Oxidized implants and their influence on the bone response

Surface oxide properties are regarded to be of great importance in establis hing successful osseointegration of titanium implants. Despite a large numb er of theoretical questions on the precise role of oxide properties of tita nium implants, current knowledge obtained from in vivo studies is lacking. The present study is designed to address two aspects. The first is to verif y whether oxide properties of titanium implants indeed influence the in viv o bone tissue responses. The second, is to investigate what oxide propertie s underline such bone tissue responses. For these purposes, screw-shaped/tu rned implants have been prepared by electrochemical oxidation methods, resu lting in a wide range of oxide properties in terms of: (i) oxide thickness ranging from 200 to 1000 nm, (ii) the surface morphology of barrier and por ous oxide film structures, (iii) micro pore configuration - pore sizes <8 m um by length, about 1.27 mum(2) to 2.1 mum(2) by area and porosity of about 12.7-24.4%, (iv) the crystal structures of amorphous, anatase and mixtures of anatase and rutile type, (v) the chemical compositions of TiO2 and fina lly, (vi) surface roughness of 0.96-1.03 mum (Sa). These implant oxide prop erties were divided into test implant samples of Group II, III, IV and V. C ontrol samples (Group I) were turned commercially pure titanium implants. Q uantitative bone tissue responses were evaluated biomechanically by resonan ce frequency analysis (RFA) and removal torque (RT) test. Quantitative hist omorphometric analyses and qualitative enzyme histochemical detection of al kaline (ALP) and acidic phosphatase (ACP) activities were investigated on c ut and ground sections after six weeks of implant insertion in rabbit tibia . In essence, from the biomechanical and quantitative histomorphometric mea surements we concluded that oxide properties of titanium implants, i.e. the oxide thickness, the microporous structure, and the crystallinity signific antly influence the bone tissue response. At this stage, however, it is not clear whether oxide properties influence the bone tissue response separate ly or synergistically. (C) 2001 Kluwer Academic Publishers.