Structure and function
The process of mechanical digestion mainly occurs in the mouth through the teeth, through a process called mastication.
There are four types of teeth present in human, and they are specialized for different functions.
Following table is showing the types and the functions of 4 types of teeth present in our mouth.
|position in mouth||front/middle teeth
|either side of incisors||between canines and molars||back/last flat|
|total number||total 8
4 lower jaw
2 upper jaw
2 lower jaw
4 upper jaw+
4 lower jaw
6 upper jaw+
6 lower jaw
( sharp edge)
|slightly more pointed than incisors||have two cusps
have one or two roots
|four or five cusps
have two or three roots
|function||biting the food||tearning and biting||tearing and grinding||chewing and best for grinding|
Teeth in human upper jaw
Structure of a Tooth:
Crown: The part of a tooth that is visible above the gum.
Gum: The gum is a tissue that overlays the jaws.
Root: The rest of the tooth that is embedded in the jaw bone, is called the root.
Enamel: the crown is covered by a hard white layer called Enamel. This layer is replaced by cement in the root, which enables the tooth to grip to its bony socket in the jaw.
Dentine: Below the Enamel is a layer of dentine. Dentine is softer than Enamel.
Pulp cavity: Inside the dentine is a pulp cavity, containing nerves and blood vessels,
enters the tooth through a small hole at the base of the root.
Causes of dental decay
- We all have germs in our mouth that plays an important part in dental decay.
- If we do not brush our teeth properly then food deposits and a layer of bacteria form on our teeth called plaque.
- Bacteria feed on this plaque and also on sugar taken up with sugary food and highly contained carbohydrates food.
- The germs make acids. This acid cause tooth decay means damages the surface of the tooth. Tooth decay cannot stop itself until it is treated so it can be prevented if it is caught early.
- And if proper dental care does not take place then over the time, acid will dissolve the enemal and make a hole or cavity and penetrate into dentine.
- Now if the cavity is not cleaned properly and filled by a dentist, the bacteria will
get into the pulp cavity.
- Once this penetration reaches the pulp cavity where nerves and blood vessels are present it will cause toothache and possibly, an abscess (an infectionin the jaw).
- Often, the only way to treat this is to have the tooth pulled out.
Different stages of tooth decay
There is usually a layer of saliva and mucus over the teeth. This layer contains bacteria that live on the food residues in the mouth, building up a coating on the teeth called plaque.
Tartar or culcus:
If the plaque is not properly removed, mineral salts of calcium and magnesium are deposited on it, forming a hard layer of ‘tartar’ or calculus. If the bacterial plaque that forms on teeth is not removed regularly, it spreads down the tooth into the narrow gap between the gum and enamel.
Here it causes inflammation, called gingivitis, which leads to redness and bleeding of the gums and to bad breath. Eventually gums recede and expose the cement.
If gingivitis is not treated well, it progresses to periodontitis; the fibres holding the tooth in the jaw are destroyed, so the tooth becomes loose and falls out or has to be pulled out.
Care of teeth:
The graph below shows how the pH in the mouth falls (i.e. becomes more acid) when a single sweet is sucked. The pH below which the enamel is attacked is called the critical pH. In this case, the enamel is under acid attack for about 10 minutes.
The following graph shows the effect of sucking sweets at the rate of four an hour. In this case the teeth are exposed to acid attack almost continually.
Steps to be taken for dental care:
- The best way to prevent tooth decay, therefore, is to avoid eating sugar at frequent intervals either in the form of sweets or in sweet drinks such as orange squash or soft (fizzy) drinks.
- It is advisable also to visit the dentist every 6 months or so for a ‘check-up’ so that any caries or gum disease can be treated at an early stage.
- Brushing the teeth is very important in the prevention of gum disease. It may not be so effective in preventing caries, although the use of fluoride toothpaste does help to reduce the bacterial population on the teeth and to increase their resistance to decay.
- Rinsing the mouth regularly with mouthwashes helps reduce the number of bacteria residing in the mouth.
- Drawing a waxed thread (‘dental floss’) between the teeth, or using interdental brushes, helps to remove plaque in these regions.
- How many total teeth an adult has?
- What is a wisdom tooth? Is it a molar or pre- molar?
- What is the function of molar and pre-molar?
- What is the basic cause of tooth decay?
- How does fluoride help to prevent tooth decay?
- What is a dental floss?
- What is the difference between plaque and gingivitis?
- What is enamel?
- What is an abscess?
- In which part of the tooth, nerves and blood vessels are present?