The influence of the occlusal vertical dimension on masticatory muscle activities and hyoid bone position in complete denture wearers.

PURPOSE: Long lasting usage of complete dentures causes lower occlusal vertical dimension, producing potential detrimental consequences. The aim of this study was to investigate how changes in vertical dimension during denture exchange affect muscular activity and hyoid bone position. MATERIAL AND METHODS: Twenty-five edentulous, otherwise healthy patients (14 females, 11 males) aged 70.5 +/- 9 years, wearing their dentures over 5 years but no longer than 15 years (mean 9.8 +/- 5.2), were studied. New dentures were fabricated and the occlusal vertical dimension was recorded on cephalometric radiographs. Cephalograms were analyzed according to Ricketts. The relation of the hyoid bone position to the mandible was estimated. An evaluation of muscular activity was performed using the Biopak Electromyography Recording System synchronized with the T-Scan II Occlusal Analysis System. RESULTS: The occlusal vertical dimension was higher with the new dentures compared with the old dentures. The transition to new dentures was accompanied by a change of the vertical position of the hyoid bone. Digastric muscle activity was lower with the new dentures in comparison with the old dentures. CONCLUSIONS: Increase of the occlusal vertical dimension in complete denture wearers affects the hyoid bone position and masticatory muscle activity.

The effect of mastication on occlusal parameters in healthy volunteers.

PURPOSE: To assess possible associations between occlusal parameters and comminution of solid food during chewing in a group of completely dentate subjects. MATERIALS AND METHODS: Twenty-five completely dentate volunteers (28 teeth, 14 functional dental units) aged 24-50 yrs, without any complaints of the stomatognathic system participated in this study. An Optosil test was used to estimate masticatory efficiency for 20 and 80 cycles of chewing. An occlusal analysis, using the T-Scan II System, was performed to assess the following occlusal parameters: the distribution of occlusal contacts, the time of occlusion, the chewing platform area before chewing and after 20 and 80 cycles of chewing. RESULTS: The parameters, that were taken into account: i. X50 for 20 and 80 cycles of chewing, ii. the occlusion time, iii. the occlusal contact area. The occlusion time decreased after 20 and 80 chewing cycles (mean TO0=0.28+/-0.07 vs TO20=0.21+/-0.05 s vs TO80=0.18+/-0.05 s, respectively). The mean value of the chewing platform area was 125.12+/-46.5 mm2. CONCLUSION: Prolongation of chewing produces, shortening of the occlusion time while the chewing platform area remains at the same level independent of the number of chewing cycles.