If the teeth are not cleaned regularly, they become covered with a sticky yellowish layer W of food particles and bacteria. Since layer W covers the teeth, the alkaline liquid X secreted by glands Y inside the mouth cannot reach the teeth surface to neutralise the acid formed by the action of organisms Z on sugary food, and hence tooth decay sets in.
(a) What is W known as ?
(b) What is (i) X, and (ii) Y ?
(c) What are organisms Z ?
(d) State one way of removing layer W from the teeth.

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Solution

(a) Dental plaque (b) (i) Saliva (ii) Salivary glands (c) Bacteria (d) Brushing the teeth regularly after eating food

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When a person eats sugary food, then organisms A present in his mouth act on sugar to produce a substance B. The substance B first dissolves the calcium salts from the top part C of the tooth and then (rum its middle part D forming holes E. These holes ultimately reach the part F in the lower part of tooth which contains: nerves and blood vessels. The substance B irritates the nerve endings inside the tooth causing toothache.

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(c) By what name are the holes E in the tooth known?
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Q. When a person eats sugary food, then organisms A present in his mouth act on sugar to produce a substance B. The substance B first dissolves the calcium salts from the top part C of the tooth and then from its middle part D forming holes E. These holes ultimately reach the part F in the lower part of tooth which contains nerves and blood vessels. The substance B irritates the nerve endings inside the tooth causing toothache.
(a) What are (i) organisms A, and (ii) substance B?
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