Predictors of buccal bone thickness in the esthetic zone of patients with gummy smile: a cross-sectional study

PURPOSE: This study aimed to investigate buccal bone thickness (BT) patterns in the maxillary anterior region, examine correlations with clinical and radiographic parameters, and assess the predictive value of these parameters in patients with gummy smiles. METHODS: Eighty-four gummy smile patients were included. Six anterior maxillary teeth (canine to canine) per patient were evaluated using clinical examination, digital photography, cone-beam computed tomography, and intraoral scanning. Pearson correlation and multiple regression analyses were performed. RESULTS: Thick BT (>1 mm) was observed in 75.4% and 69.1% of teeth at 1 mm (BT1) and 3 mm (BT3) below the bone crest (BC), respectively. Thicker BT was more prevalent in males, canines, thick-flat gingival architecture, and sagittal root position class III. Positive correlations were found between BT at both levels and keratinized tissue width, smile line, crown width-to-length ratio, gingival thickness (GT) at the cementoenamel junction (CEJ), and sagittal root angulation. Negative correlations were identified between the CEJ-to-BC and gingival margin-to-BC distances and GT at 1 and 3 mm. Multiple regression analysis identified GT as the strongest predictor of BT. CONCLUSIONS: Gummy smile patients predominantly exhibit a thick bone morphotype. GT below the BC was the strongest negative predictor of BT. These distinct bone characteristics may affect treatment planning for esthetic procedures such as surgical crown lengthening.