Judson C. Hickey

Electromyographic analysis of jaw movements

P REVIOUS ARTICLES have reported the frequency response requirements encountered in dental electromyography and have outlined a practical means of obtaining electromyograms of jaw muscle activity under optimal conditions. The influence and inadequacy of a single electrode reference on electromyograms was demonstrated and the necessity for using the multielectrode or standard generalized reference was established.l*2 The impetus of electromyography has reached beyond the determination of simple muscle function or dysfunction into the areas of orthodontics, periodontics, prosthodontics, and oral surgery. The electromyographer must be cognizant of the limitations of his instrumentation, and the dental profession likewise must realize the limit of its usefulness. The objectives of this study were (1) to determine the range of variability of muscular activity in jaw movements for a group of patients, (2) to determine the range of variability in a series of electromyograms of one patient, (3) to provide electromyographic data obtained with high-fidelity techniques for future reference, and (4) to provide an analysis of the role played by the external pterygoid muscles in trained (learned) jaw movements. In order to accomplish these objectives, statistical techniques were employed to analyze data derived from the electromyograms.

Electromyographic studies of mandibular muscles in basic jaw movements

Abstract The muscular activity for various jaw movements has been measured and the total electrical activity of the different muscles compared on a time basis. Based on observed electrical activity and anatomic considerations, it has been concluded that the external pterygoid and suprahyoid muscles were primarily responsible for the uncontrolled opening movement. The masseter and temporal muscles, of those listed, were responsible for the closing movement. The internal pterygoid muscles were not tested. The left external pterygoid muscle was mainly responsible for the movement of the mandible to the right and the right external pterygoid muscle for the opposite movement. Both external pterygoid muscles were responsible for the protrusion of the mandible. The analysis and discussion of the material covering the different sets of dentures will be presented at a later time.

Responsibility of the dentist in complete dentures

Abstract The dentist is obligated to perform certain essential phases of complete denture construction. These include making a comprehensive diagnosis, making certain that the oral tissues are healthy before work is started, making the impressions, producing jaw relation records, selecting the teeth, correcting the jaw relation records, rearranging the anterior teeth for esthetic appearance, correcting the occlusion at the time of the first insertion of the dentures, and making whatever denture adjustments may be necessary. If the dental profession is to maintain its high standard of denture service, the dentist must not delegate to someone else any phase of denture construction he should complete himself.

Stability of mandibular rest position

Abstract The stability of mandibular rest position was tested by two methods. A statistical analysis of the data indicated that there was no significant difference in mandibular rest position at the same sitting, between sittings approximately 1 year apart, or between the two methods. However, differences were of a magnitude to make the stability of rest position questionable for certain individuals. Similar measurements from both groups after the third year will add information as to the reliability of the methods tested and to the constancy of the position.

Influence of occlusal schemes on the muscular activity of edentulous patients

Abstract An investigation utilizing different occlusal schemes on the same denture base was conducted to test the variance in muscle activity during mastication. Results indicate that the anatomic occlusion required the least activity from the closing muscles for all test foods. The reverse curve occlusal scheme required the greatest closing muscle activity during the chewing of carrots and peanuts. Thus, the form of posterior occlusion is an important factor in the amount of muscle activity during mastication.