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

Abstract

Objective: To evaluate the growth pattern of the Sprague-Dawley (SD) rat mandible in three-dimensional (3D) without sacrifice of the animal for a limited time period.

Design: Twenty SD rats were used for microcomputed tomography (micro-CT) scan from T0 (4 week) to T3 (16 week) for every 4 weeks. We reviewed and selected the reference point for the 3D spatial measurements. After 3D reconstruction of micro-CT images, we performed linear and angular measurements and superimposition of the 3D micro-CT models to evaluate the mandibular growth of rat.

Results: Each site-specific growth rate was observed as follows. In functional cranial analysis, the longitudinal growth of angular process was the greatest, it increased 184% of the size of T0 period, compared to other measurement; condyle (170%), coronoid (157%), body (130%), symphysis (128%) respectively. The height of condyle increased 161%, and coronoid and anterior alveolar area showed 151–140% increase in height respectively. In anterior posterior length, condyle, coronoid, gonion from anterior alveolar bone showed similar increase of 143–138%. The width of angular process (Go-Go) increased 135%, however, width of condylar process (Con-Con) increased 110%. By the superimposition of the models, we could observe this growth pattern that the mandible grew radially, and the width of lower border of ramus was widen.

Conclusions: We analysed the growth pattern of mandible in SD rat visually through the image superimposition in three dimensions and calculated the growth ratio of each part of mandible according to the time periods.