An evaluation of smile components in skeletal malocclusion in sagittal plane

The purpose of this study was to analyze of smile components in subjects with Class I, Class II div I and Class III malocclusions with normal vertical skeletal pattern and to evaluate the effect of sagittal malocclusions on smile components. Video equipment and a cephalostat device were used to capture smiles in 80 subjects with Class I (23 female, 7 male, mean age: 20.77±3.17 years), Class II div 1 (22 female, 8 male, mean age: 17.36±3.00 years) and Class III (12 female, 8 male, mean age: 17.59±3.59 years) malocclusions. Subject's spontaneous smiles were elicited by watching funny movies. Two frames were selected from the videographic records including rest and the widest spontane smiling for each subject. The rest and smile frames were analyzed with the Image J® program. SPSS version 23.0 software was used for statistical analysis of the data. The parameters which showed statistically significant differences between the sexes were found to be higher in males than females except smile height and mandibular incisor display. The smile arc showed no statistically significant difference among the groups and genders. The values of outer commissural lengths, buccal corridor ratio and visible dental width were higher in Class I subjects than Class II subjects. Maxillary incisal edges to lower lip distance and upper lip thickness at rest and smile showed higher values in females with Class II malocclusions than the other groups. The linear measurements of buccal corridor were higher in Class II malocclusion than Class I malocclusion for females. Mandibular incisor display was found to be higher in Class II malocclusion than Class III malocclusion for males. The smile area in Class I female subjects was higher than Class III female subjects. The incidence of high smile line in Class I female subjects was higher than the other groups. The sagittal skeletal malocclusions and genders are effective on the smile components.