Osteogenesis of the human upper jaw: Proof of the non-existence of a separate premaxillary centre

Abstract

It is almost universally accepted that man possesses a premaxillary bone. Separate ossification centres have frequently been reported in alizarin embryo studies but seldom in studies which utilized serial sections. This study included 4 serially sectioned Rhesus monkey embryos and 128 human embryos; 93 were serially sectioned and 35 were cleared and alizarin stained. Separate premaxillary and maxillary ossification centres were easily identified in the monkey serial sections. The human serial sections, however, failed to reveal separate maxillary or premaxillary centres in a single embryo. They showed that a primary ossification line exists bilaterally in the upper jaw which lies just superior to the region which will give rise to the alveolar ridge. Ossification occurs in innumerable small independent foci of osteoid tissue along this line. These separate foci rapidly fuse and form a unit structure bilaterally before any calcification occurs. The alizarin stain (calcium specific) showed that calcification begins as different regions within this single osteoid framework, and in past investigations these have been incorrectly identified as “premaxillary” and “maxillary” ossification centres. The human jaw bone forms as a single bone bilaterally.