F. MÜLLER*, M.R. HEATH1, G. DAVIS2 (Dept. of Prosthetic Dentistry, University of Mainz, FRG; The London Hospital Medical College, Dept. of 1Prosthetic Dentistry and 2Child Dental Health, London, U.K.)
Suction is achieved when dentures are first fitted but progressively diminishes during the wearing period. The aim of this study was to investigate the extent to what mastication relies on suction once complete dentures are adapted. Therefore seven edentulous patients with an average age of 74.0 ± 6.3 years took part in the experiment. All had worn their dentures for 8.5 ± 1.1 months and were subjectively satisfied with them. Upper copy dentures with a good fit and peripheral seal were made incorporating a fine tube between the fit surface and an air pressure pump and a manometer. Mandibular movements, EMG and the pressure under the upper denture were recorded whilst the subjects were chewing gum unilaterally. During the chewing sequence the upper dentures were unexpectedly loosened twice by injecting air under the fitting surface for an average of 25.6 ± 8.1 cycles.
All subjects continued chewing apparently undisturbed whilst the upper denture was loosened. The mandibular excursions were found almost unaltered during all phases of the chewing cycle but the movements' speed tended to be reduced when upper denture suction was not present. However, except for the occlusal phase, the variances of the duration of the individual cycle phases and the speed of movement were significantly smaller. The muscle activity showed significantly longer bursts and the peak occurred later in the cycle. The ratio of EMG-peak to burst integral dropped indicating a flatter shape of the burst but this was not significant.
Once adaptation to dentures was successful, the loss of suction did not interrupt ongoing mastication. Failure of denture retention initiates an immediate modification of muscular activity patterns.