The Permanent Teeth

Permanent teeth are the second and final set. There are thirty-two of them; sixteen in each jaw, eight on each side. Like deciduous teeth, the eight on each side of both jaws have the same names.

Permanent teeth start devel­oping at birth. Eruption commences at six years of age and is completed at eighteen to twenty-five years. Eruption times are subject to consider­able individual variation but the average ages are:

1. Central incisor, 7 years.

2. Lateral incisor, 8 years.

3. Canine, 9 years (lower); 11 years (upper).

4. 1st premolar, 10 years (lower); 9 years (upper).

5. 2nd premolar, 11 years (lower); 10 years (upper).

6. 1st molar, 6 years.

7. 2nd molar, 12 years.

8. 3d molar, 18-26 years.

After the deciduous teeth loosen, they are shed and are soon replaced by eruption of their permanent successors. Deciduous incisors and canines are replaced by permanent teeth of the same name. Deciduous molars, however, are replaced by premolars. Thus the permanent molars erupt without having any deciduous predecessors. Deciduous teeth become loose by resorption of their roots which deprives them of their attach­ment to the jaws. The unerupted permanent successors lie adja­cent to the absorbing deciduous roots and are thus able to erupt into their places when the deciduous teeth are finally shed.

POST-TEXT ASSIGNMENT

Exercise 8. Find in the text English equivalents for these words and word combinations:

1.також відомі як. 2. десять у кожній щелепі — по п'ять з кожного боку. 3. мати назву. 4. прорізуються після наро­дження. 5. індивідуальна відмінність. 6. протилежні верхні. 7. як і тимчасові зуби. 8. завершується. 9. незабаром замі­нюються. 10. мати таку ж назву. 11. випадають через розсмок­тування їх коренів. 12. ті, що не прорізалися. 13. здатні до прорізування.

Exercise 9. Quote the sentences in which the following words and word com­binations are used in the text.

to be named, arrival, usually, at birth, to be subject, loosen, premolars, deprive, to be shed.

Exercise 10. Make the sentences negative and then interrogative:

1. The deciduous teeth are the first set.

2. All teeth start developing inside the jaw.

3. Eruption starts at six months.

4. Permanent teeth are the second and final set.

5. After the deciduous teeth loosen, they are shed.

Exercise 11. Answer these questions:

1. How are deciduous teeth also named?

2. How many deciduous teeth do you know and what are they?

3. When do deciduous teeth start developing?

4. What are average ages for tooth eruption?

5. When do lower teeth usually erupt?

6. How many permanent teeth are there?

7. When does eruption of per­manent teeth start? And when is it completed?

8. What are deciduous teeth replaced by?

9. Why do deciduous teeth become loose?

Exercise 12. Insert articles where necessary:

1. ... deciduous teeth are also known as temporary.

2. There are five teeth on ... each side of ... jaw.

3. Their arrival in ... mouth is known as eruption.

4. Eruption starts at six month and is com­pleted at ... two years.

5. Permanent teeth are ... second set.

6. Permanent teeth start developing at ... birth.

7. Eruption is completed at eighteen to twenty-five years of ... age.

8. Deciduous molars are replaced by ... premolars.

Exercise 13. Give a summary of the text «The Number of the Teeth».

PART II

PRE-TEXT ASSIGNMENTS

Exercise 1. Read, translate and learn the following words:

Bite [bait] прикус

Cusp [kΛsp] вістря зуба, горбик

Crevice [krevis] тріщина, щілина

Fissure [fi∫ә] щілина, тріщина, борознa

Incisal edge [insaizәl e] ріжучий край

Exercise 2. Practice the pronunciation:

Mesial [mi:zjәl], occlusal [oklu:3l], buccal [bΛkәl], lingual [liŋwәl], facial [fei∫l], posterior [posiәriә], anterior [æntiәriә].

Exercise 3. Find the Ukrainian equivalents:

1. Posterior teeth a. передні зуби

2. Occlusal surface b. медиальна поверхня

3. Median line c. внутрішня поверхня

4. Against the lips d. периферична поверхня

5. Mesial surface e. язикова поверхня

6. Inside surface f. задні зуби

7. Anterior teeth g. оклюзійна поверхня

8. Distal surface h. середня лінія

9. Lingual surface i. піднебінна поверхня

10. Palatal surface j. напроти губ

11. Buccal surface k. лицева поверхня

12. Labial surface l. щічна поверхня

13. Facial surface m. губна поверхня

Exercise 4. Read the text «Surfaces of the Teeth» and write out the main terms characterizing different surfaces of the teeth. Translate the text and retell it.