Disclusion time measurement studies: a comparison of disclusion time between chronic myofascial pain dysfunction...

From a pool of 89 patients, 49 patients were classified as having chronic myofascial pain dysfunction syndrome (MPDS), and 40 were classified as asymptomatic or non-MPDS patients designated as the control group for the study. To achieve balanced sample size in both groups, 40 patients were arbitrarily selected from the MPDS group. All patients from each of the two primary groups were then categorized and assigned to one or more subgroups according to the following criteria: (1) jaw classification, (2) open occlusion, (3) previous orthodontic therapy, or (4) no previous orthodontic therapy. A fifth subgroup composed of only MPDS patients and equally divided into those who had or had not experienced orthodontic therapy was established to determine whether mean disclusion time differences occur between orthodontic and nonorthodontic MPDS patients. All 80 patients were evaluated for disclusion time of their right and left mandibular excursions to determine statistical population comparisons. Statistical assessment of right and left disclusion times for women and men in the MPDS and non-MPDS groups was performed separately for each of the five subgroups. Analysis of the comparisons revealed that in all except two of the subgroups, mean disclusion time was significantly longer in the MPDS patient group than in the non-MPDS group. The two subgroups in which this was not apparent were those with open occlusion and orthodontic patients compared with nonorthodontic patients. These findings suggest that lengthy posterior disclusion time may be of diagnostic importance when the differing etiologic factors of chronic MPDS patients are evaluated.