Dentists are looking for more efficient ways of providing quality care for their patients. In today’s economic environment there is an increased demand for direct restorations. Composite restorations have traditionally been viewed as requiring extra time, attention to detail and expertise compared to amalgam restorations. New materials and armamentaria have been introduced to enable the procedure to be more efficient and predictable.
WARMING COMPOSITE PRIOR TO PLACEMENT
Manufacturers of composite resin restorative materials have been increasing the viscosity of their materials in an attempt to increase filler loading. Generally, the higher the percentage by volume of fillers is, the higher the flexural strength, flexural modulus, fracture toughness and strength.1 This may alter the handling characteristics of the material making it more difficult to place and shape for some practitioners. The newly developed Comax (Addent) composite loading gun requires less pressure to extrude the composite simplifying placement. The viscosity of a composite may be lowered to improve handling characteristics preferred by some dentists by pre-warming the composite material. The Calset (Addent) unit allows for the proper shade of composite to be selected and then warmed to 130° or 150° prior to dispensing into the tooth preparation. The unit allows for placing the preloaded gun into the warmer (Fig. 1). Adaptation to the cavity walls and margins is enhanced. After a few moments the material begins to cool increasing resistance and making shaping of anatomy easier. Composite which is polymerized at an elevated temperature is reported to have a higher polymerization conversion rate and a deeper depth of cure.2-3
OBTAINING CONSISTENT FIRM, CLASS II INTERPROXIMAL CONTACTS
Another challenging aspect of posterior restorations is obtaining firm, well shaped interproximal contacts in Class II restorations.4 A number of matrix systems have been developed for Class II restorations but many provide inconsistent results. Adequate pressure is necessary to separate the teeth so that the contacts are tight following removal of the band. The V-3 ring (Triodent) exerts strong separating force to spread the teeth apart.5 There are two sizes of rings, one for bicuspids and one for molars. The design of the V-ring allows space between the tines for the wedge to protrude outward. Once in place an additional wedge can be placed through the opening on the opposite side if necessary. The wedges that are part of the system are anatomically designed to give the proper emergence profile of the restoration as it extends coronally (Fig. 2). An integral part of the entire system are pin-tweezers to place and remove the band and wedges and forceps to place the retainer. This allows more precise placement, and reduces the likelihood of dropping the band during placement.
MANAGING POLYMERIZATION SHRINKAGE STRESS IN CLASS II COMPOSITE RESTORATIONS
The phenomenon of polymerization shrinkage stress of composite resins has resulted in the advocacy of a number of methods of composite placement to mitigate the problem. Some have advocated a detailed protocol using a multitude of layers (up to nine different layers) to reduce stress formation.6 Others chose to bulk fill the entire restoration and use advanced light polymerization protocols to control the setting stress.7-8 It is my belief that a balanced approach is the best method. I choose to place four segments in the typical large Class II composite restoration. The first segment is placed in the deep interproximal area and fills no more than two thirds of the box at its highest point and half at the lowest point. A pear shaped metal instrument is used to spread the composite out laterally and down to insure no voids (Fig. 3A). The material is then light polymerized. The second increment builds up the entire interproximal to full contour and adapts to the margins (Fig. 3B). The third segment is added along the buccal half of the tooth. Effort is made to insure the adaptation of the composite to the margin. Light polymerization is first conducted through the tooth as much as possible and then from the occlusal9 (Fig. 3C). The final buildup is completed and light cured similar to the buccal segment (Fig. 3D).
CASE PRESENTATION: LARGE CLASS II RESTORATION
A patient presented with a faulty amalgam restoration and radiographic display of interproximal decay on the upper first molar (Fig. 4). The patient was anesthetized and different shades of composite tried on the tooth and polymerized before making the final selection. The desired shade was placed in the composite warmer (Addent Calset). The old restoration was quickly removed (Fig. 5). The visibly decayed areas were removed and the preparation was slowly extended along the pulpal floor in order to confirm the presence of interproximal decay before breaking the contact (Fig. 6). This is a useful check to make sure that the radiographic image of decay was accurate. The preparation was completed (Fig. 7).
The appropriate wave wedge and matrix band were tried in, selected, and loaded in the pin tweezers (two pair). The universal retainer was loaded into the forceps and the band, matrix and retainer were sequentially placed. The matrix band was smoothly burnished to enhance the contact. Take care to not scratch up the metal since this will be reproduced as the shape of the final composite. A resin-modified glass ionomer (GC Fuji Liner LC) was placed over the deep dentin to reduce the likelihood of post-operative sensitivity10 (Fig. 8). The entire enamel was treated with 32% phosphoric acid containing benzalkonium chloride (Bisco Uni-etch w BAC) for 20 seconds while the dentin and set resin-modified glass ionomer was treated for only five seconds. Benzalkonium chloride has been shown to be an effective way of preventing the degradation of the dentinal hybrid layer due to the action of matrix metallo-proteases (MMPs).11 The tooth was thoroughly washed. the enamel dried and exposed dentin left moist. Several coats of a total etch one bottle system (Bisco Universal Bond) bonding agent were applied to the tooth and agitated for 20 seconds. The solvent was gently evaporated and the tooth light cured. The first increment (GC Kalore) was added in the interproximal box and pushed down and out towards the margins. The material was polymerized (Fig. 9). The second increment completely filled the box area to the occlusal height, was shaped and polymerized (Fig. 10). The third increment was added to the buccal, shaped and polymerized (Fig. 11). The last increment was added and light cured (Fig. 12). The retainer and wedge were removed and the band peeled back to allow for additional curing of the interproximal from the buccal and lingual along the gingiva (Fig. 13). Curing along the gingival insures optimal polymerization of composite along the gingival floor which is often located far from the curing light during initial curing from the occlusal surface. Finally the band was removed and the interproximal areas cured once again.
The egg-shaped finishing carbide bur (SSWhite 7406) was used for gross occlusal reduction and to blend the margins between the composite and tooth (Fig. 14). The occlusion was marked using articulating paper (Fig. 15). A small pear shaped carbide bur (SSWhite 245) was used to adjust high spots by creating a groove wherever the occlusion is too high (Fig. 16). In this manner the anatomy is retained without scooping out the occlusal surface. The interproximal area was adjusted and excess removed first using a fine diamond bur (SSWhite 849-011) and then a finishing carbide bur (SSWhite 7901) (Fig. 17). The interproximal area was smoothed below the contact using a narrow finishing strip (3M Soflex Narrow). The composite was finished and polished with sequential coated abrasives (Ivoclar Astopol) and the finished restoration was post-cured for 20 seconds with the light (Fig. 18).
SONIC ACTIVATION OF COMPOSITE MATERIA
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Recently a new composite material has been introduced which is designed to be activated by sonic vibration immediately prior to placement (Kerr Sonic Fill). The activated composite has lower viscosity which improves handling. This allows a more heavily filled composite to be used imparting the positive physical properties that high filler loading provides. The composite has been manufactured with special activators (initiators) that respond to the sonic vibration. In addition it gives a greater depth of cure insuring optimal polymerization in deep preparations. The composite is a nano-hybrid and exhibits only 1.6% volumetric polymerization shrinkage.
The system is easy to use (Fig. 19). The unit dose is pre-loaded by inserting and screwing down into the handpiece. The handpiece is connected by means of a quick disconnect to an air handpiece line. To dispense, the foot pedal is depressed and the sonic handpiece energizes the composite which quickly flows out the tip (Fig. 20). This delivery system works much faster and easier than squeezing the material out with an applicator or scraping it out of a syringe with an instrument. Even though the manufacturer has demonstrated building up a restoration in bulk I still prefer to build incrementally. This allows easier buildup of each facet of the restoration and makes overfilling less likely. The operator must work quickly as the material begins to set and approach the gel state rather rapidly around operatory light. The shaped material is cured for 20 seconds and the next segment is added. Final shaping and polishing is quicker since there is a reduction of excess material. This additive style of building up the tooth results in a more anatomical restoration. The material feels harder than most other composites when shaping with a finishing carbide.
IMPROVED INTERPROXIMAL MATRIX SYSTEM
The newly introduced V-3 Extreme Curve (Triodent) has been developed to give a more anatomical configuration to the interproximal area. The highly contoured bands hug the tooth better allowing easier placement (Fig. 21). Proper anatomy is built into the band with a flush gingival extension for sub-gingival preparations and a rolled marginal ridge at the coronal area. Finishing and polishing is simpler since excess flash beyond the margins is reduced. The bands come in four sizes and are coated with a non-stick surface to make removal of the band around the set composite material easier.
CONCLUSION
Direct composite restorations have become an important part of the active dental practice. Methods to increase efficiency and speed of their placement should be incorporated with the goal being to produce restorations which are long lasting and properly formed. The best way to acquire these skills is to develop systematic and predictable methods and then to objectively evaluate the results over a period of time. Well placed composite restorations should enjoy a long lifetime and should be considered a definitive restoration; not a temporary restoration prior to the placement of a crown. OH
Dr Ward is in private practice in Columbus, Ohio. He is a Diplomate of the American Board of Esthetic Dentistry, a Fellow of the American Society for Dental Esthetics, Fellow in the Academy of General Dentistry and serves as editor of the ASDA Journal. He has lectured internationally and authored pioneering articles in the field of proportional smile design. Email:dward@columbus.rr.com
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