2
PRINCIPLES
OF
TOOTH PREPARATION
Veneer Preparation Design The veneer preparation design can be influenced by tooth size, location and orientation in the arch, dental anatomy, occlusal function, mechanical forces, quantity and quality of remaining tooth structure, the parameters for extension of the preparation to the aesthetic zone, and the final anticipated restorative dimension.41, 46 Using these clinical considerations, modifications in the preparation design could be required to include the following designs: interproximal wraparound, incisal overlap, and intraenamel or window preparation. The primary consideration factors prior to veneer preparation of any tooth include: anatomic variations in enamel thickness according to tooth and location on the tooth and the final restorative dimension. Removing predetermined tooth dimensions (i.e., depth reduction guides) without consideration of these two factors can result in improper and extensive removal of tooth structure and postoperative sensitivity. A conservative intraenamel preparation should preserve as much of the natural enamel as possible. The facial reduction should be at two different angles so as to preserve the double convergence of the labial buccal surface. Axial reduction begins at the cervical region and the gingival margin should be prepared to a minimal (0.3 mm) chamfer and should be placed at or slightly above the level of the gingival crest unless caries, defects, or discoloration require a subgingival position. A conservative facial reduction should be 0.3-0.5 mm whereas, substrate discolorations may require increased reductions of 0.5 mm to 0.9 mm. All angles and corners should have smooth, rounded line angles, to improve resin adaptation,47 prevent stress concentrations in ceramic material and facilitate laboratory fabrication. Furthermore, healthy tooth structure should be removed only when the outline requires extension to a point beyond or within the previously indicated functional stops.44 66
Interproximal finish lines require different preparation designs depending upon the aesthetic requirement. These interproximal wraparound designs include the common and slice preparation. In the case of the common preparation, the reduction extends into the interproximal areas anterior to the contact zone whereas, the slice preparation continues through the interproximal region and onto the lingual surface. The slice preparation allows alteration in tooth width by rotating tooth contacts. The incisal overlap preparation can be used when the tooth requires lengthening or there is a incisal defect. If the incisal reduction is required, a chamfer or concave butt margin can be placed onto the lingual surface, but it is important to provide adequate space to maintain the strength of the ceramic material. This incisal overlap preparation design facilitates accurate seating of the veneer during cementation and improves the aesthetic quality of the incisal surface. When incisal reduction is not required, the window preparation is particularly useful. This intraenamel preparation design involves only the facial surface and preserves the functional incisal surface in enamel. This design reduces the potential for accelerated wear of the opposing dentition that can occur with the incisal overlap design.
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3
COMPOSITE RESINS
Glycerin was applied to the to the proximal surface of the maxillary lateral with un-waxed floss as a separating medium. (9) The first layer of the artificial dentin body, an opacious A-2 shaded hybrid composite resin (Aelite LS™, Bisco) was applied and contoured with a long-bladed interproximal instrument, The material is adapted, to the contra-lateral tooth and smoothed cervico-incisally with a #2 sable brush. The edge of the brush can be used to form the facial and the incisal embrasures. (10a - 10d) A second increment of hybrid composite resin (Aelite LS™, Bisco) was placed with an interproximal instrument to complete the internal dentin core. It is important to anticipate the final enamel dimension from the incisal aspect in order to prevent trespassing of the dentin core into the enamel zone.(11) A diluted white tint (Kolor + Plus, Kerr/Sybron) was applied with a #000 sable brush to highlight the lobes. (12) A diluted yellow tinted resin (Kolor + Plus, Kerr/Sybron) was applied to specific regions of the restoration with an 08 endodontic file (K-Flex, SybronEndo). To improve the chromatic integration, an untinted resin (Kolor + Plus, Kerr/Sybron) was used to dilute the yellow tint using light brush strokes to fade the chroma cervico-incisally. (13 - 14)
9
114
10a
10b
10c
11
12
13
10d
14
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3
COMPOSITE RESINS
The matrix is repositioned onto the anterior teeth and a lingual composite scaffold is developed onto the maxillary left central and light cured for 40 seconds. (9) The pre-selected translucent and opacious nanoparticle hybrid
9
composites are placed onto the scaffold and adapted with a long bladed interproximal instrument and smoothed using a #000 sable brush. Notice the incisal halo that is created and the nuances in the incisal one-third that can be developed by altering the opacious and translucent shades and their thickness. It is important to monitor the facial contour from the incisal so as to allow adequate space for the artificial enamel layer. (10a - 10e) The completed composite veneer on the maxillary left central illustrates a non-invasive adhesive
10a
procedure that can provide an optimal functional and aesthetic result. (11) A translucent shaded incisal hybrid composite (Premise™, Kerr/Sybron) is placed over the facial surface to encapsulate the dentin core. (12a -12b) Dentistry and photography courtesy of Tetsuji Aoshima, D.D.S.
10b
10c
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10d
10e 11
12a
12b
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4
CERAMIC MATERIALS
9
10
The platinum foil is cut into specified shape using
held above a cone-shaped bunsen burner, or a
a template designed for veneering techniques. The
vertical torch flame until the foil is bright orange.
platinum foil is placed over the labial surface with
This procedure decontaminates and anneals the foil to a dead soft state. (12) The annealed
the tab portion below the gingival margin and the excess foil is trimmed with scissors. (9 - 10) The
13
19
foil matrix allows support for the application,
platinum foil is folded over the labio-incisal edge
sculpting, and firing of the metal-free ceramic
and carefully burnished from its center toward the
substructure. An initial thin wash of dentin porce-
proximal corners using an orangewood stick to secure the foil to the die. (11)
lain was applied to the surface of the foil matrix and baked. (13 - 14)
A foil labial ridge was creased using the straight,
A equal mixture of dentin powder and opacious
pointed-tip tweezers. Any excess foil beyond the
dentin powder (i.e., 50/50) was applied to build
mesial and distal margins and the lingual-incisal
up the fractured tooth. This layering process elimi-
edge should be cut using a scalpel blade (#11
nates the demarcation of the fracture line of the
BD Bard-Parker™, BD Medical). The foil was then
tooth structure while minimizing the diastema. The
14
20
15
21
11
ceramic shrinkage after firing in porcelain furnace. The temperature is altered 5ยบ C to prevent over firing of the ceramic material since multiple firings are required. (15 - 16)
12
of colors in the incisal edge from the scattering of light. (20) An application of MI61 between the dentin and enamel walls is used to create a mamelon
Utilizing the same mixture of dentin and opacious
effect while Illusion is applied to enhance the depth of translucency. (21- 22)
powder (i.e., 50/50) the proximal contours are developed while minimizing the diastema. (17) The
A white crack line was placed next to the mamelon to emphasize the effect by contrast. (23) After the
dentin was built to final shape and contour, then cut
internal stains were completed, the entire facial surface
back to provide space for the incisal application. (18) The enamel incisal 58 was applied to the
is covered with a combination of translucent and
mesial and distal to develop the proximal enamel walls. (19) A segmental buildup with incisal and
enamel. Layering different colors of enamel on the
clear powders (i.e., 50/50) is applied in the incisal
opalescent powders designed to simulate shaded facial aspect creates an illusion of depth by contrasting light-dark and medium layers. (24)
region. Altering the incisal powders creates nuances
16
17
18
22
23
24
4
CERAMIC MATERIALS
72 - 75
The provisional restoration preserves the position, form, and color of the gingiva and maintains the periodontal health while the definitive restoration is being fabricated. At the try-in visit the provisional restorations can be removed using a crown removing instrument (GC Pliers, GC America速) with an emery powder. It is important to dry the provisional before applying the powder. A properly contoured and sealed provisional allows the development of a healthy soft tissue framework. (72 - 75)
240
76 - 77
The porcelain restorations were tried in and evaluated and modifications were completed prior to beginning the adhesive process. To prevent contamination during the adhesive procedure, a 3-0 silk cord (3-0 Silk Suture, Ethicon) is gently placed in the sulcus using a bimanual technique. This silk cord seals the sulcus and prevents contamination of the preparation from blood or crevicular fluid during the adhesive protocol. (76 - 77) The internal surface of the zirconium crowns are microetched with a tribochemical silica coating (Rocatec/CoJet System, 3M™ ESPE™) followed by an application of an MDP-containing bonding/silane coupling agent mixture (Porcelain Bond Activator mixed with Clearfil SE™ Bond Primer, Kuraray). The microetching of highly crystalline ceramics such as zirconium with a tribochemical silica coating creates binding sites for the silane molecules while the silane provides wettability and a chemical coupling with the methacrylate based cements. (78 - 79)
78 - 79
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5
ELASTOMERIC IMPRESSION MATERIALS
1
2
Double Cord Gingival Displacement Technique The anterior teeth are prepared for all-ceramic crowns using a silicone index as a preparation guide. (1) The exact dimensions of the gingival complex are verified by means of a periodontal probe to confirm the depth of the gingival sulcus. (2) A primary compression cord of small diameter (#000 Ultrapak, Ultradent Products® Inc.) is soaked in a plain buffered aluminum chloride (Hemodent™, Premier Dental®) and gently placed in the bottom of the sulcus around the preparations with light pressure from a cord packing instrument (Fischer’s Ultrapak #170,Ultradent Products® Inc.). (3) The apical migration of the free gingival margin allows the initial finish line of the preparation to be exposed. (4)
270
3
4
6
CONTEMPORARY ADHESIVE CEMENTS
CONTEMPORARY ADHESIVE CEMENTS Contributing Authors: douglas A. Terry, D.D.S., Markus B. Blatz, D.M.D., Ph.D.
Adhesive cementation involves cement adaptation to surface irregularities in a manner that prevents the restoration’s dislodgement. The primary objective of each cementation procedure is to achieve a durable bond and a good marginal adaptation of the luting material to the restoration and the tooth.1 Successful cementation of the luting material to both is essential for retention,2, 3 clinical performance, and longevity of indirect restorations.4 The search continues for the ideal luting cement. Such a material should preserve and stabilize tooth hard tissues, provide a durable bond between dissimilar materials, possess high compressive and tensile strengths, adhere to tooth structure and restorative materials, and possess anticariogenicity by preventing caries at the restoration-tooth interface. It should be biocompatible with pulpal tissue, possesses antimicrobial properties, provide resistance to microleakage, ease of manipulation with increased working and setting time, low film thickness, low solubility, high proportional limit, translucency, and radiopacity. In addition, this material should possess increased fracture toughness to prevent dislodgement as a result of interfacial or cohesive failures, exhibit low contact angle as a measure of optimum wettability, provide adequate viscosity to ensure complete seating, and exhibit aesthetics compatible with the selected restorative material.5-7 During the last century, the quest for an ideal luting cement has been influenced by other variables. These variables include more conservative tooth preparation designs, improved mechanical properties of ceramic and resin-based materials, various tooth and biomaterial surface conditioning, advanced formulations of adhesive systems, and numerous diverse adhesive techniques and luting procedures.8 A historical review of the progression of luting cements may provide insight into future selection and application with different biomaterials. 278
Historical Progression of Luting Cements During the Pre-Adhesive era, cementation of restorations was dependent upon the restorative principles of resistance and retention form achieved from the preparation geometry and the fitting surface of the casting. Introduced to the profession in 1879,9 zinc phosphate cement has been the most widely used luting cement in the 20th century and has been accepted as the “gold standard� for cast restorations.10 However, a few of the challenges of these water-based cements included increased clinical solubility,6 sensitivity from initial low pH, and lack of anticariogenic effect5 to prevent caries at the restoration-tooth interface. The late sixties sparked the evolution of the Adhesive Era, with a major breakthrough in the development of polycarboxylate cements. These cements were developed to improve the original challenge of pulpal biocompatibility from the low pH of zinc phosphate cement.11 In addition, these materials demonstrated chemical adhesion to tooth structure between their negatively charged carboxylic groups and calcium phosphate cations, while providing lower compressive strengths (55 to 85 MPa) and higher tensile strengths (8 to 12 MPa). The seventies brought significant improvement to the challenges of the traditional cements with the introduction of the glass-ionomer cements. These bioactive materials provided improved physico-chemical adhesion to tooth structure and to non-precious metal alloys,10 higher compressive strengths than polycarboxylate and zinc phosphate cements, fluoride ion release with potential for remineralization, a low coefficient of thermal expansion, and improved resistance to dissolution. The popularity in aesthetic indirect restorations of the mid-eighties launched the increased use of composite resin cements. These luting agents offered the clinician better options for shade matching, higher compressive and tensile strengths, while enhancing the fracture resistance of ceramic materials that can be etched and silanated.6, 12 However, these cements still exhibit the potential for secondary caries and have been associated with a higher level of postoperative sensitivity. Furthermore, some of the adhesive cements require clinical procedures that are more complicated. Resin-ionomer cements debuted in the early nineties with advanced physical and mechanical properties. These cements provided solutions to the challenges of all their predecessors by providing fluoride release10 and cariostatic potential and resistance to marginal microleakage.7 They were also characterized by an improved adhesion to enamel and dentin, enhanced fracture resistance and wear characteristics. In addition, these materials exhibited more resistance to moisture and were less soluble than conventional glass-ionomer cements,7 improved setting characteristics, lower resistance to permanent deformation, a command of working time (photo-curing), lower film thickness,7 improved aesthetics, and ease of manipulation. However, these cements were contraindicated for cementing all-ceramic restorations and posts due to their volumetric expansion that leads to dimensional change and post-cementation expansion of the restoration or root fracture.5
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7
PROVISIONALIZATION
Laboratory Fabrication of a Composite Resin Bridge
Facial view of the completed diagnostic wax-up (Master Diagnostic Model®, Valley Dental Arts Laboratory). Occlusal view of the completed diagnostic wax-up (Master Diagnostic Model®, Valley Dental Arts Laboratory). (1 - 2) A mixture of soap and water is poured into a container. (3) Diagnostic wax-up is soaked in soapy mixture for 10 minutes. (4) An equal volume of silicone catalyst and base (PolyPour™, GC America®) is mixed thoroughly into an homogenous liquid. (5 - 6) The diagnostic wax-up is duplicated by making a silicone investment. (7)
1
2
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3
4
5
6
331 7
8
AESTHETIC POST SYSTEMS
Developing a Ferrule Effect Dislodgement and tooth fracture are causes for failure of post-and-core restorations. Core stability and post retention are important in preventing these failures in the restoration of endodontically treated teeth. The ideal post system should replace lost tooth structure while providing adequate retention and support to the core, allowing retention of the restoration while transferring occlusal forces during function and parafunction to prevent root fracture. The stability of the crown is influenced by the preparation design for endodontically treated teeth. Preserving tooth structure during preparation is paramount in preventing stress concentations
386
at the cemento-enamel junction of the endodontically restored tooth and provides resistance to tooth fracture. The completed crown preparation should have a ferrule design that encapsulates the endodontically restored tooth complex. This collar effect provides an antirotational feature for the stability of the crown. Clinical studies have demonstrated and confirmed the importance of this coronal tooth “collar� on the mechanical resistance and retention form of the endodontically restored tooth complex.42 The general guideline is a 1 to 2 mm preparation on sound tooth structure. Procedures that provide a shoulder on tooth structure and an axial preparation on the core bulid-up will have an insufficient ferrule design. In cases where there is insufficient sound tooth structure for this ferrule design it is necessary to obtain this dimension through periodontal crown lengthening and/or forced tooth eruption procedures. Dentistry and photography courtesy of Alejandro James, D.D.S., M.S.D.
387
9
MECHANISMS
OF
ADHESION
2
1
Total-Etch Technique Rebonding the Fractured Porcelain Veneer
Preoperative facial view of fractured porcelain veneer on a maxillary left central incisor. (1) The internal surface of the fractured porcelain restoration was micro-etched with silica coated aluminum oxide particles (Rocatec/CoJet System, 3M™ ESPE™). (2) The fractured fragment was etched for 2 minutes with a 9% buffered hydrofluoric acid gel (Porcelain Etch, Ultradent Products® Inc.). (3) Application of an MDP-containing bonding/silane coupling agent mixture (Porcelain Bond Activator mixed with Clearfil SE™ Bond Primer, Kuraray). (4) The fractured ceramic surface of the intact veneer was etched with 9% buffered hydrofluoric acid gel (Porcelain Etch, Ultradent Products® Inc.). (5) The exposed tooth preparation was etched for 15 seconds with a 37.5% phosphoric acid (Gel Etchant, Kerr/Sybron). (6)
430
4
3
5
6
10
FINISHING & POLISHING
1
2
Finishing and Polishing Anterior Ceramic Restorations: Gingival Regions After bonding the porcelain veneers, any excess polymerized resin cement can be removed from the interface using a scalpel blade (#12 BD Bard-Parker™, BD Medical). (1) Any modifications or adjustments to the gingival surface of the porcelain can be made using a 15 !m short, tapered, diamond (DET-3, Brasseler USA®) by retracting the gingiva with an 8A instrument (TNPFIA6, Hu-Friedy®), while closely observing tooth structure and the gingival margin area, and finishing margins with gentle sweeps. (2) The gingival region of the porcelain veneer can be smoothed and polished with pre-polish and high shine silicone abrasive hollow cups (DC3M, DC3, Brasseler USA®) and silicone abrasive points. (3a - 3b) A properly polished ceramic veneer allows an optimal bio-integration of ceramic material with soft tissue. (4)
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3a
3b
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FINISHING & POLISHING
References and Suggested Readings
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20. Boghosian AA, Randolph RG, Jekkals VJ. Rotary instru-
2. Stewart GP, Bachman TA, Hatton JF. Temperature rise
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due to finishing of direct restorative materials. Am J Dent. 1991;4(1):23–28.
21. Reis AF, Giannini M, Lovadino JR, Ambrosano GM. Effects
3. Cooley RL, Barkmeier WW, White JH. Heat generation
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during polishing of restorations. Quintessence Int Dent Dig. 1978;9(12):77–80.
4. Bollen CM, Lambrechts P, Quirynen M. Comparison of surface roughness of oral hard materials to the threshold surface roughness for bacterial plaque retention: a review of the literature. Dent Mater. 1997;13(4):258–269.
5. Kaplan BA, Goldstein GR, Vijayaraghavan TV, Nelson IK. The effect of three polishing systems on the surface roughness of four hybrid composites: a profilometric and scanning electron microscopy study. J Proshet Dent. 1996;76(1):34–38.
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23. Dietschi D, Campanile G, Holz J, Meyer JM. Comparison of the color stability of ten new-generation composites: an in vitro study. Dent Mater. 1994;10(6):353–362.
24. Christensen RP, Christensen GJ. Comparison of instruments and commercial pastes used for finishing and polishing composite resin. Gen Dent. 1981;29(1):40–45.
6. Berastegui E, Canalda C, Brau E, Miquel C. Surface
25. Duke ES. Finishing and polishing techniques for composite
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10. Summitt JB, Robbins JW, Hilton TJ, Schwartz RS. Finishing
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12. Yap AU, Sau CW, Lye KW. Effects of finishing/polishing
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32. Judd DB, Harrison WN, Sweo BJ, Hickson EF, et al.
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44. Grundy JR. Finishing posterior composites. An SEM study of a range of instruments and their effect on a composite and enamel. Restorat Dent. 1985;1(6):48–58.
45. Terry DA. Natural Esthetic with composite resins. 1st ed. Mahwah, NJ: Montage Media Corp; 2004
46. Quiroz L, Lentz DL. The effect of polishing procedures on light-cured composite restorations. Compend Contin Educ Dent. 1985;6(6):437–439.
47. Anusavice KJ ed. Phillips’ science of dental materials. 10th ed. Philadelphia, PA: WB Sanders; 1996.
48. Magne P, Oh WS, Pintado MR, DeLong R. Wear of enamel and veneering ceramics after laboratory and chairside finishing procedures. J Prosthet Dent. 1999;82(6):669–679.
49. Sulik WD, Plekavich EJ. Surface finishing of dental porcelain. J Prosthet Dent. 1981;46(2):217–221.
50. Monasky GE, Taylor DF. Studies on the wear of porcelain, enamel, and gold. J Prosthet Dent. 1971;25(3):299–306.
51. Wiley MG. Effects of porcelain on occluding surfaces of restored teeth. J Prosthet Dent. 1989;61(2):133–137.
52. Jefferies SR, Barkmeier WW, Gwinnett AJ. Three composite finishing systems: a multisite in vitro evaluation. J Esthet Dent. 1992;4(6):181–185.
53. Clayton JA, Green E. Roughness of pontic materials and dental plaque. J Prosthet Dent. 1970;23(4):407–411.
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DENTAL PHOTOGRAPHY
Clinical Photographic Techniques Clinical photography is an essential component in aesthetic and restorative dentistry. It has become paramount to our security and indispensable in communication.28, 42 Intra-oral photographs allow the pre-existing condition to be evaluated, diagnosed, documented, and described to the patient. The aesthetic examination is not complete without photographs. In fact, the diagnosis is often discovered as the photographic series is taken and reviewed. Restorative treatment should not be initiated prior to completion of a preoperative series of photographic images since they are not only a diagnostic tool but provide legal support for any treatment provided. In addition, by reviewing postoperative photographs the restorative team (i.e., technician, clinician) can evaluate the outcomes and learn from positive as well as negative results. There is a myriad of photographic tips and tricks that can improve the image capture. For example, one suggestion is to hold one’s breath as soon as an image is clear in the viewfinder just prior to releasing the shutter. To stabilize the camera the photographer can stand slightly astride with one foot forward and lean against the dental chair. The weight of the camera seems manageable by supporting the weight with the palm underneath the camera body while bracing the elbow against the body. Another method of stabilizing the camera is to extend a finger to use as a brace against the patient’s face or tooth. Taking the portrait at the end of the series helps the patient to be at ease and comfortable for the most natural and relaxed smiles. The authors’ 16-image photographic series will describe the magnification ratio, patient orientation, photographic composition, position of camera angle, and flash position for each of these intra-oral and extra-oral views.
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DENTAL PHOTOGRAPHY
Maxillary or Mandibular Anterior Incisors Retracted Frontal View (Intra-Oral View) Magnification Ratio – Equivalent of full frame 1:1. This magnifications should display a horizontal format and reveal the maxillary or the mandibular anterior teeth and gingiva. This view should show 4-6 of the maxillary teeth and 6-8 of the mandibular teeth. The retractors should be pulled as firmly as possible so as not to display the retractors in the composition. Patient Orientation – The patient is seated in an upright position with head supported in the headrest. The head should be perpendicular to the floor while the shoulders are parallel to the floor. The chin should be slightly depressed so the occlusal plane is parallel to the floor. The patient’s mouth should be positioned so that the opposing arch is not evident. The retractors should be pulled as firmly as possible so as not to display the retractors in the composition. Photographic Composition – This view should display the maxillary or the mandibular anterior teeth and gingiva in the center of the frame. The central incisors should be in the middle of the slide and should reveal 4-6 of the maxillary teeth and/or 6-8 of the mandibular teeth. To proportion the anterior segment, the tip of the papillae between the central incisors should be centered vertically. It is important not to display the opposing arch or the retractors. Position of Camera Angle – The camera should be positioned to create a horizontal image and the lens should be perpendicular to the patient’s face. The photographer should position in front of the patient. The body of the camera should be parallel to the horizon. Flash Position – If a point flash is used, it should be positioned at one o’clock.
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PERIODONTAL PLASTIC SURGERY
Photograph and Copyright by Irfan Ahmad, B.D.S.
PERIODONTAL PLASTIC SURGERY Contributing Authors: douglas A. Terry, D.D.S., Ernesto A. Lee, D.M.D., Dr., Cir., Dent., David A. Garber, D.M.D., Alejandro James, D.D.S., M.S.D., Susana B. Paoloski, D.D.S.
The aesthetic restoration of anterior teeth frequently requires the correction of inadequate anatomical dimensions and proportions. The achievement of tooth forms that are dentofacially harmonious is often dependent on the ability to surgically modify gingival architecture. The biological principles that guide the responses of the soft and hard tissues have been the subject of increased research as patients present for the treatment of many dental and dentofacial abnormalities. An understanding of these principles allows for the development of ideal relationships between periodontal and dental structures that can provide optimal biologic and aesthetic results. By integrating surgical periodontal plastic surgery procedures with contemporary restorative therapy, it is not only possible but predictable to develop a biologically stable dentogingival interface.1-4 Periodontal plastic surgery procedures include clinical crown lengthening,5-10 subepithelial connective tissue grafting for root coverage,11-13 and hard and soft tissue ridge augmentation.14-16
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Crown Lengthening Procedures Crown lengthening procedures have become an integral component of the aesthetic armamentarium and are utilized with increasing frequency to enhance the appearance of restorations placed within the aesthetic zone. Whether performed for the purposes of exposing sound tooth structure, or to enhance the appearance of the definitive restorations, these procedures must be planned following sound biologic principles, in order to avoid deleterious effects. The implementation of evidence-based diagnostic criteria, along with contemporary surgical and restorative protocols, may result in increased predictability and optimum results when treating the aesthetic zone. Clinical Indications and Anatomical Considerations Crown lengthening procedures have been traditionally performed to provide access for treatment of subgingival caries, fractures, or defective restorations. It is also recommended when there is inadequate tooth structure for crown retention as a result of excessive occlusal wear, abrasion, altered passive eruption, hyperplastic tissue, and asymmetrical ginginival margins.17 Its surgical objectives include the exposure of an area of sound tooth structure suitable for placement of a restorative margin, while providing adequate biologic width space.7, 18-20 Crown lengthening procedures may also be required for the treatment of chronic gingivitis caused by the placement of an otherwise satisfactory restoration exhibiting margins that impinge upon the biologic width.21,22 Additionally, crown lengthening procedures may be performed to enhance the appearance of restorations placed within the aesthetic zone. Regardless of the clinical indications, however, similar biological parameters must be taken into consideration and it is therefore essential to possess a basic knowledge of the anatomic structures involved.23 Independently of whether the rationale for crown lengthening surgery is guided by functional or aesthetic requirements, the biologic principles involved remain the same. The periodontium is the basic functional unit supporting the teeth. Its components include the alveolar bone, periodontal ligament, cementum, junctional epithelium, and gingiva.24 These tissues are interdependent and exist in a state of physiologic hemostasis, where normal cellular activity allows the maintenance of health and a defensive response to environmental insults. The gingiva is comprised primarily by connective tissue, which is covered by an epithelial layer that provides a protective barrier against bacterial, mechanical, and immunological insults. Collagen fibers within the gingival connective tissue insert into the periosteum of the alveolar process and into the root cementum.
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INTERDISCIPLINARY IMPLANTOLOGY
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Anterior Ridge Augmentation Anterior ridge deficiency or defects can result from the loss of teeth from disease, trauma, surgical injury, or developmental origin.138-140 The ideal form for fixed prosthesis pontics is described as having the occlusal height at the lingual half, an adequate zone of gingiva with a smooth regular surface which is free from aberrant muscle attachments, and an accommodating contour mesio-distally and facio-lingually. The aesthetics and function can be compromised in the maxillary anterior region when pontics or implants are adapted to deficient alveolar ridges.141,142 Reconstructive periodontal plastic surgery procedures, originally referred to as mucogingival surgery 143 allow the restoration of the hard and soft tissue profiles of the alveolar ridge to proper dimensions for the optimal functional and aesthetic result. There are various types of techniques to reconstruct deficient or defective alveolar ridges. The soft tissue mucogingival augmentation procedures available for these defects include the connective tissue pedicle grafts—the “Roll technique,”144,145 pouch graft139,144-147 interpositional (wedge and inlay) graft,139,144,145,147and the onlay graft.139,144-147 The amount of soft tissue, supporting alveolar bone, and available blood supply are factors that contribute to the stability and success of the reconstruction procedure.139 The selection of the proper treatment plan requires an understanding of the type of defect present, the extent of the defect, and the quantity of tissue or graft material.
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A soft tissue diagnostic wax-up is prepared to indicate the additional bucco-lingual dimension that is required for optimal biologic and aesthetic results. (10) The connective tissue graft was harvested from the palate using sharp dissection. The volume of connective tissue required was predetermined from the bucco-lingual wax-up dimension. A subepithelial/subconnective tissue graft procedure (pouch graft )was used to restore the bucco-lingual ridge defect (Class I148 or Class B149 defect). This procedure uses a wedge of connective tissue that is placed in a surgically created pouch that maintains a supraperiosteal blood supply to surround the graft. A matrix of the diagnostic wax-up is used to confirm the predetermined dimension. (11 - 14) A postsurgical review demonstrates an improved gingival architectural contour with an enhanced bucco-lingual alveolar ridge dimension. (15)
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INTERDISCIPLINARY IMPLANTOLOGY
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The socket is gently debrided using a surgical curette. (9) A surgical guide (Atlantis, Atlantis Components Inc.) was fabricated during the pretreatment phase to a predetermined orientation and depth and the custom abutment was fabricated, prior to the surgical procedure. A 2 mm disposable twist drill is precisely placed. Notice the precise alignment with surgical guide. (10) A 3.5 mm tapered drill is measured and placed 1mm beyond the actual length (13 mm) of the fixture apex. (11 - 12) The implant is transferred under sterile conditions and delivered to the prepared surgical site. Implant selection was based upon preoperative considerations (i.e., radiographic evaluation and diagnostic wax-up) and confirmed by the root measurement after extraction and post surgical assessment of the anatomical parameters. (13 - 14) The implant is placed 3 mm below the cementoenamel junction of the adjacent teeth using 30 N-cm torque. Notice the ideal position of the implant in relation to the adjacent teeth confirms the pre-planned position. (15 - 16)
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BIOMODIFICATION OF TOOTH DISCOLORATION
Reprinted from Theodore P. Croll, D.D.S.29 with permission
BIOMODIFICATION OF TOOTH DISCOLORATION Contributing Authors: douglas A. Terry, D.D.S., Cynthia P. Trajtenberg, D.D.S., M.S., Theodore P. Croll, D.D.S.
Alterations in tooth color can be due to a variety of causes. Some of these occur during tooth formation and others afterwards.1 There are three well defined groups. These include alterations due to external agents and those generated by intrinsic etiology. The third group includes heterogeneous alterations of color (i.e., enamel wear from aging darkens tooth color). It is important to identify the correct etiology for effective treatment.2
Extrinsic Origin Extrinsic stains are superficial discolorations of the tooth surface or restorative material resulting from an accumulation and adherence of foreign particles of various origins (i.e., tobacco, coffee, tea, medications such as iron supplements, chlorhexidine, chromogenic type bacterium, tannin in dietary supplements, etc.). Extrinsic stains can consist of multiple colors: brown, black, green, orange, grey metallic.3 Brown stains are thin, pigmented pellicles usually located on the buccal surfaces of maxillary molars, the lingual aspect of mandibular incisors and less frequently on maxillary incisors. The specific origin of the brown staining has not been determined but tannin depositions from tea and coffee are suspected.3 Dark brown to black stains are the result of tobacco usually located on the gingival third of teeth and on enamel defects.4 676
Green stains are found as wide bands on the facial aspect of maxillary incisors because the bacteria originating the stain develop in the presence of light. These stains are commonly found in children and more commonly affect females. This type of stain is originated by fluorescent bacteria or fungi such as the penicillum or aspergillus. Orange stains which Reprinted from Theodore P. Croll, D.D.S. with permission are not very common are due 3 to chromogenic bacterium. Chlorhexidine discolorations are typically brown and can stain teeth and composite restorations after prolonged use.5 29
Intrinsic Origin Intrinsic stains are caused by trauma to a developing permanent tooth. The trauma causes damage to the blood supply which results in degeneration of pulpal tissues and subsequently to loss of vitality. The blood pigments left behind infiltrate the dentinal tubules leading to significant tooth discoloration.6 Other forms of intrinsic staining include Reprinted from Theodore P. Croll, D.D.S. with permission tetracycline and fluorosis. Tetracycline staining occurs as a result of the tetracycline molecule becoming incorporated into the developing dentin causing a change in color of the dentin to a yellow, blue-grey or brown discoloration. The results depend upon the concentration administered to the patient and exposure of the tooth structures to ultraviolet light following eruption.7 Fluorosis presents as brown and white speckled mottling of the tooth and is due to the intake of excessive concentrations of fluoride during formation of the coronal aspect of the tooth.8 29
Other intrinsic staining is created by local, systemic, or genetic factors that result in hypoplasia or opacities or hypocalcification of the enamel. In the case of amelogenesis imperfecta the enamel presents itself as hypoplastic, hypocalcified, or hypomaturated.9 The staining ranges from opacious white to yellow.
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