A STUDY ON THE MICROBIAL CONTAMINATION OF DENTAL UNIT AND ULTRASONIC SCALER

Lee, Byung Moon; Kim, Chang Whe; Kim, Young Soo

Abstract

The risk of cross-contamination in dental clinic is very high, Those who are engaged in dental clinic are exposed to various microorganisms in saliva and blood of patient. Potential possibility of cross-contamination of patient to patient, patient to dentist, dentist to laboratory technician always exist, which is important in the view of public health, It is well known that microorganisms may cause cross-contamination by suck-back of microorganisms into the water supply line or air supply line of dental unit and sprayed back into the next patient's oral cavity. The majority of microorganisms coming from dental unit are water microorganisms from the main water supply which have colonized the tube within the units and multiplied in the relatively warm and stagnant conditions. The purpose of this study is measure the extent of microbial contamination of dental unit and ultrasonic scaler, to evaluate that dental unit water supply is suitable for drinking water, and to assess the effect of flushing on reduction of microbial contamination of dental unit and ultrasonic scaler. In the first experiment, water samples(50ml) from 20 dental units and 10 ultrasonic scalers in Seoul National Univ. Hosp. were tested for the presence of coliform, The samples were filtered by membrane filtration technique.(Microfil system, Millipore Co. U. S. A.) The filter was then placed onto MacConkey agar plate and the plates with filter on it were incubated aerobically at 37degrees C for 5 days. The colors and shapes of colonies were examined if those were coliform, To verify the presence of coliform, the colonies were inoculated into phenol red lactose broth and incubated aerobically at 37degrees C for 2 days. The fomation of gas was observed. In the second experiment, water samples from 20 handpieces, 10 ultrasonic scalers and 30 A/W syringes after 0, 2, 4, 6 min. flushing respectively were taken. 200micrometer water samples were spreaded on Brain Heart Infusion agar plate and the plates were incubated aerobically at 37degrees C for 5 days. The number of colony was counted. The results obtained were summarized as follows 1. The water from dental unit and ultrasonic scaler was not suitable for drinking water. 2. No coliform was founded in dental unit and ultrasonic scaler water supply. 3. The number of colony of dental unit and ultrasonic scaler was highest in the group of o min. Flushing(p<0.05). 4. There was no statistically significant difference in the extent of microbial contamination among handpiece, ultrasonic scaler and A/W syringe(p>0.05). 5. The number of colony was lowest in the group of 4 min. flushing, but there was no statistically significant difference among 2, 4, 6 min. flushing groups.(p>0.05). 6. It is recommended to flush dental unit water line for 4 min. after use on each patient.