Title: 0629 - The Role of Myofibroblasts in Relapse Following Palatal Expansion


Susan Bae, University of California - Los Angeles
Juwan Rice (Presenter)
University of California - Los Angeles

Reuben Kim, University of California - Los Angeles
Christine Hong, University of California - Los Angeles


Objectives: Midpalatal expansion is used in orthodontics to address transverse maxillary deficiency; yet, current therapeutic modalities do not provide stability, as relapse can occur in up to 45% of orthodontic patients and 80% of craniofacial patients. The cause of post-expansion relapse is multifactorial and the soft tissue is believed to play a critical role. Prior research showed that bisphosphonates (BPs) reduced the relapse ratio following expansion. The long-term goal of this study was to elucidate the role of soft tissue in post-expansion relapse for development of improved therapeutics for palatal expansion. Therefore, we hypothesized that BPs enhance post-expansion stability by modulating oral myofibroblastic differentiation.

Methods: Myofibroblasts were induced by TGF-β and its marker αSMA expression was evaluated by real-time PCR and Western blot. In vivo experiment involving 30 mice underwent 7 days of palatal expansion using an expander with a helical spring and arms that loop around the central incisors. Post- expansion, the control group was injected with physiologic saline solution (5mg/kg, 0.9% sodium chloride) and the experimental group (n=10) was injected with (0.1mg/kg of Zoledronate). The expanders were then converted to retention appliances and allowed 7 days of retention. After retention, half from each group were sacrificed. The other half was sacrificed after 7 days of relapse in which the retention device will be removed.

Results: Bisphosphonates inhibit gene and protein expression of αSMA mediated by TGF-β1. Micro-CT analysis of the decalcified maxilla showed a significant decrease in relapse in mice treated with bisphosphonate. Furthermore, there was a significant increase in percent bone volume and bone mineral density after relapse in mice treated with bisphosphonate. From H & E staining, clear histologic clear histologic differences were noted between the control and the bisphosphonate groups in the suture area.

Conclusions: These results suggest that BPs plays a role in reducing relapse mediated by myofibroblasts.

Student Presenter

This abstract is based on research that was funded entirely or partially by an outside source:
NIH/NIDCR 5K08DE024603

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE