XII. Translate the text using a dictionary.

Dental Caries

Dental caries is a wide-spread disease. It is as old as mankind. For hundreds of years people believed caries and toothache were caused by a worm in the teeth. One of the earliest references to this belief was found in a papyrus dating from at least 1000 BC. This theory was disproved only in the middle of the 16^th century. Now it is believed that caries is caused by microorganisms and is characterized by demineralization of the mineral part of enamel and dentine with the following disintegration of their organic matter. When the disease approaches the pulp it may cause bacterial invasion and death of the pulp. The infected pulp causes changes in the periapical tissues.

At the early stage of enamel caries bacterial acid leads to production of micropores enamel. The earliest clinically visible evidence of enamel caries is a white or brown spot lesion. This lesion may be present in the mouth for some years without any development. If the early enamel lesion progresses the intact surface breaks down forming a hole (cavitation). With cavitation of enamel bacteria have direct access to dentine and the tissue becomes infected.

Role play

I. Read the information about some specific features of writing and abstract for a research paper.

The key elements to be included in the abstract.

1. Background: a simple opening sentence or two placing the work in context.

2. Aims: one or two sentences giving the purpose of the work.

3. Method(s): one or two sentences explaining what was (or will) be done.

4. Results: one or two sentences indicating the main findings (or what you hope to accomplish with the project).

5. Conclusion(s): one sentence giving the most important consequence of the work. What the results mean. How they will be used.

II. Read and learn the following linking words and phrases that are useful for writing a summary essay.

The text is titled …

The text is written by …

The main idea of the text is …

The article is devoted to …

It is clear from the text that …

The author reports …

According to the text …

It should be noted that …

In conclusion …

In summary …

The author comes to the conclusion that …

On the whole …

I found the text interesting (important, dull, of no value, too hard to understand …)

III. Read the abstract and following the above instructions practice writing its summary essay. Present your summary essays to the class and discuss them.

Classification of Carious Lesions

There are two broad classifications of tooth decay based on the anatomy of the tooth surface involved: pit and fissure, and smooth surface. The pattern by which the spread of dental caries occurs as it enlarges and deepens differs in these two types.

Pit and fissure carious lesions begin in the depth of pits and fissures which form from incomplete fusion of enamel lobes during tooth development and are nearly impossible to keep clean. Fissures and pits are commonly located on the occlusal surfaces of the posterior teeth (molars and premolars), as well as on the lingual surface of maxillary molars, the buccal surface of mandibular molars, and the lingual fossae of maxillary incisors, especially lateral ones.

In contrast to pit and fissure caries, smooth surface carious lesions occur on the smooth surfaces of the anatomic crown of the tooth in the areas which are least accessible to the natural cleansing action of the lips, cheeks, and tongue. The pattern of spread within enamel for smooth surface caries is different from that for pit and fissure caries since it begins as a relatively broad area of destruction just beneath the outer layer of enamel but it narrows as it progresses more deeply toward the dentinoenamel junction. Once it reaches dentin, however, it spreads out wider at the dentinoenamel junction, just like pit and fissure caries.

Root surface caries is another type of smooth surface caries that occurs on cementum, most frequently in patients with disease of the periodontium, patients with decreased saliva flow, or in older patients who have had gingival recession which increases the potential for accumulation of caries-forming plaque on the cementum of root surfaces. Treatment in these cases can include polishing the root, applying fluoride and keeping the roots clean through good oral hygiene.

In 1908, Dr. G. V. Black developed a comprehensive method of classifying carious lesions that has been useful when describing specific principles cavity preparation. The original classifications were G. V. Black Class I, II, III, IV and V. All pit and fissure type lesions are Class I, whereas Class II, III, IV and V caries are all smooth surface type lesions.