MECHANICAL CHARACTERISATION OF CAD/CAM DENTAL MATERIAL AND NATURAL TEETH

The aim of this study was to investigate the hardness and the fracture toughness of dental ceramic materials by means of the Vickers indentation technique. One type of the most common commercial restorative dental ceramic materials fabricated using CAD/CAM system, leucite-based glass-ceramics, was selected for the study and comparison with laboratory synthetised leucite composites and natural teeth. The obtained results show that the measurement of hardness and fracture toughness depends on the used conditions (the indenter geometry, the indentation load and the duration of the maximal force), the morphology of the polished surface, the type of crack system developed or measured indentations and, of course, on the empirical equation (Casellas, Shetty et al., Niihara et al., Lankford, Niihara, Laugier, Nakahira) used for calculation of the fracture toughness. The results proved that the values of the Vickers hardness of our laboratory prepared leucite composites (7.76 - 8.92 GPa) are very close to the values of commercial IPS Empress blocks. The Vickers indentation test was verified as a suitable method for the evaluation of the fracture toughness of small sized samples of leucite-based dental composites when using a low indentation load of 9.807, 19.61, 29.42 and 39.23 N and an indication of Palmqvist cracks.