Surface roughness assessment of resin-based materials during brushing preceded by pH-cycling simulations

This study evaluated the surface roughness pattern of resin-based restorative materials during brushing preceded by a regimen that simulated a dynamic pH-cycling. Restoratives included two resin composites (Renamel Microfill and Charisma), two polyacid-modified composite resins (Compoglass-F and Dyract AP) and one resin-modified glass ionomer cement (Fuji II LC Improved). Twenty standardized cylindrical specimens of each material were prepared according to a randomized complete block design. After finishing and polishing, the average surface roughness (Ra) and profile-length ratio (LR) of the specimens were determined. The experimental units were subjected to a pH-cycling regimen, and then to 10,000 brushing strokes. New readings of both the Ra and LR parameters were obtained. The same protocol of pH-cycling, brushing simulation and surface roughness measurements were repeated 10 times. Data was analyzed using ANOVA according to split-plot design and Tukey's test. Results showed the pH-cycling followed by 10,000 brushing strokes provided a remarkable increase in Ra for all restorative materials except for Renamel. Throughout the brushing simulation, Renamel, Charisma, Compoglass-F and Dyract AP showed steady textures, whereas Fuji II LC Improved exhibited a progressive increase in surface roughness. Among the materials tested, Renamel presented the smoothest surface, followed by Charisma and Compoglass-F, which did not differ from each other except at the baseline. Dyract AP was different from both these materials except at the baseline. Fuji II LC Improved had the roughest surface texture.