Milk teeth begin to erupt in the mouth during infancy and complete their eruption at about 2 - 2.5 years of age. There are milk teeth that remain in the mouth until the age of 11 - 12 until the permanent dentition period with various intervals. Decaying deciduous teeth must be treated according to the position of the permanent tooth coming from below. Otherwise, the decay will progress, the child will feel pain, and then it will become infected, which will affect the structure of the permanent tooth coming from below.