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Selective Removal of Residual Orthodontic Composite Using a Rapidly Scanned CO2 Laser with Spectral Feedback Designed to Improve the Tooth Enamel Properties



Background and Objective: If lasers could selectively ablate residual composite with minimal damage to the enamel surface, decrease the clinician’s time, and improve the surface properties of underlying enamel, problems with current debonding techniques could be overcome. The overall objective of this work was to selectively remove residual orthodontic composite from the enamel surface using a rapidly scanned carbon dioxide laser controlled by spectral feedback without perceptible changes to the enamel.

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 polished buccal surfaces of 30 extracted human teeth. Laser parameters were tested to determine the ideal settings to remove composite with the least amount of enamel damage. GrenGlooTM composite was used to better visualize residual composite. The amount of enamel surface modulation/roughness was measured with a three dimensional digital microscope. A spectral feedback system utilizing a miniature spectrometer was used to control the laser scanning system.

Results: The amount of enamel lost with our final laser parameters averaged 2.59 ± 0.63 µm. The laser settings that produced the best results were the following: Spot size= 450 µm, Fluence= 4.0 J/cm2, Overlap= 50 µm. These enamel-conserving parameters were still able to remove composite at clinically relevant speeds.

Conclusions: Residual orthodontic composite can be quickly removed from the tooth surface using a rapidly scanned CO2 laser with spectral feedback with minimal damage to the underlying enamel surface.

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