Laser irradiation effects on structural, morphological and mechanical properties of ZirCAD dental ceramic

In the present study, the effects of laser irradiation on microstructure, morphology and hardness of yttria-stabilized tetragonal zirconia (ZrO2) commercially known as ZirCAD are examined. Three specimen discs were cut from the ZirCAD block. After polishing two of them were irradiated by Nd: YAG pulsed laser, with 100 and 150 laser pulses respectively and the remaining one unexposed specimen was kept as a standard. The XRD analysis confirmed that no phase change occurred after laser irradiation however an increase in dislocation line density (DLD) was observed. The surface morphology was observed by optical and scanning electron microscopy (SEM). Laser irradiation initially caused the upper surface to melt therefore resulting in a smooth and glazed surface. Further increase in laser pulses produced porosity within the sample. The optical microscopy revealed that the crater size decreased and the heat-affected zone increased with the increased number of laser pulses. Vickers hardness was employed to observe the hardness of unirradiated and irradiated samples and a 32% increase in hardness was observed when the material was irradiated by 100 laser pulses. The glazed surface exhibited more hardness as compared to the unirradiated and porous surfaces. The improved surface morphology and high hardness achieved in this work with laser irradiation for ZirCAD ceramic are quite beneficial in dental applications.