Q1. What is the passage mainly about?

1. AHow to make toothpaste
2. BWhether you should wait to brush after eating
3. CWhy sour drinks taste good
4. DHow many times to brush a day

食後すぐ歯をみがいてよいか、待つべきかがテーマなので B。

Q2. What helps protect your teeth?

1. ASugar
2. BSour drinks
3. CFluoride
4. DWaiting two hours

Fluoride helps protect your teeth. とあるので C。

Q3. In this passage, "surface" means ...

1. Athe outside layer
2. Bthe inside part
3. Cthe color
4. Dthe root

surface は「表面」。歯のいちばん外側の部分を指すので A。

Q1. What is the passage mainly about?

1. AHow a German team invented fluoride toothpaste
2. BWhy sodas are bad for children
3. CHow enamel is formed in the body
4. DWhether the advice to wait before brushing is supported by research

「食後は待ってからみがく」というルールの根拠と、その後の研究による見直しが中心なので D。

Q2. What did the 2001 experiment use?

1. AAnimal teeth in a laboratory only
2. BPieces of human teeth exposed to an acidic soft drink
3. CThousands of people eating normal meals
4. DToothpaste mixed with sugar

placed pieces of human teeth in devices worn in the mouth と They exposed the pieces to an acidic soft drink から B。

Q3. Why might the 2001 results not apply to everyday meals?

1. ABecause it used strong acid and only a few participants
2. BBecause it was done too recently
3. CBecause the participants used fluoride toothpaste
4. DBecause the participants did not brush at all

But the study had only a few participants and used strong acid とあり、ふだんの食事とは条件がちがうと推測できるので A。

Q1. According to the passage, what is the basis of the advice to wait before brushing?

1. AFluoride toothpaste is harmful right after eating.
2. BBacteria disappear from the mouth after 30 minutes.
3. CBrushing makes food taste sour.
4. DAcid can temporarily soften enamel, so brushing might wear it away.

Acidic foods and drinks partly dissolve tooth enamel and soften it for a while, and brushing softened enamel could, in theory, wear it away と根拠が説明されているので D。

Q2. What did the 2020 meta-analysis find?

1. AWaiting two hours doubled tooth wear.
2. BWaiting brought no significant benefit for human enamel.
3. CFluoride had no effect on erosion.
4. DBrushing immediately caused cavities.

A 2020 meta-analysis found no significant benefit of waiting for human enamel とあるので B。

Q3. Which statement best reflects the author's view of the evidence?

1. AIt proves that everyone must brush immediately.
2. BIt is weak because no studies have been done.
3. CIt supports brushing soon with fluoride, but it has limits, so high-risk people may need personal advice.
4. DIt shows that waiting is always better.

these studies mostly used small experimental models rather than long-term clinical trials, so people at high risk of erosion may need individual advice と限界を述べつつ、2024年のレビューはフッ素製品ですぐみがいてもよいと結論づけているので C。