Cyclic fatigue resistance for six types of nickel titanium instruments at artificial canals with different angles and radii of curvature

This study evaluated the cyclic fatigue resistance for six types of 25# NiTi instruments. A traditional manufacturing instrument, an M wire instrument, a gold treatment instrument, a controlled memory (CM) wire instrument, a CM wire instrument with electrical discharge machining (EDM), and an R-phase heat treatment instrument, were operated in the different curved artificial canals. The fracture time (FT) and number of cycles to fracture (NCF) of the NiTi instruments were higher at 45 degrees angles and double-curvature canals than at 60 degrees angles. Except for the instruments with gold technology and EDM technology, others showed the longest FT and the highest NCF at an 8 mm radius of curvature. Morphological characteristics of cyclic fatigue were exhibited on the cross-section and lateral view of fracture fragments. The use of M-wire, R-phase wire, CM-wire, gold technology, EDM technology, and reciprocating movement were beneficial to enhance the cyclic fatigue resistance of NiTi files.

Automated summary

This study evaluated the cyclic fatigue resistance of six types of 25# NiTi instruments, finding differences in performance at different angles and curvatures. Except for instruments with gold and EDM technology, the best performance was seen at an 8 mm radius of curvature.