COSMETIC AND ESTHETIC DENTISTRY |
USING A MODIFIED SUBOPAQUING TECHNIQUE TO TREAT
HIGHLY DISCOLORED DENTITION
WYNN H. OKUDA, D.M.D.
 |
ABSTRACT
|
|---|
Background. The objective of esthetic dentistry is to treat diverse problems and achieve natural-appearing results. The author reviews the issues involved in the discoloration of human dentition and the concerns associated with current treatment for this problem. Understanding the proper use of materials in esthetic dentistry can result in a conservative, natural-appearing restoration.
Overview. Dentition discoloration due to intrinsic staining can be a severe esthetic problem. Current treatment using crowns and highly opaque porcelain veneers has inherent disadvantages in regard to the final restorations. The author explores a subopaquing technique that allows for progressive lightening of highly stained teeth to create natural color depth in a conservative porcelain veneer procedure.
Clinical Implications. In treating dental problems, the clinical practitioner looks for solutions that conserve tooth structure. To achieve natural-appearing esthetic results, it is important for the practitioner to be aware of technological advances in materials science as well as the proper use of esthetic dental techniques. Understanding the problems associated with dental discoloration and ways of correcting them will allow the practitioner to solve these moderate-to-severe esthetic problems on a consistent basis.
Dental discoloration is an esthetic problem that manifests itself for a variety of reasons. First, the effects of tetracycline staining of the permanent dentition have been well-documented.1–3 Although the incidence of such staining has decreased, the problem still exists. Moreover, the use of minocycline hydrochloride has increased within the last decade. This medication, used to treat severe acne and rheumatoid arthritis, is capable of causing pigmentation in the adult dentition.1 These permanent stains can be a major source of embarrassment, leading to reduced self-esteem. To establish proper dental esthetics, the clinician must correctly apply dental materials using innovative techniques.
|
DISCOLORATION IN THE HUMAN DENTITION
|
|---|
Dentition discoloration, both extrinsic and intrinsic, can originate from a variety of sources.2,3 Extrinsic stains can create superficial discoloration along the clinical crown that can result from excessive iron supplementation, poor oral hygiene and accumulation of dental plaque.2 Intrinsic stains in the adult dentition are caused by a variety of factors. Pulpal trauma, congenital problems (for example, phenylketonuria, ochronosis), genetic abnormalities (for example, dentinogenesis imperfecta, amelogenesis imperfecta) and drug-induced stains (for example, tetracycline, minocycline, sulfur drugs) can cause irreversible pigmentation in the adult dentition in varying colors and degrees of chromacity. The modality of esthetic dental treatment depends on the severity of the color problem.3
For decades, severe intrinsic staining often has been treated with a crown. Although this has been moderately successful, the aggressive removal of tooth structure that is required is undesirable. With advancements in technology during the last decade, porcelain veneers have become a popular means of correcting these severe problems because of the conservative amount of tooth structure that needs to be removed. However, to mask highly chromatic intrinsic stains, opaque porcelain must be placed in the initial layer of the porcelain veneer to change the hue and increase the visual value (that is, brightness) of the teeth involved.
The opaque porcelain lining placed in the porcelain veneer does mask the intrinsic stain; however, the resulting esthetic effect is much worse than the natural appearance.4,5(p269) Just as with porcelain-fused-to-metal crowns, the opaque porcelain layer does not allow natural light to penetrate the underlying tooth structure. The result is improper illumination of the dentin and root structure.6 Proper reflection, refraction and absorption of light into the dentin are important to re-create natural esthetics in the human dentition. Although highly trained ceramic technicians are able to create natural color depth in a highly opaque veneer, it is unrealistic to expect that natural results will be achieved on a consistent basis (Figure 1
). Therefore, better techniques are needed to address this esthetic problem.
View larger version (74K):
[in this window]
[in a new window]
|
Figure 1. Previously bonded opaque porcelain veneers over highly discolored teeth exhibit minimal natural color. Notice the grayness along the middle third of the veneers.
| |
|
INFLUENCE OF TOOTH COLOR ON EXTERNAL VISUAL EFFECT
|
|---|
Two factors directly influence tooth color: dentin and enamel. Although enamel is colorless and does not contribute to the actual color, it does determine the ultimate value of the external tooth shade. Enamel acts as a fiberoptic structure that conveys light through its rods and into the underlying dentin.7 The primary source of tooth color is beneath the enamel layer. Thus, internal color contributes greatly to the depth and vitality of natural dentition. Whether the internal color is considered detrimental or not, it is an integral component and cannot be overlooked.8 Because light reflects, refracts and absorbs in different areas of the tooth, use of dental materials that mimic natural dentin to uniformly mask or subopaque tetracycline-stained dentition would create a more natural-appearing dentin color. When used appropriately, hybrid composite material along with a corresponding opaque composite system can create an optical view that is similar to that of natural dentin.9 By uniformly controlling the color along the restorative interface, the clinician can consistently achieve natural depth of color.
|
MATERIAL SELECTION FOR A MODIFIED SUBOPAQUE LAYER
|
|---|
The key to mimicking normal color and strength of dentin is proper material selection. Hybrid composite materials such as Renamel Hybrid (Cosmedent Inc.), Herculite XRV (SDS Kerr), Tetric Ceram (Ivoclar-Vivadent) and Vitalescence (Ultradent Products Inc.) provide the strength and opacity needed in an artificial dentin.10 This is because of the combination of inorganic filler type and particle size. Moreover, these contents in hybrid materials help to increase the overall bond strength to dentin as well as to other substrates such as porcelain.11
However, when sub-opaquing a highly discolored dentin, the clinician may find that a hybrid material alone does not fully mask the unesthetic color. For this reason, an opaque material is needed in esthetic dentistry. A comprehensive opaque system such as Creative Color (Cosmedent Inc.) or Kolor+/Opaker (SDS Kerr) gives the practitioner the ability to fully mask the offensive discoloration without achieving a result that is unnaturally bright. This procedure is indicated for healthy adult dentitions that have adequate inherent strength for porcelain veneers.
|
CLINICAL PROCEDURE FOR THE MODIFIED SUBOPAQUE LAYER
|
|---|
In treating highly chromatic intrinsic stains (for example, tetracycline stains) or re-treating these types of stains, the clinician must approach these problems systematically. The current subopaquing procedure involves the use of only an opaquer that is bonded onto the discolored area of the tooth preparation. However, this method brings up questions of bond strength and natural internal color. To maximize bond strength and internal color, practitioners can use a modified subopaquing procedure consisting of hybrid composite and opaquer placed in a "sandwich" technique. First, 0.7 millimeters of tooth structure must be removed uniformly along the facial, proximal and incisal areas of the enamel surface or the pre-existing veneers. This can be achieved with a 0.7-mm preparation guide (Nixon Preparation Kit II, Brasseler USA). For severely darkened teeth, this 0.7-mm thickness is needed for the ceramist to effectively increase the visual value and hue.12
After removing the initial enamel layer or pre-existing porcelain veneer, the clinician must make a preliminary assessment of the internal color. In cases of tetracycline staining, the internal color of the dentin is much more intense and hyperchromatic than it is in other forms of staining. The offensive color is a highly chromatic black-brown hue (Figure 2). To create adequate depth of the subopaque material, an additional 0.3 mm of tooth structure needs to be removed along the entire axial wall. This can be achieved with a 0.3-mm preparation guide (Nixon Preparation Kit II). This added preparation should be placed approximately 1.0 mm from all margins. For increased mechanical retention and assurance of normal color along the free gingival margin, about 1.0 to 1.5 mm of tooth structure needs to be removed into the gingival floor of the axial wall preparation (Figure 3). The resulting tooth preparation does not need to be free of stain.
View larger version (69K):
[in this window]
[in a new window]
|
Figure 3. Approximately 1.0 to 1.5 millimeters of tooth structure is removed into the gingival floor from the new axial wall to increase mechanical retention and ensure normal color along the free gingival margin. Notice the removal of the dark stain along the gingival aspect of the preparation.
| |
Increasing color value.
The rationale behind using a modified subopaque layer is to immediately decrease the hyperchromacity and to gradually increase the color value of the discolored teeth from the inside, without using unnatural opacifiers. To achieve this, a combination of hybrid composites and composite opaque materials are used in a sandwich technique. This involves placing a uniform layer of neutral dentin color along the axial surface of the tooth. Hybrid composites contain glass particles that increase the bond strength to both dentin and other substrates, such as porcelain.13 In comparison, opaque materials are microfilled, with a particle size of 0.04 micrometers, which does not provide a bond that is as strong as that provided by hybrid composites (that is, a particle size of 0.6 to 5 mm).5(p121) For this reason, sandwiching the opaque material between the hybrid composite material will create a structurally and optically effective block-out medium.
Before placing the subopaque layer, the clinician places a rubber dam to reduce saliva contamination. The tooth preparations are then pumiced clean and wiped with a chlorhexidine gluconate swab (for example, Cavity Cleanser, Bisco Dental Products) to remove any surface contaminants. The prepared surfaces along the dentin are etched with a 37 percent phosphoric acid for 15 to 20 seconds, and are then thoroughly rinsed with copious amounts of water. The teeth are then lightly air-dried to avoid desiccation and remoistened with an antimicrobial agent (for example, benzalkonium chloride).
Wet-bonding technique.
I use a wet-bonding technique, as described by Kanca14 and Nakabayashi and colleagues,15 to optimally bond the sub-opaque layer to the dentin. A hydrophilic adhesive system (All-Bond 2, Bisco Dental Products) is used in which the primer is placed on the moist dentin, as recommended by the manufacturer. After the primer solvents evaporate and are light-cured, dentinal adhesive resin is lightly placed on the preparations, thinned gently with uncontaminated air and light-cured for 20 seconds.16
The clinician places a thin uniform layer of A-2 hybrid composite along the prepared area of the tooth and light-cures it for 40 seconds. Although hybrid composites are opaque, the discolored teeth still transmit a gray color through the composite. Therefore, the corresponding opaque shade of A-2 (Creative Color, Cosmedent Inc.) is brushed on and thoroughly light-cured to uniformly mask the entire axial surface (Figure 4). Because only a thin layer of opaque material is needed to optically mask the underlying color, adequate room remains for another layer of hybrid composite. This sandwich technique allows for maximal block-out of discoloration and strength needed to bond the porcelain veneer.
View larger version (67K):
[in this window]
[in a new window]
|
Figure 4. Composite opaque material is placed on an initial layer of hybrid composite to further mask the severe staining.
| |
Before taking a final impression, the clinician places 4-0 suture cords in the gingival sulcus of each prepared tooth. These cords displace the gingival tissue apically to establish margins that are slightly sub-gingival. A modified chamfer margin is established uniformly along all areas of the preparation. Refinement of these margins is done such that the proximal contacts are broken and placed along the linguoproximal location. This eliminates the potential for the discoloration to show through along the proximal areas. In addition, the margin of the incisal edges is placed along the lingual aspect to create natural incisal color into the porcelain veneers.
The clinician then uses a 0.020-inch clear matrix fabricated from a diagnostic wax-up to check the preparations for adequate removal of tooth structure. After final impressions are taken with a poly-ether impression material (Impregum, ESPE America), a face-bow transfer along with a bite registration are completed to properly mount the working models on a semiadjustable articulator.
Esthetic provisional restorations are created by using the clear 0.020-inch matrix form.17 After modifying the esthetic provisional restorations to the patient’s satisfaction, the dentist takes another impression to facilitate effective communication (regarding esthetics and function) with the ceramist.
Communicating with the ceramist.
In addition, it is important for the dentist to convey the internal color to the ceramist via slides, photographs or both (including reference shade tabs). According to Daniel Materdomini of da Vinci Dental Studios (oral communication, May 1996), in properly creating natural color enhancement of porcelain veneer restorations, it is important that the ceramist understands the internal coloration of each prepared tooth surface. By preparing the stained teeth to a depth of 0.7 mm, practitioners are able to give the ceramist creative space along areas that may still need slight masking. Having a more natural dentin color along most of the axial tooth preparations allows the ceramist to create a multitude of natural colors in the 0.7-mm thickness of the porcelain veneer.4 The ultimate goal of esthetic treatment is to mimic the combined optical effects of enamel and dentin, imparting a quality of depth to the restorations.
Assessing fit.
At the veneer seating appointment, I use a computer-assisted anesthetic delivery unit (The Wand, Milestone Scientific) to anesthetize the dentition and the gingival tissue along the anterior areas up to the premolars; the upper lip is not anesthetized. This method allows the patient to comfortably preview the esthetic restorations before they are bonded permanently. The provisional restorations are removed and the tooth preparations are pumiced clean and disinfected with an antimicrobial solution. The permanent porcelain veneers are placed in the patient’s mouth—first individually and then together—to assess marginal fit, proximal contacts and esthetics. Different try-in gels (for example, Lute-It, Jeneric Pentron Inc.; Insure Prevue gels, Cosmedent Inc.) are used to select the best luting resin shade from an optical standpoint. Because the anesthesia is confined to the dentition and gingival tissue areas, the patient is able to comfortably assess the esthetic contours, size and color of the porcelain veneers before they are permanently bonded. After the porcelain veneers have been fitted and a permanent luting resin shade has been chosen, the clinician prepares the veneers for bonding.
Veneer preparation.
To prepare the porcelain, I place 37 percent phosphoric acid on the internal surface of the veneer to remove all organic debris and to acidify the internal surface. After thoroughly rinsing the porcelain veneer with water, I place a silane coupling agent to intensify the chemical bonding. A thin layer of unfilled resin is then painted on the internal aspect of the veneers to serve as a wetting agent.
Teeth preparation.
After placing a rubber dam, I prepare the teeth in a conventional manner to clean and disinfect the tooth surfaces. An intraoral microetching unit with 50-mm aluminum oxide is used to first prepare the surface of the sub-opaque layer. Sandblasting increases the surface area and enhances the bond strength between the hybrid composite and the luting resin18,19 (Figure 5). After another thorough rinse, the entire tooth is etched with 37 percent phosphoric acid to prepare the enamel and to acidify the resin surface. The porcelain veneers are then bonded to the prepared teeth in the conventional manner using the wet-bonding technique and resin cement.
View larger version (71K):
[in this window]
[in a new window]
|
Figure 5. Using an intraoral microetching unit, the clinician sandblasts the modified subopaque layer to increase the surface area and enhance the bond strength. Notice the more natural color of the artificial dentin.
| |
Final steps.
The next step is to thoroughly finish all margins and proximal areas using porcelain finishing diamonds (Nixon Veneer Kit II, Brasseler USA) and proximal finishing strips. After this has been accomplished, the clinician checks centric occlusion and lateroprotrusive excursions. The final step is to polish the porcelain veneers (Dialite intraoral polishing kit, Komet/Brasseler USA; porcelain laminate polishing kit, Shofu Dental Corp.) (Figure 6). The result is esthetic restorations that exhibit a more natural appearance in terms of color depth because of their ability to reflect, refract and absorb light naturally (Figure 7).
View larger version (73K):
[in this window]
[in a new window]
|
Figure 6. The final porcelain veneers exhibit a more natural appearance as a result of controlling the internal color via the modified subopaquing technique.
| |
View larger version (93K):
[in this window]
[in a new window]
|
Figure 7. The esthetic restorations properly reflect, refract and absorb light, with the resulting smile appearing natural.
| |
|
CONCLUSION
|
|---|
Although conservative all-ceramic bonded restorations, such as porcelain veneers, are indicated for esthetic and restorative treatment in the anterior dentition, they can be problematic in teeth that are highly discolored. However, when severely discolored teeth are treated with the modified subopaquing technique described above, the resulting restorations can appear natural. By bonding a neutral color of artificial dentin onto the prepared surfaces, I have been able to control the internal color by uniformly masking the stained tooth structure. With the increased use of drugs that can create severe intrinsic stains in the adult dentition, it is important that the practitioner be knowledgeable about materials science and technique to conservatively treat these problems.
|
FOOTNOTES
|
|---|
Dr. Okuda is in private practice, The Waialae Building, 3660 Waialae Ave., Suite 212, Honolulu, Hawaii 96816-3258. Address reprint requests to Dr. Okuda.
|
REFERENCES
|
|---|
- Parkins FM, Furnish G, Bernstein M. Minocycline use discolors teeth. JADA 1992;123:87–9.
- Giunta JL, Tsamtsouris A. Stains and discolorations of teeth: review and case reports. J Pedod 1978;2:175–82.[Medline]
- Cheek CC, Heymann HO. Dental and oral discoloration associated with minocycline and other tetracycline analogs. J Esthet Dent 1999;11(1):43–8.[Medline]
- McLaren EA. The skeleton buildup technique: a systematic approach to the three-dimensional control of shade and shape. Pract Periodontics Aesthet Dent 1998;10(5):587–97.[Medline]
- Crispin BJ. Contemporary esthetic dentistry: practice fundamentals. Carol Stream, Ill.: Quintessence; 1994.
- Yamada K. Porcelain laminate veneers for discolored teeth using complementary colors. Int J Prosthodont 1993;6:242–7.[Medline]
- Terry D. Direct reconstruction of the maxillary anterior dentition with composite resin: a case report. Pract Periodontics Aesthet Dent 1999;11(3):361–7.[Medline]
- Muia PJ. Esthetic restorations: improved dentist-laboratory communication. Carol Stream, Ill.: Quintessence; 1993:141.
- Mopper WK. Renamel restorative system clinical manual. Chicago: Cosmedent Inc.; 1994.
- Fahl N, Denehy GE, Jackson RD. Protocol for predictable restoration of anterior teeth with composite resins. Pract Periodontics Aesthet Dent 1995;7(8):13–21.
- Goldstein RE. Esthetics in dentistry. Vol 1. 2nd ed. Philadelphia: Decker; 1998:277–338.
- Nixon RL. Masking severely tetracycline-stained teeth with porcelain veneers. Pract Periodontics Aesthet Dent 1990;2(1):14–8.
- Reality: the information source for esthetic dentistry. In: Miller MB, ed. 13th ed. Houston: Reality Publishing Co.; 1999:286.
- Kanca J. Resin bonding to wet substrate. I. Bonding to dentin. Quintessence Int 1992;23(1):39–41.[Medline]
- Nakabayashi N, Ashizawa M, Nakamura M. Identification of a resin-dentin hybrid layer in vital human dentin created in vivo: durable bonding to vital dentin. Quintessence Int 1992;23(2):135–41.[Medline]
- Suh BI, Cincionne FA. All-Bond 2: the fourth generation bonding system. Esthet Dent Update 1992;3(3):61–6.
- Morley J. The role of cosmetic dentistry in restoring a youthful appearance. JADA 1999;130(8):1166–72.
- Birmbaum NS. Direct oven-tempered hybrid composite-resin laminate veneers. Pract Periodont Aesthet Dent 1992;4(5): 23–31.
- Hornbrook D. Repair of Class IV fractures utilizing resin and porcelain. Pract Periodontics Aesthet Dent 1993;5(8):55–62.[Medline]
TOP
ABSTRACT
DISCOLORATION IN THE HUMAN...
