Adhesion procedure for CAD/CAM resin crown bonding: Reduction of bond strengths due to artificial saliva contamination

PURPOSE: The present study aimed to elucidate how saliva contamination affects microtensile bond strength of resin cement to CAD/CAM resin blocks and identify a decontamination method that can restore original bond strength. METHODS: The KATANA AVENCIA block (Kuraray Noritake Dental) was sandblasted on the adherend surface (P-Co group). Then, the block was contaminated with artificial saliva (Saliveht Aerosol, Teijin). Air dry (N-Co), sandblasting (Sb) and phosphate acid cleaning (AT) groups were prepared. After silane treatment, PANAVIA V5 (Kuraray Noritake Dental) was built up and microtensile bond strength (μTBS) was measured after immersion in water (n=24 per group). Scanning electron microscopy (SEM) analysis, surface roughness and contact angle measurement of each surface were performed. RESULTS: The P-Co group showed the highest μTBS value, and bond strength was significantly lower in the N-Co group than the other groups (P<0.001). In all groups, decreased bond strength resulted from long-term water storage. In the N-Co group, a contaminated layer was observed on the surface by SEM and the contact angle was significantly smaller than the other groups (P<0.001). In Sb and AT groups, μTBS values that were reduced by artificial saliva contamination significantly increased but did not recover to P-Co group values (P<0.001). SEM showed no morphological difference between P-Co, Sb and AT groups. The Sb group showed increased surface roughness. CONCLUSION: The long-term durability of bonds between CAD/CAM resin blocks and luting agent cement was significantly reduced by artificial saliva contamination. However, sandblasting or phosphoric acid cleaning can recover bonding effectiveness by 75-85%.