Ti-6Al-4V选择性溶解在整形外科植入物上作为点蚀攻击的前缘在体内发生。我们对选择性溶解的基本理解仍然存在差距,临床前测试无法重现这种损害。虽然CoCrMo临床使用减少,Ti-6Al-4V和可能发生腐蚀的缝隙几何形状在植入物设计中仍然普遍存在。此外,FDA批准的大多数增材制造设备使用Ti-6Al-4V。加速临床前测试,因此,将有助于评估新的钛设备和生物材料。在这项研究中,使用温度,我们(1)开发了一种加速的临床前方法来快速诱导溶解,(2)研究了溶解表面和氧化物层之间的结构-性质关系。我们假设溶液温度和H2O2浓度会加速氧化物降解,增加腐蚀动力学和减少实验时间。为了评估这种影响,我们选择高于(45°C)的温度,低于(24°C),和在(37°C)生理水平。然后,我们获得了活性β溶解过程中的电化学阻抗谱,显示随着时间(p=0.000)和温度升高(p=0.000),氧化物极化电阻(Rp)显着降低。接下来,使用阻抗响应作为指导,我们在扫描电子显微照片中量化了选择性溶解的程度。随着温度的升高,腐蚀速率以阿伦尼乌斯依赖的方式增加。最后,随着氧化物性质的变化,我们确定了三个表面类别:不溶解,过渡和溶解。这些结果表明,溶液之间存在浓度和温度依赖性结构-性质关系,保护性氧化膜,和基体合金。此外,我们展示了超生理温度如何在较短的实验时间内在37°C下运行的测试诱导结构相似的溶解。重要声明:在全髋关节置换系统的模块化锥形接头内,检索研究记录了严重的腐蚀,包括Ti-6AL-4V选择性溶解。当前的临床前测试和ASTM标准无法重现这种损害,防止钛基生物材料和植入物设计的准确筛选。在这项研究中,我们使用加速温度诱导选择性溶解。在以前的工作基础上,我们使用电化学阻抗谱来快速监测溶解过程中的氧化膜。我们阐明了溶解机制的组成部分,其中氧化物降解先于β相中的凹坑成核。使用阿伦尼乌斯方法,我们将这些加速测试条件与更生理相关的溶液浓度联系起来。总的来说,本研究显示了在临床前检测中包括阴极活化和炎症物质等不良电化学事件的重要性.
Ti-6Al-4V selective dissolution occurs in vivo on orthopedic implants as the leading edge of a pitting corrosion attack. A gap persists in our fundamental understanding of selective dissolution and pre-clinical tests fail to reproduce this damage. While CoCrMo clinical use decreases, Ti-6Al-4V and the crevice geometries where corrosion can occur remain ubiquitous in implant design. Additionally, most additively manufactured devices cleared by the FDA use Ti-6Al-4V. Accelerated preclinical testing, therefore, would aid in the evaluation of new titanium devices and biomaterials. In this study, using temperature, we (1) developed an accelerated pre-clinical methodology to rapidly induce dissolution and (2) investigated the structure-property relationship between the dissolving surface and the oxide layer. We hypothesized that solution temperature and H2O2 concentration would accelerate oxide degradation, increase corrosion kinetics and decrease experimental times. To assess this effect, we selected temperatures above (45 °C), below (24 °C), and at (37 °C) physiological levels. Then, we acquired electrochemical impedance spectra during active β dissolution, showing significant decreases in oxide polarization resistance (Rp) both over time (p = 0.000) and as temperature increased (p = 0.000). Next, using the impedance response as a guide, we quantified the extent of selective dissolution in scanning electron micrographs. As the temperature increased, the corrosion rate increased in an Arrhenius-dependent manner. Last, we identified three surface classes as the oxide properties changed: undissolved, transition and dissolved. These results indicate a concentration and temperature dependent structure-property relationship between the solution, the protective oxide film, and the substrate alloy. Additionally, we show how supraphysiological temperatures induce structurally similar dissolution to tests run at 37 °C in less experimental time. STATEMENT OF SIGNIFICANCE: Within modular taper junctions of total hip replacement systems, retrieval studies document severe corrosion including Ti-6AL-4V selective dissolution. Current pre-clinical tests and ASTM standards fail to reproduce this damage, preventing accurate screening of titanium-based biomaterials and implant designs. In this study, we induce selective dissolution using accelerated temperatures. Building off previous work, we use electrochemical impedance spectroscopy to rapidly monitor the oxide film during dissolution. We elucidate components of the dissolution mechanism, where oxide degradation precedes pit nucleation within the β phase. Using an Arrhenius approach, we relate these accelerated testing conditions to more physiologically relevant solution concentrations. In total, this study shows the importance of including adverse electrochemical events like cathodic activation and inflammatory species in pre-clinical testing.