Teeth – Anatomy, Structure, Types & Functions

Teeth are the most valuable thing that makes your smile beautiful. To have a pleasant smile, you must protect your teeth. Teeth are the hard, calcified structures seen in the jaws (or mouths) of several vertebrates. Teeth lie in the oral cavity along with the other parts of the mouth. The major function of teeth is to break down food for better digestion. Let’s have a look at the tooth’s anatomy and structure. 

Teeth

The teeth are hard and resistant structures that are part of your digestive system. They are positioned on the jaws, in or around the mouth, and in the pharynx regions of vertebrates. They help break down the foods by simply crushing them before they are swallowed. Most humans have 32 teeth, while some have more or fewer than 32. Tooth enamel is the hardest substance in the human body and acts as the protective outer layer of your teeth. Among the 32 permanent teeth, it contains eight incisors, four canines, eight premolars, and 12 molars. Proper maintenance of teeth is vital for ensuring overall oral hygiene.

Teeth Structure

Teeth are hard mineral calcium phosphate structures in the oral cavity. Teeth in humans are heterodont, which means they are more than one. The human teeth embedded in the upper jaw (maxilla) and lower jaw (mandible) are diphyodont. That means they have two generations of teeth during their lifespan, which are 20 deciduous (primary) teeth and 32 permanent teeth. Human teeth are divided into four types namely, incisors, canines, premolars, and molars.

The two types of incisors (i.e., central and lateral) and two types of molars (i.e., first and second) make up the primary dentition. 

The successional permanent incisors, canines, and premolars replace the incisors, canines, and molars in the primary dentition.

The extra teeth, like the three types of molars (i.e., first, second, and third), are included in the permanent dentition.

The two main structures of teeth are the crown (the part above your gums) and the enamel (a hard and protective substance that covers your tooth crown). The root is the invisible part that helps hold the tooth in your jaw. It is usually covered by your gums. The root gripply holds your tooth with your periodontal ligament. The other structures of the teeth are:

Enamel: It is the hardest tissue that covers the surface of the dental crown. The enamel contains 89% mineral carbonate-substituted hydroxyapatite arranged in interlocking patterns, giving it its characteristic ability. Enamel is the hardest substance in the human body and is the protective outer cover of each tooth. It shields your teeth from cavity-causing bacteria. 

Dentin: The layer underneath your enamel is called the dentin. Dentin inside the enamel and cementum is the tissue that forms the tooth from the dental crown to the tooth’s root. Dentin is much softer than enamel. The dentinal tubule is a small tube containing tissue fluid that runs inside the dentin.

Dentin decides the size and shape of a tooth. Dentin consists of 60% minerals by weight and 20% organic components. The structure of dentin can ease out and absorb the thrust, permitting it to work as a substructure for enamel. But dentin isn’t as hard as enamel. So, the cavity risk increases if the enamel misses and dentin is seen out.  

Cementum: Cementum is the tissue that connects the alveolar bone and the tooth through the periodontal ligament. This tissue is harder than the bone and covers the surface of the tooth root. It anchors your tooth firmly in your jaw, along with your other periodontal tissues.

Dental pulp: The dental pulp comprises the blood vessels, lymph vessels, connective tissues, and nerve fibres. The tissue, also called the nerve, supplies nutrients to the dentin. The tooth pulp is the innermost layer of your tooth.

Periodontal ligament: The periodontal ligament is the soft connective tissue that serves as the lining of your tooth socket. Periodontal ligament It stops the force directly given to the tooth from being applied to the alveolar bone at the time of chewing the food. It is the tissue made up of fibrous tissue that helps connect the tooth root and the alveolar bone.

Alveolar bone: The alveolar bone is the place where the tooth is installed. It is the jaw bone supporting the tooth. The tooth gets loose if a large portion of the alveolar bone gets destroyed by any periodontal disease or other causes.

Gingiva: Gingiva, also called “gum,”  is the soft tissue that covers the alveolar bone.

Gingival sulcus: Gingival sulcus simply refers to the small space between the tooth and the gums. Even in people with genitals, there is a space of 1 to 2 mm, even in the healthy teeth. However, this space gets deeper because of the inflammation, and then it is known as the periodontal pocket or gingival pocket.

Teeth Anatomy

The specialised tissues in the tooth survive the forces of mastication while restoring the retention of the oral cavity. The specialised tissue called pulp, present at the core of the tooth, contains the nerves, blood vessels, odontoblasts, fibroblasts, and an extracellular matrix, which gives the tooth its neurosensory function and reparative potential. 

The cementum connects to the periodontal ligament, which is connected to the alveolar bone. This functions as a connection system to keep the tooth in place, overcoming the mastication forces. Teeth anatomy can be divided into two main parts: the crown and the root.

Crown

The crown of the tooth is the visible part of the oral cavity. The tooth’s crown has five surfaces.

1. The facial surface for incisors and canines, which is the surface facing the lip or cheek. Then, the buccal surfaces are used for premolars and molars.
2. The surface facing the mouth’s interior is called the palatal surface in the maxilla and the lingual surface in the mandible.
3. The surfaces, which are the boundaries of adjacent teeth, are known as mesial and distal. 
4. The surface closer to the midline of the face is called mesial, and the surface away from the face’s midline is called distal.
5. The occlusal surface refers to the biting surface.

Root

The root is enclosed into the bony ridge of the upper and lower jaws, called the alveolar process, through a connection to the periodontal ligament. The border of the alveolar process is enclosed by the gingiva, which is adjacent to the teeth.

At the root apex, the apical foramen acts as the neurovascular structure that enters the tooth and goes up the root canal to the extended pulp chamber of the crown. The type of tooth determines the variation in the roots of the tooth. The molars comprise the three roots. They are a lingual root on the lingual aspect, a mesiobuccal root, and a distobuccal root on the buccal aspect.

The cementoenamel junction is the anatomical boundary that exists between the enamel-covered crown and the cementum-covered root. Dentin forms the core of the whole tooth, which encircles the pulp, which has the neurovascular structures.

What are the four types of teeth?

In general, there are four types of permanent teeth in humans. Those teeth are:

1) Incisors

For many people, the four incisors will be on the upper jaw and the other four on the lower jaw. They are the front two teeth and the teeth on either side of them. Each incisor has a single narrow edge in each incisor, which helps crush the food you eat. Incisors are the visible teeth in your mouth. 

2) Canines

Canine teeth are sharper than other types of teeth. Canine teeth help tear foods like chips, meat, and crunchy vegetables. Many people have four canine teeth, one in every quadrant (upper right, upper left, lower right, and lower left). As they are directly under your eyes, canines are sometimes called “eye teeth.”

3) Premolars

Premolar teeth have the characteristics of both canines and molars. Premolars stand between your canines and your molars on the back of your mouth. Also called bicuspids, premolars help tear, crush, and grind food into smaller particles.

4) Molars

Molars help with 90% chewing, supporting the crushing and grinding of your food. The molar teeth lie in the back of your mouth, and many adults have 12 molar teeth in the format of three in each quadrant. The wisdom teeth (third molars) are included in the molar teeth. You might have eight molars altogether if your wisdom teeth were removed or if you were born without them. 

How do teeth function?

Human teeth help with digestion. The human teeth work together to break, mix, and grind the food you eat into smaller pieces. They help chew and grind the food properly. Then, your tongue and oropharynx (the upper part of your throat) convert the food into a small ball for easy swallowing.

Though they seem to be more like bones, teeth are actually ectodermal organs. Other ectodermal organs include your hair, skin, and sweat glands.

Teeth numbers

The numbering systems are used by dentists and other healthcare providers to label the teeth. Mostly, the Universal Numbering System is used to number the teeth.

Universal Numbering System for adult teeth

According to the Universal Numbering System, starting from the upper-right third molar, a number from 1 to 32 is assigned to each adult tooth. You start towards your two front teeth and then go to the left side. After you count #16 (your upper-left third molar), then you move down and begin with #17 (your lower-left third molar).

Now, numbering across your lower teeth, you stop at #32 (your lower-right third molar). Yet, dentists give numbers to the missing teeth to provide an accurate tooth chart for your records. 

Universal Numbering System for baby teeth

The universal numbering system used to label primary (baby) teeth uses letters instead of numbers. The baby teeth are labelled from A to T, starting with the upper-right molar. By counting the upper teeth, you will see #J as the upper-left molar. On counting on the lower part, #K will be the lower left molar, and #T will be the lower right molar.

Conclusion

Though the structure and anatomy of each part of the human body are complicated to understand, they are interesting to learn. One such part of the body is the tooth, which is a welcome guard in your mouth. Teeth are hard structures mostly made up of calcium. Their primary function is to break down the food we eat to aid in digestion. The structure of the mouth is also decided by the teeth. So, it is important to protect your teeth from all types of oral issues.

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