Sensitivity of oral bacteria to 254 nm ultraviolet light

Z. Metzger*, M. Dotan, H. Better, I. Abramovitz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Aim: To explore the sensitivity of bacteria commonly found in root canals to 254 nm ultraviolet (UV) light, either as individual cells or as participants of a bacterial multilayer. Methodology: The sensitivity of oral bacteria, as individual cells, to UV light was tested by subjecting plates streaked with bacteria to 254 nm UV, at a fluence of 1-20 mJ cm-2. An experimental model was designed to produce a bacterial multilayer and to study absorption of UV light by bacteria in an outer layer and its effect on the elimination of bacteria in the inner layer. Results: Direct exposure to relatively low doses of UV light (2-7 mJ cm-2) effectively eliminated all bacterial strains tested. Furthermore, an Enterococcus faecalis strain, partially resistant to a 24 h exposure to calcium hydroxide, was effectively eliminated within several seconds of exposure to UV light (P < 0.001). UV was absorbed by a multilayer of bacteria. When 4 bacterial cells μm-2 were present in the light path, the UV light dose had to be increased by a factor of ×10 to achieve 100% elimination of the bacteria in an inner layer. Conclusions: The application of UV light to eliminate endodontic pathogens may be possible. Nevertheless, its absorbance by outer layers of bacteria should be considered and the UV light dose adapted accordingly.

Original languageEnglish
Pages (from-to)120-127
Number of pages8
JournalInternational Endodontic Journal
Issue number2
StatePublished - Feb 2007


  • Absorption
  • Oral bacteria
  • Ultraviolet


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