In rehabilitation for dysphagia in the elderly, it is necessary to take into account both age-related changes and reduced reserve capacity for swallowing. Especially, since it was thought that the oropharyngeal expansion as morphological age-related change causes functional changes such as pharyngeal residue. Wearing complete dentures is common in elderly people, and although wearing and removing dentures is thought to affect the morphology of the oropharynx, the details of this effect remain unclear.
The present study aimed to elucidate the relationship between wearing dentures and changes in the hyoid bone position and pharyngeal diameter. The subjects were 17 elderly people fitted with complete dentures who underwent cone-beam computed tomography imaging while wearing maxillary and mandibular dentures (MM), maxillary denture only (OM), and with neither maxillary nor mandibular dentures (ED). Computed tomography images were subjected to analysis of mandibular position (FMA), hyoid bone position, and antero-posterior and left-right oropharyngeal diameters.
FMA decreased significantly in the order MM, OM, ED. In the ED condition, the hyoid bone shifted significantly in the antero-superior direction as compared with the MM and OM conditions. Antero-posterior and left-right oropharyngeal diameters in the ED condition were significantly larger than those in the MM condition at the height of the base of the epiglottis. Removal of complete dentures causes an antero-superior shift of the mandible, resulting in an anterior and superior shift of the hyoid bone and the expansion of the inferior part of the oropharynx. These findings suggest that removal of dentures exacerbate reduced reserve capacity for swallowing by age-related changes in the elderly.

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