Wear resistance of crowns made from different CAM/CAD materials

The aim of this laboratory study was to evaluate the wear resistance of crowns made from current computer-aided design and computer-aided manufacture (CAD/CAM) materials. In addition, the abrasion of the steatite antagonist against these materials was compared.

Identically shaped crowns of lithium disilicate, zirconia-reinforced lithium disilicate and a polymer-infiltrated ceramic network (PICN) were fabricated with an occlusal thickness of 1.5mm and a lateral wall thickness of 1.2mm (n=8). The crowns were cemented with a dual-polymerizing luting resin on composite resin dies. Using spherical steatite antagonists, all specimens were loaded with 49N for 1,200,000 cycles in a mastication simulator with additional thermocycling. After 120,000, 240,000, 480,000, 960,000, and 1,200,000 cycles, precision impressions were made and investigated with a laser scanning microscope. The vertical and volume substance loss was measured. Additionally, the substance loss of the antagonists was evaluated after 1,200,000 loading cycles.

No significant difference (p>0.05) was found in the median volume loss of the test materials after 1,200,000 cycles (lithium disilicate: 0.405mm³, PICN: 0.362mm³, zirconia-reinforced lithium disilicate: 0.340mm³). The vertical substance loss of PICN (157μm) was significantly lower (p≤0.05) than that of lithium disilicate (201μm) and zirconia reinforced lithium disilicate (191μm). However, the substance loss of steatite against zirconia-reinforced lithium disilicate (0.191mm³) was significantly lower (p≤0.05) than against lithium disilicate (0.296mm³) and PICN (0.531mm³).

All three CAD/CAM materials showed wear resistance that seems appropriate for clinical application. Also, the abrasion of the antagonist looks promising.