Class II functional appliance treatment and dynamic three‐dimensional mimic muscle evaluation

Background Functional appliances have skeletal and dentoalveolar treatment effects, but knowledge on their effect on facial expressions is limited. Objective To analyse changes in facial expressions, using three‐dimensional (3D) mimic muscle evaluation, in growing children with Class II malocclusion and large overjet, undergoing functional appliance treatment. Methods Fifteen growing children with Class II division 1 malocclusion, selected prospectively, had dynamic 3D recordings of facial expressions prior to and 12 months after commencing functional appliance treatment. Facial expressions recorded were smile and lip pucker, and the movements of the oral commissures were analysed, as well as mouth width and its symmetry. A control group of fifteen age‐ and sex‐matched growing children without immediate need for orthodontic treatment had similar recordings prior to and after a 12‐month observation period. Results In the treatment group, the Class II malocclusion in all children improved after 12 months of functional appliance wear. With regard to movements of the oral commissures, the initial recordings of the treatment group did not show any significant differences to the control group for neither smile nor lip pucker. Differences were noted however when looking at mouth width asymmetry, where this tended to become more symmetrical in the functional appliance treatment group, during rest and during smiling, while it became more asymmetrical in the untreated control group. Conclusion The use of removable functional appliances in children with Class II division 1 malocclusion may have a positive effect on mouth width symmetry when smiling, making it more symmetrical.