Effect of degradation of acidic pH on surface roughness and micro-hardness of restorative CAD-CAM materials

Abstract

The aim of this study was to test the impact of exposure to acidic condition on the properties of CAD/CAM dental ceramics. Earlier research has indicated that immersion in acid has caused increased surface roughness of dental ceramics; however further evaluation using new materials seems necessary. Materials and Methods: Three commercially available ceramics were chosen for this study: Zirconia-reinforced lithium silicate (Celtra Duo, Dentsply), Resin matrix ceramic (VITA Enamic, VITA Zahnfabrik, Lithium Disilicate glass ceramic (IPS e.max CAD, Ivoclar Vivadent AG). The specimens (10 × 1 mm discs) were cut, thermally treated as required, and polished. All specimens of each group were divided into two groups and were immersed in a 10 ml of 5% hydrochloric acid (HCl) and placed into an incubator at 37 °C for 45 hours or 91 hours. The surface roughness average (Ra) of the specimens was measured using a 3-D optical interferometer before the storage period (baseline), after 45 hours, and after 91 hours of exposure to HCl. The microhardness of specimens was measured by Vickers test as well. Results: In Celtra Duo and IPS e.max CAD blocks, there was no statistically significant difference between the mean roughness at different evaluation times. While 45 hours of immersion in acid increased the surface roughness of the Enamic block. Also, 45 and 91 hours of acid immersion reduced the microhardness of Enamic and Celtra blocks, respectively, while it has no significant effect on the microhardness of IPS e.max CAD. Celtra had the highest microhardness and Enamic had the lowest microhardness at all times. Conclusion: Acidic environment increases the surface roughness and decreases the microhardness of Enamic blocks while it has no effect on the roughness and microhardness of IPS e.max CAD blocks. The acidic environment also reduces the microhardness of Celtra blocks while not affecting the surface roughness.