Approximal caries diagnosis in epidemiological studies: transillumination or bitewing radiographs?

The aim of this study was to compare the results obtained by transillumination and bitewing radiography in the diagnosis of caries affecting approximal surfaces of molar and premolar teeth for epidemiological surveys. 3960 posterior approximal surfaces on the right side of 330 patients aged 5 to 35 years were examined using a transillumination probe with a 1.5 mm diameters light source (Oralum, Rocky Mountain, Denver, Colorado) and bitewing radiographs using a portable dental apparatus (Elin, Wien, 60kV, 15mA. Transillumination detected 89% of the carious lesions reaching dentine diagnosed on radiographs and no statistically significant differences were observed in the diagnosis yield of the two systems. However, transillumination detected only 45% of these lesions diagnosed from bitewings as being confined to the enamel. Transillumination also made it possible to detect approximal caries into dentine in teeth covered by orthodontic bands. Thus comparative study gives experimental support to the use of transillumination in large epidemiological studies. The transillumination method is however not suitable for epidemiological trials including caries confined to the enamel.