ABSTRACT
Dental unit waterline system is considered potential source for contamination with Legionella species. The aim of this study was to determine if contamination of a dental unit water line system by Legionella pneumophila serogroup1 in the Mashhad School of Dentistry occurred in 2009. A total of 52 dental units were selected from all clinical departments of the Mashhad School of Dentistry. Samples of water were collected from outlets of water/air spray, high-speed dental hand pieces and water cup fillers. Samples were tested via the ELISA method. At the beginning of the work day, a total of 36.1 percent of dental units were contaminated by Le-gionella pneumophila serogroup 1. Infection control of the dental unit water line system regarding legionella in the Mashhad School of Dentistry is a challenge and engineering controls should be used in contaminated clinics