Author/Editor		Majaron, Boris; Šušterčič, Dušan; Lukač, Matjaž
Title		Debris screening and heat diffusion in Er:Yag drilling of hard dental tissues
Type		članek
Source		Proc SPIE Int Soc Opt Eng
Vol. and No.		Letnik 2973
Publication year		1997
Volume		str. 11-22
Language		eng
Abstract		A systematical investigation of Er:YAG laser drilling of both human dentin and enamel with pulselengths between 50 micro s and 1.2 ms is presented. At the shorter pulselengths, the influence of heat diffusion is negligible. Consequently, ablation of tissue starts abruptly at a well-defined fluence value, which is independent of the pulselength. Depths and volumes of the resulting craters show a quasi-logarithmical dependence on the applied laser fluence. An improved analytical model of the laser beam screening by the ejected debris is developed, which fits well to the experimental data. With longer laser pulses, ablation turns up only gradually, with differential ablation efficiency slowly increasing with applied laser fluence. Such double-threshold behavior is explained by a simple model of dynamical interplay between the ablation front and heat-diffusion wave. The model enables us to derive expressions for pulselength and laser fluence ranges in which such behavior should be xpercted for any combination of tissue and laser properties. Also, it predicts qualitatively the amount of thermal side effects in a general laser ablation process.
Descriptors		DENTIN DENTAL ENAMEL LASER SURGERY ERBIUM YTTRIUM HEAT LASERS