Prenatal development of the human osseous temporomandibular region

The purpose of the present study was to describe the sequence in which the lateral cranial base ossifies, particularly in the temporomandibular region. Charting the ossification sequence in the lateral normal cranial base is important for evaluating deviations in pre- and postnatal temporomandibular development. The material consisted of 74 normal human fetuses (crown-rump length = 25-228 mm). The period investigated covers the interval from the early start of ossification at 8 weeks gestational age to the occurrence of a complex ossification pattern at 21 weeks gestational age. Ossification of the cranial base in the sagittal plane is assessed mainly by radiography. The findings are confirmed by marking structures before X-ray, devisceration, and histology. This investigation confirms previous findings concerning regularity in cranial ossification sequences. In addition, the ossification in the temporomandibular region is divided into eight developmental stages according to the pattern of ossification. Thus, a developmental reference material has been established based on the following sequence in ossification of the cranial base (including the mandible and the zygomatic bone): mandible, maxilla, medial pterygoid process of the sphenoid bone, the horizontal part of the frontal bone, the zygomatic bone, the zygomatic arch of the temporal bone, the squamous part of the temporal bone and the occipital squama followed by ossification in the greater wing of the sphenoid bone, the tympanic ring, the occipital condyle, the minor wing of the sphenoid bone (anterior clinoid process), and the lateral part of the postsphenoid bone.(ABSTRACT TRUNCATED AT 250 WORDS)