The impact of clinical use on the torsional behavior of Reciproc and WaveOne instruments.

Rafael Rodrigues Soares De Magalhães,Vicente Tadeu Lopes Buono,Maria Guiomar De Azevedo Bahia,Isabella Faria Da Cunha Peixoto,Lígia Carolina Moreira Braga,Érika Sales Joviano Pereira

doi:10.1590/1678-775720150596

Abstract

ABSTRACTTorsional overload is a fracture representative parameter for instruments in single-file techniques. Objective The aim of this study was to assess the influence of clinical use, in vivo, on the torsional behavior of Reciproc and WaveOne instruments considering the possibility that they degraded with use.Material and Methods Diameter at each millimeter, pitch length, and area at 3 mm from the tip were determined for both types of instruments. Twenty-four instruments, size 25, 0.08 taper, of each system were divided into two groups (n=12 each): Control Group (CG), in which new Reciproc (RC) and WaveOne Primary (WO) instruments were tested in torsion until rupture based on ISO 3630-1; and Experimental Group (EG), in which each new instrument was clinically used to clean and shape the root canals of one molar. After clinical use, the instruments were analyzed using optical and scanning electron microscopy and subsequently tested in torsion until fracture. Data were analyzed using one-way analysis of variance at a=.05.Results WO instruments showed significantly higher mean values of cross-sectional area A3 (P=0.000) and smaller pitch lengths than RC instruments with no statistically significant differences in the diameter at D3 (P=0.521). No significant differences in torsional resistance between the RC and WO new instruments (P=0.134) were found. The clinical use resulted in a tendency of reduction in the maximum torque of the analyzed instruments but no statistically significant difference was observed between them (P=0.327). During the preparation of the root canals, two fractured RC instruments and longitudinal and transversal cracks in RC and WO instruments were observed through SEM analysis.Conclusion After clinical use, no statistically significant reduction in the torsional resistance was observed.

Highlights

Nickel–Titanium (NiTi) rotary instruments UHSUHVHQWHGVLJQL¿FDQWSURJUHVVLQWKHSUHSDUDWLRQ of the root canal system; they may experience premature failure caused by fatigue17,24 or by torsional overload
The rupture occurs when the torsional stress locks the instrument in dentine walls and becomes higher than the maximum torque; the instrument can withstand at that point15
To evaluate the magnitude of the torsional load to which the instruments are subjected when used in VLQJOH¿OHWHFKQLTXHVLVRIIXQGDPHQWDOLPSRUWDQFH Considering that the instrument progress in the canal without pre-enlargement and being aware that the amount of torque generated during the shaping of root canals clearly depends on the size of the contact areas between the instruments and the canal walls20, the purpose of this research was to analyze the effect of the clinical use on torsional resistance of Reciproc and WaveOne instruments

Summary

Introduction

Nickel–Titanium (NiTi) rotary instruments UHSUHVHQWHGVLJQL¿FDQWSURJUHVVLQWKHSUHSDUDWLRQ of the root canal system; they may experience premature failure caused by fatigue or by torsional overload. The rupture occurs when the torsional stress locks the instrument in dentine walls and becomes higher than the maximum torque; the instrument can withstand at that point. The rupture occurs when the torsional stress locks the instrument in dentine walls and becomes higher than the maximum torque; the instrument can withstand at that point15 This risk may be reduced by performing coronal enlargement and by creating a glide path before using any NiTi rotary instrument. Two brands of NiTi instruments, adopting the VLQJOH¿OHV\VWHPDQGDGYRFDWLQJWKHUHFLSURFDWLRQ concept, were recently introduced into the market: Reciproc (VDW, Munich, Germany) and WaveOne (Dentsply-Maillefer, Ballaigues, Switzerland). These ¿OHV DUH PDGH RI D 1L7L DOOR\ FDOOHG 0:LUH WKDW is produced by an innovative thermomechanical treatment process. They employ a reciprocating motion, rather than a continuous rotary motion; the former reduces the torsional stress by

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Conclusion