Methods and models to study nickel–titanium instruments

Abstract

Over the past two decades, nickel–titanium (NiTi) instruments have become an important part of the armamentarium for root canal treatment. They are increasingly used by generalists and specialists to facilitate the cleaning and shaping of root canals. Despite the advertising claims of superiority of design for some NiTi rotary systems, few have been supported by objective well‐designed studies in the literature. A variety of experiments with different models and methods have been developed for studying the properties of NiTi instruments and how they fulfil these mechanical goals. One of the main issues is how to make a rational choice for the best study model that is relevant. This article aims to present an overview of those methods and devices that have been used in endodontic literature for studying NiTi files.

Fatigue and nanomechanical properties of K3XF nickel‐titanium instruments

“…However, the K3XF prototypes demonstrated a significant increase in cyclic fatigue resistance. Possible reasons for these conflicting findings are different experimental settings and different NiTi instruments (Shen & Cheung ).…”

A critical appraisal of studies on cyclic fatigue resistance of engine‐driven endodontic instruments

“…Usually, resistance to cyclic fatigue is measured as the number of rotations/cycles until fracture (NRF/NCF) or as time to fracture. Such studies mainly are performed in metal tubes with defined curvatures (angle, length and radius of curvature), filled with a lubricant, thus preventing torsional load, although different study designs also have been developed such as rotation against a plane, three-point bending tests or block-and-rod assemblies (Plotino et al 2009, Shen & Cheung 2013. In some studies, a 3-pin model has H€ ulsmann et al Instrument fatigue studies International Endodontic Journal, 52, 1427-1445, 2019 been used instead of the tube model (Cheung & Darvell 2007a,b, Tokita et al 2017.…”

“…Topics of major interest of these instruments include bending properties and flexibility, cutting efficacy and safety of use/fracture resistance (Hülsmann et al ). As the main reasons for instrument fractures are torsional overload or cyclic fatigue – or even a combination of both – many studies describe the torsional or cyclic fatigue behaviour of instruments (Wei et al , Shen et al ,b,c, Shen & Cheung ); in fact, one of the first on cyclic fatigue behaviour of LightSpeed instruments dates from as far back as 1997 (Pruett et al ). The basic requirements for testing endodontic instruments are defined in the revised ADA Specification No.…”

A comparison of two reciprocating instruments using bending stress and cyclic fatigue tests

“…Similarly, the ranges of simulated canals with different angles and radii of curvature are large, as is the range of materials examined, which vary from acrylic resin blocks to metal tubes and conformations of canal models using electroerosion. 23,24,25 In this study, a battery of tests was performed to measure flexibility to 45°. In the traction machine, the vertical displacement of the instrument was 15.55 mm, a value obtained using trigonometry (sin 45°).…”