Aim. The research was designed to assess the capabilities of the microcomputer tomography method with the subsequent image analysis and determination of the mineral optical density of demineralized areas to improve the early diagnosis of fissure caries of permanent molars after the eruption.Materials and methods. Using a high-resolution X-ray microtomograph “Skyscan 1176” (“Bruker”, Belgium) followed by post-processing and analysis of the obtained tomograms, 75 molars of children aged 8-11 were removed by orthodontic indications. Of the total number of teeth removed, research groups were formed – teeth without signs of demineralization and teeth with carious lesions in the stage of white, light brown, brown and black spots. In the reconstructed 2D and 3D images were identified the zones in the outer (0.05-0.5 mm), middle (0.75-1.25 mm) and inner (1.5-2.0 mm) thirds of the thickness of the enamel layer followed by the computation in the CTvox program (3.3.0-1403, Bruker-micro CT) of the averaged X-ray (mineral) density indicators. Results. According to the tomograms of the teeth of the studied groups, the average indicators of the mineral optical density of the intact teeth enamel were identified as well as the average indicators of teeth with various types of carious lesions within the enamel. The following sequence was revealed in descending order of the parameters of optical density: healthy enamel (2.47±0.12 g/cm3) – caries in the white spot stage (2.41±0.11 g/cm3) – caries in the light brown spot stage (2.32±0.07 g/cm3) – caries in the brown spot stage (2.18±0.12 g/cm3) – caries in the black spot stage (1.81±0.12 g/cm3). Identifying the correlations between the color of carious lesion and mineral density of tooth enamel broadens the understanding of the mechanisms of the development of caries pathogenesis and contributes to the improvement of therapeutic and preventive measures aimed at improving caries resistance.Conclusion. The use of microcomputer tomography in combination with other special methods characterizes fissure caries as a sequential, gradually progressing destructive process of hard tooth tissues (from focal demineralization to cavity formation), which establishes the relationship between the intensity of internal disturbances and external damage.