Microhardness evaluations of CAD/CAM ceramics irradiated with CO₂ or Nd:YAP laser

Abstract : Background and aims. The aim of this study was to measure the microhardness values of irradiated computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics surfaces before and after thermal treatment. Material and Methods. Sixty CAD/CAM ceramic discs were prepared and grouped by material, i.e. lithium disilicate ceramic (Emax CAD) and zirconia ceramic (Emax ZirCAD). Laser irradiation at the material surface was performed with a carbon dioxide laser at 5 Watt (W) or 10 W power in continuous mode (CW mode), or with a neodymium:yttrium aluminum perovskite (Nd:YAP) laser at 10 W on graphite and non-graphite surfaces. Vickers hardness was tested at 0.3 kgF for lithium disilicate and 1 kgF for zirconia. Results. Emax CAD irradiated with CO2 at 5 W increased microhardness by 6.32 GPa whereas Emax ZirCAD irradiated with Nd:YAP decreased microhardness by 17.46 GPa. Conclusion. CO2 laser effectively increases the microhardness of lithium disilicate ceramics (Emax CAD).