The effects of functional appliances on functional activities of jaw muscles in Macaca fasciculari

Functional orthodontic appliances are thought to modify skeletal jaw growth in an attempt to correct skeletal Class II and III malocclusions. Previous studies have raised the possibility that the activity of muscles of mastication increases the proliferation of condylar tissues and thus allow for jaw growth modification. The present study analyzed the functional EMG activity of four muscles of mastication (superior and inferior head of lateral pterygoid muscle, superficial masseter muscle and anterior portion of digastric muscle) in non-human primates. The EMG activity during deglutition and mastication before and after the insertion of two fixed functional appliances was recorded with chronically inserted electrodes to determine whether or not a continuously established bite registration produces a different EMG activity pattern from that produced by an intermittently established bit registration.;The wearing of the Herbst and protrusive appliances by Macaca fascicularis monkeys was associated with a statistically significant decrease in EMG activities of masticatory muscles. The insertion of the appliances resulted in a change in the temporal pattern of muscle activity associated with swallowing and mastication; the temporal pattern was re-established within 6 to 9-weeks. (Abstract shortened by UMI.).