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Comparison of defects in ProTaper hand‐operated and engine‐driven instruments after clinical use
Author(s) -
Cheung G. S. P.,
Bian Z.,
Shen Y.,
Peng B.,
Darvell B. W.
Publication year - 2007
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.1365-2591.2006.01200.x
Subject(s) - fracture (geology) , orthodontics , materials science , shear (geology) , fatigue testing , dentistry , composite material , medicine
Aim To compare the type of defects and mode of material failure of engine‐driven and hand‐operated ProTaper instruments after clinical use. Methodology A total of 401 hand‐operated and 325 engine‐driven ProTaper instruments were discarded from an endodontic clinic over 17 months. Those that had fractured were examined for plastic deformation in lateral view and remounted for fractographical examination in scanning electron microscope. The mode of fracture was classified as ‘fatigue’ or ‘shear’ failure. The lengths of fractured segments in both instruments were recorded. Any distortion in hand instrument was noted. Data were analysed using chi‐square, Fisher's exact or Student's t ‐test, where appropriate. Results Approximately 14% of all discarded hand‐operated instruments and 14% of engine‐driven instruments were fractured. About 62% of hand instruments failed because of shear fracture, compared with approximately 66% of engine‐driven instruments as a result of fatigue ( P < 0.05). Approximately 16% of hand instruments were affected by shear, and either remained intact or was fractured, compared with 5% of engine‐driven instruments ( P < 0.05). The length of the broken fragment was significantly shorter in hand versus engine‐driven group ( P < 0.05). Approximately 7% of hand instruments were discarded intact but distorted (rarely for engine‐driven instruments); all were in the form of unscrewing of the flutes. The location of defects in hand Finishing instruments was significantly closer to the tip than that for Shaping instruments ( P < 0.05). Conclusions Under the conditions of this study (possibly high usage), the failure mode of ProTaper engine‐driven and hand‐operated instruments appeared to be different, with shear failure being more prevalent in the latter.