(4) The structure and function of teeth

Although teeth are not considered part of the skeletal system, teeth are made out of bone-like material (plus soft tissue) and also involve muscle action to work the jaw bones!

Teeth are NOT bone, but they are anchored to the jaw bones.

Designed for the crushing of food - mechanical digestion of food.

Image adapted from https://en.wikipedia.org/wiki/Human_tooth

Molars - the biggest teeth, large flat ridged surfaces to grind and chew food into smaller pieces that are easy to swallow.

Pre-molars - have many ridges and their main function is to chew and grind up food.

Canines ('fangs') - the strongest, but smaller sharpest pointed front teeth are used for biting food - you use them to bite into food first.

Incisors - flat sharper front teeth for tearing food, and used in first biting action too. They also support the lips.

The structure of the human tooth

image adapted from https://en.wikipedia.org/wiki/Human_tooth_development

The crown is the visible top part of your tooth and the 'invisible' root extends down below the gum line and helps anchor the tooth to the jaw bone.

Enamel coating - is the hardest and most mineralised part of a tooth that covers and protects the tooth crown.

Dentine - is the substance between the enamel or cementum and is a mineralised tissue not as hard as enamel, so susceptible to decay if the enamel is worn away.

Pulp - the central region of the tooth and contains the blood vessels, nerves and softer tissues that delivers nutrients and signals to and from the tooth.

Gums - tissue that covers the root of the tooth.

Cementum - a specialized bone like substance covering the root of a tooth and helps tether the root firmly to the jaw bones.

Bone - the root of the tooth is anchored to the jaw bone.

Blood vessels - bring nutrients and oxygen to the teeth cells, note the network of blood vessels and nerves right up to near the dentine.

Nerves - the inner softer tissue of teeth contain neurons which are part of the peripheral nervous system - very effective in sending pain signals to the brain if the tooth is infected, ouch!!!

 

Dental decay and plaque

Your teeth get coated with bacteria and food.  The bacteria respiring sugars in the food producing acidic molecules.  The acids dissolve the enamel and dentine.

The bacteria and undigested food and saliva form soft deposits called plaque which hardens with salts to form a deposit called calculus.

Both plaque and calculus act as food reservoirs by absorbing sugars on which the bacteria can feed on.

These bacteria respiring on sugars in the food, produce the acids which dissolves the enamel and dentine on your outer coatings of your teeth and exposing the inner structure of the teeth to potential decay.

 

Looking after your teeth and gums.

Brush your teeth regularly, which clears out residual food and bacteria so the acidic molecules are not formed in the first place - prevention is better than cure (if possible!) at the dentist.

It is not good to consume too many sugary foods or drinks on which the acid producing bacteria can feed on.

Calcium ions are an important component of the harder bone tissues, so your diet should include sources of calcium like milk, cheese, yogurt, nuts and green leafy vegetables.

Although very rare, lack of vitamin C from fruit and vegetables can lead to scurvy whose effect includes bleeding gums - gum disease.

See also the connection between teeth and your overall health

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Key points - The structure and function of teeth and looking after them

Based on the syllabus-specifications for students taking the UK AQA, Edexcel and OCR GCSE level biology examinations (~US grades 9-10 biology).

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Structure and Function of Human Teeth

Teeth are essential for mechanical digestion - they break food down into smaller pieces to increase the surface area for enzymes to act on. Humans are heterodonts, meaning we have different types of teeth for different functions.

Types of Teeth

• Adults have 32 permanent teeth, while children have 20 deciduous (milk) teeth.

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Tooth Structure

Each tooth has a specific structure made up of different layers:

• Enamel:

  • Hardest substance in the human body

  • Covers the crown (visible part) of the tooth

  • Protects inner tissues from decay and damage

• Dentine:

  • Beneath the enamel

  • Hard, but not as strong as enamel

  • Contains microscopic tubules that lead to the pulp

• Pulp cavity:

  • Central part with nerves and blood vessels

  • Supplies nutrients and responds to stimuli (like pain)

• Cementum:

  • Covers the root of the tooth

  • Helps anchor the tooth into the jawbone via ligaments

• Periodontal ligament:

  • Connects tooth to surrounding bone

  • Absorbs shock and holds tooth in place

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Taking Care of Teeth

To prevent tooth decay and gum disease, it’s essential to maintain proper oral hygiene and a balanced diet.

Causes of Tooth Decay:

1. Sugary foods: Feed bacteria in the mouth

2. Bacteria: Produce acid that dissolves enamel

3. Poor brushing: Allows plaque (a sticky bacterial layer) to build up

4. Acidic food/drink: Erodes enamel over time

Preventative Measures:

• Brush twice daily with fluoride toothpaste

• Use dental floss and mouthwash

• Limit sugary and acidic food and drinks

• Visit the dentist regularly

• Drink water after meals to help rinse acids

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Quick Recap Table

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Teeth and your overall health

Teeth do a lot more than just help you chew and smile - they’re surprisingly powerful indicators of your overall health. Here's how:

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1. Mouth-Body Connection

Your mouth is the gateway to your body.

Bacteria from gum disease or tooth decay can enter the bloodstream and travel to other organs, potentially contributing to:

• Heart disease – Inflammation from gum disease is linked to clogged arteries and increased risk of heart attacks and strokes.

• Endocarditis – A serious infection of the heart’s inner lining caused by bacteria from the mouth entering the bloodstream.

• Respiratory infections – Inhaling bacteria from infected teeth and gums can lead to pneumonia and other lung issues.

• Pregnancy complications – Gum disease has been associated with premature birth and low birth weight.

• Diabetes – Poor oral health can make it harder to control blood sugar, and diabetes can worsen gum disease.

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2. Warning Signs of Other Conditions

Changes in your teeth and gums can signal other health problems:

• Pale gums might indicate anemia

• Tooth enamel erosion can be a sign of acid reflux or eating disorders

• Persistent bad breath may point to systemic infections or digestive issues

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3. Prevention Is Powerful

Good oral hygiene - brushing, flossing, and regular dental checkups - doesn’t just protect your teeth. It helps reduce inflammation and bacterial spread, supporting your immune system and lowering your risk of chronic disease.

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Your teeth are like tiny health detectives and

keeping them healthy helps protect your whole body.

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Keywords, phrases and learning objectives for this part on bones, muscles, skeleton and teeth

Know the basic structure and function of teeth in terms of molars, pre-molars, canines, incisors, crown enamel coating, pulp, gums, cementum.

Know that teeth are fixed to the jaw bone and connected nerve system.

Know about dental decay and plaque formation and how to look after your teeth

Know that you need calcium in your diet for healthy bone structure.

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