Abstract
BackgroundMastication is one of the most fundamental functions for the conservation of life. The demand for devices for evaluating stomatognathic function, for instance, recording mandibular movements or masticatory muscle activities using animal models, has been increasing in recent years to elucidate neuromuscular control mechanisms of mastication and to investigate the etiology of oral motor disorders. To identify the fundamental characteristics of the jaw movements of mice, we developed a new device that reconstructs the three-dimensional (3D) movement trajectories on an arbitrary point on the mandible during mastication.MethodsFirst, jaw movements with six degrees of freedom were measured using a motion capture system comprising two high-speed cameras and four reflective markers. Second, a 3D model of the mandible including the markers was created from micro-computed tomography images. Then, the jaw movement trajectory on the certain anatomical point was reproduced by integrating the kinematic data of the jaw movements with the geometric data of the mandible.ResultsThe 3D movements at any points on the mandible, such as the condyle, molar, and incisor during mastication, could be calculated and visualized with an accuracy > 0.041 mm in 3D space. The masticatory cycle was found to be clearly divided into three phases, namely, the opening, closing, and occlusal phases in mice.ConclusionsThe proposed system can reproduce and visualize the movements of internal anatomical points such as condylar points precisely by combining kinematic data with geometric data. The findings obtained from this system could facilitate our understanding of the pathogenesis of eating disorders or other oral motor disorders when we could compare the parameters of stomatognathic function of normal mice and those of genetically modified mice with oral behavioral dysfunctions.
Highlights
Mastication is one of the most fundamental functions for the conservation of life
Recent developments in molecular biology have led to the creation of genetically modified mice expressing various kinds of oral dysfunctions, such as serotonin receptor-deficient mice [11] that present with eating disorders and epilepsy
One was the kinematic data obtained from a motion capture system, and the other was the geometric data of the mandible created from images scanned with an in vivo micro-CT system (R-mCT, Rigaku, Japan)
Summary
The demand for devices for evaluating stomatognathic function, for instance, recording mandibular movements or masticatory muscle activities using animal models, has been increasing in recent years to elucidate neuromuscular control mechanisms of mastication and to investigate the etiology of oral motor disorders. To identify the fundamental characteristics of the jaw movements of mice, we developed a new device that reconstructs the three-dimensional (3D) movement trajectories on an arbitrary point on the mandible during mastication. Comparisons between normal mice and genetically modified mice with oral motor disorders will enhance our understanding of neural and motor disorders in the craniomandibular system Given this background, the demand for mice to use as animal models for identifying the etiology of oral motor disorders is increasing. There have been very few studies to evaluate oral functions in mice due to the difficulties in mounting the instrument on such small animals and in measuring a very small range of jaw movement within 2 mm cube
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