Evolution of Composite Materials
During the past 60 years, the use of composite resin for direct restorations in anterior and posterior teeth has increased significantly,1 largely due to the esthetic demands of patients and concerns regarding mercury in amalgam fillings. Because composite resins require little to no preparation, minimally invasive procedures can be used to preserve tooth structure and provide natural-looking results.2 Composite resin also may eventually replace silver amalgam for direct restorations.3
Dental composites typically are composed of three chemical materials: an organic matrix, an inorganic matrix, and a coupling agent. Because composite resins require a bonding procedure for durability and reliability, they must be biocompatible and bond well to both enamel and dentin.5 Direct restorative materials also are required to resist masticatory forces and demonstrate mechanical properties similar to those of natural teeth.5 Composite resins must also be easy to use if they are to replace silver amalgam for direct fillings.5
In the 1990s, microleakage, which can ultimately lead to secondary caries and sensitivity, still caused concern.2 Between 24 and 32 shades of composites were available, and composite layering remained a technique embraced mostly by more elite clinicians.2 However, dentists did begin to architecturally build teeth and the chemistry of composites did improve with the development of microhybrids.2 With a heterogeneous aggregate of fillers, the physical characteristics and polishability of composites also improved.2 Unfortunately, however, microhybrids did not retain their final gloss.2
Today’s composite resins produce highly esthetic, long-lasting restorations for many indications.2 Through an understanding of advanced layering techniques, microleakage and fracture rate concerns have decreased significantly.3 Fewer shades of composites with better chameleon effects improve esthetic outcomes, while enhanced filler particles promote excellent polishing, finishing, and longevity.3 To build dentin and enamel characteristics, material and particle refraction indices and integrated value scales enable proper shade selection.3
Increasingly used for anterior and posterior restorations, composite resins have evolved considerably.6 Modern composite resins demonstrate greater durability, better handling characteristics, less shrinkage, improved polishing, enhanced bond strengths, and highly esthetic outcomes.6,7 However, composite placement remains technique-sensitive, and post-polymerization shrinkage can still be an issue.6,7
Flowable or injectable composites are gaining momentum in use because their filler rates are high enough to be used as a final restorative material for minimally invasive restorations. From a creative standpoint, some manufacturers have created a color palette of flowable specialty shades that artistically create injectable restorations.
Bulk-fill composites are appearing in the literature because of their depth-of-cure rates. A clinician can cure up to 4 mm per increment according to the scientific data. In addition, polymerization shrinkage has decreased to allow the clinicians to become more efficient in their restorative sequences.
Composite resins have evolved to represent artistic alternatives for the direct restoration of anterior and posterior teeth.4 Through improvements in formulations, optimization of physical and optical properties, and the development of new placement techniques, today’s direct composite resins enable reliable and predictable realization of esthetic outcomes.3 Simultaneously, their proven adhesive capabilities contribute to minimally invasive and tooth-conserving treatment plans.4
References
1. Minguez N, Ellacuria J, Soler JI, et al. Advances in the history of composite resins. J Hist Dent. 2003;51(3):103-105.
2. Sensi LG, Strassler HE, Webley W. Direct composite resins. Inside Dentistry. 2007;3(7):76.
3. Fortin D, Vargas MA. The spectrum of composites: new techniques and materials. J Am Dent Assoc. 2000;131(suppl):26S-30S.
4. Hervás-Garcia AH, Martínez-Lozano MA, Cabanes-Vila JC, et al. Composite resins. A review of the materials and clinical indications. Med Oral Patol Oral Cir Bucal. 2006;11(2):E215-E220.
5. Kugel G, Perry R. Direct composite resins: an update. Compend Contin Educ Dent. 2002;23(7):593-608.
6. Ritter AV. Direct resin-based composites: current recommendations for optimal clinical results. Compend Contin Educ Dent. 2005;26(7):481-527.
7. Puckett AD, Fitchie JG, Kirk PC, et al. Direct composite restorative materials. Dent Clin North Am. 2007;51(3):659-675, vii.
About the Author
Frank J. Milnar, DDS, AAACD
Private Practice
Saint Paul, Minnesota
