ANATOMIC DISORDERS OF THE TEMPOROMANDIBULAR-JOINT DISC IN ASYMPTOMATIC SUBJECTS

Purpose: This study determined the prevalence and specific anatomic ty pes of disc displacement in asymptomatic versus symptomatic subjects u sing magnetic resonance imaging (MRI). Patients and Methods: A detaile d MRI assessment was performed on both temporomandibular joints (TMJ) in 76 volunteers and 102 successive patients. Attention was placed on the functional aspects of disc displacement with and without reduction and on the anatomic aspects of disc displacement in the anterior, lat eral, medial, anterolateral, and anteromedial directions. These assess ments were made by radiologists blinded to the clinical information. R esults: Disc displacement was found in at least one joint in 25 of 76 (33%) of asymptomatic subjects and 79 of 102 (77%) of symptomatic subj ects, The anatomic types of disc displacement between groups was not s tatistically significant (P = .55), However, there was a significant d ifference between asymptomatic and symptomatic subjects, with an odds ratio of 3.91 for disc displacement with reduction and 42.71 for disc displacement without reduction (P < .001). Conclusion: Although there was a 33% prevalence of disc displacement in asymptomatic volunteers, there was a highly significant difference in the prevalence of interna l derangement in symptomatic subjects, Bruxing was statistically linke d to TMJ disc displacement and could explain the anatomic variation in abnormal disc position.