Comparison of Forces Generated During Root Canal Shaping and Residual Stresses of Three Nickel–Titanium Rotary Files by Using a Three-Dimensional Finite-element Analysis

Defects in Nickel-Titanium Instruments after Clinical Use. Part 2: Fractographic Analysis of Fractured Surface in a Cohort Study

“…The ProTaper Universal file with a reduced bending moment and increased flexibility was launched recently as an improvement to the original design. A mathematical simulation found that stress concentration was situated at the trailing edge adjacent to rather than at the cutting edge on the ProTaper Universal file (20). In theory, this could help to alleviate the combined effect of having both the greatest stress concentration and the site of rubbing contact with the root canal wall at the same location.…”

Comparison of Conventional and New-generation Nickel-Titanium Files in Regard to Their Physical Properties

“…These areas are especially vulnerable if those with the highest levels of stress coincide with the presence of machining marks or miniature grooves (16). Once the cracks are nucleated, their growth progresses slowly and seemingly along these machining grooves, at least initially, until the sudden, final fracture occurs (17,18).…”

Defects in Nickel-Titanium Instruments after Clinical Use. Part 1: Relationship between Observed Imperfections and Factors Leading to Such Defects in a Cohort Study

“…NiTi rotary files are available in a variety of designs, each with features that affect the manner in which they engage and cut dentin (7) and the stress that may generate within them (8,9). The safety of NiTi instruments in use requires an understanding of the basic mechanism for the development of defect and the factors involved (10,11).…”