Electromyographic analysis of the upper and lower fascicles of the orbicular oris muscle, in edentulous patients, before and after complete denture implantation.

The orbicular oris muscle, including its upper and lower fascicles, the alveolar processes and dental arches, constitute a complex morpho-functional system, located in the lower third of the face, which is very important for the clinical determination of the occlusal vertical dimension. Any alteration of this system, as in the case of edentulous patients, might produce esthetic problems and alterations in the muscular tonicity. This study was aimed to evaluate the electromyographic behaviour of that musculature in patients while pronouncing the syllables PAH, BAH, MAH, SAH, FAH, VAH, MEE, and the word MISSISSIPPI. Edentulous patients were submitted to electromyographic tests under two clinical conditions: before and after the implantation of complete dentures. A K6-I EMG Light Channel Surface Electromyograph was utilized (Myo-tronics Co. Seattle, WA, USA). The Analysis of Variance, with 3 sources of variation (Syllables, Muscles and Clinical Conditions) and 12 repetitions, indicated statistically significant differences in the pronunciation of the different syllables. For the Muscles factor, the analysis revealed higher electromyographic readings in the lower fascicle of the orbicular oris muscle, as compared with those of the upper fascicle. The comparison among the Clinical Conditions indicated higher electromyographic values for the edentulous condition (i.e., before complete denture implantation), as compared to those recorded after denture implantation.