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Proceedings Paper

Microsecond enamel ablation with 10.6µm CO2 laser radiation
Author(s): W. S. Góra; A. McDonald; D. P. Hand; J. D. Shephard
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Paper Abstract

Lasers have been previously been used for dental applications, however there remain issues with thermally-induced cracking. In this paper we investigate the impact of pulse length on CO2 laser ablation of human dental enamel. Experiments were carried in vitro on molar teeth without any modification to the enamel surface, such as grinding or polishing. In addition to varying the pulse length, we also varied pulse energy and focal position, to determine the most efficient ablation of dental hard tissue and more importantly to minimize or eradicate cracking. The maximum temperature rise during the multi pulse ablation process was monitored using a set of thermocouples embedded into the pulpal chamber. The application of a laser device in dental surgery allows removal of tissue with higher precision, which results in minimal loss of healthy dental tissue. In this study we use an RF discharge excited CO2 laser operating at 10.6μm. The wavelength of 10.6 μm overlaps with a phosphate band (PO3-4) absorption in dental hard tissue hence the CO2 laser radiation has been selected as a potential source for modification of the tissue. This research describes an in-depth analysis of single pulse laser ablation. To determine the parameters that are best suited for the ablation of hard dental tissue without thermal cracking, a range of pulse lengths (10-200 μs), and fluences (0-100 J/cm2) are tested. In addition, different laser focusing approaches are investigated to select the most beneficial way of delivering laser radiation to the surface (divergent/convergent beam). To ensure that these processes do not increase the temperature above the critical threshold and cause the necrosis of the tissue a set of thermocouples was placed into the pulpal chambers. Intermittent laser radiation was investigated with and without application of a water spray to cool down the ablation site and the adjacent area. Results show that the temperature can be kept below the critical threshold either by using water spray or by decreasing the repetition rate. We demonstrate that CO2 laser pulses with pulse lengths in the regime of 10 μs can provide precise enamel tissue removal without introducing any unwanted thermal damage.

Paper Details

Date Published: 29 February 2016
PDF: 6 pages
Proc. SPIE 9692, Lasers in Dentistry XXII, 969205 (29 February 2016); doi: 10.1117/12.2207455
Show Author Affiliations
W. S. Góra, Heriot-Watt Univ. (United Kingdom)
A. McDonald, Univ. College London (United Kingdom)
D. P. Hand, Heriot-Watt Univ. (United Kingdom)
J. D. Shephard, Heriot-Watt Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 9692:
Lasers in Dentistry XXII
Peter Rechmann; Daniel Fried, Editor(s)

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