Acute Effects on Masticatory Muscle Activity and Swallowing Following Increases in Occlusal Vertical Dimension Using Bite Blocks

Objective: This study aimed to evaluate acute changes in tongue pressure and electromyographic (EMG) activity of the masseter and temporalis muscles during swallowing with incremental increases in occlusal vertical dimension (OVD). Material and Methods: This pilot experimental study included 22 healthy adults. Swallowing was assessed at the basal OVD and with incremental increases of 2, 4, and 6 mm using hard wax stops under two conditions: saliva swallowing (SS) and yogurt swallowing (YS). Tongue pressure was measured with a Flexiforce A-201 sensor, and EMG activity of the masseter and temporalis muscles was recorded using EMG Works 4.0.7 (Delsys, USA). Each participant performed three swallows per condition, and the average of the three trials was used for analysis. Comparisons between conditions were made using ordinary least squares linear regression, with a significance level of p < 0.05 and 95% confidence intervals. Results: No significant differences in EMG activity were observed for the temporalis or masseter muscles across the different OVD conditions during SS (p > 0.05). Tongue pressure increased significantly between basal OVD and 4- and 6-mm OVDs during SS (p < 0.05) and between all OVDs during YS (p < 0.05). Conclusions: A short-term increase in OVD up to 6 mm was not associated with statistically significant acute changes in EMG activity and produced only minor adaptive variations in tongue pressure. These findings indicate that no immediate neuromuscular disturbances were detected under the experimental conditions tested; however, given the pilot design, no conclusions can be drawn regarding long-term safety or equivalence. Clinical Study Registration Number: CEC202030.