2020-09-24
1113
THE NUMBER OF THE TEETH
The deciduous teeth are the first set and are also known as milk or temporary teeth. There are twenty of them; ten in each jaw with five on each side.
Deciduous teeth start developing inside the jaw before birth and erupt after birth. Eruption starts at six months and is completed at two years. Individual variation is common but the average ages are as follows:
A. Central incisor, 6months;
B. Lateral incisor, 8 months;
C. Canine, 18 months;
D. 1st MOLAR, 12 months;
E. 2nd MOLAR, 24 months.Lower teeth usually erupt before their corresponding upper.
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. 5. 2nd premolar, 11 years (lower); 10 years (upper).
2. Lateral incisor, 8 years. 6. 1st molar, 6 years.
3.Canine, 9 years (lower); 11 years (upper). 7. 2nd molar, 12 years.
4. 1st premolar, 10 years (lower); 9 years (upper). 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.
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.
PART II
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
The biting surface of molars and premolars is called the occlusal surface. On incisors and canines it is called the incisal edge. The occlusal surface is the biting surface of the posterior teeth, i.e. of molars and premolars, which is raised up into cusps. Between the cusps are crevices known as fissures.
The outer surface of molars and premolars — the surface facing the cheeks — is called the buccal surface. In the case of incisors and canines this surface is called labial as it faces the lips instead of the cheeks.
The inner surface of every lower tooth faces the tongue so it is called the lingual surface. This surface in all upper teeth is known as the palatal surface.
The remaining surfaces are those between adjoining teeth. The surface facing towards the front of the mouth is called mesial and that facing backwards is called distal. The adjective cervical is used for the neck of the tooth.
