Aferição da força muscular do sorriso gengival: uma nova abordagem

Abstract

Excessive gingival exposure is considered the second change with the greatest oral aesthetic impact, reflecting on self-esteem. Gummy smile, considering a gingival exposure from 3 mm, can have dental, skeletal and muscular etiologies, with lip hyperactivity being the most prevalent. Currently, the assessment of lip muscle strength (F) is carried out empirically, making the precision of some therapeutic methods difficult. The objective of this study was to create a method for evaluating muscular F related to the act of smiling, through the development of equipment that would make it possible to verify the strength exerted by the different muscles that move the upper lip during a smile, and to establish a correlation between the lip translation and individual/total F exercised. The sample consisted of 89 individuals, mean age 28 ± 8.4 (SD), 80.9% female and 19.1% male, divided into 4 groups (G): G1 - Upper lip hyperactivity (9%); G2 - Other causes (dental, skeletal or joints) (19.1%); G3 - Control (33.7%); G4 - Hyperactivity combined with one or more etiologies (38.2%). Equipment was developed to measure the F of each lip muscle during a smile, compared within the different G, through filming the movements of the equipment's springs analyzed by the Tracker® software. Statistical analysis was performed using SPSS 21.0 software and was subjected to the ANOVA test and then Tukey's post hoc test and the chi-square test. The results demonstrated that lip hyperactivity was the most prevalent isolated or combined etiology (68.2%) in the sample and that this group presented 30% greater strength than the other groups. G4 (0.15 N ±0.03) presented significantly higher F in the 6 muscles evaluated, compared to G2 (0.11 N ±0.03) and G3 (0.01 N ± 0.02) (p< 0.001). The zygomaticus major muscle on the right and left sides of G1 was significantly stronger than G2 and G3. A statistical difference was observed between the F of the zygomaticus major muscle (0.025 N ± 0.007) and the other muscles (0.0021 N ± 0.006 and 0.019 N ± 0.006, zygomaticus minor and lip elevator respectively), being the strongest in the entire the sample (p<0.001). The lip translation in mm was evaluated in its average F and the different displacements from 6 mm, observing a statistically significant difference (p<0.001) between 6mm and 7mm, 7mm and 8mm, 9mm and 10mm, and 9mm and 11mm. The largest DL forces were observed from 8 mm onwards (0.12± 0.02). Between 8/9 mm, 10/11 mm, and 11/12 mm, no significant difference was observed. It was concluded that lip hyperactivity alone or combined with other etiologies was the most prevalent cause of gummy smile. Individuals with lip hyperactivity showed greater muscle F compared to other etiologies or individuals without a gummy smile and, from 8 mm of lip displacement, an increased and significant muscle F is observed.