Previous studies have shown that dentin can be thermally modified by pulsed CO₂ laser irradiation to form a more highly mineralized tissue. The implications are important for the potential laser modification or removal of dentinal and root caries. Temperature excursions were followed after (lambda) equals 9.3, 9.6, 10.3, and 10.6 micrometers laser irradiation with pulses of 100 (Mu) s duration at irradiation intensities of 0.5 to 8 J/cm². In addition, photoacoustic and transient reflectance measurements were used to monitor the loss of water and organics and to detect the thresholds for surface modification and tissue ablation. The surface temperatures of dentin were markedly higher than those measured on enamel for similar irradiation intensities due to the lower reflectance losses of dentin and the lower thermal diffusivity at the respective wavelengths. Hence, lower fluences are required for the thermal decomposition of dentin. Ablation typically occurred with the first few laser pulses during multiple pulse irradiation and eventually ceased after modification of dentin to a more hypermineralized tissue. The debris ejected during the initial laser pulses shielded the surface by as much as 60 percent at the low fluences employed in this study. Optical and electron microscopy and IR spectroscopy indicated that incident laser fluences of 1-2 J/cm² at 9.3 and 9.6 micrometers produced sufficient crystalline changes in the carbonated apatite mineral in dentin for caries preventive treatments.

Date Published: 15 May 1997
PDF: 7 pages
Proc. SPIE 2973, Lasers in Dentistry III, (15 May 1997); doi: 10.1117/12.273576

Published in SPIE Proceedings Vol. 2973:
Lasers in Dentistry III
Harvey A. Wigdor D.D.S.; John D. B. Featherstone; Peter Rechmann D.D.S., Editor(s)