Mandibular condylar growth in growing rats after experimentally displaced condylar fracture with associated attachment damage and disc displacement: an observation by polychrome sequential labeling.

PURPOSE: The purpose of this study was to evaluate mandibular condylar growth in growing rats after experimentally displaced condylar fracture with associated attachment damage and disc displacement by means of polychrome sequential labeling.

MATERIALS AND

METHODS

We randomized 30 growing male Wistar rats into 3 equal groups: rats with experimentally displaced condylar fractures with associated attachment damage and disc displacement (experimental group); rats with experimentally displaced condylar fractures without associated attachment damage and disc displacement (control group); and rats that received no operative intervention (negative control group). Polychrome sequential labeling was used to establish chronologically oriented condylar growth characteristics in these rats. Three months after the operation, the specimens were obtained, fixed, dehydrated, and embedded in acrylic resin for fluorescence microscopy observation. In addition, the lateral-medial diameter (in millimeters) and mineral apposition rate (in micrometers per day) of condyles were measured and analyzed across the 3 groups.

RESULTS

The results showed condylar growth disturbance in the experimental group rats, presenting with no obvious and regular bone growth lines in the anamorphic condyle. However, in the control group and negative control group rats, the condylar growth was normal. Regarding the lateral-medial diameter and mineral apposition rate, there was a significant difference between the experimental group and control group, as well as between the experimental group and negative control group; however, there was no significant difference between the control group and negative control group.

CONCLUSIONS

The occurrence of associated attachment damage and disc displacement in condylar fractures should be considered an important factor influencing the condylar growth after fracture.