Effect of C-factor on Micro-tensile Bond Strength of Bulk fill V/S Micro-hybrid Composite in Class II Restorations - An In-Vitro Study.

Abstract

High Configuration factor (C-factor) results into increased polymerization shrinkage causing stress at resin-dentin interface leading to failure of the restoration. The purpose of this study was to evaluate the effect of C-factor on micro-tensile bond strength (μTBS) of bulk fill composites in class-II cavities when restored in 4mm of bulk as compared to conventional composite. A total of 90 carious, crack free extracted human mandibular permanent molars were selected and randomly divided into 3 groups (n=30). On all samples, class II cavities (3.5X 3.5cm) were made by single operator and divided as Gp1 (2.5mm), Gp2 (4mm), and Gp3 (6mm) on the basis of depth of cavities. Sampling units of 30 in each group were further randomly subdivided into 3 subgroups (n=10 each subgroup), according to the type of composite resin systems to be used for restoration. Experimental Subgroup includes SubGp1 restored with SDR Surefil (Dentsply, caulk, USA) and SubGp2 restored with Sonic fill (kerr, orange, CA, USA), whereas SubGp3 restored with FILTEK Z250 served as control. After storage in water at 37◦C, the teeth were sectioned perpendicular to the restorative tooth interface as 1×1 mm non-trimmed rectangular micro-specimens for micro-tensile bond strength (μTBS) testing. Beams (n=30 max) from each SubGp were fixed to a metal jig and subjected to micro-tensile bond strength testing. The data collected for micro-tensile bond strength (expressed in Mpa) were statistically analysed using one way ANOVA and Tukey's post hoc test. In class II cavities with high C-factor, SDR Surefil showed better μTBS than SonicFill and micro-filled composite when filled in bulk of 4mm, as compared to micro-hybrid composite filled incrementally. There is no effect of high C-factor on μTBS of tooth restored with both SDR Surefil and Sonic Fill in class II cavities as compared to microhybrid composites.