How Many Teeth Do We Have?

Overview: Anatomy & Function of Teeth

​​Teeth help a person eat, speak, and smile. Each tooth type has a name and serves a specific function. They are made up of four different layers, including enamel, dentin, pulp, and cementum:

  1. Enamel is the hardest substance in the body. It is on the outside of the tooth. 
  2. The second layer of the tooth is dentin. Dentin is softer and darker than enamel.
  3. The deepest layer inside the tooth is the pulp. The pulp consists of nerves and blood vessels.
  4. The cementum is on the root of the tooth and is located below the gums.

The number and kinds of teeth a person has changes as they grow older. 

Usually, people have two sets of teeth during their life. These are primary baby teeth and permanent adult teeth.

In adult teeth, the incisors are used to cut food. The canines are for tearing and grasping food. The premolars are for crushing and tearing food, while the molars are used to help you chew and grind food.

How Many Teeth Do Kids Have?

Children have 20 baby or primary teeth. Primary teeth first start to erupt when babies are around six months old. Children typically get all their primary teeth by age three.

Primary teeth gradually fall out, and adults can end up with up to 32 permanent teeth. In some circumstances, permanent teeth push the baby teeth out. However, typically, permanent teeth come through the gums at the back of the mouth behind the last primary tooth in the jaw.

When Does a Child’s First Tooth Erupt?

Your child will begin to grow teeth around 6 months of age. This will continue until around the age of 3. However, each child will grow and lose teeth on their timeline.

Your child should lose all their baby teeth by the time they are 12 years old. When teenagers are about 17 years old, they may develop wisdom teeth, resulting in 32 adult teeth. 

As the age at which teeth erupt differs from child to child, parents and caregivers should not worry if their child’s teeth do not precisely follow the patterns above.

Check with your child’s dentist if they have a delay of longer than one year. Dentists can perform X-rays to ensure that adult teeth are present and developing correctly.

Some children are congenitally missing a tooth or have a supernumerary (extra) tooth, causing them to have less or more than the average number of teeth. 

When Should Dental Exams Start?

According to the American Academy of Pediatric Dentistry (AAPD), dental exams should begin as soon as the first tooth appears. When this occurs, begin brushing your child’s teeth daily and arrange a dental appointment. In most circumstances, children should visit the dentist by their first birthday.

When Should a Child Begin Losing His/Her Primary Teeth? 

Compared with when your child’s teeth first appeared, losing them can be a more straightforward process for parents. While teething may be uncomfortable, incoming molars may be particularly painful for babies and toddlers.

However, the primary molars, known as the first molars, are not usually painful when they fall out or are replaced by permanent molars. These primary first molars are usually lost between the ages of 9 and 11.

When Do Permanent Teeth Start to Grow in? 

The first permanent teeth to grow through the gums are the six-year molars. They are called six-year molars because they typically erupt when a child is around six years old.

The first baby teeth to shed are the lower central incisors. The adult central incisors typically erupt around the same time as the first permanent molars around age six to seven.

Usually, people lose all their baby teeth by around the age of 12.

How Many Permanent Teeth Do Adults Have? 

Most people begin adulthood with 32 teeth, including the wisdom teeth. There are four types of teeth. Each plays an essential role in how you eat, drink, and speak.

The different types include:

  • 8 incisors: These are the chisel-shaped teeth used to cut up food.
  • 4 canines: These pointy teeth enable you to tear and grasp food.
  • 8 premolars: The two points on each premolar tooth allow you to crush and tear food.
  • 12 molars: Multiple points on the top surface of molar teeth help you chew and grind food.

Is Having Less Than 32 Permanent Teeth Normal?

Hypodontia is a developmental problem in which six or fewer permanent teeth do not develop. Hypodontia is typically an inherited trait, but environmental factors during tooth development can also play a role.

When more than six permanent teeth are missing, this is known as oligodontia. A total absence of missing teeth is called anodontia.

Hypodontia is one of the most common development oral health problems. Missing wisdom teeth is the most prevalent, followed by missing premolars, upper lateral incisors, and lower central incisors.

What Causes Missing Permanent Teeth? 

There is a strong genetic influence in hypodontia. Hypodontia may result from complex interactions between genetic and environmental factors.

The following may also lead to missing permanent teeth:

  • Advanced maternal age
  • Low birth weight
  • Maternal smoking
  • Incidences of rubella

Other hormonal, environmental, and infectious conditions may also link to missing teeth. Hypodontia is more common in women than men and occurs at a higher than average rate in identical twins.

How to Treat Missing Permanent Teeth

There are many effective ways to treat missing permanent teeth, including:

  • Implants
  • Dental prosthetics
  • Orthodontic braces and appliances

Removable partial dentures or fixed porcelain ceramic bridges can fill in spaces left by missing teeth to improve the look of a smile. Braces can often help realign the teeth to close the gap, but this may require reshaping adjacent teeth.

When the gaps between teeth are small, it may be possible to close them by bonding tooth-colored fillings to the teeth on either side of the space. 

Dental implants are another treatment for adults with healthy gums and jawbones. Dental implants are placed below the gums in your jawbone. 

As their jaws are still growing, children are not suitable candidates for dental implants. Dentists may suggest preserving the existing baby tooth for a child with permanent tooth hypodontia.

With no underlying adult tooth to push the primary tooth out of place, a baby tooth can sometimes stay in the mouth for a lifetime when cared for properly.

If preserving the primary tooth is impossible, the dentist may try to close the space with braces. In these circumstances, braces draw an existing tooth into the space. This helps to reshape the tooth to resemble the absent tooth.

The timing of treatment can be essential when planning for and managing missing permanent teeth in kids. It is crucial for your child to visit a dentist regularly and for the dentist to keep you updated about treatment timing and options.

What are Persistent Teeth? (+ How to Treat Them)

Persistent teeth refer to the delayed loss of baby teeth. The most prevalent reason for persistent teeth is because permanent teeth are absent. This condition is also known as tooth agenesis, characterized by a partial or complete absence of permanent teeth.

Another reason for persistent teeth is ankylosis. This is when the root of the primary tooth is fused to the bone. Lower teeth are ankylosed more than twice as often as upper teeth.

Other reasons for persistent teeth include infection, trauma, and impacted permanent teeth. If your child’s primary teeth have not shed when expected, it is best to speak with your child’s pediatric dentist and an orthodontist. 

If the crown, roots, and alveolar bone of the persistent baby tooth is in good condition and are not causing any structural or aesthetic issues, then the baby tooth can be retained.3 It may even serve well into adulthood.

However, if your child’s tooth is ankylosed, the orthodontist may suggest that the tooth is extracted. 

This depends on the following, among other factors: 

  • Age of the onset of ankylosis
  • The affected tooth's location
  • Child’s smile line

When Do Wisdom Teeth Start Erupting? 

Wisdom teeth are otherwise known as third molars

Third molars are the last permanent teeth to erupt. Wisdom teeth typically erupt between the ages of 17 and 25. However, wisdom teeth can erupt many years later.4

Should Wisdom Teeth Always Be Removed? (+ Best Age) 

Wisdom teeth may not need to be removed if they are:5

  • Healthy
  • Grown in completely (fully erupted) 
  • Positioned properly and biting correctly with their opposing teeth 
  • Able to be cleaned daily

However, in many circumstances, wisdom teeth do not have room to grow correctly and can cause issues. Erupting wisdom teeth can grow at many angles in the jaw, even horizontally, and cause dental problems like infection or pain.

The decision to remove wisdom teeth is not always clear. Speak with your dentist or an oral surgeon regarding the position and health of your wisdom teeth for advice.

Most commonly, wisdom teeth extractions are suggested between the ages of 18 and the early 20s.

Tips for Taking Care of Your Teeth

It is easy to keep your mouth and teeth healthy. A simple oral hygiene routine can help prevent most dental issues.

Always brush your teeth before bed at night, and at least one other time during the day with fluoride toothpaste. Spit out the toothpaste after brushing and do not rinse so that the fluoride remains on your teeth for longer.

You should also clean between the teeth with dental floss or interdental brushes. Try to avoid sugary drinks and foods, too. Regular dental check-ups are also essential every 6 months to a year. 

While most people brush their teeth regularly, many people do not floss or attend regular dental check-ups. A few small adjustments in your daily routine can make a significant difference in the long term. During a dental check-up, your dental team can remove any build-up on your teeth and address any gum disease that has already developed.

Resources

Taking Care of Your Teeth and Mouth, National Institute on Aging (NIH), March 2020

Aktan, Ali Murat et al. “An evaluation of factors associated with persistent primary teeth.” European journal of orthodontics vol. 34,2 (2012): 208-12

Retained Primary Molars and Related Reasons in Umm Al-Qura University, Makkah: A Retrospective Study, The Open Dentistry Journal, May 2019

Renton, Tara, and Nairn H F Wilson. “Problems with erupting wisdom teeth: signs, symptoms, and management.” The British journal of general practice : the journal of the Royal College of General Practitioners vol. 66,649 (2016): e606-8

Wisdom teeth removal: When is it necessary?, Mayo Clinic, December 2016

Zimmerman B, Jenzer AC. Physiology, Tooth. [Updated 2021 Jun 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan

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