X-ray safety requirements for all Ontario dentists

Originally published in the May/June 2011 issue of Dispatch. Updated June 21, 2024. 

The Healing Arts Radiation Protection Act (HARP), administered by the Laboratories and Diagnostics Branch, Health Program and Delivery Division of the Ministry of Health, was passed in 1980. The regulations (X-Ray Safety Code) passed in 1985 and applicable to the dental profession, were developed by the Dental Advisory Committee to the HARP Commission whose membership included practising dentists and dental educators. This legislation specifies operator qualifications and technical performance standards for x-ray machines and outlines the procedures and tests that are deemed necessary as well as their frequency, to ensure the highest possible level of patient and operator safety.

Operator qualifications

Under the HARP Act, the following operator qualifications with regard to patient safety are outlined:

• No person shall use an x-ray machine for the irradiation of a human being unless he or she has successfully completed a recognized course in radiology safety as a part of the qualifications in his or her specified discipline.
• A person enrolled in a recognized x-ray safety course may be permitted to operate an x-ray machine while under the supervision of a qualified individual. Dentists and dental hygienists are deemed to have met the required qualifications by virtue of their membership in their respective Colleges.

Dental assistants, however, must have taken appropriate training in x-ray safety to take radiographs, and must present proof of successful completion of such program, when requested to do so by X-ray Inspection Service inspectors (XRIS).

At the present time, most current Level I and Level II dental assisting programs in Ontario provide the appropriate training. A listing of programs that have already been approved by the HARP Commission, including private dental assisting programs, co-op high school dental assisting programs and out-of-province programs can be obtained from the school itself or the X-ray Inspection Service (XRIS) at xris@ontario.ca.

It is the responsibility of the dentist who has taken on the role of the Radiation Protection Officer (RPO) to ensure that all x-ray operators, including dental assistants, meet the qualification requirements under the HARP Act. Staff qualification documents must be readily available in the event of an inspection.

Registration of x-ray machines

All dental x-ray machines must be registered by the owner and new installations must be approved by the X-ray Inspection Service (XRIS). Plan approval ensures both patient and staff safety from unnecessary radiation exposure. To obtain approval, an application along with the floorplan must be submitted to XRIS for evaluation. Written approval to install and operate the x-ray machine must be obtained from the provincial Director of X-ray Safety.

Registration and approval forms can be found online. 

If you have recently renovated your office or purchased an existing practise and made renovations, it is important that you re-submit your plans for approval. If you have purchased a practice from another dentist and do not renovate, the pre-existing plans, if already approved by the Director of X-ray Safety, will suffice.

Ensuring proper record keeping of all facility documentation is of utmost importance for any X-ray machine owner and Radiation Protection Officer (RPO) appointed under the HARP Act. The owner is legally responsible for maintaining an up-to-date approved plan for their facility that accurately reflects the installation of all X-ray machines, including CT scanners.

For more information, please review the XRIS document for Facilities with Lost/Misplaced or “No” Plans.

When you inform the College of the change of practice ownership, it is recommended to also contact XRIS.

The HARP Act authorizes inspectors to enter and inspect premises at all reasonable times. Inspectors do not have to make an appointment but may provide dentists with advance notice in some situations.

The College recommends that you have all the necessary paperwork, including any forms or plans associated with the installation and operation of dental x-ray machines, readily available at the office. The Inspector visits your dental facility on average once every three to five years and stays on average for less than an hour or two depending on the number of x-rays machines, size of your practice and available required documents.

If an inspector visits your office and finds that the plan does not conform to the approved plan, he or she will issue an order indicating that you are in violation of the HARP Act. This can result in a stop use order preventing further use of the x-ray equipment. The dentist-owner of the practice must submit a new plan with the actual layout for approval or redesign his or her office to match the approved plan on file with the Ministry.

Patient Shielding

The HARP Act requires that protective accessories are available for use by persons who may receive exposure to x-rays. XRIS has advised that dental offices must have lead aprons available for patient use and must use thyroid shields. In offices that meet the requirements of section 3.0 of Safety Code 30, dentists are permitted to use their clinical judgment whether an abdominal lead apron is required.   

Quality Assurance Requirements

A key component of the HARP Act is the requirement that a Photographic Quality Assurance Program (QA) relative to x-ray shall be instituted in every dental office.

Quality Assurance is defined as a program of activities designed to ensure that diagnostic imaging is carried out with the maximum benefit to the patient, at a minimum of risk. The goal of the program is to confirm that the dentist is providing the highest quality care possible with respect to the use of x-rays.

In a dental facility, the primary objective of a QA program is to ensure that:

• Every imaging procedure is necessary and appropriate to the clinical problem at hand and is prescribed by a dentist.
• The images generated contain information critical to the solution of that problem.
• The examination results in the lowest possible radiation exposure, cost and inconvenience to the patient consistent with the diagnostic information requirements.
• Repeat films and exposure will be kept to a minimum.
• Accurate functioning of the x-ray equipment will be monitored.

Radiation Protection Officer

The responsibility for ensuring that quality assurance testing is carried out rests with the Radiation Protection Officer, who must be a dentist qualified to take x-rays. He or she is also responsible for all other matters of radiation safety related to the taking of x-rays in the dental office, such as ensuring that only HARP qualified personnel are permitted to take radiographs, and that the office has received Ministry of Health and Long-Term Care’s approval for the installation of x-ray equipment.

Prescribing of dental x-rays

The HARP Act requires that dental x-rays be prescribed by a dentist before they can be taken. A clinical rationale for taking the x-ray or x-rays, therefore, must first be determined by the dentist. The HARP Act precludes taking a set number of exposures or time sequence radiographs (i.e. every six months, every year etc.) without an individualized prescription for a particular patient, which is based on the results of a clinical examination.

Photographic QA Testing

The HARP Act also sets out certain requirements for photographic quality assurance tests for dental offices, clinics and facilities. The minimum requirements of an acceptable photographic QA program include the following:

Annual testing

• Patient entrance exposure measurements
• Collimation testing
• Half value layer testing

These tests must be carried out every 12 months and upon alteration or servicing of the machine. They can be accomplished by using a mail-in testing service, if available, or by arranging for a qualified service technician to come to the dental office.

Daily testing

• Photographic quality control testing

For conventional dental x-ray units, these tests must be performed every operational day and can be carried out by keeping a log referring to the number of films processed and the change cycle of the processing solutions, using a thermometer in the manual processing tank or a back-up thermometer in automatic processors, and recording and logging the temperature on a daily basis. It may also be helpful to compare the quality of a test film each day (the first exposure of the day) with that of a reference radiograph that was processed when film quality was known to be optimal. A step-wedge can also be used. Any variance from the ideal should be noted and corrected.

The radiographic quality control measures that are required for digital radiography, including panoramic radiography are:

• Perform daily photographic control testing on each x-ray machine.  The Ministry of Health X-ray Inspection Services (XRIS) recommends that offices test each x-ray machine by taking an image of an object that would show up on the screen, such as a step wedge or a metal clip, before the x-ray machine is used on a patient. The image should be stored in a “QA test file” as documentation.
• Record in a logbook the number of images exposed per x-ray machine per day.
• Record the number of retakes for each machine per day.
• Record the reasons for retaking the images and determine if the problem stems from operator error or from x-ray equipment/sensor malfunction. Corrective measures such as equipment recalibration or staff retraining in imaging technique can then be taken accordingly and recorded in the logbook.  

Records must be available as evidence that photographic quality control is being done every day of use.  Records must be maintained for 6 years. These requirements also apply to panoramic x-ray machines.

In conclusion

The guiding principle behind the HARP Act is that every dental patient in Ontario has the right to expect a high-quality x-ray examination with as small an amount of risk as possible. The Quality Assurance Program described in this article, as well as the other elements of the legislation, is meant to assist Ontario dentists in achieving this goal.

For more information, please see the College's FAQs on dental radiographs.