Oshida Y, Hashem A
Department of Restorative Dentistry, Indiana University School of Dentistry, Indianapolis 46202-5186.
Biomed Mater Eng. 1993 Winter;3(4):185-98.
The bonding strength of porcelains to metals depends on the oxide layer between the porcelain and the metal. Oxidation of a metal surface increases the bonding strength, whereas excessive oxidation decreases it. Titanium and its alloys are gaining acceptance for dental use since they exhibit excellent biocompatibility, corrosion resistance, low specific gravity, good mechanical properties, and low cost. However, titanium suffers from its violent reactivity with oxygen at high temperatures that yields an excessive thick layer of TiO2, and this presents difficulties with porcelain bonding. The present study deals with the oxidation kinetics of titanium simulated to porcelain firing and evaluating surface nitridation of titanium as a process of controlling the oxidation behavior of titanium. Nitrided samples with the Arc Ion Plating PVD process and un-nitrided control commercially pure titanium (CPT, Grade 1) were subjected to oxidation simulating firing of Procera porcelain with 550 degrees, 700 degrees, and 800 degrees C firing temperatures for 10 min in both 1 and 0.1 atmospheric air. Weight difference before and after oxidation was calculated and the parabolic rate constant, Kp (mg2/cm4/s), was plotted against inverse absolute temperature. Surface layers of the samples were subjected to x-ray and electron diffraction techniques for phase identifications. Results revealed that both nitrided and un-nitrided samples obey a parabolic rate law with activation energy of 50 kcal/mol. In addition this study shows that nitrided CPT had a Kp about 5 times lower than the un-nitrided CPT and hence the former needs about 2.24 times longer oxidation time to show the same degree of oxidation. Phase identification resulted in confirming the presence of TiO2 as the oxide film in both groups but with 1-2 microns thickness for the un-nitrided CPT and 0.3-0.5 micron thickness for the nitrided samples. Therefore it can be concluded that nitridation of titanium surface can be effective in controlling the surface oxide thickness that might ensure satisfactory bonding with porcelain.
陶瓷与金属之间的结合强度取决于陶瓷与金属之间的氧化层。金属表面的氧化会增加结合强度，而过度氧化则会降低结合强度。钛及其合金因其具有优异的生物相容性、耐腐蚀性、低比重、良好的机械性能和低成本而逐渐被用于牙科领域。然而，钛在高温下与氧气反应剧烈，会产生过厚的TiO₂层，这给陶瓷结合带来了困难。本研究探讨了模拟烤瓷烧制过程中钛的氧化动力学，并评估了钛的表面氮化作为控制钛氧化行为的一种方法。采用电弧离子镀物理气相沉积（PVD）工艺对氮化样品和未氮化的商业纯钛（CPT，1级）对照样品进行处理，将其在1个大气压和0.1个大气压的空气中，分别在550℃、700℃和800℃的烧制温度下氧化模拟Procera烤瓷10分钟。计算氧化前后的重量差，并绘制抛物线速率常数Kp（mg²/cm⁴/s）与绝对温度倒数的关系图。对样品的表面层进行X射线和电子衍射技术分析以进行相鉴定。结果表明，氮化和未氮化样品均遵循抛物线速率定律，活化能为50千卡/摩尔。此外，本研究表明，氮化CPT的Kp约为未氮化CPT的五分之一，因此前者需要约2.24倍长的氧化时间才能达到相同的氧化程度。相鉴定结果证实两组样品中均存在TiO₂作为氧化膜，但未氮化CPT的氧化膜厚度为1 - 2微米，氮化样品的氧化膜厚度为0.3 - 0.5微米。因此，可以得出结论，钛表面氮化可有效控制表面氧化物厚度，从而确保与陶瓷的良好结合。
