Characteristics of mandibular masticatory movement in young and elderly dentate subjects.

Dimensions and velocity of mandibular movement are important variables in the evaluation of masticatory and speech patterns. However, little information is available concerning elderly dentates and their oral motor function and behavior. Double recordings of a chewing period, from start to swallowing, were performed in 14 elderly (mean age, 80 years) and 30 young (mean age, 26 years) dentate subjects chewing crispbread. Three-dimensional records of mandibular movements were obtained by means of the Selspot movement analysis system, which monitors infrared light pulses from light-emitting diodes attached to the test subject. There was no difference in the duration of the total chewing cycle between the two groups. Mandibular velocity was significantly lower in the elderly group, in both the opening and the closing phases. Despite great inter-individual variations, significantly smaller mean vertical displacements of the mandible were found in the elderly than in the younger group. The lateral component in the vertical opening movement was similar for both the elderly and younger subjects. The similar chewing rates in the two groups might imply that the function of the central pattern generator was unaffected by old age. Aging was, however, associated with reduction of vertical mandibular displacement and velocity.