We, like most other mammals, have two sets of teeth in our lifetime. The first set are called milk or deciduous teeth which last us through childhood. The second set are called adult or permanent teeth. Teeth start forming in the jaws even before we are born, and we don't get the full set until late teens.
The deciduous teeth come through first, and then they fall out to make way for the adult ones as children get older. Our timeline is only an average guide to these ages, and some people may get their teeth sooner or later than the ages given. Dentists can check children's teeth to see if they are coming through at the right time.
Birth (0 months)
When babies are born, their teeth are still growing inside the jaws. The first set of teeth (milk or deciduous) don't usually start appearing in the mouth until around age 6 months.
By about six months, the first tooth appears in the mouth. It is usually one of the lower central incisors followed soon after by the other lower central incisor.
By about 9 months of age, four front teeth at the top, and four at the bottom (called central and upper incisors), will be showing.
At a year old the lower first deciduous molars start to come through, and are the first of the back teeth. The upper first deciduous molars come through a bit later by about 14 months. The lower deciduous canines come through at about 16 months and the upper canines a couple of months later.
At age 20 - 24 months, the last of the baby teeth (the upper and lower second deciduous molars) erupt, so by the age of 2 1/2 years, all the deciduous teeth should be visible in the mouth.
Age 6 years is the time when the deciduous (milk) teeth start to drop out, and the permanent (adult) teeth start to come through in their place. The first milk tooth to be lost is the lower central incisor from around 6 years of age. It becomes wobbly and then falls out, and the permanent (adult) tooth will start to come through (erupt) soon afterwards. The first of the adult molars also start coming through at the back from around 6 years, behind all the deciduous teeth (and are called the first permanent molars).
All four permanent lower incisors arrive in the mouth between 6 and 8 years, starting with the two central ones first. The four upper deciduous central incisors start falling out from around 7 years, and the new permanent upper central incisors are the first to start showing. The upper and lower first permanent molars have usually started to erupt by now.
All four lower permanent incisors should be showing by now, but the upper permanent incisors will probably still be coming through (the upper central incisors first followed by the upper lateral permanent incisors).
By nine years, all four upper permanent incisors should be showing. Some of the other adult teeth start coming through about now, and ones to watch out for are the lower permanent canines (or 'eye teeth'). The first deciduous molars start falling out as early as 9 years, and new adult teeth (called first premolars) start growing in their place.
The lower permanent canines may still be coming through at 10 years, and the second deciduous molars start falling out to make way for the adult second premolars.
The upper deciduous canines and second permanent molars are often the last of the milk teeth to fall out. The upper permanent canines and second premolars can then start coming through in their place.
By 12 years all the milk teeth have usually been lost. Between 12 and 13 years is also the age when the permanent second molars erupt.
By about 13 years old, the average teenager should have 28 permanent teeth. The upper and lower second molars are the final teeth to come through before the wisdom teeth.
If there is enough room for them, the third molars (or 'wisdom teeth') normally erupt in the mouth any time between the ages of 17 and 21 years.
It is quite normal for teeth to darken slightly and show some signs of wear with age. However, the effects of not looking after your teeth and gums properly can become more obvious as you get older.
Gum disease can lead to receding gums so that the roots of teeth (which are darker than the crowns of teeth) begin to show. Teeth may loosen because of this or even move position (migrate), resulting in gaps between teeth that weren't there before and teeth looking more crooked. Untreated tooth decay can lead to unsightly or broken teeth, and teeth may be missing because they have had to be removed (extracted).
The important thing to remember is that teeth are meant to last a lifetime, and that regular visits to the dentist, a healthy diet, and keeping your mouth clean could mean that your teeth and gums look good always.