Influence of Forward Head Posture on the Condylar Position

Objectives: Habitual forward head posture has been suggested to be one of the causes of temporomandibular disorders (TMDs). However, there were no experimental data showing the influence of habitual forward head posture on the condylar position with the mandible at rest. The purpose of this study was to examine this influence. Methods: Ten healthy young adults without TMD symptoms participated in this study. They gave their informed consent after having received an explanation of this study. Using a six-degrees-of-freedom jaw-tracking system, we recorded the mandibular position during two different head postures, i.e., the natural head posture and forward head posture, with the mandible at rest. The hinge axis point was mathematically calculated and was used as the condylar point. The mean displacement in each direction between the two different head postures was statistically analyzed. Results: In the transversal and vertical directions, there were no significant differences of the displacement at the condylar point between the natural head posture and forward head posture. In the anterior-posterior direction, the condylar positions in the forward head posture with the mandible at rest were significantly more posterior than those in the natural head posture. Conclusions: The results suggest that the condyles are displaced more posteriorly in the forward head posture than that in the natural head posture with the mandible at rest. The posterior displacement of condyles at rest in subjects with habitual forward head posture, may lead to TMDs via excessive load to the temporomandibular joint.