Types of Teeth

Teeth are one of the essential parts of the human body. They participate in many activities of the human body. Their importance can even be measured by the fact that they come to the first step when it comes to the digestive process. In general, we all know that they help chew food. But there are different types of teeth, and each tooth has its specific function. Therefore, it is important to know about different types of teeth.

Here, we are discussing various types of teeth and their definition. We will also learn about the total number of teeth in humans. Before we discuss different types of teeth, let us first understand about teeth with the help of the definition:

What are Teeth?

The teeth are defined as rigid calcified structures in the human body composed of proteins (e.g., collagen) and minerals (i.e., calcium). Because teeth are known for their strong structure, they help us chew the hardest and toughest foods. Besides, they help us speak clearly and smile properly. Teeth also have a big role in shaping the human face.

The teeth are composition made up of four layers, such as:

• Enamel: It is the first and outermost layer of each tooth. Also, it is the most rigid substance in our body.
• Dentin: It is the second layer and comparatively softer than enamel.
• Pulp: It is the third and deepest layer inside each tooth. This layer mainly has nerves and blood vessels.
• Cementum: This layer is formed at the root of each tooth and lies beneath the gums.

Types of Teeth

The teeth usually have different shapes, and each tooth has a specific function in the process of mastication (chewing). This ultimately helps in proper digestion. To fulfill its purpose properly, the teeth are positioned at a particular location according to their purpose.

In humans, there are mainly four different types of teeth, which are listed below:

• Incisors
• Canines
• Premolars
• Molars

Let us understand each type in detail:

What are incisors?

Incisors are the teeth that are located on the front side of our mouth. They are generally the first type of teeth that grows in humans. We can notice the starting development of these teeth in babies at about six months old. However, they come under the milk teeth. The adult set of these teeth usually erupt at the age of around 6 to 8 years. By naturally, these teeth appear in both the above and lower jaw, such as four in the above jaw and four in the lower jaw in our mouth.

Incisors typically have small chisel shapes. Besides, they are flat and include sharp edges to cut foods into small parts so that other teeth could chew. For instance, when we sink our teeth into something like we try to eat the whole apple, we most commonly use incisor teeth. They are also known as anterior teeth.

What are canines?

Canines are the teeth that sit next to the incisor teeth. In other words, they are located at the corners of the dental arch in a human mouth. In children, the initial type of canines (baby canines) usually start to appear at the age of between 16-20 months. In particular, there are four canines in a human mouth. In the case of babies, the upper canines grow first and then the lower canines. Besides, the adult canines follow the opposite way, and they first appear in the lower jaw (usually at the age of 9 years), followed by the upper jaw (usually at the age of between 11 to 12 years).

In terms of shape, canine teeth are more similar to fangs. Furthermore, they are sharp, elongated and have a pointy surface. The primary function of canines is to grip foods and tear them. For fulfilling this purpose, they are characteristically the longest type of teeth in humans. They are also known as eye teeth and cuspids.

What are premolars?

Premolars have a bigger size as compared to incisor teeth and canine teeth. These teeth appear behind the canines. Babies and young children don't get premolars teeth. In other words, these teeth are not grown as the milk teeth. They are the secondary or permanent types of teeth that replace the set of baby molars. These teeth usually start growing at the age of 10 or 11 years old. In particular, there are eight premolars in a human mouth. Once they start coming, we can notice four premolars in the upper jaw, followed by the four in the lower jaw. More specifically, there are two premolars in each quadrant of a human mouth.

Premolars are further subdivided into the first and second premolars. The one located nearest to the midline is known as the first premolar, whereas the one located farthest from the midline is known as the second premolar. In terms of shape, the premolars usually have a ridge structure with a flat surface. The premolars are the traditional teeth designed mainly for grinding and crushing foods into smaller parts. Since Premolars generally have 3-4 cusps, they are also called bicuspids.

What are molars?

Molars have the biggest size, and they are the strongest types of teeth in humans. They are situated in the back portion of the human mouth. There are 12 molars in adults, three on each side of the upper jaw and the lower jaw. These 12 molars also include the four wisdom teeth. Despite four wisdom teeth, eight primary molars appear in children. They are generally sub-divided into 6-year and 12-year molars according to their grown sizes.

Once fully grown, molars are named the first molars, second molars, and third molars based on their placement and the midline distance. However, some people don't get fully developed third molars. Molars typically have a large, flat-biting surface designed to sustain the force used for grinding food. When we eat, our tongue pushes the food into the back of our mouth. Then, molars help chew and grind the food into parts small enough for us to swallow easily.

Wisdom Teeth: Wisdom teeth are the last set of teeth that commonly erupt between the ages of 18 and 25 years. These four molars are located at the end of the teeth' row in the furthest four corners of our mouth. That is why they are also known as the third molars. The wisdom teeth do not usually erupt properly in most people. They may either erupt partially sideways or may remain unerupted inside the bone and never appear in the mouth.

It is suggested by most dentists to remove wisdom teeth as soon as possible in case they have been impacted. Although impacted wisdom teeth may not cause sudden issues, they may get infected over time. This can result in damaging the adjacent teeth or cause several other oral health issues. Additionally, it isn't easy to keep them clean because they sit far back in the mouth.

Number of Teeth in Humans

The number and type of teeth in a person change according to their age. Generally, a human gets two sets of teeth during his or her entire life - primary or baby teeth and permanent or adult teeth.

Children are born without teeth. However, teeth start to appear as soon as children start to wean. Children usually have 20 teeth, called primary, temporary, or milk teeth. They include the same ten teeth in the upper and lower jaw:

• Eight incisors: Four in the upper jaw and four in the lower jaw
• Four canines: Two in the upper jaw and two in the lower jaw
• Eight molars: Four molars in the upper jaw and four in lower law

Most adults by the age of 21 get their complete set of teeth (32 teeth) combining permanent or secondary teeth:

• Eight incisors: Four in the upper jaw and four in the lower jaw
• Four canines: Two in the upper jaw and two in the lower jaw
• Eight premolars: Four in the upper jaw and four in the lower jaw
• Twelve molars: Six in the upper jaw and six in the lower jaw, including the wisdom teeth

Diphyodonts vs Polyphyodonts

Humans and many mammals, including geckos, reptiles, and vertebrates, are referred to as diphyodonts because they typically possess two sequential sets of teeth during their lifetime, including milk teeth and permanent teeth. The remaining vertebrates, such as toothed fishes, are referred to as polyphyodonts because their teeth are constantly replaced overtime in their lifetime. The elephants, manatees and kangaroos are the only mammals that are polyphyodont.