The effectiveness of glass bead sterilizer in the dental practice

Objectives: Glass bead sterilizer is a common method for chair-side sterilization of small hand instruments, especially endodontic files, in the dental practice. Several studies from the 1950-1970s achieved sterilization by the bead sterilizer within few seconds. Nevertheless, there are no current evidence-based instructions for using the sterilizer. This study was designed to evaluate the effectiveness of this method in sterilization of endodontic files, according to the current microbiologic knowledge. We evaluated Actinomyces Israelii, which is primarily a commensal microbe found in normal oral flora and dental plaques, in tonsillar crypts, and in carious teeth, because its pathological importance, and Bacillus Cereus, a heat-resistance spores-forming oral bacteria that used as standard for sterilization tests.

Methods: Standard endodontic k-files (#15, 50, 80) were sterilized in a steam autoclave and then soaked in Actinomyces Israelii and Bacillus Cereus [0.5 MacFarland] media for 10 seconds. After drying, the files were placed in 225°C-heated glass bead sterilizers for 15, 30 and 60 seconds. The files were incubated according the guideline of the American Society of Microbiology for these specific organisms. Then morphologic and biochemical examination were performed to reveal bacterial growth.

Results: Files that have been contaminated with A. Israelii were sterilized within 30 seconds, whereas B. Cereus-contaminated files needed 60 second for sterilization.

Conclusions: It seems that the common method of using the glass bead sterilizer for sterilization time of few seconds is not effective. In order to eliminate spore-forming bacteria, like B. Cereus, by glass bead sterilizer, the sterilization time has to be at least 60 seconds. More research is needed, however, for establishing the effectiveness of the glass bead sterilizer for viral infection control.