ABSTRACT
Objective To survey the retraction of dental unit waterlines (DUWLs)in medical institutions,and evaluate the influencing factors for retraction of DUWLs.Methods In May-November 2014,dental chair units (DCUs)in medical institutions in Tianjin City were sampled through systematic random sampling method,retrac-tion volume of DUWLs was detected by independently made detector,the relevant influencing factors were investi-gated.Results A total of 58 DCUs in 30 medical institutions in 10 districts(counties)of Tianjin were investigated, the average retraction volume of DUWLs was (103.60 ±117.85 )mm3 ,the qualified rate of retraction volume of DUWLs was 48.28 %(28/58);length of utilization of DCUs was positively correlated with DUWLs retraction (r=0.52,P 0.05 ).Conclusion The qualified rate of retraction volume of DUWLs is low,routine maintenance of DUCs needs to be intensified,especially the long-term used DUCs,contaminatin of DUWLs due to the invalidity of retraction valve should be prevented.