VIII. Read and translate the texts.

Forms and Functions of Teeth

Teeth are of different shapes. Human teeth are more complicated in form than the teeth of other animals.

The basic shape of all teeth is a simple cone. This conic shape is modified in different teeth in order to perform different functions.

The biting edge or edges of the wide-shaped crowns are the cusps that first cut food upon mastication.

The incisors are a single cone with a sharp, flattened crown which forms a wide cutting edge. The canines are also a simple cone but have a sharp pointed cusp. The premolars are two fused cones, i.e. they have a two-cusped crown. They function as nutcrackers. The large molar teeth are a coalescence of several (three to five) cones and form a broad chewing surface. the first molar has four or five cusps, the second one has four cusps and the third molar usually has three cusps.

The Dental Formula

The human being has two sets of teeth: the primary or deciduous teeth sometimes called baby or milk teeth, and permanent teeth. There are 20 primary teeth: 8 incisors, 4 canines and 8 molars. The permanent teeth are 32 in number: 16 in the maxilla and 16 in the mandible. They are: 8 incisors, 4 canines, 8 premolars and 12 molars. Each tooth is paired, i.e. there is another tooth like it on the other side of the mouth. The form and location of these paired teeth determine the work of the teeth. Dentists use a formula in order to describe teeth. The formula always begins at the middle front of the mouth.

I 2/2 – two incisors in the upper half and two incisors in the lower half of the jaw.

C 1/1 – one canine in the upper half and one canine in the lower half of the jaw.

P 2/2 – two premolars in the upper and lower halves.

M 3/3 – three molars in the upper and lower halves.

This makes teeth for each half of the upper and lower dental arch, i.e. a total of 32 permanent teeth.

IX. Answer the questions.

1. Do teeth have different shapes?

2. Are the human teeth more complicated in form than the teeth of other animals?

3. What is the basic shape of teeth?

4. Do different teeth perform different functions?

5. What is the form of the incisors?

6. Do the incisors cut the food?

7. What teeth function as nutcrackers?

8. What teeth form a broad chewing surface?

9. How many sets of teeth does a human being have?

10. How many deciduous teeth are there?

11. What are the names of the teeth?

12. How many permanent teeth are there?

13. Is each tooth paired?

14. What determines the work of the teeth?

X. Translate the sentences into English.

1. У человека два набора зубов – молочные и постоянные.

2. Зубы имеют разную форму, чтобы выполнять различные функции.

3. основная форма всех зубов – простой конус.

4. Резцы представляют собой простой конус с острой, плоской коронкой.

5. Клыки представляют собой простой конус с заостренным выступом.

6. Премоляры представляют собой два слившихся конуса. Они имеют коронку с двумя выступами.

7. Коренные зубы представляют собой слияние нескольких конусов, которые образуют широкую жевательную поверхность.