Staffolani N, Damiani F, Lilli C, Guerra M, Staffolani N J, Belcastro S, Locci P
Institute of Clinical Odontology, University of Perugia, Italy.
J Dent. 1999 Aug;27(6):449-54. doi: 10.1016/s0300-5712(98)00073-6.
The microbiological and enzymatic characteristics of the oral cavity would seem to provide a suitable environment for the corrosion of metals. We assayed the release of metal ions from one orthodontic appliance which included two 304 and 316 steel molar bands, ten 316 steel brackets, one nickel-titanium archwire and a brazing alloy to connect the elements of molar bands and brackets.
The orthodontic appliance was dipped in both inorganic (pH 3.5-6.5) and organic acid solutions (w/v 1% each of tartaric, citric and ascorbic acid at pH 2.2 or 1.5% each of lactic and acetic acid at pH 2.5). The release of nickel (Ni), chromium (Cr), copper (Cu), silver (Ag) and palladium (Pd) was determined using an atomic absorption spectrophotometer Varian AA 10.
The release of Ni, Cr and Cu was markedly less at pH 6.5 than at pH 3.5 at all time points in acid solution. Daily release/single appliance after the first day decreased. Contrary to expectations, appliances immersed in organic acid solutions at pH 2.2 or 2.5 after 28 days generally released an amount of ions similar to that observed in inorganic acid solution at pH 3.5, with the exception of Cu. Release of silver and palladium, two metals present in the brazing alloy, proved to be very low (approximately 0.2 microgram after 28 days).
The daily release of Ni, Cu and Cr by an orthodontic appliance in acid pH, particularly favourable to corrosion, was well below that ingested with a normal daily diet. It is therefore concluded that the quantities of metal ions released in our experimental conditions should not be cause for concern in utilising the appliance.
口腔的微生物学和酶学特性似乎为金属腐蚀提供了适宜的环境。我们测定了一种正畸矫治器中金属离子的释放情况，该矫治器包括两个304和316不锈钢磨牙带环、十个316不锈钢托槽、一根镍钛弓丝以及一种用于连接磨牙带环和托槽各部件的钎焊合金。
将正畸矫治器浸泡在无机酸溶液（pH值为3.5 - 6.5）和有机酸溶液中（酒石酸、柠檬酸和抗坏血酸各1%（w/v），pH值为2.2；乳酸和乙酸各1.5%（w/v），pH值为2.5）。使用瓦里安AA 10原子吸收分光光度计测定镍（Ni）、铬（Cr）、铜（Cu）、银（Ag）和钯（Pd）的释放量。
在酸性溶液中，所有时间点pH值为6.5时Ni、Cr和Cu的释放量均明显低于pH值为3.5时。第一天后单个矫治器的每日释放量减少。与预期相反，在28天后浸泡在pH值为2.2或2.5的有机酸溶液中的矫治器，除Cu外，通常释放的离子量与在pH值为3.5的无机酸溶液中观察到的相似。钎焊合金中所含的银和钯的释放量非常低（28天后约为0.2微克）。
正畸矫治器在酸性pH值（特别有利于腐蚀）条件下每日释放的Ni、Cu和Cr量远低于正常日常饮食摄入的量。因此得出结论，在我们的实验条件下释放的金属离子量在使用该矫治器时无需担忧。
