Temporomandibular disorders: the habitual chewing side syndrome

Abstract

Background:Temporomandibular disorders are the most common cause of chronic orofacial pain, but, except where theyoccur subsequent to trauma, their cause remains unknown. This cross-sectional study assessed chewing function (habitualchewing side) and the differences of the chewing side and condylar path and lateral anterior guidance angles in participantswith chronic unilateral temporomandibular disorder. This is the preliminary report of a randomized trial that aimed to testthe effect of a new occlusal adjustment therapy.Methods:The masticatory function of 21 randomly selected completely dentate participants with chronic temporoman-dibular disorders (all but one with unilateral symptoms) was assessed by observing them eat almonds, inspecting the lateralhorizontal movement of the jaw, with kinesiography, and by means of interview. The condylar path in the sagittal plane andthe lateral anterior guidance angles with respect to the Frankfort horizontal plane in the frontal plane were measured onboth sides in each individual.Results:Sixteen of 20 participants with unilateral symptoms chewed on the affected side; the concordance (Fisher’s exacttest, P = .003) and the concordance-symmetry level (Kappa coefficientk= 0.689; 95% confidence interval [CI], 0.38 to 0.99;P = .002) were significant. The mean condylar path angle was steeper (53.47(10.88) degrees versus 46.16(7.25) degrees;P = .001), and the mean lateral anterior guidance angle was flatter (41.63(13.35) degrees versus 48.32(9.53) degrees P = .036)on the symptomatic side.Discussion:The results of this study support the use of a new term based on etiology, ‘‘habitual chewing side syndrome’’,instead of the nonspecific symptom-based ‘‘temporomandibular joint disorders’’; this denomination is characterized inadults by a steeper condylar path, flatter lateral anterior guidance, and habitual chewing on the symptomatic side