A baby's first tooth typically appears somewhere around six months. The lower central incisors (the two front teeth) usually erupt between 6 to 10 months while the top central incisors appear between 8 and 12 months. The next set of teeth are the lateral incisors, erupting between 9 and 16 months, followed by the canines (the pointy teeth) at 16 to 23 months. The first molars appear at 13 to 18 months and second molars at 23 to 33 months. By a child's third birthday, he/she should have a full set of primary teeth (20 teeth total).

At around age 6 or 7, the primary teeth begin to fall out and are replaced by permanent teeth. Adults normally have a total of 32 permanent teeth (16 on the top and 16 on the bottom), which include the central incisors, lateral incisors, canines, first premolars, second premolars, first molars, second molars and wisdom teeth (sometimes referred to as the third molars).

The Wisdom Teeth
Wisdom teeth generally begin to erupt around age 18 to 20. If the teeth are properly positioned, they cause no problems. In some cases, there isn't enough room for the third molars. As the teeth try to move out of the gums, they can become impacted (trapped, partially emerged or growing sideways). An impacted wisdom tooth can cause infection, gum disease or decay of adjacent teeth. In some cases a cyst or tumor may form from the tooth follicle. Wisdom teeth that are impacted or causing problems are often removed.

Reappearance of the Wisdom Teeth
On rare occasions, a patient may experience the development of extra teeth, referred to as "supernumerary teeth." The exact occurrence of supernumerary teeth is not certain, but researchers estimate the condition occurs in less than four percent of the population. Most of the time, the extra teeth are located in the upper jaw. Men seem to be affected more often than women. In many cases, the tendency for supernumerary teeth runs in families.

Extra wisdom teeth are often smaller than normal third molars and may be misshapen and poorly aligned. Dental experts say the teeth are present at the time the original wisdom teeth are removed, but may not be easily accessible. So the dentist or oral surgeon will wait until the extra teeth move into position before deciding to remove them.

For general information on wisdom teeth:
Academy of General Dentistry, http://www.agd.org
American Dental Association, http://www.ada.org

Source: Medstar