Formations of the Dentitions:- Humans have two sets of teeth during a life time.The first set of teeth to be seen in the mouth is the primary or deciduous dentition,which begins to form about 14 weeks in utero and completed at about age 3. In the absence of dental disease or trauma,the teeth appear at the age of 6.At the age of 6,the permanent teeth begin to emerge in to the mouth.from the primary dentition to the permanent dentition begins with the emergence of the first permanent molars,shedding of the deciduous incisors and emergence of the permanent incisors.The mixed dentition period is a difficult time for the young child because of habits,missing teeth,teeth of different colours and malposed teeth.permanent dentition completed at age 18 to 25.