Listen to the tape-recording of the text and be ready to read the text aloud.

There are two sets of teeth: the deciduous or milk teeth and

permanent ones.

The deciduous teeth are 20 in number 5 on each side of the upper and the lower jaw, namely: 2 incisors, 1 canine, and 2 molars. There are 32 adult or permanent teeth: 8 on each side above and below namely: 2 incisors, 1 canine, 2 premolars, and 3 molars.

Each tooth is divided into a crown above the level of the gum, a neck surrounded by the gum, and a root or roots embedded in the jaw.

The crowns are chisel-shaped in incisor teeth, peg-shaped in canine teeth, have two tubercles in premolar teeth; have several tubercles in molar teeth. The upper teeth usually form a wider arch than the lower teeth and therefore overlap them.

Each root tapers to a point. The roots of the incisors, canine, premolar teeth are single. Each upper molar has three roots - two lateral and one medial, each lower molar has two roots: anterior and posterior.

The bulk of each tooth is composed of an exceedingly hard substance called dentine. The crown is covered with a thin layer of a still harder substance called enamel. The root is covered with a modified bone called cement

In the interior of each tooth there is a cavity called the pulp cavity, which contains vessels and nerves. The vessels and nerves enter the tooth through a foramen at the tip of each root.

The first deciduous tooth to erupt is one of the incisors and it should appear about six months after birth; all milk teeth should have appeared by the end of the second year. The first permanent tooth to erupt is one of the first molars and it should appear during the sixth year.

By the twelfth year all the permanent teeth should have erupted except the third molar, which appears at the time between 17 and 30.

EXERCISES

Ex. 1. Give English equivalents:

временные зубы, постоянные зубы, появляться, прорезываться, резцы, клыки, коронка, шейка, десна, корень, бугорок, отверстие, вещество дентин, цемент, эмаль, перекрывать.

Ex. 2. Choose the correct form of the verb:

1. The first permanent teeth (will appear, appeared, are appearing, appear) at six.

2. Each tooth (was divided, will be divided, is divided) into three parts: a crown, a neck, a root.

3. The roots of teeth (are embedded, were embedded, will be embedded) in the sockets of the jaw.

4. The upper teeth usually (are formed, form, will form) a wider arch therefore overlap the lower ones.

5. The bulk of each tooth (compose, is composed, will compose) of an exceedingly hard substance called dentine.

6. Many new stomatological clinics (are building, built, are being built) in our city now.

Ex. 3. Give the correct form of the Predicate:

1. The crown of a tooth (to be covered) with the enamel.

2. The deciduous teeth (to be replaced).

3. Your teeth (to be examined) by this dentist

4. Some medicine (to be given) by the nurse.

5. A bad tooth (to be extracted) by the surgeon.

Ex. 4. Listen to the tape-recording of the text "Teeth" and be ready to answer some questions.

TEETH

The teeth are implanted on the borders of the upper and lower jaw bones. The jaw bones are covered with a tissue known as the gum, which encircles the lower portion of each tooth. Two sets of teeth are developed during life. The first set is the milk or baby teeth. These develop shortly after the seventh month usually and are lost during childhood, when the second set of teeth or the permanent ones appear. The teeth differ from each other in form and hence in their usage. The front teeth, orthe incisors, are sharp and serve for cutting and tearing. The back teeth have large bases or crowns utilized in grinding and crushing the food.

A tooth consists of three parts - the crown, the neck and the root. The tooth itself is composed of a hard outer covering surrounding the central pulp cavity which contains a blood vessel and a nerve. The outer covering consists of a very firm hard substance, the enamel. This is the protective covering of the teeth. Beneath this is dentine, a softer and less resistant material than the enamel. When the enamel is broken the dentine soon suffers.

Ex. 6. Answer the following questions and check your answers:

1. Where are the teeth implanted on?

2. What tissue covers the jaw bones?

3. How many sets of teeth are there during life?

4. What are they?

5. What is the function of the incisors?

6. What is the function of the molars?

7. What does a tooth consist of?

8. What dental tissues do you know?

Lesson 7

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