Removal of two different CAD/CAM ceramics with er: Yag laser evaluation of the time and the pulpal temperature

Removing all-ceramic restorations used with adhesive cements is extremely difficult due to strong bonding. Laser transmitted into the ceramic is used for debonding. This study is conducted to evaluate the debonding time and pulpal temperature caused by the Er: YAG laser. 120 extracted maxillary central teeth were prepared at the enamel level. Leucite and lithium disilicate CAD / CAM ceramic blocks were used in this study. Specimens from these blocks were fabricated with size of 5 mm x 12 mm and a thickness of 1 mm (60 specimens from each leucite and lithium disilicate). Ceramic blocks were cemented on the enamel surface using light cure adhesive cement. Each group was divided into 3 subgroups according to laser parameters (n = 20) (1 W - 2 Hz - 500 mJ, 2W - 15 Hz - 135 mJ, 3 W - 10 Hz - 300 mJ). Thus, 6 groups were obtained with different ceramic and laser parameters. During debonding, a force of 15 N was applied to each group. Pulpal temperature was measured with a thermocouple placed in the pulp chamber. Obtained data were analysed by using the Kruskal Wallis and Dunn multiple comparison tests. Debonding time was found in 3W groups the shortest. There was no debonding in 15 minutes in 1W groups. Pulpal temperature difference was found in the groups of maximum 1W and the lowest 2W. When the same wattage was used, it was observed that different ceramic types did not statistically affect the removal time and pulpal temperature difference (p <0.05). Based on the data, a significant relationship was observed between the method and the temperature difference greater than 5.5 °C (p = 0.012). When the ratios were compared with the Bonferroni correction, a significantly higher rate of teeth with a temperature higher than 5.5 °C was found in 1 watt groups (p = 0.026). Keywords: CAD / CAM, Debonding, Dental ceramics, Er: YAG laser, Pulpal temperature