Objective: Establishment of the natural head position in radiographs or photographs by estimation so called natural head orientation (NHO), has been a mater of discussion in forward or backward chin cases. This study aimed to determine the changes on reproducibility of NHO in cases with normal, forward and backward chin position.
Methods: Digital photographs based on NHP of 33 adults with normal profile were modified using computer software Supper-Goo and Photpshop technique to produce 99 profile images of three groups with normal, advanced and backward chin. The reconstructed images were presented to three observers who rotated the images through a circle hole on a computer monitor. The horizontal angle then were read on screen and recorded whenever they found the best horizontally oriented face. This was performed in four occasions; T0: baseline; T1: after 5 minutes; T2: after one week; and T3: one month after baseline.
Results: After orientation, the mean orientation angle was registered 0.19° ± 1.39, 0.20°± 1.53 and 0.31°± 1.39 for normal, forward and backward chin groups respectively. One-way ANOVA did not show any significant differences between three groups of chin position and among observers. The reproducibility of NHO calculated via Med-Calc 8.1 online software for the times T0, T1, T2 and T3, was obtained more than 60%, which is regarded significant in medical studies.
Conclusions: The natural head position could be created, with grate reliability, through orientation of profile images regardless of the chin position.
Keywords: Chin position, Natural Head Orientation, Reproducibility.