Surface properties of Ti-35Nb-7Zr-5Ta: Effects of long-term immersion in artificial saliva and fluoride solution

Abstract

Statement of problem. The mechanical properties of new titanium alloys with an elastic modulus closest to cortical bone have been studied. However, potentially damaging conditions experienced in the oral cavity, such as fluoride ions, can initiate a localized or crevice process of corrosive degradation in the alloy surfaces. Purpose. The purpose of this in vitro study was to evaluate the effects of long-term immersion in artificial saliva or in fluoride solution on mean roughness (R-a), Vickers hardness, and topography of the new titanium alloy Ti-35Nb-7Zr-5Ta (TNZT) compared with those of cp Ti and Ti-6AI-4V (TAV). Material and methods. Disks (N=210) were divided into cp Ti, TAV, and TNZT and subdivided according to the following treatments: no immersion (N-, control), immersion in artificial saliva (S), and immersion in fluoride (F) during periods equivalent to 5, 10, 15, and 20 years. The R-a and Vickers hardness were measured with a profilometer and a hardness tester. The topography was analyzed by scanning electronic microscopy. Data were compared using the Kruskal-Wallis and Dunn tests (alpha=.05). Results. Values of R-a and hardness were significantly different among the metals (R-a: TAV<TNZT<cp Ti; P<.05); and hardness (cp Ti<TNZT<TAV; P<.05); with a tendency for R-a to increase for TAV after 20 years of fluoride immersion and changes in hardness values of TAV and TNZT after immersion. TAV surfaces showed a heterogeneous appearance. Conclusions. Long-term immersion in NaF did not change the roughness of Ti-35Nb-7Zr-5Ta. However, the hardness of the alloys increased with immersion.