Digital enhancement of radiographs for assessment of interproximal dental caries

Abstract

Evaluation of a particular digital caries image-enhancing mode (filter) for its effect on the validity of measurements of caries lesion depth. 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. 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. The lesion type significantly influenced the validity of CD measurements: enamel lesions were less underestimated than dentin lesions.