ABSTRACT
OBJECTIVE To investigate the use of a chlorine dioxide-based dental unit waterline(DUWL) treatment to reduce the colonization and growth of heterotrophic bacteria.METHODS Twenty-two dental units with self-contained water systems were randomly selected.Three of the units and tap water served as controls.Twenty-three water samples were taken at baseline and once a week for five weeks.They were serially diluted,spread-plated in duplicate onto R2A agar plates and incubated at 37 ℃ for 7 days.RESULTS At baseline,the 3 control DUWLs had a median count of 8440 colony-forming units/milliliter(CFU/ml) and the 19 treated DUWLs had a median count of 9160 CFU/ml.By week 1,18 of the 19 treated DUWLs had counts of less than 200 CFU/ml,and by week 4,the median count for all of the treated DUWLs was 0 CFU/ml.The measurement at week 5 showed that the reduction to below 200 CFU/ml had been maintained.Scanning electron examination revealed a similar results,with biofilm accumulation more evident in the untreated control specimens.CONCLUSIONS Using a chlorine dioxide-based disinfectant in DUWLs can achieve the American Dental Association(ADA) goal of less than 200 CFU/ml of heterotrophic bacteria per milliliter of unfiltered output water.
ABSTRACT
OBJECTIVE To observe the effect of flushing dental handpieces to prevent suction-induced contamination and to lower the bacterial level in dental unit waterlines,and then to analyze the time-effect relationship of flushing.METHODS Twelve BienAir handpieces(group A) and 12 W&H TA-96 handpieces(group B) were employed in this study.The water samples from each handpiece′s outlet were immediately taken once when operations of de-caries,cavity-preparing and dental-drilling had been completed,and then taken once per 0.5 min while the handpieces were being flushed by running without work for 4 min.The bacterial colony formation of these water samples was counted on R2A agar plates.Colony forming units vs flushing time were then compared.RESULTS Alike in groups A and B,water bacterial levels were lowered the most significantly while flushing the handpieces for 0.5 min.BienAir or W&H TA-96 handpieces still showed decreased levels of water bacteria when being flushed for 3 or 2.5 min respectively.Afterwards,the flushing effect reached to a platform,that was,more flushing time didn′t bring the bacterial level down further.CONCLUSIONS Flushing handpieces by running without work can significantly reduce the level of bacterial contamination in the waterlines.Different types of handpieces may have different flushing time at which the most effect is reached.