Effect of toothbrushing abrasion on weight and surface roughness of pH-cycled resin cements and indirect restorative materials

Objective: To evaluate wear resistance, by weight loss and roughness changes, of resin cements and indirect restorative materials to toothbrushing and toothbrushing associated with pH-challenge simulation. Method and Materials: The following materials were studied: Enforce resin cement (Dentsply), Rely X resin cement (3M ESPE), Variolink II resin cement (Ivoclar/Vivadent), Artglass indirect resin composite (Heraeus Kulzer), and Duceram Plus porcelain (Degussa). Twenty cylindrical specimens were prepared for each material for a total of 10 groups (n = 10). After finishing and polishing, the specimens were subjected to toothbrushing. One group of each material was pH cycled before abrasion. For toothbrushing, a machine containing soft-bristle tips, dentifrice, and water was used. One hundred thousand brushing cycles were performed. Weight loss was determined as the percentage difference between initial (before brushing) and final (after brushing) measurements. Roughness changes were evaluated by the difference between initial and final measurements. Data were analyzed with the paired t test, 2-way ANOVA, and Tukey test (a=0.05). Results: Paired t test showed significant differences in weight loss and roughness after toothbrushing (P .01). Statistically significant differences were found among materials for both weight loss, which ranged from 0.34% (Duceram Plus) to 1.85% (Enforce/pH), and roughness changes, which ranged from -0.03 µm (Duceram Plus) to 0.29 µm (Rely X/pH). Conclusions: Among cements, Variolink II exhibited the least weight loss and roughness increase. Of all materials, Duceram Plus porcelain presented the lowest weight loss and became smoother after abrasion. pH cycling had no influence on material weight or roughness changes after abrasion. Keywords: abrasion, ceramic, pH cycling, resin cements, roughness, toothbrushing