Fifty young and fifty elderly subjects were tested by a two-point discrimination method applying an aesthesiometer to the mucous membr'ane of lips, cheeks and tongue. Two changes characteristic of ageing wer'e disclosed: (1) higher threshold values wer'e found in the older age group eoneomitant with (2) a gr'eater range of variation in these values. The importance of the perception of tactile stimuli from the structures tested is discussed in relation to adaptation to full dentures. It is suggested that signals arising from lips, cheeks and tongue assist the process of adaptation, whereas signals from the dentur'e foundation ean, on occasion, pr'event adaptation.
IntroductionIt has been shown that three areas of facial skin innervated by the trigeminal nerve, when subjeeted to two-point discrimination tests exhibited a significant decrease in response in old people, compared to that in a group of young subjects (Brill et at., 1974). It was suggested that this decr'ease was due to the r'etrograde changes which occur thr'oughout the sensorium with ageing. Signs of involution in older subjeets have been found in receptors (Ronge, 1944), in intercalated nerve fibres (Cottrell, 1940), in spinal cell bodies (Gardner, 1940) and in the cerebr'al cor'tex (Brody, 1955). If the explanation offer'ed in r'elation to faeial skin is valid, at least in par't, then a similar decrease in sensibility should prevail when tactile stimuli ar'e applied to the oral mucosa. The pr'esent investigation was undertaken to test this hypothesis.A second objective was to discuss the assumption that perception of oral tactile stimuli has a bearing on the ability of patients to adapt to full dentur'es. The importance of this factor in relation to other's is still uncertain (Berr-y & Mahood, 1966).