Golden Rules for Successful Composite Resin Restorations

Very often, colleagues and students ask me, “What is the best composite to use?” It took me a while to find a reasonable and convincing answer to this question! One must keep in mind that the specific composite material that a doctor chooses is not the only factor in the success or failure of a restoration. For example, many studies have shown that 50% of the dentists worldwide use light-curing devices that transmit energy below the accepted level (600 mW/cm2) resulting in postoperative sensitivity, early discolorations of the restorations, pulp necrosis, and other problems.
The success of a composite restoration depends on 3 main factors: the selection of a good quality composite; proper use of an appropriate bonding system; and use of a light-curing system that is capable of delivering enough energy to properly complete the polymerization process. Consequently, any technical error committed during one of those 3 steps, can result in clinical failure.

EVOLUTION OF COMPOSITE RESINS

Composite resins have been used for nearly 50 years and, year after year, improvements have been made regarding their composition and handling. Since 1960, many classifications of resin composites have been introduced. Most of these have differed mainly in the particular filler system used; conventional or traditional, microfine or small particle composite filled with silicium dioxide microfillers, and hybrids (microhybrid, minihybrid, submicron hybrid, and nanohybrid).
For traditional composites the main shortcomings included a lack of lifelike aesthetics and difficulty in achieving an adequate and long-lasting polish. For microfine composites the drawbacks mostly involved having weaker mechanical properties. Hybrid composites contain large filler particles and a small amount of colloidal silica (SiO2) to produce a material with higher filler loading.1 They combine good aesthetics with physical and mechanical properties being better than traditional and small particle filled composites.
Composites resins may also be considered according to their consistency with the introduction of both flowable and packable hybrid composites. Flowable composites, with lower filler content and smaller particle size, have a low viscosity.2 Manufacturers suggest various indications for their use: pit and fissure sealants, repair of marginal defects, liners in deep cavities, and as a direct restorative material for class V restorations.
Packable composites, also referred to as high-density composites, are materials with “supposed” higher filler content for posterior use. Although they have been referred to as “condensable” composites, they in fact cannot be actually condensed. According to the manufacturers, improvements regarding handling properties such as reduced stickiness and increased viscosity (packable) are achieved either by increasing filler loading or by modifying the resin. High-viscosity packable composites, with their lack of stickiness, are supposed to help in establishing tight interproximal contacts. However, in practice these materials have not been shown to have physical-mechanical properties than universal hybrid composites. In addition, some are not easy to adapt to cavity walls and can be difficult to polish. Furthermore, “packability” did not help in obtaining a better contact point.3
A few years ago, nanocomposites containing nanoparticles and/or nanoclusters were marketed. They were supposed to show improved polishability and luster over time, and better wear resistance. In vitro and in vivo investigations conducted thus far has demonstrated similar behavior to microhybrid composites.4-5 Therefore, nanocomposites should not be considered a completely unique category, but rather as a subdivision of hybrids containing some nanofillers.
Although polymerization shrinkage has not yet been totally eliminated in composite resins, other problems such as stickiness, consistency, slumping, and handling have been recently addressed.6-8 Composites resins are influenced by both the organic and the inorganic fraction, and composite materials from the same category can have different viscosities. In fact, the rheological properties of restorative materials suggest the method of manipulation that can influence the success or failure of the restoration.
This article will present 2 case reports in which a newly introduced composite resin material (Herculite Ultra [Kerr]) was used. This material, with new nanofiller technology, is based on the resin matrix science of Herculite (Kerr) that has been used successfully for anterior and posterior restorations for more than 20 years.9 Per the author’s experience, some positive clinical characteristics in the newer material includes improved aesthetic properties, polishability, and gloss retention. Moreover, excellent consistency and a lack of stickiness allows for easier handling and adaptation to the cavity walls.

Figure 1. Preoperative view of the mandibular molars, teeth Nos. 18 and 19.	Figure 2. Field isolation with a rubber dam (OptiDam [Kerr]).
Figure 3. Cavity preparation was done using a small pear-shaped (330) tungsten carbide bur (Jet Burs [Beavers Dental—a Kerr company]).	Figure 4. The completed minimally invasive class I cavity preparations.
Figure 5. Etching was done for 20 seconds with a 37% phosphoric acid gel.	Figure 6. Wet dentin surfaces after thoroughly rinsing off the etching gel.
Figure 7. Bonding application (OptiBond [Kerr]).	Figure 8. The bonding adhesive was light-cured 20 seconds.
Figure 9. Application of the first layer of the nanofilled composite (Herculite Ultra [Kerr]), shade A3 Dentin.	Figure 10. Thorough polymerization of each layer of composite was done.

After verifying via the radiographs that caries did not extend interproximally, a preformed 3D-rubberdam (OptiDam [Kerr]) was placed on the posterior teeth using an autoclavable plastic clamp (SoftClamp [Kerr]) on tooth No. 18 and multifunctional floss (Fixafloss [Kerr]) between the premolars (Figure 2). Cavity preparation under rubber dam provides a clear working field for the practitioner, and isolates and protects the soft tissues. Furthermore, a rubber dam can greatly improve patient comfort.
A small pear-shaped (330) tungsten carbide bur (Jet Burs [Beavers Dental—a Kerr company]) was used for the cavity preparations. Compared to diamond burs, carbide burs generate less vibration that could possibly damage the pulp, and tend to be more efficient at cutting tooth tissues (Figure 3). The selection of correct size and shape of the bur results in achieving minimal preparations, preserving sound enamel and dentin as shown in Figure 4 on the second molar.
The 2 class I cavities (teeth Nos. 18 and 19) were restored simultaneously since no contact point reconstruction was involved. The teeth were etched with phosphoric acid gel (37% concentration) for 20 seconds (Figure 5), and then thoroughly rinsed for 10 seconds with water and air to remove the acid and smear layer. Next, excess water was removed; however, the dentin surfaces were left wet for the bonding procedure (Figure 6). A fourth generation bonding system (OptiBond [Kerr]) was used. The primer was applied using a microbrush, lightly scrubbed for 15 seconds, then gently air dried. Then, the adhesive was applied for 15 seconds (Figure 7) and light-cured for 20 seconds (Figure 8).
The cavities were filled using the layering technique concept. Small amounts of composite were employed in order to minimize polymerization shrinkage, to ensure complete polymerization in deeper areas, and to produce a void-free restoration through better adaptation between the composite layers and the cavity walls. Any gap or void, especially between the first layer and the floor of the cavity, may cause postoperative sensitivity and/or microleakage. Other advantages of the incremental technique include controlling tooth morphology (shape) as well as the ability to enhance the aesthetic results (shade) via the mixing of different shades and opacities of the composite material.
The first layer of composite (A3 Dentin) was placed in the bottom of the cavity (Figure 9). Next, layers of A2 Enamel and Incisal were placed. Each layer of composite was individually polymerized for 40 seconds after placement using a light-curing device with a minimum energy output of 600 mW/cm2 (Figure 10).
Figure 11 shows the completed restorations before the rubber dam was removed, and before the finishing and polishing phase was initiated.
Finishing and polishing are 2 very important and separate steps that contribute to the success and longevity of any composite resin restoration. Finishing includes shaping and contouring of the restoration, while polishing imparts the shine and luster to the composite surfaces. Filling the cavities using small increments of composite, also allows more precise control of the anatomy thereby reducing the time required to finish the restoration.
Finishing and polishing was accomplished in this case utilizing 12- and 30-bladed multifluted finishing burs. These come in various sizes and shapes. Figure 12 shows the use of an egg-shaped (9406) multifluted 30-bladed fine finishing bur (Jet Burs [Beavers Dental—a Kerr company]) followed by the use of a silicone carbide brush (Occlubrush [Kerr]) (Figure 13). Other manufacturers offer polishing systems that can also be used to properly accomplish this task.
At a one-month postoperative visit, both the composite resin restorations showed excellent morphology and aesthetic integration with the natural dentition (Figure 14).

Figure 11. Completed occlusal anatomy before rubber dam removal.	Figure 12. Finishing of the composites with an egg-shaped 30-bladed tungsten fine finishing bur.
Figure 13. Polishing the restorations using a silicone carbide brush (Occlubrush [Kerr]).	Figure 14. One-month recall showing excellent occlusal morphology and aesthetic integration of the composite and natural tooth structure.
Figure 15. Preoperative view of the defective anterior restoration.	Figure 16. Rubber dam isolation and application of a translucent matrix with a wood wedge.
Figure 17. Beveling of the cavity on the facial aspect using a football-shaped (379) diamond bur.	Figure 18. Composite application using a nonstick modeling instrument (Comporoller [Kerr]).
Figure 19. Different sizes and grits of composite polishing discs (OptiDisc [Kerr]) were used.	Figure 20. Postoperative view of composite resin (Herculite Ultra [Kerr]) restorations.

Shade selection was done prior to rubber dam application, before the teeth would become dehydrated causing them to lighten. Then anaesthesia was delivered and the old composite resin restorations were removed under copious water irrigation. A rubber dam (OptiDam [Kerr]) was applied from the first right to the first left premolar in order to achieve optimal moisture control during the restorative procedure (Figure 16). A tight ligature was made around the second right incisor with dental floss for complementary isolation. Then, a translucent matrix was fixed between teeth Nos. 7 and 8 with a wooden wedge inserted to avoid over contouring.
Bevelling was performed on the cervical-incisal margin using a coarse diamond football-shaped (379) bur (Figure 17). This increases retention on the enamel surface and allows a better shade transition between the composite material and tooth structure.
Etching and bonding procedures were performed following the same steps described earlier in case 1. The buildup of the restoration was performed using layers of composite (Herculite Ultra [Kerr]), placed in different geometrical aspects in order to reproduce the proper anatomy of the tooth. An innovative composite modeling instrument with nonsticky rolling tips (Comporoller [Kerr]) was used to manipulate and adapt the composite on the facial wall of the tooth without the inclusion of any unwanted voids (Figure 18). Again, as in case 1, each individual layer of composite is light-cured from both the facial and lingual sides for 40 seconds.
Finally, contouring discs (OptiDisc [Kerr]) with varying grits were used to finish and polish the composite restoration (Figures 19 and 20). These discs are available in 2 different diameters and 4 grits; coarse and medium for finishing, and fine and extra fine for polishing. They were used consecutively without water irrigation, but between using each individual disc, debris was rinsed thoroughly with water spray.

CONCLUSION

Despite the numerous techniques now available in restorative dentistry, we must still rely heavily on direct restorative techniques. Achieving a successful composite resin restoration is not a difficult task if we respect some golden rules (key steps) during the restorative procedures. Additionally, case selection is a very important factor in determining aesthetic and long-term functional success. The size of the cavity, the limits of the cavity, and the habits of the patients must also be considered when treatment planning decisions are made for any direct restorative technique. If not, other options such as indirect restorations (inlays-onlays or ceramic crowns) ensuring a better and long lasting protection of the dental tissues, will be recommended.
Innovative nanofilled universal (anterior/posterior) composite systems are now being introduced and they are producing excellent clinical results when used properly. The use of a proven enamel and dentin bonding system, combined with accurate layering techniques, will enable the dentist to obtain excellent direct composite restorations while preserving tooth structure.

References

Dr. Sabbagh graduated from the Saint-Joseph University (Beirut) in 1996 and in 2000 he obtained a master in Operative Dentistry (Restorative Dentistry and Endodontics) from the Catholic University of Louvain (Belgium). He also obtained 2 certificates of Advanced Studies in Biomaterials and Operative Dentistry from the University of Paris-VII (France) in 1997 and 1998. In 2004, he obtained his PhD in Biomaterials from the Catholic University of Louvain. He has published many articles in dental literature and has lectured locally and internationally. He is Fellow of the International College of Dentists, a member of the Lebanese Dental Association and member of the Academy of Operative Dentistry. He is an assistant professor in the department of Conservative and Aesthetic Dentistry in the Lebanese University, Lebanon; a Senior Lecturer in Operative and Cosmetic Dentistry in the “Dental College” (a Lebanese private college for dental continuing education) Beirut, Lebanon; and a Fellow researcher in the Catholic University of Louvain (Cribio division), Belgium. He has private practices in Beirut and Brussels specialized in Cosmetic Dentistry and Endodontics. He can be reached by e-mail at josephsabbagh@hotmail.com.

Disclosure: Dr. Sabbagh did not report any disclosures.