OBJECTIVE: To investigate the effects of CO(2) laser debonding of a ceramic bracket on the mechanical properties of tooth enamel. MATERIALS AND METHODS: Fifty-three human premolars were used in this study. The temperature changes of cross-sectioned specimens during laser irradiation were monitored with an infrared thermographic microscope system. Different laser output settings (3, 4, 5, and 6 W) were compared. The shear bond strength of brackets after laser irradiation was measured for specimens bonded with a conventional etch and rinse adhesive or with a self-etching adhesive, and the adhesive remnant index score was calculated. The hardness and elastic modulus of cross-sectioned enamel after laser irradiation were investigated by the nanoindentation test. Data were compared by one-way and two-way analysis of variance, followed by the Scheffé test. RESULTS: The temperature of enamel increased by about 200 degrees C under CO(2) laser irradiation with a relatively high output (5 and 6 W), and a temperature increase of about 100 degrees C to 150 degrees C was seen under laser irradiation with a low output (3 and 4 W). The bracket shear bond strength decreased under all laser irradiation conditions. The hardness and elastic modulus of enamel were not affected by CO(2) laser debonding. CONCLUSION: CO(2) laser debonding may not cause iatrogenic damage to enamel.
OBJECTIVE: To investigate the effects of CO(2) laser debonding of a ceramic bracket on the mechanical properties of tooth enamel. MATERIALS AND METHODS: Fifty-three human premolars were used in this study. The temperature changes of cross-sectioned specimens during laser irradiation were monitored with an infrared thermographic microscope system. Different laser output settings (3, 4, 5, and 6 W) were compared. The shear bond strength of brackets after laser irradiation was measured for specimens bonded with a conventional etch and rinse adhesive or with a self-etching adhesive, and the adhesive remnant index score was calculated. The hardness and elastic modulus of cross-sectioned enamel after laser irradiation were investigated by the nanoindentation test. Data were compared by one-way and two-way analysis of variance, followed by the Scheffé test. RESULTS: The temperature of enamel increased by about 200 degrees C under CO(2) laser irradiation with a relatively high output (5 and 6 W), and a temperature increase of about 100 degrees C to 150 degrees C was seen under laser irradiation with a low output (3 and 4 W). The bracket shear bond strength decreased under all laser irradiation conditions. The hardness and elastic modulus of enamel were not affected by CO(2) laser debonding. CONCLUSION: CO(2) laser debonding may not cause iatrogenic damage to enamel.