The primary dentition in human differs from permanent dentition in not having one of the following type of teeth

The primary dentition in human differs from permanent dentition in not having Premolars. The deciduous molars are replaced by the first and second premolars (bicuspids). The permanent molars, which erupt into the mouth posterior to the premolars, do not replace any deciduous teeth and erupt as the jaw grows to accommodate them—the first permanent molars at age 6 (six-year molars), the second permanent molars at age 12 (twelve-year molars), and the third permanent molars (wisdom teeth) aft er age 17 or not at all.