An experimental evaluation of a new craniofacial implant using the rabbit tibia model: part I. Histologic findings.

Hypothesis: This experimental study was undertaken to test the hypothesis that a new design of craniofacial implant shows a stronger tissue response than the currently used implant.
Materials and Methods: A total of 60 newly designed Cochlear Baha BI300 titanium implants (test) and 60 of the current design (control) were placed in the tibiae of 30 adult loop-eared rabbits. The new implant had the surface modified by blasting with TiO2 particles to give a moderately rough surface topography. The control implant had an as-machined surface. The animals were euthanized after 5, 14, or 28 days. The implants with surrounding bone tissue were retrieved for descriptive histology and morphometric measurements of bone-implant contacts (BICs).
Results: The test implants showed integration through bone formation direct on the surface and ingrowth from the vicinity. Conversely, the control implants showed increased BICs because of ingrowth of bone from the adjacent bone surfaces only. The test implant showed significantly more BICs at all time points.
Conclusion: It is concluded that the new craniofacial implant with a moderately rough surface showed integration through a contact-osteogenesis pathway, whereas the smoother control surface was integrated by distance osteogenesis. More bone contacts were seen for test implants and, thus, a stronger bone tissue response compared with control implants. Biomechanical tests are needed to also evaluate the impact of the different histologic responses on implant stability.