The influence of posture on the three-dimensional mandibular position relative to the maxillary coordinate system in centric relation.

BACKGROUND

This study aimed to evaluate the influence of postural changes along three spatial axes on the three-dimensional position of the lower incisal point and bilateral condylar points relative to the maxillary coordinate system in Centric Relation (CR).

METHODS

Mandibular movements were recorded in 18 healthy participants using a high-precision jaw movement analysis system while they wore customized 3D-printed Lucia jigs. Three-dimensional coordinates of the lower incisal point and bilateral condylar points were captured. Measurements were performed under various postural conditions, including anterior/posterior body tilt, left/right head tilt, and left/right head rotation.

RESULTS

Postural changes significantly affected mandibular position within the measurement system (P < 0.05). During anterior-posterior body tilt, the recorded lower incisal point and bilateral condylar points shifted posteriorly along the Y-axis, with displacements up to 0.96 mm (P < 0.05). Lateral head tilt induced ipsilateral displacement along the X-axis (0.16-0.43 mm, P < 0.05), while lateral head rotation resulted in contralateral X-axis shifts (0.09-0.18 mm, P < 0.05). Across all postural conditions, the three mandibular landmarks showed predominantly coordinated displacement within the measurement system.

CONCLUSIONS

Postural changes significantly affect mandibular position relative to the maxillary coordinate system. Anterior-posterior body tilt and lateral head tilt induce mandibular movement in the same direction, while head rotation produces movement in the opposite direction. The relative positions of the lower incisal point and bilateral condylar points remain largely stable, consistent with a coordinated displacement pattern.