Influence of placement position and designing of removable partial denture on oral sensation

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This study aimed to investigate the effects of different shapes of removable dentures on oral sensation, and to identify comfortable position and designing of major connectors.Four different cross sectional form and different placement position of experimental palatal straps were delivered to 6 healthy subjects and examined as for lingual tactile sensation with questionnaire. The results were that with the knife-edged marginal shape of cross sectional form and the symmetrical form at the occlusal view of major connector exihibited less uncomfortable lingual tactile sensation.When applying different thickness plates to 10 healthy dentulous subjects, with the thinner experimental metal plates, it showed more sensitive gustatory response than with the thicker metal or resin plates.Two types of new method to evaluate the ability of mastication were developed and were applied to the partial edentulous patients with dentures. One was the method to analyze bolus formation ability by counting the number of rice cracker chewing strokes. Another was to analyze the amount of umami in saliva solution by measuring the glutamine amino acid in mastication of tangle at the molar teeth.As to the pressure pain threshold(PPT) of edentulous oral mucosa, denture-wearing patients exhibited 40% lower value of PPT than non-denture-wearing patients.In guinea pig experiment the neuronal mechanism of adjusting occlusal vertical dimension was investigated by physiological method. And the trigeminal mesencephalic nucleus were proved to be involved in the regulation of the occlusal vertical dimension. Raising or reducing occlusal vertical dimension alters the length of jaw-closing muscles, resulting in changing the sensitivity of the muscle spindles.It was suggested that oral sensation and oral function are closely related with each other and consideration of oral sensation is necessary for the designing of removavle partial denture as much as retentive force and distribution of functional load.