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Senior Scientist Ellen Bruzell participated at the 22nd European Dental Materials Conference in Birmingham, UK, 29–30 August 2013, with the following presentations:

Antimicrobial photodynamic treatment of oral infections

Objectives: The increased occurrence of antibiotic resistance in general necessitates development of alternative antimicrobial drugs or methods. Further, certain cases of periodontitis respond poorly to conventional treatment. The principle of photodynamic therapy, currently used against certain cancers, may be a practical treatment modality for oral infections, presumably with low possibility for development of resistance. The treatment requires the presence of light-absorbing molecules (photosensitizer; PS) and irradiation with a light source emission that spectrally matches the light-absorption of the PS. The resulting reactive oxygen species and/or photoproducts formed may be toxic to cells and organisms. PS often requires pharmaceutical formulations, water solubility and hydrolytic and photochemical stability, to avoid formation of aggregates and to control the drug release at the target.

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Methods: Phototoxicity induced by the food-colourant curcumin (E100) as a PS in combination with blue light (fluorescent tubes; emission max. 450 nm) on Gram-positive (G+) and -negative (G-) planktonic bacteria and biofilms. Formulations were single vehicles, such as micelles, surfactants, liposomes or cyclodextrines and complex foams consisting of one or more of the vehicles above.

Results and conclusions: The degree of phototoxicity of curcumin (measured as number of colony forming units/ml) was dependent on the type(s) and concentration of formulations as well as curcumin concentration and light dose. Generally, G- bacteria and biofilms were less sensitive to the treatment than were G+. A six log reduction of G+ bacteria was obtained after treatment with several of the investigated formulated preparations containing 2.5 µM curcumin irradiated with 0.5 J/cm2 blue light. To obtain the same reduction for G- bacteria, a micelle/curcumin preparation of 25 µM curcumin irradiated with 30 J/cm2 was required. Improved formulations with increased release of curcumin are under development.

Authors: Ellen M. Bruzell1, Anne Bee Hegge2, Hanne Hjorth Tønnesen2.
Affiliations: 1NIOM – Nordic Institute of Dental Materials, Oslo, Norway; 2 School of Pharmacy, University of Oslo, Oslo, Norway.

 

Safety of optical light sources in the dental clinic

Objective: To inform operators and suppliers of curing/bleaching lamps, lasers and other optical instruments intended for oral applications about safe use. Further, to give references to relevant international guidelines and standards.

Methods: Laboratory measurements of lamps and eye protective filters, literature review and radiation risk assessment according to recommended limit values.

Results: Limit values for exposure to eyes from curing lamp emission were reached within minutes and seconds for blue light and ultraviolet radiation, respectively. Emission from bleaching lamps exceeded limit values for eyes and skin before 10% of the treatment duration had elapsed. About 50% of selected non-laser eye protection filters were of inferior quality. A short description of the following safety related standards and guidelines will be given:erb-2008-13-2.png

  • Limit values and guidelines from International Commission on Non-Ionizing Radiation Protection: www.icnirp.de/PubOptical.htm
  • Standards for laser eye protection: EN 207 and EN 208; non-coherent lamps eye protection: EN 166.
  • Standards for light sources: Safety of laser products EN 60825; Safety of lamps and lamp systems EN 62471; Standards for medical electric equipment IEC 60601, part 2-22 for lasers and part 2-57 for non-laser light sources.
  • Documents related to occupational exposure: EU directive for the workplace 2006/25/EC. For guidelines, see: http://ec.europa.eu/social/main.jsp?catId=738&langId=en&pubId=5926&furtherPubs=yes
  • Standard on measurement and risk assessment, EN 14255-2.

Conclusion: Curing/bleaching lamps and lasers used for oral applications can pose risks to patients and health personnel. Risks can be reduced, e.g. by application of internationally developed standards/guidelines. Correct use of relevant guidelines requires knowledge of the properties of the light source and its applications.

Authors: Terje Christensen1*, Bjørn Johnsen1 and Ellen M. Bruzell2.
Affiliations: 1Norwegian Radiation Protection Authority, Norway and 2Nordic Institute of Dental Materials, Norway. 
* presenting author, terje.christensen@nrpa.no