Grade Six Science
Was your past week a good one? Have you been keeping well? How well did you do your Mock Exam? I hope you put your best foot forward. This week let us turn our attention to the teeth.
Look at your teeth in the mirror. How do they look? How would you look without them? Why do we have teeth? That’s right, our teeth help us to have a lovely smile, a pleasant appearance. Our teeth also help us to speak nicely, and very importantly, our teeth help us to chew our food.
Someone said that a tooth is a bit like a tree. Can you explain how that is so? Yes, only part of the tree is visible, and the other part is below the surface of the earth. Part of your tooth is visible and the other part, the roots are within the gum and not visible.
Teeth are hard bony structures that grow from the jawbone.
Unlike the brain, your teeth are not ready to work from the first day you are born. You only see the baby’s teeth from when they are about six to twelve months old. Humans grow two sets of teeth during their lifetime. The first set is called baby teeth, milk teeth or temporary teeth. There are 20 of these teeth. When a child is about six years old these teeth will become loose and fall out. (That’s when the children say/sing All I want for Christmas is my two front teeth.) Over the next few years 28 permanent teeth replace the baby teeth. Around 20 to 22 years, a person gets four more back teeth called wisdom teeth.
Let’s look at parts of a tooth.
The tooth has several outer parts, the crown which we see, the root which we don’t see and the neck. The tooth has several layers, the enamel which is the outer layer. The enamel is the hard outer shell that covers the crown. It helps to protect the inside parts of the tooth. The body cannot repair it so we must care it.
Just as the enamel covers the crown of the tooth, cementum covers the root or roots. It is not as hard or as white as enamel. The cementum helps to anchor the tooth to the jawbone.
Dentine makes up most of the tooth. It is a bone-like substance found just under the enamel in the crown and under the cementum in the root.
Beneath all of this, at the core of the tooth is the pulp cavity. Look again at the diagram. This space contains blood vessels, nerves and other tissues, all called the pulp. The blood provides nutrients that help to keep the tooth alive. Nerves in the tooth send signals to the brain about heat, coldness or pain. Have you ever had a toothache?
One of the biggest problems with teeth is tooth decay. Germs formed in the teeth, especially when the teeth are not brushed often enough, eat away tooth enamel and from a hole or cavity in your tooth. It may cause pain or infection.
There are different types and shapes of teeth in your mouth. The shapes of animals teeth give us clues to their type of diet. Can you tell? Meat eaters have sharp, pointed teeth. Why? Plant eaters have broad, flat teeth. Why? Humans have different types of teeth as we eat both plants and animals.
For you to do now:
1. Give three names for the first set of teeth we get. 2. Name four types of teeth. Explain their functions. 3. Draw a tooth and label it.
We have different types of teeth in our mouth. Each one has a different function. The four front teeth are called incisors. They are sharp and are used for cutting and chopping food.
The pointed teeth near to the incisors are the canine teeth (cuspids). There are two at the top and two at the bottom. They help to tear the food e.g. flesh from the bones of meat. If you open your mouth widely you will see the premolars and molars. They are broader, bigger and stronger, and have ridges for crushing and grinding the food.
For you to do
1. In the adult, state the number of incisors canines premolars molars 1. Describe how a tooth decays. ________________________________________________________________ ________________________________________________________________ ________________________________________________________________
2. State three reasons for having teeth. i. ______________________________________________________________ ii. ______________________________________________________________ iii. ______________________________________________________________
Let’s now find out how we can care our teeth. Caring our teeth
Have you ever heard this little poem/verse below? Brush your teeth
Brush your teeth
Brush them every day
Up and down
And all around
That is the proper way