How-to · Exam prep
Periapical vs. bitewing X-rays: a beginner's guide
Radiology is one of the most-used skills a Texas dental assistant has — and these two intraoral films are the bread and butter. If you can explain what a bitewing shows, what a periapical shows, and why the doctor asked for one instead of the other, you're ahead of most beginners.
The one-sentence difference
A bitewing shows the crowns of the upper and lower back teeth in one image — great for finding decay between teeth. A periapical shows one area from the crown all the way to the root tip and the bone around it — great for seeing what's happening under the surface.
Compare them (tap each film)
Why the bitewing is the everyday workhorse
The name comes from the little tab or holder the patient bites down on, which positions the film so both arches show at once. Dentists rely on bitewings at routine checkups because decay between back teeth — where the toothbrush can't reach and the eye can't see — shows up on a bitewing before it becomes a bigger problem. Bitewings also help the doctor watch the crest of the bone between teeth, an early indicator in gum disease.
"Let's get four bitewings" is one of the most common radiology requests in a general office — typically one horizontal film on each side, upper and lower premolar and molar areas. It becomes muscle memory fast.
When the periapical earns its keep
When a patient comes in pointing at one tooth and saying "this one hurts," the doctor usually wants a periapical. Because a PA captures the entire tooth plus the surrounding bone and the area around the root tip (the apex — that's the "api" in periapical), it's the film for suspected abscesses, root fractures, checking a tooth before an extraction or root canal, and following up on healing afterward.
How you'll learn to take them
Reading about films is one thing; positioning a sensor in a real mouth is another. In training you practice both projections repeatedly — angulation, sensor placement, patient comfort, retakes and how to avoid them — until they're routine. Radiology training is part of the in-person program's core curriculum, and it's one of the three courses Texas requires for RDA registration, alongside jurisprudence and infection control.
Radiology certification requirements, fees, and exam specifics come from the state — always verify current details at tsbde.texas.gov. Our guide to getting radiology certified in Texas walks the path in plain English.
Quick self-check
Cover the answers and try it: Which film for a routine checkup looking for decay between molars? (Bitewing.) Which film when tooth #19 aches and the doctor suspects an abscess? (Periapical.) Which film shows the root apex? (Periapical.) Which film shows both arches at once? (Bitewing.) If you got all four, you're ready for more — the free practice exam has a whole radiology section.
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Apply now →Keep reading: Pass the radiography portion of the RDA exam · Radiology certification in Texas · Dental instruments 101