Details

Autor(en) / Beteiligte

• Pedullà, E.
• Lo Savio, F.
• Boninelli, S.
• Plotino, G.
• Grande, N. M.
• Rapisarda, E.
• La Rosa, G.

Titel

Influence of cyclic torsional preloading on cyclic fatigue resistance of nickel - titanium instruments

Ist Teil von

• International endodontic journal, 2015-11, Vol.48 (11), p.1043-1050

Ort / Verlag

England: Blackwell Publishing Ltd

Erscheinungsjahr

2015

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• Aim To evaluate the effect of different torsional preloads on cyclic fatigue resistance of endodontic rotary instruments constructed from conventional nickel‐titanium (NiTi), M‐Wire or CM‐Wire. Methodology Eighty new size 25, 0.06 taper Mtwo instruments (Sweden & Martina), size 25, 0.06 taper HyFlex CM (Coltene/Whaledent, Inc) and X2 ProTaper Next (Dentsply Maillefer) were used. The Torque and distortion angles at failure of new instruments (n = 10) were measured, and 0% (n = 10), 25%, 50% and 75% (n = 20) of the mean ultimate torsional strength as preloading condition were applied according to ISO 3630‐1 for each brand. The twenty files tested for every extent of preload were subjected to 20 or 40 torsional cycles (n = 10). After torsional preloading, the number of cycles to failure was evaluated in a simulated canal with 60° angle of curvature and 5 mm of radius of curvature. Data were analysed using two‐way analysis of variance. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). Data were analysed by two‐way analyses of variance. Results Preload repetitions did not influence the cyclic fatigue of the three brands; however, the 25%, 50% and 75% torsional preloading significantly reduced the fatigue resistance of all instruments tested (P < 0.01, P < 0.001 and P < 0.0001, respectively) except for the HyFlex CM preloaded with 25% of the maximum torsional strength (P > 0.05). Conclusions Torsional preloads reduced the cyclic fatigue resistance of conventional and treated (M‐wire and CM‐wire) NiTi rotary instruments except for size 25, 0.06 taper HyFlex CM instruments with a 25% of torsional preloading.