Residual heat deposition in dental enamel during IR laser ablation at 2.79, 2.94, 9.6, and 10.6 μm

✍ Scribed by Daniel Fried; Jerome Ragadio; Allen Champion

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 183 KB
• Volume: 29
• Category: Article
• ISSN: 0196-8092
• DOI: 10.1002/lsm.1111

✦ Synopsis

Abstract

Background and Objective

The principal factor limiting the rate of laser ablation of dental hard tissue is the risk of excessive heat accumulation in the tooth. Excessive heat deposition or accumulation may result in unacceptable damage to the pulp. The objective of this study was to measure the residual heat deposition during the laser ablation of dental enamel at those IR laser wavelengths well suited for the removal of dental caries. Optimal laser ablation systems minimize the residual heat deposition in the tooth by efficiently transferring the deposited laser energy to kinetic and internal energy of ejected tissue components.

Study Design/Materials and Methods

The residual heat deposition in dental enamel was measured at laser wavelengths of 2.79, 2.94, 9.6, and 10.6 μm and pulse widths of 150 nsec −150 μsec using bovine block “calorimeters.” Water droplets were applied to the surface before ablation with 150 μsec Er:YAG laser pulses to determine the influence of an optically thick water layer on reducing heat deposition.

Results

The residual heat was at a minimum for fluences well above the ablation threshold where measured values ranged from 25–70% depending on pulse duration and wavelength for the systems investigated. The lowest values of the residual heat were measured for short (< 20 μs) CO~2~ laser pulses at 9.6 μm and for Q‐switched erbium laser pulses at 2.79 and 2.94 μm. Droplets of water applied to the surface before ablation significantly reduced the residual heat deposition during ablation with 150 μsec Er:YAG laser pulses.

Conclusions

Residual heat deposition can be markedly reduced by using CO~2~ laser pulses of less than 20 μsec duration and shorter Q‐switched Er:YAG and Er:YSGG laser pulses for enamel ablation. Lasers Surg. Med. 29:221–229, 2001. © 2001 Wiley‐Liss, Inc.