Background Excessive gingival display (EGD), or a gummy smile (GS), is a mucogingival deformity that can be of concern to patients. The prevalence of GS etiologies, such as altered passive eruption (APE) and hypermobile upper lip (HUL), has not been reported. The aim of this study was to assess the prevalence of APE and HUL in patients seeking to correct their GS, and to determine possible prevalence differences among patients with different gingival display (GD) levels. Methods During clinical screening of patients interested in participating in a GS treatment study, GD diagnosis, GD level, and presence of APE and/or HUL were determined. Descriptive statistics were calculated for APE, HUL, and GD group prevalence. Fisher's exact test was used to determine difference in frequency of etiologies between GD groups. Results Fifty‐six patients were clinically screened (27.2 ± 7.2 years old; 85.7% females; 94.6% with GD, 5.4% without GD). Among patients having GD, 75.5% presented with GD≥4 mm and 24.5% with GD<4 mm. Prevalence of etiologies was: 20.8% APE alone, 45.3% HUL alone, and 34% APE and HUL. The prevalence difference between GD≥4 mm and GD<4 mm groups was statistically significant (p<0.0001); for ≥4 mm GD: 5% presented with APE alone, 50% HUL alone, and 45% APE and HUL; for <4 mm GD: 69.2% presented with APE alone and 30.8% HUL alone. Conclusion Among patients seeking GS treatment, HUL is the most predominant etiology and it is often present in combination with APE.

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