A novel approach to determine the effect of irrigation on temperature and failure of Ni-Ti endodontic rotary files

Sayed Ali Mousavi, Vida Kargar-Dehnavi, Sayed Amir Mousavi


Background: Nickel-titanium (Ni-Ti) rotary instrument files are important devices in Endodontics
in root canal preparation. Ni-Ti file breakage is a critical and problematic issue and irrigation
techniques were applied to decrease risk of file failure root. The aim of the present study was
to compare the temperature gradient change of different irrigation solutions with Ni-Ti rotary
instrument system during root canal preparation and also to define their effects on the file failure.
Materials and Methods: A novel computerized instrumentation was utilized and thirty standard
(ProFile #25/.04) files were divided into three groups and subjected to a filing in the root canal test.
Changes in temperature on teeth under constant instrumental conditions with custom-designed
computerized experimental apparatus were measured by using a temperature sensor bonded to
the apical hole. A rotary instrument for canal preparation in three series of solution was used and
the changes in temperature after each solution were compared. Finally, the file failure results were
mentored according to each step of test. Comparisons were performed between group status
clinically by using ANOVA (t) test, once the sample showed up normal and differences of P<0.01
were considered significant. All data collected were computerized and analyzed for frequency,
distribution, and statistical description.
Results: There was a decrease in the temperature of the instruments, which were immersed
in 5% NaOCl, when compared with the water group (P<0.01). There was also a decrease in the
temperature of the instruments immersed in water, when compared with the no solution group
(P<0.01). Test results showed that sodium hypochlorite, water, or air of root canals does alter the
properties of gradual temperature change and contributes to the failure of the instruments.
Conclusion: By immersing the file in 5% NaOCl, the temperature gradient decreased and
instrument failure was reduced.
Key Words: File failure, instruments, Ni-Ti, solution, temperature

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