X. Read the sentences, find the predicates and define their tenses. Translate the sentences.

1. Enamel and dentin have different expansion coefficient.

2. Cracks are most frequently found in the molars of older patients.

3. It was found that in addition to pain on mastication sensitivity to thermal changes, sweet and sour foods were frequent.

4. The teeth were sensitive to cold and almost one sixth of patients had heat sensitivity.

5. A newer method of diagnosing cracks in enamel has been proposed by a group of scientists.

6. The excess of oil is then removed with a water jet.

7. If the crack has not involved the pulp such treatment is effective.

XI. Read and translate the text.

Dental Cracks

Cracks in the enamel and dentin may develop from thermal stresses. The cycling of temperatures which occurs, for example, in eating and drinking may crack the enamel because enamel and dentine have different expansion coefficient. The continuing stress of mastication coupled with clenching and grinding habits and restorative work may deepen the cracks. Thermal testing with frozen carbon dioxide (dry ice) may also deepen cracks or form new ones. The cracks may involve the pulp, and in extreme cases, the roots may be split. Cracks are most frequently found in the molars of older patients.

In reviewing 100 cases of incomplete crown-root fractures it was found that in addition to pain on mastication sensitivities to thermal changes, sweet and sour foods and alcoholic beverages were frequent; according to another researcher out of 150 patients studied almost half complained of pain on chewing and sensitivity to pressure, in 0ne-third the teeth were sensitive to cold, and almost one-sixth had heat sensitivity.

A newer method of diagnosing cracks in enamel has been proposed by a group of scientists. They recommend applying a fluorescent oil for 8 minutes after cleaning and polishing the tooth surface. The excess oil is then removed with a water jet and the tooth is examined under a surgical microscope with ultraviolet light. The cracks are visible as yellowish green lines.

Treatment consists in covering the crown of the tooth with an onlay or preferably a full crown. Such treatments are effective if the crack has not involved the pulp. When it has, endodontic therapy should be performed.

XII. Answer the questions.

1. Why do cracks in the enamel and dentin develop?

2. What process helps to crack the enamel?

3. What deepens the cracks?

4. What happens when the cracks involve the pulp?

5. In the molars of what patients are the cracks most frequently formed?

6. What did the researchers find in reviewing 100 cases?

7. What did they find in reviewing 150 patients?

8. What new method was proposed by a group of scientists?

9. Are the cracks visible under a surgical microscope?

10. What does the treatment of cracks consist of?

11. When is the treatment effective?

12. When should endodontic therapy be performed?

XIII. Translate the following word combinations:

трещины эмали и дентина, смена температур, разный коэффициент расширения, привычка стискивать зубы и скрежетать зубами, сухой лед, в крайнем случае, частичный (неполный) перелом, боль при жевании, сладкая и кислая пища, реакция (чувствительность) на холодное и горячее, алкогольные напитки, чистка и полировка зубной поверхности, видимые трещины, накладывать мазь, удалять излишек мази