FIG. 4.

Representative photomicrographs of ISO-10993-6 histological scoring parameters. (A–C) Osteogenic response and fibrosis scoring. (A) Animal SY05-left. Photomicrograph demonstrating an osteogenic response score of 2 (mild; 25–50% bone filling of implant/site) and a fibrosis score of 2 (mild), characterized by thin anastomosing trabeculae of new bone being laid down directly on a fibrous tissue intermediate that has permeated the implant. Dense fibrous connective tissue comprises the remaining implant associated new tissue. (B) Animal SY05-right. Photomicrograph demonstrating an osteogenic response score of 0 (none), and a fibrosis score of 3 (moderate). New host tissue growing into the implant is composed entirely of dense fibrosis (black asterisks), whereas the only visible bone is pre-existing tibial bone of the implant site. (C) Animal SY07-right. Photomicrograph demonstrating an osteogenic response score of 2 (mild; 25–50% bone filling of implant/site) and a fibrosis score of 1 (minimal). Abundant new bone composed of densely packed trabeculae (blue asterisks) infiltrates the implant material/void space left by the implant. The remaining space between the new bone is filled with increased amounts of adipose tissue, with only minimal fibrous tissue (black asterisk). (A–C) are 1.25 × magnification, scale bar = 1 mm. (D–F) Inflammation. (D) Animal SY05-left. Photomicrograph demonstrating a cumulative inflammation score 6. Multifocally, low to moderate numbers of lymphocytes (arrowhead) and multi-nucleate giant cells (arrows) infiltrate the fibrous tissue immediately surrounding the implant-associated void space. (E) Animal SY05-right. Photomicrograph demonstrating a cumulative inflammation score of 3/20. Inflammation is predominately composed of a few giant cells (arrows) infiltrating the fibrous tissue immediately adjacent to implant void spaces. (F) Animal SY07-right. Photomicrograph demonstrating a cumulative inflammation score of 2/20. Similar to SY05-right, inflammation in this animal was characterized primarily by few scattered giant cells (arrows) present throughout the fibrous tissue surrounding the implant/void space. Images (D–F) are 20 × magnification, scale bar = 50 μm. (G–I) Osteoblast activity and neovascularization. (G) Animal SY05-left. Photomicrograph demonstrating an osteoblast activity score of 2 and a neovascularization score of 1. A single layer of plump reactive osteoblasts (arrow) segmentally line endosteal surfaces of new bone. There is a minimal degree (∼1–2 vessels per 20 × magnification field) of new blood vessel formation (arrowheads). (H) Animal SY05-right. Photomicrograph demonstrating an osteoblast activity score of 0 and a neovascularization score of 2. No new bone and associated osteoblast activity was observed either extending from the margin of the tibial defect or being laid down directly within the implant. There is a mild degree (∼3–5 vessels per 20 × magnification field) of new blood vessel formation (black arrows) throughout the fibrous connective tissue surrounding the implant. (I) Animal SY07-right. Photomicrograph demonstrating an osteoblast activity score of 1 and a neovascularization score of 1. Osteoblast activity (arrow) was rarely observed along endosteal surfaces of new bone. Images (G–I) are 10 × magnification, scale bar = 100 μm.