November/December 1997	Jorge Pinero, DDS
Contemporary Esthetics
Direct Adhesive Esthetic Restorations:  The Ideal Restorative Material

Never before in the history of dentistry has there been such a wide selection of restorative dental materials. Today, a dentist has more than just a myriad of tools to choose from; there is now a complete smorgasbord of materials that can provide for the restoration of missing tooth structure, the predictable restoration of the dentition, and replication of the polychromatic characteristics of natural teeth, as well as eliminate postoperative sensitivity.

Advances in composite resins and ceramic materials, including polymer glass systems and injectable ceramics, provide new options for direct restorations, inlays, onlays, and crowns. Significant advances have been made in the areas of luting cements, resin cements, and resin-modified glass ionomers, in addition to hybrid adhesive cements, which combine a high degree of retention and lower solubility than conventional cements. This article demonstrates the use of direct composite resin in restoring teeth to esthetic form and function with state-of-the-art materials.

Dentistry: Past vs Present

Presently, the practice of dentistry differs widely from that offered to our ancestors, primarily due to the demands of the public we serve. In the past, dentistry focused on the delivery of care to diseased teeth, the restoration of those teeth with materials that satisfied the clinician, and the relative biocompatibility of these materials.

Today's public, although maintaining some of the notions held over from classic dentistry, focuses primarily on the esthetic and pain-free approach to restorative care. So, although symptoms have remained the same, the restoration of diseased tooth structure has indeed changed.

Esthetic restorations pose a significant challenge to the clinician. Patients' demands require the use of state-of-the-art restorative materials and instrumentation to accomplish the goals of both the patient and the clinician. The techniques used can be many, such as direct freehand bonding, direct application of laboratory-fabricated ceramic resin, or ceramic copolymer restorations.

Freehand Bonding

The direct application, or freehand bonding technique gives the clinician complete control over the restoration of anterior or posterior dentition, allowing exact replication of anatomy and the

polychromatic shading of natural teeth. Advances in adhesive technology and composite dental materials now permit the dental technician to create a masterpiece of art in the restoration of the human dentition. 1

Laboratory-Fabricated Ceramic Resin or Ceramic Copolymers

Laboratory-fabricated ceramic resin or ceramic copolymers offer exceptional esthetics. The outcome of these restorations depends on proper preparation, skillful shade selection, dentist-laboratory communication, and the artistic skill and knowledge of the dental technician.

These restorations are generally an "all-or-nothing" esthetic process at the time of completion, meaning the resulting esthetics of these restorations are mostly dependent on all of the above requirements. Except for slight modifications of anatomy, extrinsic staining, and hue modification, there is very little that can be done to produce an exceptional esthetic result if all the criteria of the natural dentition are not met.

Onward and Upward

Materials and techniques are now available that combine the properties of well-reproduced contours, highly polished surfaces, high translu-cency, strength, and wear-resistance, and exceptional adhesion to dentin and enamel. The selection of macrofills, microfills, hybrids, and microhybrids is no longer required. Adhesive technology and the new generation composites, such as Herculite® and Prodigy™ (KERR® Corporation), are microhybrid composites that offer exceptional strength, fluorescence, translucency, polishability, and good wear characteristics.3

Anterior and Posterior Composite Restorations

Anterior composite restorations have been useful for procedures ranging from the restoration of Class III and Class IV carious lesions to the complete restoration of the anterior dentition–with exceptional results. Posterior composite restorations are indicated for Class I, II, and V restorations. For maximum strength. Class I and II restorations require an isthmus width of no more than one third of the intercuspal distance.4 Isthmus width greater than the one-third rule would require indirect resin, ceramic, or ceramic copolymer restorations.5

Occlusal Stress

Occlusal stress is an important consideration in selection of the ideal restorative material in posterior and anterior restorations. Studies show that occlusal forces are three times greater in the molar region than in the bicuspid region.6 Proper complete occlusal diagnosis and equilibration are desirable before any restorative treatment with any of the associated materials. Direct composite restorations should not be placed where there is evidence of excessive occlusal force, parafunctional habits, or teeth with extensive fractures or lack of structural integrity.7

Preparation Techniques: Adhesive, Interproxmial & Tunnel

Posterior preparation criteria are dramatically different from G.V. Black's cavity preparation outlines. The general outline form is provided by access to the carious lesion and its complete removal. Adhesive preparations require rounded internal line angles. Retention is further aided by undercuts created from the removal of previous restorations and decay.

Interproximal preparations require rounded-box preparations that extend buccally, gingivally, or lingually, removing only enough to eliminate decay or a previous restoration. Tunnel preparation access from the mesial or distal pit under the marginal ridge can be accomplished without fear of marginal ridge fracture. However, there should be sufficient tooth structure in this "bridge" of the marginal ridge to prevent fractures.8

Enamel Marginal Integrity

Enamel marginal integrity requires that there is no unsupported enamel or thin composite material remaining on the occlusal surface. These areas will result in fracture of the enamel or composite.9

Bond strength of the composite is critical at the marginal area. It is preferable to have finish lines in the enamel to minimize the effects of thermal expansion. Composites have a greater coefficient of thermal expansion than dental structure.10

Often, it is advisable to bevel interproximal areas, which will allow bonding in a greater crosssectional area of enamel. The use of fifth-generation bonding adhesives, such as OptiBond™ (KERR® Corporation), reduces the fracture potential at the cavosurface area, which can result from occlusal stress and thermal variants.11

Clinical Procedure

Figure 1 Preoperative view of carious detention.

A 42-year-old man presented with extensive caries, extensive staining of the dentition, and without any previous restorations (Figure 1). He had extensive occlusal wear and an improper occlusal relationship as a result of parafunctional habits. After a complete occlusal equilibration and reduction in parafunctional habits was accomplished, a restorative treatment plan was devised, which included direct bonded posterior esthetic restorations to mend the carious lesions.

The lower-right quadrant was selected for treatment with restorations that would replace lost tooth structure with sufficient strength to restore his dentition. Multiple restorative materials could have been successfully used to accomplish the desired outcome; however, because of the clinical indications and desired esthetic outcome, the direct freehand approach was used.

Preparation and Adhesive Technique

Rubber dam isolation was accomplished, and all teeth were polished with a flour of pumice (Figure 2). Complete removal of carious lesions was obtained via adhesive preparation techniques in the lower-right first and second molars, lower-right first and second bicuspids, and lower-right canine (Figure 3).

Figure 2 Rubber dam isolation.  Preoperative view. Figure 3 Adhesive preparations showing caries removal.

Areas with deep, extensive dentinal decay resulting in near pulpal exposures were treated with the "wet bond" adhesive technique rather than the conventional calcium hydroxide liner pulp-capping technique. Since the development of the complete etch and fifth-generation adhesive technology that provides a "hybridization" bonding technique, the use of calcium hydroxide liners is rarely, if ever, needed to allow pulpal protection. In actuality, calcium hydroxide liners are contraindicated for use as dentinal liners because they irritate the pulp and can cause dentinal postoperative sensitivity.12 In addition, it has been proven that this hybridization technique reduces dentinal hypersensitivity, provided, of course, that all the technical requirements have been met.

Total Etch Technique

Figure 4 Total etch technique (enamel portion).

The "total etch technique" was employed by using a 37% phosphoric acid gel that was applied to the enamel for 15 seconds, followed by application for an additional 15 seconds to the dentin and enamel (Figure 4).

A total etch of 30 seconds is all that is needed for complete enamel and dentin structure to be properly etched.

Dentinal etching removes the smear layer in the dentinal tubules and exposes the collagen fibers to provide the basis for a hybrid layer and structural bond.13 Etching of dentin should occur for only 15 seconds, because the gel can penetrate the dentinal tubules up to 100 µm to 150 µm if left longer. It is not necessary to etch dentin beyond this time, because most dentinal bonding primers can only penetrate the dentin 25 µm.

Rinsing

The etched teeth were rinsed for 30 seconds with a gentle stream of water to remove all of the gel etchant in the dentinal tubules. Allowing excess grains to remain in the dentinal tubules is one cause of postoperative dentinal hypersensitivity.

The teeth were then blotted dry and had the appearance of wet dentin. Excessive drying of the tooth at this point can cause dehydration of the dentin, which can result in pulpal irritation and lack of proper bond strength; collagen fibers can collapse, which prevents a hybrid layer formation.

Wetting Solutions

Figure 5 Application of wetting solution.

Two different "wetting solutions" were applied to enhance the wet adhesive technique. The first was Tublicid Red (Global Dental Products), which contains benzylclonium chloride, a chemical that provides a bactericidal benefit when applied (Figure 5). The placement was done with a cotton pellet, scrubbing to completely wet the dentin. This solution was thinned with a gentle stream of air, although the teeth were still left moist.

A second wetting solution was placed, AQUA-PREP™ (Bisco Dental Products), containing water and HEMA (2-hydroxy-ethyl methylmethacrylate). This solution is used because the HEMA is hydrophilic, and thus enters deeper into the moist denti-nal tubule, which prompts the collagen fibers to stand erect for optimal bonding.

Adhesive Component Addition

Figure 6 Application of OptiBond bonding adhesive

next step is the placement of the OptiBond™ Solo (KERR® Corporation) adhesive components (Figure 6). The bonding resin is situated to the enamel and dentinal surfaces for 30 seconds, which allows complete penetration into the dentinal tubules.

Because this resin is hydrophilic and contains HEMA, it is attracted to the original wetting solutions, resulting in a deeper penetration of primer into dentin.

The resin is then air-dried for 5 seconds to eliminate the alcohol carrier in the resin, which could cause hypersensitivity. The resin should have a shiny appearance. Air thin, but do not desiccate.

Figure 7 Photopolymerization of bonding adhesive.

The bonding adhesive was then light-cured with a Demetron Optilux 500™ curing light (KERR® Corporation) for 30 seconds (Figure 7). This material combines with the wetting solution and a hybrid layer appears, providing a superior structural bond to the overlying resin and the dentin.14

Composite Placement Technique

The microhybrid composite Herculite® XRV™ (KERR® Corporation) was selected to restore the prepared teeth. Before composite placement, matrix bands and wedges were arranged to provide proper anatomic contours (Figure 8). Incremental layers of dentinal-shaded resin were placed in the boxes and pulpal floors, and each surface was light-cured from all sides for 30 seconds (Figure 9).

Figure 8 Matrix band and wedge placement. Figure 9 Incremental layers of composite on the pulpal floor.

Microhybrids are lighter (of higher value and lower chroma) at an unpolymerized stage and become darker (lower value and higher chroma) after polymerization.15 Before polymerization, a try-in shade (a small, cured resin shade tab) should be used to determine the proper shade selection.

Individual cuspidian lobes were formed with the dentinal shades not exceeding 2 mm in depth and were shaped with a composite placing instrument and a half-Hollenback carver. Using the polymerization shrinkage properties of the composite to gain superior adherence to the cuspal wall, each cusp was cured from the tooth-structure side.

Staining

Figure 10 Occlusal staining to duplicate existing esthetics. Figure 11 Photopolymerization of stained pits and fissures.

Successive cusp formation and incremental placement were accomplished in the above manner until the entire dentinal structure was created. Natural staining in the pits and fissures was accomplished through a blend of stains from Kolor-Plus™ (KERR® Corporation), with a No. 15 endodontic file in the grooves and fissures. A small, fine brush was used to blend the stain and achieve an optimal polychromatic effect (Figure 10). The stain was light-cured for 20 seconds before final resin placement (Figure 11).

Final Composite Placement

Figure 12 Enamel composite placed over stained grooves.

The final addition of the composite enamel portion is also placed in an incremental fashion to create the fine anatomy of the pits and fissures of the natural dentition (Figure 12).

Unfilled bonding resin is placed on the carving instrument to complete the smoothness and artistic quality of the occlusal anatomy, to improve the marginal adaptation, and to enhance the sealing of the tooth-composite interface. The final composite placement was polymerized a full 60 seconds.

Prefinishing and final finishing

Prefinishing was accomplished with 12-fluted finishing burs, extra-fine finishing diamonds, polishing disks, and points before rubber dam removal. Final polishing was accomplished with a similar approach after the evaluation of occlusal contacts.

Occlusal contacts are desirable to maintain proper dentition and should be ideal point contacts without balancing interferences. Final finishing was accomplished with composite finishing points and polishing paste.

Final Surface Seal

Figure 13 Final restoration etched with 37% phosphoric acid.

The final step in the restoration process was to use Opti-Guard™ (KERR® Corporation), an unfilled resin, to provide the final surface seal of the composite tooth interface. The teeth were isolated with cotton rolls, dried, and a 37% phosphoric acid etchant gel was applied on the enamel and composite resin for 10 seconds (Figure 13).

Figure 14 Placement of OptiGuard resin. Figure 15 Final composite restorations.

The teeth were rinsed, dried completely, and OptiGuard'" resin was rubbed over the enamel andcomposite resin (Figure 14). This resin should be thinned with a gentle stream of air and light-cured for 10 seconds. The use of this final sealer enhances the luster of the composite and seals the marginal area exceptionally well (Figure 15). In addition, because OptiGuard™ contains boron tri-fluoride, it leaches fluoride to enhance the life of the restoration.

The resin can be reapplied periodically to provide a longer lasting restoration. This procedure is similar to the initial placement. After proper isolation, the tooth is polished with flour of pumice, rinsed, dried, and etched with phosphoric acid for 15 minutes. Again the tooth is rinsed and dried, and the resin is applied, thinned with a stream of air, and polymerized for 10 seconds. This procedure can aid the longevity of these restorations against marginal leakage, discoloration, and surface degradation, preventing marginal recurrent decay.17

Summary of Restorations

Figure 16 Final restorations showing realistic esthetics.

These restorations provide many of the requirements for the ideal conservative treatment of caries. There are many approaches that can provide similar benefits to the patient, although direct freehand composite resins outperform many other direct and indirect restorations when it comes to esthetics, marginal integrity, surface composition, and efficiency of treatment. If they are meticulously placed, these restorations can provide patients with many years of oral health (Figure 16).

Conclusion

This article presents a clinical interpretation of a protocol used with composite resins. Today's composite restorations provide predictable reconstruction of extensively impaired teeth that is feasible, highly esthetic, and often, the optimal choice for restoring dentitions to the true polychromatic character of teeth.

The ultimate esthetic result requires adequate training, optimal dental materials, and a commitment to excellence in esthetic dentistry. The dentist traverses beyond structural engineer and becomes the artist who revels in the design and creation of his or her masterpiece. The satisfaction that evolves from this creation, both for the clinician and the patient, gives credibility to direct composites as an ideal restorative material.

References
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