The primary teeth begin to form during the embryonic stage of pregnancy in the sixth week of lamina development. This process begins at the midline and then extends towards the posterior regions. By the time the fetus is eight weeks old, there will be ten buds in the maxillary and mandibular arches, which will eventually become the primary teeth.
Lower teeth of seven years old, showing primary teeth (left), missing primary tooth (middle), fully erupted permanent tooth (left).
These teeth continue to form until they erupt in the mouth. In the primary dentition there are a total of twenty teeth, five per quadrant and ten teeth per dental arch. The eruption of these teeth begins at the age of six months and continues until the age of 25-33 months during the first dentition period. Usually the first primary teeth to appear in the mouth are the lower central incisors, and the last of these is the upper second molars. The primary dental group consists of: the central incisors, the quadruple incisors, the canines, the first molars, and the second molars; There is one per quadrant, for a total of four teeth per species. All are gradually replaced by corresponding permanent teeth, with the exception of the first and second molars, where they are replaced by premolars. These teeth are designated in the “International Dental Designation System” with capital letters A-T.[6] The replacement of primary teeth begins at the age of six when the permanent teeth begin to appear in the mouth, producing what is known as a mixed dentition. The erupting permanent teeth cause “root resorption, whereby the permanent teeth push the roots of the primary teeth, causing them to dissolve by odontogenic cells (in addition to the surrounding alveolar bone by ossifying cells). Then they are resorbed by the evolving permanent teeth. The process of falling primary teeth and replacing them with permanent teeth is called « Peeling”, and this process may continue from the age of six to twelve years, and usually at the age of twelve, only permanent teeth remain.
Age of teething for primary teeth:
Central incisors: 6-12 months.
Quadruple incisors: 9-16 months.
First molar: 13-19 months.
Canines: 16-23 months.
Second molar: 22-33 months.
