Abstract
This paper developed a new method to easily record and automatically reproduce the 3D natural head position (NHP) of patients using a portable 3D scanner based on immediate calibration. We first optically scanned the patient’s face using a portable 3D scanner, and the scanned model was easily aligned with the global horizon based on an immediate calibration procedure using a developed calibration plate. The 3D patient NHP Computed Tomography(CT) model was reproduced automatically by performing registration between the CT model and the optically scanned model in the NHP using a modified coherent point drift (CPD) algorithm. In a phantom experiment, we evaluated the developed method’s accuracy using the error between the true and the calculated orientations in roll, pitch, and yaw directions. The mean difference was −0.05 ± 0.13°, 0.08 ± 0.22°, and −0.05 ± 0.18° in the roll, pitch, and yaw directions, respectively. The measured roll, pitch, and yaw directions were not significantly different from the true directions (p > 0.05). The calibration procedure for aligning the scanner coordinate system was easy enough for an inexperienced user to operate, and the 3D NHP CT model could be reproduced automatically. The developed method could be used for diagnosing and treating orthognathic patients with facial asymmetry accurately and conveniently in dental clinics.
Highlights
It is important to acquire the correct head position accurately to improve orthognathic surgery outcomes [1]
A mannequin phantom was used to evaluate the accuracy of the developed method for recording and reproducing the natural head position (NHP)
We evaluated the differences between true and calculated orientations in the roll, pitch, and yaw directions (Table 1)
Summary
It is important to acquire the correct head position accurately to improve orthognathic surgery outcomes [1]. To obtain the correct head position, the natural head position (NHP), in which the head is positioned upright with the eyes focused on a distant point at eye level, has been introduced [2,3]. Intracranial cephalometric landmarks were used as a logical reference for evaluating the orthodontic facial morphology in two-dimensional (2D) cephalometric analyses [4,5,6]. A three-dimensional (3D) NHP reproduction method has been introduced [7]. An important factor for diagnosing and treating orthognathic patients with severe facial asymmetry is the rotation of the patient’s 3D skull model to the NHP [1]. The 3D skull model cannot be rotated to the NHP
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