Dental radiographs, commonly known as X-rays, are indispensable tools used by dentists to gather diagnostic information invisible during a routine oral examination. These images allow practitioners to look beneath the surface of the teeth and gums to assess the health of supporting structures. Since no single image can capture the entire necessary spectrum of information, different types of radiographs are employed to focus on specific areas of the mouth. Understanding the purpose of each image type clarifies why a dentist may request one view over another during a visit.
The Scope of Bitewing Radiographs
The bitewing (BW) radiograph is primarily a screening tool designed to capture a focused view of the crowns of the upper and lower back teeth on one side of the mouth simultaneously. The name comes from the small tab or wing the patient bites down on to position the film or digital sensor. This specific positioning is engineered to show the tight contact points between adjacent teeth, which are areas where decay often begins but is hidden from direct view.
The main function of the bitewing image is the early detection of interproximal decay. Because the X-ray beam passes directly through these surfaces, even small lesions appear as distinct shadows before they become visible to the naked eye or cause symptoms. These images are typically taken during routine checkups, often once a year, to monitor changes in the enamel and underlying dentin.
A secondary application of bitewing radiographs involves assessing the alveolar bone. The image clearly displays the height of the marginal bone crest, which is the bone supporting the teeth right below the gum line. Changes in this bone level provide evidence for diagnosing early to moderate periodontal, or gum, disease. By monitoring this height over time, dentists can track the progression or stabilization of bone loss.
The Focus of Periapical Radiographs
The periapical (PA) radiograph, by contrast, is a highly detailed diagnostic tool that focuses on the entire length of one or two teeth. The PA image is designed to capture the tooth from its crown all the way down to the root tip and the surrounding bone structure. Its primary function is to evaluate the health of the internal pulp tissue, which contains the nerve and blood vessels.
When a tooth is symptomatic or a deeper problem is suspected, the PA image is used to check the periapical area for signs of infection or inflammation. Pathologies like dental abscesses or cysts at the root tip appear on the radiograph as dark, translucent areas in the bone. This view is also indispensable for assessing the success of prior treatments, such as tracking the healing of a tooth after root canal therapy.
Periapical radiographs are also used to diagnose trauma, such as suspected root fractures, or to evaluate advanced stages of periodontal disease where significant bone loss has occurred. The PA image provides a vertical, comprehensive view of the entire tooth structure. This detailed scope makes it the standard for evaluating the full anatomy of a tooth before complex procedures like extractions or endodontic treatment.
Key Differences in Technique and Clinical Use
The most significant difference between the two types of radiographs lies in their field of view and intended diagnostic purpose. The bitewing is a horizontally oriented screening image, capturing multiple posterior crowns and the upper portion of the alveolar bone, making it excellent for surveying surface-level decay and early bone changes. The periapical view is a localized image, vertically focused on one or two teeth to capture the entire root and the bone at the apex, serving as a dedicated diagnostic tool for deep internal pathology.
From a patient’s perspective, the technique for taking each image differs noticeably. For a bitewing, the patient simply bites down on a small wing or tab, which positions the sensor to capture the crowns of the opposing arches simultaneously. The periapical technique often requires the use of a more involved aiming device to ensure the X-ray beam is perfectly parallel to the tooth’s long axis, capturing the entire root without distortion or foreshortening.
The clinical choice between the two is based entirely on the dentist’s goal; the bitewing is employed for routine surveillance and preventative care, while the periapical image is reserved for investigating specific symptoms or known issues. Neither image can fully replace the other, as the bitewing is unsuitable for assessing the root tip, and the periapical image does not efficiently capture the interproximal surfaces of multiple teeth. For a comprehensive view of oral health, both specialized images are necessary.