PrepTest 149, Section 4, Question 1
Dentist: I recommend brushing one's teeth after every(43 more words not shown)
Which one of the following,(12 more words not shown)
- AA piece of(14 more words not shown)
- BTooth decay can(12 more words not shown)
- CChewing gum stimulates(15 more words not shown)
- DSugars can be(19 more words not shown)
- EChewing gum exercises(16 more words not shown)
Reading the argument
Why add sugar when we're trying to get sugar off our teeth?
The dentist gives us a chain: sugar helps bacteria grow, the bacteria produce acid, and the acid damages enamel. Brushing removes the sugar. But chewing sugary gum seems to put more of the troublesome substance into the mouth. What benefit could make that a sensible backup when brushing isn't practical?
What we’re looking for
Maybe gum kills the bacteria. If so, adding some sugar wouldn't tell the whole story: the gum would also interfere with the process that leads to cavities. That's my first guess for reconciling the recommendations. We need a way chewing gum can protect teeth despite the sugar it may contain.
Working the answers
- A
Less added sugar is still added sugar. This could make the gum seem less concerning than a whole meal, but it doesn't explain why chewing it would help prevent cavities. We need a benefit of the gum, not merely a smaller amount of the ingredient the dentist wants removed.
- B
Knowing that decay can be reversed doesn't tell us that chewing gum helps reverse it. The answer never connects the recommended action with that possibility. Tooth decay could be reversible through some entirely different process while sugary gum offered no protection.
- CCorrect
The benefit comes from saliva, rather than from killing bacteria as I guessed. Chewing stimulates saliva, which reduces the acid and helps restore minerals to the enamel. Those effects counter the process the dentist described. The gum can therefore offer protection even if it introduces some sugar: we have to consider its helpful effects too.
- D
A delay before bacterial growth doesn't explain why gum prevents cavities. Even if damage doesn't start immediately, why would adding gum help? The recommendation calls for a protective action when brushing isn't practical, not simply waiting a while before brushing.
- E
Healthier jaw muscles aren't the particular benefit we're trying to explain. An action could exercise the jaw without preventing acid from damaging enamel. E connects gum to a different aspect of oral health; C connects it to the cavity-forming process in the passage.
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