Topographic Quantification and Comparison of Titanium Implant and Osteoclast-Resorbed Human Bone Surfaces

Ay, Birol 1 ;  Davies, John E. 1, 2

1. Institute of Biomaterials and Biomedical Engineering (IBBME), University of Toronto, Toronto; 2. Faculty of Dentistry, University of Toronto, Toronto

Background: The osteoclast-resorbed bone surface is crucial for the anchorage of new bone during bone remodeling (1), and could serve as an ideal model for the development of candidate endosseous implant surfaces. Using scanning electron microscopy (SEM), image processing and fractal analysis (FA) we examined osteoclast-resorbed surfaces in human bone and compared them with a putative titanium oxide implant surface.

Hypothesis/Objectives: We hypothesized that FA could provide quantitative data to guide the design of putative implant surfaces.

Materials & Methods: An un-fixed, human cadaveric femur was sourced from the Anatomy Department, University of Toronto following REB approval. Residual soft tissue was removed by dissection and soaking in water. Bone slices were prepared (0.5 mm thick), and cut into 1x0.5 cm samples and disinfected using 70% ethanol. The samples were seeded with RAW 264.7 cells and incubated with a- MEM, containing 50ng/ml RANKL. After 14-day culture, cells were removed by sonication, and five different areas of osteoclast-resorbed bone surfaces and five identical nanostructured titanium dioxide (TiO2) nanotube implants were imaged by SEM. SEM images of resorbed human bone and nanotube surfaces were then rendered to create binary images from which average fractal dimensions (FD) were calculated using Image J 1.49v software.

Results: SEM images of the topographical structure in the individual (resorption pits) and consecutive depressions (resorption tracks) with scalloped edges demonstrated pores and irregular gaps between the collagen fibers. The average FD of this topographical structure was calculated as 1.778±0.01 while the average FD was 1.856±0.0006 in the nanotube implant surfaces.

Conclusions: The difference between FDs of the two surfaces were statistically significant (GraphPad, One-way ANOVA, p<0.05, n=5). Therefore, the nanotube features should be modified, during processing, to increase the pore diameter while maintaining the pore wall thickness to approximate more closely to the topography of resorbed bone.

Significance/Impact: This approach can act as a design guide for the optimization of surface modification of putative implant surfaces.

References: 1) Davies JE. J Dent Educ 2003;67(8):932-49.