To investigate the osteogenic properties of surface modified titanium in vitro and in vivo.
Method:
3 different titanium surface modifications (6.25mm in diameter): machined (M), titanium oxide blasted (TOB, TiOBlast, Dentsply Implants), and titanium oxide blasted and etched with hydrofluoric acid (OSS, Osseospeed, Dentsply Implants) were used. Surfaces were examined under high power SEM and surface chemistry analysed with XPS. Osteogenesis was investigated in vivo in the mandible of 9 sheep. The sheep were sacrificed at 2, 5, and 10 weeks with an overdose of sodium-pentothal, and histomorphometric analysis was carried out. In vitroexperiments were utilized to determine the molecular mechanisms promoting osteogenesis. PCR array and RT-PCR were used to interrogate the expression of major markers of Wnt pathway and osteoblast differentiation. Western blot and immunofluorescence were used to confirm the location and expression of β-catenin protein.
Result:
SEM and XPS analysis demonstrated different surface characteristics between the three implant types. In vivo experiments showed new bone formation on the OSS surface as early as 2 weeks post healing, but not on TOB or machined surfaces. At 5 weeks the bone to implant contact (BIC) was 7.4%±2.8 for M, 26%±3 TOB and 52%±14 for OSS; while at 10 weeks it was 18%±4.3 for M, 25%±1.3 for TOB and 70%±5.8 for OSS. At both 5 and 10 weeks BIC was significantly higher for Osseospeed and Tioblast than machined surfaces. Expression of β-catenin and key osteoblast markers are detected in human mesenchymal stem cell (hMSC) cultured on modified titanium surfaces. β-catenin protein is also detected via immunofluorescence and western blot.
Conclusion:
Osseospeed and TiOblast surfaces demonstrated superior osteogenesis when compared to machined surfaces in vivo. Expression of β-catenin suggests that it plays a role in the signalling events leading to the expression of osteoblast markers.