Figure 9. Reduction of secondary cartilage and increased osteoclast numbers in expansion suture.

Frontal sections of midpalatal sutures of control animals at day 3 (A and D) and expansion animals at days 3 (B and E), 7 (H, top) and 14 (C, F and H, bottom). Sections were subjected to Saffranin O/Fast Green staining (A–C) and stained for tartrate resistant acid phosphatase (TRAP) (D–F). (G) Comparative analysis of TRAP positive multinucleated cell numbers in control groups and expansion groups at days 1, 3, 7 and 14 (* p<0.05). B: filled arrowhead points to a region of significantly decreased Saffranin O-positive cartilage. C: open arrowheads point to areas of significantly reduced Saffranin O staining. E and F: arrows point to osteoclasts on the nasal side of the palatal bone surfaces (E) and on the surface of bone marrow cavities (F). H: positive staining with collagen II specific antibodies identifies regions of newly formed cartilage within the oral region of the suture (see also C). I: Diagrams showing midpalatal suture at the beginning (up) and end (below) of the 14-day period of suture expansion. Following exposure to expansion force (indicated by arrows and F under the diagram), the suture region is widened, new bone (red) is forming at the palatal edges in the nasal (top) region, and new bone (red) and cartilage (light green) are formed in the oral (bottom) region. Scale bar (A, D and H): 100μm.