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.