Cleanability of Dental Instruments and Issues of Proteins and Prions

By their very nature dental instruments such as endodontic files or retainers have an intricate surface topography with a very high surface area to volume ratio due to their small size and serrated edges. These intricate surfaces are able trap proteins and prions that can irreversibly bind to stainless steel raising some issues with the cleanability of dental instruments. Objective: to investigate the amount of protein materials attached to a range of dental instruments following their use on patients. Methods: dental surgeries were recruited from the South West of England to provide a range of dental instruments including scalers, endodontic files, forceps, matrix bands, suction tubes and retainers that had been used on patients but had not been cleaned or sterilized. The instruments were visually assessed for soiling using a 0 (no debris) to 3 (>50% of the instrument covered with particles) score point system and analysed for adherent protein concentration using a variant of a sensitive protein assay based on o-phthaldialdehyde/N-acetyl cysteine as the fluorescent reagent with reference to a standard curve determined using bovine serum albumin. Results: Scalers were found to have the highest concentration of attached protein (1386 µg/instrument, n=3), followed by the suction tubes (465 µg, n=2), forceps (51 µg, n=3), matrix bands (38 µg, n=3) with 3.9 µg (n=9) protein being recovered from endodontic files. For visual scoring the results were 1.5 (scalers), 1.6 (suction tubes), 0.16 (forceps), 0.8 (matrix bands) and 1.2 (endodontic files) respectively. Conclusion: After being used on patients, the range of dental instruments investigated were found to be heavily fouled with protein. The difficulties associated with cleaning some of these instruments raises issues as to whether some should be regarded as single-use items. Supported by the Department of Health (UK) – contract nos:0070099.