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sep 2011

Design features of rotary endodontic instrumental and its physicomathematical analysis

E.A. Rzhanov* & T.S. Belyaeva
Moscow State University of Medicine and Dentistry Department of Operative Dentistry and Endodontics, Moscow, Russia

Aim

To develop a new procedure for the analysis of the basic design parameters of rotary endodontic instruments, which allows carrying out comprehensive comparative evaluation of its properties.

Methodology

Four systems of nickel-titanium rotary instruments with different geometries were selected: ProFile (Tulsa Dental, Tulsa, Oklahoma), ProTaper (Dentsply Maillefer, Ballaigues, Switzerland), FlexMaster (VDW, Munich, Germany) and Mtwo (VDW, Munich, Germany). A scanning electron photomicrographs were taken of each instrument from each system at the magnifi cation ×25, ×100 and ×120. Then three instruments of each type were sectioned transversely at 1mm, 3mm, 6mm and 10mm from the tip and also were examined by scanning electron microscopy at the magnifi cation ×150. All images were captured digitally and the following design parameters were assessed by a direct measurement technique: tip angle, helical angle, pitch length, depth of fl utes, ratio between the external and internal diameters, angles of cutting blades. All measurement values then were processed with the mathematics program Mathcad 14.0 (PTC, Needham, Massachusetts, USA).

Results

Technical analysis based on the measured parameters enabled to calculate the important instrument properties which infl uence its behaviour inside the root canal: distribution of torsion rigidity along the axis of the instrument, torsion angle per unit length along the axis, self-feeding force component, volume of fl uting along the axis, safe depth of cutting per unit step of treatment.

Conclusions

Physics-mathematical analysis is accurate and objective method for the assessment of the principal design parameters of rotary endodontic instruments. It enables evaluating of outstanding characteristics of each instrument and carrying out comprehensive comparative analysis of the instruments of different types.