CBSE Class 4 Science The Teeth Worksheet Set 01

Answer: (a) 20 milk teeth. A young child has a set of 20 milk teeth.

Teacher's Note:
1. Milk teeth are the first set and are later replaced.
2. The full set of 32 belongs to adults and is made of permanent teeth.

Answer: (a) Enamel. Enamel is the hard white covering of the crown and is the hardest substance in the body.

Teacher's Note:
1. It protects the softer parts inside.
2. Enamel cannot grow back once it is damaged.

Answer: (b) Molars. Molars are broad and flat, which makes them good for grinding food.

Teacher's Note:
1. Premolars are also fairly flat and help in grinding.
2. Incisors are thin and sharp-edged, so they cannot be the answer.

Answer: (c) Pulp. The pulp has nerves and blood vessels, so damage that reaches it causes pain.

Teacher's Note:
1. A cavity in the enamel or dentine usually hurts little.
2. Visit a dentist before the cavity reaches the pulp.

Answer: (b) Canines. Canines are sharp and pointed and are used to tear food.

Teacher's Note:
1. Meat-eating animals have very large canines.
2. Incisors cut and molars grind.

Answer: (c) 32. An adult has 32 permanent teeth: 8 incisors, 4 canines, 8 premolars and 12 molars.

Teacher's Note:
1. Add the four types to check: 8 + 4 + 8 + 12 = 32.
2. Milk teeth have no premolars, which is why children have fewer teeth.

Answer: True. Enamel is the hardest material in the human body, harder than bone.

Teacher's Note:
1. It is hard because it contains a lot of minerals.
2. Even so, sugar and germs can slowly damage it.

Answer: False. Milk teeth are replaced by permanent teeth, but a permanent tooth that falls out is not replaced.

Teacher's Note:
1. This is why we must take good care of permanent teeth.
2. Only the first set has a replacement.

Answer: False. Incisors, canines, premolars and molars have different shapes for different jobs.

Teacher's Note:
1. A tooth's shape matches the job it does.
2. The four shapes work together to bite, tear and grind food.

Answer: True. The pulp is soft because it holds nerves and blood vessels.

Teacher's Note:
1. The dentine is harder than the pulp but softer than the enamel.
2. The order from hardest to softest is enamel, dentine, pulp.

Answer: False. A cavity does not heal by itself and must be treated by a dentist.

Teacher's Note:
1. If left alone, it grows deeper over time.
2. Early treatment saves the tooth.

Answer: plaque. Plaque makes acids that damage enamel.

Teacher's Note:
1. Brushing twice a day removes plaque.
2. Plaque left on teeth leads to cavities.

Answer: crown. The part below the gum is the root.

Teacher's Note:
1. The crown is covered by enamel.
2. The root holds the tooth firmly in the jaw.

Answer: dentist. We should visit a dentist for a check-up at least twice a year.

Teacher's Note:
1. Regular visits help find problems early.
2. Dentists also teach good brushing habits.

Answer: Incisors cut and bite food. Canines tear food. Premolars and molars crush and grind food.

Teacher's Note:
1. Each kind of tooth has a special job.
2. Together they break food into small pieces that are easier to swallow.

Answer: The crown, the root and, inside, the enamel, dentine and pulp, with the gum around the base.

Teacher's Note:
1. Enamel is the outer coat and dentine lies below it.
2. The pulp is in the centre.

Answer: Milk teeth are the first set of 20 teeth that a baby grows. They begin to fall out at about 6 years of age and are replaced by permanent teeth.

Teacher's Note:
1. They are called milk teeth because they appear when the child still drinks milk.
2. The new teeth that replace them must last for life.

Answer: 1. Calcium - milk. 2. Phosphorus - fish or nuts. 3. Vitamin C - orange or amla (good for gums).

Teacher's Note:
1. Calcium and phosphorus make teeth strong.
2. Vitamin C keeps gums healthy.

Answer: Sticky toffees, chocolates and sweet cold drinks (or other sugary snacks).

Teacher's Note:
1. Sugary food feeds the germs that cause cavities.
2. If you eat sweets, rinse your mouth afterwards.

Answer: 1. Brush twice a day. 2. Rinse after meals. 3. Avoid too many sweets. 4. Visit the dentist regularly.

Teacher's Note:
1. Good habits keep teeth strong for life.
2. Brush gently for about two minutes.

Answer: The sharp edges act like blades, so the front teeth can cut and bite food easily.

Teacher's Note:
1. Incisors work like scissors.
2. Without them we would find it hard to bite into apples or bread.

Answer: The enamel and dentine have no nerves. The pulp holds the nerves, so pain begins only when the cavity reaches it.

Teacher's Note:
1. By that time the damage is already deep.
2. This is why regular check-ups are important.

Answer: Sweets leave sugar on teeth that germs turn into acid. The acid damages the enamel and causes cavities, so brushing removes the sugar and germs.

Teacher's Note:
1. Rinsing the mouth also helps if you cannot brush.
2. Cleaning teeth in time saves them.