Aims: To compare the intra- and inter-assessor agreement and operator preference of a modified (four-grade) quality rating system for dental radiographs with the current National Radiological Protection Board (NRPB) (three-grade) quality rating system.
Methods: Sixty radiographic images of varying quality were selected by retrospective review of dental records from a general dental practice. The images were sorted into groups to represent examples of radiographic quality (1=excellent, 2=diagnostically acceptable, 3=diagnostically compromised, 4=unacceptable). A 'gold standard' for radiological quality assessment was provided by a consultant in dental and maxillofacial radiology. A compact disc (CD) of the 60 images was produced and posted to a panel of 14 general dental practitioners (GDPs) who were asked to grade the quality of the images using two different systems on two occasions separated by a washout period of two days. The practitioners graded the radiographs using the currently accepted method for assessing radiographic quality (the three-grade NRPB system) and the alternative four-grade system. The quality of the images on the CD was deemed appropriate by the consultant.
Results: The strength of inter-assessor agreement was weaker when using a four-grade system in comparison to a three-grade system, reducing to a mean of k=0.51 from a mean of k=0.61 when using the original grading system. Mean agreement did not fall below 'moderate agreement' (k=0.41-0.60). Eleven of the 14 GDPs preferred the four-grade system.
Conclusion: The GDPs who participated in this study preferred the four-grade system to the three-grade system when comparing the quality of dental radiographs. However, the strength of agreement was weaker when using the four-grade system in comparison to the three-grade system. Overall, the results are equivocal. However, they should help to inform specialist dental radiology panels, should revision of quality grading be undertaken in the future.