Surgical procedure. A. Four standardized defects 8 mm in diameter were created using a trephine bur. B. The defects in each animal were assigned into four groups. Clockwise from bottom left: sham control, silk scaffold (SS), dental pulp cells seeded on SS (DPSS), periodontal ligament cells seeded on SS (PDLSS). C. The silk scaffold was made at 8 mm in diameter in order to fit into the defects.