6 interesting facts about different layers of the teeth

Layers of the teeth

Human teeth are not just ceramic-like blocks for breaking down the food, but nature has intricately designed them to perform several functions in the mouth. Every tooth has three distinct layers, and every layer is unique and has peculiar features. In this article, I will walk you through the distinctive characteristics of different layers of teeth.

Let’s get started:

different layers of the teeth

There are three layers of the teeth; enamel, dentin, and pulp. The following are the characteristic features of each layers:

Enamel (an outer, white layer on the teeth) 

Dental enamel forms the outer, thin, and hard protective layer on the teeth. It insulates the teeth from hot, cold, chemical, and physical insults throughout the day. 

The calcium and phosphate minerals make up 96% of the enamel structure, making it the hardest structure in the body. The remaining 4% is water and organic matrix, such as collagen fibers. 

The calcium and phosphate ions are arranged in a specific order extending in several directions, forming a hexagonal (six-sided) crystal that resembles the shape of a prism. These calcium phosphate crystals are known as hydroxyapatite crystals. 

The hydroxyapatite crystals are tightly packed in a bundle, with all the crystals oriented in the same direction forming a rod-like structure. Millions of these microscopic rod-like structures run from the dentin to the tooth’s surface. 

A prism: A Hydroxyapatite crystal resembles a prism and reflects light.

A few interesting facts about enamel

1: Enamel is colorless then why do teeth appear white

The crystal orientation in enamel makes it colorless, translucent, and capable of reflecting light from the underneath dentin. The shade and thickness of dentin determine the color of your teeth. The colors of dentin can vary from off-white, grey, to yellow. 

In young people, teeth appear bright, white and light because of the thin dentin and pinkish hue from the blood lying in the tooth’s core. As you age, the teeth get darker because of increased dentin thickness and shrunken pulp in the teeth.  

2: Teeth can sustain 120kg of force in one bite

A human jaw can exert up to 120 kg of force in a single bite. Thus, it requires teeth to be strong enough to bear these stresses.

The enamel, along with dentine, provides enough strength to the teeth to sustain these stresses day in and day out. 

Dentin (hard, yellow layer on the teeth)

Dentin lies between the enamel and pulp and forms the bulk of the tooth. It is seen as a yellow layer on the teeth if the enamel is lost.

Unlike enamel, dentin is porous and has fluid-containing tiny channels that connect enamel with the pulp.

[The toughness of the layers of the teeth goes down as we go deeper into the teeth].

The tiny channels or tube-like structures in dentin are called dentinal tubules that run from the pulp to the enamel. The dentinal tubules are tracks created around the long tail of the dentin-producing cells. These cells are lined up at the junction of dentin and pulp.  

A few nerve endings from the pulp also penetrate to some length in these tubules.

The dentin is comprised of 65% minerals and 35% collagen fibers and water, which makes it alot flexible than enamel.

A few interesting facts about dentin

1: Tooth sensitivity due exposure of dentinal tubules to the environment

The sensitivity we experience in the teeth is due to dentin exposure to the environment. The fluid movement in exposed dentinal tubules triggers the nerve endings penetrating the tubules causing pain or sensitivity in the tooth.

Over time, the exposed ends of the dentinal tubules are blocked by calcium, phosphate, fluoride salts, decreasing the overall sensitivity in the tooth. 

2: Teeth become darker with age

The teeth become darker as you get older because new dentin is laid down in the pulpal space, pushing the pulp further in the tooth whenever it anticipates that it’s under bacterial attack, injury or dentin has been exposed to the environment.

After the new increments of dentin are laid down, the enamel reflects light from the thicker yellow or grey dentin, turning teeth one to two shades darker.

Pulp (located in the core of the teeth)

Layers of the teeth

Pulp is soft and is found the core of the tooth. It is composed of dense network of several blood vessels and nerves. The dentin-forming cells lie at the dentin and pulp interface and are responsible for the dentin repair when needed.

An interesting fact about pulp

Cavities or bacteria reaching the pulp tissue irreversibly damages the tooth

During the process of tooth decay, when the bacteria reach the pulp tissue, they destroy the cells and fibers of the pulp, leading to an irreversible damage that’s is beyond repair.

At this stage, the tooth can not be restored with a filling and requires a root canal therapy (RCT). RCT involves removal of infection, nerves, and blood vessels, and filling it with a biologically safe material.

Cementum (covers the root dentin)

The cementum covers the root portion of the dentin. The roots of the teeth are covered by gums and don’t require a rigid layer like enamel to protect them.

Cementum is less rigid than enamel and thus doesn’t provide necessary protection to the teeth if roots get exposed in the mouth. 

An interesting fact about cementum

Tooth sensitivity following root exposure

You may experience sensitivity in teeth if the gums lose grip on the teeth and recede. The root cementum is not as strong as enamel to protect teeth from hot, cold and others insults and any exposure to these stimuli elicits a sharp pain or sensitvity in the teeth.

FAQ’s

Is dentin harder than enamel?

No, dentin is softer than enamel. The higher mineral content in enamel and the lower quantities of organic matrix and water make it harder than dentin. 

layers of the teeth
The table shows the composition of enamel and dentin by volume.

What is dentin, and what is its function in teeth? 

Dentin is the second layer of the tooth. It lies below the enamel. It supports the thin enamel. Its elasticity allows teeth to bend a little during movement. 

Does dentin grow back?

Dentin has a limited capability to grow back. The bulk of dentin destroyed due to tooth decay can’t grow back and is replaced by filling. 

Deep fillings near to pulp require a thin layer of calcium hydroxide cement that is known to stimulate dentin formation. The dentin-forming cells in the superficial layer of the pulp, calcium, and alkaline environment provided by the cement allow dentin bridge formation below the cement base. The new dentin is porous and irregular and takes six months to form. 

What happens if dentin is exposed?

Your teeth become sensitive as a result of dentin exposure. The enamel protects the underlying layers from the harsh oral environment. 

Dentin comprises of network of tiny tubes known as dentinal tubules that run from the pulp toward the enamel and are filled with fluid. The nerve fibers also extend to some distance in the tubules from the pulpal end. The movement of fluid due to dentin exposure causes sensitivity in teeth.

Which layers of the teeth are sensitive, and which are not?

Dentin is the only layer whose environmental exposure leads to tooth sensitivity—air, hot or cold drinks, or food trigger sensitivity in the teeth. In teeth with gum recession, the cementum quickly wears away with brushing, exposing the open dentinal tubules to the oral environment.

Can you cover exposed dentin?

Yes, you can cover exposed dentin. There is a wide range of toothpaste available for sensitive teeth. The active ingredients in the toothpaste block the tubules preventing tooth sensitivity. For instance, Colgate sensitive pro-relief repair and prevent contain amino acid formula with co-argin technology to occlude the dental tubules.

Dentin exposure and reduction in height of the teeth may occur if you have a habit of night grinding or bruxism. Getting a bridge or veneers may help maintain your facial height and bite if the teeth height are reduced. Also, you should consider wearing a night guard while sleeping to control the grinding habit. 

What causes teeth to lose enamel?

Excessive use of acidic drinks erodes the dental enamel over time. You will notice the top layer of a tooth coming off, exposing dentin.

Also, disorders such as bulimia or gastric esophageal reflux disease (GERD) are another reason for enamel erosion. Frequent vomiting in bulimia and stomach acid regurgitation in GERD erodes the enamel. 

Frequent use of aspirin water (dissolved in water) for heart conditions or aspirin tablets placed on the tooth for a toothache can lead to gradual enamel loss.

Toothbrushing with a hard bristle toothbrush or aggressive toothbrushing can abrade your enamel over time. Use soft bristles toothbrush with gentle strokes instead.

How do I know if my enamel is gone?

You will feel sensitivity in your teeth if your enamel is gone. The enamel forms a protective layer over the teeth. The teeth appear yellow due to dentin exposure. Also, the teeth appear short in patients with teeth-grinding habits, and the chewing surfaces of molars appear scooped out. 

What are the two parts of the pulp?

The pulp has two parts:

  • The pulp chamber lies in the core of the tooth crown. 
  • Root pulp lies in the root canals of the teeth. 

Can a tooth survive without pulp?

No, a tooth can’t remain vital without a pulp. However, it can be saved by removing the infected and damaged pulp and filling it with a filling followed by a crown. 

Does tooth pulp grow back?

Dental pulp has limited regenerative capacity, and an irreversibly damaged pulp can’t heal itself. With age, the pulp loses its capability to regenerate due to increased collagen fibers and decreased count of reparative cells. On the contrary, young vascular pulps have more cells and blood vessel supply and tremendous repair potential. 

What is the function of cementum in teeth?

Cementum covers the root dentin and provides tooth attachment to the bone with a huge network of fibers or ligaments.

How do I know If I have a layer of bacteria on teeth?

A couple of hours after toothbrushing, a biofilm knowns as plaque forms on the teeth. Dental plaque is composed of salivary proteins, oral bacteria and a sticky polysaccharide substance produced by bacteria. If plaque is not removed, it thickens and matures with diverse bacterial species leading to bad breath, gum inflammation, or tooth decay.  

What is the black layer on teeth? 

The black or brown layer on teeth could be due to tooth staining or a cavity. Prolonged plaque accumulation on the teeth can lead to cavity formation. The plaque bacteria metabolizes dietary sugars into acid, damaging the enamel. The bacteria gain access inside the tooth through the softened enamel. Inside the enamel, dentin becomes an easy target for the bacteria to destroy because of the increased organic matrix and less mineral salts.

If you are smoker, nicotine and tar in cigarettes may stain your teeth black. Also, a diet rich in copper and iron, deposits brown or black pigments on the teeth causing teeth staining.

The top layer of tooth came off – what to do next?

If the top layer of the tooth chips off, you need to see your dentist. The sharp edge of the broken tooth may hurt your tongue. The dentist will trim the sharp edge and reconstruct the lost part with a filling.

Enamel chipping can also expose dentin, allowing bacteria to attack porous and organic matrix-rich dentin. It is, therefore, important to see a dentist and get the tooth restored.

Conclusion 

Enamel, dentin, and pulp are the three distinct layers of the teeth. 

A thin outer layer of enamel protects the teeth; dentin forms the bulk of the teeth and has channels (tubules) that connect the pulp with enamel.

Pulp is soft and has a rich nerve and blood vessel network. It also houses reparative cells that repair dentin when needed. Enamel is a mineral-rich dead layer and cannot be repaired once damaged. 

Comment below if you find this blog informative or have any questions related to the blog.

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