Erosion of CAD/CAM restorative materials and human enamel: An in situ/in vivo study

This in situ/in vivo study aimed to evaluate the effects of erosion on the surface microhardness, substance loss, and surface roughness of CAD/CAM restorative materials and human enamel. This study used a 2-treatment (14 days each) crossover design with 8 healthy volunteers. Each volunteer wore an intraoral appliance containing 3 CAD/CAM restorative material specimens [IPS e.max CAD, Lava Ultimate CAD/CAM Restorative, and a poly (methyl methacrylate) (PMMA) block for CAD/CAM] and 1 human enamel specimen. The specimens were subjected to in vivo erosion cycles by rinsing with 150 ml of cola drink (4 x 5 min/day) for 14 days. The surface microhardness, substance loss, and surface roughness of the specimens were measured at baseline (T1), day 7 (T2) and day 14 (T3). The data were statistically analyzed using repeated measures ANOVA and Tukey's test (alpha = 0.05). After erosion, significant increases in substance loss and surface roughness were observed for enamel, though the surface roughness and substance profile of the tested restorative materials remained unchanged. Erosion significantly decreased the surface microhardness of all materials. For IPS e.max and Lava Ultimate, a significantly higher percentage of surface microhardness loss (%SMHl) was found at T3 than at T2, while no significant difference was found between T2 and T3 for enamel and the PMMA block. In conclusion, CAD/CAM restorative materials showed smaller changes in surface roughness and the surface profile than human enamel after in situ/in vivo erosion. However, CAD/CAM restorative materials and human enamel showed similar changes in surface microhardness after in situ/in vivo erosion.