Impact of torsional and bending inertia on root canal instruments

The laws of applied mechanics can be used to analyze and predict the behavi or of mechanical parts subjected to strain and distortion, such as endodont ic instruments. Simple mathematical formulas can be used to represent the i mpact of torsional and bending inertias on stresses in endodontic instrumen ts being used in root canals. The boundary integral method was applied to t wo theoretical models with the same diameters but different cross-sections to evaluate quantitatively and qualitatively the stresses produced in ortho gonal cross-sections. The results confirmed the mathematical deduction conc erning the impact of torsional and bending stresses. The results indicate t hat clinical protocols based on the torsional and bending properties of end odontic instruments must be strictly followed, and endodontic instrument ma nufacturers must adopt standardized criteria for describing these propertie s.