Written by Martin G. Abel, DDS, FAGD Thursday, 31 October 2002 19:00
Composites have become an integral part of our restorative practices, however, their evolution was not without growing pains. Among the failures are problems with wear,1 shrinkage, microleakage, open contacts, recurrent caries, and most perplexing, sensitivity.2 Sensitivity can be defined as patient pain or discomfort, particularly with cold foods and drinks. The current philosophies of cause are defined as: (1) polymerization shrinkage of composite (microleakage or pullback of material from the floor of the preparation); (2) unpolymerized composite in direct contact with the dentin floor (or wall) of the preparation; (3) primer solvent (usually acetone or ethanol) not volatilized prior to placement of composite; and (4) occlusal disharmony.
Improved technology in resin material, bonding agents, and techniques has essentially eliminated these obstacles. Wear resistance of composite resin restorative material is comparable with amalgam.3 Vastly improved resin-based composites, bonding materials, and bonding methods have facilitated sealing dentinal tubules, controlling polymerization shrinkage, and limiting microleakage. Tight, anatomical contacts have been routinely achieved with sectional matrix systems. Sensitivity issues are practically nonexistent if proper techniques are followed.
Technique seems to be the major problem.2 The process of restoring teeth with composite resin is certainly more technically difficult than the process of restoring teeth with amalgam. Insistence on treating resin like amalgam will not work! Even with so-called “packable” composites it will not work.4 We are dealing with two entirely different materials and restorative systems. Amalgams require a minimal dimension and bulk to resist fracture. Resin-based composites do not. Furthermore, amalgam restorations require mechanical retention, whereas resin-based composites are retained by adhesion.2 Use amalgam methods for amalgam, and use composite methods for composite!
This article reviews a method for placement of posterior composite restorations that has been successful in our office. There are many excellent resin-based composite materials and adhesives in today’s marketplace. Some are similar in makeup while others have quite different chemistries. It is these differences in chemical makeup that require different application techniques. Therefore, it is important to closely follow manufacturer instructions for the total system. Bonding agents with different solvents require different application techniques.
|Figure 1. Bicuspid class II caries.||Figure 2. Contemporary class II preparation.|
|Figure 3. Rubber dam to isolate tooth from salivary contaminants.|
The class II preparation can be much more conservative than in the past (Figures 1 and 2). In the case described in this article, the preparation of the tooth for a direct placement composite resin restoration was accomplished using a 330 carbide bur (Axis Dental Corporation). The traditional type of preparation works well here, with the following modifications.5 First, breaking interproximal contact is not mandatory. This would have been indicated if amalgam were to be used as the restorative material. The old concept of “extension for prevention” is not necessary when using composite resin as the restorative material. Second, rounded internal line angles work best. It has been discussed that rounded internal line angles permit a better distribution of the stresses of mastication on the composite, and therefore will allow the composite to better resist compressive forces. In addition, with rounded internal line angles, a greater surface area is created in the preparation, giving a stronger bond.5
Use of a rubber dam is essential (Figure 3). With the prepared tooth isolated under the rubber dam, the tooth is ready to be prepared for acceptance of the composite. Etching should not be done until the band, wedge, and ring are in place. If these are not in place, the acid can irritate the root surface and cause hypersensitivity. In addition, the etchant should be kept from the adjacent interproximal contact area to prevent inadvertent adhesion of the bonding agent or composite to the adjacent tooth.
A sectional matrix band with a separating ring is the only way to consistently achieve an accurate interproximal contact. The band restores the actual contour of the tooth at the height of contour, and renders proper bulk to resist fracture. I use the new Composi-Tight Gold system of rings and bands (Garrison Dental Solutions) (Figure 4). I have used their original system for years and thought it was unbeatable, but the new rings are approximately twice the strength and maintain their memory consistently.
|Figure 4. Flexi Wedge and gold matrix installed.||Figure 5. Miris shade guides.|
Prior to placing the ring, I wedge the matrix band in place with a Flexi Wedge (Garrison Dental Solutions) (Figure 4). The wedge should be inserted snuggly until the deepest part of the wedge is at the center of the proximal box. A Flexi Wedge seals the cervical area, and its flexibility will allow the separator fines to be placed on either side of the wedge. The composite resin used in this case was Miris (Coltene Whaledent). At this point I select the dentin shade of the Miris Composite that will be used for the restoration (Figure 5). Following the selection of the dentin shade, I select the appropriate enamel shade. The Miris shade guides are made so the dentin shade guide can fit inside the enamel shade guide, thus showing the final shade for the restoration. The respective tubes of composite are set aside.
|Figure 6. Acid etch.||Figure 7. Dentin bonding with Tenure.|
Acid etching with 37% phosphoric acid for 15 seconds is adequate for achieving a suitable surface for application of disinfectant and then bonding agent (Figures 6 and 7). Composite resin bonding requires a saliva-free environment. It has been written and discussed that a dry field is necessary. This is not the case. The dentin must not be desiccated prior to application of bonding agents. If desiccated, the dentin collagen matrix may collapse and prevent a good bond, as well as cause postoperative sensitivity. The dentin must be kept moist with a mist of water from the air/water spray.
For the next step, I recommend the use of a disinfecting agent. I use Tubulicid Red (Global Dental), however, many other products may be used, such as Consepsis (Ultradent), chlorhexidine, and even sodium hypochlorite (bleach). The reason for disinfecting is to rid the surface of the preparation of bacteria left after acid etching. The use of Tubulicid Red will allow the surface of the preparation to also be moist, as the agent is in aqueous solution. Some clinicians recommend disinfecting before acid etching to remove the bacteria from the surface hybrid layer. That is fine. However, when the tooth preparation is etched and then rinsed, the surface may still have a small amount of residual bacteria, especially in the top and inside of the newly exposed dentin tubules. This would be the best time to disinfect and cleanse the surface of the preparation for bonding agent and then composite restorative material.
The disinfecting procedure requires swabbing the preparation for 15 seconds with the disinfecting agent on a microbrush, the same type of brush that is used to apply the bonding agent. In the case of Tubulicid Red, I do not dry the preparation before application of the bonding agent. The bonding agent I used in this case was Tenure (Den-Mat). Since this agent is carried in an acetone solvent, I want the surface of the preparation to be moist with either water or in this case, Tubulicid Red, because it is carried in an aqueous solution. The bonding agent, being hydrophilic, will percolate further into the dentin tubules, and therefore allow a more complete obturation of the tubules and a stronger bond.6
The Tenure used is the “two-bottle” Tenure. I prefer the fourth-generation product, as I seem to have had better results and fewer cases of postoperative sensitivity.7 Two-bottle systems use acetone as a solvent. Each drop contains less than 20% primer and the rest is solvent, therefore multiple coats need to be applied. Single-bottle primers can be alcohol- or water-based or both. In either case they contain more monomer, and one or two liberal coats is adequate. The fifth-generation adhesives have primer and bond together. The solvents are usually alcohol or acetone. They have a high affinity for water, therefore properly wet the dentin and place one or two large coats of adhesive to seal the dentin.
|Figure 8. Apply flowable composite resin.||Figure 9. Composite set with Virtuoso.|
After placement of the Tenure bonding agent, the tooth is ready to accept the composite. I apply a thin layer of flowable composite (Flowline, Heraeus Kulzer) to the floor of the proximal box and floor of the preparation (Figure 8), and then cure. I feel that this ensures a sealed gingival margin and minimizes the possibility of microleakage. Following the application and curing of the flowable composite, I apply an amount of the dentin shade of Miris, pack it carefully, and then cure with the Rembrandt Virtuoso Curing Light (Den-Mat) for 5 seconds bucally, then 5 seconds lingually. Finally, I apply the enamel shade and cure (Figure 9).
When curing, be aware that holding the light continually on the restorationcan generate tremendous amounts of heat. Have all personnel test the light on their thumbnail. Ouch! Judicious use will reduce sensitivity.
When the matrix setup is disassembled, you will notice the necessity of hemostats or Howe pliers to remove the band. The natural contact has been restored. When finishing, we use a simplified system from Garrison Dental Solutions called Finale. Everything is together in one sturdy, heavy-duty block that will not spill. When burs or polishers are used, simply return them to the block. The whole system can be placed in the ultrasonic (because each item is held separately, they cannot wear against each other). Then after the block is autoclaved, all ingredients are still intact and ready for the next patient, with no sorting required.
|Figure 10. “Raptor” diamond for occlusal refinement.||Figure 11. “Flame” carbide for interproximal finish.|
|Figure 12. Football carbide for occlusal finish.||Figure 13. Final restoration.|
In the finishing process, we first outline the occlusal grooves with the 3-mm conical diamond (Figures 10 through 12). Because the matrix band was held firmly to the buccal and lingual walls by the ring, there is very little flash to trim. If flash is present, trimming can be accomplished with the ultra fine flame (Figure 10). The pear, flame, or football carbides (Figure 11) can be used for occlusal shaping and contouring. Diamond cups are then used to shape and polish using varying pressure. Finally, we check the occlusion (Figure 12) and polish (Figure 13).
Direct resin composite restorations can be a very rewarding treatment modality for the patient as well as the clinician. More and more patients are requesting tooth-colored restorations instead of amalgam restorations. It is important for clinicians to read and learn through workshops and university sponsored courses how to incorporate the use of composite resins as a direct restorative material.
Even managed care and various dental plans, through the pressure of their enrollees, are allowing composite restorations to be used instead of amalgam. We are now entering the era of composite dentistry for restoration of not only smaller lesions but also larger, more complex restorative cases.
1. CRA Dentistry Update. 2001;2.
2. Jackson RD. The importance of technique in preventing postoperative sensitivity when placing bonded restorations. Dent Today.1999;18:44-47.
3. Pediatric posterior restorations. CRA Newsletter. September 1996;3-4.
4. Nash R, Lowe RA, Leinfelder K. Using packable composites for direct posterior placement. J Am Dent Assoc. 2001;132:1099-1104.
5. Jackson RD. Aesthetic inlays and onlays: A clinical technique update. Pract Periodont Aesthet Dent. 1993;518-26.
6. Perdigao J, Swift E, Gomes G, et al. Bond strengths of new simplified dentin-emamel adhesives. Am J Dent. 1999;12:286-289.
7. Kälin C, Paul SJ, Schärer P et al. Evaluation of the interface between one bottle bonding agents and dentin by aryopreparation and low temperature scanning electron microscopy (LTSEM). A pilot study on perfused dentinal samples. J Dent. 1998;26:511-520.
Dr. Abel is an accredited member of the American Academy of Cosmetic Dentistry, a member of the American Society for Dental Aesthetics, a fellow in the Academy of General Dentistry, and a fellow in the International Society for Dental and Facial Aesthetics. He has published both nationally and internationally and lectures on the techniques necessary for using composite resins to predictably restore both anterior and posterior teeth. Dr. Abel maintains a cosmetic dental practice in Rockville, Md. He can be reached at (301) 770-1447.
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