Constrained and unconstrained postures of the mandible--a break with tradition?
Evaluation of detailed electrognathographic recordings of various movements of the mandible (and points on it) suggested interpretations at variance with some traditional concepts. Data previously accumulated from several sources were subjected to critical analysis. An objective was to assess the manner in which two rotations of the mandible influenced its postures during trials of mastication and deliberate lateral excursions. Rotations about a vertical and an antero-posterior axis appear to facilitate a greater functional posturing potential of the mandible than has previously been reported. In most instances the influence of the rotations upon mandibular posture is considerably greater than the size of the recorded angles would suggest. Some of the resulting postures seem to challenge concepts derived strictly from cadaverine anatomy. For example, during mastication the condyle does not simply glide forward and backward relative to the eminence but may be distracted downward away from it for a part of the time. Furthermore, the ability of a subject to effect a considerable variety of mandibular postures challenges traditional reliance upon constrained mandibular movements as a means of evaluating function.
Lewin
A
A
Department of Orthodontics, University of the Witwatersrand, Johannesburg, South Africa.
Evans
W G
WG
Booth
J L
JL
Howes
D G
DG
D006801:Humans; D007574:Jaw Relation Record; D008334:Mandible / Q000502:physiology*; D008409:Mastication / Q000502:physiology; D009068:Movement; D012399:Rotation