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Five-year reproducibility of natural head posture: a longitudinal study
1Department of Children's Dentistry and Orthodontics, Faculty of Dentistry, Prince Philip Dental Hospital, University of Hong Kong.
Summary
Natural head posture (NHP) shows decreasing reproducibility over five years in children, though it stabilizes and remains more consistent than other reference planes. Further research is needed to confirm long-term stability.
Area of Science:
- Orthodontics and Craniofacial Research
- Cephalometric Analysis
- Longitudinal Growth Studies
Background:
- Natural head posture (NHP) is increasingly utilized as a reference for craniofacial morphology evaluation.
- NHP's presumed lower long-term clinical variability compared to conventional intracranial planes is key to its use.
Purpose of the Study:
- To assess the longitudinal reproducibility of NHP in lateral cephalometric radiographs over a 5-year period.
- To evaluate the method error and individual variability in NHP measurements over time.
Main Methods:
- A 5-year longitudinal study involving 126 randomly selected Chinese children (initial age 12 years).
- 30 subjects were re-assessed after 5 years using lateral cephalometric radiographs.
- Method error and standard deviation of SN/vertical angulation were calculated at different time intervals.
Main Results:
- NHP reproducibility demonstrated deterioration over time, with stabilization observed after 1 to 1.5 years.
- Method error increased from 1.93° (1-2 hours) to 3.04° (5 years).
- Individual variability (SN/vertical angulation SD) increased from 2.61° to 4.20° over 5 years, yet NHP variance remained significantly lower than intracranial planes.
Conclusions:
- While NHP reproducibility decreases over 5 years, it stabilizes and remains a more reliable reference than conventional planes.
- Further longitudinal data are necessary to confirm if NHP reproducibility continues to decline beyond 5 years.