What Are Bitewing X-Rays and What Do They Show?

Bitewing X-rays are a type of dental radiograph that captures the upper and lower back teeth in a single image, showing the crowns and the bone between them. They are the standard tool dentists use to find cavities between teeth and to check for early signs of bone loss from gum disease. The name comes from the tab or holder you bite down on during the exposure, which keeps the film or sensor in position. While they are just one of several dental imaging techniques, bitewings are uniquely suited to catching problems that a visual exam alone would miss.

What Bitewings Reveal About Cavities

The primary reason your dentist orders bitewing X-rays is to look for decay on the surfaces where teeth touch each other. These “interproximal” surfaces are nearly impossible to examine visually, especially on molars and premolars crammed together at the back of your mouth. On a bitewing image, healthy enamel appears as a bright, dense white layer. A cavity shows up as a darker shadow eating into that bright layer, because decayed tooth structure absorbs X-rays differently than intact enamel or dentin.

Even small cavities that haven’t caused any pain or sensitivity can appear on a bitewing. In children, adding bitewing radiographs to a clinical exam raises the detected caries rate substantially. A study of over 500 children aged three to eight found that clinical examination alone identified cavities in about 63% of them, but after bitewing X-rays were added, that figure rose to nearly 75%. Among children who appeared cavity-free based on a visual exam alone, bitewing radiographs revealed hidden lesions in almost half of them.¹ That gap between what the eye sees and what the X-ray shows is precisely why bitewings remain a routine part of dental check-ups.

Detecting a cavity early, when it is still within the enamel, gives your dentist the option of monitoring it or treating it with a small filling rather than a crown or root canal later. Bitewings can also reveal decay forming underneath an existing filling, which is practically invisible during a standard clinical exam. The image shows the interface between the filling material and the remaining tooth, making gaps or new shadows relatively easy to spot.

Spotting Bone Loss and Gum Disease

Beyond cavities, bitewing X-rays give dentists a snapshot of the bone that supports your teeth. In a healthy mouth, the bone crest sits close to the junction where the enamel meets the root surface. Research has established that a normal distance between that junction and the bone crest on a bitewing falls between roughly 0.4 and 1.9 millimeters.² When the gap is larger than that range, it signals that bone has been lost, often due to periodontal disease.

This matters because gum disease is frequently painless in its early and moderate stages. You might not notice anything is wrong until significant bone has eroded and teeth begin to loosen. By comparing bitewings taken at successive visits, your dentist can track whether bone levels are stable or gradually dropping. The images also reveal whether the bone loss is happening evenly across the jaw (horizontal loss) or in sharper, angular pockets around specific teeth, which can change the treatment approach.

Horizontal Versus Vertical Bitewings

Not all bitewings are taken the same way. The traditional approach, called a horizontal bitewing, positions the film or sensor lengthwise so it captures a wide strip of crowns and a narrow band of bone. This works well for spotting cavities and checking the fit of fillings. However, it shows only a sliver of the bone below the crowns, which limits its usefulness for periodontal assessment.

Vertical bitewings rotate the sensor 90 degrees, capturing less width but more height. A comparative study found that vertical bitewings were dramatically better at showing the level and type of bone loss. Vertical images revealed bone-loss levels in over half of sites examined, compared with under 4% for horizontal images. They also showed furcation involvement (where bone loss reaches the fork between a molar’s roots) in about 43% of sites, versus barely 1% with horizontal bitewings.³ Another clinical trial reached the same conclusion, recommending vertical bitewings for patients who have or are at risk for periodontal disease, because they outperform horizontal bitewings for detecting both bone loss and furcation issues.⁴

In practice, many dental offices default to horizontal bitewings for routine cavity checks and switch to vertical bitewings when a patient shows signs of gum disease. If your dentist has flagged bone loss or deep pockets during a probing exam, you may notice them angling the sensor differently at your next visit. That small change in orientation gives them a much more complete picture of what is happening below the gumline.

How Bitewings Compare to Periapical X-Rays

Periapical X-rays are the other common type of intraoral film. They show the entire tooth from crown to root tip, including the bone around the root apex. Bitewings, by contrast, focus on the crowns and the crestal bone but don’t reach the root tips. The two serve different purposes: periapicals are better for evaluating infections at the root end, fractures, and the shape of the roots before extractions or implants, while bitewings are better for interproximal cavities and the bone crest between teeth.

When it comes to measuring crestal bone height specifically, the two techniques don’t always agree. One study found significant differences in bone-level measurements between bitewings and periapicals for half the tooth surfaces examined, and in cases where the measurements diverged, the bitewing reading was larger 94% of the time. The researchers concluded that data from the two techniques should not be swapped interchangeably for an individual patient.⁵ A separate study looking at large-scale epidemiologic data was more lenient, finding identical readings at 82% of sites and concluding the two methods could be used interchangeably for population-level research, even though individual-level differences existed.⁶

The practical takeaway is that your dentist chooses between these based on what they need to see. If the question is “is there a cavity hiding between these molars,” a bitewing is the first choice. If the question is “what’s happening at the tip of this root,” a periapical is the right tool. They complement each other rather than compete.

Radiation Dose and How Often You Need Them

One of the advantages of bitewing X-rays is their low radiation exposure. A study measuring dose in children and adolescents found the effective dose from a single dental or bitewing radiograph averaged about 0.77 microsieverts.⁷ To put that in context, you receive roughly 8 microsieverts of background radiation just from living on Earth for a single day. A standard set of four bitewing images adds up to a fraction of your daily natural exposure.

Digital sensors have reduced the dose even further compared with traditional film, because they require less radiation to produce a usable image. A comparison study found no significant difference in diagnostic accuracy between digital and conventional film bitewings for detecting cavities between teeth, meaning the move to digital sensors maintained image quality while cutting radiation.⁸

How often you need bitewings depends on your risk level. Adults with no recent cavities and healthy gums may only need them every two to three years. If you have a history of frequent decay, active gum disease, or are undergoing orthodontic treatment, your dentist might recommend them annually or even more often. The goal is always to balance the diagnostic benefit against keeping cumulative radiation as low as reasonably achievable. For most people, the tiny dose from bitewings is far outweighed by the value of catching a cavity or bone loss early.

Bitewings in Children

Children benefit enormously from bitewing X-rays, particularly because baby teeth have thinner enamel and cavities can progress quickly. As noted earlier, a clinical exam alone can miss a large proportion of cavities in young children. But taking bitewings in a small mouth comes with practical challenges. Some children struggle with the gag reflex triggered by the sensor or film holder, and very young or anxious patients may not be able to hold still long enough for a clear image.

For children who can’t tolerate a standard intraoral bitewing, extraoral bitewing techniques offer an alternative. The sensor is placed outside the cheek rather than inside the mouth, which eliminates the gagging problem. Research on extraoral bitewings in primary molars has confirmed that they can serve as a viable option for uncooperative or intolerant pediatric patients.⁹ The tradeoff is somewhat lower image resolution, but for a child who simply cannot sit through an intraoral exposure, it is far better than no image at all.

Pediatric dentists typically begin recommending bitewings once the back baby teeth are touching each other, which usually happens around age four or five. The American Academy of Pediatric Dentistry and similar bodies suggest the frequency be tailored to each child’s risk, with cavity-prone children getting them more often.

When AI Reads Your Bitewing

Reading bitewing X-rays has always been a skill that improves with experience, and even seasoned dentists can disagree on borderline findings. Dental artificial intelligence is now entering the picture, with deep learning models trained on thousands of annotated bitewing images to flag cavities and bone loss automatically. A systematic review of AI caries detection found that convolutional neural networks show strong accuracy, sensitivity, and specificity, though results still vary considerably between studies.¹⁰

Individual AI models are posting impressive numbers. One model trained on over 550 bitewing images achieved a precision of about 96% for enamel cavities and 80% for deeper dentin cavities, with an overall precision around 85%.¹¹ Another study directly compared an AI algorithm against dentists with varying levels of experience and found the AI had higher precision than human readers, particularly in avoiding false positives caused by common radiographic artifacts like cervical burnout, which is a dark shadow near the gumline that can mimic a cavity.¹²

AI is also being applied to the bone-loss side of bitewing interpretation. A preliminary study using deep learning to detect alveolar bone loss on bitewings reported a sensitivity of 65% and specificity of 90%, with an overall accuracy of 76%.¹³ Another research group developed a model that automatically locates the key anatomical landmarks on a bitewing and measures the distance between them to estimate bone loss, then compared its measurements against a multi-expert consensus.¹⁴ These tools are not replacing dentists yet. They function more like a second set of eyes that can highlight areas a human reader might want to look at twice, and the technology is still maturing.

Near-Infrared Light as a Radiation-Free Alternative

For patients concerned about radiation, or for situations where bitewings are impractical, near-infrared light technology is emerging as a complement or potential substitute. These devices shine harmless infrared light through a tooth and capture the light that passes through or reflects back. Healthy enamel transmits the light well, while a cavity scatters it, creating a visible contrast on a screen.

A meta-analysis pooling data from six studies on near-infrared light transillumination found it had good overall accuracy for detecting cavities between teeth in permanent teeth, correctly classifying about 92% of surfaces examined.¹⁵ A large multicenter study conducted in private practices compared reflected near-infrared light against bitewing radiography and found that the infrared device actually detected more than twice as many carious lesions, mainly because it picked up very early enamel-only lesions that don’t yet show on an X-ray.¹⁶

That sounds like a clear win, but the picture is more complicated. A systematic review of near-infrared technology found that its specificity, meaning its ability to correctly identify surfaces that are not decayed, varied wildly across studies, from as high as 94% to as low as 20%.¹⁷ A device that detects many real cavities but also flags many healthy spots as suspicious can lead to overtreatment, which is a real concern. The technology also cannot assess bone levels or show the structures below the gumline that bitewings capture. For children with primary teeth, one study found that near-infrared imaging added no extra diagnostic information beyond a clinical exam for initial enamel-only lesions, suggesting bitewing radiographs still hold their ground when deeper or more advanced lesions are the concern.¹⁸

Right now, near-infrared devices are best thought of as a supplement rather than a replacement. They are especially useful for screening and monitoring early lesions that haven’t progressed far enough to need a filling, or for patients who need to minimize X-ray exposure, like pregnant women. But when your dentist needs to see bone support, check underneath a filling, or get a comprehensive view of everything happening between your back teeth, the bitewing X-ray remains the workhorse that nothing else has fully displaced.