A Quantitative Analysis of the Decrease in Width of the Mandibular Arch during Forced Movements of the Mandible

The suggestion that the medial angulation of the external pterygoid muscles will effect a contracting action upon the two halves of the jaw was made by Grunewald in 1921.1 More recently, De Brul and Sicher2 demonstrated lines of stress near the symphysis of the mandible by squeezing the condyles together with finger pressure at the insertion of the external pterygoids.* They reported a distortion (in the living) between the last mandibular molars which was up to a mm. less when the jaw was forcefully protruded than when it was at rest. In an effort to characterize quantitatively the decrease in mandibular width from the rest position to a forced protrusive and a wideopen position the following study was undertaken.