Mandibular movements are produced by a combination of condylar translation and rotation. The relationship between condylar translation and rotation during opening jaw movement and border movement was studied in 10 controls (4 men and 6 women), aged 20 to 26, without signs or symptoms of masticatory disorders and 61 patients (5 men and 56 women), aged 19 to 64 (average age 37.5), with closed lock of the temporomandibular joint (TMJ). The patterns of condylar movement and clinical findings were evaluated by means of multivariate analysis. Mandibular movements were recorded with an electronic jaw tracking system (JKN-1) consisting of 5000-pixel linear charge-coupled-device (CCD) cameras that register the position of six light-emitting diodes (LEDs) muted on two facebows separately attached to the upper and lower jaws. A computer produced plots of the opening angle versus the anterior condylar translation as well as the condylar path in the sagittal plane.
The condylar translation/rotation patterns were analyzed visually for differences in trace patterns. The patterns on visual analysis could by classified into six types. Type I: At the begining and at the end of opening, rotation was more pronounced than translation. Type II: At the end of opening, translation was more pronounced than rotation. Type III: At the begining of opening, rotation was more pronouced than translation. Type IV: The condylar translation/rotation patterns were almost linear. Type V: At the end of opening, rotation was pronounced and translation was severely limited. Type VI: At opening, rotation was pronounced and translation was completely limited. These patterns in the patients with closed lock of the TMJ differed from those in the controls. Of the controls, 50% were found to be type I, and 30% were type II. In contrast, 44% of the patients with closed lock were found to be Type V, and 33% were Type VI.
As for opening movement of patients with closed lock of the TMJ, abnomalities of condylar movement were more pronounced than those of movements at the incisive point. The results indicate that it is possible to diagnose the condition of closed lock disease. Moreover, our statistical evidence shows that it is possible to predict the patterns of condylar movement depending on age, degree of pain at opening, and deformity of the condyle.
