CBCT is one of the most useful tools in dentistry and one of the easiest to overuse. It answers questions that flat radiographs cannot, and it does so at a dose that is higher than a periapical or a panoramic and lower than a medical CT. The right way to think about it is as a problem-solving study. You reach for it when a specific question needs three dimensions to answer, not as a routine screen for patients who happen to be in the chair.
Here is how I decide, and how I wish more referrals were framed.
Start with the question, not the modality
The useful referral does not say “please take a CBCT.” It says “I need to know X.” If X genuinely requires 3D, the CBCT follows. If a periapical or a panoramic answers X, order that instead. The modality is the last decision, not the first.
Where CBCT clearly earns its place
Several situations reliably justify the volume:
- Implant planning where bone height, width, and the position of vital structures matter. Knowing the exact relationship of the planned site to the inferior alveolar canal or the maxillary sinus is a 3D question.
- Impacted teeth, especially maxillary canines, where the position relative to the roots of neighboring teeth and the presence of root resorption change the surgical or orthodontic plan.
- The inferior alveolar nerve before third molar surgery, when a panoramic shows signs of close association and the surgical risk turns on the true relationship.
- Complex endodontic questions: suspected extra canals, root fractures, resorption, or persistent disease that a periapical cannot resolve.
- Suspected or known pathology where the extent, internal character, and effect on surrounding structures need 3D characterization.
- Trauma and bony abnormalities where fractures or the shape of the bone matter.
- Temporomandibular joint evaluation for bony degenerative change.
Where it usually does not belong
CBCT is not a routine screening tool. It should not be the default for a caries check, a periodontal survey, or a general “let us have a look” at an asymptomatic patient. It should not be ordered because the practice owns the machine and the volume is easy to acquire. And it should be used carefully in children, whose tissues are more radiosensitive and whose lifetime accumulated dose you are helping to write.
The governing idea is the same one that runs through all of radiation safety: justification and optimization. Every scan should be justified by a clinical question that needs it, and once justified, acquired at the lowest dose and smallest field of view that still answers the question.
When to send it to a radiologist
Acquiring the volume and interpreting it are two different skills. A general dentist can plan an implant from a small field of view they ordered for that purpose. A large or complex volume, an unexpected finding, or a case where the stakes are high is a good reason to involve an oral and maxillofacial radiologist. A cone beam volume frequently captures anatomy well beyond the dental region, and incidental findings in the sinuses, the airway, the cervical spine, or the skull base are common and consequential. Someone should be reading all of it, not just the teeth.
If you are ever unsure whether a case needs CBCT, that uncertainty is itself worth a quick conversation. It is faster to ask than to expose a patient to a study that will not change what you do.