A 14-year-old child complains about a cosmetic defect in the frontal teeth region. Objectively: enamel of the 11, 12, 21, 22, 31, 32, 41, 42 teeth is thin in the region of cutting edge, there is a sulcate enamel pit 1,5 mm wide which encircles the tooth and is parallel to the cutting edge. The cusps of the 16, 26, 36, 46 teeth are underdeveloped and have conical form. What is the most likely diagnosis?