Experimental Analysis of the Influence of Heat Treatments on the Flexibility of NiTi Alloy for Endodontic Instruments Manufacturing

Abstract

The flexibility of NiTi based endodontic files is improved by heat treatment, leading to lower risk of failure, ledges, and canal transportation during the preparation of curved root canals. The aim of this study is to investigate and clearly highlight the influence of every parameter of heat treatment on the flexibility of NiTi wires and thus of endodontic instruments. A full factorial Design of Experiment (DoE) and a designed bending–torsion bench following the ISO 3630-1 standard were used for this investigation. Temperature, holding time, and cooling method were selected as contributing factors, while maximum bending moment, hysteresis size, and stiffness during martensitic transformation were selected as outputs. Regression analysis was performed to estimate the relationship between contributing and output variables to assess how the experimentation fits with the model. The experimental results showed that wires heated at 425 °C for 30 min are more flexible. Moreover, heat treatment temperature is the most critical factor influencing the flexibility and hysteresis size of the NiTi wire followed by the holding time, while the cooling method has a negligible effect. The regression analysis showed that the model is effective at predicting the relationship between contributing factors, bending moment response, and hysteresis size.

Scanning Electron Microscopic Analysis of Deformation of TruNatomy File Systems: An Ex-vivo Study

“…A wide range of instrumentation system types, designs, and surface modifications have been done to instruments to prevent the inherent cyclic and torsional fatigue [4]. NiTi alloys with various surface treatments have been produced in recent years with improved mechanical properties and clinical efficiency [5]. Thermal processing methods changed NiTi alloy transition temperatures [6].…”

Influence of Endodontic Motors on the Behaviour of Root Canal Shaping Instruments: An in Vitro Comparative Study

“…[1][2][3] In this context, instrumental developments in terms of materials [4][5][6] , geometries [7][8][9][10][11][12] , kinematics [13][14][15][16][17][18][19][20][21][22] , surface 5,[23][24][25][26][27] and thermal treatments [28][29][30][31][32][33] have gradually allowed to offer more reproducible endodontic treatments. By taking these different parameters one by one as variable, several mechanical and preclinical studies have made it possible to compare these instruments in terms of exibility 10,28,[34][35][36][37][38][39][40][41][42][43][44][45][46] , cyclic fatigue 19,[36][37]…”