11. Odontocetes possess teeth with cementum cells overlying dentine cells. 12. Cementum is a specialized bone like substance covering the root of a tooth.13. Periodontal ligaments connect the alveolar bone to the cementum . 14. There is also either a second infundibulum or a cementum -filled furrow. 15. Cementum also is permeable to a variety of materials.16. These cementoblasts can form subsequent layers of cementum if the tooth is injured. 17. This type of cementum forms around the fiber bundles of the periodontal ligaments. 18. ERM plays a role in cementum repair and regeneration. 19. Roots of teeth are covered with cementum , a structure that resembles bone. 20. Fibroblasts develop the periodontal ligaments which connect teeth to the alveolar bone through cementum .