Architecture and Mineralization of Developing Mandibular Bone

Objectives: Ossification of the presumptive trabecular bone in the mandibular condyle and presumptive cortical bone in the mandibular corpus of the pig mandible was investigated during development using micro-computed tomography (microCT). Methods: Both three-dimensional architecture and mineralization characteristics were assessed from ten pigs of different developmental ages. Results: In the condyle, increases in trabecular thickness and separation and a decrease in trabecular number led to an unchanged bone volume fraction. A conversion from rod-like into plate-like trabeculae was observed. Bone volume and trabecular thickness were always higher in the corpus, where an increase in bone volume fraction was caused by an increase in trabecular thickness and a decrease in separation. A transition from a plate-like structure into a more compact structure took place. Onset of functional muscle behavior was reflected in bone parameters. Average degree of mineralization in condyle and corpus increased with age. In the corpus the degrees of mineralization were higher than in the condyle. The differences between condyle and corpus and changes with age could be explained by differences in distribution of mineralization within trabecular elements. Generally, degrees of mineralization increased from the surface towards the centers of trabecular elements, indicating growth of trabecular elements by surface apposition of new mineral. Conclusions: These findings suggest that, during normal mandibular development, changes in both architecture and local and global mineralization of the bone occur and that these changes might reflect the onset of mechanical loading of the TMJ in utero.