Aging and mastication: changes in performance and in the swallowing threshold with natural dentition.

Few comprehensive studies of oral function have been conducted on adult populations. A "Longitudinal and Cross-Sectional Study of Oral Health in Healthy Veterans" was activated at the VA Outpatient Clinic in Boston in 1969; it included general oral and dental examinations as well as tests of masticatory performance and the swallowing threshold. The current investigation involved 863 subjects from the "Dental Study" who had either their natural teeth or a fixed replacement for missing teeth. Masticatory performance as measured by the subject's ability to reduce a test portion of cut carrot by a mandatory number of chewing stroked remained constant for persons with complete or partially compromised natural dentition. Swallowing threshold performance as measured by the particle size acceptable for swallowing remained constant for persons with complete dentition. Tooth loss significantly decreased the swallowing threshold performance and increased the particle size which the subject was willing to swallow. Older subjects increased the number of chewing strokes and the time required for this test, an observation not related to performance as measured by final particle size. Only with compromised dentition, however, did this increased effort result in increased performance.