Influence of various fluoride agents on working properties and surface characteristics of uncoated, rhodium coated and nitrified nickel-titanium orthodontic wires

Abstract

Objective. To analyze the effect of various fluoride formulations in commercially available agents on working properties of various nickel-titanium orthodontic wires. Materials and methods. Uncoated (NiTi), rhodium coated (RhNiTi) and nitrified (NNiTi) wires were immersed to dH₂O, MiPaste, Elmex and Mirafluor for 1 h. Unloading slope characteristics (average force, bending action of the force and average plateau length) and the percentage of useable constant force during unloading were observed. Surface roughness (R_a) was measured. SEM and EDS were used for observation of the surface. Results. NiTi had decreased loading and unloading elastic modulus (E) and yield strength (YS) after immersion to MIPaste and Mirafluor. The unloading YS decreased in the RhNiTi by the MIPaste. The loading and unloading YS of the NNiTi increased in Elmex and increased average plateau force. RhNiTi showed higher average plateau length and the percentage of useful constant force during unloading in Mirafluor and the average plateau force lowered after immersion to MIPaste. The unloading slope characteristics for NiTi were affected by all three prophylactic agents, mostly by Mirafluor, and produced significantly lower forces during both loading and unloading, similarly to the NNiTi wires. The RhNiTi had the lowest forces during both loading and unloading in MIPaste. All results were at significance; p < 0.05. Difference in R_a was observed for RhNiTi after immersion to the MI Paste (p < 0.001; η² = 0.761). Conclusion. The NiTi and NNiTi wires lose less working force when combined with Elmex. The RhNiTi improve their working properties with Mirafluor and deteriorate when combined with MiPaste.

Key Words:

• corrosion
• orthodontic appliance
• roughness
• chemically induced
• stress
• mechanical

Acknowledgment

This research is part of the University of Rijeka research project 13.06.2.1.53, principal investigator Stjepan Špalj. Our deepest gratitude goes to Professor Branko Tripalo, whose advices enabled conduct of this research. We thank Davor Mandić, mag. ing. mech. at ‘IDA-Metris Pula’ for the SEM and EDS analysis.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.