Diagnostic Imaging: Dental X-rays and CBCT Scans

An examination shows the surfaces of the teeth and gums. Much of what shapes treatment lies out of sight: between and inside the teeth, at the root tips and in the bone. Dental imaging is used to look there. It helps diagnose decay, gum disease and infection at the tip of a root¹. Three-dimensional scans also have uses in root canal treatment, orthodontics and assessing the jaw before an implant¹. How gum disease is diagnosed and treated is explained on our gum disease page.

An image is worth taking only if it can change what happens next. The European Commission published guidelines on dental CBCT in 2012 ("the European guidelines" below). They state that a scan should potentially add new information to aid the patient’s management². Selection Criteria for Dental Radiography (2018) is a guide to choosing dental X-rays, written for dentists in the UK ("the selection guidance" below). It reminds dentists that X-ray exposure involves a risk to the patient¹. The expected benefit of each image is therefore weighed against that risk, as explained under "Clinical justification and optimisation" below.

Images also serve as a record. When an implant crown or bridge is finished, a consensus report recommends an X-ray and probing measurements as a baseline³. Later images are compared with that baseline.

Dental imaging is either two-dimensional (2D), which flattens the teeth and jaws into one picture, or three-dimensional (3D).

• Intraoral X-rays are taken with a small sensor or film held inside the mouth. A bitewing shows the crowns of the back teeth and the bone between them. A periapical X-ray shows one or a few whole teeth, down to the root tips.
• Extraoral 2D X-rays are taken with the sensor outside the mouth. A panoramic X-ray (also called an OPG) shows both jaws and all the teeth in one wide image. A cephalometric X-ray is a side view of the skull, used in orthodontics.
• Cone beam CT (CBCT) produces high-resolution, three-dimensional images of teeth and jaws¹. The scanned area, called the field of view, can be limited to the teeth and jaws or extend to the face².
• Medical computed tomography (CT) and magnetic resonance imaging (MRI) are done in hospitals or imaging centres. The section on limitations below explains when they are used instead of CBCT.

An intraoral scan, used to make crowns, bridges or aligners, is a different thing. It records only the surface of the teeth and gums.

For most everyday questions, a 2D X-ray is the first choice. The selection guidance finds intraoral X-rays better than panoramic X-rays for diagnosing decay, gum disease and infection at the root tip¹. For these it calls intraoral X-rays the optimal examination, because of better detail and lower radiation doses¹.

The European guidelines date from 2012 and recommended their own review within five years. Read them with that age in mind. They say a scan should be used only when the question cannot be answered adequately by lower dose conventional (traditional) radiography². They list situations where CBCT is not indicated²:

• finding decay;
• checking bone support in gum disease, as a routine;
• diagnosing infection at the tip of a root, or showing the shape of the root canals, as a standard method. The guidelines note that an operating microscope may reveal canal anatomy without radiation;
• assessing every wisdom tooth before removal, as a routine;
• large-volume scans for orthodontic diagnosis, as a routine.

After an implant has been placed, recommendations say 2D intraoral X-rays are still the main tool⁴ when it needs checking. So an implant can usually be followed up with intraoral X-rays.

A CBCT scan may be justified when a 2D X-ray leaves open a question that matters for treatment. The European guidelines name selected cases², each where ordinary X-rays do not give enough information:

• a suspected root fracture after an injury to a tooth;
• root canals whose shape stays unclear, most often in back teeth with several roots;
• some areas of bone loss beside or between the roots of teeth affected by gum disease;
• teeth that have not come through, before surgery;
• a lower wisdom tooth that is to be removed, where X-rays suggest its roots are in close contact with the nerve canal.

Our pages on wisdom tooth removal and root canal treatment explain those treatments.

Before implants. The European guidelines accept CBCT before an implant as an alternative to other cross-sectional (3D) methods. The condition is that the CBCT dose is shown to be lower. They give that recommendation their lowest evidence grade (D)². They add that the first question is whether cross-sectional imaging is needed at all. Recommendations from 2018, based on a narrative review, say a scan could be justified for diagnosis and planning before surgery⁴. Neither source sets a rule for every implant: both leave the decision to the dentist, for each patient. On implants, this page draws only on these two sources, from 2012 and 2018. How an implant is planned at our clinic is explained on our dental implant treatment page. Treatments that add bone where it is needed are covered on our bone grafting and sinus lift page.

Two principles apply to every dental X-ray and scan.

Justification. The expected benefit has to outweigh the risk, for you as an individual. The selection guidance calls this both an ethical and a legal requirement¹ for dentists in the UK. It describes X-rays taken by a general rule, rather than prescribed for the individual, as unacceptable¹. It defines a routine X-ray as one taken whether or not there are signs or symptoms. Routine X-rays of this kind cannot be justified¹. Check-up X-rays chosen according to your own risk are different. In checking for decay, your assessed risk is central to deciding when further X-rays are taken¹. The interval should be specific to each patient¹. For CBCT, the European guidelines add that each scan must be justified for each patient². It should not be repeated ‘routinely’² without a new assessment of benefit and risk.

Optimisation. Once an image is justified, the dose should be as low as still gives a reliable answer. For CBCT, that means the smallest scanned volume compatible with the clinical situation². It also means the resolution compatible with adequate diagnosis and the lowest achievable dose². The 2018 implant recommendations describe the aim as a dose as low as diagnostically acceptable⁴. Equipment matters too. The European guidelines found that some dental CBCT equipment is associated with effective doses that are not as low as reasonably achievable².

You can ask why an image is needed, what question it should answer, and whether an image you already have would do.

Dental X-rays and CBCT scans use ionising radiation. According to the selection guidance, the risk is mainly that of causing cancer¹. It is highest for the young and lowest for the elderly¹.

Doses are compared as "effective dose", in microsieverts (µSv). Effective doses are calculated for a reference patient, with many uncertainties¹. They are not a measurement of your own dose. The table shows ranges from the European guidelines’ 2012 tables, based on measurements on models (phantoms)². The guidelines warn that such figures become dated very quickly².

Pregnancy. Tell the dentist before any X-ray if you are or might be pregnant. According to the selection guidance, dental X-rays, including panoramic and CBCT scans, do not need to wait until after the birth¹. It advises abdominal protection only for one rarely used view, the vertex occlusal X-ray, which points the beam at the abdomen¹. You may also choose to postpone an X-ray that is not urgent¹. The 2020 shielding report is more cautious about CBCT. It notes that the reasons for a CBCT scan are limited. For a pregnant patient, it may be more appropriate to postpone imaging until after pregnancy⁶. A 2024 systematic review concluded that dental imaging in pregnancy should not be restricted if clinically indicated⁸. It also noted that few studies have looked at this. A 2013 US obstetric committee opinion says that urgent dental treatment may be given at any time during pregnancy⁹. It adds that delaying treatment may result in more complex problems⁹.

Guidance on shielding in pregnancy differs. The 2023 US radiology recommendation advises discontinuing fetal shielding⁷ for dental imaging. The same 2013 obstetric opinion recommends shielding of the abdomen and thyroid⁹. Whether or not an X-ray is taken, the selection guidance recommends recording your agreement to that decision¹ in your notes.

Your medical and dental history. A history and an examination come before any scan. The European guidelines say a CBCT scan must not be carried out² without them. Tell the dentist about X-rays and scans you have had recently, and bring them. The selection guidance advises dentists to seek originals or copies of radiographs taken elsewhere¹ when they are relevant. It also asks them to avoid images that duplicate those taken previously¹. Mention any metal crowns, posts or fillings too: metal can blur a CBCT scan, as explained below.

An image is only as useful as its reading.

• The whole scan is read. The European guidelines call for a thorough clinical evaluation (‘radiological report’) of the entire image dataset², not only of the area being treated. Large scans often include the base of the skull. The selection guidance says these need to be viewed by a suitably qualified radiologist¹ to rule out unexpected findings.
• Who reports. For scans of the teeth and jaws, the European guidelines recommend a report by a specially trained dento-maxillofacial radiologist². Where that is impracticable, they accept an adequately trained general dental practitioner². For larger scans that include the face, or scans beyond the teeth and jaws, they recommend a dento-maxillofacial radiologist or a medical radiologist². Ask who will report your scan, and whether you will receive the written report.
• Detail. CBCT gives the advantage of three dimensions at the expense of a loss of resolution¹, compared with intraoral X-rays.
• Metal. Metal crowns, posts and fillings can cause streaks on CBCT. These artefacts¹ can look like decay or hide it, and can profoundly reduce image quality¹.
• Soft tissues. CBCT is designed for teeth and bone. Where soft tissues need assessing, the guidelines advise conventional medical CT or MR, rather than CBCT².
• Measurements. Distances measured on CBCT are comparable in accuracy with CT¹. But bone density values read from CBCT are not reproducible¹. The European guidelines add that accuracy in patients may be lower than in laboratory studies, because of small movements during the scan. They advise clinical judgement and a margin of safety² when planning implants close to important structures.
• Planning. A scan shows where the nerve canal and the sinus lie, so treatment can be planned around them. It does not remove the risks of surgery.

An image never replaces an examination. A normal-looking X-ray does not rule out every problem: the dentist reads it together with your symptoms, the examination and any tests. Any opinion given on X-rays or scans you send is preliminary until you have been examined.

Records. Every image, and the report on it, is part of your dental record. Under Turkish rules, private dental clinics record the diagnosis, the treatment and any X-rays in detail, with tooth numbers¹⁰. You can examine your file and records and get a copy¹¹. A CBCT scan is a set of data files, not a single picture. The selection guidance notes that most CBCT makers provide an export function with a simple imaging program¹, so the data can be viewed elsewhere. Ask in writing for copies of your images and reports, with their dates, and ask in which format you will receive them.

Consent. You can ask why an image is needed, what it should show and what would happen if you said no. Under Turkey’s patient rights regulation, you are told about other options, with their benefits and risks, and the possible consequences of refusing¹¹. In private dental clinics, you are asked to sign a consent form for every intervention¹⁰. The form is signed in two copies, and one copy is given to you¹¹. Ask for your copy. You can say no, or ask to stop, at any stage. That includes saying no to a particular image.

Referrals. Sometimes one dentist asks another, or a hospital, to take an image. The selection guidance says the request should carry adequate clinical information. A note such as “please take a panoramic radiograph for diagnosis” is not enough¹. For CBCT, the referring dentist must supply the results of a history and examination². A scan may raise a question beyond the teeth and jaws, or soft tissues may need assessing. You may then be referred to a hospital or an imaging centre.

Before an image is taken, you can ask:

• Why is it needed, and what question should it answer?
• Would an X-ray or scan I already have answer that question?
• Is it taken at the clinic or at an outside imaging centre?
• For a CBCT scan, how large an area will be scanned, and who will report it?
• Will I receive the written report, and in which format will I get copies of the images?
• Is it included in my written treatment plan?

Bring any earlier X-rays or scans, with the date each was taken. If they answer the dentist’s question, a repeat may be avoided. For a CBCT scan, ask for the data files with a viewing program, as well as the report. Ask for the answers, and for copies of your images and reports, in writing.