Objectives: We have developed a simple and cheap jaw-tracking system using a home digital camcorder. However, the masticatory movements have not been measured yet. This study aims to confirm that the measurement of chewing movements using this system is sufficiently precise for clinical use to the same degree as a conventional jaw-tracking system. Methods: The new jaw-tracking system consists of a digital camcorder (DCR-TRV900, SONY), a mirror assembled beside the subject's face to detect antero-posterior movement, and motion capture software (2D-PTV, Digimo) operated by a personal computer. The marker for detecting jaw-movements was attached to mandibular incisors of a subject. Jaw movements including mirror images were recorded by the camcorder.The movements of the marker was traced and analyzed by the motion capture software,and transferred to 3-D data by our original logic. Five residents of our university hospital who have complete dentition were consented to be subjects. Their masticatory movements were simultaneously recorded by both the newly developed system and a conventional jaw-tracking system (Sirognathograph Analyzing System III, Canopus). To assess the precision of our system, simple regression analysis between the trajectories recorded by both systems were carried out for each measured coordinate (x; transverse direction, y; vertical direction, z; antero-posterior direction). Results: The trajectories of chewing movements recorded by both systems simultaneously were very similar. The correlation coefficient values between trajectories obtained from both systems were 0.9 or higher in every direction for all subjects. It was confirmed that the new jaw-tracking system we developed can record masticatory movements to the same degree as the conventional jaw-tracking system. Conclusion: The newly developed jaw-tracking system can measure chewing movements with high precision enough for clinical use.

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