It’s not uncommon for dental patients to require multiple X-rays over a short period of time in order to properly diagnose and develop a thorough treatment plan for certain oral health issues.
For example, a patient with generalized dental pain or symptoms indicative of a potentially serious condition may need several periapical X-rays on specific teeth along with bitewing films and a panoramic scan within a single appointment or a few appointments spaced closely together.
While this focused radiographic investigation is often clinically warranted to fully evaluate the patient’s case, it understandably raises questions around safe frequency limits for dental X-rays, especially when done all within the span of a month or two.
Patients want to ensure they are not exposing themselves to excessive levels of radiation that could negatively impact their health. Dentists share the same goal of optimizing the clinical benefits of dental radiography while minimizing any potential risks.
Guidance on safe yet adequate frequency limits for common dental X-ray types over a short time frame enables dentists to hone in on the source of a dental issue while also reassuring patients. Recommendations take into account average radiation exposure from different dental radiographs along with up-to-date evidence on safe monthly exposure limits and effects.
With thoughtful guidelines, patients can get the X-rays needed in the short run while maintaining overall safety.
Average Radiation Exposure from Dental X-rays
- A bitewing set consisting of four X-rays exposes the patient to 22 to 51 microSv (microsievert).
- A panoramic examination results in exposures of about 5 to 25 microSv.
- Cone-beam X-rays result in a wide variety of exposure ranging from a little as 20 microSv to as much as 700 microSv depending on image size and the brand of cone-beam machine used.
To understand what this means, this can be compared with the average amount of background radiation (radiation occurring in the environment) a person is exposed to in a year. That average, worldwide, is 2400 microSv per year.
Recommended Limits for Monthly Dental X-rays
Professional organizations suggest the following evidence-based safety limits for dental X-rays within a 1 month timeframe:
- Bitewing: No more than 4 films (0.02 mSv)
- Periapical: No more than 20 images (0.2 mSv)
- Panoramic: No more than 1 image (0.015 mSv)
- CBCT: No more than 1 scan (0.3 mSv)
This adheres to the ALARA (As Low as Reasonably Achievable) principle for minimizing radiation exposure.
ALARA Principle
The ALARA principle is an important concept in dentistry and radiology to minimize radiation exposure from diagnostic imaging as much as possible. This applies to all ionizing radiation sources in dentistry including CT scans, radiographs, fluoroscopy, and nuclear scans when needed.
ALARA means taking every reasonable effort to keep radiation doses as far below dose limits as possible. This involves weighing radiation risks versus benefits for necessary imaging. Use is justified only when benefits outweigh risks.
Here are some key points:
- Dentists follow ALARA by taking only required X-rays, using the smallest dose to achieve acceptable image quality, and shielding patients.
- Digital X-rays emit lower doses than film through shorter exposure times and tighter collimation. This aligns with ALARA.
- Dental X-rays follow ALARA by using fastest image receptors, collimating to the minimum size needed, and proper shielding.
- Techniques like rectangular collimation, higher kV settings, and proper patient/sensor positioning optimize the ALARA concept.
- Monthly exposure from dental radiographs is well below annual background radiation levels when ALARA is followed.
- Adhering to ALARA means critically evaluating if X-rays are clinically indicated, not taking them by routine.
In summary, the ALARA principle governs best practices for minimizing radiation exposure from imaging while balancing diagnostic benefits in dentistry and medicine. This helps maximize patient safety.
What if more are required for Urgent Needs?
If more X-rays are absolutely necessary for a specific urgent case per clinical judgement, it is still considered safe for a few reasons:
- Dental X-ray doses are very low compared to other exams like CTs. Even 20 periapical images in a month are well below a CT’s radiation.
- The monthly limits incorporate wide safety margins – higher doses are still reasonably safe based on research.
- Any risk elevation from X-rays needed for urgent diagnosis is outweighed by their benefit for managing serious conditions.
- Dentists collimation and shielding to strategically target only required areas and block sensitive tissues.
However, elective panoramic X-rays for non-essential purposes should not accompany required periapicals in the same month.
Strategies for dentists to limit dental X-ray exposure
Your dentist can take several steps to ensure you receive the least amount of exposure possible when X-rays are taken. These include:
- Placing a leaded shield over your body. A thyroid collar that shields your neck, while not mandatory, is recommended
- Using a collimator, which is a long tube that extends from the X-ray machine. Collimators limit the size and shape of the useful x-ray beam reaching the patient.
- Using the fastest type of film (E/F) or digital sensors.
Long-term Effects are Highly Unlikely
Despite internet myths, experienced dentists reassure that even double these monthly dental X-ray limits present:
- No increased cancer risk – Studies mixing dental/medical X-rays find no correlation. Dental X-rays make up only 0.4% of annual radiation exposures.
- No thyroid issues – Modern thyroid collars provide adequate shielding.
- No elevated risk for hereditary, fertility or pregnancy issues according to current evidence.
The accumulated exposures from multiple dental X-rays over a lifetime are well within safe ranges and nowhere near levels linked to adverse effects.
Final Word
While limiting radiation exposure is always advisable, monthly dental X-ray limits incorporate wide safety margins based on risks. Clinically necessary increased X-rays over 1-2 months are still considered very safe and far outweighed by their diagnostic benefits for assessing urgent dental issues.
Please consult your dentist for further assistance on the safe use of dental X-rays.
References
https://www.cda.org/Portals/0/pdfs/fact_sheets/xrays_english.pdf
