Introduction: Optical feedback from the laser induced ablation plume can be exploited to provide information about the chemical composition of the target tissue or material and the mechanism of ablation. Such data can potentially be used to increase the selectivity of ablation, avoid peripheral thermal damage and excessive heat deposition in the tooth, and provide a means of robotic automation and control. Objective: To determine whether laser plume emission spectra acquired using a compact fiber-optic spectrometer can be used to differentiate between the ablation of sound and carious enamel, enamel and dentin, and dental hard tissue and composite. Methods: Sound and carious tooth surfaces along with composite restorative materials were scanned with 0.355, 2.79, and 9.3 mm laser pulses at irradiation intensities ranging from 0.5-100 J/cm2. Spectral data was acquired from 250-900 nm using a compact fiber-optic spectrometer. Spectra were acquired with and without the addition of extrinsic chromophores such as metal salts and India ink to lesion areas to provide characteristic spectral signatures. Results: Emission spectra varied markedly with wavelength and pulse duration and the onset of plasma formation was indicated by an increase in Ca(II) emission lines. Thermal radiation during the ablation process provided information about the temperature of particles in the plume and the tooth surface temperature. Optical feedback was not successful in differentiating between sound and carious enamel, even with the addition of metal salts or India Ink. However, spectral feedback was successfully used to differentiate between dental hard tissues and composite enabling the selective removal of composite from tooth surfaces using a computer controlled 9.3 mm pulsed CO2 laser and laser-scanning system. Conclusion: Spectral feedback provides a means for the selective removal of composite from tooth surfaces using lasers. Supported by: NIH/NIDCR R01DE14554 and T32DE07306 research grants.

Back to the Cariology Research Program
Back to the ADEA/AADR/CADR Meeting & Exhibition (March 8-11, 2006)

Top Level Search