when do i need a cbct scan instead of an x ray

CBCT stands for cone beam computed tomography. It is a 3D X-ray of the teeth and jaws: instead of one flat picture, the machine takes many images as it rotates around your head and a computer builds them into a model your dentist can slice in any direction. It is a powerful tool, but it uses more radiation and costs more than a normal dental X-ray, so it should be used when the extra information will change a decision.

Why a flat X-ray sometimes is not enough

A normal X-ray squashes a three-dimensional jaw onto a flat image. Structures in front of and behind each other overlap. It cannot show the width of bone, only its height. It cannot tell whether a root lies on the cheek side or the tongue side of a nerve. When the answer depends on depth or direction, CBCT is the right tool.

When CBCT is commonly advised

• Dental implants: to measure the height and width of bone, the position of the sinus in the upper jaw and the nerve canal in the lower jaw, and to decide whether a bone graft is needed. See our implant page.
• Wisdom teeth near the nerve: when an OPG suggests the roots of a lower wisdom tooth overlap the nerve canal, CBCT shows the real relationship and helps plan a safer extraction. See our wisdom tooth extraction page.
• Difficult root canals: suspected extra canals, severely curved roots, calcified canals, or a root canal that keeps failing.
• Suspected root cracks or fractures that a flat image cannot confirm, although even CBCT does not always show fine cracks.
• Cysts, tumours and unusual lesions: to see their size and what they are pressing on.
• Jaw injuries: after a road accident or fall, to look for fractures.
• Impacted canines and complex orthodontic cases, and some jaw joint problems.

When CBCT is usually not needed

• Checking for routine cavities: ordinary bitewing or IOPA X-rays do this better and with far less radiation.
• Most straightforward root canals and simple extractions.
• "Just to be thorough" with no specific question in mind.
• Routine check-ups.

If a clinic recommends a CBCT, it is fair to ask what question the scan will answer and how the result might change your treatment.

Radiation and safety

The dose from a dental CBCT varies widely with the size of the area scanned and the machine settings. A small-field scan of a few teeth is much lower than a scan of both full jaws, but any CBCT is higher than a single intra-oral X-ray. Children and pregnant women need extra care in deciding. Ask for the smallest field of view that answers the question.

Reading the scan matters as much as taking it

A CBCT contains far more information than the dentist asked for: sinuses, airway, bone outside the area of interest. Someone needs to look at all of it, not just the one tooth. Complex scans benefit from a report by an oral and maxillofacial radiologist.

At AR 32

If a CBCT scan is advised for you, we will tell you where it is done and what it costs, and your dentist will go through the scan with you; our oral radiology department can review complex images. More on imaging choices is on our diagnosis hub.