Effect of slightly acidic hypochlorous acid on disinfection of dental unit waterlines
OBJECTIVE To observe the effect of slightly acidic hypochlorous acid on disinfection of dental unit wa-terlines(DUWLs)and removal of biofilms.METHODS A total of 108 water samples were collected from dental handpieces,three-way syringes and mouthwash water of 36 dental units of stomatology department.The status of microbial contamination was observed and identified.The water supply pipelines and DUWLs were rinsed and dis-infected with different concentrations of hypochlorous acid.Totally 13 dental chairs were randomly selected,and the water samples were collected from the dental handpieces,three-way syringes and mouthwash water for micro-bial culture after the disinfection.RESULTS The median total bacterial colony counts of the dental handpieces was 340 CFU/ml before the disinfection,the three-way syringes 240 CFU/ml,the mouth wash water 217 CFU/ml.Pseudomonas aeruginosa,Sphingobacterium thalpophilum and Chryseobacterium indologenes were dominant a-mong the isolated pathogens.When 50 ppm of hypochlorous acid was used for regular disinfection,the total bacte-rial colony counts of the water samples from ends of DUWLs declined on the 1st day,then rapidly rose and reached the peak on the 3rd-5th day;the median total bacterial colony counts of the water samples at the outlets after the disinfection were more than 10 times as those before the disinfection,and the water samples presented with yellow-brown flocculent substance.The total bacterial colony counts were decreased after the disinfection for 7 days.When 100 ppm of hypochlorous acid was used for regular disinfection,the total bacterial colony counts of the water samples from ends of DUWLs declined sharply on the 1st day,the total bacterial colony counts of the water samples at the outlets were less than 50 CFU/ml on the 3rd day.The bacterial colony counts were less than 20 CFU/ml during the process of persistent disinfection with 5 ppm low concentration.CONCLUSION There is microbial contamination in the DUWs.The high concentration of slightly acidic hypochlorous acid can achieve re-markable effect on eradicating the biofilms of DUWLs,and the low concentration of slightly acidic hypochlorous acid can inhibit the growth of microorganism inside the pipelines.
Dental unit waterlineSlightly acidic hypochlorous acidBiofilmEffect of disinfection
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