Digital enhancement of radiographs for assessment of interproximal dental caries

Objectives: Evaluation of a particular digital caries image-enhancing mode (filter) for its effect on the validity of measurements of caries lesion depth. Methods: Standardized radiographs of 44 extracted teeth exhibiting interproximal caries lesions were obtained. Six radiographs were obtained of each tooth and digitized. Four radiographs were made using D-speed film with and without soft tissue scattering equivalent (STSE) at normal exposure time (0.32 s) and underexposed (0.16 s). Two were made using E-speed film with STSE normally (0.16 s) and underexposed (0.08 s). On each of the 264 radiographs, 4 independent examiners measured the central depth (CD) of 1 carious lesion per tooth both on the unchanged radiographic image and after use of the filter. Histometric CD assessments provided a gold standard for comparison with the radiographic measurements (validity). Repeated measures ANOVA was calculated for validity in relation to examiner, lesion type, filter, film type, exposure time and STSE. Results: The lesion type was identified to statistically significantly influence the validity of CD measurements. Examiner in combination with defect type (P < 0.001), filter (P = 0.017), exposure (P = 0.027) and film type (P = 0.044) had an additional albeit small effect. Conclusions: The lesion type significantly influenced the validity of CD measurements: enamel lesions were less underestimated than dentin lesions.