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Proceedings Paper

Beam profile measurements for dental phototherapy: the effect of distance, wavelength and tissue thickness
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Paper Abstract

Light delivery for potential bacterial disinfection (UV/blue) and photobiomodulation (near-IR) requires specific, concentrated and controllable local irradiance and dose. Dental targets for light irradiation involve dentine, which scatters, absorbs and reflects light, reducing local irradiance. This study compared the effectiveness of LEDs (400-900nm) and lasers (660nm and 810nm) to penetrate dentine. Caries-free wisdom teeth were sectioned through the Pulpchamber by either cutting perpendicular to the crown, the buccal aspect or obliquely. Specimens were wet-polished to 1, 2 or 3mm thicknesses to expose the dentine on opposing surfaces. The beam profile of the LEDs/lasers were measured through dentine specimens (n=5) to obtain beam width following optical calibration, and spatial irradiance distribution following photodiode power calibration. There were no significant differences in the percentage power and irradiance transmitted through different dentine specimens between LEDs and lasers (P>0.05). However, light penetration through tissue was wavelength dependent and highest for red and near-IR wavelengths (P<0.05) for specimens cut perpendicular to the crown compared with buccal and oblique specimens. The beam diameters increased and irradiance decreased significantly (P<0.05) with increasing specimen thickness/distance for both LEDs and lasers. There was a noticeable shift in beam position for all light sources in buccal and oblique specimens. Data indicated that dentine tubule orientation may alter the direction of light through the tissue. Optimal light penetration and distribution through dentine at specific distance is best achieved with a flat-top beam distribution vertically through the crown of the tooth.

Paper Details

Date Published: 5 March 2015
PDF: 13 pages
Proc. SPIE 9309, Mechanisms for Low-Light Therapy X, 930905 (5 March 2015); doi: 10.1117/12.2077628
Show Author Affiliations
William M. Palin, The Univ. of Birmingham (United Kingdom)
Mohammed A. Hadis, The Univ. of Birmingham (United Kingdom)
Michael R. Milward, The Univ. of Birmingham (United Kingdom)
James D. Carroll, THOR Photomedicine Ltd. (United Kingdom)
Paul R. Cooper, The Univ. of Birmingham (United Kingdom)

Published in SPIE Proceedings Vol. 9309:
Mechanisms for Low-Light Therapy X
Michael R. Hamblin; James D. Carroll; Praveen Arany, Editor(s)

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