Comparison and evaluation of surface deformation of Hyflex controlled memory and Hyflex electric discharge machining nickel titanium rotary files and cyclic fatigue resistance after instrumentation and heat sterilization - An in vitro study.

AIMS: The aim of this study is to evaluate and compare the surface deformation and cyclic fatigue resistance of Hyflex controlled memory (CM) and Hyflex electric discharge machining (EDM) files following instrumentation and heat sterilization.

SUBJECTS AND

METHODS

Thirty Hyflex CM and thirty Hyflex EDM files were selected and profilometric images taken. Sixty extracted molars were decoronated, cleaning and shaping done with files, and subjected to autoclaving. Profilometric images were taken after instrumentation and sterilization. Cyclic fatigue testing was done at 30° and 60° in a custom-made jig.

STATISTICAL ANALYSIS USED: The Mann-Whitney test was used to compare profilometer and cyclic fatigue values between Hyflex CM and Hyflex EDM groups, whereas Friedman's and Wilcoxon signed-rank test were used for intragroup comparisons.

RESULTS

Intact Hyflex EDM files showed higher surface roughness values compared to Hyflex CM. Hyflex CM showed an increase in surface roughness after instrumentation and sterilization that was statistically significant while Hyflex EDM showed no statistical significance both after instrumentation and sterilization. Hyflex EDM showed a significantly higher mean number of cycles to failure than Hyflex CM at both degrees.

CONCLUSIONS

Hyflex EDM files are able to maintain their surface topography and also have cyclic fatigue resistance better than Hyflex CM after both instrumentation and sterilization.