1. St. Bonaventure College and High School Form 4 Biology Bridging Course 2009-2010
Structure of a tooth

3. Types of teeth

4. Dentition and Diet
Herbivores (e.g. rabbits) are animals that feed on plants only. Their incisors are sharp edged for cropping plants. Canine are either absent or reduced to form a diastema, a gap for holding grasses. There are ridged surfaces on the premolars and molars, which allow grinding of tough grasses and plant tissues.

5. Carnivores (e. g. dogs) are animals that feed on other animals only
Carnivores (e.g. dogs) are animals that feed on other animals only. Their teeth are adapted for killing prey, tearing flesh and crushing bones. Their canines are enlarged, with sharp pointed edges for piercing and grasping prey. There are carnassial teeth (modified premolars and molars), which form a pair of large, sharp blades for cutting flesh and bones on each side of the jaw.

6. Omnivores (e. g. humans) feed on both plants and animals
Omnivores (e.g. humans) feed on both plants and animals. Their teeth are less specialized compared with herbivores and carnivores as omnivores consume many types of food including both meat and plant materials. They usually have all four types of teeth.

7. Vocabularies jaw chew embedded enamel calcium phosphate resistant
decay
pulp cavity
nutrients
cement
incisor
canine
premolar
molar
chisel-shaped
biting
grinding
cusp
dentition
diet
herbivores
reduced
absent
carnivores
prey
carnassial teeth
omnivores

8. Questions What is the hardest substance in our body?
What are the functions of the different types of teeth?
What is the function of diastema in herbivores?

9. Useful vocabularies to answer question 2
saliva
plaque
alkaline
food debris
neutralize
dissolves
acid
tooth decay
stimulate
cumulative time
secrete
fluctuation
snakes

10. Question 2

11. Question 2
The pH value is restored to around 7 after the meal. How is the restoration brought about?(2 marks)
Saliva is alkaline and therefore it neutralizes the acidity in the mouth cavity.

12. (2) A chewing gum advertisement claims that its product can help speed up the pH restoration after meals. Explain how chewing gum can do so. (2 marks)
Chewing gum stimulates salivary glands to secrete more saliva to neutralize the acidity.

13. (1) Describe how the pH changes in the mouth cavity of Nicole differ from those of Leo. (2 marks)
The pH in the mouth cavity of Nicole shows more fluctuation. The pH falls not only at meal times, but also between meal times.

14. (2) Explain the difference in (1).
Nicole has snacks between meal times, while Leo does not.

15. Describe the occurrence of tooth decay. (4 marks)
The bacteria in the mouth cavity/ on the plaque break down sugars in the food debrisinto an acid.
The acid dissolves the calcium salts in enamel and causes tooth decay.

16. Who has a higher chance of getting tooth decay? Why? (3 marks)
Nicole. (no mark if explanation is not given)
The cumulative time of experiencing acidity in Nicole’s mouth cavity is longer.
The pH in Nicole’s mouth cavity is lower.