The development of dental CAD/CAM system has made metal-free ceramic restorations more available to patients. Silane coupling treatment is an essential clinical process to achieve reliable and good adhesion with silica-based indirect restoratives. However, long-term water-storage causes the hydrolysis of silane coupling agents and decreases the bond strength. The aim of this study was to examine the effect of additional treatments including photochemical treatments on silane coupling performance in ceramic restorations. The influence of water-storage periods (1d: one day, 1m: one month, and 3m: three months) for the silanized surface of CAD/CAM ceramic restorations was also investigated. In addition, bonding reliability was evaluated as a qualitative measure in order to characterize the bond strength of CAD/CAM restorations. The micro-tensile bond strength (μ-TBS) was measured to explore the benefits of additional photochemical treatments (UV: ultraviolet and VL: visible light irradiations) on silanized surfaces, compared to non-additional treated (CO) and dry heating (DR) conditions. In the CO specimens, μ-TBS decreased in the order of 1d > 1m > 3m. However, in DR, UV, and VL additional treatments, no significant differences could be observed in the 1d, 1m, and 3m groups. The Weibull modulus and 10% failure probability values of the UV and VL specimens were inclined to be significantly greater than those of CO specimens, regardless of the water-storage period. These findings reveal that additional photochemical treatments had a successful effect to improve the bond strength and bonding reliability of the CAD/CAM restorations, when compared to CO and DR conditions.
Keywords: CAD/CAM restorations; Micro-tensile bond strength; Photochemical treatment; Silane coupling treatment; Water-storage.