Longitudinal study on TMJ disk status and its effect on mandibular growth

This longitudinal study assessed the potential contribution of temporomandibular joint (TMJ) disk status over mandibular linear and angular changes.

Cohort study.

Edmonton, Alberta, Canada.

Seventy-three adolescent subjects attending TMJ or orthodontic clinics with or without TMJ disk abnormality were followed during a mean 3 years 7 months. From this sample 39 subjects underwent orthodontic treatment.

Disk displacement and disk length measurements taken from MRIs were utilized to evaluate the TMJ disk status. Mandibular changes were quantified from cephalometric radiographs by superimposing the mandible around the internal cortex of the posterior wall of the mandibular symphysis. Fishman's skeletal maturation system was used to calculate the percentage of mandibular growth remaining during the follow-up. This expected mandibular growth was factored out through a statistical normalization process applied to the actual difference between the initial and final mandibular measurements. In addition, previous orthodontic treatment was also considered for the analysis. A multiple analysis of variance (MANOVA) was used to evaluate interaction between the independent variables (TMJ disk status and previous orthodontic treatment) over the dependent variables (mandibular ramus, mandibular body, mandibular length and gonial angle measurements).

No significant contribution was found of any of the evaluated variables or its interactions over the mandibular measurements.

No evidence was found of TMJ disk abnormality as an associated significant factor with mandibular dimensional changes. The findings have to be evaluated with caution because of some limitations identified in this study.