Marginal adaptation of thermoviscous bulk-fill composite in class II cavities

Objective To evaluate the marginal adaptation of thermoviscous bulk-fill, preheated, and conventional nanohybrid composite resins in class II cavities. Patients and methods Thirty extracted human sound molars were selected in this in vitro study. Simple class II cavities were prepared using carbide bur. The overall dimensions and depth of cavities were standardized as follows: 4 mm length occlusocervically, 4 mm width buccolingually, and 2 mm depth axially. The teeth were randomly divided into three groups (n = 10 each). Futurabond DC (one-step self-etch adhesive) was applied in all groups. Group 1: cavities were restored with VisCalor bulk composite, group 2: cavities were restored with Grandio composite, group 3: cavities were restored with preheated Grandio composite. The specimens of each group were thermocycled in a thermocycling apparatus by alternating immersion in a water bath at 5 and 55°C with a dwell time of 2 min for 600 thermal cycles. Impressions of the teeth were made and then poured with epoxy resin and replicas were examined under scanning electron microscopy to examine marginal gaps. All data were collected, tabulated, and statistically analyzed. Result The highest percentage of marginal gap length was recorded for group 2, recording 22.93%, while there was no significant difference between group 1 and group 3, recording 13.44 and 13.83%, respectively. One-way analysis of variance test was used to compare the tested groups at a level of significance (P < 0.05). Conclusion The marginal gaps decreased when VisCalor bulk and Grandio composite resins were applied after preheating so preheating composite resins considerably improves marginal adaptation.