Tooth development

Before Birth

By the third week after conception the primitive mouth has formed. Over the next few weeks the tongue, jaws and palate develop. During the sixth week formation of the teeth commences, and by eight weeks all of the primary (deciduous) incisors, canines and molars are discernable. The permanent teeth begin to develop shortly afterwards.

After Birth

The development of the teeth within the jaw continues after birth. Normally the primary teeth start to appear in the mouth around six months after birth. The primary central incisors, lateral incisors, first molars, canines and second molars appear in this order at intervals from 6-24 months. For each tooth type, lower teeth tend to appear about two months before the uppers. By two years most children have their full compliment of 20 primary teeth, that is five on each side of the midline of the top and bottom jaws.

As the child grows the jaws grow and spaces may begin to appear between the primary teeth. This growth makes spaces for the larger permanent teeth. The growth in jaw length also accommodates the permanent molar teeth, which appear behind the primary teeth.

The first permanent teeth to appear in the mouth are normally the four first permanent molars. These erupt at around age six years behind the primary teeth. At the same time the two lower central primary incisors begin to loosen and then fall out and are replaced by the lower central permanent incisors. Over the following six years (6-12) the remaining 18 primary teeth fall out and are replaced by permanent teeth. At about age 12 the four second permanent molars appear behind the first permanent molars. The last teeth to appear are the 3rd molars or wisdom teeth. Not everybody has 3rd molars and there is considerable variation in the age at which they erupt.

Teething

During the first two years of life many symptoms have been attributed to teething. The most common side effect of teething is drooling. Symptoms of teething may include disturbed sleep, feeding irritability and swollen tender gums. The response to tooth eruption is very varied however; other more severe symptoms such as diarrhoea, fever and convulsions should not be attributed to teething and require medical attention.