The baby's first teeth begin to errupt at the age of 6 months and the primary dentition is completed by the age of approximately 3 years. The four front upper and lower incisors will be raplaced between 6-8 years of age, but the posterior primary molars will remain in the mouth until the age of 12 years. This is quite a long time and those molars need proper care in order to be cavity free. Dental decay progresses quickly in primary molars, it can easily reach the pulp, creating necrosis and abscesses that will affect the permanent teeth that follow.