Effect of different surface treatments on the biaxial flexural strength of zirconia ceramics

Abstract

Statement of problem. Different surface treatments have been applied to zirconia restorations in clinical practice to increase the bond strength between zirconia and cement, but their effect on flexural strength is unknown. Purpose. The purpose of this in vitro study was to evaluate the effect of different surface treatments before and after sintering on the flexural strength of zirconia. Material and methods. Sixty disk-shaped specimens with an initial diameter of 18.6 +/- 0.1 mm and thickness of 2 +/- 0.1 mm were prepared from preshaded presintered 3Y-TZP blocks. The specimens were randomly divided into 3 groups (n=20) according to surface treatments (Group Laser, Group APA, Group Rocatec), and the groups were then divided into 2 subgroups (n=10) according to surface treatment before and after sintering. The phase compositions of the groups were examined by using an X-ray diffractometer (XRD) with 3 randomly selected specimens from each group. Biaxial flexural strength testing was conducted using a universal testing machine to examine the flexural strength of the zirconia specimens. Two-way ANOVA and post hoc least significant difference tests were performed (a=.05). Results. According to the XRD analysis, no monoclinic phases were determined on the surface of the presintered laser-treated specimens, but tetragonal phases were observed on the surface of the postsintered specimens. Surface treatment type and application stage (presintering to postsintering) have a significant effect on the biaxial flexural strength of the specimens (P<.05). The lowest biaxial flexural values were observed in the Laser group, and postsintered specimens showed higher biaxial flexural strength than presintered specimens (P<.05). Conclusions. Postsintered specimens showed higher monoclinic content than presintered specimens. Laser-treated specimens showed the lowest biaxial flexural strength for both presintered and postsintered specimens. (J Prosthet Dent 2023;129:220.e1-e5)