample sizes for the DICRG studies were calculated to ensure sufficient power to test the main hypotheses of the DICRG study. Final patient accrual goals for the studies were set using these calculations for minimum sample size requirements as a guide. More than one study case can be initiated and followed in a single study patient if conditions allow. The studies have ac cumulated a large number of study patients and cases, with recent totals exceeding 700 study patients and 1,000 study cases.

Table 1. Bone Level Relative to Top of Implant by Study Examination (in millimeters) Examination

Implant insertion 1,354 Implant uncovering 1,233 Six-month follow-up 897

Minimum Maximum Mean SD 0 0 0.1

5.6 12.2 9.3

0.5 1.5 2.6

0.6 1.2 1.2

DATA COLLECTION

Direct bone level measurements are made at implant insertion and implant uncovering appointments be cause the bone is exposed in completing the surgical procedures. These direct measurements can be used to check the reliability of measurements made from the radiographs taken at these appointments. Radiographs are also taken when the final prosthesis is inserted and at follow-up appointments, which are scheduled for all study patients based on the date of implant uncovering. These appointments are scheduled at 6 months, at 1 year, and then yearly thereafter for a period of 6 years. Direct measurements are not made at the time of pros thesis placement and at the follow-up appointments to avoid further tissue trauma and possible compromise of the peri-implant tissues, which may, in tum, increase the chances of implant complications or failure. Radiographs of the implant cases are sent to the project director's office, where they are labeled and catalogued. The radiographs are then mounted on a flat viewbox and measurements are made to the nearest 0.1 mm using vernier calipers. Vertical measurements of bone level adjacent to the implants are made from the top of the implant, which provides a fixed reference point (Fig 2). Measurements taken from the radio graphs at implant uncovering are used as the baseline for radiographs taken at subsequent follow-up evalua tions. Although generally the implant should be in serted so that its top is flush with the level of the crestal bone, deviations often occur. These deviations must be accounted for when determining the change in bone level at subsequent appointments. In determining actual bone loss from radiographic measurements, particularly on panoramic radiographs that generally provide an enlarged image of teeth and implants, calibration of the measured increments of bone change is required. Calibration is the process of correcting and standardizing measurements in radio graphic analysis so that accurate and valid measure ments of changes in bone over time may be made. The measurement from the top of the implant to the point of bone-implant interface is calibrated using the known and the radiographically measured length of the im plant. This calibration involves multiplying the bone height measurements by the ratio of the known to the

66 Frequency

400r-------------------, 3001------

..•.-:-:-:-:-:-:-:-::-:.:-:-:. .·.·...·..·..·..·..·..·.·...·.· ..· ·..·.. ·...·.·.. :;::::::: ::::::::::;::::::::::;,:, .·.·.·.·..· ·..· ·,·... · ·.·.·.·.·.·

309

2001------

................. .•.•,, •.·.· ·.·.·.. ·.·.·.·.·.· . .. ....·., ·...........

:::::::::::::::::::::::::::::::::·

........... , .... ..... .

·.·.·.·.·.·.·.·.·.· ..·..· ·.·.·. FIGURE 2. Radiographic measurement sites and formulas used for analysis. Measurement average of bone from top of implant = (A + B)/2. Actual average distance = (A + B) (known length)/2C. Proportion of implant not directly apposed to bone = (A + B)/2C.

measured implant length. Formulas used for calibration appear in Figure 2. The calibrated (ie, actual) distance at the time of implant uncovering is subtracted from all subsequent calibrated vertical bone measurements for a given implant in determining bone height changes. Negative values are not assigned in cases in which the bone level is above the level of the implant, because the amount of implant-bone contact is consid ered to be the factor of primary importance. DATA ENTRY

Measurements and bone pattern assessments are en tered onto paper forms. These forms, which include case information, are generated by the FoxPro data management software (Microsoft Corporation, Red mond, WA) using databases with information entered from study forms sent to the DICRG Data Management Center (Ann Arbor, MI). The measurements, along

FIGURE 4. Frequency di ai Implant uncovering to 6-momh ---�,n,•-�-

tered into a data set usin .:: Stone Mountain, GA) da package. Entry is double""'-'",C,.."""� ..... ,�"""·-:T=,...,ror rechecks entry errors have been m measurements, data entry. .:: data set to ensure clean, accurate ANALY

The Epi Info program p.m bilities. Certain aspec o - ibe pleted using this program.. • created in Epi Info i al Institute Inc., Cary. C) Variables are created and u.::.�,a.,..-:::1;. analysis. The use of appropri an important aspect of lhese �.._..__,_ interim stage in the .:nll,u.i''"""" complete. The result pfl"",:c"C.::�,

Frequency

100�-----------------�

600 !---------------------< 5001---400 >---3001---2001---100 ..----0

..._ ,o

L..'v

""'o

'-"

Evaluation Times Contacting bo� Vertical Bone Change (mm)

FIGURE 3. Frequency distribution for bone loss measurements: Implant placement to implant uncovering.

urements:

·� . . .

I I I I _ I_

Not contacting bone

FIGURE 5. Direct ll. IIIK=·--Q:llae li;;i!CS:::ai total implant surface.

I I I -�I I I I I l�I 0212

proportion of

MICHAEL C. MANZ

■

HA l!I non-HA mm 1.6 r----------------1.2t-----0.8 0.6 0.4 0.2 0

■

' ;

! !

•

■ ■ • -

I _ ___J_�■_J __�I Stage 1 to 2

1.6 ,---------------

1 0.8 0.6 0.4 0.2

Stage 2 to 6 mo.

Stage 1 to 2

Evaluation Time Intervals

FIGURE 6. Mean peri-implant vertical bone change for study in tervals: HA vs non-HA.

fore primarily descriptive and intended only to provide indications of trends seen in the data to this point. Data from the two DICRG studies were pooled to simplify the presentation of these preliminary findings. Results are presented on bone loss overall, and on bone loss stratified by various predictor variables. As the data base on radiographic bone loss becomes more com plete, a more comprehensive analysis of the data will be conducted. Results

The mean actual bone levels calculated from the calibration formulas for the different study examina tion appointments are shown in Table 1. For data col lected to this point, the overall average bone loss be tween implant insertion and implant uncovering is 0.94 mm. Average overall bone loss between implant un covering and 6 months after uncovering is 1.14 mm. The distributions of bone change measurements for the two study intervals are shown in Figures 3 and 4.

■ Mandible l!l Maxilla

mm 1.4 ,-----------------� 1.2 t-------------1

1---�---,,,____

0.8

Ill Anterior I!!! Posterior

Stage 2 to 6 mo.

Evaluation Time Intervals

FIGURE 8. Mean peri-implant vertical bone change for study in tervals: Anterior vs posterior.

The average proportion of the implant that radio graphically appears to be in direct contact with bone at the different study evaluation points is shown in Figure 5. The top portions of the bars indicate the mean proportion of the implants not in direct contact with bone, providing an indication of vertical bone loss rela tive to the length of the implant. The mean proportion, of the implants not in direct contact with bone as evalu ated radiographically, increases from about 4.5% at implant insertion to 21.2% at the 6-month follow-up. The remainder of the results primarily show the bi variate relationships of various predictor variables in the studies to radiographic bone loss. Vertical bone changes for HA-coated versus non-HA-coated im plants are compared for the two study intervals in Fig ure 6. Non-HA-coated implants show more vertical bone loss at both intervals. Figure 7 shows average vertical bone loss for im plants placed in the maxilla compared with bone loss for implants placed in the mandible. For the two study intervals shown in the figure, there is more average ll Mandible

mm 2

■

Maxilla

1.5

0.6 0. 4

0.5

0.2

Stage 1 to 2

Stage 2 to 6 mo.

Evaluation Time Intervals

FIGURE 7. Mean peri-implant vertical bone change for study in tervals: Mandible vs maxilla.

Ant

Post

Stage 1 to2

Ant

Post

Stage 2 to 6 mo.

FIGURE 9. Mean peri-implant vertical bone change for study in tervals by arch location.

PERI-IMPLANT RADIOGRAPHIC BONE LOSS II Mandible Ill Maxilla mm 2.5 ,------------------,

■

Bone Score = 1

■

Bone Score = 2

□ Bone Score = 3 !!!!I Bone Score = 4

mm 1.6 --------------------, 1.44 1,4 l-------------

1.21-----------.--.-l 0.8 0.6

0.5

0.4

non-HA

Stage 1 to 2

non-HA

Stage 2 to 6 mo.

FIGURE 10. Mean peri-implant vertical bone change for study intervals by HA vs non-HA and mandible vs maxilla.

vertical bone loss around implants placed in the max illa than around those placed in the mandible. There is also more bone loss in both study intervals for implants placed in anterior regions of the maxilla and mandible than in posterior regions (Fig 8). Figure 9 shows a further breakdown by jaw location. For the two study intervals, the tendencies for more bone loss in the max illa than the mandible, and more bone loss in anterior regions than posterior regions, generally hold. Figure 10 displays the comparison of bone loss be tween implants with and without HA coating stratified by arch. The figure shows a trend of more bone loss in noncoated implants and implants placed in the maxilla up to 6 months after uncovering. Figure 11 displays mean vertical bone loss between implant placement and implant uncovering by case type. More bone loss is seen in completely edentulous cases for both the maxilla and mandible. The figure also shows that mean bone loss for the different man-

1.2

Stage 2 to 6 mo.

FIGURE 12. Mean peri-implant vertical bone change for study intervals by bone quality score.

dibular case types are all intermediate between com pletely edentulous maxillary cases and the other ty�es of maxillary cases. Vertical bone loss by bone quahty, as evaluated at the implant placement surgery, is shown in Figure 12. The figure shows a slight tendency for more vertical bone loss with the increasing numeric designations for bone quality type, particularly be tween the implant uncovering and the 6-month follow up examination. Figure 13 shows bone change between implant placement and uncovering for the different implant designs being studied. For this study stage, the least amount of bone loss is seen with the Bio-Vent design, followed by Micro-Vent, Screw-Vent (titanium alloy), Screw-Vent (HA-coated), Core-Vent, and Screw-Vent (commercially pure titanium). Discussion

2------------------,

0.91

0.8 ..,___

..._

0.6 ..,___

,....._

0.2 >--0

Stage 1 to 2

Overall, the implants in this study experienced about 1 mm bone loss between implant insertion and implant

mm 1.4

0.4

0.2

'---

>--

..._

0.85 >--

..._ LCE LRP LLP

Mandibular Cases

0.69 0.62_ t_iu;a_ >--

- -

>--

..._ � UCE URP ULP UST

1.s 1--------------

0.5

Maxillary Cases

FIGURE 11. Mean peri-implant vertical bone change by case type: Implant insertion to implant uncovering. LCE, lower completely edentulous; LRP, lower right posterior; LLP, lower left postenor; UCE, upper completely edentulous; URP, upper right posterior; ULP, upper left posterior; UST, upper single tooth.

FIGURE 13. Mean peri-implant vertical bone change by implant design:implant insertion to implant uncovering.

MICHAEL C. MANZ

uncovering, and another millimeter of bone loss be tween implant uncovering and 6 months post-uncov ering. It is difficult to compare bone loss in these early stages of the DICRG studies with other studies because publications from other studies generally have not re ported on bone loss occurring during these early stages. Although the data collection to this point is not suffi cient to report findings, preliminary indications are that, after the initial stages, the rate of vertical bone loss around DICRG study implants declines substan tially. As the DICRG studies continue, data will show whether the bone loss seen in these later study intervals falls in the range of bone loss rep01ted in other stud ies.23-26 Direct comparisons with other studies will be made when data collection is more complete. The distribution of bone change measurements for the two study intervals up to 6 months after uncovering are seen in Figures 3 and 4. These figures show the distribution of bone loss measurements for those im plants on which measurements were completed for both the beginning and ending study appointments for the intervals. The distribution of measurements for bone change between implant insertion and implant uncovering is skewed toward higher values of bone loss, with most measurements falling between O and 1 mm. The measurements for the interval between im plant uncovering and 6 months after uncovering shift slightly away from O and appear to be somewhat more normally distributed and less severely skewed. Higher measurement values, which cause skewing of the dis tributions, act to pull up the means for the interval measurements. The medians provided in the distribu tion figures a.re lower than the means for the two study intervals (medians of 0.7 and 0.99 vs means of 0.94 and 1.14). The normality of measurement distributions must be considered in future data analysis. These measurement distributions indicate that in the early stage after implant insertion most implants show little loss of bone, with a small proportion of implants having substantially more bone loss. Continuing re search in this and other studies should investigate the variables associated with those implants showing rapid early vertical bone loss. Figure 5 relates the same information on overall bone loss in a different way. The upper sections of the bars indicate the average proportion of the implants that do not appear radiographically to be in direct ap proximation to bone, providing an indication of verti cal bone loss relative to implant length in the study evaluations. On average, about 95.5% of the study im plants appear radiographically to be in direct contact with bone at implant insertion. This proportion drops to 87.5% at implant uncovering, and 78.8% at 6 months after uncovering. This information can be evaluated and related to current ideas on the percentage of direct bone-implant contact necessary to bear the mechanical

69 stress and loading forces placed on dental implants when prosthetic restoration has been completed. The results shown in Figures 6 through 13 show various and overlapping relationships of different study variables to vertical bone loss around implants. More bone loss is associated with non-HA-coated im plants than with HA-coated implants (Fig 6) in the early study intervals. It is possible that these findings may relate to the immediate biologic reaction to the implant surface at implant placement. Whether the trend for greater bone loss with non-HA implants in these studies remains after a period of healing and stabilization of the implants will be evaluated as fol low-up results continue to be gathered. Overall, more vertical bone loss appears to be asso ciated with implants placed in the maxilla than the mandible, and with implants placed in anterior regions than with those in posterior regions (Figs 7 and 8). Unlike the HA versus non-HA comparison, smaller differences were noted in the interval between implant placement and implant uncovering, with the greatest differences appearing in the interval between implant uncovering and 6 months after uncovering for these implant location variables. The further categorization of implant location in Figure 9 shows bone change results stratified by arch and anterior/posterior location. Generally, in the earlier study intervals the greatest vertical bone loss is seen around implants placed in the maxillary anterior region, followed by the mandibular anterior region, with posterior regions in both arches showing the least amounts of vertical bone loss. Whether bone loss differences by arch location a.re mostly confined to the initial stages after implant inser tion will continue to be evaluated as data collection continues. Figure 10 shows results for HA-coated versus non coated implants stratified by arch. The same basic trends described for the bivariate relationships of arch to bone loss and HA coating to bone loss are still apparent in this figure. In both study intervals, less bone loss is associated with HA-coated implants and with implants placed in the mandible. From these re sults, the relationship of HA coating and arch to bone loss is still apparent and would appear to be additive. The results shown in Figure 11 provide an indication of a more complex interrelation of the different predictor variables in these studies. From this figure it is evident that the tendency for greater bone loss in the maxilla than in the mandible (Fig 7) for the interval between implant insertion and implant uncovering is entirely accounted for by bone loss a.round implants in completely edentulous cases. Maxillary implants for partially edentulous and sin gle tooth cases actually show less bone loss on average than implants for any of the different types of mandibular cases. The greater vertical bone loss seen in the completely edentulous cases for both arches might be related to the

MORRIS, MANZ, AND TAROLLI

Table 1.

Implants and Prostheses in the DICRG Study Strata

Stratum

Prosthetic Application

Number of Implants

Implant Design

Implant Material

Implant Name*

Basket Screw Cylinder Basket Cylinder Grooved Screw Screw Grooved Cylinder Grooved

Ti6A14V Ti6Al4V HA-coated Ti6Al4V HA-coated HA-coated HA-coated cpTi HA-coated HA-coated HA-coated

Core-Vent Screw-Vent Bio-Vent Core-Vent Bio-Vent Micro-Vent Screw-Vent Screw-Vent Micro-Vent Bio-Vent Micro-Vent

Lower completely edentulous (LCE)

Full denture

5 or 6

Lower posterior (LP)

Posterior bridge

2 or 3

Upper completely edentulous (UCE)

Bar overdenture

5 or 6

Upper posterior (UP)

Posterior bridge

2 or 3

Upper single tooth (UST)

Single crown

NOTE. cpTi, commercially pure titanium; HA, hydroxyapatite. * Micro-Vent, Screw-Vent, Bio-Vent, and Core-Vent and Spectra-System products (Core-Vent Corporation, Las Vegas, NV).

rates of success and then evaluated to see if past experi ence, operator skill, or other factors might explain the difference in success rates. This article reports on the distribution of implant failures across study sites and by implant design in an attempt to address these ideas on the relation of clinical factors to implant success. The source of data for this report was the ongoing prospective, multicenter clini cal studies of the Dental Implant Clinical Research Group (DICRG) that were started in 1991 to investi gate the influence of implant design, application, and site on clinical performance and crestal bone. to Be cause the report only spans the time from implant placement through uncovering, the trends seen in the results may not be predictive of the long-term survival of the study implants. Materials and Methods

The DICRG study design includes five treatment categories (research strata) of approximately equal size (Table 1). These are the lower completely edentulous stratum (LCE), the lower posterior partially edentulous stratum (LP), the upper completely edentulous stratum (UCE), the upper posterior partially edentulous stratum (UP), and the upper single tooth stratum (UST). Three types of implant were assigned and randomized for the LCE and UCE cases. Two types of implant were assigned and randomized for the LP and UP cases. One type of implant was used in the UST stratum cases. Thirty Department of Veterans Affairs medical cen ters and two universities are participating in the studies. They are administered as two study groups of approxi mately equal size, each using the same study design and yielding similar numbers of implants placed in the five study strata so that data may be compared. Clinicians received training in procedures related to the implant system and data collection.

Patients are from various socioeconomic levels and range in age from 20 to 80 years and older (mean, 62.9). They are predominately white male veterans (77.8% white; 15.0% African American, 4.5% Latin American, 1.4% Asian, 0.5% Native American, 0.8% missing data; 93.5% male, 6.4% female, 0.1% missing data). Initial screening was performed to ensure that endosseous dental implant treatment was appropriate, and extensive dental and medical history data were collected. ASA health status categories represented are "healthy," "mild systemic disease," and "severe sys temic disease." ASA status was previously reported to be associated with implant survival at uncovering. 11 The implants used are part of the Spectra-System (Core-Vent Corporation, Las Vegas, NV), which in cludes screw, cylinder, basket, and grooved press-fit designs, all with an internal hexagon-and-thread con nection. Implant length and diameter were chosen by the treatment team. Implants were placed according to standard implant surgical protocol, and sutures were removed 5 to 7 days postoperatively. Use of preopera tive antibiotics was optional, and use of an antimicro bial rinse postoperatively for 2 weeks was recom mended. Fifty percent of the clinical centers were randomized to continue use of an antimicrobial rinse for the duration of the study. Standardized forms were used to collect data. Data were entered by the staff of the Data Management Center in Ann Arbor, Michigan, and analyzed by the study biostatistician at the Data Management Center. The analysis covers the period up to and including the end point of surgical uncovering, with results reported primarily as the proportion of implants surviving to the defined end point for this analysis. This report does not reflect the success of study implants after uncov ering or long-term clinical results after implant load ing. For this analysis, an implant was considered as a failure if it was removed because of mobility or chronic

MORRIS, MANZ, AND TAROLLI

Implant Survival to Uncovering

Implant Survival to Uncovering 1QQ%

99 .6

100

1 O % _,,,� O;,;; ,,;, ccr--,-,i,;;,;;,,;,;,.,------9fr:,r'll,--

100%

80%

60%

40%

20%

n =251 n=208

HA-cyl

HA-grv

n =27

HA-scr

n =73

Alloy-scr

n=32

n=142

cpTi-scr Alloy-bskt

n =206 n= 125 HA-grv

HA-cyl

n =41

HA-scr

n=69

Alloy-scr

n=38

n= 144

cpTi-scr Alloy-bskt

FIGURE 2. Implant survival comparison by implant type for the upper quartile success class (n = 733).

FIGURE 4. Implant survival comparison by implant type for the lower quartile success class (n = 623).

(0% to 1.0%) and HA grooved implants (0% to 1.6%). The failure percentages ranged higher for the HA screw (0% to 7.3%), alloy screw (0% to 7.2%), and cpTi screw (3.1% to 7.9%) implants. The alloy basket showed the widest range of failure percentages across the three success groupings (0% to 15.3%).

LP stratum, there were no failures among 113 HA cylinder and 72 alloy basket implants. In the UST stra tum (not shown), there were no failures among the 63 HA grooved implants.

COMPARISON OF IMPLANTS WITHIN STUDY STRATA BY SUCCESS GROUPINGS

Top 25% In the upper quartile success class (Fig 5), only two implant failures occurred. Within the UCE stratum, 1 of 32 cpTi screws failed, and there were no HA grooved (n = 59) or HA screw (n = 27) failures. In the UP stratum, 1 of 53 HA cylinders failed, with no failures among 83 HA grooved implants. In the LCE stratum, there were no failures among 85 HA cylinder, 73 alloy screw, and 70 alloy basket implants. In the

Middle 50% In the middle quartiles success class (Fig 6), there were 30 implant failures: 14 alloy basket, seven cpTi screw, four HA grooved, three alloy screw, and two HA screw implants. In the UCE stratum, 7 of 123 cpTi screws failed (5.7%), compared with 2 of 131 HA grooved (1.5%) and 2 of 118 HA screw (1.7%) im plants. In the UP stratum, there were no failures among 74 HA cylinder and 110 HA grooved implants. In the

Implant Survival

Implant Survival 100%

80% 60%

Implant Survival to Uncovering

100%

n=59

HAg - rooved

80%

n=27

HA-screw

n=32 cpTl-scrow

n=53

HA-cyllnder

n=83

HA.grooved

Implant Survival

40% HA-cylinder

20% 0%

n =407 n=375 n=120 n=148 n=127 n= 314

HA-cyl

HA-grv

HA-scr

Alloy-scr

cpTi-scr Alloy-bskt

FIGURE 3. Implant survival comparison by implant type for the middle quartiles success class (n = 1,491).

Alloy-screw

Alloy-basket

HA-cylinder

Alloy-basket

FIGURE 5. Implant survival comparisons within study strata for the upper quartile success class (n = 730). UCE, upper completely edentulous stratum (n = 118); UP, upper posterior partially edentu lous stratum (n = 136); LCE, lower completely edentulous stratum (n = 228); LP, lower posterior pattially edentulous stratum (n = 185). UST stratum (not shown) (upper single tooth stratum) (n = 63 HA grooved implants; 100% survival).

MORRIS, MANZ, AND TAROLLT

Table 2. Prior Experience With Implants of Clinical Center Success Groups Clinical Centers Ranked by Implant Success

Number of More Experienced Clinical Centers

Number of Less Expe1ienced Clinical Centers

Top 25% Middle 50% Bottom 25%

5 7

(UP), only one of the HA cylinder (n = 160) and one of the HA grooved (n = 233) implants failed (survival percentages of 99.4% and 99.6%, respectively). In the upper single tooth stratum (UST) (not shown), in which only HA grooved implants were used, there was a 98.7% survival percentage, with only three failed implants (n = 235). STUDY SITE RESULTS

Implant survival to uncovering for all implant de signs combined differed among the 32 study sites, ranging from 100% to 89.8% (mean, 97.6%; N = 2,847 implants). For each of the implant designs, at least some of the study sites experienced 100% success rates. The lowest success among study sites was 96.2% (25 of 26) for HA cylinders; 93.3% (14 of 15) for HA grooved implants; 75% (three of four) for HA screws; 84.6% (11 of 13) for alloy screws; 80% (four of five, two stations; 8 of 10, one station) for cpTi screws; and 75% (12 of 16) for alloy baskets. The results for the various implant designs by study site further showed that no site had more than two failures of any specific implant design except for the alloy basket implants. Five sites had three to five fail ures with this particular design, whereas 13 sites had no alloy basket failures and another 10 sites had only one alloy basket failure. The five sites with more than two alloy basket failures, while placing only 18% of the total alloy baskets in the study, accounted for half (18 of 36) of the total alloy basket failures. COMPARISON BY PRIOR EXPERIENCE WITH IMPLANT PLACEMENT

Sixteen principal surgeons had placed 50 or more implants (more experienced), and 16 had placed fewer than 50 implants (less experienced) before participa tion in the study. The distribution of surgeons by prior experience among the quartile success groupings is displayed in Table 2. Although the upper quartile was evenly divided between more and less experienced sur geons, a definite difference appeared in the middle and lower groupings. More experienced surgeons exceeded less experienced surgeons in the middle grouping, and

all but one of the surgeons in the lower quartile group ing was classified as having less experience. The percentage of implant failure also differed by surgeon experience. The failure percentage was nearly twice as high (3.22% vs 1.69%) for surgeons having less experience in the placement of dental implants before the DICRG study (44 failures of 1,367 placed) than for the more experienced surgeons (25 failures/ 1,480 placed). Furthermore, the lowest six study sites in percentage success were sites with surgeons classi fied as having less experience before the DICRG study. They experienced 48% (33 of 69) of the total study failures at uncovering, while placing only 18% (525 of 2,847) of the total study implants. For all implant designs, higher percentages of failure were seen with the less experienced surgeons. Percent ages of failure for the different implant designs by prior experience were HA cylinder-more experienced 0% (0 of 401), less experienced 0.65% (3 of 463); HA grooved-more experienced 0.81% (3 of 370), less experienced 0.89% (3 of 338); HA screw-more expe rienced 0.81% (1 of 123), less experienced 6.15% (4 of 65); cpTi screw-more experienced 4.92% (6 of 122), less experienced 6.67% (5 of 75); alloy screw more experienced 1.37% (2 of 146), less experienced 4.17% (6 of 144); alloy basket-more experienced 4.09% (13 of 318), less experienced 8.16% (23 of 282). Discussion

Initial studies conducted on dental implant systems usually tend to focus on an evaluation of efficacy (per formance under ideal conditions with carefully selected patients and with skilled and experienced surgeons). The DICRG studies recruited study sites without spe cific inclusion criteria on the amount of experience with the placement of dental implants in general, expe rience with specific implant systems, or the level of skill of the implant treatment team as indicated by past success rates with dental implant treatment. Addition ally, exclusion criteria for study patients were well defined but were not strict as to age, medical status, or available bone. Therefore, it could be argued that the DICRG studies are more representative of a study of effectiveness (performance under normal conditions with a variety of dentists and patients) than efficacy. By viewing study data on success rates related to factors such as experience, adherence to study proto col, and patient selection, an approximate evaluation of efficacy could be conducted. This would involve a restricted analysis of data from study sites in which ideal study conditions were more closely approxi mated, surgeons had higher levels of experience and skill, and patients were more carefully selected to max imize the probability of implant treatment success. Alternatively, evaluating results that include sites with varied study conditions, treatment providers, and