Fig 4. Histology.

Undecalcified toluidine blue-stained sections of the (A, C, E, G) machined and (B, D, F, H) laser-modified implants. At the bone-implant interface, morphological features of bone formation and remodelling can be clearly observed in different threads in the cortical bone and the endosteal and bone marrow compartments. (A-B) Areas of ongoing remodelling. Osteoclasts (black arrows), osteoblasts (white arrows) and osteocytes (some of which are indicated by white arrowheads) are located in areas undergoing active remodelling at the interface. Blood vessels are indicated by black arrowheads. (C-D) For both implant types, mature bone occupies the endosteal threads, consisting of densely packed osteons (black arrows), with central blood vessels, surrounded by concentric bone lamellae and mature osteocytes. (E-F) Generally, the lower three threads of both implant types are occupied by bone marrow (Ma). Islands of newly formed, immature bone (black arrows) characterised by intense toluidine blue staining and large rounded osteocytes, which indicate an early stage of bone formation, are sometimes detected in the lower threads. This type of bone appears to be formed de novo and not as an extension from the endosteum. (G-H) Some of the bone marrow threads (Ma) show condensations of haematopoietic (black arrows) as well as relatively large and lightly stained mesenchymal-like cells (white arrows) adjacent to the implant surfaces.