Orthodontic X-Rays and Radiation UK — What You Need to Know

Why orthodontic X-rays are required

X-rays form part of the orthodontic diagnostic record because they reveal information that cannot be obtained from a clinical examination alone. A panoramic X-ray shows the position, angulation, and developmental stage of all teeth — including unerupted, impacted, and wisdom teeth — as well as the roots, bone levels, and signs of pathology such as cysts. A lateral cephalogram shows the skeletal relationship of the upper and lower jaws and allows precise measurement of jaw angles, which informs treatment planning for both orthodontics and orthognathic surgery. X-rays also identify whether teeth are present, how many roots they have, and whether root resorption has occurred previously. The decision to take any X-ray must be clinically justified on an individual basis.

OPG (panoramic X-ray) — radiation dose and what it shows

The OPG, or orthopantomogram, is a panoramic X-ray that sweeps around the jaw to produce a single flattened image of all upper and lower teeth, the jaws, and the TMJ. It is the most commonly requested orthodontic X-ray. The effective radiation dose from an OPG is approximately 14 to 24 microsieverts (µSv) — roughly equivalent to one to two days of background radiation from natural sources. For context, a chest X-ray delivers around 14 µSv and a transatlantic flight delivers around 80 µSv. The OPG is considered a low-dose examination that is well justified for orthodontic assessment. It does not provide a reliable measure of tooth inclination in three dimensions, which is why it is supplemented by other records in complex cases.

Lateral cephalogram — dose and clinical use

The lateral cephalogram is a standardised side-profile X-ray of the skull and jaw, taken with the patient in a reproducible position using a cephalostat. It allows the clinician to trace and measure skeletal and dental angles — including the ANB angle (upper to lower jaw relationship), the incisor inclination, and vertical facial proportions. The radiation dose is approximately 3 to 6 µSv — lower than the OPG. Cephalometric analysis is particularly important in patients with skeletal discrepancies, Class II or Class III malocclusion, and where orthognathic surgery is being considered. It may also be taken at mid-treatment or post-treatment to evaluate changes. Not every patient requires a lateral cephalogram; its use should be clinically justified for the individual.

CBCT — when it is justified versus OPG

Cone beam computed tomography (CBCT) produces a three-dimensional image of the jaws, teeth, and surrounding structures. It is used in orthodontics when conventional 2D imaging cannot provide sufficient information — typically for impacted teeth (especially canines), assessment of root proximity before tooth movement, evaluation of bony defects, and surgical planning. The radiation dose from a CBCT varies significantly depending on field of view and scan protocol, but a small-field CBCT delivers approximately 70 to 400 µSv — several times higher than an OPG. Because of this, CBCT should only be used when conventional X-rays have been shown to be inadequate and when the additional diagnostic information will change clinical management. The FGDP and Public Health England guidelines state clearly that CBCT is not a first-line investigation and must be justified on a case-by-case basis.

ALARA principle and UK regulatory guidance

The ALARA principle — As Low As Reasonably Achievable — governs radiation use in UK dental practice. Under the Ionising Radiation (Medical Exposure) Regulations 2017 (IR(ME)R), every X-ray must be individually justified by a referrer and authorised by a practitioner, and the dose used must be the minimum necessary to obtain diagnostic quality images. Practices must have documented protocols for each type of X-ray, use digital detectors where possible (which significantly reduce dose compared to film), and carry out regular equipment quality assurance. Patients should be told why an X-ray is being taken. Routine X-rays taken at fixed intervals without individual clinical justification do not comply with ALARA or IR(ME)R requirements.

Patient rights — can you decline an X-ray, and pregnancy considerations

You have the right to refuse any X-ray, and a clinician must respect your decision. However, you should be aware that declining a clinically justified X-ray may limit the clinician's ability to plan treatment safely — for example, not knowing the position of an impacted tooth carries its own risk. Discuss your concerns and ask for the justification for each X-ray before agreeing. For pregnant patients, dental X-rays — including OPGs — can be taken if clinically necessary, as the abdomen is remote from the primary beam and the radiation dose is very low. A lead apron is not routinely required for dental X-rays under current UK guidance but may be offered. Elective orthodontic X-rays are typically deferred until after the first trimester where possible, though in most cases the risk is considered negligible.

Useful related pages

This guide is for general information only. It is not a diagnosis, treatment plan, or substitute for advice from a registered dentist or orthodontist.