Vertical dimension of occlusion related to mandibular movement during swallowing

Background: Increasing the vertical dimension of occlusion (VDO) is a common procedure in complicated prosthodontic treatment. The swallowing technique had been verified as a functional method to determine the VDO. The purpose of this study was to investigate the association between increasing VDO and mandibular movement during swallowing. Methods: 26 females and 14 males were enrolled (age range: 21 to 30 year-old). Under different increased VDO (3, 5, and 8 mm), the mandibular trajectory during swallowing was measured by K7 Evaluation System (Myotronics®). When the subjects were instructed to salivary swallowing, the range of mandibular movement in vertical, anteroposterior and lateral directions were recorded. Results: Increasing VDO significantly impacted the range of mandibular movement in lateral direction during swallowing (p < 0.0001, F value = 40.09). The average variance of the mandibular movement distance in lateral direction during swallowing raise 1.58 (p = 0.001); 3.59 (p = 0.0001) and 2.01 (p = 0.001) when th VDO was raised from 3 mm to 5 mm; from 3 mm to 8 mm and from 5 to 8 mm respectively. The range of mandibular movement was significantly correlated to the increasing VDO (p ≤ 0.05) under the analysis of the Post Hoc test. Conclusions: VDO was closely correlated to the trajectory of mandibular motion during swallowing. The increase in VDO could change the extent of mandibular trajectory during swallowing if the increase was more than 3 mm. The range of mandibular motion when swallowing had positive correlative tendency as the VDO was increased.