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Teeth and the World of Microbes - Dental Care and Hygiene

Grade 4CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Human beings have two sets of teeth: Milk teeth (temporary set of 2020 teeth) and Permanent teeth (adult set of 3232 teeth).

A tooth consists of three main layers: The outermost hard layer called Enamel, the middle layer called Dentin, and the innermost soft part called Pulp which contains nerves and blood vessels.

There are four types of teeth based on their functions: Incisors for cutting (88), Canines for tearing (44), Premolars for cracking (88), and Molars for grinding (1212).

Tooth decay occurs when bacteria react with sugar to produce acid: Sugar+BacteriaAcid\text{Sugar} + \text{Bacteria} \rightarrow \text{Acid}. This acid dissolves the enamel, leading to cavities.

Microbes are tiny organisms that can only be seen through a microscope. They include Bacteria, Viruses, Fungi, and Protozoa.

Helpful microbes include LactobacillusLactobacillus, which converts milk into curd, and YeastYeast, which is used in baking bread.

Harmful microbes, also known as germs, cause diseases like typhoid (bacteria), common cold (virus), and malaria (protozoa).

📐Formulae

Total Permanent Teeth=8 Incisors+4 Canines+8 Premolars+12 Molars=32\text{Total Permanent Teeth} = 8 \text{ Incisors} + 4 \text{ Canines} + 8 \text{ Premolars} + 12 \text{ Molars} = 32

Milk Teeth Count=20\text{Milk Teeth Count} = 20

Sugar+BacteriareactionAcidCavity (Tooth Decay)\text{Sugar} + \text{Bacteria} \xrightarrow{\text{reaction}} \text{Acid} \rightarrow \text{Cavity (Tooth Decay)}

💡Examples

Problem 1:

Calculate the total number of grinding teeth (Molars and Premolars) in a complete set of permanent teeth.

Solution:

2020 teeth

Explanation:

In a permanent set, there are 88 premolars and 1212 molars. Therefore, 8+12=208 + 12 = 20 teeth are used for grinding and crushing food.

Problem 2:

Identify the microbe responsible for the fermentation of dough in the kitchen.

Solution:

YeastYeast (a type of fungus)

Explanation:

YeastYeast is a fungus that reacts with sugars in the dough to produce CO2CO_2 gas, which makes the bread or cake soft and fluffy.

Problem 3:

Why do dentists recommend brushing twice a day in the context of pH levels?

Solution:

To prevent acid formation.

Explanation:

Brushing removes food particles and prevents Bacteria+SugarAcid\text{Bacteria} + \text{Sugar} \rightarrow \text{Acid} reaction, maintaining a healthy environment for the Enamel.

Dental Care and Hygiene - Revision Notes & Key Formulas | CBSE Class 4 Science