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Determination of energy density threshold for laser ablation of bacteria An in vitro study
Author(s) -
Coffelt Doublas W.,
Cobb Charles M.,
MacNeill Simson,
Rapley John W.,
Killoy William J.
Publication year - 1997
Publication title -
journal of clinical periodontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.456
H-Index - 151
eISSN - 1600-051X
pISSN - 0303-6979
DOI - 10.1111/j.1600-051x.1997.tb01177.x
Subject(s) - ablation , laser , bacteria , in vitro , microbiology and biotechnology , materials science , dentistry , biology , medicine , optics , physics , genetics
The Nd:YAG and CO 2 lasers have been shown to be bactericidal at relative low energy densities. However, at energy densities exceeding 120 J/cm 2 (CO 2 ) and 200 J/cm 2 (Nd:YAG). laser irradiation also causes irreparable root surface damage. The purpose of this study was to determine, in vitro, the energy density threshold at which microbial ablation could be achieved while inflicting the least amount of damage to the root surfaces of human teeth. Pairs of Escherkhia coli colonies cultured on broth agar were treated with a CO 2 laser using a pulsed waveform at approximate energy densities ranging from 3 to 110 J/cm 2 . One of each colony‐pair was then examined by scanning electron microscopy (SEM) and the other subcultured for viable microbes. Roots of extracted teeth were lightly scaled and treated by CO 2 laser, again with pulsed beam using approximate energy densities of 3 to 110 J/cm 2 : and examined by SEM. Regardless of the level of energy density, residual bacteria could be subcultured from all laser treated microbial colonies. The inability of the laser to completely obliterate microbial colonies was likely due to: depth of energy penetration, difficulty in precisely overlapping beam focal spots, irregular beam profile, and presence of microbes at the periphery of the beam focal spot. The threshold energy density for bacterial obliteration was determined to be 11 J/cm 2 and that for root damage was 41 J/cm 2 . Root damage was evident by charring, crater formation, meltdown and resolidification surface mineral, and increasing surface porosity. The results of this in vitro study indicate that when used at an energy density between 11 and 41 J/cm 2 : the CO 2 laser may destroy microbial colonies without inflicting undue damage to the tooth root surface.