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Mechanical properties of ProTaper Gold nickel‐titanium rotary instruments
Author(s) -
Elnaghy A. M.,
Elsaka S. E.
Publication year - 2016
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/iej.12557
Subject(s) - cyclic stress , materials science , indentation hardness , nickel titanium , composite material , abrasion (mechanical) , fracture (geology) , bending , dentistry , orthodontics , medicine , microstructure , shape memory alloy
Abstract Aim To evaluate and compare the resistance to cyclic fatigue and torsional stress, flexibility and surface microhardness of ProTaper Gold ( PTG ; Dentsply, Tulsa Dental Specialties, Tulsa, OK , USA ) system with ProTaper Universal ( PTU ; Dentsply Maillefer, Ballaigues, Switzerland). Methodology PTG and PTU instruments were rotated in simulated canals and the number of cycles to failure was recorded to assess their cyclic fatigue resistance. Torsional strength was measured using a torsiometer after fixing firmly the apical 3 mm of the instrument. A scanning electron microscope was used to characterize the topographic features of the fracture surfaces of the broken instruments. The instruments were tested for bending resistance using cantilever‐bending test. Vickers microhardness was measured on the cross section of instruments with 300 g load and 15 s dwell time. Data were analysed statistically using independent t ‐tests. Statistical significance was set at P < 0.05. Results PTG instruments had a significantly higher resistance to cyclic fatigue and flexibility than PTU ( P < 0.001). The fractured cross‐sectional surfaces revealed typical features of cyclic fractures, including crack origins, fatigue zones and overload fast fracture zones. On the other hand, PTU instruments were associated with higher resistance to torsional stress and microhardness than PTG instruments ( P < 0.001). After torsional tests, the fractured cross‐sectional surfaces revealed skewed dimples near the centre of the fracture surfaces and circular abrasion streaks. Conclusions The PTG instrument had improved resistance to cyclic fatigue and flexibility compared with PTU . PTU instruments had improved resistance to torsional stress and microhardness compared with PTG .