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The hinge axis concept: a radiographic study of its relevance
G Hellsing1, E Hellsing, S Eliasson
1Department of Clinical Oral Physiology, Karolinska Institute, Huddinge, Sweden.
The Journal of Prosthetic Dentistry
|January 1, 1995
Summary
The hinge axis concept, crucial in dentistry, was tested. Mandibular movement showed minor condylar changes, suggesting limited clinical impact in prosthodontic restoration.
Area of Science:
- Dentistry
- Biomechanics
- Prosthodontics
Background:
- The hinge axis concept, fundamental since the 1920s, posits mandibular movement around a transverse horizontal axis through both condyles.
- This concept significantly influences global clinical dental practices, particularly in prosthodontics.
Purpose of the Study:
- To investigate the condylar positional changes during an increase in occlusal vertical dimension.
- To evaluate the validity of pure rotational movement around the hinge axis in a clinical context.
Main Methods:
- Utilized radiographic subtraction technique to analyze mandibular movement.
- Measured positional changes of the condyles in the retruded position after increasing occlusal vertical dimension by 4 to 7 mm.
Main Results:
- Observed small, unpredictable positional changes in the condyles, ranging from 0.31 to 1.84 mm.
- Demonstrated that pure rotation around the hinge axis did not occur.
- The condylar displacement was found to be of minor clinical significance.
Conclusions:
- The traditional hinge axis concept may not fully represent mandibular movement during vertical dimension changes.
- Condylar displacements observed are likely of minimal clinical relevance for prosthodontic restorations.
- Further research may refine understanding of complex mandibular kinematics in dental restoration.