Influence of Intra-Oral Temperature Changes on The Mechanical Properties of Different Nickel Titanium Orthodontic Arch-Wires

Authors

1 Assistant lecturer of Biomaterials, Biomaterial department, Faculty of Dentistry, 6 October University

2 Professor of Dental Biomaterials and Dean of Faculty of Dental Medicine for Girls, Al Azhar University

3 Professor and Head of Orthodontic department, Faculty of Dental Medicine for Girls, Al Azhar University

4 Assistant Professor of Mechanical Engineering, Faculty of Engineering for Boys, Al Azhar University

Abstract

Purpose: To evaluate and compare the effect of intra-oral temperature changes on the mechanical properties of three different NiTi orthodontic arch-wires. Materials and methods: A total of 45 specimens of three different 0.014-inch upper round NiTi orthodontic arch-wires, namely, 3M Nitinol Classic, 3M Nitinol Super-elastic, and 3M Nitinol Heat-activated were used in this study. Fifteen specimens from each wire type were subjected to a modified three-point bending test under three different temperatures (5, 37, and 55℃). Loads were plotted for 4, 3, 2, and 1mm deflections during unloading. Results: It was found that Nitinol Heat-activated shows the lowest mean load value followed by Nitinol Super-elastic and Nitinol Classic respectively, at 5, 37 and 55 ℃, for all deflections with exception at 1 mm deflection. At 37 ℃, Nitinol Super-elastic shows the highest mean value, while at 55 ℃, Nitinol Heat-activated shows the highest mean load value at 1mm deflection. Nitinol Heat-activated acquires the longest plateau of working force and the least plateau slope of the three wires. At 5 ℃, Nitinol Heat-activated exhibits diminished working force. The working force increases as the temperature increases from 5 ℃ to 55℃ and the working force plateau becomes more obvious as the temperature increases to 37 ℃ then tends to decrease again at 55 ℃. Conclusion: The low, constant working force offered by Nitinol Heat-activated arch-wire makes this wire favorable to the periodontal ligaments and improves the patient discomfort during orthodontic treatment. The working force of all of the three wires increases as the temperature rises.

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