Mandibular Movements in Hemi-mandibulectomy Patients during Injestion and Deglutition

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In mandibulectomy patients who have not undergone surgical reconstruction, the remaining mandibular segment is unstable and often deviated. Its movements have low reproducibility during mastication and deglutition.The purpose of this study was to clarify three-dimensionally the differences in mandibular movements for each of these oral functions in mandibulectomy patients with and without mandibular continuity. Four mandibulectomy subjects (Group I) without mandibular continuity and three subjects (Group II) with mandibular continuity were selected. Their mandibular movements were recorded using a jaw movement tracking device with six degrees of freedom. Each movement was assessed graphically at the virtual incisor point and the rotational angle of the mandible in the frontal, sagittal and horizontal plane was analyzed. Furthermore, in Group I subjects, 4 types of the platal ramps by changing of the width of the occlusal sufaces were applied and analyzed during each functional movement.The findings were as follows ;1. In Group I, the border movements at the virtual incisor point exhibited an irregular and asymmetric envelope deviated to the resected side in the frontal plane, whereas Group II exhibited a smooth and symmetric envelope.2. In Group I, the rotational angle in the frontal plane during border movements, mastication and in the frontal and horizontal plane during deglutition were significantly larger than in Group II.3. The wider the palatal ramps were, the more smooth and wider each chewing stroke was in the frontal plane, whereas the more frequently the mandibular movement was interfered during speech.A comparison among border and all functional movements in mandibulectomy patients revealed characteristic movements in the rotation of the mandible in the frontal plane. It is suggested that the rotational angle of the mandible is a useful parameter for assessment of mandibular movements in mandibulectomy patients.