Abstract:

Objective To analyze the anatomical relationship between maxillary premolars and the alveolar bone and maxillary sinus using cone-beam computed tomography(CBCT), in order to provide an anatomical basis for immediate implant placement in maxillary premolars. Methods Data from 351 patients who underwent maxillary CBCT imaging at Yancheng Stomatological Hospital between January 2022 and December 2023 were collected. Measurements included the vertical distance between premolar roots and the maxillary sinus floor, intraosseous root length, angle between the tooth axis and alveolar bone axis, and buccal/palatal bone wall thickness, with comparisons of gender differences. Results The median vertical distance between single-rooted maxillary first premolars and the maxillary sinus floor was 10.16 mm, while that for second premolars was 4.61 mm. For double-rooted first premolars, the buccal root distance was (4.13±3.99)mm and the palatal root was (5.14±3.94)mm. Maxillary first premolars were farther from the maxillary sinus floor than maxillary second premolars, with palatal roots farther than buccal roots. The intraosseous root length of maxillary first premolars was (9.20±1.44)mm, and maxillary second premolars (9.64±2.04)mm. Maxillary first premolars exhibited significantly shorter intraosseous root length than maxillary second premolars. The angle α between tooth axis and alveolar bone axis was 18.89°±6.33° for maxillary first premolars, and 12.65°±6.10° for maxillary second premolars, showing statistically significant differences. The buccal bone wall thickness of maxillary first premolars gradually decreased from 2 mm subcrest to the apex, while palatal bone walls of maxillary first premolars and both buccal/palatal walls of maxillary second premolars progressively thickened from 2 mm subcrest to the apex. Significant correlations were identified between angle α and buccopalatal bone wall thickness at mid-root and the apex: increased α corresponded with reduced buccal wall thickness and enhanced palatal wall thickness. Conclusion The apical region of maxillary first premolars provides sufficient bone volume for primary stability in immediate implantation, though the thin buccal bone wall necessitates careful consideration of implant shape and positioning. Maxillary second premolar roots are closely adjacent to the maxillary sinus floor, requiring implant stabilization with the sinus floor cortical bone or mesiodistal walls of the extraction socket.

Key words: maxillary premolar, immediate implantation, primary stability, CBCT, maxillary sinus