Programme For International Student Assessment Pisa / Sample Science Passage 8: Tooth Decay


Bacteria that live in our mouths cause dental caries (tooth decay). Caries have been a problem since the 1700s when sugar became available from the expanding sugar cane industry. 

Today, we know a lot about caries. For example: 
- Bacteria that cause caries feed on sugar. 
- The sugar is transformed to acid. 
- Acid damages the surface of teeth. 
-Brushing teeth helps to prevent caries.

Graph 1: 



Graph 2:



What is the role of bacteria in dental caries?

Bacteria produce sugar.
Bacteria produce acid.
Bacteria produce enamel.
Bacteria produce minerals.

The second graph above shows the consumption of sugar and the amount of caries in different countries. Each country is represented by a dot in the graph. Which one of the following statements is supported by the data given in the graph?

The more sugar people eat, the more likely they are to get caries.
In some countries, people brush their teeth more frequently than in other countries.
In recent years, the consumption of sugar has increased in many countries.
In recent years, the rate of caries has increased in many countries.

 
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