Influence of Facial and Occlusal Characteristics on Gummy Smile in Children: A Case-Control Study

Objective: To determine the association between occlusal and soft tissue characteristics with the presence of gingival smile (GS) in a pediatric population with inter-transitional mixed dentition. Material and Methods: Case-control study was performed with a probabilistic sample of 163 children in inter-transitional mixed dentition (age:8.8 years ±0.8). Cases were 37 children with GS, and controls were 126 children without GS. Occlusal variables were assessed through clinical examination, and soft tissue variables were assessed through photograms. Kappa test and intraclass correlation coefficient were done (0.87-0.96). The association between malocclusion, gender, and types of smile was assessed using a Chi square test. Comparison of quantitative variables in smile groups was made by Student t test. A multivariate binary logistic regression was performed. Results: Class II malocclusion, short upper lip at smile and short incisor  clinical crown, were risk factors for gummy smile (OR= 10.4, 95%CI 3.07- 34.95,  OR= 2.1, 95%CI 1.44- 3.13 and OR= 2.5 95%CI 1.34- 4.54 respectively). Lower facial height was a protective factor against GS (OR= 0.76; 95%CI 0.69- 0.85). The logistic regression model explains 48% of GS variability. Conclusion: Class II malocclusion is considered a risk factor for gummy smile. Other variables associated to gummy smile were short upper lip and short incisor clinical crown. Clinicians should considered these aspects in clinical examination of each patient to provide an adequate diagnostic and plan of treatment to control and/or correct a GS.