The Development of a New Dental Unit without a Water Supply Pipe for Infection Control

Abstract

Water contamination from conventional dental units is serious problem. Health, Labour and Welfare Ministry of Japan set recommended water quality standard as 100 CFU/ml ( common bacteria ) and 2,000 CFU/ml ( heterotrophic bacteria ). However, there are no reports on dental units meeting this standards in Japan. The purpose of this study was to develop a dental units without a water supply pipe, and meet water quality standards of Japan . We removed the water supply pipe from a dental unit, installing a built-in removable water supply tank. We grew common bacteria on standard agar at 36 ℃ for one days and heterotrophic bacteria on R2A agar at 20 ℃ for 7 days, and measured bacterial numbers in the conventional type and the tank type. The results of the conventional type ranged from 180 to 31,000 CFU/ml in common bacteria, and 2,000 to 86,000 CFU/ml in heterotrophic bacteria. The results of the tank type ranged from 30 to 50 CFU/ml in common bacteria, and 30 to 1,500 CFU/ml in heterotrophic bacteria achieving the water quality standard of Japan. The conventional type has a water supply pipe 6-7 m long. In contrast, the tank type has 26cm.