The effectiveness of glass bead sterilizer in the dental practice

OBJECTIVES: Although it is not FDA-approved as inter-patients sterilization measure, in Israel, glass bead sterilizer is still a common method for chair-side sterilization of small dental hand instruments, especially endodontic files. Studies from the 1950-1970s achieved sterilization by the bead sterilizer within few seconds. Nevertheless, there are no current evidence-based instructions for using this sterilizer. The study was designed to evaluate the effectiveness of this method in sterilization of endodontic files, according to current microbiologic knowledge. METHODS: Standard endodontic k-files (#15, 50, 80) were sterilized in a steam autoclave and then soaked in Actinomyces israelii, Eikenella corrodens or Bacillus cereus [0.5 MacFarland] media for 10 sec. After drying, the files were placed in 225 degrees C or 250 degrees C-heated glass bead sterilizers for 0, 15, 30 or 60 sec. After appropriate incubation for 10 d, morphologic and biochemical examinations were performed to reveal bacterial growth. RESULTS: Files that have been contaminated with A. israelii were sterilized within 30 sec, whereas B. cereus and E. corrodens-contaminated files needed 60 sec for sterilization. CONCLUSIONS: The use in bead sterilizer has to be limited only for sterilization of intra-appointment purpose. However, it seems that the common method of using bead sterilizer for sterilization time of few seconds is not effective. In order to eliminate spore-forming bacteria, like B. cereus, by bead sterilizer, the sterilization time has to be at least 60 sec. More research is needed, however, for establishing the effectiveness of the bead sterilizer for viral infection control and for other dental instruments.