Glenoid fossa responses to mandibular lateral shift in growing rats

Objective: To evaluate the morphological and histological responses of the glenoid fossa to mandibular lateral shift in growing rats. Materials and Methods: A resin plate was placed on the upper incisors of 4-week-old rats in the experimental groups to displace the mandible to the left during closure. The rats were killed after 2, 4, 8, and 12 weeks. The morphometric measurements were performed on dry skulls, and tissue blocks Were processed for periodic acid and Schiff's reagent (PAS) staining to examine the new bone formation. Results: Gross measurements showed asymmetry in both the position and size of the fossae between the two sides after 4 weeks of lateral shift. The glenoid fossa on the ipsilateral side was repositioned relatively backward, outward and upward compared with the contralateral side and control group, whereas the fossa on the contralateral side was relocated relatively forward and downward compared with the control group. The length of the fossa was smaller on the ipsilateral side than on contralateral side and control group. At 2 weeks, the amount of newly formed bone in the posterior region of the fossa was higher in the experimental group than the control group. Conclusion: It is suggested that the mandibular lateral shift causes asymmetry in the position and size of the glenoid fossa and that this phenomenon can be related to different bilateral directional new bone formation in the posterior region.