Effect of hydrofluoric acid concentration and etching time on the surface roughness of CAD/CAM ceramics

Introduction: Dental ceramics are considered as materials that can restore the appearance of natural teeth. Etching the inner surface of a ceramic restoration with hydrofluoric acid (HF) followed by using a silane coupling agent is a well-known and recommended method to increase the bond strength. The aim of etching on ceramic structure is to enhance the surface roughness (Ra) and energy and to cleanse the bonding area. The aim of this study was to evaluate the effect of different HF concentrations and etching times on the Ra of IPS e.max CADTM and Vita mark IITM. Materials &Methods: Two HF concentrations (5% and 10%) and three etching times (20, 60 and 120 seconds) were evaluated. Etched patterns were observed by scanning electron microscopy (SEM) and Ra was measured using atomic force microscopy (AFM). Surface element analysis was performed using energy dispersive X-ray spectroscopy (EDAX). Data were analyzed on SPSS 20 using ANOVA and T-test. Results: The Ra had no significant difference among various Vita mark IITM specimens (P=0.973). Among IPS e.maxTM specimens etched with 5% HF, the AFM results showed that 20-s etching time had the lowest Ra and among those etched with 10% HF and 120-s etching time had the most Ra. In IPS e.maxTM specimens etched with acid for 20 s, a significant difference was observed in Ra of 5% and 10% acid concentrations (5% HF lower than 10% HF) (p=0.012). Conclusion:  Among IPS e.maxTM specimens etched with 5% and 10% HF, increasing the etching time lead to higher Ra. For both IPS e.maxTM and Vita mark IITM, 20-s etching with 5% HF provides acceptable Ra for the bond.