Comparison of condylar lateral translation and skeletal classes

Aim: To demonstrate whether a correlation exists between the occurrence of mandibular lateral translation during the symmetric movements (ΔY-MLT) in mandibular dynamics and the different skeletal classes in humans. The main goal was to evaluate whether a correlation exists between the occurrence of mandibular lateral translation (ΔY-MLT) in protrusion/retrusion (P/R) and open/close (O/C) movements at different levels of severity and the subjects' skeletal classes. The secondary goal was to test the concordance between the maximum ΔY-MLT values in reference to four different cutoffs (0.65, 0.70, 0.75 and 0.80 mm). Materials and methods: A total of 108 subjects - 216 temporomandibular joints (TMJs) - who underwent a condyl-ography performed to obtain a functional diagnosis before dental rehabilitation were retrospectively selected by our research group to detect the occurrence of ΔY-MLT during symmetric movements. The condylographic tracings were analyzed in both sides (216 TMJs): two for P/R and two for O/C. The maximum ΔY-MLT value occurring in one side was taken out of both tracings. The cephalometric tracing executed to define the individual sagittal intermaxillary skeletal relationship was retrospectively retrieved and also included in the study. To test the correlation among the risk of presenting a pathological level of ΔY-MLT in both P/R and O/C movements, a chi-square test was performed for each skeletal class, using the abovementioned cutoffs. Conclusions: The repeated measures carried out for each patient were highly correlated, confirming the accuracy of the electronic-assisted condylography. Patients belonging to different skeletal classes did not show statistical differences in terms of ΔY-MLT average value in P/R and O/C. However, the multivariate analysis highlighted that skeletal class II showed a higher risk of presenting a pathological value in O/C compared to the risk for skeletal class I. During P/R movements, a higher level of risk exists for subjects belonging to skeletal class I. Moreover, this latter subgroup showed a high probability of presenting a pathological or borderline level in both types of symmetric movements at any cutoff, while the skeletal class II subjects have a major probability of presenting this complex pathological/altered profile only in the case of the larger width of lateral translation (0.8 mm). Keywords: temporomandibular disorders, temporomandibular joint dysfunction, internal derangement, computerized jaw tracking, skeletal classes