ABSTRACT
This study evaluated the temperature in the bonding composite and in the pulp chamber, the shear bond strength after the irradiation of CO2 lasers, and the Adhesive Remnant Index (ARI) after debonding of ceramic bracket. A hundred and five premolars were used: 30 to evaluate the temperature and 75 to test the resistance to shear and the ARI. To assess the temperature, different irradiation times (3 and 5 s), pulse duration (0.001 and 0.003 s), and output power (5, 8, and 10 W) were tested (total of 12 groups). During all the irradiation, specimens were immersed in thermal bath water at 37 °C. In the test and ARI evaluation, premolars were divided into five groups (n = 15) and were submitted to the following regimens of CO2 laser irradiation: I (5 W, pulse duration = 0.01 s, application time = 3 s), II (5 W, 0.03 s, 3 s), III (8 W, 0.01 s, 3 s), and IV (1 0 W, 0.01 s, 3 s). Group C (control) was not subjected to irradiation. ARI was measured after debonding of the bracket. Following irradiation of the lasers, the pulpal temperature was not higher than 5.5 °C in four of the study groups. Results were submitted to the ANOVA and Duncan's test. CO2 laser irradiation regimen IV was one in which the strength of debonding is 7.33 MPa. Therefore, CO2 laser may aid removal of ceramic brackets; it decreased the bond strength without increasing the excessive temperature excessively.
