Ultrafast Laser Induced Non-Invasive Veneers Debonding In Dental Restoration

The purpose of this study is to explore the feasibility of ultrafast laser debonding of ceramic veneers. Samples of restored teeth were prepared with a general clinical method, the linear polarized laser beam was generated by an ultrafast laser system. Optical property was tested with a UV-Vis spectrometer. Temperature on the ceramic surface was measured by an infrared camera. After debonding, the microstructures were characterized by the scanning electron microscope. Laser scanning confocal microscope was used to measure the surface morphology. Raman spectra measurement was conducted with Renishaw inVia Qontor. Carbonization and micro-cracking were two typical reactions in the adhesive layer, and the bond strength was thus largely weakened. It normally exhibited smaller shear strength under carbonization mode, which can be down to 1.2 MPa. Within a wide range of defocusing distances, the bond can be broken with low forces, indicating a high tolerance in spatial control of laser beam. Based on the thermal conduction originated from the laser focus, temperature in dental pulp can be controlled by adjusting the laser parameters and scanning strategy. As proposed, the temperature was below 41 ℃ under an alternate scanning path, and both carbonization and micro-cracking modes can occur with resultant shear strength 2.3 MPa and 4.1 MPa, respectively. This ultrafast laser debonding method exhibits a facile and fast way to debond the ceramic veneer with minimal damage in dentin, which shows great potential in non-invasive dental restoration.