In-vivo characteristics of metallic arch wires in orthodontics

Background: The purpose of this study was to analyse the elements (Ti, Ni, Si, Al, Mn, Fe, Cr) in orthodontic wires during orthodontic therapy in a clinical cohort. Saliva simultaneous liquids are not accurately comparable with human saliva, so there is a need for this study. (ELIADES, et al. 2002) In addition, the connection between the intraoral period, other intraoral appliances, and the oral hygiene was observed, because these parameters have a secondary influence on the corrosion of wires. (ELIADES, et al. 2005). Purpose: The aim of the following study was to quantify ion leaching from orthodontic wires in relation to time, oral hygiene, and other co-factors. Material/Methods: Data from 50 stainless steel- (SS) and 50 nickel-titanium-wires (NiTi) (Forestadent Bernhardt Förster GmbH) from 100 patients during a normal orthodontic treatment in the Department of Orthodontic at the University of Greifswald were collected and prospectively analysed. Additionally, the type and number of fillings and the plaque index (PI) were registered. With an energy-dispersive X-ray spectroscopy (EDS), the distribution of nickel, chromium, and titanium was compared before and after a special period of intraoral time. The surface of all wires was observed subjectively. Statistically, a t-test and u-test were used (p ≤ 0.05). The influences of a different intraoral time and oral hygiene were analysed using linear regression analysis. Results: On average, all wires were 61.9 days in the oral cavity. The mean age of the patients was 14.6 years, and they had in average of 1.26 fillings. 70% of the kids didn't have any fillings during this study. Every patient had on average 3.2 orthodontic bands on the molars, and 48% were treated with a self-ligating braces system. We had 22 TPA's and 5 LLA's. The EDS analysis showed no significant difference in the distribution of the collected elements irrespective of the plaque index and the intraoral time of these wires. Even with other orthodontic appliances and the number of fillings, there was no significant difference in the number of elements before and after a period of time in a patient's mouth. In addition self-ligating as well as conventional braces showed no differences in the distribution of nickel, chromium, titanium, and other elements. Conclusion: A higher plaque index caused by moderate oral hygiene during an orthodontic treatment and a longer intraoral treatment time of wires do not significantly increase the risk of corrosion of nickel, chromium, titanium, and other elements in orthodontic alloys. The differences between the original and used wires were within a single-digit percent range and showed no significance (p ≤ 0.05). In addition, the type of braces, other intraoral appliances, and the number of fillings did not significantly influence the stainless steel- and nickel-titanium-wires. Nevertheless, visual differences on the surface of all probes could be detected. Keywords: Biomaterials, Ion release, Corrosion, Nickel