An Electromyographic Analysis of Orbicularis Oris and Buccinator Muscle Activity in Patients with Complete Dentures Fabricated Using Two Neutral Zone Techniques—A Pilot Study

Abstract

Several studies have evaluated electromyographic (EMG) activity of perioral muscles in patients using unsatisfactory old complete dentures and after the insertion of new clinically acceptable dentures; however, studies evaluating EMG activity of orbicularis oris (OO) and buccinator (BUC) muscles in patients wearing complete dentures fabricated using swallowing (SNZ) and phonetic neutral zone (PNZ) techniques are lacking in the literature. The purpose of this study was to evaluate differences in muscle activity of the superior orbicularis oris (SOO), inferior orbicularis oris (IOO) and BUC muscle during the use of unsatisfactory old complete dentures, in comparison with the satisfactory dentures fabricated using the two neutral zone techniques. Ten completely edentulous participants dissatisfied with their existing mandibular complete dentures participated in the study. Each patient received two sets of new dentures fabricated using the SNZ and PNZ techniques. Surface EMG activity of the OO and BUC muscles was recorded using a 4-channel Medelec premier plus electromyography machine while the patients still used their old dentures (group A) and with the SNZ (group B) and PNZ (group C) dentures. On the basis of participation in the study, five participants first received the SNZ dentures and five the PNZ type. After having worn the prosthesis for a minimum of 2 months, EMG recordings were repeated for the first set of dentures. The prostheses were then changed and the procedures repeated. The activity of OO and BUC muscles was recorded at rest, while pursing and laughing, and during pronunciation of various syllables. Results are expressed as mean ± SD and as absolute numbers and percentage. ANOVA with appropriate correction (Bonferroni or Tamhane) and Student's t-test were used for statistical analysis. A p-value < 0.05 was taken to indicate a significant difference. There was no statistically significant difference in the mean EMG activity of SOO, IOO, and BUC muscles at rest, or during pursing or laughing among the three groups. No significant difference was observed in the mean EMG activity of SOO and BUC muscle among the groups for all the syllables pronounced. For IOO, a statistically significant difference was observed among the groups for the words "baby" and "cheese." Within-group comparisons of the mean EMG activities of SOO and IOO during pronunciation and pursing showed no significant difference; however, at rest a statistically significant difference was observed in group B. OO and BUC muscle activities did not significantly differ, irrespective of the technique used for fabrication of complete dentures.