Chapter
3
Background of Mini Dental Implants BURTON E. BALKIN
Outline The Early Historical Perspective: Sendax, Balkin, and Ricciardi History Description of Histologic Preparation
The Early Historical Perspective: Sendax, Balkin, and Ricciardi History Dental implants date back to the ancient Egyptian and South American civilizations. Recorded progress commenced in the 1880s and progressed into the 1900s, and the Harvard and National Institute of Health’s consensus development conference on dental implants indicated acceptance as a mode of treatment in 1988.1 In 1970-80 BrĂĽnemark and associates advocated an extended, soft-tissue covered healing period after implant insertion to allow for what came to be termed osseointegration and maintained in an unloaded environment for optimum predictability.2,3 In the 1980s implantologists gradually saw a need to try to accommodate the desire of patients for more immediate implant support. Thus narrow-Âdiameter mini dental implants came into use initially as a provisional treatment during healing/integration periods of traditional endosteal root-form implants. However, during this period, while utilizing mini dental implants for provisionalization, it was noted
Methods and Materials (Subtraction Radiography) Subjects and Dental Implants Digital Subtraction Radiographic Analysis Results (Subtraction Radiography) Early Clinical Applications Conclusion
that these immediately loaded mini implants were often difficult to remove and appeared to have become clinically integrated. This led to an ongoing development of applications and to the current use for long-term restorative cases. The initial concept was developed and tested by Dr. Victor Sendax with further development of use, trials, and applications by co-investigators Dr. Burton Balkin (Professor of Periodontology and Oral Implantology, Temple University School of Dentistry) and Dr. Anthony Ricciardi (New Jersey College of Medicine and Dentistry). Dr. Balkin demonstrated bone stability with mini implants inserted via the auto-advance technique and immediately loaded. Supportive information was obtained from a human histologic study and a human subtraction radiography study. The Sendax insertion protocol included preparing a minimal receptor site for a 1.8-mm implant by drilling directly through the attached gingiva into the bone for the part of the length of the implant portion that would be inserted but without the classic osteotomy that removed substantial bone to provide premeasured space for stabilizing traditional implants. The mini implant would then be turned
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Background of Mini Dental Implants
FIGURE 3-1. Example of 1.8-mm titanium alloy implant. and threaded into the bone with pressure from finger and thumb drivers until the threads were fully inserted. The auto-advance technique was a modification initiated by Balkin and colleagues4 to enhance immediate implant stability for both ongoing and long-term applications and to refresh the well-used self-tapping concept with a newly dynamic image of the narrow-width mini implant feeling drawn into the bone automatically during guided insertion. The technique used only a minimal starting point opening in bone, and then the 1.8-mm implant was inserted by turning into the bone without a deeply drilled receptor site. This insertion was performed by using either an ultra-slow high-torque machine driver and/or hand drivers (Figures 3-1, 3-2). Cases were immediately loaded and anecdotal evidence indicated a more predictably stable result with the auto-advance insertion technique in accommodating bone of varied trabeculation and density (Box 3-1). Very dense Type 1 bone and extremely osteoporotic Type 4 bone required limited compensatory deviation from this basic underlying process. To further test the validity of the clinical protocol, the mini implant system was subjected to histologic and radiographic scrutiny in two studies: 1. Histological specimens of minis were obtained by Dr. Balkin at 4 to 6 months after insertion and placement into immediate function while other traditional root-form implants integrated. Mini implants that supported the transitional prostheses were removed by trephination. The
FIGURE 3-2. Instrumentation for auto-advance technique insertion of mini dental implant.
BOX 3-1
M ini Dental Implant Insertion with Auto-advance Technique
• Starting point in bone • Auto-advancing into position without preparation of a receptor site • Ultra low-speed machine driver • Hand driver specimens were prepared and read by histologist David Steflik, M.S., EdD. Results indicated osteointegration to the surface of the implants based upon close adaptation of bone to the surface of the implants without interposition of soft tissue. This information was published in The Journal of Oral Implantology in 2001 and was the first human histologic report on the autoadvance insertion technique with immediate loading of mini dental implants, demonstrating feasibility for ongoing applications.4
Description of Histologic Preparation Two mini dental implants were fixed in 10% neutral buffered formalin for at least 72 hours. The samples were dehydrated in ascending concentrations of ethenol (50%, 75%, 90%, and 100% twice). Samples were transferred through acetone and infiltrated with methacrylate. Initially samples were immersed into a 50/50 mixture of methyl methacrylate, and samples were immersed into a 50/50 mixture of methyl methacrylate monomer and acetone for 24 hours, followed by 100% methacrylate monomer for 24 hours. The samples were
The Early Historical Perspective: Sendax, Balkin, and Ricciardi
FIGURE 3-3. Core of bone interposed between the implant and the drill bit. (From Balkin BE, Stefik DE, Navel F: Mini dental implant insertion with the AutoAdvance Technique for ongoing applications. J Oral Implantol 27:32, 2001) then vacuumed and infiltrated with methacrylate at room temperature for 14 days. Thereafter, they were placed in a vacuum oven, as per our previous report. As embedded blocks, they were then sectioned on an Isomet low-speed saw (Buehler Ltd., Lake Bluff, Ill.). The low-speed saw was affixed with a diamond wafering blade. Sections were cut in serial cross sections at thicknesses of 150 UM if necessary. They were ground to 80 UM if there were irregularities in the surface texture. The sections were stained with warmed toluidine blue and basic fuchsin, cover slipped, and viewed with a Zeiss Axiophat photomicroscope (Carl Zeiss Microscopy, LLC, Thornwood, N.Y.). Images were taken at various magnifications using Nomarski deferential interference imagery or polarized microscopy and routine light microscopy.
Results Two implant samples were prepared. The samples were cut in situ with a trephine over the implant and bone. In one sample the trephine remained fixed over the implant and bone, and the bone and implant were unable to be retrieved from the trephine. Figure 3-3 shows a core of bone interposed between the implant and the trephine drill bit, which prohibits the trephine drill from being removed. The osseous core consisted of cortical bone with osteonal bone apparent. In the second sample, the trephine was able to be removed from the bone and implant. The low magnification photomicrograph (Figure 3-4) depicts close bone congruency
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FIGURE 3-4. Low magnification photo micrograph shows close bone congruency to the implant surface. (From Balkin BE, Stefik DE, Navel F: Mini dental implant insertion with the Auto-Advance Technique for ongoing applications. J Oral Implantol 27:32, 2001)
FIGURE 3-5. Bone apparent with microscopy. (From Balkin BE, Stefik Mini dental implant insertion with the Technique for ongoing applications. J 27:32, 2001)
routine light DE, Navel F: Auto-Advance Oral Implantol
to the implant surface. Bone is clearly apparent with both routine light microscopy (Figure 3-5) as well as corresponding Nomarski differential interference, microscopy (see Figure 3-4), which showed the morphology of the osteone bone. Higher magnification of the similar area (Figure 3-6) demonstrated the osseointegration of the implant with osteonal bone directly interfacing the implant. The interstitial lamella, as well as the corresponding circumferential lamellae of the remodeled bone, is apparent.
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Background of Mini Dental Implants
FIGURE 3-6. Integration of the implant with osteonal bone. (From Balkin BE, Stefik DE, Navel F: Mini dental implant insertion with the Auto-Advance Technique for ongoing applications. J Oral Implantol 27:32, 2001)
FIGURE 3-8. Osteocytes revealed within their lacunae. (From Balkin BE, Stefik DE, Navel F: Mini dental implant insertion with the Auto-Advance Technique for ongoing applications. J Oral Implantol 27:32, 2001)
FIGURE 3-7. Demonstration of the concentric lamellae of the formed osteon and interstitial lamellae. (From Balkin BE, Stefik DE, Navel F: Mini dental implant insertion with the Auto-Advance Technique for ongoing applications. J Oral Implantol 27:32, 2001)
FIGURE 3-9. Mini implant inserted as transitional support during integration of cylindrical implants #27, #28.
Higher magnification (Figure 3-7) of the same area clearly shows the concentrical lamellae of the formed osteon and the interstitial lamellae. Such an image suggests the intimate association of the remodeled bone to the implant and the osseointegration of the implant. Higher magnification (Figure 3-8) shows osteocytes within their lacunae. This remodeled bone is closely placed to the implant surface. Vascular elements within this remodeled bone are apparent (Figure 3-9), providing the
nutritional requirements for the healthy-appearing remodeled bone interfacing this dental implant.4 2. Based upon the observations that mini dental implants may function better and longer than originally anticipated, in 2004 a pilot study examined the outcomes with digital subtraction radiography of human mini dental implants subjected to long-term fixed prosthetic function at least 3 years after their immediate loading after surgical placement.6
Methods and Materials (Subtraction Radiography)
Methods and Materials (Subtraction Radiography) Subjects and Dental Implants In three systemically-healthy adults requiring multiple tooth replacement, a total of 14 mini titanium screw dental implants were surgically inserted with an auto-advance technique,4 and then immediately loaded with fixed prosthetic bridges and followed for at least 3 years after treatment.
Digital Subtraction Radiographic Analysis Conventional periapical radiographs were taken of each of the 14 mini dental implants at the time of surgical placement, and at least three years after treatment, providing 14 serial radiographic pairs for digital subtraction analysis. Changes in crestal alveolar bone mass between the serial radiographic pairs were assessed using a United States Federal Drug Administration (FDA) approved, computerassisted, digital subtraction radiography program (DSRTM, Electro Medical Systems, Richardson, Tex.), which compensated for geometric projection and film contrast differences between the pairs of radiographic images before the subtraction. A board-certified oral and maxillofacial radiologist independently scored the computer-generated 足digital subtraction images at 27 proximal surfaces on the 14 mini dental implants as either exhibiting a gain (indicated by the appearance of a white color in the area of interest), no change (seen as a gray color-
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ation), or a loss (black color) in crestal alveolar bone mass over the 3-year period subsequent to immediate fixed prosthetic loading and function on the mini dental implants.
Results (Subtraction Radiography) None of the 14 mini implants were lost over the 3-year observation period. Of the 27 proximal implant surfaces examined with digital subtraction 足radiography, 8 (29.6%) mini implant surfaces exhibited a gain in crestal alveolar bone mass, 18 (66.7%) showed no change, and 1 (3.7%) surface revealed a loss in crestal alveolar bone mass. Representative digital subtraction images are presented in Figures 3-10 to 3-16.
Conclusions (subtraction radiography) This pilot study demonstrates that human mini dental implants subjected to immediate fixed prosthetic loading and function for at least 3 years survived and exhibited a remarkably high degree of stability in crestal bone mass, as indicated by the occurrence of only one of 27 viewed proximal surfaces exhibiting a loss in crestal alveolar bone mass as seen with digital subtraction radiographic analysis. Further research with larger patient sample sizes is indicated to additionally assess the capability of mini dental implants to successfully anchor fixed bridge restorations over extended periods after their surgical placement and immediate prosthetic loading.
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Background of Mini Dental Implants
A Baseline
3-years follow up
Subtraction image
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J FIGURE 3-10.  Subject D01, sites 24-26
Methods and Materials (Subtraction Radiography)
A Baseline
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Subtraction image
3-years follow up
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FIGURE 3-11.  Subject D01, sites 27-30
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Background of Mini Dental Implants
A Subtraction image
3-years follow up
Baseline
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C FIGURE 3-12.  Subject D01, site 19
Methods and Materials (Subtraction Radiography)
A Baseline
Subtraction image
3-years follow up
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C FIGURE 3-13.  Subject D02, site 5
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Background of Mini Dental Implants
A Baseline
Subtraction image
3-years follow up
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B
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FIGURE 3-14.  Subject D03, site 12
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Methods and Materials (Subtraction Radiography)
A Baseline
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Subtraction image
3-years follow up
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D FIGURE 3-15.  Subject D03, sites 14-15
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Background of Mini Dental Implants
A Baseline
Subtraction image
3-years follow up
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FIGURE 3-16.  Subject D03, site 10
Early Clinical Applications
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Early Clinical Applications Initial use was for support/stabilization of fixed temporization (see Figure 3-9 and Figure 3-17). This was followed by support/stabilization of removable prosthesis (Figure 3-18). Uses in ongoing and longterm applications (Figures 3-19 to 3-21) followed as experience and information accrued. Subsequent development by Bulard, Sendax, and Hadwin of the O-ball abutment allowed for O-ring attachment of a removable prosthesis to the mini implants, while also being partially tissue-supported (Figures 3-22 to 3-26). Use of mini implants rather than traditional implants could be considered in cases of: • Compromised health with minimal surgery and trauma, • Minimal bone where grafting or bone regeneration is considered contraindicated, • Desired immediate loading and function, • Minimal financial resources. Highlights include reduced chair time, simplified conventional restorations, and reduced cost to both patient and doctor.
FIGURE 3-18. Implant supported ongoing fixed prosthesis of reinforced processed acrylic for an elderly patient with compromised health.
FIGURE 3-19. O-ball mini implants for mandibular overdenture.
FIGURE 3-17. Transitional implant removed and abutments inserted.
FIGURE 3-20. O-ring retention for mandibular overdenture.
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Background of Mini Dental Implants
FIGURE 3-21. Edentulous maxilla, before operation.
FIGURE 3-22. Insertion of mini implant with machine driver.
FIGURE 3-24. Maxillary implants for overdenture without palate and with O-ball abutment heads for O-ring retainers.
FIGURE 3-25. Maxillary overdenture without palate with multiple O-ring retainers.
FIGURE 3-23. Maxillary implant overdenture. FIGURE 3-26. Postoperative with prosthesis insertion.
Conclusion
Conclusion Early findings of case reports, including histology and subtraction radiography, suggest the successful utilization of an auto-advancing threaded implant of titanium 6Al 4V alloy5 with adequate strength to penetrate the bone without a fully prepared receptor site while at the same time using a minimum diameter to avoid fracture of surrounding bone. Such a construct with auto advance insertion may also diminish implant fractures and provide a stable mini dental implant which when placed in adequate numbers for stress distribution and with immediate loading in mature bone may indeed provide interim transitional support, ongoing applications, and ultimately long-term use. Histology demonstrates healthy integrated bone in the areas of concern immediately surrounding the mini dental implants 4 to 5 months postoperatively. Subtraction radiography of cases with mini dental implants in immediate function demonstrates bone integration around the implants, including regeneration of previous intraosseous and soft tissue defects after a 3 year elapsed time period. This information, plus markedly expanded use of mini dental implants in the years since the early review was completed, indicates that the potential use of mini dental implants, using the auto-advance technique protocol, can provide immediate loading with integration for transitional use, ongoing applications, and long-term use. Further comparison studies with other implant designs and techniques in similar circumstances are indicated and to be encouraged. Thus mini dental implants have demonstrated an additional venue in dental implant treatment within the context of adequate knowledge, skill, and experience.
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References
1. Balkin BE: Implant dentistry: historical overview with current perspective, J Dent Educ 52:683, 1988. (NIH Consensus Development Conference on Oral Implants). 2. Adell R, Lekholm U, Rockler B, Br책nemark PI: A 15year study of osseointegrated implants in the treatment of the edentulous jaw, Int J Oral Surg 10:387, 1981. 3. Br책nemark PI: Osseointegration and its experimental background, J Prosthet Dent 50:399, 1983. 4. Balkin BE, Steflik DE, Navel F: Mini-dental implant insertion with the auto-advance technique for ongoing applications, J Oral Implantol 27:32, 2001. 5. McCracken M: Dental implant materials: commercially pure titanium and titanium alloys, J Prosthodont 8:40, 1999. 6. Balkin BE, Diaz JH, Yang J, Rams TE: Mini dental implants in human long-term fixed prosthetic function, J Dent Res 84(Special Issue A):2081, 2005. [Abstract].