Abstract
Persistent pressure change is a common phenomenon within scuba diving with various medical and dental sign side effects. This study evaluates the effect of simulated pressure change due to scuba diving on the microleakage of class II composite restoration. In our methodology, a total number of 150 intact bicuspids are divided into two main groups (A and B), and prepared for a class II composite restoration. The samples of each main group are divided into five subgroups to be prepared with different liners. Then samples are restored with the same resin composite material. The teeth in group A are thermocycled under the normal atmospheric pressure, while group B are thermocycled under simulated scuba diving conditions. The gingival microleakage is assessed based on dye penetration. The group B teeth show a significantly higher microleakage score than their equivalents in group A (p < 0.05). The subgroups without a liner have a higher microleakage score than the other subgroups (p < 0.05). The flowable composite shows the leased leakage scores followed by Nano ionomer, Resin Modified Glass Iononomer, GIOMER, and linerless groups (p < 0.05). Scuba diving could increase the risk of microleakage development beneath class II, a composite restoration.