Influence of fluoride-containing acidic artificial saliva on the mechanical properties of Nickel-Titanium orthodontics wires

• Published in: Indian journal of dental research 2012-09, Vol.23 (5), p.591-595
• Main Authors: Lin, Jun, Han, Shujuan, Zhu, Jiajun, Wang, Xiaoxiang, Chen, Yuan, Vollrath, Oliver, Wang, Huiming, Mehl, Christian
• Format: Article
• Language: English
• Subjects: Basketball players; Corrosion; Corrosion resistance; Crystal structure; Dental care; fluoride; Fluorides; microhardness; nickel; Nickel products; orthodontic wires; Orthodontics; Studies; surface morphology; three-point bending test; Titanium; Titanium alloys
• ISSN: 0970-9290; 1998-3603
• DOI: 10.4103/0970-9290.107332

Objective: This study aimed to investigate the influence of fluoride and an acidic environment on the mechanical properties of NiTi orthodontic wires (NiTiW) in artificial saliva. Design: A prospective laboratory investigation. Setting: Department of Stomatology, First Affiliated Hospital, Zhejiang University, Hangzhou, China. Materials and Methods: Commercial, round 0.016-inch NiTiW were immersed in 0% or 0.05% Natrium-Fluoride-containing artificial saliva at a pH of 4 or 6 for one or three days, respectively. NiTiW were examined with a three-point bending test, Vickers′ microhardness tests and surface morphology observation (SEM). Results: A pH of 4 increased microhardness and decreased the three-point bending strength significantly (P≤0.05), whereas immersion time and fluoride concentration had no significant influence on the microhardness or on the three-point bending strength (P>0.05). When examining the test group NiTiWs after three days of immersion at a pH of 4 the SEM revealed a rough surface morphology, a damaged oxide layer and signs of corrosion. Conclusions: The most influential factor for decreasing the unloading force and increasing the hardness seems to be the pH value, whereas immersion time and NaF addition do not have a major influence.