Influência de diferentes instrumentos de exploração no comportamento em torção dos instrumentos MTWO após uso clínico múltiplo / influence of Nickel-Titanium rotary glide path on the torsional resistance of Mtwo shaping instruments after multiple clinical use

RESUMO

As propriedades mecânicas, especialmente a resistência dos instrumentos endodônticos de NiTi são influênciadas pelas suas características geométricas, físicas e químicas, somadas ainda à influência da anatomia dos canais radiculares. A exploração e negociação do canal radicular seguido de dilatação prévia ao processo de formatação (Glide Path) reduz consideravelmente as chances de fratura dos instrumentos. Essa manobra elimina as interferências em toda a extensão do canal, possibilitando aos instrumentos seguintes agirem livremente na formação e limpeza minimizando assim, a sobrecarga sobre o mesmo. O objetivo desse trabalho foi avaliar a resitência torcional após uso clínico múltiplo dos instrumentos de Niti PathFile e Scout RaCe e a influência de três diferentes sequências de glide path (K-File, PathFile e Scout RaCe) no comportamento em torção dos instrumentos de formatação MtWo...

ABSTRACT

The mechanical properties, mainly the resistance of endodontic instruments are affected by factors such as diameter, design, chemical composition, physical properties and canal anatomy. Instrument failure can be controlled by creating a manual or mechanical glide path. The aim of this study was to evaluate the torsional resistance of PathFile and Scout RaCe NiTi rotary instruments with the purpose of "glide path” after multiple clinical use and the influence of three different preflaring (K-File, PathFile and Scout RaCe) on the torsional resistance of shaping Mtwo files after multiple clinical use. The mechanical behavior was evaluated by torsion tests, in accordance with specification ISO 3630-1. All instruments showed geometric features within the tolerance limits and no significant difference concerned about the torsional resistance. Despite of one subtle increase in torsional resistance is noted, it is suggested as an effect of simultaneous sterilization methods or by the work hardening of the NiTi alloy. The present study highlights the importance of preparing the glide path before introducing the shaping files and concludes if sterilization does not render rotary NiTi endodontic instruments stronger, it does not result in deleterious effects that could reducetheir mechanical resistance.