The enkephalin response in human tooth pulp to orthodontic force.

Public perception is that dentistry and pain go hand in hand; thus, pain and pain control are important considerations to the profession. Recent studies have attempted to discover the precise metabolic events involved in neural transmission of nociceptive information. One focus has been the study of peptidergic pathways, which purportedly inhibit the firing of pain-conducting fibers. The research described in this article defined the existence of one enkephalin, methionine enkephalin (ME), in an extract of human tooth pulp tissue and the effect of orthodontic force on that ME concentration. One set of patients who had premolars extracted for orthodontic purposes served as controls. Another set, also diagnosed for premolar extractions, had a coil spring attached between the left and right maxillary premolars to supply an orthodontic force for a period of time prior to extraction. High-performance liquid chromatography, radioimmunoassay, radioreceptor assay, and mass spectrometry were used in a series of experiments to isolate, identify, and quantify ME in the pulp tissues. Principal results were as follows: for the first time ME was detected in human tooth pulp, orthodontic force caused a significant decrease in ME concentrations in the group of experimental teeth compared with controls, and ME levels of the first spring-attached tooth that was removed from each patient had a statistically significant inverse log-linear relationship to the amount of applied force. These data indicate that orthodontic force mobilizes at least one neuropeptidergic pathway in the human tooth pulp.