Shaping ability of different single‐file systems in severely curved root canals of extracted teeth

Abstract

Under the conditions of this study, all instruments respected the original canal curvature well and were safe to use. The use of Reciproc and OneShape instruments required less time to prepare the curved canals compared with Mtwo and F360.

Cyclic fatigue resistance of OneShape and WaveOne instruments using different angles of curvature

“…Cyclic fatigue resistance is also influenced by the chemical composition of the alloy, cross-sectional design, and thermomechanical process applied during alloy manufacturing 8) . WO was manufactured using M-Wire NiTi, while OS instrument was manufactured from a conventional austenite 55-NiTi alloy 9,10) . The M-Wire technology offers NiTi instruments with greater flexibility and resistance to cyclic fatigue than those made of regular superelastic wires 29) .…”

“…WaveOne (WO) (Dentsply Maillefer, Ballaigues, Switzerland) is one of these single-instrument systems which uses a reciprocating motion. The reciprocating motion is based on a counterclockwise (CCW) motion (cutting direction) and a clockwise (CW) motion (release of the instrument) 10) . The values of CCW and CW rotations are different.…”

“…A large rotating angle in the cutting direction (CCW) allows the instrument to advance in the canal and engage the dentin to cut it. A smaller angle in the opposite direction (CW) allows the instrument to be immediately disengaged and safely progress along the canal path, thus reducing the tendency of "screwing in" and fractures 10,11) . WO instruments have a modified convex triangular crosssection at the tip and a convex triangular cross-section in the middle and coronal portions of the instrument 12) .…”

“…In the first zone at the tip region, the cross-section is characterized by a three-cuttingedge design which transforms progressively in the middle zone to two cutting edges. In the last zone at the shank, an S-shaped cross-section presents two cutting edges 9,10,15) . Additionally along the working part, the OS instrument has variable pitch length which is claimed by the manufacturer to help reduce the screwing effect 15) .…”

Effect of different rotary systems on fracture resistance of post-core reconstructed teeth

“…Son olarak, koronal üçüncü kısımdaki yatay kesitte 2 şekilli kesici kenar bulunur. [48][49][50] Üretici firmaya göre, eğenin değişken yatay kesitli tasarımı, vidalanan eğenin kanal duvarlarına etkisini azaltır. Bu bağlamda, OSNG'nin 3 ile 2 kesici kenar arasında giderek değişen üç farklı seviyede değişken kesitlere sahip olması kök kanallarındaki stresin azalmasını ve böylece kırılma dayanımının artmasını sağladığını düşünmekteyiz.…”