One of the critical anatomic structures in the anterior mandible is the lingual foramen and its canal. On a periapical radiograph of the mandibular anterior region, a radiopaque entity — the genial tubercle — is often seen. Sometimes the lingual foramen is superimposed over this bony projection and appears as a radiolucent dot surrounded by a radiopaque band. A periapical radiograph may show only the presence of a foramen. A panoramic radiograph does not adequately show the canal or the genial tubercle. These imaging procedures do not have the information of the length and course of the canal(s).

The placement of oral implants in the interforaminal region of the anterior mandible has become an increasingly common intervention, averaging more than one million per year worldwide. Several reports have indicated postoperative complications including hemorrhage and sensory impairments in the mandibular anterior area. These complications suggest the presence of functionally important neurovascular bundles in this region. It is therefore important for the dentist to be aware of the different types of canals and foramina in the anterior mandible.

Several cadaver studies have shown the presence of multiple canals in the mandibular anterior region. MRI studies have also shown presence of neurovascular bundles in these multiple canals. MRI scans are not used for implant planning, while cone beam CT (CBCT) scans are now frequently used for such purposes.

A review of the CBCT data at the University of Minnesota Maxillofacial Imaging Center has shown that the number, location, and direction of the canals vary.

The figures presented here are sagittal cross sections through the anterior mandible from a CBCT scanner. The lower panel represents tracing of the bony outlines as shown on the upper panel. These images show some variations of the canals and foramina as observed during the review. Cross sections A and B represent how the majority of the reviewed CBCT scans appeared. Panel A shows a single canal oriented downwards. Panel B shows two canals, one oriented downwards and another oriented upwards. Cross section C is a representation of two parallel canals. Such a variation appeared less frequently in the study sample. Panels D and E show the intersection of two separate canals. In addition, the image on panel E has an extra small canal at the inferior-most part. Panel F shows a canal exiting through the labial side of the mandible, a variation that is rather uncommon. Panels E and F belong to the same mandible. Thus, this mandible holds four canals in the anterior area. Panel G also shows four canals with varied orientations, three exiting through the lingual cortical plate and one through the labial.

This review shows that CBCT scans can be employed to define the anatomical details of the anterior mandible area. This vital information, when obtained preoperatively, can be critical in determining an appropriate size of the implant and a suitable location at which to place it. Defining the anatomy during preoperative planning can save many patients from prolonged postoperative complications.
 

*Aamna Ali is a pre-dental undergraduate student at the University of Minnesota. She is a recipient of Undergraduate Research Opportunities Program Scholarship from the University to study the variation of lingual foramina and canals.

**Mansur Ahmad, B.D.S., Ph.D., is an Associate Professor of Oral and Maxillofacial Radiology at the University of Minnesota School of Dentistry.