Effectiveness of ultrasonic cleaning of dental instruments.

Purpose: To quantitate blood contamination present on dental instruments used for routine prophylaxis and to assess the effectiveness of ultrasonic decontamination in reducing blood and virus contamination on dental instruments.

Materials And Methods: Human blood contamination present on dental instruments obtained after routine prophylaxis was analyzed using IgG as a blood marker.

Results: The estimated contaminating blood volume was found to normally range between 1.4 x 10(-6) to 2.0 x 10(-4) ml. Attempts to saturate the instruments with blood contamination suggested that the maximum possible retained blood volume was about 10-fold higher than the normal levels of contamination. Hand scrubbing of contaminated instruments was both relatively ineffective and inconsistent in removing blood contamination. Decontamination in an ultrasonic cleaner was more effective than hand washing, resulting in greater than a 100-fold reduction of blood contamination. Using a mouse model virus (lactate dehydrogenase-elevating virus, LDV), high levels of virus contamination of dental instruments and dental handpieces were achieved, as determined by assay of residual virus. Ultrasonic treatment reduced the level of virus contamination present on dental instruments by one million-fold, and virus contamination present in dental handpieces was reduced by one thousand-fold. These results provide quantitative estimations of the infection threat and its reduction by ultrasonication, posed by human-exposed dental instruments.