Abstract
Purpose To address the following null hypothesis: when the Rocatec bonding system is used, the various sizes of aluminum oxide particles used to roughen the surface area of the commercially pure (CP) titanium prior to bonding to autopolymerized resin have no effect on the average shear bond strength. Materials and Methods One hundred specimens were randomly allocated to five equally sized groups: Ti-no air abrasion (group A), Ti-air-abraded with 50 mu m (group B), Ti-110 mu m (group C), Ti-250 mu m (group D), and Co-Cr-50 mu m (group E) grain-size aluminum oxide. Rocatec Plus tribochemical coating was applied to all of the specimens, followed by a RelyX primer and Sinfonyopaquer. Autopolymerized denture base resin was then bonded to the treated titanium surfaces. All specimens underwent thermocycling (10,000 cycles), shear bond testing, and mode of failure examination under stereoscopic microscopy. Results The average bond strength of group D (250 mu m) was significantly different compared to all other groups, except group C (p = 0.057, trending significance). The average bond strength of group D was substantially higher than that in the other groups (p < 0.01). The weakest bond was observed when the specimens did not receive any air abrasion (group A). Maximum load (N) showed the same significant results as the shear bond strength at maximum load (MPa). The average extension at maximum load (mm) and the time at maximum load(s) for group A were significantly different than that of all other groups. Group A had lower average values than any other group (p = 0.003). More cohesive and mixed, rather than adhesive, modes of failure were observed as the size of the aluminum oxide particles increased. Conclusion When the Rocatec system is used, using a combination of chemical and micromechanical adhesion is essential for the success of the bond between the autopolymerized acrylic resin and CP Ti. The micromechanical interlock can be improved significantly when the Ti surface is air abraded with larger particles (250 mu m) than the currently used alumina particle size.