Comparing the Surface Behavior of Conventional and CAD-CAM Feldspathic Porcelains in the Face of Laser-Assisted Bleaching and Post-bleach Polishing

Abstract

Introduction: The prevalence of using different esthetic methods increases the possibility of close contact between them with potential adverse interactions. This study aimed to compare the surface changes (microhardness and roughness) in two types of feldspathic porcelain after laser bleaching and post-bleach polishing. Methods: 12 standardized rectangular specimens were prepared for each porcelain group (conventionally layered and CAD-CAM milled). Vickers microhardness and roughness were evaluated before and after the bleaching procedure and after polishing. Data were statistically analyzed using repeated measures ANOVA and t test (P<0.05). Results: The surface roughness of both groups increased significantly after laser bleaching (P<0.001 for conventional and P=0.004 for CAD-CAM porcelains). The polishing process reduced the roughness of both groups; the reduction was significant in conventional specimens (P=0.020). The surface hardness values did not change significantly in the groups after bleaching and post-bleach polishing stages (P=0.142). Generally, the average surface roughness of CAD-CAM specimens was significantly lower (P<0.001), and the surface microhardness of the CAD-CAM group was significantly higher than conventional porcelains (P=0.011). Conclusion: Laser bleaching significantly increased the surface roughness of feldspathic porcelains; however, it did not affect the surface microhardness significantly. Unlike CAD-CAM specimens, polishing significantly improved the surface smoothness of conventional porcelains.