# Dental X-rays and 3D scans

> Why dentists take X-rays, what bitewing, periapical, panoramic and cone-beam CT images show, how the radiation dose is kept low, and what to know in pregnancy.

Source: https://www.nazemalioussef.com/en/patient-guides/dental-x-rays/  
Updated: 2026-09-28

Patient guide

An X-ray shows what an examination of the mouth cannot: decay between the teeth, the bone around the roots and teeth that are still inside the jaw. Dentists take one when the answer will change what happens next.

From the professional website of Dr Nazem Al Ioussef Published 27 September 2026 Last reviewed 27 September 2026

## What an X-ray can show

Enamel, dentine and bone block X-rays to different degrees, so the image shows structures that are hidden in the mouth. Dentists use X-rays to look for:

- decay between the teeth, under fillings or beneath the enamel;
- the level of the bone around the teeth, which drops in gum disease;
- infection at the tip of a root;
- wisdom teeth, and in children the adult teeth still developing in the jaw;
- the effects of an injury to the teeth or jaw;
- the bone and nearby structures before an extraction, root canal treatment or an implant.

## The different kinds of image

### What each kind of dental X-ray covers

1. **Bitewing.** It shows the crowns of the upper and lower back teeth together and is used to find decay between the teeth.
2. **Periapical.** It shows one or two whole teeth, from the crown down to the root tips.
3. **Panoramic and cone-beam CT.** One shows both jaws whole; the other gives a three-dimensional view used to plan implants and assess wisdom teeth.

Simplified drawing, not to scale.

- **Bitewing.** A small sensor sits inside the mouth while you bite on a tab. It shows the crowns of the upper and lower back teeth and the bone between them, and is the usual way to find decay between the teeth.
- **Periapical.** Also taken with a sensor inside the mouth, it shows one or two teeth in full, down to the root tips. It is used for toothache, suspected infection and root canal treatment.
- **Panoramic (OPG).** The machine moves around the head and produces one flat image of both jaws and all the teeth. It is often used to assess wisdom teeth and the jaws as a whole, though it shows less fine detail than an X-ray taken inside the mouth.
- **Cone-beam CT (CBCT).** The scanner rotates around the head and builds a three-dimensional image. It is used, for example, to plan implants, to see how close a wisdom tooth is to the nerve in the lower jaw, and for some root canal problems and injuries.

## Radiation, and how it is kept low

Dental X-rays use low doses of radiation, and digital sensors have lowered them further. A cone-beam CT usually gives a lower dose than a medical CT scan but a higher one than a standard dental X-ray. Because every exposure carries some risk, dentists follow two principles: an X-ray is taken only when it is needed to diagnose or treat a problem, and the settings are chosen to keep the dose as low as reasonably achievable. Children are more sensitive to radiation than adults, so extra care is taken with them.

RadiologyInfo.org, the patient website of the Radiological Society of North America and the American College of Radiology, gives these approximate effective doses and compares each with natural background radiation, which everyone receives from the environment:

- dental X-ray: 0.005 mSv, comparable to 1 day of natural background radiation;
- panoramic X-ray: 0.025 mSv, comparable to 3 days;
- cone-beam CT: 0.18 mSv, comparable to 22 days.

These are typical figures. The actual dose depends on the machine and on how much of the head is scanned.

## How often X-rays are taken

There is no fixed schedule. The American Dental Association advises that X-rays are taken only when the dentist believes they will provide information needed for diagnosis or treatment. How often that is depends on a person's age, the health of their teeth and gums, their risk of disease and any symptoms. People at higher risk of decay or gum disease may need them more often, and children sometimes do too, because their teeth and jaws are still developing.

A new dentist may want a set of images as a starting point. If another dentist has taken recent X-rays, copies can often be sent across, which can avoid taking them again.

## Pregnancy

Tell the dentist if you are pregnant or might be. Dental X-rays are aimed at the mouth, well away from the abdomen, but X-rays that can wait are usually postponed, particularly in early pregnancy. When an X-ray is needed for your care, for example for pain or infection, it can still be taken.

## What to expect

1. **Before.** You may be asked to remove glasses, earrings, hairpins, hearing aids and any removable denture or brace, as metal can show on the image.
2. **Bitewing and periapical.** The sensor is placed in the mouth and you bite gently to hold it. Keep still for a moment while the image is taken. If the sensor makes you gag, tell the dental team; changing its position often helps.
3. **Panoramic.** You stand or sit with your chin on a rest and bite on a small block, and the machine turns around your head. Keep as still as you can.
4. **Cone-beam CT.** You sit, stand or lie still while the scanner rotates around your head. The scan itself takes seconds, not minutes.

A cone-beam CT is often part of planning [dental implants](https://www.nazemalioussef.com/en/clinical-interests/dental-implants/), and a panoramic X-ray or a scan is usually taken before removing [impacted wisdom teeth](https://www.nazemalioussef.com/en/clinical-interests/wisdom-teeth/).

## Questions patients ask

**Are dental X-rays harmful?**

Dental X-rays use low doses of radiation, and the American Dental Association describes the risk of harmful effects as very small. Because any dose carries some risk, dentists take X-rays only when the information will help with diagnosis or treatment, and keep the dose as low as reasonably achievable.

**Why can't the dentist see the problem without an X-ray?**

Much of a tooth is hidden. Decay often starts where two teeth touch or under an old filling, and infection at a root tip, bone loss from gum disease and teeth still inside the jaw cannot be seen in the mouth at all.

**I am pregnant. Can I have a dental X-ray?**

Tell the dentist if you are, or might be, pregnant. X-rays that can wait are usually postponed, particularly in early pregnancy, and an X-ray is taken when it is needed for your care. The beam is aimed at the mouth, not the abdomen.

**Do I need a lead apron?**

The American Dental Association now advises that abdominal and thyroid shielding is not needed for dental X-rays, for patients of any age or health status, including pregnancy, because it can block the beam and lead to repeat X-rays. Some practices still use it where local rules require.

**What is the difference between a panoramic X-ray and a cone-beam CT?**

A panoramic X-ray is a single flat image of both jaws and all the teeth. A cone-beam CT builds a three-dimensional picture that can be viewed in slices from any direction. It shows more, but usually involves a higher dose, so it is kept for questions a flat image cannot answer.

## What this page rests on

This guide rests on patient information from the American Dental Association, the Oral Health Foundation and RadiologyInfo.org (the Radiological Society of North America and the American College of Radiology), and on the US Food and Drug Administration's guidance on cone-beam CT. The radiation figures are quoted from RadiologyInfo.org. Which images a particular person needs is decided by the dentist after an examination.

General health information, not a diagnosis or a treatment recommendation for any individual.

### Sources

1. American Dental Association, MouthHealthy — [X-rays](https://www.mouthhealthy.org/all-topics-a-z/x-rays)
2. Oral Health Foundation — [X-rays](https://www.dentalhealth.org/x-rays)
3. US Food and Drug Administration (FDA) — [Dental cone-beam computed tomography](https://www.fda.gov/radiation-emitting-products/medical-x-ray-imaging/dental-cone-beam-computed-tomography)
4. RadiologyInfo.org (RSNA and ACR) — [Radiation dose](https://www.radiologyinfo.org/en/info/safety-xray)
5. RadiologyInfo.org (RSNA and ACR) — [Dental cone beam CT](https://www.radiologyinfo.org/en/info/dentalconect)

## Related pages

- [Children's teethFrom a baby's first tooth to a first dental visit: teething, sugar and help with brushing.](https://www.nazemalioussef.com/en/patient-guides/childrens-teeth/)
- [Bad breathWhere bad breath usually comes from, what helps, and when it needs a dentist.](https://www.nazemalioussef.com/en/patient-guides/bad-breath/)
- [Teeth grindingGrinding and clenching, often at night: the signs, the causes and what can help.](https://www.nazemalioussef.com/en/patient-guides/teeth-grinding/)