Review article: radiation protection in dental radiology.

Dental radiology represents the most frequent diagnostic radiological investigation in the industrialized world, with over 16 million examinations performed annually in England and Wales alone. Although individual doses and risks are low in dental radiography, the collective dose is not inconsiderable and many examinations are performed in younger age groups. Radiation protection of patients in dental radiology is achieved in three ways: by appropriate selection criteria for patients and equipment, methods of dose limitation and quality assurance procedures. There is a lack of agreed radiographic selection criteria to guide British dentists and this may lead to overuse of certain techniques, principally panoramic radiography. In intraoral radiography the use of fast (E-speed) film and rectangular collimation offer dose reductions of approximately 50% and 60%, respectively. Constant potential X-ray units and rare-earth filtration permit further reductions. In panoramic and cephalometric radiography, improved collimation offers a simple means of dose limitation, while doses can be reduced by up to one-eighth by combining the use of constant potential X-ray units, rare-earth intensifying screens and rare-earth filtration. Lead protection of the abdomen has little relevance to radiation protection; however, thyroid shielding has some value. Concern has been expressed about the poor diagnostic quality of radiographs taken in the general dental services. Consequently a quality assurance programme plays an essential part in dental radiation protection by improving diagnostic yield and limiting repeat examinations.