Dental Anatomy – Structural & Functional Facts of Human Teeth

The mouth is the smallest yet the most complex part of our body. Several components work together to help us eat, drink, taste, speak, and swallow the food. Teeth are one of the most crucial aspects of our mouth as they help to maintain the radiant smile. In our lifetime, we encounter two different sets of teeth – one that erupts during childhood is termed as primary dentition. Primary dentition primarily consists of a set of 10 teeth on each jaw.

As the child grows and develops, the permanent set of teeth gradually replaces the baby teeth. Permanent dentition consists of 16 sets of teeth on each arch. Coming to the structure of a tooth, it typically consists of two sections – the crown and the root. Both the parts include two essential dental tissues, namely the dentin and pulp. The difference between the two structures is that the crown is protected by enamel, whereas the root is covered by cementum.

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Our teeth mainly function to tear and breakdown the food into small chewable particles, thereby, making digestion easier.

Moreover, teeth are a critical aspect of our smile. Now that you know the basic terminology let’s take a closer look at the structure and functions of our teeth.

Teeth and its functions

Teeth are the most distinctive features of our body and also the hardest substance in the human body. Typically, the teeth are made from proteins like collagen and minerals like calcium and phosphorus. The prime function of the teeth is to mechanically break down the food by cutting and grinding, which makes swallowing and digestion easier. Typically there are four types of permanent teeth – incisors, canines, premolars, and molars.

Each tooth has a specific function; for example, the incisors cut the food, canines tear the food, the molars and premolars work on crushing the food into smaller pieces. Secondary functions of teeth are mainly concerned with speech and esthetics of the smile.

What are the different types of teeth?

Every tooth in our jaw plays a unique role in the process of digestion. Moreover, they specifically help in speaking. Let’s check out the different types of human teeth –

Incisors

Incisors are the teeth located in front of the mouth. They are the prime centers for aesthetics and smile of a person. Typically, a person consists of four incisors each on the upper as well as the lower jaw. The shape of an incisor resembles small chisels with sharp edges that help to cut or bite the food. For example, incisors help you to eat and cut a piece of apple. In the primary dentition, lower incisors are the first pair of teeth to erupt around six months of age. In the permanent dentition, incisors grow in between the age of six and eight.

Canines

Canines are the cornerstones of the smile. They erupt on either side of the lateral incisors – two in the upper arch and two in the lower arch. Canines are usually characterized by their sharp and pointy surface, which is built to tear the food. Deciduous canines erupt at the age of 16 and 20 months on the upper and lower arch, respectively. Usually, the upper canine grows first followed by lower canine.

Coming to the permanent dentition, the lower canines erupt first around the age of nine years followed by upper canines at the age of 12 years.

Premolars

Premolars are a unique set of teeth that only occur in the permanent dentition. These teeth replace the primary molars on both the upper and lower jaw. Premolars are more prominent as compared to permanent canines and incisors. Anatomically, they have a flat surface with two cusps that help to crush and grind the food into smaller particles. The first set of premolars starts to erupt at the age of ten years.

Molars

Molars are the most prominent and most influential teeth of all other types. Generally, primary dentition consists of four molars on each jaw, whereas, the permanent dentition consists of six molars on each jaw. The two additional sets of molars in the permanent dentition are termed as wisdom teeth. These are the last set of molars that erupt between the ages 18 and 25. These teeth are considered as troubleshooters because of increased risk of impaction or partial eruption. (1)

Such problems arise due to lack of space in the mouth for the growth of third molars. This is the reason why wisdom teeth are frequently extracted. Molars are mainly used to grind the food into small particles.

The tongue plays a significant role in pushing the food particles towards the molars for further breakdown.

What are the different types of dentition?

Usually, we encounter two sets of dentition throughout our life, namely the primary and permanent dentition.

Primary dentition

Primary teeth or milk teeth develop in the babies and erupt around six months of age. However, this period may vary from one child to another. In some cases, the tooth may erupt as early as three months of age while in other cases, it may not erupt until the child is one year old. (2)

An interesting fact about primary teeth is that they always erupt in pairs. The first pair of baby teeth to erupt in the mouth is usually the lower incisors. Primary teeth are temporary and usually, fall out making room for the permanent teeth to erupt in the mouth. Typically, primary dentition consists of 20 set of teeth – ten teeth on each jaw. Each arch consists of –

Children tend to lose their baby teeth between the ages of six and twelve. Molars are the first permanent teeth that erupt in the mouth.

Permanent dentition

The adult mouth typically consists of 32 set of teeth – 16 teeth on each jaw. Each arch consists of the following teeth–

  • Four incisors
  • Two canines called cuspids (3)
  • Four premolars also are known as bicuspids
  • Four molars
  • Two wisdom teeth

Unlike the primary dentition, permanent teeth cannot be replaced. For any reason, if you lose a permanent tooth, you will have to get an artificial replacement of the tooth. Premolars are a new edition in this unique type of dentition. They erupt in the place of primary molars. Often premolars are referred to as the bicuspids due to the presence of two cusps. Third molars erupt much later in life and commonly erupt partially or become impacted.

What is the difference between primary and permanent dentition?

Typically, primary teeth can be differentiated from permanent teeth in three aspects –

Composition

  • Primary teeth appear whiter than permanent teeth – This is because primary teeth have a thinner and translucent layer of enamel as compared to permanent teeth. The thick layer of enamel in permanent teeth gives it a bluish-white color.
  • Thin enamel layer in primary teeth makes it more permeable to plaque and bacteria. Therefore, primary teeth have an increased risk of dental caries and cavity formation as compared to permanent teeth. (4)
  • Fluoride treatments are less useful for primary teeth due to reduced calcification of the enamel. Therefore, primary teeth require more dental attention as compared to permanent teeth.

Structure

Following are the various factors that differentiate primary teeth from permanent dentition –

  • Shapes of the tooth – primary teeth are usually characterized by the bulbous crown and pointed cusps. Moreover, their interdental contact area is smaller as compared to the broad contact areas found in permanent teeth.
  • Sizes of the teeth – Primary teeth are usually smaller in size as compared to permanent teeth. However, primary molars are an exception as they are wider than the permanent premolars.
  • Occlusal surface – Primary teeth have a narrow occlusal table as compared to the full occlusal surface of permanent teeth.
  • Pulp cavity – bulbous crowns in primary teeth have larger pulp cavities. Moreover, they are covered by a less dense layer of dentin. This is one of the prime reason for the increased risk of tooth decay and pulp infection among the kids. Pulp cavities in permanent teeth are comparatively low and small with a thicker dentinal layer.
  • Root structure – roots of primary teeth are short and delicate. The roots of primary molars usually diverge widely. Whereas, the permanent tooth root is long, strong, and non-divergent.

Total number of teeth

Generally, primary dentition consists of 20 teeth – ten teeth per arch, while the permanent teeth consist of 32 teeth – 16 teeth per arch. The eruption time for each tooth varies in both primary as well as permanent dentition. Let’s look at the eruption rate of primary and permanent teeth

Primary teeth chart

Upper arch

ToothEruptionShedding
Central Incisor8-12 months6-7 years
Lateral Incisor9-13 months7-8 years
Canine16-22 months10-12 years
First Molar13-19 months9-11 years
Second Molar25-33 months10-12 years

Lower Arch

ToothEruptionShedding
Central Incisor6-10 months6-7 years
Lateral Incisor10-16 months7-8 years
Canine17-23 months9-12 years
First Molar14-18 months9-11 years
Second Molar23-31 months10-12 years

Permanent teeth chart

Upper Arch

ToothEruption
Central Incisor7-8 years
Lateral Incisor8-9 years
Canine11-12 years
First Premolar10-11 years
Second Premolar10-12 years
First Molar6-7 years
Second Molar12-13 years
Third Molar17-21 years

 Lower Arch

ToothEruption
Central Incisor6-7 years
Lateral Incisor7-8 years
Canine9-10 years
First Premolar10-12 years
Second Premolar11-12 years
First Molar6-7 years
Second Molar11-13 years
Third Molar17-21 years

What are the different parts of a tooth?

tooth anatomy with labels

Typically, a tooth is divided into two parts, namely the crown and the root. Crown is the topmost of the tooth, which is usually exposed to the oral environment. Every tooth has a characteristic shape of the crown, which helps to determine the specific function. For example, the incisors are sharp and chisel-shaped, which makes them efficient in cutting the food.

The root consists of about two-thirds of the tooth structure, which is embedded in the jaw bone. The primary function of the root is to provide support and anchorage to the tooth within the bony socket. Coming on to the structure, the tooth is usually made up of four different layers of dental tissue

  • Enamel – it is the hardest substance in our body and the outermost protective layer of the tooth. Enamel is a mineralized structure made up of calcium and phosphorus. It is also the most vulnerable layer of the tooth, which can be easily damaged by tooth decay. (5)
  • Dentin – next to the thickness of enamel lies the dentin. It is the most sensitive layer of the tooth. Usually, loss of enamel exposes the dentinal layer to the bacterial acids, which can cause severe tooth sensitivity and damage. (6)
  • Pulp – pulp is the central most layer of the tooth, which is formed by a network of nerves and blood vessels. Pulpal tissue maintains the vitality of the tooth. Severe tooth infections with pulp involvement are the primary cause of tooth pain. Such cases undergo root canal treatment.
  • Cementum – cementum is the protective covering of the tooth root. It mainly consists of connective tissue that binds around the root of the tooth. Cementum also provides attachment to the periodontal ligaments to provide support and anchorage to the tooth in the bony socket.

Overview of Dental anatomy

The tooth is one of the essential parts of our mouth. They help to speak, chew, and swallow the food. Additionally, teeth are necessary for a radiant and good looking smile. Typically, there are four types of teeth in our mouth – the incisors, canines, premolars, and molars. Incisors and canines are meant to cut and tear the food respectively while the premolars and molars function in grinding and crushing the food.

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Throughout our life, we encounter two sets of dentition, namely the primary and permanent dentition. Primary teeth or baby teeth usually grow around six months of age and persist until the eruption of the permanent dentition. Usually, the primary teeth are structurally wider and bulbous as compared to permanent teeth. They have a thinner layer of enamel and look whiter than the permanent teeth. However, the functions of each tooth remain the same in both types of dentition.

Each tooth is made up of four different dental layers, namely the enamel, dentin, pulp, and cementum. All these layers built up the tooth structure and provide protection and support to the tooth. Now that you know about the different types of teeth and their anatomy, you may understand their importance in the mouth.

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