Objective: The objective was to evaluate the anatomical relationship between the mandibular foramen and surrounding structures using CBCT and to investigate the potential causes of inferior alveolar nerve block (IANB) failure.
Method and materials: In this retrospective study, CBCT images of 222 mandibular sides from 111 patients (55 men, 56 women; aged 18–45 years) who underwent CBCT examination at the Shenzhen University General Hospital between January 2018 and December 2020 were analyzed. Three-dimensional models were reconstructed, and measurements of angles and distances related to the mandibular foramen were performed. The presence of a bony protuberance on the medial side of the mandibular ramus was evaluated. Differences between sexes were assessed using paired t tests or Wilcoxon rank-sum tests (α = .05).
Results: The angle between the anterior–posterior line of the mandibular ramus and the line connecting the innermost point to the mandibular foramen (angle AP–IF) was significantly greater than zero (P .05), indicating the presence of a bony protuberance. The angle between the midline and the line connecting the mandibular premolar contact point to the mandibular foramen (angle F45MnLP-ML) was 49.69 ± 2.17 degrees in men and 48.19 ± 2.20 degrees in women (P .001). The distance from the occlusal plane to the mandibular foramen was 9.45 ± 3.40 mm in men and 8.28 ± 3.41 mm in women (P = .011).
Conclusion: The presence of a bony protuberance on the medial side of the mandibular ramus may contribute to IANB failure. Adjusting the needle insertion angle and height/vertical distance according to the reported measurements may improve IANB success rates. These findings may help clinicians optimize IANB techniques and improve success rates by adjusting needle insertion angles and heights/vertical distances based on individual patient anatomy.