Based on Phase I results, Ti-Mo-Al alloys exhibit the best combination of superelastic springback, low modulus and ductility, and good potential as a new orthodontic alloy. In the short period of Phase I, optimization of the alloy composition and thermal mechanical processing was not possible. Phase II research will concentrate on Ti-Mo-Al based alloys, modifying the composition to meet the requirements of a superior orthodontic wire. Composition and processing optimization will employ a multi-component alloy design procedure using a partial factorial statistical experiment design to identify the relative importance of composition, heat-treatment and hot and cold working. The high temperature reactivity of titanium alloys creates problems in processing and heat treatment; practical processing procedures will be developed. Fundamental alloy metallurgy will be studied with respect to alloy microstructure and phase transformation kinetics. Particularly important in Phase II is the development of scaled-up alloy processing to validate the properties measured on laboratory specimens using ingots processed by techniques closer to commercial practice. The details of the effect of heat treatment on superelasticity and modulus will be determined for the optimized alloy, and the practical limits to their clinical control. Properties important to the orthodontist such as bend ductility, wire forming and weldability, will be determined on alloy wire produced from the larger scale ingot. Arch wires will be fabricated using accepted heat treating and polishing techniques to demonstrate the practicality of the final alloy selection and wire processing.
