The effect of thermomechanical loading on gingival microleakage of bulk fill composite

Abstract Purpose To evaluate the effect of thermo mechanical cycling on gingival microleakage of bulk fill composite versus conventional one. Patients and methods A total of 32 noncarious human premolar teeth were mounted in acrylic blocks (only roots were embedded). Class II cavities were prepared with the following dimensions the occlusal cavity was 3 mm in depth and 2 mm in width buccolingually, the dimensions of the proximal box were as follow, the gingival wall was 1 mm above the cemento-enamel junction, the axial wall height was ~3 mm, the axial wall depth was 2 mm. Specimens were randomly divided into two equal groups (16 each) according to the restorative material, for group I tetric N-ceram composite was used and for group II tetric N-ceram bulk fill composite was used. Half of the specimens in each group were then subjected to 500 thermal cycles from 5 to 55°C with 30 seconds(s) dwell time, and 20 s transfer time and then subjected to 120 000 cycles of loading with a force of 60 N, frequency of 2 Hertz and displacement of 1 mm by using a chewing simulator machine, The other half of the specimens were left without thermal or load cycling. All surfaces of the teeth except 1 mm around the margins of restoration were sealed with two layers of nail polish. Then, the teeth were immersed in 0.5% basic fuchsin solution for 48 h. All specimens were then sectioned in the mesio-distal direction through the center of restorations using isomet saw to detect dye penetration by the stereomicroscope. The recorded data was collected, tabulated, and statistically analyzed using SPSS version 26. Results There were no significant differences among the gingival microleakage of both types of composite in both unloaded and loaded groups. Conclusions Thermal and load cycling did not affect the gingival microleakage of class II cavities restored with composite by bulk filling technique or those restored with the incremental technique.