Correlated appearance of ossification and nerve tissue in human fetal jaws.

The factors initiating the onset of desmal jaw formation are not known. The purpose of the present report was to examine the correlation between the appearance of ossification and nerve tissue in human fetal jaws. This was done through elaboration of similarities in occurrence of tissue types at four different sites of initial bone formation in the jaws. Radiological and histochemical methods applied to the jaws of 26 human embryos/fetuses revealed that nerve tissue appeared in the jaws before bone tissue. Early bone formation occurred in close relation to the mandibular nerve, the maxillary nerve, the palatine nerve, and the naso-palatine nerve. It is suggested that the foramina (mental foramen, infraorbital foramen, palatal foramen, and incisive foramen) are the areas of incipient bone formation, and that the sequence in bone formation corresponds to the sequence in the development of nerve fibers from the trigeminal ganglion.