Marginal and Internal Adaptation of Different Flowable Composite Restorations in Class V Cavities after Thermomechanical Cyclic Loading: In vitro study

Objective: This study aimed to evaluate and compare marginal and internal adaptation of different flowable composite restorations in class V cavities after thermomechanical cyclic loading. Material and methods: One hundred freshly extracted human premolars with class V cavities on the facial surface were randomly assigned into five main groups (n=20) according to the type of restoration materials. Group I was restored with short fiber-reinforced flowable, group II with self-adhesive flowable, group III with ORMOCER-based bulkfill flowable, group IV with resin-based bulkfill flowable, and group V with injectable flowable. Each group was divided into two equal subgroups (n=10) according to the examination state at Non-Thermomechanical cyclic loading (N-TMC) and after thermomechanical cyclic loading (TMC). However, the TMC subgroup was evaluated after thermomechanical cyclic loading, which involved 5000 thermal cycles (5°±1℃ to 55°±1℃) and simultaneous mechanical stress applied with 100,000 load cycles at 100 N and 4 Hz, and evaluated for marginal and internal adaptation using a scanning electron microscope. The data were statistically analyzed using the Monte Carlo test to compare the studied groups, and the McNemar test was used to compare N-TMC and TMC results, with a statistically significant level set at (P≤0.05). Results: There were no statistically significant differences at N-TMC and TMC results for marginal adaptation when comparing between groups with P = 1.0 and 0.08, respectively. In other ways, there were statistically significant differences when comparing both states in the same groups, with P= 0.007 for group I and P ≤ 0.001 for all other groups. Additionally, there was a statistically significant difference in N-TMC results for internal adaptation when comparing groups with P<0.001, and no statistically significant difference between the groups in the delayed state p = 1.0. Finally, there was a statistically significant difference when comparing N-TMC with TMC in all groups with p <0.001 except group V, where there was no statistically significant difference with P=1.0. Conclusions : Different flowable composite restorations exhibited good marginal and internal adaptation in class V cavities. Short fiber-reinforced flowable composite restorative system had better adaptation than other restorations. Thermomechanical cyclic loading exerted a negative effect on both marginal and internal adaptation