Suture cartilage formation pattern varies with different expansive forces

Introduction: Midpalatal suture expansion could induce osteogenesis to correct maxillary insufficiency; cartilage formation could also be induced, and lower-magnitude forces might generate a preferable response pattern. In this study, we aimed for an enhanced understanding of the cartilage formatting effects of expansion. Methods: Thirty 6-week-old male C57BL/6 mice were randomly and evenly assigned to 3 groups; the animals in each group received a sustained suture expansion at 0, 10, and 20 g, respectively. Ten additional mice were fed the same as the baseline controls and received no expansion. After 7 days, the animals were killed; coronal paraffin sections were stained using toluidine blue and safranin-O. The proliferating cell nucleus antigen, the nuclear antigen Ki-67, alkaline phosphatase, and matrix metalloproteinase 13 expressions were visualized with immunohistochemistry. All data were analyzed statistically, and the differences were considered significant at P < 0.05. Results: Compared with the control, the cartilage matrix volume was significantly increased by the 20-g expansion, showing increased cartilage matrix and hypertrophic chondrocytes with the highest matrix metalloproteinase 13 expression. The 10-g expansion formed condensed proliferating chondrocyte masses, within which the highest percentages of proliferating cell nucleus antigen and Ki-67 positive cells were present. The 10-g and the 20-g expansions equally intensified the alkaline phosphatase expression. Conclusions: The lower expansion (10 g) promoted chondrocyte proliferation and induced a more preferable suture cartilage response pattern compared with the higher expansion (20 g), which just increased the cartilage matrix production.