214 Australian Dental Journal 2002;47:3. A study of titanium release into body organs following the insertion of single threaded screw implants into the mandibles of sheep KW Frisken,* GW Dandie,† S Lugowski,‡ G Jordan§ Abstract Background: Titanium is generally considered a safe metal to use in implantation but some studies have suggested that particulate titanium may cause health problems either at the site overlying the implant or in distant organs, particularly after frictional wear of a medical prosthesis. It was the purpose of this investigation to study the levels of dissemination of titanium from threaded screw type implants follow- ing placement of single implants in sheep mandibles. Method: Twelve sheep were implanted with a single 10x3.75mm self-tapping implant for time intervals of one, four and eight to 12 weeks. Four unoperated sheep served as controls. Regional lymph nodes, lungs, spleens and livers were dissected, frozen and subsequently analysed by Graphite Furnace Atomic Absorption Spectroscopy. Results: Results associated with successful implants showed no statistically significant different levels of titanium in any organ compared to controls, although some minor elevations in titanium levels within the lungs and regional lymph nodes were noted. Two implants failed to integrate and these showed higher levels of titanium in the lungs (2.2- 3.8 times the mean of the controls) and regional lymph nodes (7-9.4 times the levels in controls). Conclusions: Debris from a single implant insertion is at such a low level that it is unlikely to pose a health problem. Even though the number of failed implants was low, multiple failed implants may result in considerably more titanium release which can track through the regional lymph nodes. Results suggest that sheep would be an excellent model for following biological changes associated with successful and failed implants and the effect this may have on titanium release. Key words: Titanium, sheep, body organs. (Accepted for publication 12 December 2001.) INTRODUCTION Titanium is generally accepted to be a relatively inert substance with minimal side effects. 1-3 However, evidence in the literature suggests that under some circumstances, the presence of titanium particles may be harmful, especially following frictional wear of medical prostheses or of screws such as those used in plate fixation during surgical procedures. 4,5 Aggressive soft tissue reactions with black extracellular deposits and titanium particles within histiocytes and foreign body giant cells have been observed resulting from rough surface titanium alloy medical prostheses or those which have loosened. 4,6 Elevated serum levels have also been reported for loose devices. 7 Titanium particles have also been implicated in the development of histiocytotic lesions in regional lymph nodes. 8 Some further side effects can include dark staining in the tissue around titanium. 6,9 This has led to concern about the long term metabolic, oncogenic and immunologic effects of titanium particles. 4 Further reports in the medical literature suggest that metal debris may be a contributing factor in component loosening and failure. 4,6 Lalor et al. 10 have shown a macrophage reaction with a large T-lymphocyte response, with absence of plasma cells suggesting an immunological reaction such as type IV hypersensitivity may be involved in this process. They and others suggested that sensitization to titanium may have contributed to the failure of medical prostheses. 4,10 The exact mechanism for titanium release is not clear, but early reports by Ferguson 11-13 showed that ionization of all metal occurs to some extent and titanium may be released in relatively large concentrations into adjacent tissues. 14 Some reports in the dental literature show that frank particles can be found locally after using titanium screwtaps in the placement of smooth surfaced threaded screw type implants. 15-17 Fragments can also be found extracellularly in tissue over plates and screws used in surgery. 16 As well as local release, several reports describe the presence of titanium particles in regional lymph nodes as a result of insertion procedures and/or corrosion. 18-20 *Private Practice, Tasmania and Department of Anatomy, The University of Tasmania. †Department of Pathology, The University of Tasmania. ‡Department of Biomaterials, Faculty of Dentistry, University of Toronto, Canada. §School of Plant Science, The University of Tasmania. Australian Dental Journal 2002;47:(3):214-217 ADRF RESEARCH REPORT