posted: Oct. 31, 2020.
November 1st is X-ray Day! In honor of that, I thought I'd answer some questions about dental radiographs.
Q: Why did you call them radiographs instead of x-rays?
A: Good question! Most of the time, in casual conversation, we call them x-rays. The technical answer is that the x-rays are what comes out of the x-ray machine that create the image. The image that we see is called a radiograph. (But, as I said, in casual conversation, most of us just call them x-rays.)
Q: Why are dental x-rays important?
A. They help us to see areas of your mouth that we can't see just by looking in your mouth. If you've flossed your teeth, you've probably noticed that there's a spot where it's hard to get the floss between the teeth. We call that a contact point. When teeth are close together like that, we can't see in between them to see if decay has started. We also can't get our cavity detecting instruments into the contact point to see if decay has started. An x-ray helps us see that area.
Gums cover your jaw bone. The dental x-rays also let us "see" that bone so we can check for bone loss, abscesses or other pathologies in the bone. Some x-rays also let us see bones of the skull and bones that make up the tempromandibular joint (jaw joint).
Q: You said only some x-rays let you see certain bones. What are the types of dental x-rays and what are they used for?
A: There are several types of x-rays that your dentist may take:
Bitewing x-rays: usually 1-4 films though vertical bitewings may involve up to 7-8 films. The traditional method for these is to put the film or sensor into the mouth and you bite down on a tab or plastic bite block. These show both top and bottom teeth from about the gumline to the biting surface. They're most helpful for seeing cavities in between your teeth though for those with healthy bone levels around the teeth, we can sometimes see that as well. Newer panoramic type machines can also take bitewing x-rays with only a bitestick in between your front teeth. These give us a bit more information than the traditional bitewings since there is more bone repressented and we can see the ends of the roots of your teeth. (It's kind of a combination of bitewing x-rays and periapical x-rays which I'll discuss next. The panoramic machine's bitewings do not always show your front teeth, so if you're having a problem with front teeth, a different type of x-ray might be needed.)
Periapical x-rays: traditionally a film or sensor was placed in the mouth near the tooth in question and you'd bite down on a plastic holder. This type of film shows teeth from the biting surface of the tooth to the end of the root. (The end of the root is called its apex.) It is most often used to see if there is a dark circle around the apex of the root (which indicates an abscess) or to see if there is other pathology around the tooth. It can also be used to check the height of bone around a tooth. With the traditional method usually 1-3 teeth (possibly more for lower front teeth) are shown on the x-ray. Newer panoramic machines can take this type of x-ray too, again with only a bitestick between your front teeth. Depending on the settings, we may see more teeth per film than we would with the traditional method of taking them. If you have a root canal, this type of x-ray is used to check that the instruments have reached the end of the tooth root.
Full Mouth Series: This is a set of approximately 18 films or images. The full mouth series includes both bitewing and periapical views of each tooth you have. In the traditional method, films or a sensor would be inserted into your mouth and a series of images taken. They're used for the same reasons as described under each individual type of film. Periodontists like this type of x-ray because it shows them bone levels around teeth. Some offices skip areas of the mouth that don't have teeth, while others will still try to take a film there just to check for pathology.
Panoramic x-ray: the panoramic x-ray is taken in a machine where part of the machine rotates around your head to produce the image. In most cases, there is only a bite stick between your front teeth. (Many people find this more comfortable than having the film or sensors inside their mouth.) It's similar to a full mouth series in that we see all your teeth, but it also shows areas where you don't have teeth, as well as the jaw bones and the bony aspects of the tempromandibular joint area (jaw joint). It is useful for detecting pathology and seeing changes in the bone. It's not as accurate for detecting decay that is just starting (incipient decay) but larger areas of decay can often be seen on this type of x-ray. It's also helpful for checking on unerupted permanent teeth in children and unerupted wisdom teeth.
Cephalometric x-ray: this type of x-ray always reminds me of a profile (only it's showing the bones, not the facial features). Orthodontists use this view most often but there are other times it is useful as well.
Occlusal x-ray: Traditionally, this type of x-ray involved a larger film size and it was set in the mouth almost like you were biting into a sandwich. It was often used to check for unerupted front teeth. I'm not sure if digital platforms make a sensor in that size. CBCT units might be needed to render this view.
CBCT (Cone Beam): This is a specialized machine that's often used for surgical planning (dental implants, orthognatic surgeries etc.) and to detect fractures in teeth. It kind of reminds me of a medical tomography scan. The software and machine take a series of images which the software then compiles into an image, but the operator can look through the various "slices" or images that the machine took to see various levels and to see the position of anatomic structures.
I hope this helps you to understand why your dentist takes dental x-rays. If you're curious to see what a specific type of x-ray looks like, ask your dentist to show you at your next dental visit.
*Note: The information in this post article is not meant to replace the clinical judgement of your healthcare professionals.
Jennifer G. Robb, DMD is a general dentist. Her office is located at 1320 Cooper Foster Park Rd. W, Lorain, OH 44053.