What is a CBCT scan? A plain-English guide to 3D dental scans

How a CBCT scan works

A normal dental X-ray is a single flat picture, so everything in the beam’s path is overlapped. A CBCT works differently. An X-ray source and a detector rotate once around your head, taking a series of images from different angles. A computer combines them into a 3D block of data called a volume. Your dentist can then scroll through it slice by slice in any direction: front to back, side to side or top to bottom.

The 3D view lets a dentist measure bone height and width for an implant. It shows how close a wisdom tooth root is to the nerve, where an unerupted tooth lies and the shape of a root canal. A flat image can only suggest these things.

Field of view: why the scan size matters

The “field of view” is the size of the area scanned. A small field might cover two or three teeth. A larger one can cover a whole jaw or both jaws. UK guidance shows that the dose generally rises as the field of view gets larger, so the rule is to scan the smallest area that answers the question. We offer small, medium and large fields of view. Our largest is 16 cm high by 9 cm deep. Your dentist’s referral tells us which is needed.

What happens on the day

1. Check-in. We confirm your details and the area to be scanned, and answer any questions.
2. Remove metal. We’ll ask you to take off earrings, glasses, hair clips and removable dentures or braces. Metal in the scan area causes streaks on the image. Fillings, crowns and implants can’t be removed, and they can produce artefacts that your dentist allows for when reading the scan.
3. Positioning. You stand in the scanner and rest your chin or bite gently on a support to keep your head still.
4. The scan. The arm rotates around your head, usually in under 20 seconds. Keep still and breathe normally.
5. Done. The whole appointment is normally around 10–15 minutes. Nothing stays in your body afterwards, and you can carry on with your day.

Radiation in context

Everyone in the UK receives natural background radiation from the ground, the air and food. UK dental selection criteria put this at around 2,230 microsieverts (µSv) a year on average. Figures published by those criteria and by UK health protection guidance are summarised below. Doses vary widely between machines and settings, so treat them as ranges, not exact values for any one scan.

Examination	Typical effective dose	Roughly equivalent to
Panoramic X-ray (OPG)	2.7–38 µSv	No more than about six days of background radiation
Small-field dental CBCT	11–214 µSv	Between about two days and six months of background radiation, depending on the machine and settings
Medium/large-field dental CBCT	18–674 µSv
Chest X-ray	18 µSv	About three days of background radiation
Medical CT of the jaw	250–1,410 µSv	Generally higher than dental CBCT

The risk from a dental scan falls into the lowest risk category, but it is not zero. That is why every scan has to be justified and kept to the lowest dose that answers the question. More on our radiation safety page.

Why a dentist has to approve every scan

Under the Ionising Radiation (Medical Exposure) Regulations 2017, known as IR(ME)R, no X-ray exposure may be carried out unless a practitioner has justified it. Justifying it means showing a sufficient net benefit for you, weighed against the detriment. It also means considering whether another technique with less or no radiation would achieve the same goal. In dental practice, that practitioner is normally a dentist. So:

• If your own dentist has asked for a CBCT, they refer you with the clinical details, and the scan is authorised before it is taken.
• If you don’t have a dentist, our booking form adds a short consultation (£54) so a clinician can assess whether a scan is needed. Sometimes the answer is an OPG instead, or no scan.

Children and pregnancy

Children are more sensitive to radiation. UK guidance estimates young children’s risk at about two to three times that of adults in their thirties for the same dose. CBCT for children is used only when clearly needed, with the smallest possible field of view. See CBCT for orthodontics.

Pregnancy: please tell us if you are or might be pregnant. UK selection criteria state that dental CBCT and panoramic X-rays do not need to be delayed until after the birth. They also recommend offering pregnant patients the option of delaying non-urgent X-rays, and you are welcome to take that option.

What happens to your scan

Files are supplied as DICOM, the standard format for medical images, with JPG previews. They are sent securely to your dentist, and viewer software is available on request. UK guidance requires the whole scan to be clinically evaluated, including areas outside the main question. Your dentist either does this or asks for a formal radiology report (£115).

Costs: CBCT £139 per arch; OPG £79. A £30 deposit secures an online booking and comes off your fee on the day. See prices or what affects the cost.

Book a scan Call 01922 326040