Effect of steam sterilization inside the turbine chambers of dental turbines,☆☆

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Abstract

Objective. It has been demonstrated that contamination of the insides of high-speed dental turbines occurs and that bacteria as well as viruses may remain infectious when expelled from such turbines during subsequent use. Consequently, it has been widely recommended that a high-speed turbine be sterilized after each patient. The purpose of this study was to evaluate the effect of steam autoclaving on a high-speed dental turbine with a contaminated turbine chamber. Study Design. Streptococcus salivarius and endospores of Bacillus stearothermophilus were used as test organisms to determine the effectiveness of 4 different small non-vacuum autoclaves and one vacuum autoclave. Results. The study demonstrated different efficiencies among the small non-vacuum autoclaves, the best showing close to a 6 log reduction of the test organisms inside the turbine chamber. When cleaning and lubrication of the high-speed dental turbine was carried out before autoclaving, this level of reduction was observed for all the examined non-vacuum autoclaves. Conclusions. It is concluded that cleaning before sterilization is essential for safe use of high-speed dental turbines and that small non-vacuum autoclaves should be carefully evaluated before being used for the reprocessing of hollow instruments such as high-speed turbines. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:184-8)

Section snippets

Dental high-speed turbines

Twelve Super-Torque 630 B (KaVo A/S) HTs were included in the study. The turbines had been used for several months in operative dentistry. Before each experiment, the turbines were cleaned and lubricated and then sterilized in a vacuum autoclave (Selectomat-S-2000, MMM).

Cleaning and lubricating

KaVo’s Rotaspray II was used for cleaning and lubrication. Information on the exact composition of this cleaner/lubricant could not be obtained from the manufacturer.

Autoclaves

Four different non-vacuum autoclaves and one vacuum autoclave

Viable bacteria in turbine chambers after artificial contamination of HTs with human saliva

The number of viable bacteria in the pooled saliva cultured aerobically or anaerobically was at the level of 40 to 50 million CFU/mL. After cultivation of the contaminated turbine wheels, an average contamination of 500,000 CFU/mL (standard deviation, 720,000 CFU/mL) was found for the HTs that had been operated above the surface of saliva, and an average contamination of 1,300,000 CFU/mL (standard deviation, 1,700,000 CFU/mL) was found for the HTs that had been submerged in the saliva.

Survival of endospores of B stearothermophilus inside the turbine chambers after autoclavation

Table I

DISCUSSION

As noted previously, a potential risk for transmission of microorganisms from dental turbines has been demonstrated.14, 17 However, the documentation of simultaneous transmission of disease is still sparse. The possibility of cross contamination from one patient to another via an HT is primarily dependent on retraction of saliva into the turbine chamber. Therefore, the effect of autoclaving on HTs was studied with special interest in the killing effect inside the turbine chambers.

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References (18)

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Reprint requests:Hans-Kristian Andersen,Danish Medicines Agency,Inspection and Medical Devices,Frederikssundsvej 378,DK-2700 Bronshoj,Denmark

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