Routine examination of a 9-year-old girl revealed symmetrical horizontal grooves on the vestibular surfaces of the 16,12,11, 21, 22, 26, 31, 32, 36, 41, 42, 46 teeth. The grooves alternated with intact tooth tissues and were present in these teeth at the time of their eruption. The patient has a history record of pneumonia at the age of 10 months treated with a course of antibiotics. Make a diagnosis: