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A comparison of cyclic fatigue between used and new M two Ni–Ti rotary instruments
Author(s) -
Plotino G.,
Grande N. M.,
Sorci E.,
Malagnino V. A.,
Somma F.
Publication year - 2006
Publication title -
international endodontic journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.988
H-Index - 119
eISSN - 1365-2591
pISSN - 0143-2885
DOI - 10.1111/j.1365-2591.2006.01142.x
Subject(s) - molar , statistical significance , dentistry , cyclic stress , mathematics , significant difference , statistical analysis , analysis of variance , orthodontics , dental instruments , medicine , materials science , statistics , composite material
Aim To evaluate the cyclic fatigue of M two Ni–Ti rotary instruments after controlled clinical use in molar teeth. Methodology Twenty M two instruments of each size were selected and divided into two groups: group A consisted of 10 new instruments (control group); group B consisted of 10 used instruments. Each instrument in group B was used to clean and shape 10 root canals of molar teeth in patients. Cyclic fatigue testing of instruments was performed in tapered artificial canals with a 5‐mm radius of curvature and a 60° angle of curvature. In all 140, instruments were rotated until fracture and the number of cycles to failure was recorded. Data were analysed using one‐way anova , Tukey's HSD test and independent sample t ‐test to determine any statistical difference; the significance was determined at the 95% confidence level. Results A reduction of cycles to failure between new (group A) and used (group B) instruments was apparent. A statistically significant difference ( P < 0.05) was noted between instruments of groups A and B in all sizes with the exception of size 40, 0.04 taper. Conclusions Clinical use significantly reduced cyclic fatigue resistance of M two rotary instruments when compared with an unused control group. However, all the instruments had minimal instrument fatigue when discarded after controlled clinical use.