Experimental Investigation on the Impact Resistance of CAD/CAM Fabricated Dental Restorations Made of Zirconia Nano Powder Stabilized by Yttrium Oxide

In this study, the impact resistance of CAD/CAM fabricated dental restorations was investigated experimentally. For this purpose, after preparation of zirconia-yttrium oxide nano powder by sol-gel method, hot and cold pressing was performed, followed by 5-axis milling operation. Finally, the impact tests were carried out and the fracture energy was calculated. In this regard, the influence of yttria content, rotational speed of milling machine and curing temperature was evaluated. The obtained results indicated that by increase of the yttria content, the porosity of dental crowns increased, leading to the reduction of the impact strength. Also, it was observed that by increase of the rotational speed, the impact strength decreased. From the viewpoint of the curing temperature; it was found that in the range of 1300-1500 °C, the maximum impact strength was achieved. Finally, SEM images revealed the presence of very short cracks, being in the range of 0.2 - 0.4 µm.