Age changes in the perception of comfortable mandibular occlusal positions.

It has been shown that a zone of comfort in maxillo-mandibular relationships in edentulous subjects can be identified with some precision. Whilst the neurophysiological mechanism involved has not been explained fully, the phenomenon is influenced by starting position and by fatigue. This experiment was set up to test the hypothesis that age is another significant factor in perception of the comfortable zone. A group of seventeen subjects with a mean age of 62 years and an equivalent younger group, the mean age of which was 28 years, were tested with Timmer screw jacks applied using the central approach to record the upper and lower limits of the zone fifteen times in succession for each subject. A linear statistical model was used to analyse the data from upper and lower borders separately. The results showed that the effect of making successive adjustments, whilst not significant statistically in the young group, was significant in the more elderly. Regression lines from the young group data were horizontal signifying the high degree of accuracy with which their perceptual mechanisms worked: the upwards inclination of those from the more elderly was interpreted as showing that initial appreciations were subjected to constant correction.