What it shows
Our teeth have different shapes for different jobs. Incisors cut, canines tear, premolars and molars crush and grind, and each kind can be matched to the food it deals with.
The science
An adult has 32 teeth: 8 incisors, 4 canines, 8 premolars and 12 molars. Children have 20 milk teeth which fall out and are replaced. Incisors have a flat, sharp edge for cutting food, canines are pointed for tearing, and premolars and molars have broad, bumpy tops for crushing and grinding. Each tooth has hard enamel on the outside, dentine below and a soft pulp inside with nerves and blood vessels.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- White clay or salt dough (1 cup flour, 1/2 cup salt, water)
- A cardboard mouth shape cut as two arches
- Red paper or red poster colour for the gums
- Toothpicks to hold teeth
- Small samples of food: a piece of carrot, a roti and a chikki
- Coloured pencils
- A mirror
Safety
For this project: An adult must cut the cardboard. Do not eat the salt dough, and wash hands after handling it.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Colour two arches of card red as the upper and lower gums and glue them onto a base.
Roll small clay pieces to make flat chisel-shaped incisors and press four on each arch at the front.
Make a pointed canine on each side of the incisors, one per side per arch.
Add wider premolars and then broad, bumpy molars behind them, drying the clay overnight if it is salt dough.
Look at your own teeth in a mirror, count the front, pointed and back teeth and compare with the model.
Ask an adult to watch you bite and chew a piece of carrot and a roti, and note which teeth you use for cutting and for grinding.
Label the model with tooth names and jobs, using a coloured arrow for each.
Draw one tooth in section and label the enamel, dentine, pulp and root.
What you should see
The finished mouth shows four different tooth shapes in the right places, each labelled with its job, and your chewing notes match them.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1Which teeth cut food?
Incisors.
2How many teeth does an adult have?
32.
3What is the hard outer layer of a tooth?
Enamel.
4Why do children get a second set of teeth?
Milk teeth are small and the jaw grows, so larger permanent teeth replace them.
Take it further
Make a chart of how many teeth your classmates have lost and count the average number of milk teeth left in the class.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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