Kusy R P, Ambrose W W, LaVanier L A, Newman J G, Whitley J Q
Department of Orthodontics, University of North Carolina, Building 210-H, Room 313, Chapel Hill, North Carolina 27599, USA.
J Biomed Mater Res. 2002 Oct;62(1):106-18. doi: 10.1002/jbm.10226.
Retainers were collected from private, university, and dental labs. After viewing these corroded and control appliances using scanning electron microscopy, corroded maxillary and mandibular retainers were selected along with a control stainless-steel retainer for in-depth chemical analysis. Using electron spectroscopy for chemical analysis, monochromated Al x-rays were rastered over areas 1.5 x 0.3 mm. After survey spectra were acquired, high-resolution multiplex scans were obtained and binding energy shifts were noted. Using Auger electron spectroscopy, a spot size of approximately 30 nm was analyzed. Photos, survey scans, and depth profiles were acquired using a 3.5kV Ar(+) ion beam that was calibrated using a SiO2 standard. Via electron spectroscopy for chemical analysis, the brown stains contained Fe and Cr decomposition products in which three carbon species were present. Proteinaceous N was found as amines or amides. No Ni was present because it had solubilized. The Cr:Fe ratio indicated severe Cr depletion in the stained regions (0.2) versus the control regions (1.3). The stained regions appeared mottled, having both dark and light areas. Via AES, the dark versus light areas of the stained regions indicated that there was an absence versus a presence of both Cr and Ni. In the dark areas corrosion penetrated 700 nm; in the light areas the depth equaled 30 nm. By comparison, the passivated layer of the control retainer was 10-nm thick. After sputtering away the affected areas, all specimens had similar spectra as the control regions. The bacterial environment created the mottled appearance and induced electrochemical potential differences so that, upon reducing the passivated layer, an otherwise corrosion-resistant alloy became susceptible to rampant corrosion. An integrated biological-biomaterial model is presented for the classic case of an orthodontic acrylic-based stainless steel retainer subject to crevice corrosion.
保持器取自私人诊所、大学和牙科实验室。使用扫描电子显微镜观察这些腐蚀的和对照矫治器后，选择腐蚀的上颌和下颌保持器以及一个对照不锈钢保持器进行深入化学分析。使用化学分析电子能谱，将单色Al X射线在1.5×0.3mm的区域上进行光栅扫描。获取 survey 光谱后，获得高分辨率多重扫描并记录结合能位移。使用俄歇电子能谱分析约30nm的光斑尺寸。使用3.5kV Ar(+)离子束获取照片、survey扫描和深度剖面图，该离子束使用SiO2标准进行校准。通过化学分析电子能谱，棕色污渍中含有铁和铬的分解产物，其中存在三种碳物种。发现蛋白质氮以胺或酰胺的形式存在。由于镍已溶解，所以不存在镍。铬与铁的比例表明，染色区域（0.2）与对照区域（1.3）相比存在严重的铬损耗。染色区域呈现斑驳状，有暗区和亮区。通过俄歇电子能谱，染色区域的暗区与亮区表明铬和镍的存在与否。在暗区，腐蚀穿透700nm；在亮区，深度为30nm。相比之下，对照保持器的钝化层厚度为10nm。溅射掉受影响区域后，所有标本的光谱与对照区域相似。细菌环境造成了斑驳外观并诱导了电化学电位差，因此，在减少钝化层后，原本耐腐蚀的合金变得容易受到剧烈腐蚀。针对正畸丙烯酸基不锈钢保持器发生缝隙腐蚀的经典案例，提出了一个综合的生物-生物材料模型。
