Abstract
BACKGROUND: Objective: To compare two in-vitro protocols to study the effect of simulated gastric acid on the mechanical properties of resins based composites(RBCs). MATERIAL AND METHODS: Three RBC FILTEK Supreme XTE (FS), BRILLIANT EverGlow (BE), GrandioSo (GS) were used. They were randomly divided into a control group (CG) and two groups exposed to simulated gastric acid: a 6-month daily protocol (DG) and an accelerated 90-min protocol (AG). Vickers microhardness (VH) and flexural strength were evaluated at baseline and six months. Statistical analysis was performed using repeated measures ANOVA tests for VH and three-way for flexural strength data (α=0.05). RESULTS: Daily exposure in the CG and DG groups caused a reduction in VH values and flexural strength (p<0.05). The majority of values in the AG remained stable, after an exposure of 90 min; FS (p=0.118) and GS (p=0.729) in VH and FS (p=0.377), BE (p=0.692) and GS (p=0.672) in flexural strength. CONCLUSIONS: Daily exposure during 6 months caused significant changes in the VH values and flexural strength of the RBCs. The acid-accelerated protocol did not cause the same magnitude of change in VH values and flexural strength seen at six months of daily exposure. Key words:Gastric acid, hardness, composite resins, flexural strength, dental materials.