Effects of different surface treatments on phase change and bond strength of zirconia ceramics

Aim: The aim of this study was to investigate the effects of femtosecond laser (Fs) and/or tribochemical silica coating protocols on roughness, bond strength and phase transformation to monolithic zirconia. Materials and methods: One hundred forty four zirconia were randomly divided into nine subgroups according to surface treatment protocols: Control (C), tribochemical silica coating before sintering (TBS), Fs laser before sintering (FBS), tribochemical silica coating before and after sintering (TBS+TAS), Fs laser before sintering + tribochemical silica coating after sintering (FBS+TAS), tribochemical silica coating after sintering (TAS), Fs laser after sintering (FAS), Fs laser and tribochemical silica coating after sintering (FAS+TAS), tribochemical silica coating and Fs laser after sintering (TAS+FAS). Panavia V5 dual cure self adhesive resin cement was bonded to zirconia samples. Surface morphological properties and roughness were evaluated by scanning electron microscopy (SEM) and optical (3D) profilometer. After cementation of the samples, shear bond strength test was performed by applying force at a crosshead speed of 1 mm/min. One sample from each group was subjected to X-ray diffraction analysis (XRD) to determine the phase transformation.The data were analyzed with one-way ANOVA, and Tukey HSD tests at 0.05. significance level. Results: While the groups FAS, TBS+TAS, FAS+TAS, TAS+FAS, FBS+TAS had showed the highest SBS (P<0,05), control and TBS groups demonstrated the lowest SBS (p<0,05). Surface roughness value was found to be higher in femtosecond applied groups compared to other groups. According to the XRD analysis, there was no phase transformation in monolithic zirconia samples as a result of surface treatments before sintering. Femtosecond laser applied after sintering caused much less phase transformation than tribochemical silica coating. Conslusions: For clinical applications, a combination of surface treatments (femtosecond laser and tribochemical silica coating) before and after sintering may be recommended. Clinical use of the FS laser in dentistry is not yet possible. Therefore, Group 4 (SST+SST) can be recommended for clinical application. Group 4 gave the same high SBS value as the Fs laser treated groups, but caused more phase transformation than the Fs treated groups. Key words: Femtosecond laser, Tribochemical silica coating, MDP, X-ray diffractometers, Shear bond strength