Comparative evaluation of the microtensile bond strength of bulk fill and low shrinkage composite for different depths of Class II cavities with the cervical margin in cementum: An in vitro study

AIM: The aim of this study was to evaluate the microtensile bond strength (μTBS) of bulk fill and low shrinkage composite for different depths of Class II cavities with the cervical margin in cementum. MATERIALS AND METHODS: Standardized conservative box-shaped Class II cavities were prepared on sixty sound-impacted human third molars. The samples were randomly divided into two groups: Group I (n = 30) - horizontal incremental technique and Group II (n = 30) - bulk fill technique (SonicFill). They were further subdivided into three subgroups of (n = 10) samples each according to the different occluso-gingival height: subgroup (A - 4 mm, B - 5 mm, and C - 6 mm). The gingival margins for all the samples were located 1 mm below the cementoenamel junction. The restored samples were subjected to thermocycling (500 cycles) followed by μTBS testing. The scores were statistically analyzed using ANOVA and post hoc test using SPSS software version 16. RESULTS: Subgroups IA and IB showed lower μTBS than subgroups IIA and IIB (P < 0.05) whereas subgroup IC showed higher μTBS than subgroup IIC (P < 0.05). SonicFill showed a significant reduction in μTBS as the depth increased. CONCLUSION: SonicFill should be used in two increments for cavities with a depth of more than 5 mm.