Objective: To evaluate the impact of unilateral functional posterior crossbite, as well as its correction, on head posture in growing children in comparison to children without crossbite.

Methods: A prospective longitudinal controlled clinical trial was carried out including 40 children aged 8-11 years, assigned into a treatment group with unilateral functional posterior crossbite treated with maxillary expansion (n = 20) and an untreated control group without malocclusion (n = 20). Head posture was assessed pre-treatment (or pre-follow-up) (T0) and 2.5 years post-treatment (or post-follow-up) (T1) using an inertial measurement unit (IMU) measuring pitch (forward/backward head inclination), roll (left/right tilting), and yaw (left/right head rotation). Dominant-eye determination was performed using the Battista Della Porta aiming test to evaluate its potential influence on head posture.

Results: No significant differences in head posture were observed between the crossbite and control groups pre- (T0) or post-treatment (T1). Within the crossbite group, an increased pitch post-treatment was noted (P = .008), although not significant after Bonferroni correction. No significant changes were found in the roll or yaw axes neither between groups nor across time points. Eye dominance influenced yaw orientation, with right-eye-dominant participants showing higher yaw angles compared to left-eye-dominant participants (3.61+/-3.46° versus -1.47+/- 3.46°; P < .001).

Conclusion: The presence of a unilateral functional posterior crossbite does not appear to influence head posture, when compared with a control group without crossbite. Furthermore, the orthodontic correction of unilateral functional posterior crossbite does not seem to alter head posture. The results question a cause-effect relationship between crossbite and head posture. The study did identify however a significant influence of eye dominance on head posture.