Ultrasonic Cleaning Influences Silica Coated Zirconia Bond Strength

Objectives: The purpose of this study was to evaluate influence of ultrasonic cleaning of surface of zirconia-based ceramics that was coated with silica on bond strength to resin luting material. Methods: A total of forty zirconia-based ceramic (Lava, 3M ESPE) specimens were randomly divided into two main groups; air abrasion and silica/silane coated. Specimens of silica/silane coated group were cleaned with distilled water using ultrasonic cleaner after tribochemical silica coating (Rocatec, 3M ESPE) and were further divided into three groups by cleaning duration (1 and 5minutes and without cleaning). A luting material (PanaviaF 2.0, Kuraray Medical), 2mm thickness and 3.6mm in diameter, was processed against all specimens, after applying silane coupling agent (ESPE Sil, 3M ESPE) except for air abrasion group. Specimens were stored in distilled water at 37degrees C for 24hours and shear bond strength values were determined at a crosshead speed of 0.5mm/min. Data was statistically analyzed using one way ANOVA and Student-Newman-Keuls method. Impacts of surface treatment were evaluated employing SEM. Energy dispersive X-ray spectroscopy (EDXS) analysis was carried out to analyze element distribution of treated surface. Results: Mean shear bond strength values for silica/saline without cleaning group was 9.6MPa and was significantly higher than other three groups; air abrasion (8.0MPa) and silica/silane with ultrasonic cleaning for 1 minute and 5minutes groups (8.1MPa, 7.2MPa)(P<0.05), while these three groups did not show significant difference value one another. All fractured surface of silica/saline with ultrasonic cleaning groups (1 and 5minutes) showed adhesive failure-mode, while some of air abrasion and silica/saline without ultrasonic cleaning groups obtained mixed-mode. SEM image suggested visible difference among treatment methods. Decrease of silica by ultrasonic cleaning was suggested from EDXS analysis. Conclusions: Ultrasonic cleaning of tribochemical silica coated zirconia-based ceramics decreases effectiveness of silica/silane coating on adhesive strength to resin luting material.