Reproducibility of natural head position in normal Chinese people

• We recorded natural head position (NHP) with horizontal laser level and 3dMDface imaging system.
• NHP was studied in both the sagittal and coronal planes.
• Three ways to acquire NHP—self-balanced, mirror, and estimated positions—were compared.
• The estimated position has the best reproducibility.

IntroductionIn this study, we evaluated the reproducibility of natural head position for pitch and roll acquired using 3 methods.MethodsThe participants were 30 Chinese adults (ages, 23-28 years) who had normal occlusion with no history of orthodontic therapy, maxillofacial trauma, or surgery. The natural head position was acquired using the self-balanced, mirror, and estimated positions, which were performed in duplicate and repeated after 1 week. Three-dimensional photographs were recorded with a horizontal laser line projected onto the face. The laser lines were observed by registering the repeated 3-dimensional photographs. The roll and pitch of the head orientation were measured with a digital ruler. Reproducibility was calculated using Dahlberg's formula and the Bland–Altman method.ResultsThe reproducibility values calculated with Dahlberg's formula were 1.51°, 1.2°, and 0.99° for pitch, and 0.78°, 0.76°, and 0.41° for roll in the self-balanced, mirror, and estimated positions, respectively.ConclusionsThe 3 methods are reproducible for both pitch and roll, and the estimated position showed the best reproducibility among these methods. This indicates that the estimated position could be used for acquiring the reference plane in preoperative planning for orthognathic surgery.