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Estimated natural head position and facial morphology
1Research associate, Orthodontic Department, Dental School, University of Athens, Greece. dhal@dhal.com
Summary
Natural head orientation (NHO) is influenced by facial morphology, specifically chin position. This finding questions the validity of NHO as a diagnostic tool in orthodontics.
Area of Science:
- Orthodontics
- Cephalometrics
- Facial Morphology Analysis
Background:
- Natural head orientation (NHO) is a proposed reference for facial morphology assessment.
- NHO's subjective definition by orthodontists raises concerns about potential bias from facial form.
Purpose of the Study:
- To evaluate if natural head orientation (NHO) is influenced by variations in facial morphology.
- To determine the reliability of NHO as an objective diagnostic standard in orthodontics.
Main Methods:
- Lateral cephalometric photographs of 14 patients were digitally altered to simulate forward and backward chin positions (+/-2 degrees).
- Seven orthodontists oriented 42 images (original and altered) to NHO.
- Differences in head orientation measurements between chin positions were analyzed.
Main Results:
- Natural head orientation (NHO) was significantly influenced by chin position.
- Protrusive chins resulted in more downward head rotation (Frankfort plane 3.10 degrees) compared to retrusive chins (Frankfort plane 4.98 degrees).
- Head orientation changes were approximately half the magnitude of chin position alterations.
Conclusions:
- The validity of NHO as a diagnostic standard is questionable due to its dependence on facial morphology.
- Using NHO may lead to underestimation of true skeletal relationships in orthodontic assessments.