Japanese Society for Infection Prevention and Control-Online Journal

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Research on Microbial Contamination of Dental Unit Waterline

Rie KAMINOTA¹⁾, Atsuko WATANABE²⁾, Miki KAWADA-MATSUO³⁾, Hitoshi KOMATSUZAWA³⁾ and Shouichi MIYAWAKI²⁾⁴⁾
¹⁾Department of Dental Hygiene, Clinical Technology Department, Kagoshima University Hospital, ²⁾Department of Orthodontics, Center of Developmental Dentistry, Kagoshima University Hospital, ³⁾Department of Bacteriology, Hiroshima University Graduate School of Biomedical and Health Sciences, ⁴⁾Department of Orthodontics and Dentofacial Orthopedics, Kagoshima University Graduate School of Medical and Dental Sciences

Objective: The purpose of this study is to understand the current status of microbial contamination in water supply system of dental units and evaluate effective countermeasures against microbial contamination.
Subject and methods: Water samples were collected before flushing and after 10 s of flushing from three-way syringe before medical treatment on Monday and Friday.
Disinfectant treatment was performed for units with disinfection function after the medical treatment on Friday, and water was collected after discharging the disinfectant and after 10 s flushing before medical treatment on Monday day after a holiday. In this study, the unit was disinfected after the end of clinic hours on Friday although it is recommended to be performed after the end of clinic hours every day. After sampling, we counted the bacterial colony forming units (CFU).
Result: The number of microorganisms was significantly higher in the units that had been used for a long time than in the other units.
A significant difference was observed in the number of microorganisms before and after flushing in the unit with short-use units, but the effect was low in the unit with long-use ones.
The number of microorganisms had been few regardless of before and after flushing in units with disinfection function.
Discussion: Long-use units tend to have high number of microorganisms and have weaker flushing effects, suggesting the need to improve the current flushing method.
Although there were many specific bacterial species in each unit, the flora showed diversity.
It suggested that microorganisms may have entered from a three-way syringe or turbine hand piece used during the treatment.

Key words：water system, contamination, infection control

e-mail: a-wtnb＠dent.kagoshima-u.ac.jp

Received: December 28, 2021
Accepted: June 7, 2022

37 (5)：183─189,2022