Atypical Anatomy: Tips on What to Look for in CBCT Data

While most of the scans you read will fall into the “normal anatomy” category, the logical next step in the journey of learning how to interpret data sets from cone beam computed tomography (CBCT) imaging is developing proficiency at deciphering anatomical variations. These variations can often be seen in intraoral and extraoral radiography, and it is sometimes helpful to use 3D radiography to fully understand certain variations; which otherwise could result in failure to diagnose.

One of the most common anatomical variations of a critical structure is the anterior extension/loop of the inferior alveolar nerve. Visualizing this structure is imperative when planning surgical procedures in the anatomical areas around mental foramen and the immediate area anterior to it.

Anterior extension of Inferior Alveolar canal: the red circle shows anterior extension and the yellow circle shows mental foramen

In addition to mental foramen, accessory foramen(s) can also be noted as a variation of normal anatomy in the mandible.

The temperomandibular joint (TMJ) area can exhibit wide variations in normal anatomy, which has to be correlated with clinical findings and additional imaging if necessary to establish the absence of any pathology. One of the most common variations can be the inter-articular space of the joint. This space may vary widely between contralateral joints of the same patient and between patients as well. The complexity of this anatomical region warrants a thorough review of all information available.

Lingual undercuts can also be observed in varying degrees in the dento-alveolar region of the mandible. These are easiest to see in views that have a greater emphasis on the buccal lingual dimension.

Normal maxillary sinus may exhibit mild mucoperiosteal thickening—predominantly on the floor of the sinus. It’s important to correlate these clinical findings to avoid a failure to diagnose any underlying clinical condition both of an odontogenic and non-odontogenic nature.

Variations in morphology of alveolar crest may also be noted in dentate and edentulous areas of the jaws. These may vary based on numerous factors, such as resorption related to aging, the time frame that the individual has stayed edentulous, and systematic factors related to the patient.

To conclude, it’s important to remember that identifying normal variations is always the first step to systematic interpretation of all types of images. But since patients come in all shapes, sizes and anatomies, proficiency in identifying the variations is equally essential.