How many teeth have you had filled in the past two years? If you follow the adv ice of Dr. Faustick, you may be able to reduce the number of your visits to a dentist. Dr. Faustick conducted a two-year survey to find out how to prevent or reduce dental decay. (1)_______________________.
523 students cleaned their teeth within ten minutes of eating: when possible they used a toothbrush, when this was impossible they washed their mouth thoroughly with water. (2)_____________________________when they went to bed and when they got up in the morning. All the students had their teeth X-rayed at the end of the first and second years. At the end of the first year, the night and morning group had three times as many decayed teeth as the clean after each meal group.
At the end of the second year (3)__________________________________.
946 students took part in the experiment
there remaining 423 students clean their teeth
the later group has 53 percent fewer decayed teeth than the formor group
发表于 2016-9-5 16:01
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发表于 2016-9-8 15:15
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