Evaluation of the different surface treatments (glazing or mechanical polishing) effect on the corrosion rate of two CAD/CAM restorative ceramics types

Abstract

The multiphase microstructure of dental ceramic restorative materials leads to complex corrosion states. Because each phase reacts separately to the chemical characteristics of the environment. In this study, we investigated the effect of different surface treatments (mechanical polishing or glaze) on the amount of corrosion of two types of CAD/CAM ceramic restorations. Materials and methods In this laboratory study, 20 ceramic block samples (ZLS (n=10) and LDS (n=10) with length and width of 12×7 mm and color A2 were prepared. The samples were placed in ultrasonic device to remove residual particles and surface contamination. Then it was sintered and completely crystallized by porcelain furnace. To standardize the process and homogenize the surface of the samples before work, all the samples were polished with a low speed handpiece and water cooling, by silicon carbide sandpaper, by one person and for 60 seconds for each sample. The samples of each type of ceramics were randomly divided into two equal groups according to the method of surface treatment that was applied on their surface (polishing or glaze). The samples of group one (LDS polishing) and group three (ZLS polishing) were polished by polishing kit. The samples of group two (LDS glaze) and group four (ZLS glaze) were glazed in the furnace. After washing and drying and measuring the initial weight, the samples were immersed in 4% and 40% acetic acid solution at 80Ċ for 16 hours, and after cooling and washing and drying again, the final weight the samples were measured. The final results of the amount of Corrosion were reported as the difference between the final and initial weight, divided by the surface area of the samples with a mg/cm2 scale. In order to avoid the bias of the results, the technician and the student weighing the weight were blinded to the groups. Data were analyzed by statistical software SPSS.21 and statistical tests Two-way and one-way analysis of variance and independent t- test. Results The results of the pilot study of the current research showed that 4% acetic acid does not cause any change in the corrosion of the study restorations, so we used a concentration of 40% to check the corrosion. In the present study, in ZLS restoration, the amount of corrosion in glaze operation was (0.0098±0.0036 mg/cm2) and in the polishing method was (0.0062±0.0039 mg/cm2), which states that the type of surface treatment had no effect on the amount of corrosion. Also, in LDS restoration, the amount of corrosion in polishing operations was (0.0105± 0.0057 mg/cm2) and in glaze method (0.0086 ± 0.0033 mg/cm2), which indicates that the amount of corrosion was similar to the surface polishing method. The results of the present study showed that the type of surface treatment (glaze and polishing) and the type of restoration (LDS and ZLS) had no effect on the amount of corrosion. Conclusion The type of surface treatment (glaze and polishing) and the type of restoration (LDS and ZLS) had no effect on the amount of corrosion.