Direct evidence for effective cleaning and decontamination of the internal air and water channels, heads and head-gears of multiple contra-angle dental handpieces using an enzymatic detergent and automated washer-disinfection in a dental hospital setting

We have read the letter by Smith and colleagues [ ] claiming that our recent paper [ ] published in the Journal of Hospital Infection in October 2022 will mislead the readership about the effective cleaning and decontamination of dental handpieces (DHPs) by washer disinfection because the work was not supported by consensus international standards. In our view, Smith and colleagues have misconstrued our study and its purpose. Prior to our study, there was little published data in the literature on the direct effectiveness of washer disinfectors at significantly reducing contamination from the internal components of DHPs, especially in a dental hospital setting where large numbers of DHPs must be decontaminated simultaneously daily. Of course, there are a range of international standards governing the decontamination of reusable invasive medical devices including those cited by Smith and colleagues, but there are none specifically for DHPs. DHPs have a complex internal architecture including narrow lumens and channels that can become contaminated during use. DHPs also require lubrication with oil prior to sterilization. DHPs are not intended to be disassembled routinely to investigate the effectiveness of cleaning and decontamination processes nor is direct examination of internal components of DHPs covered by any of the international standards. The purpose of our study was to investigate whether washer disinfection using an enzymatic detergent is effective at decontaminating the internal components of DHPs deliberately contaminated with four process challenge micro-organisms and organic test soil by directly examining the internal components following washer disinfection. This has not been investigated thoroughly in previous studies. Our study provided comprehensive direct evidence that this process is very effective, including with multiple DHPs processed simultaneously. Furthermore, effective decontamination was achieved using densities of micro-organisms and levels of organic contamination significantly in excess of levels that would be encountered during routine use of DHPs in dental practice.