Microscopic Grain Structure Analysis of Titanium-based Orthodontic Archwires

Abstract

Introduction: Orthodontic archwires are designed to move teeth with light continuous forces. Great strides have been accomplished and are continuously evolving to produce the ‘perfect’ wire through complete knowledge of their metallurgical properties. Advent of shape memory alloys in orthodontics has been phenomenal. This study addresses the need of basic understanding of its micrograin structure. Materials and methods: Nickel-titanium and titanium molybdenum; archwires were selected. Each of the samples was studied using following equipments: Scanning electron microscopy and energy dispersive X-ray spectroscopy. Results: Surface topography of nickel-titanium alloys showed a highly rough surface with pits along with phases of intermetallic compounds of TiNi, Ni4Ti and Ti2Ni while titanium molybdenum alloys showed a highly porous surface topography. Precipitates of stabilizing elements were seen at the grain boundaries in both the alloys. Nickel-titanium alloys showed equiatomic concentrations of nickel and titanium with titanium to be slightly more than nickel. High percentage of interstitial elements like carbon, oxygen, etc. were detected; while titanium molybdenum showed maximum percentage of titanium followed by beta stabilizer, molybdenum and low concentrations of interstitial elements. Conclusion: Metallurgists are continuously experimenting with alloying elements to improve titanium alloys with consistent and predictable properties.