# Material compatibility of guanidine thiocyanate for decontamination of nickel-titanium root canal instruments after potential exposure to prions

## TL;DR

This study tests if guanidine thiocyanate can safely decontaminate dental instruments without affecting their strength.

## Contribution

The study evaluates the material compatibility of guanidine thiocyanate on nickel-titanium dental files after prion decontamination.

## Key findings

- GdnSCN decontamination up to 8 times for 15 minutes does not affect torsional strength or bending stiffness of the instruments.
- A 12-hour exposure to GdnSCN reduced bending moment and torsion angle for size 25.06 files.
- The material properties of size 35.04 files remained unaffected even after extended exposure.

## Abstract

Due to the effectiveness of guanidine thiocyanate (GdnSCN) for the decontamination of prion protein aggregates, which are the causative agent of transmissible spongiform encephalopathy, the influence on the bending stiffness and torsional strength of endodontic nickel-titanium files should be tested to provide a potential alternative to single-use if necessary.

For the investigation, nitrite-titanium-coated EasyShape® files of sizes 25.06 and 35.04 were placed in 6 M GdnSCN solution 8 times for 15 min each for decontamination in line with the manufacturer’s recommendation, with intermediate drying in each case. To simulate the worst case, the soaking time was extended to 12 h once. Both the bending stiffness and the torsional and fracture behavior were determined in accordance with DIN EN ISO 3630-1:2008-04.

Compared to the untreated control (n=12), decontamination with GdnSCN has no effect on the torsional strength or flexural rigidity of the tested endodontic instruments of sizes 25.06 and 35.04 (n=18 each) when used properly. On the other hand, the exposure time of 12 h reduced the bending moment and torsion angle of instrument size 25.06, while the material properties of size 35.04 files are not affected.

Based on the results, the maximum 8-fold application of 6 M GdnSCN solution for 15 min for decontamination of endodontic nickel-titanium files can be considered. Although the sterilization process has no influence on the fracture behavior, it is important to clarify for clinical practice what influence the overall reprocessing process has on the performance of the instruments.