Preliminary Study On The Control Of Microorganism Contamination In The Dental Unit Waterlines

ObjectiveDental unit is very important in the practice of oral treatment,the water flow of the waterline system is versatile in the treatment.However,there is serious microorganism contamination in the pipes.According to the results of many studies,total amount of microorganism in the dental unit waterlines can reach to 10~6CFU/ml,among these,there are bacteria,fungi,moulds and protozoa.Researchers detected varied opportunistic pathogens in these microbes.They can fly into the mouth of patients with the flow of water,so than cause people’s inflammatory response,especially people who are hypoimmunity,such as old man and children,or long-term drug dependent people.Beside of this,the water mist formed in the operation of a high-speed handpiece also pollutes the air and the surface of the object around the operating point,which threatens the health of the medical staff.Nowadays,more and more attention has been paid to reducing the incidence of nosocomial infection in various hospitals in China.The pollution of the dental unit waterlines should be paid more attention to.We need to find methods to control the contamination of microbes and make reasonable standards to help the long-term detection.The purpose of this experiment is to have a preliminary understanding of the production and development of the contamination in the waterline system by establishing laboratory model,and treat the biofilm in pipes with the disinfectant produced by manufacturers,in order to evaluate the disinfection effect of the disinfectant in laboratory and clinical conditions.MethodsExperiment 1:the 4mm inner diameter silica gel pipe sample was selected for model establishment,with a duration of 29 days.On the 4 day,the 8 day,the 15 day,the 22day,and the 29 day of the morning,the first circulating water 30 s and the residue water at the end of the cycle were collected on the R2A medium for colony culture,and the dynamic changes of the microorganisms contamination were observed.Also,the morphological changes of the biofilm on the morning of 4 days,8 days,11 days and 15 days was observed under the scanning electron microscope.Experiment 2:choose the pipes which have been cultured for 14 days in the the previous experiment,and the 5 mm tube samples were cut out after the action of0.25%,0.5%,0.75%,1%,2%concentrations of disinfectant in the biofilm for 15 h,the biofilms inside the walls were scraped and cultured on R2A medium to observe the sterilization effect.Experiment 3:4 dental chairs in the department of periodontics were selected for three days to disinfect the waterline system for a period of 6 days.Before and after disinfection,three-in-one air/water syringe,ultrasonic scalers waterlines and water for rinsing the mouth,10 ml of water samples,were cultured on the R2A medium,recorded the Colony-Forming Units,and the standard rate of qualification of 500CFU/ml recommended by the American Dental Association was compared.Results1.the occurrence and development of waterlines contamination:the content of bacteria in urban tap water is 30 CFU/ml.Under the flow state,the microbial content of water increased slowly,while the microbial content in water under stagnation increased rapidly.Under the scanning electron microscope,a small amount of extracellular polysaccharide was found among the attached bacteria on the 8 day,and a more complete biofilm was formed for about 14 days.2.the effect of the disinfectant on the biofilm in the pipe:on the 14 day without disinfectant,the average amount of bacteria on the inner wall of the pipe was 1305.55CFU/ml,and the total number of cultured bacteria was reduced to 0 CFU/ml after the disinfectant with a concentration of 0.25%,0.5%,0.75%,1%,2%was used.3.the control of the contamination of the water after the application of the disinfectant clinically:the average colony density of the three sites before disinfection was three with air/water syringe of 34425 CFU/ml,the rinse water at 13116.67CFU/ml,and the ultrasonic scalers 42858.33 CFU/ml,in addition,there has no significant difference of bacterial colony between water samples before disinfecting.After disinfection,the sterilization rate was between 92～100%,and there was no significant difference in disinfection efficacy between the three loci.The average pass rate was 91.67%in the first morning,but only 45.83%after two days.ConclusionsThe increase of microbial biomass in the pipe under stagnation is greater than that in the flowing state.The important structure of the biofilm is formed in 7 days,and the whole biofilm is formed at 14 days.Application of 0.25%to 2%disinfectant can eliminate bacterial activity in the biofilm of the pipes.In the normal clinic,the bacterial decline effect is obvious in the short term after the application of disinfectant within hydrogen peroxide and silver ion with the final concentration of0.25%,but it will rise sharply after the stop disinfection,and the long-term control effect is not good.It can be deduced that in the two disinfection,the biofilm in the pipe could not be completely removed.