Dental X-rays

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Dental X-rays are an integral and essential part of dental diagnosis and treatment planning. No matter how experienced the dentist is, X-rays are essential.

For example, X-rays are used to:

  • Diagnose decay or rotten teeth
  • Determine degrees of bone loss associated with gum disease (periodontal disease)
  • Examine root lengths and infection in the jaw bone during endodontics (root canal treatment)

How dental X-ray systems work
Most X-ray systems have been digitalised, which means X-ray sensors instead of X-ray film are now used in most modern dental pratices. The sensors instantly produce images of the structures in and around the mouth without having to develop, fix and process X-ray film – a time-consuming, tedious process.

The digital sensors are exposed very briefly by the X-ray machine or camera, resulting in an instantaneous image on a PC monitor. This image can be manipulated in a number of ways, using an X-ray software programme.

Bite-wing and periapical X-rays
When you visit your dentist, he or she is most likely to take a bite-wing (so-called because you bite down on a wing-shaped device that holds the film in place) and/or periapical X-ray (which shows the entire tooth, from the crown to the bone that supports it). These X-rays give your dentist a small view of a particular part of the mouth.

For these intra-oral X-rays to be taken, you’ll have to sit or lie down in your dentist’s chair. The dentist will ensure that the system’s small sensors are lined up in your mouth, and the camera will be placed in such a way that there’s very little room for error. The sensors vary in size, but are usually around 2cm x 4cm, and are comfortably tolerated by most people.

For safety reasons, your dentist will cover you with a lead-lined apron, taking care to cover your thyroid glands, ovaries and testes in particular. Both the dentist and dental assistant will leave the room while the X-ray is being taken. It’s a straightforward process that only takes a few minutes to complete.

Other types of X-rays
More advanced X-ray units are also widely used in dental practices. These include:

  • Dental panoramic (panorex) X-ray machines, which give a two-dimensional, full view of the upper and lower jaws, teeth, joints and the surrounding structures and tissues (e.g. the nasal sinuses).
  • Lateral cephalometric (ceph) X-ray machines, which are mostly used in orthodontic treatment planning.

The newest advance in dental X-rays is three-dimensional dental cone beam computed tomography (CT), which shows much more than regular two-dimensional X-rays.

These X-rays are, for example, used in root canal therapy. They’re also used to scan bone density, which is an essential step in the placement of dental implants. Dental cone CT scans also give surgeons a clear understanding of structures at risk during surgeries like wisdom tooth extraction.

Dental panoramic, lateral ceph and cone beam CT scan machines must all be attached to a wall. This means that, should you have to get one of these types of X-rays done, you won’t be seated in the dental chair. Instead, you’ll have to stand at the X-ray machine – once again covered with a lead-lined, protective apron.

Again, the dentist and assistant will leave the room while the X-ray is being taken.

What should you know about safety?
Dental X-rays emit ionising radiation, which has been linked to meningioma – a slow-growing, usually non-malignant type of brain tumour that arises from the meninges of the brain and spinal cord.

Although risk levels are low, dental practitioners take care to avoid over-exposure.

When it comes to your safety, it’s important to take note of the following:

  • X-rays are unlikely to cause harm to your unborn baby, yet dentists prefer to err on the side of caution. Expectant mothers should avoid dental X-rays, particularly during the first trimester of pregnancy. Even if you’re just trying to conceive, you should avoid X-rays – unless your life is in danger, of course. Remember to tell your dentist if you’re trying to fall pregnant or are already pregnant.
  • If you’re visiting the dentist as a family, you shouldn’t stay in the room while other family members are being X-rayed.

Note that all dental X-ray machines undergo stringent safety testing as per South African law. They’re tested by Gendentsa – the inspection company for all X-ray units throughout South Africa –and must be certified by the Department of Health. These units must undergo testing every three years.

How often should you get a dental X-ray?
Dental X-rays are usually taken every six months, during your biannual dental check-up, unless complex treatment is required during which several X-rays may have to be taken.

The larger, more powerful machines are used less often, but can be used every 12-18 months for diagnostic purposes. If your dentist is tracking the growth of a tumour or cyst, X-rays may have to be used more frequently.

Common sense should be applied when it comes to opting for dental X-rays. If you’re at risk of dental disease, you should be X-rayed regularly. If your risk is low, you should be X-rayed less often. It’s important to talk to your dentist about the frequency that’s best for you.

Written by dentist Dr Lance Videtzky of City Dental Care, Cape Town. (B.D.S.) Rand. February 2019.

Read more:

- Wisdom teeth

- Root canal treatment

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