Abstract
Linear and angular measurements of the head and neck in both the closed and maximal opening positions were taken by means of cephalometry in dental students of our school. The subjects consisted of 29 males and 31 females, without functional disorders of the masticatory system. Skeletal forms of the head and neck related to the degree of maximal opening were also investigated. The results were as follows:
1. In closed position, the position of the mandible relative to the SN plane was rotated significantly more posteriorly in females than in males.
2. The angular rotation of the mandibular ramus when the mouth was fully opened was 39.1±5.9° in males and 36.3±4.3° in females. This difference was significant (P<0.01).
3. At maximal opening, the posterior margin of the mandibular ramus came to lie near the anterior margin of the cervical spine, in nearly all subjects.
4. The correlation between the degree of the mandibular rotation and the movement of the condyle was significant (r=0.660815, P<0.01).
5. The mandibular ramus angle (SN-CGo) was correlated with the degree of movement of the condyle (r=-0.356754, P<0.01) and the rotation of the mandible (r=-0.371501, P<0.01). This implied that a decrease in the mandibular ramus angle led to an increase in maximal opening.
