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