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Condylar movement and mandibular rotation during jaw opening
S J Lindauer1, G Sabol, R J Isaacson
1Department of Orthodontics, School of Dentistry, Medical College of Virginia, Virginia Commonwealth University, Richmond, USA.
Summary
Mandibular rotation during jaw opening involves condylar translation and rotation, not a fixed axis. This dynamic movement, unique to each individual, impacts orthognathic surgery and appliance fabrication precision.
Area of Science:
- Dentistry
- Biomechanics
- Orthodontics
Background:
- Accurate mandibular rotation description is crucial for orthognathic surgery and appliance fabrication.
- Existing theories on condylar movement during jaw opening lack consensus.
Purpose of the Study:
- To examine condylar movements and centers of mandibular rotation during jaw opening in normal subjects.
- To clarify the nature of mandibular rotation for improved clinical applications.
Main Methods:
- Utilized the Dolphin Sonic Digitizing System to record condylar movements.
- Analyzed jaw opening kinematics in a cohort of normal subjects.
Main Results:
- All subjects exhibited both translation and rotation of the condyle at jaw opening initiation.
- No subject displayed a fixed center of rotation at the condylar head.
- Significant individual variability in the instantaneous center of rotation was observed.
Conclusions:
- Jaw opening involves a constantly moving, instantaneous center of rotation, unique to each individual.
- Variability in mandibular rotation necessitates consideration in surgical planning and appliance design.
- Findings challenge the notion of a fixed rotational axis in the temporomandibular joint.