Auger electron spectroscopic studies of the interface between human tissue and implants of titanium and stainless steel

Abstract

Auger electron spectroscopy has been used to study the interface between human tissue and implants of titanium and stainless steel. Both the thickness and the nature of the oxide layers on the implant have been found to change during the time of implantation. The stainless steel implants have a surface oxide about 50 Å in thickness prior to implantation. The metal atoms in the oxide are mainly chromium. The changes of the oxide thickness and nature depend on the location of the implant in the body. For implants located in cortical bone, the thickness of the interfacial oxide layer remains unaffected, while it increases by a factor of 3–4 on samples located in bone marrow. In both these cases, calcium and phosphorus are incorporated in the oxides. Implants located in soft tissue have an interfacial oxide with a thickness of about one and a half times that of an unimplanted sample. On these samples, calcium and phosphorus are not incorporated in the oxide layer. Also for titanium an increase in oxide thickness and an incorporation of Ca and P are found. In the cases with titanium implants, it is also demonstrated that the oxidation process occurs over a long period of time, up to several years. For the elements incorporated in these interfacial oxide layers on both stainless-steel and titanium implants, it is found that P is strongly bound to oxygen suggesting the presence of phosphate groups in the oxides. The interaction between the implants and human tissue are discussed in terms oxygen pressure, electron transfer between proteins and implants, metabolic activity, and enzymes producing free radicals.