Sir, since 2001 and the publication of Guidance notes for dental practitioners on the safe use of x-ray equipment by the National Radiological Protection Board (NRPB), the recommended method for assessing quality of radiographic imaging has been via a three-grade NRPB system: Grade 1 - 'Excellent', Grade 2 - 'Diagnostically Acceptable' and Grade 3 - 'Unacceptable'. This guidance was withdrawn in October 2020 and replaced with an updated second edition which is free to view and download from the College of General Dentistry (CGDent) website.1

The chief aim of dental radiography is to produce an image of adequate quality for diagnostic purposes, while minimising patient dose as far as reasonably possible.2 Measuring the quality of radiographs compared with NRPB guidelines is a common clinical audit performed across primary and secondary care and is a useful tool to help improve personal practice or check if the required standard is being met.2 Public Health England (PHE) previously recommend certain targets - eg >70% Grade 1 and <10% Grade 3.2

A move away from traditional film-based imaging towards digital imaging systems has removed the need for chemical processing, a major source of reduced image quality.2 As such, CGDent and PHE now recommend a two-point grading scale, where images are recorded as either 'diagnostically acceptable' ('A') or 'not acceptable' ('NA') (see Table 1).2

Table 1 Subjective image quality ratings of dental radiographs and CBCT images2
Full size table

An important point to note is the allowance for differentiation between digital and film imaging in the recommended targets when performing clinical audit. The new guidance details clearly defined elements of image quality analysis, quality assurance audits and image quality rating, of which all practitioners should be aware going forwards.