There are two sets of teeth in the human body, the baby and the permanent.
The baby dentition consists of 20 teeth and appears in the oral cavity around the 7th month of the child's life. Completion occurs approximately when the child is 3 years old. Statistically, the last baby tooth is lost when the child is 12-13 years except for cases of congenital missing ,that can last for life.
Baby teeth begin to be replaced by the permanent ones at the age of approximately 6 years.
The age in which baby and permanent teeth coexist is defined as the period of the mixed dentition.
Permanent dentition consists of 32 teeth and is completed at the age of 20 years approximately with the eruption of wisdom teeth.