Objectives: To compare the efficacy of sterilization methods used in dental offices and determine their compliance with sterilization. Methods: The Sterilization Assurance Service of Loma Linda University tests biological indicators for sterilization efficacy using a strip containing Geobacillus stearothermophilus and Bacillus atrophaeus. These strips are processed and mailed in from dental offices located through the USA. A retrospective analysis of results from 2000 to 2008 was conducted to evaluate the efficacy of three most commonly used sterilization methods: autoclave, chemiclave, and dry heat. Compliance with the sterilization protocol was determined by number of samples sent by each office with minimum requirement of one sample/week as recommended by the CDC. Incomplete submission of samples was considered invalid and excluded. A total of 117,695 samples (88,527 for autoclave, 22,964 for chemiclave and 6,204 for dry heat) were received and tested. Binomial test was used to evaluate data at the significance level of α = 0.05. Results: Compliance rate for sample submission increased in the last 4 years, however compliance rates (≥48 samples/year) were less than the 50% of subscribes.
Samples/Year | 2008 | 2007 | 2006 | 2005 |
≥ 48 | 33.7% | 29.7% | 26.9% | 25.2% |
24 - 47 | 37.1% | 39.0% | 41.1% | 32.3% |
< 24 | 29.2% | 31.3% | 32.0% | 42.5% |
Overall failure rate was 2.23% (2,626 of 117,695), with autoclave accounting for 1.57% (1,390 of 88,527), chemiclave 3.21% (736 of 22,964) and dry heat, 8.06% (500 of 6,204). Failure rates for autoclave were significantly lower than chemiclave (p <0.0001) and dry heat (p <0.0001). Failure rates for chemiclave were significantly lower than dry heat (p <0.0001). Conclusions: Autoclave is the most effective method of sterilization with a significantly lower failure rate than chemiclave and dry heat and it is the preferred method whenever available. Compliance with sterilization checks needs to be enforced to assure safe operations of dental clinics.