Developments in radiographic caries diagnosis.

The developments that have been taking place in radiographic caries diagnosis, within the context of the changes occurring in both the disease process and the available technology, are reviewed. The decline in caries prevalence seen in many western countries has been accompanied by changes in the pattern and behaviour of lesions. More lesions are now seen on occlusal surfaces, more are concealed (and thus imperceptible to conventional diagnostic techniques), while the average progression rates for approximal lesions have also slowed. Systems employed for caries diagnosis must take account of these changes and the varying needs of users employing different diagnostic thresholds. This paper reviews and discusses developments in: conventional film radiography; xeroradiography; indirect digital imaging (with computer image analysis and subtraction radiography), and direct digital imaging. It is concluded that: for the detection in high caries prevalence groups of both approximal caries (especially small lesions in enamel) and dentinal occlusal lesions in teeth with little or no surface breakdown, radiography is still a significant and reasonably accurate diagnostic method; and that, in spite of the more limited resolution, digital imaging methods seem to perform as well or better than conventional film radiography. Digital systems possess a number of advantages, primarily the possibility for image enhancement and significant dose reduction. It may be predicted that digital imaging techniques will enter the clinical routine in the near future.