Effect of Surface Treatment on the Characterization Layer of 3D-Printed and CAD/CAM Resin Composite Materials

The mechanical action of toothbrushing can lead to the wear of restorations, and the extrinsic characterization layer applied to enhance their esthetics may also experience degradation over time. Therefore, it is essential to evaluate the effectiveness of surface treatments and the durability of this layer in new restorative materials.

This study evaluated the effects of simulated toothbrushing on the optical and mechanical properties of one 3D-printed and two CAD/CAM resin composite materials, considering different surface treatments.

Disks of a 3D-printed material (VarseoSmile Crownplus) and two CAD/CAM resin composite materials (Grandio Blocs and Vita Enamic) were divided into three groups (n = 10) based on surface treatment: control (no treatment after polishing), self-etching primer (Monobond Etch & Prime [MEP]), and hydrofluoric acid with silane. A pigment layer followed by glaze was applied to the surface, which was then evaluated for roughness, color, translucency, and gloss. Specimens were subjected to 3,650, 18,250, and 36,500 cycles of simulated toothbrushing, with measurements taken after each interval. Surface characteristics were analyzed using scanning electron microscopy. Translucency and color difference data were subjected to Two-Factor ANOVA and Tukey's test, while roughness and gloss were analyzed using repeated measures ANOVA and Tukey's test.

Repeated measures ANOVA revealed statistically significant differences (p < 0.05) across the tested factors (time, surface treatment, and their interaction), depending on the material and parameter evaluated. Surface treatment and toothbrushing had a significant impact on roughness, gloss, and translucency (p < 0.05), with varying effects across different materials. Overall, MEP is preferred for VarseoSmile Crownplus, while acid conditioning is most suitable for Grandio Blocs and Vita Enamic. Two-way ANOVA indicated statistically significant differences for color and translucency difference, with higher values after applying the characterization layer.

Surface treatment played a key role in maintaining the longevity of the characterization layer. Although simulated toothbrushing led to progressive wear, the application of surface treatment before characterization effectively mitigated this degradation.