Figure 2.

Loss of periostin results in dramatic periodontal defects. A) Within the periodontal attachment apparatus, periostin localizes exclusively within the PDL as shown here by immunostaining (brown color). B) With normal periostin expression, as in the wild-type control mice, the periodontium can be described by a well-defined (a) gingival tissue, (b) cervical epithelial attachment, (c) intact crestal alveolar bone, (d) narrow and regular PDL thickness, and (e) appropriate thickness of root cementum. C) In the absence of periostin (periostin-null mice), several defects become evident after the tooth eruption. The null periodontium displays (a) enlarged gingival tissue, (b) attachment loss, (c) irregular PDL, (d) dramatic alveolar bone loss, and (e) external root resorption. D and E) The periodontium of the null and wild-type animals appears intact when the teeth are unerupted. F) The wild-type adults maintain an intact and functional periodontium. G) The adult null animal develops rapid alveolar bone loss and obvious enamel defects affecting the incisors. (Original magnification: A, ×20; B and C, ×4.)