Ceramics demonstrate chemical stability, excellent biocompatibility and good mechanical and optical properties. However, catastrophic failure still occurs and the repair of those failed restorations is often problematic. In contrast, resin composites are easier to operate and repair, but with less desirable wear, biocompatibility and mechanical properties. Polymer based ceramics (PBC) with various polymer matrix compositions and different percentage of ceramic fillers have been developed to provide better mechanical properties, lower discoloration rates, and higher wear resistance than the conventional resin composites. They are currently available as monolithic blocks fabricated for CAD/CAM systems. However, little is known on their elastic and viscoelastic properties and their mechanical behaviours.
Materials & Methods:
Twenty five bar shaped specimens (12x4x2 mm) were prepared from five different PBC blocks. The surface morphology of the PBC was studied by Scanning Electron Microscopy (SEM). Micro hardness of the specimens was measured using Vicker indenter under a load of 100 gf for 10 s at room temperature. Nano hardness was tested under a 50 g load with a 10 s pause/dwell. The hardness results obtained by micro indentation and nano indentation of all 5 test groups were compared using one-way ANOVA (p ? 0.05).
The mean nano hardness values of the studied PBC ranged from 0.32 to 7.05 GPa. For the micro hardness, the mean values ranged from 25.8 to 499.9 HV. Mean Elastic modulus ranged from 4.66 to 76.40 GPa. Statistically significant differences were found between the tested materials for all the studied mechanical properties. Positive correlation between the amount of ceramics (in wt%) and both micro hardness nano hardness data were observed.
Different PBC materials show different surface morphology of fillers in different size, shape and density. Micro hardness and nano hardness of the studied PBC materials increased systematically with an increase in filler loading.