Sammanfattning
BACKGROUND – Chloride is added to the dental unit water system to maintain a low germ count. A low concentration of chlorine is preferred to avoid corrosion of the instruments.
CASE – At the Department of Dentistry and Oral Health at Aarhus University a low germ count had been maintained inthe dental unit water system with a concentration of 0,2 ppm chloride, far below the recommended 2,5 ppm. The chlorid concentration was reduced to 0,15 ppm to further reduce the
risk of corrosion. A slightly increased germ count was subsequently observed and it was not reduced by resetting the chloride concentration to 0.2 ppm. Troubleshooting showed that the automatic disinfection of non-working units stopped when the unit computer experienced an automatic update.
The system was redesigned to make the automatic disinfection of units independent of the individual unit computer and the dental unit water systems of all units was flushed with 1,9 ppm of chloride. This restored the germ count to the low level it had had before reducing the chloride concentration.
CONCLUSION – Regular checks for technical problems of the dental unit water system is recommended in order to avoid formation of biofilm and increased germ counts necessitating cleaning of the entire system to restore good water quality.