Bone formation at titanium porous oxide (TiUnite™) oral implants in type IV bone

Background: Several oral implant design advances have been suggested to overcome poor bone quality, an impediment for successful implant treatment. A novel titanium porous oxide (TPO) surface has been shown to offer favorable results in several settings. The objective of this study was to evaluate the local bone formation and osseointegration at TPO-modified implants in type IV bone. Method: Three TPO surface-modified implants (TiUnite™) were installed into the edentulated posterior maxilla in each of 8 Cynomolgus monkeys. The animals were injected with fluorescent bone labels at 2, 3, 4 and 16 weeks post-surgery and were euthanized at week 16 when block biopsies were collected for histologic analysis. Results: The predominant observation of the TPO implant surface was a thin layer of new bone covering most of the implant threads. Mean (±SE) bone-implant contact for the whole study group was 74.1 ± 4.8%. There was a significant variability in bone-implant contact between animals (P = 0.0003) and between sites of the same animal (P<0.0001). The variance in bone-implant contact was 30% larger among sites of the same animal than between different animals (187.5 vs. 144.8, respectively). There was a small but significant difference in bone density immediately outside, compared to within the threaded area of the implants (37.1 ± 3.2% vs. 32.1 ± 3.2%, P<0.0001). Bone density outside the implant threads was significantly correlated (β = 0.682, P<0.0001) with the bone density within the threaded area. Bone density within the threaded area was significantly correlated (β = 0.493, P = 0.0002) with bone-implant contact, whereas bone density outside the implant threads did not have a significant effect (β = 0.232, P = 0.1). Conclusions: The results suggest that the TPO surface possesses a considerable osteoconductive potential promoting a high level of implant osseointegration in type IV bone in the posterior maxilla.