Comparison of different cleaning methods used in dental surgeries

Dental instruments such as endodontic files and matrix band retainers have complex surfaces that are difficult to clean prior to sterilisation. Objectives: This study aims to investigate the efficiency of three cleaning methods currently used in dental surgeries (manual cleaning and ultrasonic cleaning, and cleaning using fully automated washer disinfectors). Methods: A standardised method for measuring residual protein was developed based on a micro BCA assay using HTM2030 recommended (Edinburgh) and commonly used (Brownes) instrument test soils combined with a novel thermostable Adenylate Kinase (tAK) enzyme indicator system and used to study the relative effectiveness of the different methods. Test soils (± tAK) were loaded onto surgical grade stainless steel discs (n=8) and dried down. Manual cleaning was simulated by subjecting the discs to forty strokes of a nylon brush and this was compared to an ultrasonic bath (using 3E-zyme detergent for 20 mins at 43°C) and washer disinfector (with 3E-zyme) following manufacturer's instructions. Results: Using Edinburgh test soil and micro BCA assay the total protein remaining post cleaning was 2.36 (± 4.43µg), 4.11 (± 2.81µg) and 8.53 (± 5.44µg) for the ultrasonic bath, manual wash and washer disinfector respectively. However, using an ultrasensitive bioluminescent assay to detect residual AK levels the washer disinfector was determined to be the most effective cleaning process 0.47 (± 0.69µM) followed by the ultrasonic bath and manual wash detected 1.92 (± 1.53µM) and 7.61 (± 5.70µM) respectively. Both detection methods demonstrated Brownes soil to be easily removed and therefore unable to distinguish any significant differences between the cleaning processes. Conclusion: Significant variation in the relative cleaning efficiencies of the different cleaning methods was found using Edinburgh test soil which may have implications for dental surgery. This study has also established rapid and easy to use standardised methods for comparing cleaning processes.