LASER-AIDED DEGRADATION OF COMPOSITE RESIN

The removal of residual composite resin after debonding orthodontic br ackets often creates surface scratches, enamel loss, and enamel tearou ts. If the Nd: YAG laser could selectively degrade the resin without d amaging the underlying tooth structure, these problems might be elimin ated. The purpose of this study was to determine the effectiveness of the Nd: YAG laser in degrading composite resin within a time frame tha t will not cause pulpal damage. Minimal lasing times and optimum frequ encies were determined by testing the compressive strengths of resin c ylinders exposed to laser radiation for 2, 3, 5, 10, or 15 seconds at frequencies of 60, 80, or 100 Hz. The optimum condition was determined to be a 3 second lasing time at a frequency of 100 Hz. Cylinders of c omposite resin were divided into four groups consisting of: (1) resin, (2) resin with a laser enhancing dye, (3) resin lased for 3 seconds a t 100 Hz, and (4) resin with the dye which was lased for 3 seconds at 100 Hz. The compressive strengths of the four groups were statisticall y compared. The resin groups that were lased for 3 seconds at 100 Hz s howed a 75% reduction in compressive strength. The results of this stu dy demonstrate that dual wavelength pulsed Nd: YAG laser energy, when used within the parameters described here, will degrade the mechanical properties of composite resin, thereby offering the potential for a q uick and efficient method of removing residual composite resin.