In vitro and in vivo behaviour of Ca- and P-enriched anodized titanium

The influence of different surface preparations on titanium biocompatibilit y and bone integration was evaluated. Commercially grade 2 titanium rods (e mpty set 2 mm, length: 3 mm), vacuum annealed and hydrofluoric acid etched was selected for its promising surface characteristics to achieve good dire ct osseointegration. Some rods were surface modified by Anodic Spark Discha rge anodization and a thin layer (approximate to 5 mu m) of amorphous TiO2 containing Ca and P (Ti/AM) was obtained. Some of the Ti/AM specimens under went a further hydrothermal treatment to produce a thin outermost layer (ap proximate to 1 mu m) of hydroxyapatite (Ti/AM/HA). Cytotoxicity tests (dire ct contact: ISO 10993-5) showed good cytocompatibility for all tested sampl es. Ti and tissue culture substrate + DMEM control, respectively, were asso ciated with a significant higher proportion of attached cells than Ti/AM an d Ti/AM/HA (P < 0.0005), but this was in the normal range of 10-20% of unat tached cells for cytocompatible materials. Histomorphometric analysis condu cted on samples inserted in the cancellous bone of distal femoral epiphysis of Sprague-Dawley rats gave the following results at 4 and 8 weeks: Affini ty index (AI%) data proving the surface osteconductive properties of non-an odized acid etched Ti (AI-4 weeks: 67.1 +/- 17.0%; AI-8 weeks: 74.8 +/- 11. 5%). Ti/AM samples showed the lowest values (AI-4 weeks: 45.8 +/- 15.9%; AI -8 weeks: 68.5 +/- 13.6%) while the best performances of the Ti/AM/HA sampl es (AI-4 weeks: 60.4 +/- 21.8%; AI-8 weeks: 79.5 +/- 9.37%) indicated that hydroxyapatite allowed a higher bone to implant contact respect to Ti only. Further investigations should be performed in order to better understand t he mechanism of observed in vitro behaviour and to achieve information on l ong-term osseointegration process. (C) 1999 Elsevier Science Ltd. All right s reserved.