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Proceedings Paper

Laser antisepsis of Phorphyromonas gingivalis in vitro with dental lasers
Author(s): David M. Harris
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Paper Abstract

It has been shown that both pulsed Nd:YAG (1064nm) and continuous diode (810nm) dental lasers kill pathogenic bacteria (laser antisepsis), but a quantitative method for determining clinical dosimetry does not exist. The purpose of this study was to develop a method to quantify the efficacy of ablation of Porphyromonas gingivalis (Pg) in vitro for two different lasers. The ablation thresholds for the two lasers were compared in the following manner. The energy density was measured as a function of distance from the output of the fiber-optic delivery system. Pg cultures were grown on blood agar plates under standard anaerobic conditions. Blood agar provides an approximation of gingival tissue for the wavelengths tested in having hemoglobin as a primary absorber. Single pulses (Nd:YAG: 100- ìs; diode: 100-msec) of laser energy were delivered to Pg colonies and the energy density was increased until the appearance of a small plume was observed coincident with a laser pulse. The energy density at this point defines the ablation threshold. Ablation thresholds to a single pulse were determined for both Pg and for blood agar alone. The large difference in ablation thresholds between the pigmented pathogen and the host matrix for pulsed-Nd:YAG represented a significant therapeutic ratio and Pg was ablated without visible effect on the blood agar. Near threshold the 810-nm diode laser destroyed both the pathogen and the gel. Clinically, the pulsed Nd:YAG may selectively destroy pigmented pathogens leaving the surrounding tissue intact. The 810-nm diode laser may not demonstrate this selectivity due to its longer pulse length and greater absorption by hemoglobin.

Paper Details

Date Published: 28 May 2004
PDF: 6 pages
Proc. SPIE 5313, Lasers in Dentistry X, (28 May 2004); doi: 10.1117/12.549028
Show Author Affiliations
David M. Harris, Univ. of California/San Francisco (United States)
Bio-Medical Consultants, Inc. (United States)


Published in SPIE Proceedings Vol. 5313:
Lasers in Dentistry X
Peter Rechmann; Daniel Fried; Thomas Hennig, Editor(s)

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