What Are the Four Types of Human Teeth and Their Functions?
Teeth are hard, calcified structures in our mouth that help break down food into smaller pieces. Unlike some animals that can swallow large chunks of food, humans need their teeth to cut, tear, and grind food before swallowing. This essential process is supported by jaw muscles and saliva.
Humans have two sets of teeth in their lifetime: milk teeth (also called primary teeth) and permanent teeth (secondary teeth). In total, an adult has 32 permanent teeth, which include a special set called wisdom teeth. In this article, we will explore the different types of teeth, their functions, common types of teeth shapes, and the dental formula of human adults. We will also learn about why wisdom teeth often cause discomfort and how teeth differ across various groups of vertebrates.
Human Teeth Diagram
Different Types of Teeth in Humans
Humans generally have four main types of teeth:
Incisors
Location: Front part of the mouth (upper and lower jaws).
Shape: Thin, blade-like edges.
Function: Cutting food into smaller chewable pieces.
Count in adults: 8 (4 in the upper jaw and 4 in the lower jaw).
Canines
Location: At the corners of the dental arch.
Shape: Pointed and sharp.
Function: Tearing and gripping food, especially tough foods like meat.
Count in Adults: 4 (2 in the upper jaw and 2 in the lower jaw).
Premolars
Other Name: Bicuspids.
Location: Behind the canines.
Shape: Flat biting surface with ridges.
Function: Crushing and grinding food.
Count in Adults: 8 (4 in each jaw, two on each side).
Molars
Location: At the back of the mouth.
Shape: Wide and flat biting surface.
Function: Grinding food into smaller particles for swallowing.
Count in Adults: 12 (6 in each jaw, including 4 wisdom teeth).
These four types of teeth and their functions help us handle different kinds of foods effectively.
Dental Formula of Human
A dental formula is a shorthand way to describe the number of each type of tooth in one half of the jaw (upper or lower). For adults, the dental formula of human teeth is:
2 (Incisors) : 1 (Canine) : 2 (Premolars) : 3 (Molars)
This is often written as 2.1.2.3 / 2.1.2.3, indicating the upper and lower halves of the jaw. Thus, for one half of the jaw, there are two incisors, one canine, two premolars, and three molars. When multiplied by four (both sides of the upper and lower jaw), the total comes to 32 permanent teeth.
Children have 20 milk teeth, which follow a simpler formula of 2.1.0.2 / 2.1.0.2, reflecting the absence of premolars in primary dentition. As the child grows, these milk teeth are replaced by permanent teeth.
Shapes of Teeth
We can also talk about types of teeth shapes and why they matter:
Incisors: Chisel-shaped edges for slicing through soft or moderately firm foods.
Canines: Cone-shaped and pointed for ripping and tearing.
Premolars and Molars: Broad surfaces and multiple cusps for crushing and grinding.
These shapes help us eat a variety of foods, from leafy vegetables to tougher meats.
Role and Functions of Teeth
Digestion: Teeth start the mechanical process of breaking down food.
Speech: Teeth help in pronouncing certain sounds clearly.
Facial Structure: Healthy teeth support facial muscles and maintain natural contours.
Teeth are made mostly of dentine and covered by the hardest substance in the body, enamel. Though enamel is very strong, it does not contain living cells. Hence, damaged enamel cannot repair itself naturally.
Wisdom Teeth
Wisdom teeth, also called third molars, typically appear between the ages of 17 and 25. They are considered vestigial because many people do not need them to chew effectively. Often, wisdom teeth grow in awkward positions or only partially emerge, leading to problems such as:
Pain and swelling
Jaw stiffness
Infection due to trapped food or bacteria
Many dentists recommend removing problematic wisdom teeth to avoid long-term complications.
Diphyodonts vs Polyphyodonts
Humans are diphyodonts: we have two sets of teeth in our lifetime – milk teeth (20) and permanent teeth (32).
Some animals, like geckos and fishes, are polyphyodonts, meaning they can replace teeth continuously throughout their life. Among mammals, elephants, kangaroos, and manatees can also replace their teeth multiple times, making them polyphyodonts.
Additional Information
Variation in Wisdom Teeth: In some people, wisdom teeth may never emerge or might be fewer in number.
Mixed Dentition: Around 6 to 12 years of age, children have a mix of milk teeth and newly erupting permanent teeth.
Enamel Care: Since enamel cannot repair itself, brushing twice a day with fluoride toothpaste, flossing, and regular dental check-ups are essential.
Quick Quiz (With Answers)
Test your understanding with this short quiz:
1. Which type of tooth is used mainly for cutting food?
A. Canines
B. Incisors
C. Molars
D. Premolars
Answer: B (Incisors)
2. How many premolars does a typical adult have?
A. 4
B. 8
C. 10
D. 12
Answer: B (8)
3. Which set of teeth appears between the ages of 17 and 25?
A. Milk Teeth
B. Premolars
C. Wisdom Teeth
D. Incisors
Answer: C (Wisdom Teeth)
4. Which of the following animals are considered polyphyodonts?
A. Elephants
B. Humans
C. Lions
D. Horses
Answer: A (Elephants)
Related Topics
FAQs on Types of Teeth in Humans: Names, Shapes & Key Functions
1. What are the four main types of teeth in humans and their primary functions?
Humans have four different types of teeth, each specialised for a specific role in the process of mastication (chewing). These are:
- Incisors: The eight sharp, flat teeth at the front of the mouth used for cutting and biting food.
- Canines: The four pointed teeth next to the incisors, used for tearing and ripping tough foods like meat.
- Premolars (Bicuspids): The eight teeth with flat surfaces behind the canines, responsible for crushing and grinding food.
- Molars: The twelve largest teeth at the very back of the mouth, including wisdom teeth, designed for the final, intensive grinding of food before it is swallowed.
2. What is the difference between the number of teeth in children and adults?
The primary difference lies in the two sets of teeth humans develop. Children have a set of 20 primary teeth, often called milk or baby teeth. As they grow, these are replaced by a larger set of 32 permanent teeth in adults. The adult set includes 8 premolars and up to 4 more molars (wisdom teeth) which are not present in the primary dentition, accommodating the larger jaw and a more varied diet.
3. How does the unique shape of each tooth type directly relate to its function?
The structure of each tooth type is perfectly adapted for its function:
- Incisors are thin and blade-like, acting like a chisel to provide a clean, sharp cut when biting into food.
- Canines are sharp and conical (pointed), which provides the necessary grip to tear fibrous or tough foods.
- Premolars have a broader, flatter surface with two cusps, making them a transitional tooth ideal for both tearing and crushing.
- Molars possess large, wide surfaces with multiple cusps and ridges, acting like a mortar and pestle to powerfully grind food into small, digestible particles.
4. Why do humans have two separate sets of teeth in their lifetime?
Humans are described as diphyodont, meaning they grow two sets of teeth. This is a biological necessity tied to growth. The first set of 20 primary teeth is smaller and fits within a child's small jaw. As the jaw grows into its adult size, a smaller set would be inadequate for proper chewing and would leave large gaps. Therefore, the primary teeth are shed and replaced by a larger, stronger set of 32 permanent teeth that are correctly sized for the adult jaw and are built to last a lifetime.
5. What does the adult human dental formula 2123/2123 represent?
The human dental formula is a scientific way to represent the number and type of teeth in one half of the jaw. For a human adult, the formula 2123/2123 signifies that in one quadrant (e.g., the upper right side from the centre to the back), there are:
- 2 Incisors
- 1 Canine
- 2 Premolars
- 3 Molars
6. Do all adults have 32 teeth?
While a full set of permanent teeth is 32, not all adults have this number. The final set of four molars, known as wisdom teeth, often emerge in late adolescence or early adulthood. Due to evolutionary changes in jaw size, many people lack sufficient space for these teeth to erupt properly. This can lead to them becoming impacted or causing other dental issues, resulting in their surgical removal. Consequently, it is very common for an adult to have only 28 teeth.
7. What is the fundamental difference between premolars and molars?
Although both are used for grinding, the key differences are their position, size, and presence in dentition sets. Premolars are located just behind the canines and are smaller than molars. Adults have eight premolars, and they are only found in the permanent set of teeth; there are no premolars in the primary (baby) set. Molars are the largest and strongest teeth located at the back of the jaw for heavy-duty grinding. While the primary set has eight molars, the permanent set has twelve (including wisdom teeth).
