Different dental X-rays answer different questions. A bitewing looks for decay hiding between the back teeth, a periapical shows a single tooth all the way to the tip of its root, an OPG gives one wide picture of every tooth and both jaws, and a 3D cone beam scan shows the bone in depth when treatment such as an implant needs to be planned.
Which one you have depends on what your dentist needs to see. Here is what each view shows and when it tends to be used.
Much of a tooth cannot be seen in the mirror
Roots sit inside the jaw, the surfaces where teeth touch are hidden from view, and early decay often starts under intact enamel. X-rays let a dentist see decay between teeth, infection around a root, bone levels around the teeth and teeth that have not yet come through. Problems found this way are usually simpler to treat than ones that wait until they hurt.
Bitewings check between the back teeth
For a bitewing, a small sensor sits inside your mouth and you close gently on a tab or holder. The image shows the upper and lower back teeth on one side together, from the biting surfaces down to the bone level. Bitewings are the most common check-up X-ray because they show decay between teeth and around the edges of fillings and crowns, which is very hard to spot by eye. They also give a useful view of bone height in early gum disease.
Periapicals show one tooth from top to root tip
A periapical image covers one or two teeth in full, including the roots and the bone around them. It is usually the X-ray taken when a particular tooth is aching, swollen or has been knocked. It can show infection at the root tip, a cracked or broken root, the progress of a root canal and how a tooth or implant is sitting in the bone.
An OPG shows the whole mouth in one picture
For a panoramic X-ray, or OPG, you stand or sit in a machine that moves around your head for a few seconds. The result is a single wide image of all the teeth, both jaws, the jaw joints and the lower part of the sinuses. It is useful for looking at wisdom teeth, checking how children's adult teeth are developing, planning orthodontic treatment, and getting an overview before larger treatment. Because it shows less fine detail than an intraoral X-ray, it is used alongside bitewings and periapicals rather than instead of them.
3D cone beam scans are kept for planning and complex questions
A cone beam CT (CBCT) scan builds a three-dimensional image of the teeth, bone and nearby structures. It is not a routine check-up image. It is mainly used when depth matters, such as measuring bone before an implant, locating the nerve near a wisdom tooth or looking more closely at a complicated root problem. The dose is higher than a standard dental X-ray, so it is taken only when the extra information will change the plan.
How the four compare
| Type | What it shows | Often used for |
|---|---|---|
| Bitewing | Upper and lower back teeth on one side, crowns to bone level | Decay between teeth, checking fillings, bone levels |
| Periapical | One or two whole teeth including the roots | Toothache, infection, root canal, injury |
| Panoramic (OPG) | All teeth, both jaws, jaw joints | Wisdom teeth, orthodontic planning, overview |
| Cone beam CT | 3D view of teeth and bone | Implant planning, nerve position, complex cases |
The radiation doses are very small
A dental imaging brochure on the Australian Dental Association's patient website, teeth.org.au, lists dental X-rays other than cone beam scans at 10 microsieverts or less, and a cone beam scan at less than 80 microsieverts. For comparison, the same brochure lists 4 microsieverts for simply living one day, 16 for a flight from Darwin to Perth and 20 for a medical chest X-ray. It also notes that lead aprons are not usually required in modern dentistry, and at Lumi Dental we do not use them.
Dentists still take X-rays only when they are likely to change or confirm your care, and use the lowest dose that gives a useful picture. Our guides to how safe dental X-rays are and how often they are needed and X-ray safety for children go into more detail.
Questions about dental X-rays
Which X-ray finds cavities?
Bitewings are the main tool for finding decay between the back teeth. A periapical can give a closer look at one tooth.
Will I have an OPG or 3D scan at every visit?
No. These are taken when a wider or 3D view is needed, for example for wisdom teeth or implant planning, not as routine check-up images.
How often will I need bitewings?
There is no fixed schedule. People with a higher risk of decay or active gum disease may need them more often than those with healthy teeth and gums.
Imaging at Lumi
At Lumi Dental we take digital X-rays and have an Orthophos 3D X-ray unit for OPGs and 3D scans when they are needed. To see what a routine visit involves, read our check-up guide, or book through our current offers.
This article is general information and not a substitute for personal dental advice. Please see a dentist for care tailored to your situation.
