Associations between global postural factors and mandibular lateral deviation during maximal mouth opening in healthy young adults: cross-sectional study

Mandibular lateral deviation during mouth opening may reflect temporomandibular joint and masticatory dysfunction. While postural factors are implicated in temporomandibular joint disorders, the relationship between global posture and mandibular lateral deviation in healthy individuals remains unclear. Therefore, this study aimed to investigate the correlations and associations between mandibular lateral deviation during maximal mouth opening and global postural factors in healthy young adults. This cross-sectional study involved 110 healthy adults (aged 20–39 years) recruited between September 2024 and August 2025 through advertisements at Yonsei University and in downtown Wonju, Gangwon, South Korea. Twelve postural variables were assessed using a three-dimensional posture analysis system: head posture, shoulder height difference, rounded shoulder, thoracic kyphosis, lumbar lordosis, spinal lateral deviation, three pelvic parameters (pelvic tilt, rotation, obliquity), left/right hip-knee-ankle angles, and knee flexion angle. Mandibular kinematics, including lateral deviation and maximal mouth opening distance, were assessed using video-based motion analysis. Relationships with global postural parameters were evaluated using Spearman’s correlation and stepwise multiple regression analyses. The regression model exhibited an adjusted R2 of 0.193, and knee flexion angle (β = − 0.415, p < 0.001) and spinal lateral deviation (β = − 0.180, p = 0.041) emerged as significant factors associated with mandibular lateral deviation. These findings suggest a potential interrelationship between global posture, specifically lower limb and spinal alignment, and mandibular function. However, further longitudinal and interventional studies are warranted to confirm these associations and clarify causal mechanisms.