We have been studying an easy bracket debonding method using heating of an
orthodontic adhesive containing thermal expansion
microcapsules. However, heating with a high-temperature heater brings obvious risks of
burns around the oral cavity. Thus, we examined safer and more effective bracket debonding methods. The purpose of this in vitro study was to examine the reduction in debonding strength and the time taken using a bracket bonded with an
orthodontic adhesive containing thermal expansion
microcapsules and a
CO2 laser as the heating method while maintaining safety. Ceramic brackets were bonded to bovine permanent mandibular incisors using bonding materials containing various
microcapsule contents (0, 30, and 40 wt%), and the bond strengths were measured after
laser irradiation for 4, 5, and 6 s and compared with nonlaser-treated groups. Subsequently, the temperature in the pulp chamber during
laser irradiation was measured. After
laser irradiation for 5 or 6 s, the bond strengths of the adhesive containing 40 wt%
microcapsules were significantly decreased to ∼0.40 - 0.48-fold (4.6-5.5 MPa) compared with the nonlaser groups. The mean temperature rise of the pulp chamber was 4.3 °C with
laser irradiation for 6 s, which was less than that required to induce pulp damage. Based on these results, we conclude that the combined use of a
CO2 laser and an
orthodontic adhesive containing thermal expansion
microcapsules can be effective and safe for debonding ceramic brackets with less enamel damage or tooth
pain.