Wear Patterns of Adhesive Interfaces over Different Materials

Purpose: The aim of this in vitro study was to investigate differences in surface wear of enamel-material and dentin-material bonded interfaces obtained from upper molars samples and subjected to cycling occlusal load. Methods: Forty-eight flat specimens of enamel-material and dentin-material bonded interfaces were prepared using different restorative materials with both CAD-CAM techniques and direct techniques. After the bonding and cementation procedures specimens were tested with a chewing machine with a stainless-steel ball on flat sliding contact (20N loads, 50.000 cycles). Wear analysis and comparison of the enamel or dentin substrates and the three restorative materials was performed using a 3D profilometer and analyzed with ANOVA test and post-hoc comparison procedures. Finally worn surfaces were examined with optical microscopy. Results: Statistical analysis after simulated chewing cycles identified a significant influence of the factor “substrate” (p<0.05) and of the factor “restorative material” (p<0.05). The enamel results in being more wear resistant than dentin, and also more resistant than all the restorative materials tested. Considering the materials, the most severe wear loss was observed with micro-hybrid composite paste. CAD-CAM materials showed a wear rate significantly better both in association with enamel and dentin. An interesting wear pattern was found at the bonded interface level and the oval shapes obtained from the profilometer images underlined a repetitive wear pattern with the central zone more consumed and decreasing depth moving towards the perimeter. Initials signs of cracks were showed in enamel interfaces at the optical microscopy analysis. Conclusions: Both the dental substrate and the restorative material significantly affect the wear behavior of a toothmaterial interface after cyclic fatigue. Thus, the initial null hypotheses were rejected.