Materials 2013, 6, 5258-5274; doi:10.3390/ma6115258 materials ISSN 1996-1944 www.mdpi.com/journal/materials Article Titanium Corrosion Mechanisms in the Oral Environment: A Retrieval Study Danieli C. Rodrigues 1, *, Pilar Valderrama 2 , Thomas G. Wilson, Jr. 3 , Kelli Palmer 4 , Anie Thomas 1 , Sathyanarayanan Sridhar 1 , Arvind Adapalli 1 , Maria Burbano 1 and Chandur Wadhwani 5 1 Department of Bioengineering, University of Texas at Dallas, 800 W Campbell Rd, Richardson, TX 75080, USA; E-Mails: axt012600@utdallas.edu (A.T.); sxs125031@utdallas.edu (S.S.); apa103020@utdallas.edu (A.A.); mxb121131@utdallas.edu (M.B.) 2 Department of Periodontics, Texas A&M University Baylor College of Dentistry, 3302 Gaston Av, Dallas, TX 75246, USA; E-Mail: valderrama@bcd.tamhsc.edu 3 Private Practice of Periodontics, 5465 Blair Road suite 200, Dallas, TX 75231, USA; E-Mail: tom@northdallasdh.com 4 Department of Molecular and Cell Biology, University of Texas at Dallas, 800 W Campbell Rd, Richardson, TX 75080, USA; E-Mail: kelli.palmer@utdallas.edu 5 Department of Restorative Dentistry, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA; E-Mail: cpkw1@live.com * Author to whom correspondence should be addressed; E-Mail: danieli@utdallas.edu; Tel.: +1-972-883-4703; Fax: +1-972-883-4653. Received: 2 October 2013; in revised form: 25 October 2013 / Accepted: 28 October 2013 / Published: 15 November 2013 Abstract: Corrosion of titanium dental implants has been associated with implant failure and is considered one of the triggering factors for peri-implantitis. This corrosion is concerning, because a large amount of metal ions and debris are generated in this process, the accumulation of which may lead to adverse tissue reactions in vivo. The goal of this study is to investigate the mechanisms for implant degradation by evaluating the surface of five titanium dental implants retrieved due to peri-implantitis. The results demonstrated that all the implants were subjected to very acidic environments, which, in combination with normal implant loading, led to cases of severe implant discoloration, pitting attack, cracking and fretting-crevice corrosion. The results suggest that acidic environments induced by bacterial biofilms and/or inflammatory processes may trigger oxidation of the surface of titanium dental implants. The corrosive process can lead to permanent OPEN ACCESS