Studies of the Growth of the Upper Facial Skeleton Using Radioactive Calcium

¹ Department of Anatomy, College of Medicine, State University of Iowa, Iowa City

Thirty-five growing rats (birth to 62 days) were injected intraperitoneally with radioactive calcium (Ca⁴⁵) and killed at variable intervals after injection, ranging from 30 minutes to 77 days. Several pregnant rats were injected, to study the uptake of Ca⁴⁵ by fetal tissues.

Serial contact autoradiographs, prepared from the dried skulls in various planes, show that accurate localization of the isotope occurs within 30 minutes of injection, permitting accurate identification of individual bony elements of the base of the skull and face. Likewise, radioactive material was taken up rapidly by fetal bones and dental tissues following placental transfer.

In the upper jaw, areas of heavy periosteal deposition of Ca⁴⁵ on facial aspects are clearly defined from areas of relative inactivity on medial surfaces. The importance of the cartilages of the cranial base and nasal septum in increase in length of the skull and face is evidenced by the greater accumulation of Ca⁴⁵ which occurs in these zones. Around the roots of the cheek teeth the pattern of Ca⁴⁵ uptake suggests that these teeth migrate in an outward direction as the jaws increase in width.

It is concluded that Ca⁴⁵ provides a useful addition to the methods available for studies of facial growth. Autoradiographic results are fully complementary with and substantiate those obtained by other techniques.