Cyclic fatigue resistance of several deep cryogenically treated nickel-titanium endodontic rotary and reciprocating files in artificial canals.

OBJECTIVE

Until now no studies were conducted to evaluate the cyclic fatigue resistance of both - rotary and reciprocating - endodontic instruments with and without cryogenic treatment. Therefore, the aim of this in vitro study was to evaluate the effect of cryogenic therapy on the cyclic fatigue resistance of various nickel-titanium rotary and reciprocating endodontic files in an artificial 90º curved canal.

MATERIAL AND

METHODS

This in vitro study was conducted using 20 rotary and 20 reciprocating nickel-titanium (NiTi) instruments: 10 ProTaper Next, 10 ProTaper Ultimate, 10 Reciproc and 10 Plex RC-ONE. All instruments were divided equally into control and cryogenic treatment groups. Instruments in cryogenic treatment groups were immersed in liquid nitrogen (-196ºC) for 24 hours, after which they were gradually returned to the room temperature. All instruments were tested in an artificial canal with a 90º curvature, and the entire process was recorded till the instrument fracture. Time to fracture was multiplied by the corresponding rotation speed. Statistical analysis was performed using IBM SPSS Statistics software.

RESULTS

The results of this study revealed statistically significant positive effect of cryogenic treatment on the cyclic fatigue resistance of Reciproc system instruments, while no statistically significant effect of cryotherapy was observed in the other instrument groups. When comparing different instrument systems in the cryogenic treatment groups, Reciproc instruments demonstrated statistically significantly higher cyclic fatigue resistance than other instruments in this study.

CONCLUSIONS

Our research demonstrated the efficacy of deep cryogenic treatment in increasing the cyclic fatigue resistance of reciprocating endodontic instrument system Reciproc. The study also showed the significantly better Reciproc resistance to cyclic fatigue than rotary ProTaper Next and ProTaper Ultimate instruments.