A modified laser pretreatment of zirconia for bonding with porcelain

Abstract

OBJECTIVES: The aim of this study was to evaluate the possibility of application of laser irradiation on the surface of zirconia to increase bond strength between zirconia and veneering porcelain instead of conventional sandblasting METHODS: One hundred and sixty zirconia discs were cut from commercial cylindrical zirconia blocks. After being densely sintered, all the zirconia discs were randomly divided into four groups and modified with one of the following surface treatments: control (without any treatment), sandblasting, sandblasting followed by regeneration firing, and laser irradiation. After cleaning procedure, veneering porcelain materials were fired on these zirconia specimens with a cylindrical shape according to the manufacturer’s instructions. Each group of the specimens were further divided into two subgroups; one for the evaluation of initial SBS, the other half was stored in water at 37°C and tested the SBS after one month. The data were statistically analyzed by using one-way analysis of variance (ANOVA) (α=0.05). The changes in crystalline structure at zirconia surfaces were recorded by X-ray diffractometry (XRD) technique. RESULTS: Statistically significant differences in initial SBS were found among these four groups, with the highest SBS (32.1±7.5 MPa) for the laser group and the lowest mean value (24.82±6.7 MPa) for the control group, and no significant differences were found between initial SBS and aged SBS for each group after the water storage. XRD analysis showed that sandblasting led to the transformation from tetragonal phase (T) to monoclinic phase (M) and such change was then reversed by regeneration firing. Laser surface treatment did not lead to T→M crystallographic transformation on zirconia surface. CONCLUSIONS: SBS between zirconia and veneered porcelain could be increased by both sandblasting and laser irradiation methods. Sandblasting as a pre-treatment for zirconia might be replaceable with modified laser irradiation.