High resolution SAXS/WAXS characterization of the cement line, a thin interface protecting osteonal bone.

Bone toughness depends on the many interfaces joining the different structural units of bone. Among these, cement lines are thin layers separating osteons from the surrounding bone. Cement lines are still one of the least understood features of our bones; yet these structures are believed to play a key role in bone fracture resistance. The main aim of this research is to characterize the mineral properties of cement lines by small and wide angle x-ray scattering with (sub)micrometer resolution to test the hypothesis that cement lines exhibit different mineral particle size, orientation and crystallographic parameters w.r.t. surrounding bone. We assume that such difference, reflected into different biomechanical properties, provides cement lines with the ability to hamper crack propagation. Our findings shall clarify the contribution of cement lines to bone toughness and guide the design of bone-inspired composites, with a tunable fiber/matrix interface to enhance toughness.