An evaluation of washer-disinfectors (WD) and dishwashers (DW) effectiveness in terms of processing dental instruments


Purpose: The aim of this study is to consider the effectiveness of a small sample of dishwashers (DW) compared to washer-disinfectors (WD) for cleaning dental instruments prior to sterilisation. Processing instruments in the context of this article means cleaning and disinfecting the instruments.

Materials and Methods: A number of tests were carried out on three domestic dishwashers and two instrument washer-disinfectors. These tests included; visual test; soil test; residual protein test; and, the TVC of the final rinse water.

Results: The washer-disinfectors (one bench-top and one under-bench) passed all the tests.

The results indicate that the instruments cleaned in the dishwashers were visibly clean and dishwashers passed the TOSI soil test. There was residual protein on some of the instruments cleaned in the all of the dishwashers and the final rinse water did not comply with standard ISO 15883.1

Conclusion: Dishwashers are not effective for cleaning instruments and they do not disinfect the instruments either. They cannot be validated and there is no record available outlining the parameters of the process. Dishwashers are not designed by manufactures for processing dental instruments prior to sterilisation.

Hugh O’Connor
B.Sc., M.Sc., IHEEM
Registered Authorising Engineer
Principal Clinical Engineer Technician
St James’s Hospital, Dublin.

Nick Armstrong
B.A., B.Dent. Sc., M.Sc.