The Sagittal Growth of the Lower Face During Foetal Life

Abstract

The mandibular line (ML) seems to show stability with both the anterior cranial base (NSI,) and with the Nasal Line (NL) during foetal lifr. The jaw angle, gn—go—co also shows angular stability during the same period. These findings suggest that the lower jaw follows the angular changes found in the cranial base, nasal septum and the upper jaw, the primary factor being possibly the cranial base. There is a reduction in the prognathic development of the lower jaw in the period investigated. Increased lower face prognathism seems to be associated with an anterior rotation of the lower jaw. Lower anterior facial height increases more than upper anterior facial height whereas horizontal growth of the lower face shows less increase than the anterior cranial base, nasal septum and upper jaw. Increased lower face height is followed by a long lower jaw, a large jaw angle and an increased distance between the condyle and NSL. Increase in the sm-NSP distance seems to be associated with a relative anterior position of the condyle, increased length of the mandibular body and inrreased height of the mandibular ramus.