Three-dimensional growth pattern of the rat mandible revealed by periodic live micro-computed tomography

Objective: We wanted to evaluate the three-dimensional (3D) mandibular growth of Sprague-Dawley rats from 4th to 16th postnatal weeks with periodic and live micro-computed tomographic scanning. Design: Twenty Sprague-Dawley rats were used for micro-CT scanning from 4th to 16th postnatal weeks. After 3D reconstruction of rat mandible, we performed the linear and angular measurements and the superimposition of the 3D models to evaluate the mandibular growth of rat. Results: The results showed that the growth direction of the condylar and coronoid regions was superior primarily and posterior secondarily, while the condyle had minimal lateral growth. Moreover, the angular region was growing mainly toward the posterior and lateral direction, while the body and symphysis maintained small, incremental anterior-posterior growth. Conclusions: We could evaluate the amount, rate, and direction of growth using the mandibular skeletal unit. Some reference points and measurements were more relevant in properly characterizing 3D growth of the mandible. Their growth rates were the greatest between 4th and 8th postnatal weeks, a period which seems most appropriate for studies of rat mandible growth.