Laser Debonding of ultrathin occlusal veneers fabricated from different CAD/CAM ceramic materials.

Abstract Background Erbium lasers were used to debond restorations safely offering the possibility of their re-use. Since these lasers have a high affinity for water molecules, they are absorbed by resin cement explosive ablation of the cement and thus the restoration debonds. The efficiency of this process depends on many factors including the ceramic type, its chemical composition and thickness. Therefore, this study was designed to test the time taken to debond ultrathin occlusal veneers made of three types of milled ceramic materials and evaluate the integrity of these restorations after debonding. Methods three ceramic types were evaluated in this study: Lithium disilicate (IPS Emax CAD), Highly condensed lithium disilicate (GC initial®LiSi), and translucent zirconia (Katana zirconia STML). Each group consisted of 8 occlusal veneers of 0.5 mm thickness. Samples were cemented to the occlusal surfaces of upper molar teeth. Er;Cr:YSGG laser was applied to the occlusal veneers using the scanning method and time was calculated till debonding. The debonded samples were then inspected under a stereo microscope for possible damage. Numerical data were presented as mean with 95% confidence intervals (CI), standard deviation (SD), minimum (min.) and maximum (max.) values. Normality and variance homogeneity assumptions were confirmed using Shapiro-Wilk's and Levene's tests respectively. Data were normally distributed and were analyzed using one-way ANOVA followed by Tukey's post hoc test. The significance level was set at p < 0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.3.2 for Windows[1]. Results There was no significant difference in debonding time between different materials (p = 0.995). The longest debonding time was found in Katana STML (87.52 ± 20.45) (seconds), followed by Emax (86.94 ± 20.63) (seconds), while the lowest value was found at LiSi initial (86.14 ± 25.16) (seconds). In terms of damage to the debonded veneers, The Emax and zirconia samples showed no damage. However, 40% of the LiSi samples fractured during debonding, and 20% exhibited cracks. Only 40% of the LiSi samples were sound after debonding. Conclusion Er;Cr:YSGG laser can be used efficiently to remove ceramic occlusal veneers. However, its effect on LiSi restorations needs further research.