An evaluation of the diagnostic yield from bitewing radiographs of small approximal and occlusal carious lesions in a low prevalence sample in vitro using different film types and speeds.

Aim: To compare diagnostic yield in caries diagnosis from D- and E-speed films.

Design: A laboratory study.

Setting: A UK dental school between 1992 and 1994.

Materials And Methods: 96 extracted teeth containing approximal and occlusal lesions, but representing a low caries prevalence sample, were set in occluding dental arches. Bitewing radiographs were taken and interpreted by 5 examiners for the presence or absence of caries. Each examiner was also asked which film image he or she subjectively liked best.

Main Outcome Measures: The teeth were subsequently sectioned and histologically examined to validate diagnostic decisions.

Results: For all film types the percentage of lesions with caries histologically in dentine correctly identified radiologically (sensitivity) was low (approximal caries 8-22%; occlusal caries 0-30%). The number of sound dentine sites correctly identified (specificity) was high (approximal caries 98-100%; occlusal caries 79-100%). There were no significant differences between D- and E-speed films. Sensitivity was unaffected by each examiner's subjective preference for a particular film. The variation in sensitivity of diagnosis was due to differences between examiners.

Conclusions: The reluctance of many GDPs to use E-speed film because they 'do not like the image' cannot be endorsed or supported. Both E-speed film types examined can be recommended for use in general practice.