Electromyographic studies were performed on the actions of the muscles of the ltemporomandibular joints on twenty full denture wearers aged 46 to 60 years old.
Electromyograms were recorded with physiograph using the preamplifier. Electrodes which were the cup-typed gold discs, 9 millimeters in the diameter, was located on the anterior lobe of temporal muscle, and also on the superficial layer of the masseter muscle.
Paired electrodes were held by electrode cream so that they pressed on the skin surface at right angle, adhesive tape being used to anchor them.
The distance of a pair of electrodes was about 5 millimeters.
Experimental data were as follow:
1) In rest position of mandible;
The minimal electrical activity was noted.
2) In opening denture;
Some electrical activity was noted, but masseter muscle activity was stronger than temporal muscle.
3) In molar occlusion of mandible;
The electrical activity was the strongest among them, especially lnasster muscle.
4) In incisal bite of mandible;
The electrical activity of temporal muscle was strong.
5) In protrusion of mandible;
The electrical activity of masseter muscle was strong.
6) In retrusion of mandible;
The electrical activity of masseter muscle was strong.
7) In lateral excursion of mandible;
Masseter muscle activity of the working side was stronger than that of the balancing side.
8) In chewing movement;
The electrical activity of masseter muscle was strong.
In Summary:
1) Little difference was revealed in the electrical activity between full denture wearer and natural dentition in rest position of mandible.
2) In well fitting full denture wearer, electrical activity was lower than natural dentition but recovery of masticatory function was possible.
3) After delivery the full denture, electrical activity was constant independent on time going by.
4) Generally, activity ´of masseter muscle was stronger than temporal muscle.
5) On the side being temporomandibular joint trouble, the masseter muscle activity was compensated by temporal muscle.
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