Debonding of Leucite-reinforced Glass-ceramic Veneers Using Er, Cr:YSGG Laser Device: Optimizing Speed with Thermal Safety

Objective: When laminate veneer restorations require removal, the process is tedious, time-consuming, and potentially damaging to the underlying tooth structure. The purpose of this study was to evaluate the removal of Empress CAD milled laminate veneers on extracted human central incisors by using an Er,Cr:YSGG dental laser while optimizing speed and maintaining thermal safety. Methods and Materials: A total of 22 extracted human incisors were mounted in acrylic blocks. Conservative veneer preparations were made on all samples with a high-speed dental handpiece with a diamond bur and air/water spray. The 22 blocks of IPS Empress CAD were designed and milled into laminate veneers with a CAD/CAM System and luted to the prepared teeth. An Er,Cr:YSGG dental laser was fitted with a handpiece and laser fiber (600-mu m diameter cylindrical fiber, 6 mm in length). Laser parameters were 333 mJ/pulse, 30 Hz, 80% air, 50% water, 600-mu m diameter fiber tip, at a fluence of 885.96 J/cm(2). The laser fiber tip was held directly on the surface of each veneer in contact, perpendicular to the surface, and moved slowly, covering the labial surface while firing. Results: At the laser parameters tested (333 mJ/ pulse, 30 Hz, 80% air, 50% water, 600-mu m diameter fiber tip), the average duration of exposure to completely remove each laminate veneer was 14.16 +/- 0.60 seconds, with a range of 10.75 to 21.25 seconds. The average thickness of each veneer measured at the midfacial was 0.75 +/- 0.03 mm. The mean intrapulpal temperature increase for this period was 0.71 degrees C +/- 0.15 degrees C. Conclusions: A regression model between time and thickness (p<0.0001) proved to be significant. However, the same cannot be said when the same modeling was tested between temperature and thickness. It can therefore be concluded that as the thickness of a veneer increases, more time is necessary to remove a veneer using Er,Cr:YSGG laser energy; however, increasing thickness does not necessarily result in an increase in pulpal temperature. Within the limitations of this study (single restorative material and single luting agent), it can be concluded that removing CAD Empress laminate veneer restorations using an Er,Cr:YSGG laser is reliable and thermally safe, even at an average of 10 W of power at 30 Hz. Additionally, thermal safety is maximized with adequate aerosolized water spray.