Microtensile Bond Strength of Adhesively Bonded CAD/CAM Materials to Dentin

Objectives: To evaluate the effect of different resin cements, type and surface treatments of CAD/CAM materials on the microtensile bond strength (µTBS) to dentin.

Methods: Two types of CAD/CAM blocks (nano ceramic Lava Ultimate, LVU; 3M ESPE and composite Cerasmart, CS; GC) were cut in slabs of 4mm thickness, sandblasted and then divided into 5 groups according to the following surface treatments: Group 1:Silane primer (Kerr), Group 2:Silane primer+Optibond XTR adhesive (Kerr), Group 3:Optibond XTR adhesive, Group 4:RelyX Ceramic Primer+Single Bond Universal (3M ESPE) and Group 5:Single Bond Universal. Then LVU and CS specimens were bonded to the mid coronal dentin surfaces of 50 noncarious human third molars using either Nexus3 with Optibond XTR (Kerr; n:30) or RelyX Ultimate with Single Bond Universal (3M ESPE; n:20) according to the manufacturer’s instructions. All the specimes were thermocyled for 5000 (5°C/55°C) cycles, sectioned into 1mm² sticks and µTBS (MPa) was determined using an Universal testing machine (Instron). Data were analyzed with three way ANOVA and post-hoc Tukey’s tests (p<0.05).

Results: µTBS was significantly influenced by the type of CAD/CAM material (p<0.0001) and by different surface treatments (p<0.0001) however not by the type of resin cement (p>0.05). Regardless of the surface treatments and resin cements, bonding of CS to dentin was significantly higher than bonding of LVU. For LVU and CS the highest bond strentgths were obtained with Group 2 (28.27±11.79; 45.27±13.69), Group 4 (28.85±7.58; 48.6±11.83) and Group 5 (27.82±5.78; 45.13±7.16) while the lowest with Group 1 (17.33±4.46; 27.63±5.12) and Group 3 (18.56±5.6; 29.72±5.49) which were not significantly different from each other in each CAD/CAM material (p >0.05).

Conclusions: Composite CAD/CAM blocks appear more bonding-receptive than resin nano ceramic blocks. Chemical adhesion using silane or an universal adhesive following sandblasting are effective surface treatment methods for CAD/CAM blocks.