Radiography and Imaging Support

Radiography in Dental Practice

Radiographs (x-rays) are indispensable diagnostic adjuncts in modern dentistry. They allow clinicians to visualize structures hidden beneath the gingiva and enamel, such as interproximal carious lesions, apical pathology, bone levels in periodontal disease, and unerupted teeth. However, x-rays are a form of ionizing radiation. When radiation passes through human tissue, it can cause cellular damage, DNA mutations, and an increased, cumulative risk of developing malignancies over a lifetime. Due to this inherent danger, strict legal frameworks govern the ownership, maintenance, and usage of radiographic equipment to safeguard patients, dental staff, and the general public.

The Legislative Framework

There are two primary sets of regulations governing dental radiography in the UK, each with a distinct focus on who is being protected.

1. Ionising Radiations Regulations 2017 (IRR 2017)

IRR 2017 is strictly concerned with the protection of workers (the dental team) and the general public from the hazards of ionizing radiation. The key requirements enforced under IRR 2017 include:

• HSE Notification: The practice must legally notify the Health and Safety Executive (HSE) before using x-ray equipment.
• Radiation Protection Advisor (RPA): The practice must appoint an external RPA (typically a highly qualified medical physicist). Their role is to provide expert, independent advice on regulatory compliance, equipment safety, and practice layout.
• Radiation Protection Supervisor (RPS): This is an internal staff member, usually a senior dentist, appointed to ensure that all local compliance is adhered to on a daily, practical basis.
• Local Rules: A mandatory written document detailing the safe working practices tailored to the specific practice. It must list the RPA and RPS, identify the controlled areas, describe contingency plans in the event of equipment malfunction, and outline specific working instructions. Every single staff member involved in radiography must read, understand, and sign the Local Rules.
• Controlled Areas: This is the designated zone around the active x-ray machine where radiation doses may exceed safe limits during exposure (usually within 1.5 meters of the tube head). This area must be clearly defined, warning lights must illuminate during exposure, and absolutely no one except the patient should be inside the controlled area when the machine is activated.

2. Ionising Radiation (Medical Exposure) Regulations 2017 (IRMER 2017)

While IRR protects workers, IRMER 2017 is strictly concerned with protecting the patient undergoing a medical exposure. The regulation is built upon three foundational principles: Justification (the diagnostic benefit must outweigh the radiation risk), Optimization (ensuring doses are kept As Low As Reasonably Practicable, or ALARP), and Limitation (using proper equipment and techniques to limit exposure).

IRMER mandates specific legal duty holders:

• Employer: Usually the practice owner or corporate body. They are legally responsible for providing safe, maintained equipment, writing standard operating procedures (SOPs), and ensuring all staff are adequately trained and continually competent.
• Referrer: A registered healthcare professional (almost always the dentist) who requests the radiograph based on clinical need.
• Practitioner: A registered professional who formally justifies the exposure. They take responsibility for the final decision that taking the x-ray will provide a net benefit to the patient.
• Operator: This role applies to anyone carrying out the practical aspects of the exposure. Responsibilities include positioning the patient, positioning the film/sensor, selecting exposure settings, pressing the exposure button, processing the film, and performing quality assurance tests. Qualified dental nurses frequently act as Operators. They must be adequately trained, competent, and authorized by the Employer to perform these tasks.

Types of Radiographs and Imaging Sensors

Radiographs are broadly categorized into intra-oral (film/sensor placed inside the mouth) and extra-oral (sensor placed outside the mouth).

• Bitewings: Taken to show the crowns of upper and lower posterior teeth simultaneously. They are the gold standard for detecting interproximal (between the teeth) caries and evaluating the fit of restoration margins.
• Periapicals: Used to view the entire length of a specific tooth, from the crown down to the apex (root tip) and the surrounding periapical bone. They are vital for diagnosing apical abscesses and planning root canal therapy.
• Dental Panoramic Tomograph (DPT / OPG): An extra-oral image providing a sweeping, wide view of the entire maxilla, mandible, TMJ, and all erupted and unerupted teeth. They are heavily utilized for wisdom tooth assessments and orthodontic planning.

Traditional imaging uses chemical film packets, containing an outer waterproof wrapper, a lead foil to prevent radiation scatter, black paper to protect from light, and the radiographic film itself. Modern practices increasingly use digital radiography, which significantly reduces patient radiation doses. Digital systems use either solid-state direct sensors connected via USB or photostimulable phosphor plates that are scanned into a computer.

Processing and Quality Assurance (QA)

In practices still utilizing wet chemical processing, the correct sequence must be followed: Development (chemicals convert exposed silver halide crystals into black metallic silver), Washing, Fixation (chemicals remove unexposed crystals, clearing the image and making it permanent), Washing again, and Drying. Chemical errors such as light fogging, underdevelopment (producing a pale image), or fixer splashes destroy image quality.

A robust Quality Assurance (QA) program is legally mandated to ensure images are consistently diagnostic, thereby eliminating the need for retakes which needlessly double the patient's radiation dose.

• Image Quality Rating: Every radiograph taken must be subjectively graded and recorded in the patient's notes.
  • Grade 1: Excellent quality, no errors in positioning, exposure, or processing.
  • Grade 2: Diagnostically acceptable. Some minor errors exist but they do not detract from the diagnostic value.
  • Grade 3: Unacceptable. Critical diagnostic information is missing or obscured, necessitating a retake. The standard target is to achieve over 70% Grade 1 images and less than 10% Grade 3 images.
• Equipment Testing and Maintenance: X-ray units must be routinely serviced and tested by an engineer. Processing equipment (like automatic developers or digital scanners) requires daily/weekly checks, such as using step wedges or coin tests to check for light leaks.
• Training Logs and Audits: Comprehensive records of ongoing Continuing Professional Development (CPD) in radiography must be maintained. Regular clinical audits must be performed to identify patterns in Grade 3 errors so that corrective action can be taken.