RESUMO
BACKGROUND: Dental composites are one of the most desired restorative materials today. Composite materials can be bonded successfully to human tooth enamel; however, developing the same degree of adhesion to dentin or cementum is a more challenging task. Polymerization contraction stress of dental composites is often associated with marginal and interfacial failures of bonded restorations. The magnitude of stress depends on composite composition and its ability to flow before gelation, which is related to the cavity configuration and curing characteristics of the composite. MATERIALS AND METHODS: This study was carried out on 24 extracted human molars and divided into three groups. Class II (slot) cavities were prepared on the mesial and distal surfaces of the teeth with the gingival wall in dentin/cementum, and the microleakage was observed. After preparation the teeth were randomly assigned into three groups of eight specimens each. The cavities were restored with: Group 1: Packable composite (Surefil, Dentsply); Group 2: Hybrid composite (Filtek Z250, 3M Dental Products); Group 3: Nanocomposite (Filtek Z350, 3M Dental Products). Sixteen samples of each group were subjected to 500 cycles of thermocycling between 5°C and 55°C. All the teeth were immersed in methylene blue for 8 h and then left in tap water for 12 h. The teeth were sectioned mesiodistally with a diamond disc, and examined under a stereomicroscope. RESULTS: The analysis indicated that packable composite showed more microleakage than all the other groups. Hybrid composite showed less microleakage than packable composite, but more leakage than nanocomposite. CONCLUSION: All composites under the study exhibited a certain amount of microleakage in the dentin/cementum margin. Packable composite showed the most microleakage and nanocomposite showed least microleakage. Since these results were obtained in vitro, long-term clinical trials are needed to fully understand the performance of these materials.
