A panoramic dental X-ray, often called an OPG or Panorex, is a specialized X-ray that provides a broad, single image of the entire mouth. This wide view captures the teeth, upper and lower jaws, surrounding bone structures, temporomandibular joints, and sinuses. It is a diagnostic tool for dentists, used to assess impacted wisdom teeth, detect jaw fractures, diagnose advanced gum disease, and plan orthodontic or surgical procedures. Because X-ray technology involves radiation exposure, the question of dose is a common concern for patients.
Measuring the Radiation Dose
To understand the amount of radiation a person receives, scientists use the effective dose, measured in units called microsieverts (µSv). The sievert is the standard unit that accounts for the biological effect of radiation on human tissue. The microsievert, which is one-millionth of a sievert, is the appropriate scale for these small exposures. A modern, digital panoramic dental X-ray typically delivers an effective dose ranging from approximately 10 to 20 µSv.
The specific dose varies depending on the equipment and the patient’s size, but this range is a reduction from older film-based systems. The shift to digital radiography allows practitioners to capture high-quality images with less radiation. Digital sensors are more sensitive than traditional film, meaning the X-ray tube is active for a shorter duration to achieve a diagnostic image. This low dose is sufficient to reveal complex dental and skeletal issues that smaller, localized X-rays might miss.
Comparing the Panoramic X-Ray Dose to Everyday Exposure
Putting the 10 to 20 µSv dose into perspective requires comparing it to the radiation people encounter daily. Everyone is constantly exposed to natural background radiation (NBR) from cosmic rays, the earth, and naturally occurring radioactive elements in the environment. The average daily NBR exposure for a person is estimated to be approximately 6.7 µSv.
A single panoramic X-ray is roughly equivalent to the NBR a person receives over two to three days. This illustrates how small the exposure is compared to unavoidable natural sources. The dose from a coast-to-coast airplane flight, such as from New York to Los Angeles, provides another comparison. Due to the higher altitude reducing the atmosphere’s shielding effect, passengers receive a cosmic radiation dose of about 30 to 40 µSv.
The radiation received during that cross-country flight is often higher than the dose delivered by the dental panoramic X-ray. Comparing the panoramic X-ray to other common medical imaging procedures also demonstrates its low exposure level. A full-mouth series of smaller intraoral X-rays, which may be needed for detailed cavity detection, can deliver a total effective dose ranging from 35 to 170 µSv.
A standard chest X-ray, a routine medical procedure, often exposes a patient to around 100 µSv. The panoramic X-ray sits at the low end of the medical imaging spectrum, delivering a dose that is often less than one-tenth of a standard chest X-ray. These comparisons show that while radiation exposure should be taken seriously, the amount delivered by a panoramic scan is small relative to other unavoidable and common exposures.
Ensuring Patient Safety During Imaging
Dental professionals govern the use of all radiation-producing equipment by following the principle of ALARA, which stands for “As Low As Reasonably Achievable.” This philosophy mandates that X-rays are only taken when there is a clear diagnostic justification, meaning the medical benefit must outweigh the risk of exposure. Equipment settings are always optimized to use the lowest possible dose necessary to produce a clinically acceptable image.
Modern practices rely on high-speed digital sensors, which significantly reduce the exposure time compared to older film-based methods. Practitioners also employ rectangular collimation, which restricts the X-ray beam to the precise area of interest, minimizing scatter radiation to surrounding tissues. While lead aprons and thyroid shields were once routinely used, current professional guidance is evolving.
The American Dental Association states that routine use of thyroid collars is generally not recommended for dental imaging. This is because the primary X-ray beam in a panoramic scan is directed away from the thyroid area. The collar can also interfere with image acquisition, potentially requiring a retake that would increase the overall dose. The focus is instead on proper patient positioning and ensuring the machine’s technical factors are correctly set to maintain the lowest possible dose for a useful image.