Peer reviewed article isible light units (LCU) used in routine dentistry to cure light activated materials may become contaminated with oral micro-organisms. This pilot study was designed to investigate whether the fan, handle and base unit mains on/off button areas of three different designs of quartz tungsten halogen LCUs (3M Unitek 2500, Elipar Highlight, Demetron Optilux 401) were effectively disinfected after use in a dental teaching hospital. Over a period of seven days 52 LCUs were swabbed before clinics in the morning and 28 were swabbed again after clinics in the afternoon. Bacterial contamination was detected on approximately 40 % (20/52) of units before use and 64 % (18/28) after use: few viable organisms were detected on the fan or handle areas, but many were isolated from the mains button, including Staphylococus aureus . These fi ndings highlight the need for greater awareness of the potential risk of contamination of the base unit and compliance with recommendations to clean and disinfect all areas of the units. Figure 1. Use of a light curing unit in dental restoration. The whole length of the light guide may enter the patient's mouth, depending on the location of the treatment site. The model illustrated is an Elipar Highlight (as in Figure 2A ). The "concertina" style fan or "nose cone" containing the fan in other designs can brush against the corner of the patient's mouth and become contaminated directly by saliva in that manner
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