Myogenous temporomandibular disorder patients and the temporomandibular opening index

Limited mandibular movement is one of the cardinal signs of temporomandibul ar disorders, and is usually assessed by measurement of mouth opening. Line ar measurement of mouth opening does not discriminate between diagnostic gr oups and has been shown to be influenced by gender, age and ramus length. A new temporomandibular opening index, however, can differentiate between di agnostic groups and is not influenced by the above variables. When patients with a myogenous temporomandibular disorder were examined, the temporomand ibular opening index distinguished two subgroups, the first with values abo ut the lower quartile and the second with values about the upper quartile. A similar identification of two subgroups was seen in electromyographic stu dies of myogenous temporomandibular disorder patients (Visser, A., Kroon, G .W., Naeije, M. & Hansson, T.L. (1995) Journal of Oral Rehabilitation, 22, 429).