Influência de Diferentes Métodos de Fabricação no Comportamento Mecânico de Instrumentos Endodônticos de Níquel-Titânio

Abstract

Objective: To evaluate the mechanical behavior of K3 NiTi endodontic instruments (Sybron Endo, Orange, CA, USA) with conventional manufacturing or subjected to a thermal treatment during manufacturing (K3XF instruments; Sybron Endo). Methods: Twenty K3 and K3XF instruments with D0 0.25 mm, 0.06 mm/mm taper and 25 mm length were used. For standardizing purposes, 10 instruments of each type were examined by a stereomicroscope and two instruments (K3 and K3FX) had their cross-sections analyzed by scanning electron microscopy (SEM). Flexibility and fracture strength were evaluated by 45? bending test and static fatigue test, respectively. Ten K3 and K3FX instruments were used for each test, obtaining the flexural load values and the number of cycles to failure (NCF). Student's t test was used for statistical analysis. The fractured instruments were examined by SEM. Results: The flexural load was significantly greater for the K3 than for the K3FX (p<0.05) instruments, 713.3 g and 536.4 g, respectively. The NCF was significantly greater for the K3FX than for the K3 instruments (p<0.05). SEM analysis of the fractured surfaces revealed ductile-type morphological characteristics for both types of instruments and absence of plastic deformity. Conclusion: NiTi instruments subjected to thermal treatment presented lower flexural strength values when subjected to 45o bending and greater NCF values. It may be assumed that the instruments subjected to a special thermal treatment during the manufacturing process (K3FX) are more flexible and more resistant to fatigue fracture than the conventional K3 instruments.