Premium
Effects of CO 2 laser irradiation on tooth enamel coated with biofilm
Author(s) -
Cohen Julie,
Featherstone John D.B.,
Le Charles Q.,
Steinberg Doron,
Feuerstein Osnat
Publication year - 2014
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/lsm.22218
Subject(s) - enamel paint , biofilm , irradiation , demineralization , scanning electron microscope , fourier transform infrared spectroscopy , materials science , laser , nuclear chemistry , chemistry , composite material , optics , bacteria , genetics , physics , nuclear physics , biology
Background and Objectives CO 2 laser irradiation of tooth enamel can inhibit demineralization of tooth enamel, by changing enamel composition and resistance to acid attack. The aim of this work was to examine these effects of CO 2 laser irradiation on enamel covered by biofilm. Materials and Methods Streptococcus mutans was grown on bovine enamel surfaces for 48 hours to form a mature biofilm. Samples were irradiated by CO 2 laser (wavelength of 10.6 µm) at a power of 0.08 W in a super‐pulse mode for 1 second and 24 pulses/second, with an energy density of 0.77 J/cm 2 per pulse. Untreated controls and laser treated samples with and without biofilm were examined for the morphology of the biofilm and the enamel surface by scanning electron microscopy (SEM). Structural biofilm viability was assessed using confocal laser scanning microscopy with live/dead staining. The biofilm was removed in a sonication water bath and the non‐treated and irradiated enamel samples were chemically analyzed using energy dispersive X‐ray spectrometry (EDS) and Fourier transform infrared spectroscopy (FTIR). Results Irradiated samples showed a melt zone with micro‐cracks in the center of the irradiating beam position, which was smaller when irradiated enamel was covered by biofilm. Confocal microscopy images demonstrated higher proportion of dead bacteria at the margins of the irradiated spot area, while at the spot center the bacteria were evaporated exposing the enamel surface to direct laser irradiation. EDS analysis showed an increase in Ca/P ratio after irradiation of enamel covered with biofilm. FTIR analysis showed an approximately 40% carbonate loss in the irradiated enamel samples, including those with biofilms. Conclusion Biofilms protect enamel surfaces from possible morphological irradiation damage without interfering with the resultant chemical changes that may increase the enamel resistance to acid attack. Therefore, under certain exposure regimens that are thermally and mechanically safe for enamel, CO 2 laser irradiation of biofilms on dental hard tissues is suggested as a potential novel preventive treatment for controlling dental caries. Lasers Surg. Med. 46:216–223, 2014. © 2014 Wiley Periodicals, Inc.