Objective    To explore the best parameters of impulse Nd:YAG laser-aided debonding for ceramic bracket.    Methods    The removal of ceramic bracket from enamel surface by laser irradiation was investigated in vitro. Fifty-four premolars were used to test the tensile strength and 32 premolars for pulp cavity temperature test. The results were compared according to the laser setting (output power: 0

2

3

5 W; time: 2

4 s)

the average force (830.3

556.5 g) necessary to break the adhesion between ceramic bracket and tooth

the different edible pigment on bracket surface (black or not).     Results    The bonding strength of ceramic bracket was significantly reduced by laser irradiation

averagely by 48%. The average bonding strenth in the six groups for tensile strength test was of statistical difference (P0.05). The pulp cavity temperature was enhanced after laser irradiation

and the gained temperature among the 4 groups for temperature test was statistically different (P0.05). When output power was 3 W and time was 2 s

the pulp cavity temperature rose by 3.71 ℃; if the ceramic brackets were blackened

the temperature rose by 3.94 ℃. Laser irradiation could remove the adhesive on the surface of bracket and tooth. The debonding time was associated with laser output power and edible pigment on the bracket surface.     Conclusion    The bonding strength of ceramic bracket was statistically reduced after laser irradiation and the best parameters of impulse Nd:YAG laser-aided debonding are determined (laser output power: 3 W and time: 2 s). Laser irradiation can be used to remove orthodontic ceramic bracket.