Cleanliness in Reprocessing of Dental Instruments

Objectives: In 2015, the Food and Drug Administration (FDA) published a guidance document providing recommendations to medical/dental device manufacturers on the formulation and scientific validation of reprocessing instructions for reusable instruments. This document recommends 6 criteria that should be included in proper reprocessing instructions, including to “thoroughly clean the device.” However, in dentistry, most of the reusable instruments lack manufacturer specific cleaning instructions. The objective of this study was to define a clinically-relevant dental soil; “dirty” diamond instruments with the soil; and then evaluate various cleaning methods for their effectiveness in rendering the instruments “clean” for reuse.
Methods: We used multi-use diamond instruments (Two-Striper®, round-C801, Premier) and employed a “worst-case” soiling procedure, which included drilling a 9 mm access cavity preparation on an extracted molar tooth and then adding a known amount of pooled human saliva mixed with commercially available sheep blood. The soiled instruments were subjected to multiple cleaning protocols varying in cleaning time and type of detergent. Quantitatively, since the FDA doesn’t accept bioburden as a measure of cleanliness, protein and hydroxyapatite were chosen as the 2 clinically-relevant soil components to be quantified for validation-testing, which were then measured by calorimetric and spectroscopic methods. Qualitative assessment of the cleanliness of the instruments was also performed using a scanning-electron-microscope.
Results: The study was successful in designing a dental soil and a soiling protocol, as recommended by the FDA. We also demonstrated a standardized cleaning method, with reprocessing steps of presoaking, rinsing and ultra-sonication for specific times, which rendered the soiled-instrument with minimal levels of residual protein and hydroxyapatite post-cleaning.
Conclusions: A dental soil was successfully developed and used to soil diamond instruments, and then a cleaning method was shown to be effective in removing the dried soil from the multi-use instruments at quantifiable levels. Ongoing work is focused on further quantifying cleaning effectiveness.