Comparison of Sterilization Methods for Re-Use of Orthodontic Bands

Objective: While traditional steam sterilization methods are commonly practiced they may not always be ideal for sterilizing small bore lumen present on some medical devices. If methods are inadequate, disease transmission may result from the re-use of tried-in orthodontic bands. New fractionated vacuum steam sterilization methods have been developed that specifically address the unique sterilization requirements for hollow instruments and medical devices, including orthodontic bands that contain small bore lumen. This study compares the effectiveness of traditional steam sterilization and fractionated vacuum sterilization for the disinfection and sterilization of orthodontic bands, with assorted pre-welded attachments, intentionally contaminated with a panel of representative microorganisms. In light of rigorous European standards for re-use of orthodontic appliances, 3M Unitek has sponsored this work, performed at Part Three Corporation.

Methods: Standard contoured orthodontic bands (3M Unitek) were inoculated with microorganisms including Escherichia coli, Candida albicans, Staphylococcus aureus, Streptococcus mutans, and Geobacillus stearothermophilus. The inoculated bands were ultrasonically cleaned and sterilized using either traditional sterilization or fractionated vacuum steam sterilization. The sterilized bands were then dried and placed in Trypticase soy broth for 7 days at 35°C to observe any re-growth. Afterwards, a random sampling of sterilized bands underwent pull testing to verify that the appliance strength was not compromised.

Results: No growth was observed in cultures containing the disinfected and sterilized bands, indicative that sterilization was achieved using steam autoclaving. Mechanical testing verified that all bands with attachments retained high strength after 1, 10, and 25 sterilization cycles.

Conclusions: A combination of ultrasonic cleaning followed by steam sterilization is adequate to ensure the sterilization of contaminated orthodontic bands. Results from the fractional vacuum autoclave are forthcoming.