Pathophysiology of TMD and other related disorders

Abstract

The tooth pulp has many attractive features for the study of peripheral pain mechanisms because of its rich innervation, its unique distribution of nerve fibers and its general disposition to give rise to pain upon stimulation. An experimental model has been developed for simultaneous recordings of intradental multi-unit A-delta nerve activity and the subjective intensity and quality of pain evoked by tooth pulp stimulation in conscious, alert humans. The only teeth to be considered for this kind of investigations are those having such a periodontal condition that they have to be extracted. The nerve activity was recorded from two electrodes placed in the dentin on the labial tooth surface, one at the level of the most incisal part of the pulp, and the other as far apically as possible. Brief cold stimulation was produced by using evaporating ethyl chloride administered between the recording electrodes. The magnitude of perceived pain was estimated by means of an intermodal matching technique (finger span) in combination with verbal descriptors. Of three response criteria selected — average response amplitude, peak amplitude and area under the response curve (integral)—for describing the relationship between intradental nerve activity and sharp, shooting pain, the integral yielded the highest mean correlation coefficient.