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.