[Classification of the anatomical structures of maxillary central incisor root by cone-beam CT]

Objective: To examine the root position of the maxillary central incisors and to provide clinical reference before the immediate implant placement. Methods: Cone-beam CT (CBCT) data of the maxillary central incisors of 934 patients (934 incisors) was selected and the root position classsified. The sagittal root position in the alveolar bone was classified as buccal, middle, or palatal. The buccally positoined type was further classified into three subtypes of Ⅰ,Ⅱ, and Ⅲ. Results: Most of the maxillary incisor root (95.4% [891/934]) was positioned buccally. Among the buccal-type incisors, the subtypes Ⅰ, Ⅱ and Ⅲ accounted for 47.5% (423/891), 44.2% (394/891), and 8.3% (74/891). In the 4 mm apical to the cemento-enamel junction and the middle of the root, the thickest buccal bone wall was 0.86 and 0.95 mm, the thickest palatal bone wall was 1.65 and 2.37 mm. In the apical location, the thickest buccal bone wall was 1.89 mm, the thickest palatal bone wall was 7.83 mm. Conclusions: Most of the maxillary central incisors studied are positioned buccally, and half of these patients have adequate buccal bone and are suitable for immediate implant placement.