Assessment of the correlation between patients with a unilateral cleft lip and palate (UCLP) and non-cleft individuals regarding the duration and speed of maximum smile using 4d imaging

Monaghan, Jessica (2026) Assessment of the correlation between patients with a unilateral cleft lip and palate (UCLP) and non-cleft individuals regarding the duration and speed of maximum smile using 4d imaging. MSc(R) thesis, University of Glasgow.

Abstract

In a cleft lip and palate (CLP), the upper lip and palate fail to develop correctly during embryological development. CLP is managed by surgical interventions; cleft lip repairs, nasal reconstruction and revision procedures. Asymmetry is noted in the nasolabial region (Hallac et al., 2017), due to scarring, muscular pull and underdeveloped muscles around the cleft causing weakness or muscular imbalance which can cause profound psychosocial impact (Yezioro-Rubinsky et al., 2020).

Scar revision during childhood can minimise the psychosocial impact (Tan and Pigott, 1993) and restore function to facial muscles. The decision for revision surgery is currently based on subjective evaluation of limitations by a surgeon. Objective quantification of dynamic motion with 4D imaging could allow comparison of different treatments, monitor patients for worsening and guide future intervention. Each expression has specific muscle groups that undergo contraction and relaxation during different phases of movement. Some of these muscles are surgically corrected during repair and others are relatively untouched.

This study aims to objectively assess dynamic dysmorphology from rest to maximum smile with 4D imaging for individuals with a unilateral cleft lip and palate (UCLP) and unaffected individuals, to improve quality of care and treatment for patients with UCLP. The impact that residual scarring has on expression speed during the maximum smile was also investigated. Maximum smile for the two groups were compared, 31 UCLP patients (13-17yrs) and 34 control participants. Nine landmarks were used; 6 paired landmarks to analyse lip motion, cheilion, crista philtri and lower lip and 3 landmarks to minimize head motion. Different phases of the smile were assessed; onset, apex and offset and the speed for the individuals to reach maximum smile. Comparison allows differences between groups and intrapersonal differences between right and left to be identified.

Results show UCLP participants have longer onset and offset (contraction and relaxation) phases and a longer smile duration (2.02 secs) than unaffected individuals (1.33 secs). There was measurable asymmetry in philtrum magnitude and speeds between the two sides in UCLP participants with the cleft side significantly slower (7.24mm/s) than the unaffected side (8.22mm/s). Although the same pattern was seen for cheilion magnitude and speed, this did not reach statistical significance (cleft side 28.69 mm/s, non-cleft side 32.05 mm/s). In contrast the cleft side had significantly greater magnitude and speeds at the lower lip (20.98mm/s) than the non-affected side (19.22mm/s). Asymmetric movement on the lower lip is due to distorted muscle dynamics, secondary to the asymmetric upper lip muscles during expression phases. Less muscular development on the cleft side causes weakness, reduced control and tension from scarring limits upper lip movement, causing the lower lip to compensate for the deficit. Control participants had no significant speed or magnitude differences for the landmarks on opposing sides, indicating no discernible asymmetry.

During maximum smile, all landmarks on the cleft side exhibited slower speeds than control participants (cheilion 34.89 mm/s slower, philtrum 14.53 mm/s slower, lower lip 18.1 mm/s slower). This was also reflected for the UCLP participant’s unaffected side (Cheilion 37.71 mm/s slower, philtrum 12.21 mm/s slower, lower lip 21.14 mm/s slower) when compared to individuals without a cleft. Indicating restriction in muscular activity on both sides regardless of which side is affected by the cleft.

The odds of having reduced speeds at the cheilion are 87% higher when a cleft is present and it is 3 times more likely to have slower speeds at the philtrum on the cleft side than in an unaffected individual. Unlike other landmarks, the lower lip is faster on the side affected by the cleft than the unaffected individuals.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Subjects: R Medicine > RK Dentistry
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
• Supervisor's Name: Naudi, Dr. Kurt, Benington, Mr. P., Ayoub, Professor Ashraf and Ju, Dr. Xiangyang
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-85726
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2026 14:26
• Last Modified: 30 Jan 2026 14:27
• Thesis DOI: 10.5525/gla.thesis.85726
• URI: https://theses.gla.ac.uk/id/eprint/85726