A cleaning protocol for rotary nickel-titanium endodontic instruments

The cleaning of endodontic and all dental instruments prior to sterilization is a prerequisite for their processing for re-use. This study aimed to develop a clinically practical cleaning protocol for rotary nickel-titanium (NiTi) endodontic files prior to sterilization.

Cleaning experiments were conducted on six different types of files that had been used on human teeth. The experiments involved three components of mechanical and chemical removal of root canal debris from the files: the use of sponges soaked with chlorhexidine to remove gross debris, pre-soaking, and ultrasonication. After cleaning, the files were immersed in Van Gieson's solution and examined under magnification for stained debris. New unused files were also examined.

Macroscopically, there were no instances of visible debris and all files appeared clean after all cleaning sequences. Microscopically, new files showed both stained and unstained debris, and several experimental cleaning regimens produced files that were free of stained debris. Combining elements of the most effective cleaning sequences resulted in a cleaning protocol that predictably produced clean files.

The results do not support the recommendation for the single use of endodontic files based on inability to clean files between uses. Under experimental conditions the cleaning protocol developed rendered rotary NiTi files 100 per cent free of stained debris. The protocol comprises 10 vigorous strokes in a scouring sponge soaked in 0.2 per cent chlorhexidine solution, a 30 minute pre-soak in an enzymatic cleaning solution, 15 minutes ultrasonication in the same solution, and a 20 second rinse in running tap water. The protocol can be applied to all endodontic files.