Effects of alumina-blasting for a CAD/CAM resin block on adhesion

Objectives: The aim of this study was to evaluate microtensille bond strengths (µTBS) of two different resin cements to a CAD/CAM resin block with alumina-blasting under different air pressure.
Methods: A CAD/CAM resin block (Lava Ultimate, 3M ESPE) was cut into six slices with 2 mm thickness. Prior to cementation, the CAD/CAM resin block slices were untreated or alumina-blasted using 0.1 MPa or 0.2 MPa with 50 µm alumina sand. The CAD/CAM resin block specimens were cleaned with 99 % ethanol for 3 min in an ultrasonic bath, followed by the application of Scotchbond Universal (3M ESPE). The CAD/CAM resin block slices were then cemented to bovine dentin ground with #600 SiC using Rely X Ultimate (RXU) or Rely X Unicem2 (RU2) (3M ESPE). All the specimens were stored in distilled water for 24 h, cut into beams (1×1 mm). The beams were then subjected to µTBS test (n=25). The µTBS values were analyzed statistically by two-way ANOVA and t-test Bonferroni correction (p=0.05)
Results: RXU showed significantly higher µTBS than RU2 with any surface conditioning. Pre-treatment using alumina-blasting significantly increased the µTBSs in RXU (p<0.05). In RU2, 0.2 MPa alumina-blasting group showed significantly higher bond strength than other groups (p<0.05).
Conclusions: Alumina-blasting with appropriate pressure enhance the bond strength between CAD/CAM resin block and dentin. RXU showed stable bonding performance between CAD/CAM resin block and dentin compared with RU2.