How many teeth do humans have? Kids v adult teeth.

Dr. Mohamed Tarek DDS author

Dr. Mohamed Tarek, BDS, MFDS RCSEd, Member of AACD

Diagram that shows the number and names of all the teeth for adults and kids.

How many teeth do humans have?

Throughout our lives, we all have two separate sets of teeth, one set for our childhood and the other for our adult life. When we are babies we develop 20 baby teeth (also called primary teeth or deciduous teeth) which we keep until the ages of 5 or 6 years. After that, these baby teeth will gradually fall out and be replaced with 32 permanent adult teeth.

How many baby teeth do children have?

Children develop 20 teeth in total between the ages of 6 months – 33 months. 10 teeth are situated in the top jawbone (maxillary arch) and 10 are in the bottom (mandibular arch). The 20 teeth can be divided into three classes based on their unique shape and function during chewing.

  • 8 x incisor
  • 4 x canine
  • 8 x molar

Incisor teeth

Children have eight incisors in their primary set of teeth. The front four teeth in both the upper and lower jaws are incisors and they are used for cutting and slicing food. The two very front teeth are called central incisors and the teeth to the left and right are called lateral incisors.

 Canine teeth

Canine or cuspid teeth are used for tearing and cutting food. Kids have four canine teeth which is exactly the same amount as adults have in their second set of teeth. There are two canine teeth in the upper jaw and two in the lower jaw and they sit either side of the mouth next to the lateral incisors.

Molar teeth

The front eight teeth in both the upper and lower jaws are identical in the primary and secondary sets of teeth. There are always eight incisors and four canine teeth regardless of age. The difference between adult and kids teeth is the number of molars. The molar teeth are used to mash and smash up food before it is swallowed and digested. Children have eight molars in total, four are the first molars and four are the second molars. The first molars sit next to the canine teeth and the second molars sit next to the first molars. The second molars are the last teeth at the back of the mouth. Baby teeth do not all emerge together, with different sets of teeth erupting at different stages throughout the teething process.

Diagram showing the number of teeth that kids have.

The two lower central incisors are the first teeth to come in and usually push into place between 6 – 10 months.

The two upper central incisors erupt slightly later than the corresponding lower incisors and usually come in at between 8 – 12 months.

The two upper lateral incisors erupt at between 9 – 13 months.

The two lower lateral incisors emerge at between 10 – 16 months

The two upper first molars erupt at between – 13 – 18 months.

The two lower first molars erupt at between  – 14 – 19 months.

The two upper cuspid (Canine) teeth emerge at between 16 – 22 months.

The two lower cuspid (canine) teeth emerge at between 17 – 23 months.

The two lower second molars erupt at between – 23 – 31 months.

The two upper second molars emerge at between – 25 – 33 months.

How Many Teeth Do Adults Have?

A complete set of adult teeth is comprised of 32 teeth in total: 16 in the top jawbone (maxillary arch) and 16 in the bottom jawbone (mandibular arch). The 32 teeth are divided into 4 different classes based on their shape and purpose.

  • 8 x incisors
  • 4 x canines
  • 8 x premolars
  • 12 x molars

Incisor teeth

Adults have 8 incisor teeth which comprise of 4 central incisors and 4 lateral incisors. The central incisors are the two very front teeth in the upper and lower jaws and the lateral incisors sit next to them on the left and right.

Canine teeth

The secondary set of teeth contain 4 canines which are situated on the left and right-hand side of the lateral incisors of the upper and lower jaw bones.

Premolar teeth

The adult set of teeth contain 8 premolars in total which are located between the permanent canines and the permanent molars. There are 2 premolars on either side of 18the mouth on both the upper and lower jawbones. The adult premolars sit in the positions vacated by the 1st and 2nd primary molars of the baby teeth.

Molar teeth

The adult teeth have 12 molars in total. There are 3 molars located behind the 2nd premolar on either side of the mouth on both upper and lower jawbones. Since the premolars take the place of the 1st and 2nd molar baby teeth, the 3 permanent molars erupt into the empty spaces where no primary teeth were positioned before.

Diagram showing the 32 teeth that adults have.

The two adult lower central incisors emerge between the ages of  6 and 7 years.

The two upper central incisors will emerge between the ages of  7 to 8 years.

The two adult lower lateral incisors emerge at between 7 to 8 years.

The two upper lateral incisors emerge between the ages of 8 and 9 years.

The two adult lower cuspid (canine) teeth emerge at between 9 to 10 years.

The two adult upper cuspid (Canine) teeth emerge at between 11 and 12 years.

The two upper first premolar (bicuspid) teeth emerge at between 10 and 11 years.

The two lower first premolar (first bicuspid) teeth emerge at between 10 to 12 years.

The two upper second premolar (bicuspid) teeth erupt at between 10 to 12 years.

The two lower second premolars (second bicuspid) erupt at between 11 and 12 years.

The two upper secondary first molars emerge between 6 and 7 years.

The two upper secondary first molars emerge between 6 and 7 years.

The two lower adult second molars emerge at between the ages of 11 and 13 years old.

The two adult upper second molars emerge between 12 and 13 years.

The two upper third molars (wisdom teeth) emerge between the ages of 17 and 21 years.

The two lower third molars (wisdom teeth) erupt at between 17 and 21 years.

So you might wonder why there is a difference, and why do we have two separate sets of teeth. Why aren’t we just born with our adult teeth and have them grow as we grow? And if these teeth are going to fall out anyway, why do we need to brush and floss and take care of them when they will eventually be replaced? These are all very good questions, and to answer them you need to learn all you can about baby teeth.

Baby teeth are a lot different than adult teeth, they are smaller in size as well as fewer in number and they are not as strong and not as full of minerals like Calcium and Potassium as adult teeth.

Human teeth start to develop during pregnancy, while the child is still in his mother’s womb. The first tooth germ (which is the origin of each tooth) appears as early as 10 weeks of pregnancy. The last one to develop appears around 7 months of pregnancy.
Here we can notice the first difference between baby and adult teeth, in that the entire set of baby teeth are completed inside the womb, and they are ready to emerge in the mouth once the baby is born, whereas some of the adult teeth are still in their germ form at birth, and start to develop and be mineralized at 1 or 2 years of age, meaning they can be affected by the amount of minerals intake and other environmental factors such as the level of Fluoride in drinking water.

Which baby teeth come teeth first?

The first tooth to emerge in your baby’s mouth is the lower front tooth, and that happens at 6-10 months of age, followed by the upper front tooth at 8-12 months, and then comes to the upper and lower lateral incisors (the teeth right next to the front teeth) at about 10 months. The first molar follows, where the upper comes in at about 13 months and the lower at 14 months. The canine is a bit delayed, coming only after the first molar appears at 16-17 months. The last baby tooth to come out is the second molar, the one farthest back in the mouth, at about 2 years of age. These baby teeth last up to 6 or 7 years when the first permanent tooth starts to appear, that is the permanent first molar, appearing behind all these teeth (meaning this particular molar has no baby tooth before it and therefore will come in without another tooth falling out).

These numbers are of course average, and some children have their teeth erupt much earlier, and some quite later, which is a very normal process.
The number of baby teeth is also smaller, where a normal child has only 20 teeth, 10 in the upper and 10 in the lower, just enough to fit the small jaw, compared to 32 adult teeth, 16 upper and 16 lower.

Why are some children slow to teeth?

In some cases, the eruption of the permanent teeth could be delayed due to many factors. Sometimes the process is just natural and the child is just a late bloomer, but in other cases, a problem could be present where the bone or the baby teeth could be harder than normal, and therefore the permanent tooth will have a hard time making its way to the surface, and the baby tooth could be retained to adulthood. Another instance is when the permanent tooth is out of place, and so it cannot take its normal path to the correct position, and it could either erupt in an abnormal position (called ectopic eruption) or not erupt at all and get impacted in the jaws. Most of these problems will need braces in the future.

Why do adults and kids have different sets of teeth?

So why do we have two sets of teeth, and why do we have to endure the process of teeth falling out only for new ones to come in?
The reason is simple; when we were kids, we have smaller jaws and bones, and therefore there is no space for the big permanent teeth, and we have to live with our baby teeth until the jaws become large enough to accommodate the large permanent teeth, that’s why you might notice at the age of 6 to 9 years, there are large spaces between the child’s teeth, which is completely normal considering the jaws have now enlarged, and some of the baby teeth are still present. Another reason for baby teeth is their use, where most of the children’s food is soft, and doesn’t require the strong permanent teeth for chewing, and the smaller and weaker baby teeth are more than sufficient.

When do baby teeth start falling out?

Baby teeth start falling out when the permanent teeth are ready to come in, and that starts around 6 or 7 years of age, and the sequence is nearly the same as the baby teeth. The process by which teeth fall out (also called eruption) is an intriguing process. When the adult tooth is ready to come out, it starts to work its way up to the surface, and when it meets the root of the baby tooth, its stimulates certain cells to start eating away at the root, until there is only a little part of the baby tooth remaining, and the tooth becomes mobile, and it may fall out by itself, or sometimes the child or parent is eager to remove it manually. This happens serially in every tooth that is shed until the full set of baby teeth is replaced by adult teeth. You should also know that there are 20 baby teeth compared to 32 adult teeth, meaning there are 12 teeth that have no baby teeth before them, and it is normal if you see more than 20 teeth in your child’s mouth at the age of 6 or 7 years.

Why is it important to look after baby teeth?

Now to the real question: “Is it important to take care of the baby teeth, knowing they will fall out eventually?”
Unfortunately, this is a very common misconception, where most parents think that their children’s teeth are only temporary, and there is no need to maintain them properly. This could not be further from the truth for a number of reasons. First and foremost, baby teeth’s structure is similar to adult teeth, meaning they have a very sensitive part called the pulp (or nerve), and considering the lowered mineralization of baby teeth and their small size, decay can reach the nerve pretty quickly, and the pain is quite severe. Also, if this decay is neglected, an infection may develop, and this not only is painful but can adversely affect the growing adult tooth inside the bone.
If the decay becomes so severe that the tooth cannot be saved, it will need to be extracted. Since the jaws are in a constant state of change, this results in the movement of the teeth themselves, and the spaces created by removing the tooth may get closed. As a result, the permanent tooth would not have sufficient space to erupt, and it may get buried (or impacted) and if it does erupt, it will probably erupt in a wrong position, resulting in crooked teeth.

Misalignment of the teeth or jaw can also lead to speech problems, jaw pain, chronic headaches, and TMJ disorder later in life.

How to take care of baby teeth.

As you can see, taking care of your child’s teeth is vital. So how could you take care of your child’s teeth?
Brushing should start as soon as the first tooth erupts in the mouth. A special toothbrush that is really small should be used, along with only a smear of toothpaste to prevent swallowing, and you should rinse his\her mouth as much as you can. The child should be taught to take care of his own teeth as soon as he\she can grip the toothbrush, so at about 1 to 1.5 years of age, and strict supervision is a must to prevent swallowing and injury to the gums and teeth
Now let’s talk about the successors, meaning the permanent teeth.
As stated before, the first permanent tooth erupts at the age of 6 years (which is the first molar) that has no baby tooth before it and erupts behind the already present teeth.
From that moment on, taking care of the teeth is crucial. If most people think that baby teeth are replaceable and therefore don’t need special care, permanent teeth are the exact opposite. These will not fall out and will not be replaced later, meaning you only get one chance to preserve them. If the first permanent molar decays, that means poor care from the child and poor supervision from the parents, and professional intervention will be needed to preserve the other teeth.

How many teeth do we really need?

So how many teeth do we actually need, and do we really need to replace them if they’re lost?
We all know that every adult has 32 teeth, including the wisdom teeth that erupt at the age of 18-25 years. Each tooth serves a specific purpose and has a special need. Although about 80% of the chewing lies on the first molar, the remaining teeth work together as one unit to serve this first molar and help it to do its job right. That means if one tooth is lost, the remaining workload will be distributed on the remaining teeth. This increases the chance of decay, gum disease and even cracks and fractures. So in essence, if you lost one tooth and didn’t care to replace it, you could expect to lose a few more in the following period.
It has also been said that people who have all their teeth live longer. This slogan was used as a marketing tool by dentists for a long time, but recently, studies have shown a direct relation between dental health and general health, such as a strong relationship between gum disease and heart disease, and the effect of gum disease on the eyes and joints has been strongly established. This truly means that if a person takes care of his\her teeth (and therefore not lose any of their teeth) will actually live longer than a person who doesn’t give dental and oral care its proper due.

Tips for keeping your teeth healthy.

The importance of brushing cannot be overstated! It is advisable to brush twice daily and use a Fluoride containing toothpaste as advised by the dentist. Not only that, but brushing technique is also crucial, and you should seek advice from your dentist as to how to properly brush your teeth.

  • Use dental floss, at least 3 times a week and even more if advised by your dentist.
  • Use Fluoridated mouthwash, at least once a day.
  • Watch your diet, not only to make yourself slimmer but also consuming more sugars hastens the decay process and make your teeth more vulnerable to gum disease.
  • Stop your dangerous habits, such as grinding and clenching, and biting on hard objects as nails and pens.
  • Visit your dentist frequently, every 6 months to 1 year, and maybe less if your teeth demand more care.

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