Influence of Ambient Air and Different Surface Treatments on the Bonding Performance of a CAD/CAM Composite Block

Purpose: To evaluate the bond strengths of time elapsed after sandblasting with alumina particles on a CAD/CAM composite block treated with different surface conditioning methods. Materials and Methods: A CAD/CAM composite block (CCB) was cut into 72 slices of approximately 2 mm thickness. The CCB slices were divided into three groups according to sandblasting pressure (0.1 MPa, 0.2 MPa, or untreated), and then divided into two subgroups according to the time elapsed after sandblasting: same-day or one-week dry storage under controlled laboratory conditions before cementation. Surface roughness was observed by confocal laser microscopy (CLSM) (n = 20); then the wettability of the CCB surfaces was examined using a contact angle (CA) measuring device on a droplet of deionized water (n = 12). Next, CCB slices were divided into three subgroups according to the surface treatment: Clearfil Ceramic Primer (CP), Clearfil Universal Bond (UB), or a mixture of Clearfil Porcelain Bond Activator and Clearfil tri-S Bond ND Quick (NDP). All CCB slices were then cemented with Panavia V5 and stored at 37°C in distilled water for 24 h and cut into sticks (n = 10). The sticks were subjected to microtensile bond strength (µTBS) testing, and failure mode analysis was performed using scanning electron microscopy. The µTBS results were subjected to 3-way and 2-way ANOVA (α = 0.05). Results: All groups showed a statistically significant increase in wettability accompanied by decreased µTBS after one week; however, the UB group exhibited stable performance after one week. Conclusion: The time elapsed after sandblasting with alumina particles affects the bond strength, but it had no significant effect on the UB group. Keywords: alumina particles, CAD-CAM, composites, microtensile bond strength, silane, sandblasting, wettability