Association of Clinical, Biomechanical, and Psychosocial Factors with Smile Dynamics in Unilateral Cleft Lip: A Multicenter Observational Study.

Objective: To investigate the association between clinical, biomechanical, and psychosocial factors and smiling behavior in individuals with treated unilateral cleft lip with or without cleft palate (UCL ± P) compared to non-cleft controls.

Design: Multicenter observational study in New Zealand.

Participants: Individuals aged ≥15 ( = 42) comprised 2 study groups: a UCL ± P group ( = 21) and a non-cleft control group ( = 21).

Methods: Participants viewed an amusing video while their facial expressions were recorded. Smile features were automatically detected via software. A clinical outcome, nasolabial esthetics, was scored using the Asher-McDade system. Perioral biomechanical properties were measured via myotonometry. Smile Esthetics-related Quality of Life (SERQoL), Orofacial Esthetics Scale (OES), and personality (IPIP-NEO-60) questionnaires were completed.

Results: Smile features and personality traits did not differ between the groups. Participants with UCL ± P exhibited higher stiffness (+44.2%; Cohen's = 1.6) and tone (+22.6%; Cohen's  = 1.9) at the cleft scar site, and higher decrement (or lower elasticity, +8.5%; Cohen's = 0.8) adjacent to the scar. Nasolabial esthetics and elasticity of the scar correlated with the duration of smiles and relative smile time (-0.50 < R < -0.44;  < .05). Participants in the UCL ± P group had lower scores for the OES and higher impacts on SERQoL for social contacts and dental self-confidence.

Conclusions: Adolescents and adults with UCL ± P exhibit similar smile behavior as their cleft-free peers-at least in non-social settings. Nasolabial esthetics and perioral biomechanical properties are associated with propensity to smile. UCL ± P is negatively associated with smile-related quality of life and an individual's perception of their facial appearance.