15 - Acute changes in swallowing and electromyographic activity of the masticatory muscles while changing the occlusal vertical dimension with bite stops

Abstract

Introduction

Temporary bite-raising or bite-opening is often required in patients undergoing orthodontic treatment but the implications of increasing OVD remain a controversial issue based on existing evidence, although it is considered meaningful in rehabilitative procedures.

Objective

Determine the acute changes in tongue pressure and electromyographic (EMG) activity of the masseter and temporalis muscles during swallowing while increasing the occlusal vertical dimension (OVD).

Materials and Methods

Twenty-two participants were enrolled. Swallowing was measured at the basal OVD in two conditions: saliva swallowing (SS) and swallowing a semi-solid consistency element (yogurt swallowing, YS), regarding changes in tongue pressure and the EMG activity of the temporalis and masseter muscles. The same measurements were performed while increasing the OVD by 2, 4, and 6 mm. A tongue pressure sensor, Flexiforce A-201 model (Tekscan), was used to analyze the contact pressure of the tongue on the hard palate. Electromyography was recorded using EMG Works acquisition software. Comparisons between conditions were performed using ordinary least squares linear regression models. A significance level of P < 0.05 was applied, and 95% confidence intervals were calculated for all outcomes.

Results

The masseter and temporalis muscles showed no differences in EMG activity in SS condition with OVDs of 2, 4, and 6 mm (P > 0.05). In the YS condition, the masseter showed significant differences between basal OVD in the SS condition and all OVDs in the YS condition (P < 0.05), whereas the temporalis showed no differences. Tongue pressure showed differences in SS condition between OVDs at 0, 4, and 6 mm (P < 0.05). Significant results were observed between the SS and YS conditions at the same OVDs (P < 0.05).

Conclusion

The stomatognathic system rapidly adapts to acute changes in OVD.