Understanding Sentences about Flossing

Question

In a news article about the benefits of flossing, the following sentences confused me (please read the article first):

In the past decade, three systematic reviews sought to navigate these muddy waters.

The first, published in 2006, narrowed its focus to the effects of flossing in young children between the ages of four and thirteen. The reviewers found that children who had their teeth flossed by a professional hygienist five days per week for 1.7 years had a 40% decreased risk of cavities.

In this excerpt, does "review" mean "looking back at a study that was conducted previously" or "experiment" as in "three systematic experiments"?

1. Is it saying that some people (A) are looking at some other people (B)'s work and found the statistics and listed them in the excerpt?

2. Or is it saying that the people conducted the experiment in 2006 and found those statistics?

Also, later in the article, they stated that

Since daily flossings by trained hygienists aren’t available to the general public, the researchers admitted that their findings were limited.

Is the "researcher" mentioned in the above excerpt the same as the "reviewers" in the first excerpt?

1. Are the reviewers the ones doing the research?
2. Are the reviewers the ones looking at the research and drilling holes in it?

Answer 1

Stage One, 'Experiments' are run by a team of researchers;

Stage Two, the experiments are written up in 'studies;'

Stage Three, several studies are looked at for quality, and similar studies may be combined in a 'review;' one of the reviews is a review of 'three systematic experiments.'

Stage Four, in this article these 'reviewers' are analysing several previous studies and several previous reviews of studies. The word 'reviewers' is only used on this page to describe the authors of the "Stage Four" review.