If the teeth are not cleaned regularly, they become covered with a sticky yellowish laryer 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 decays 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

Answer

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