Linear and angular measurements of the mandible during maximal mouth opening.

PURPOSE

There are numerous reports of the translatory movement of the condyle in maximal mouth opening; however, the rotatory movement is less well understood. The purpose of this study was to investigate the rotatory condylar movement and the factors associated with it in normal subjects.

PATIENTS AND METHODS

To study the role of facial morphology in maximal mouth opening, linear and angular measurements of the mandible in both the closed and maximal open positions were made by means of cephalometry. Dental students, 29 men and 31 women with no functional disorders of the masticatory system, were investigated.

RESULTS

When the mouth was fully opened, the linear measurement of condylar movement was 20.5 +/- 4.0 mm in men and 18.1 +/- 2.5 mm in women, and the angular measurements of the rotation of the mandibular ramus were 39.1 +/- 5.9 degrees in men and 36.3 +/- 4.3 degrees in women. These differences were statistically significant (P < .01).

CONCLUSIONS

During condylar movement and rotation of the mandible, mandibular length and the inclination of the mandibular ramus in the former, and the inclination of the mandibular ramus, the mandibular angle and the position of the condyle in the latter, were important factors.