Correlation between bite force and electromyographic activity in dentate and partially edentulous individuals

Dental absence interferes in the physiological functioning of the masticatory system, promoting occlusal and functional alterations. The purpose of this study was to verify maximal bite force and maximal bite force correlated with electromyographic activity in 14 partially edentulous and 14 dentate individuals. Bite force in right and left molar and incisor regions were registered using a dynamometer with capacity of up to 1000N, adapted for oral conditions and at the same time electromyography was performed using Myosystem-Br1 with electrodes positioned on right and left masseter and temporalis muscles, and one reference electrode on the frontal bone. The highest value out of three recordings was considered the individual's maximal bite force. Statistical analysis of the bite force data was performed by means of t-test and Pearson's bivariate correlation test was used for the analysis between bite and electromyographic activity using SPSS 12.0 software. Dentate individuals showed greater maximal bite force in the three regions. Correlations between electromyographic activity and bite force in the dentate group obtained positive coefficients for every muscle in the right molar region, for the left temporalis in the left molar region, and for every muscle in the incisive region. For the partially edentulous group, only the left temporalis muscle presented a positive correlation in the right molar region, there was positive correlation for the right masseter and right and left temporalis in the left molar region, and, in the incisive region, every muscle presented negative correlation. These data evidence the strong influence of dental loss over the maximal bite force and small correlation between bite force and electromyographic activity.

Electromyographic analysis of upper and lower fascicles of the orbicularis oris muscle in deaf individuals, in mandibular rest position, compared to hearers

This study had the aim to analyze electromyographically, the upper and lower fascicles of the orbicularis oris muscle in bilingual, oralist deaf individuals, comparing them with clinically healthy volunteers in mandibular rest position. This was performed in 50 patients of both sexes with an average age of 18.5 years, divided into 4 groups. 1. Ten deaf bilingual, nasal-breathing patients; 2. Ten deaf bilingual, buccal-breathing patients; 3. Ten deaf oralist, nasal-breathing patients; 4. Twenty healthy volunteers, nasal-breathing patients. An electromyograph K6-I EMG Light Channel Surface Electromyography (Myo-tronics Co. Seattle, WA, EUA) of eight channels was used. The electrodes applied were duotrodes, silver-chloride surface, disposable. Statistical analysis was performed using the SPSS software version 10.0 (Chicago, IL). Continuos data with normal distribution were analyzed by univariate analysis of variance (ANOVA). The level of significance was set at alpha= 0.01. Comparing the EMG activity of the orbicularis oris muscle made it possible to verify that, during clinical mandibular rest position, all four groups presented various levels of electromyographic (EMG) activity with statistically significant differences (F = 8.81, p < 0.01). Based this study's data, it was possible to conclude that the electromyography analysis of the orbicularis oris muscle in deaf individuals showed that deaf individuals presented higher levels of EMG activity of the orbicularis oris muscle than normal controls during mandibular rest position.

A clinical evaluation of materials for interocclusal registration in centric relation

Four techniques for interocclusal registrations of centric relation based on materials or combinations of materials usually utilized were tested by means of mounting of casts for a patient with partial lower edentulousness, without a free end saddle. To ensure the correct position of centric relation a Lucia jig was utilized. The following conditions for the record of posterior section were tested: registrations with wax, wax plus zinc oxide-eugenol paste, wax plus Duralay acrylic resin, and condensation silicone (putty). The evaluation was made by the measure of vertical distance between reference points in the base of the casts and calculation of variations occurring with each material. The combinations of wax plus zinc oxide-eugenol paste and wax plus Duralay acrylic resin showed the smallest variations in centric relation position.

Device for recording the path of insertion for removable partial dentures

Some negative outcomes of oral rehabilitation using removable partial dentures (RPDs) can be prevented when the framework of the RPD is planned with mounted diagnostic casts that have been analyzed in a dental surveyor. Recording the established path of insertion can be difficult when the procedure uses a pin that is cemented in the cast base, and the casts are mounted in an articulator. This article presents a procedure for a pin device to record the path of insertion of RPDs. This device serves the same purpose as the cemented pin but can be easily removed and replaced.