Study of the internal structure of the infantile zygomatic bone.

External measurements of the zygomatic bone have been reported, but there are no reports on the internal structure. We studied the internal structure of the zygomatic bone and determined the changes in cortical bone width, cortical bone ratio to total cross-sectional area, and trabecular bone width through six periods of tooth growth and development. Zygomatic bone were fixed in resin and sliced, then the cross-sectional specimens were photographed with soft X-rays. The images were analyzed with an image processor. The specimens included the surrounding cortical bone and its internal spongy substance. The cortical bone width, cortical bone ratio, and trabecular bone width increased significantly from the period of deciduous dentition to the first early period of mixed dentition, but leveled off after that. This indicates that in addition to the growth and development of the zygomatic bone itself, its structure is also affected by the forces generated in the maxilla by mastication.