The Effect of Gender on Tooth and Gingival Display in the Anterior Region at Rest and During Smiling

The aim of the present study was to investigate the effect of gender on the degree of maxillary and mandibular anterior teeth and associated gingival display when the lips are at rest and during smiling. A total of 247 subjects (144 females [58.3%]; 103 males [41.7%]) were included in the study. All of the subjects had all natural anterior teeth present with no caries, extreme occlusal wear, restorations, extrusion, obvious deformities, or tooth mobility. Subjects with a history of congenital anomalies, lip trauma, or facial surgery were excluded. Crown length, displayed portions of anterior teeth, and associated gingivae at rest and during smiling were measured using a Fowler electronic digital caliper, which had a resolution of 0.01mm. The visible portions of the maxillary anterior teeth were measured vertically from the lower border of the upper lip to the incisal edge of the incisors, or cusp tip for the canines. The visible portions of the mandibular anterior teeth were measured vertically from the upper border of the lower lip to the incisal edges of the incisors, or cusp tip for the canines at the midpoint of the tooth. The measurements were taken by two independent clinicians and they were repeated three times and the mean value was calculated for further analysis. SPSS (V 11) software was used to analyse the data. Statistical analyses were performed by Student t test and ANOVA. The significance level was set at 5%. At rest, males displayed significantly more buccal length for maxillary lateral incisors (1.85 ± 1.27 vs 1.43 ± 1.37; P 0.01), maxillary canines (0.94 ± 0.91 vs 0.35 ± 0.67; P 0.0001), mandibular central incisors (1.09 ± 1.17 vs 0.82 ± 1.32; P 0.01), mandibular lateral incisors (0.98 ± 1.07 vs 0.79 ± 1.22; P 0.05), and mandibular canines (0.87 ± 1.23 vs 0.57 ± 0.98; P 0.05) than females. However, no gender differences in the display of buccal length of the maxillary central incisor were recorded at rest and during smiling. During smiling, no gender differences in the display of buccal length of the anterior teeth were recorded. Gingival display during smiling presented significant differences between gender groups in the maxillary anterior region, with females displaying more gingivae of central incisors (1.85 ± 1.38 vs 1.73 ± 1.07; P 0.05), lateral incisors (2.05 ± 0.93 vs 1.94 ± 1.23; P 0.0001), and canines (2.37 ± 1.24 versus 2.02 ± 1.49; P 0.05). However, no gender differences were observed in the gingival display of the mandibular anterior region. Females displayed 29% vs 25% of maxillary central incisor crown length compared to males at rest. However, during smiling, 87% of maxillary anterior teeth were displayed in females compared to less than 80% in males. Males displayed more of the maxillary lateral, canine, and mandibular anterior teeth than females at rest. During smiling, no gender differences in anterior tooth display were recorded, however, females displayed more maxillary gingivae than males.