The effect of discrete calcium phosphate nanocrystals on bone-bonding to titanium surfaces

We sought to address the question: Can metallic surfaces be rendered bone-bonding? We employed dual acid-etched (DAE) commercially pure titanium (cpTi) and titanium alloy (Ti6Al4V) custom-made rectangular coupons (1.3 mm x 2.5 mm x 4 mm) with, or without, further modification by the discrete crystalline deposition (DCD) of calcium phosphate (CAP) nanocrystals. A total of 48 implants comprising four groups were placed bilaterally in the distal femur of male Wistar rats for 9 days. After harvesting, the bone immediately proximal and distal to the implant was removed, resulting in a test sample comprising the implant with two attached cortical arches. The latter were distracted at 30 mm/min, in an Instron machine, and the disruption force was recorded. Results showed that alloy samples exhibited greater disruption forces than cpTi, and that DCD samples had statistically significantly greater average disruption forces than non-DCD samples. The bone-bonding phenomenon was visually evident by fracture of the cortical arches and an intact bone/implant interface. Field emission scanning electron microscopy showed the bone/implant interface was occupied by a bony cement line matrix that was interlocked with the surface topographical features of the implant. We conclude that titanium implant surfaces can be rendered bone-bonding by an increase in the complexity of the surface topography.