A comparison of bending and torsional properties of K‐files manufactured with different metallic alloys

Abstract

The purpose of this study was to compare bending (bending moment) and resistance to fracture by twisting (torsional moment and angular deflection) of triangular cross-section K-files made of either nickel titanium (Nitiflex, Naviflex), titanium (Microtitane) or stainless steel (Flexofile, Flex-R). A total of 200 files were tested, 10 instruments for each type from size 25 to 40, according to ANSI/ADA specification no. 28 and ISO reference no. 3630. Files made of nickel titanium, especially Nitiflex, were the most flexible. Stainless steel instruments presented a higher bending moment than files made of nickel titanium and titanium, particularly Flex-R sizes 35 and 40. With regard to resistance to fracture, measured by angular deflection at the failure point, Flexofile followed by Flex-R were the most resistant to fracture and Nitiflex were the least resistant. Differences in angular deflection among file groups were greater than those for torsional moment. Thus, it seems that angular deflection is a more specific measurement for assessing resistance to fracture by twisting.

Design Improvement and Failure Reduction of Endodontic Files through Finite Element Analysis: Application to V-Taper File Designs

“…Mainly due to the superelastic behavior of its base material of nitinol, NiTi files are more flexible than stainless steel files (1,2) and better preserve the canal anatomy with less canal aberrations such as zips, ledges, apical foramen transportation, or perforations (3)(4)(5). Despite these advantages, however, fracture of NiTi files remains a concern in clinical practices (6,7).…”

DISPOSITIVO PARA FLEXÃO ROTATIVA DE FIOS NiTi EM ENSAIO DE FADIGA

“…De acordo com Matheus et al (5) ao realizarem ensaios mecânicos em instrumentos endodônticos estabeleceu-se uma relação média de aumento do ângulo de torção máximo com o aumento do diâmetro nominal dos instrumentos de duas marcas comerciais. Todavia, para Campos e Pertot, (6) ,Canalda-Sahli, BrauAguadé e Berastegui-Jimeno (7) e Seto, Nicholls e Harrington, (8) o ângulo de torção máximo na fratura, para instrumentos manuais de NiTi, diminui com o aumento do diâmetro nominal do instrumento endodôntico, enquanto que, Carmo et al (9) afirmam que o ângulo de rotação não é influenciado pelo aumento do diâmetro do instrumento.…”

Mathematical Modeling of Flexural Behavior of Rotary Nickel-Titanium Endodontic Instruments

“…Ideally, the fracture resistance of an instrument within a curved root canal balances two failure modes (6): torsional and flexural failure (7)(8)(9). The former failure is associated in particular with binding of the instrument in the root canal lumen leading to a rise in the shear stress as the motor continues to drive the shaft.…”