Read the passage below and decide if the sentences are True or False.

How can we keep our teeth healthy? Firstly, we ought to visit our dentist twice a year. He can fill  small holes in your teeth. He can examine our teeth to check that they are growing in the right way. Unfortunately, many people wait until they have toothache before they see a dentist. Secondly, we should brush our teeth with a toothbrush and fluoride toothpaste at least twice a day, once after breakfast and once before we go to bed. We can also use dental floss to clean beetween our teeth after a meal. Thirdly, we should eat food that is good for our teeth and our body: milk, cheese, fish, brown bread, potatoes, red rice, raw vegetables and fresh fruit. Chocolates, sweet, biscuits and cakes are bad, especially when we eat them between meals. They are harmful because they stick to our teeth and cause decay.

Sweets are harmful to teeth because __________.