Viscoelasticity of the Face in Adult Patients With a Repaired Unilateral Cleft Lip/Palate

Objectives: 1) To clarify the degree of error in the measurement of physical properties of facial soft tissue in healthy individuals; and 2) to investigate whether physical properties are significantly different between affected side and unaffected side in patients with a repaired unilateral cleft lip (CLP).
Methods: Experiment 1: The hardness, elasticity, and viscosity coefficient of facial soft tissues including the Cupid's bow, cheilion, alar, and cheek were measured three times in five healthy adults using a viscoelasticity-measuring instrument (Vesmeter-E100Hs, Japan). Average (M) and relative error (E = difference between the maximum and minimum values) were determined for each. The average E and M were calculated to determine the error rate as E/M.
Experiment 2: The above-mentioned physical properties of 32 patients with a unilateral CLP who received orthodontic treatment at a university hospital were measured (17 males, 15 females; mean age = 21.6±5 years). Any significant difference between affected and unaffected sides was statistically examined for using a paired t-test (p<0.05).
Results: Experiment 1: The error rates for hardness, elasticity, and viscosity coefficient were 11.0%, 16.4%, and 12.8%, respectively, indicating clinically useful reproducibility.
Experiment 2: The hardness of affected side was significantly greater than that of unaffected side. Additionally, viscosity coefficient of affected side was smaller at the Cupid’s bow, cheilion, and alar. Elasticity of affected side was smaller at the cheilion and alar. No significant difference in hardness, viscosity, and elasticity was found at the cheek.
Conclusions: Significant differences in hardness, viscosity, and elasticity between affected side and unaffected side at the Cupid’s bow, cheilion, and alar were observed. Thus, lip scars might have affected the physical properties of surrounding soft tissues including the cheilion and alar.