Modeling the modification depth of carbon dioxide laser-treated dental enamel

✍ Scribed by Zuerlein, Michael J.; Fried, Daniel; Featherstone, John D.B.

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 892 KB
• Volume: 25
• Category: Article
• ISSN: 0196-8092
• DOI: 10.1002/(sici)1096-9101(1999)25:4<335::aid-lsm8>3.0.co;2-f

✦ Synopsis

Background and Objectives

: Many studies of laser-induced thermal decomposition of dental enamel have demonstrated a reduction in the rate of acid dissolution, size of artificial carieslike lesions, and acid reactivity. Additionally, studies have correlated the loss of carbonate from dental enamel with a reduction in acid dissolution. Dental mineral consists of hydroxyapatite with many substitutions, the major one being carbonate (∼ 3-5% by weight), which markedly affects acid reactivity. The principle objective of the present work was to determine the precise depth of modification, i.e., thermally induced decomposition of dental enamel (carbonate loss), at the predicted optimum laser irradiation parameters. Study Design/Materials and Methods: Bovine enamel blocks were irradiated at = 9.6 m with 2-sec and 100-sec pulses and at = 10.6 m with 2-sec pulses. Carbonate loss was calculated from infrared spectra as a function of depth and compared to numerical simulations of the maximum temperature rise.

Results: Carbonate loss was initiated at temperatures greater than 400°C, but was complete only after repeated irradiation of the surface above the melting threshold. Carbonate loss of dental enamel irradiated at 9.6 m with a 100-sec pulse and at 10.6 m with a 2-sec pulse was greater than that of enamel irradiated at 9.6 m with a 2-sec pulse. The depth of carbonate loss in dental enamel irradiated with a 2-sec pulse was greater for = 10.6 m than for = 9.6 m.

Conclusion:

The depth of modification is consistent with the presented model that incorporates the absorption depth and thermal relaxation time/pulse duration. However, repeated irradiation is required for complete removal of carbonate, depending on absorption depth and pulse duration. Lasers Surg.