In vitro evaluation of the influence of velocity on sliding resistance of stainless steel arch wires in a self‐ligating orthodontic bracket

Structured Abstract Introduction Of the variables used by in vitro studies of resistance to sliding (RS) in orthodontics, sliding velocity (SV) of the wire is often the one farthest from its clinical counterpart. We investigated whether velocity influences theRSat values approximating the orthodontic movement. Methods ASSself‐ligating bracket with a NiTi clip was fixed onto a custom‐made model. Different shaped orthodonticSSwires of four sizes and two types (round, 0.020″ and 0.022″; rectangular, 0.016″×0.022″ and 0.017″×0.025″) were tested using an Instron®testing machine. Wires were pulled at four velocities (1×10−2 mm/s, 1×10−3 mm/s, 1×10−4 mm/s, 1×10−5 mm/s). Shapiro‐Wilk test was used to evaluate the normal distribution of the data; two‐wayANOVAwas performed to compare means in theRSwith wire characteristics andSV. Significance level was set atP<.05. Results RSwas higher for rectangular wires, and for those with larger diameters. LowerSVwas associated with lowerRS, with wire type and size having an interaction effect. TheRSrelatively toSVcan be represented as:RS∝ α[ln(SV)]+β, where α and β are constants. Conclusions At very lowSVand low normal forces,SVinfluences theRSofSSarchwires in orthodontic brackets, and the proportionality is logarithmic. Although respecting these parameters in vitro is challenging, quantitative evaluations ofRSshould be carried out at clinically relevant velocities if aiming at translational application in the clinical scenario.