UCSF

Background and Objective: Excessive heat accumulation within the tooth, incomplete removal of composite, and variable damage to the enamel are shortcomings of using conventional burs to remove residual orthodontic composite after debonding fixed appliances. The objective of this study was to determine if composite could be selectively removed from the enamel surface using a rapidly scanned carbon dioxide laser controlled by spectral feedback.

Materials and Methods: A carbon dioxide laser operating at a wavelength of 9.3 µm with a pulse duration of 10-15 µs and a pulse repetition rate of ~ 200 Hz was used to selectively remove composite from the buccal surfaces of 21 extracted teeth. GrenGlooTM composite was used to better visualize residual composite and the amount of enamel lost was measured with optical microscopy. A spectral feedback system utilizing a miniature spectrometer was used to control the laser scanning system. Pulpal temperature measurements were performed during composite removal to determine if there was excessive heat accumulation.

Results: The amount of enamel lost averaged 22.7µm ± 8.9 and 25.3 µm ± 9.4 for removal at 3.8 and 4.2 J/cm2, respectively. An average maximum temperature rise of 1.9°C ± 1.5 was recorded, with no teeth approaching the critical value of 5.5°C. The average time of composite removal was 19.3 ± 4.1 seconds.

Conclusions: Residual orthodontic composite can be rapidly removed from the tooth surface using a rapidly scanned CO2 laser with spectral feedback, with minimal temperature rise within the pulp and with minimal damage to the underlying enamel surface.