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Modeling the modification depth of carbon dioxide laser‐treated dental enamel
Author(s) -
Zuerlein Michael J.,
Fried Daniel,
Featherstone John D.B.
Publication year - 1999
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/(sici)1096-9101(1999)25:4<335::aid-lsm8>3.0.co;2-f
Subject(s) - enamel paint , carbonate , irradiation , dissolution , carbon dioxide laser , mineralogy , chemistry , reactivity (psychology) , dentistry , materials science , laser , optics , analytical chemistry (journal) , radiochemistry , composite material , medicine , physics , chromatography , organic chemistry , alternative medicine , pathology , laser surgery , nuclear physics
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 caries‐like 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 λ = 9.6 μm with 2‐μsec and 100‐μsec pulses and at λ = 10.6 μm with 2‐μsec 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 μm with a 100‐μsec pulse and at 10.6 μm with a 2‐μsec pulse was greater than that of enamel irradiated at 9.6 μm with a 2‐μsec pulse. The depth of carbonate loss in dental enamel irradiated with a 2‐μsec pulse was greater for λ = 10.6 μm than for λ = 9.6 μm. 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. Med. 25:335–347, 1999. © 1999 Wiley‐Liss, Inc.