Treatment of Class II malocclusion with the improved superelastic nickel-titanium alloy wire and long hooks for mandibular molar protraction

Abstract

• Two patients were treated with extraction of the mandibular second premolars. • We used superelastic nickel-titanium alloy wires as working wires. • The use of nickel-titanium wires and long hooks worked to mesialize the molar bodily. The mandibular first molar must be carefully moved to prevent mesial tipping and extrusion in case extraction of the mandibular second premolar is required to achieve the desired goals. The nickel-titanium alloy has unique mechanical properties, including superelasticity and shape memory, leading to the generation of continuous light forces that may be more biologically compatible than intermittent strong forces. However, it provides poor root control because of its low stiffness. We herein have experienced the patients with Angle Class II malocclusion that uses the improved superelastic nickel-titanium wire (ISW) and long hooks to achieve bodily movement of the mandibular first molar. The 0.022 × 0.028-in slot preadjusted edgewise appliances and 0.020 × 0.025-in ISWs as the working archwire were used. We pinched the crimpable long hooks on the rectangular ISW and applied 100-150 g of contractile force between the fixed long hooks and bracket hooks of the mandibular first molars to activate the system with ligature wire lacing. The mandibular molars were uprighted and mesially moved; panoramic radiographs did not indicate severe root resorption. These experiences suggest that this method involving the combined use of the ISW and long hooks may be one of the useful methods for closing spaces by facilitating the uprighting and mesial movement of the molars in treating Class II malocclusion.