Impact of two theoretical cross-sections on torsional and bending stressesof nickel-titanium root canal instrument models

The use of nickel-titanium in the manufacture of endodontic instruments has given rise to continuous-rotation canal preparation techniques. These tech niques involve unidirectional torque, meaning that files are under constant stress and strain when operating. The study presented herein compares tors ional and bending stresses in triple U and triple helix models. This was do ne by applying the boundary integral method to theoretical cylindrical mode ls, The two theoretical models underwent very different torsional stresses, both in terms of intensity and distribution, Bending stresses were much mo re similar, but to obtain the same curvature, bending moments had to be dif ferent. The results of the mathematical calculations indicated that triple U and triple helix instruments should be used for different operating proce dures.