Composite materials are used in dentistry to rebuild hard tissues of teeth, destroyed by caries disease. Composites intended for dental direct fillings are polymerized with visible light generated by polymerization lamps. The temperature changes during polymerization can be measured within method like thermography. The study used 20 molars without caries, removed from orthodontic indications, A thermal imaging camera was used to test the temperature distribution of composite materials during the polymerization process. The work was taken up about the possibility of imaging the temperature distribution during the polymerization process of composite fillings in human teeth tissues. Temperature distribution was analyzed at specific locations of tooth tissues, particularly in terms of heat migration towards pulp. At the sites of separation of tooth materials and tissues, an attempt was made to assess the hardness of fillings and tissues. It can be concluded that the temperature during test did not exceed 42 °C, at which the tooth pulp is damaged. During cooling, heat spreads through the filling, not through the tooth tissues. Bulkfill did not show a difference in fill hardness regardless of the distance of the light source but GC composite hardness depends on the distance of the light source.