Understanding Dental X-rays

Dental x-rays provide a treasure trove of information to the dentist. Also called radiographs, they can show tooth decay, infection, cavities, impacted teeth, misaligned jaws, and much more. X-ray images are relatively straightforward – once you understand what you are looking at. Of course, it takes a qualified dental professional to identify problem areas. In this article we look at:

How does dental radiography work?
What are the different types of dental X-rays?
Reading a dental X-ray
Importance of dental X-rays

How does dental radiography work?

Radiography is the process of producing an image for medical examination on a sensitive film or plate using x-rays or other forms of radiation. In dental radiography, an x-ray tube is used to project beams (radiation) onto the patient’s mouth. X-rays pass through the mouth and come out the other side harmlessly (attenuation). On the other side is a receptor that captures the x-rays and creates an image. Receptors can be vinyl film packets or digital sensors.

X-rays do not pass through skin and tissue evenly. Thicker and heavier masses such as teeth will block x-rays more than other tissues such as skin.

What are the different types of dental X-rays?

There are two main types of dental x-rays. Intraoral x-rays are taken with the receptor inside the patient’s mouth. These are good for evaluating teeth and surrounding tissue. Extraoral x-rays are taken with the receptor outside the patient’s mouth. These are good for getting the big picture of the teeth and assessing the skull and the jaws.

Intraoral x-rays

Bitewing (shows cavities starting to develop and bone loss due to gum disease)
Periapical (show the root of teeth in detail)
Occlusal (used to look for tooth or bone fractures, tooth eruption)

Extraoral x-rays

Panoramic (frontal view of all teeth; “big picture” view of teeth)
Cephalometric (evaluate the relationship of upper and lower jaws to each other and cranial base; good for tracking growth – important in orthodontics)

Digital dental x-rays are a more recent technology. Instead of using a film that must be processed in a dark room, a digital receptor sends the image directly to the computer. It can then be viewed, shared, or printed out.

There are a few benefits of using digital dental x-rays:

There is lesser exposure to x-rays
Images are available a few seconds after being taken

Reading a dental x-ray

A dental x-ray works on the principle that harder more mineralized tissues will block more of the x-ray radiation. Due to this, hard tissues like the enamel and dentin will appear light in color. Spaces between teeth and tooth pulp appear dark because they are non-mineralized.

One easy way to understand it is the harder something is the lighter it appears. The softer something is the darker it appears.

What do cavities look like on x-rays?

Cavities appear as a dark spot in a tooth. Cavities start in the enamel, which shows as the lightest color in the x-ray. It will travel inwards into the dentin, which is softer than enamel and appears darker too. Dental x-rays also show cavities between two teeth, something that would not be visible to the naked eye.

Importance of dental x-rays

Dental radiography is an indispensable diagnostic tool for many reasons. They allow the dentist to:

See inside and between the teeth
See under the gums and locate the tooth root
Check for cavities
Assess the extent of tooth decay
Diagnose cysts and abscesses
See impacted teeth
Detect bone loss and periodontal disease

Do dental x-rays show infection?

Yes, x-rays can show infection and abscesses even before the person feels obvious symptoms.

What does a dark spot on a dental x-ray mean?

A dark spot in an x-ray can mean the presence of a cavity. It is a sign that bacteria have attacked the enamel and are entering the dentin. This decay must be addressed as soon as possible.

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