• R Emshoff and S Bertram.
• Department of Oral and Maxillofacial Surgery, University of Innsbruck, Austria.
• J Prosthet Dent. 1998 Oct 1; 80 (4): 457-61.

Statement Of ProblemPatients with temporomandibular disorders may have a cluster of joint and muscle disorders characterized primarily by pain, joint sounds, and irregular or deviating jaw function.PurposeThis study evaluated changes in local cross-sectional dimensions of muscles of the head and neck associated with short-term application of "splint therapy" using the diagnostic approach of high resolution gray-scale ultrasonography.Material And MethodsThe study included 15 subjects with signs and symptoms of temporomandibular disorders, 10 in the internal derangement type (IDT) III-a group, and 5 in the myalgia type I (MT I) and myalgia type II (MT II) group. Ultrasonographic investigation was performed with a linear (B-scan) 7.5 MHz small-part transducer to visualize the anterior temporalis, anterior and deep masseter, anterior and posterior digastric, and sternocleidomastoid muscles. The absolute asymmetry index was used to assess local muscle asymmetry patterns and to evaluate the respective effect of occluding splints, with the mean maximum muscle diameter of the respective right and left sides calculated from 3 consecutive measurements before and after splint therapy.ResultsA comparison of pretreatment with 2-month follow-up values revealed a slight decrease in the overall mean local cross-sectional dimensions in the internal derangement type III-a group (0.3 mm) and a moderate decrease in the myalgia type I/II group (3.3 mm). With an overall mean pretreatment absolute asymmetry index of 1.3% for the internal derangement type III-a group and 0.5% for the myalgia type I/II groups, the 2-month follow-up showed the internal derangement type III-a group to be associated with a moderate (1.2%) and the myalgia type I/II groups with a slight (0.1%) decrease in the respective overall mean pretreatment absolute asymmetry indices.ConclusionThis study suggests that stabilization-type splints are effective in the reduction of local muscle thicknesses and asymmetries. Further studies are necessary to evaluate muscle-site specific effects in patient and nonpatient groups and to relate these effects to variables such as bite force, preferred chewing side, facial structure, and occlusion.

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