Dentition
Teeth are arranged in the jaws in a way to form two dental arches. Each arch is named to correspond with the bone from which it is composed.
- The maxilla forms the maxillary or upper arch.
- The mandibular forms the mandibular or lower arch.
Together, these two arches make up one dentition, or set of teeth. During the life span, each person normally will have two dentitions:
- the primary or deciduous dentition;
- and the permanent dentition.
Primary dentition
The primary dentition or primary set of teeth, which in dentistry called deciduous dentition, begin to emerge in infants at 6-8th months of age. The primary 20 teeth continue to erupt periodically, following a developmental schedule: 10 maxillary and 10 mandibular teeth. These 20 primary teeth usually erupt by the time the child is 2.5-3 years old. These 20 deciduous teeth are small, but they fulfill the needs of a child.
As the child grows, primary teeth eventually fall out, or as called in dentistry exfoliate, or shed, and are replaced by the permanent teeth. When all permanent teeth have erupted, by the ages 17-21, the permanent dentition is complete.
Permanent dentition
Permanent dentition consists of 32 permanent teeth: 16 maxillary and 16 mandibular teeth. Only primary teeth are present in the mouth, until the child is 5 old. The first permanent teeth begin to erupt at 5-6 years of age in children.
By this age no deciduous tooth are necessary to exfoliate to provide space for permanent teeth, because mandible has increased in length so there are enough space to fit additional teeth.
Shortly after the permanent first molars erupt, deciduous incisors, the front teeth, begin to exfoliate. This occurs as a result of physiologic process that causes their roots to resorb as the permanent teeth form in the bone directly beneath them. Eventually all primary teeth exfoliate. Once permanent teeth erupt the permanent dentition will be complete.
Mixed dentition
Between ages 5-12, both some deciduous teeth and some permanent teeth are present in the mouth. That is called mixed dentition.
Permanent teeth that replace deciduous teeth are called succedaneous teeth and include incisors, canines, and premolars. Since permanent molars do not replace any primary teeth, they are not called succedaneous teeth.