Read the text and be able to answer some questions.
The human teeth are made up of four tissues: the enamel, the dentine, the cementum and the pulp.
The enamel is the white, compact and very hard substance. The enamel covers the exposed parts of the softer underlying dentine. Its function is to protect the tooth against the wear and friction.
The dentine is the chief substance or tissue of the teeth composing the bulk of the tooth and the characteristic form of the tooth. It surrounds the tooth pulp, and is covered by the enamel on the exposed part of the tooth and by the cementum on the part implanted in the jaw. The dentine resembles a bone, but is harder and denser.
The cementum closely resembles in structure an ordinary bone. It covers the dentine beyond the border of the enamel, overlapping it slightly at the gingival line and forming the surface of the root. Its function is to furnish the attachment of the fibres of the periodontal membrane which fastens the tooth to the bone.
The cementum is relatively small in amount in the child but it increases during life.
The pulp is the soft vascular tissue occupying the pulp chamber and the root canals of a tooth, composed of nerves, blood vessels and connective tissue. It is the remain of the formative organ which has given rise to the dentine. The pulp of the tooth is one of the most sensitive structures of the body.
THE SUPPORTING TISSUES
The human teeth are supported on the alveolar and supporting bones,
the periodontal membrane and the gingivae. The alveolar processes of the
maxillary bones grow up around the roots of the teeth, so that the roots
fit into the holes of the bone. The periodontal membrane performs three
functions:
(a) it maintains the teeth in their functional positions through its
suspensory mechanisms;
(b) it takes part in the formation of the bone of its own alveolar walls and of the cementum;
(c) it provides through its tactile sensory mechanisms, for protection against the swallowing of hard, sharp and potentially dangerous materials.
1. What dental tissues do you know?
2. What is the enamel?
3. What is the chief tissue of the teeth?
4. Where does the cementum cover the dentine?
5. What is the most sensitive structure of the body?
6. Does the periodontal membrane support the teeth against the forces of mastication?
EXERCISES
Ex. 1. Listen to the tape-recording of the text and prepare the reading of it.
Ex. 2. Give English equivalents:
зубные ткани, поддерживающие ткани, защищать, изнашивать, трение, незащищенные ткани, по десневой линии, над границей, перекрывать, поддерживающий механизм, защита, альвеолярные отростки, осязательный, образовательный.
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Ex. 3. Supply the correct form of the Participle:
1. The cases (to report) in the medical journals show that the inflammation of periosteum may be very serious.
2. To woman (to sit) at the patient's bed is a demist and she wants to examine his teeth.
3. (To have) severe toothache, the patient asks the doctor to give him some soothing medicine.
4. This patient (to place) under treatment early enough avoided the inflammation of periosteum.
5. (To suffer) from severe toothaches one must seek medical advice.
Ex. 4. Translate, using the necessary form of the Participle:
1. Дентин - это твердая зубная ткань, составляющая основу зуба.
2. Пульпа - это мягкая ткань, заполняющая центральную полость дентина.
3. Так как у вас стоматит, вы не должны курить.
4. Зубы человека, состоящие из 4-х тканей, располагаются на альвеолярных отростках челюстных костей.
Ex. 5. Answer the following questions and check your answers:
1. What are the human teeth made up of?
2. What does the enamel cover?
3. What is the function of the enamel?
4. What does the dentine compose?
5. What does the cementum cover?
6. What is the function of the cementum?
7. What is the pulp?
8. What are the human teeth supported on?
9. What are the functions of the periodonta) membrane?
Ex. 6. Translate the text without a dictionary.
The cement is the layer of a modified bone which encases the whole of the tooth except its crown. It begins at the neck as a very thin layer which slightly overlaps the enamel. From there it is continued increasing in amount towards the apex, which is formed entirely of this substance. It is relatively, small in amount in children, but it increases during life.
The pulp of the tooth is composed of a number of branched fibrous tissue ceils. Their processes form a fine network, which contains numerous blood-vessels, nerves, and lymph vessels. The most superficial of these cells are arranged in the young tooth, lying on the surface of the tooth against the destine; they are known as odontoblasts for they are active in the formation of the dentine.
The vessels of the tooth-pulp are numerous. Fine nerve bundles run through the pulp, the root canals towards the crown of the tooth and some of their fibres enter the odontoblasts Sayer. The alveolar periosteum is a layer of fibrous tissue free from elastic fibre but well supplied both with blood vessels and nerves.
Ex. 7. Answer these questions and check your answers:
1. What does the cement encase?
2. Where does the cement begin?
3. Is the cement small in amount in children?
4. What do the processes of the pulp form?
5. What are odontoblasts?
6. What is the alveolar periosteum?
7.
Ex. 8. Speak on the dental tissues and their functions using the picture below.
Lesson 9