Surface roughness and flexural strength of self-glazed, polished, and reglazed In-Ceram/Vitadur Alpha porcelain laminates

Purpose: Because of existing controversy, the present study investigated 3 methods for reducing surface roughness and improving the strength of porcel ain restorations. Materials and Methods: Ninety laminated In-Ceram/Vitadur Alpha self-glazed porcelain disks were fabricated and-randomly divided into 3 groups (n = 30 each). Group 1 consisted of 30 of the original disks. The remaining 60 disks were then polished by 6 operators according to the reco mmendations of the American Academy of Esthetic Dentistry; group 2 consiste d of 30 of these polished disks. The remaining 30 polished disks were regla zed (group 3). Average roughness values (Ra) of the veneers were measured b y a profilometer, In each group, 20 disks were subjected to a flexure test, with 10 of the In-Ceram cores and 10 of the Vitadur Alpha veneers placed i n tension. Results: The Ra values were 0.5 +/- 0.1 mu m; 0.7 +/- 0.3 mu m, and 0.4 +/- 0.1 mu m for groups 1 to 3, respectively. Following one-way ana lysis of variance (ANOVA), Bonferroni's multiple comparison tests found tha t groups 1 and 3 were significantly smoother than the polished group (P < 0 .001). Reglazed disks were also significantly smoother than the original se lf-glazed disks (P < 0.01). With the veneers in tension, the flexural stren gths were 151 +/- 22 MPa, 118 +/- 22 MPa, and 172 +/- 27 MPa for groups 1 t o 3, respectively. Following one-way ANOVA, Bonferroni's multiple compariso n tests found that groups 1 and 3 were similar and were significantly stron ger than the polished samples (P < 0.05 and P < 0.001). Conclusion: Reglazi ng polished porcelain surfaces significantly improved the surface texture a nd flexural strength of the materials tested.