Cleaning of used rotary nickel-titanium files in an ultrasonic bath by locally intensified acoustic cavitation

Abstract

Aim

To compare the pre-sterilization cleaning of rotary Ni-Ti files of different sizes previously used a. ex vivo and b. clinically by a washer disinfector, a regular ultrasonic bath, and the same ultrasonic bath in combination with a recently developed cavitation intensifying method.

Methodology

Two sets of two hundred rotary Ni-Ti files, one previously used ex vivo and another one used clinically, were collected from the undergraduate and postgraduate clinics of the Academic Centre for Dentistry Amsterdam (ACTA). The instruments were immersed in an enzymatic solution and subsequently cleaned either by a washer disinfector, a regular ultrasonic bath combined with a glass beaker, the same bath combined with a beaker lined with two cavitation intensifying sheets or with two standard plastic sheets. The positive control consisted of used files that did not undergo any cleaning and the negative control included new unused files. The instruments were then stained to reveal remaining protein material and scored under a stereoscopic microscope. The results were analyzed by non-parametric statistical tests (α=0.05).

Results

No significant difference was found between the combination of the ultrasonic bath and the regular glass beaker and the same ultrasonic bath with the beaker lined with the cavitation intensifying sheets. The washer-disinfector left significantly more debris compared to the latter group when clinically-used files were evaluated (P≤0.001). The effect of instrument size on cleaning was not consistent.

Conclusion

None of the tested methods was able to remove all residual protein material from the files, however, it could be noted that the current study did not follow the reprocessing protocol provided by the manufacturer.

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