Observations of the anterior loop of the inferior alveolar canal

The inferior alveolar nerve may extend beyond the mental foramen as an intraosseous anterior loop. The purpose of this study was to determine if panoramic radiography accurately identifies the anterior loop of the inferior alveolar canal. Adult skulls (n = 25) were radiographed using two panoramic machines both with and without radiopaque markers placed into the inferior alveolar canal and anterior loop. The anterior loop was also measured directly using flexible tubing (2 mm in diameter). Significantly fewer loops were detected in radiographs as compared with anatomic assessment (P < .001). A significant loop (> 2 mm) was identified in 92% to 96% of the direct measurements, whereas radiographs identified only 56% (Panelipse) and 76% (Orthoralix). Analysis of variance demonstrated that the skeletal length of the anterior loop was significantly greater than that measured radiographically (P < .0001). The average length of the anterior loop based on direct measurements was 6.95 mm, whereas radiographic measurements were 3.18 mm (Panelipse) and 3.45 mm (Orthoralix). The difference in detection of anterior loops among the radiographic procedures studied was not significant (P > .05).