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

TL;DR

This study compares smile dynamics in people with cleft lip and non-cleft individuals, finding biomechanical and psychosocial factors influence smiling behavior and quality of life.

Contribution

The study is the first to associate clinical, biomechanical, and psychosocial factors with smile dynamics in UCL ± P individuals using a multicenter observational approach.

Findings

Participants with UCL ± P showed higher stiffness and tone at the cleft scar site compared to controls.

Nasolabial esthetics and elasticity correlated with duration and frequency of smiling.

UCL ± P individuals reported lower quality of life related to smile esthetics and dental self-confidence.

Abstract

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.

Multicenter observational study in New Zealand.

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

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.

Smile features and personality traits did not differ between the groups. Participants with UCL ± P exhibited higher stiffness (+44.2%; Cohen's d = 1.6) and tone (+22.6%; Cohen's d = 1.9) at the cleft scar site, and higher decrement (or lower elasticity, +8.5%; Cohen's d = 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; p < .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.

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.

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