Association between morphology of the first cervical vertebra, head posture, and craniofacial structures.

In order to test the assumption of an association between the anatomy of the first cervical vertebra, the atlas, and dentofacial build, roentgen-cephalograms of 78 young adults with either a markedly high or a low atlas dorsal arch were analysed with regard to head posture, and cervicovertebral and dentofacial anatomy. The high and low dorsal arch groups each comprised 22 women and 17 men. The head was more extended in the low arch groups and particularly so among the women, in whose low arch group there was a tendency for the cervical spine to be inclined more forward. Both the dorsal arch and the dens of the second vertebra were vertically smaller in the low arch groups, and more so among the men. Vertebral length was reduced more in the women, however. The clival plane was more parallel to the foraminal plane in the low arch groups and the gonial angle was more obtuse. Furthermore, the women with low arches showed a steepened mandibular plane, a backward-rotated condylar head, a decrease in the ratio of posterior to anterior face height, smaller vertical overbite and reduced proclination of the lower incisors. The prevalence of severe malocclusions was higher than in the corresponding high arch group.