RESUMO
BACKGROUND AND OBJECTIVES: The removal of porcelain veneers using Er:YAG lasers has not been previously described in the scientific literature. This study was designed to systematically investigate the efficacy of an Er:YAG laser on veneer debonding, possibly without damage to the underlying tooth, and preservation of the veneer integrity. STUDY DESIGN/MATERIALS AND METHODS: The Fourier Transform Infrared Spectroscopy was used on 10 flat veneer samples (IPS Empress Esthetic, e.max Press HT) to assess which infrared laser wavelengths transmits through a veneer. Additionally, Fourier Transform Infrared (FTIR) spectra for a bonding cement (RelyX) were obtained. Consequently, Er:YAG laser energy transmission (wavelength 2,940 nm, 10 Hz repetition rate, pulse duration 100 µseconds at 133 mJ/pulse) through different veneer thicknesses was measured. Twenty-four veneers were bonded to freshly extracted and prepared incisors. The energy necessary for debonding was determined and then the veneers were debonded with the laser. Time needed for total debonding was measured and possible damage to the underlying tooth structure was assessed by light microscopy. RESULTS: While the veneer materials did not show any characteristic water absorption bands in the FTIR, the bonding cement showed a broad H(2) O/OH absorption band. The veneers transmitted between 11.5% and 43.7% of the incident Er:YAG energy with Emax transmitting twice the energy as EE at comparable thicknesses. Initial signs of cement ablation occurred at 1.8-4.0 J/cm(2) with the fiber tip positioned at a distance of 3-6 mm from the veneer surface and 133 mJ output energy. All 24 bonded veneers were completely removed with an average removal time of 113 ± 76 seconds. Underlying tooth structure was not damaged. The debonding mainly occurred at the cement/veneer interface. None of the Emax veneers fractured during debonding, while 36% of the EE did. CONCLUSION: Er:YAG laser irradiation effectively debonds porcelain veneers while preserving tooth structure. Maintaining veneer integrity possibly depends on the flexure strength of the veneer porcelain.
