Why Your Dentist Is Wrong About Flossing, a Stellar Void, and More

IRA FLATOW: This is Science Friday. I’m Ira Flatow. A bit later in the hour a look at the security of our voting systems and the launch of our next book club. But first, we expect long established healthy habits to be backed up by scientific evidence, and when your dentist scolds you for not flossing your teeth, we take for granted that his claim is backed by years of research. Well, it turns out that’s not the case. The Associated Press reports this week that there’s actually little evidence to support the idea that flossing is good for you. Here to tell us that story and other selected short subjects in science this week is Sophie Bushwick, senior editor at Popular Science joins us here in our CUNY studios. Welcome back.

SOPHIE BUSHWICK: Thanks

IRA FLATOW: Alright, let’s talk. You mean it’s not– So the word on the street is our dentists have been lying to us about flossing all these years?

SOPHIE BUSHWICK: Pretty much. So it’s even in the dietary guidelines for Americans issued by the federal government that you’re supposed to floss to help prevent plaque build up and gum disease. And then when the Associated Press said, ask them for the scientific evidence behind it, there was– he even filed a Freedom of Information Act request for information because he wasn’t getting anything. And then six months later in January of this year they very quietly just removed the recommendation. And when he spoke to them they said, we looked and we realized we couldn’t find any really credible strong studies supporting the use of floss. And so they took it off the recommendation.

IRA FLATOW: That doesn’t mean it’s not good for you. It’s just that there are no studies that have been done.

SOPHIE BUSHWICK: Right. They’ve done a lot of studies on flossing, but a lot of them are just very bad studies. They’ve got a small sample size. Maybe they’re only looking at 25 people, or other ones looked at only a very short period of time, say 2 weeks. And then, still other ones weren’t actually looking at the stuff we want to know about preventing cavities and preventing gum disease. Instead, they looked at something like bacteria.

IRA FLATOW: So, but when you take that floss out, you see all this gook on it, don’t you?

SOPHIE BUSHWICK: Right. It seems like it should be something that’s true but–

IRA FLATOW: It’s flossiness.

SOPHIE BUSHWICK: It’s flossiness.

IRA FLATOW: How did it get started? Did somebody just making it up some day?

SOPHIE BUSHWICK: Well, it kind of got started– well, back in the day when floss was first invented, that was over 100 years ago. And then companies started patenting it, and companies that made floss were doing their own studies. But again, a lot of these were just– there wasn’t a really strong basis of fact behind it. And so when it turns out that when they were formulating these dietary guidelines, they just didn’t have really good science. And even dentists associations that say this is a recommendation from the American Dental Association, they cited studies that were very weak.

IRA FLATOW: OK, let’s move on to what astronomers have found, or I guess it’s better to say what they have not found out there in the middle of our galaxy.

SOPHIE BUSHWICK: So these astronomers were looking for a kind of young star called a cepheid. These are about 10 to 300 million years old, as opposed to our own sun which is a few billion years old. And they were looking for them in the center of the galaxy. And what they found is there’s cepheids in the middle of the galaxy out to a distance of about 150 light years. But from that point out to 8,000 light years, there’s this ring where there’s no cepheids in it.

IRA FLATOW: There’s a hole in the bottom of our galaxy.

SOPHIE BUSHWICK: There’s a hole. Yep.

IRA FLATOW: Wow. Do they have any idea why that is?

SOPHIE BUSHWICK: They think– Well, the fact that cepheids are so young, this suggests that new stars aren’t forming in that area, and probably haven’t been forming for maybe 100 million years or so. And the question is, what is causing this. And so the researchers think that by further studying it, they might be able to tell how the Milky Way is evolving, and maybe will continue to evolve.

IRA FLATOW: All right. Let’s move on to this next story about something called, and this is fascinating, neural dust.

SOPHIE BUSHWICK: Yes. It’s a great name. So this has to do with existing research. Researchers are making these amazing breakthroughs with implanting electrodes into brains, and using these electrodes to measure what the nerve signals are doing. And so when they’ve done this, for example in monkeys, the monkeys were able to control an external robotic arm just using their brains. But the problem with this type of implant, is it’s got these wires attached to it, and the wires have to run through the skull outside the head, and that’s just not feasible. That irritates the body. It’s not good for a long-term implant. So what researchers at UC Berkeley are doing are creating this neural dust, which could be implanted into the body and then get wireless power from an ultrasonic source outside the body. So they wouldn’t have any wires, and they could stay in the body for maybe up to 10 years.

IRA FLATOW: How do they get it to your brain?

SOPHIE BUSHWICK: You would have surgery to implant it in the brain. And right now, of course, this is really early stages. They haven’t looked at it in the brain. They’ve looked at it in rats in the peripheral nervous system. So the nerves running to the arms and the legs. And also, another thing is that right now it’s about three millimeters long. So this sounds pretty short, but what they’re hoping to do is shrink down each implant until it’s more like 50 microns. Half the width of a human hair.

IRA FLATOW: Nanoparticle size or a little bigger?

SOPHIE BUSHWICK: Microparticle, I’d say. Yeah, they’re thinking like 50 microns.

IRA FLATOW: And they can implant it in your brain. I’m opting out of that one. Finally, let’s talk about rich people. Rich people have more of everything including more insects in their homes?

SOPHIE BUSHWICK: It’s true. Some researchers a while back did a survey of bugs in homes and they looked at 50 homes in and around Raleigh, North Carolina, and they went over them with a fine tooth comb cataloging all the arthropod that lived in there. And what they found was in wealthier homes, where there’s an average income of about $176,000 a year, you have about 100 different arthropod families. But when they looked at less wealthy homes with an average income of $33,000 a year, they found only 74 arthropod families. So this means you’ve got more biodiversity in wealthier households.

IRA FLATOW: And how did all the bugs get there?

SOPHIE BUSHWICK: It’s because of landscaping. So if you picture sort of wealthier neighborhood, you think of these rolling green lawns and having maybe a flower garden next to the door, and these are environments that foster a lot of biodiversity in bugs and in animals. And because the way bugs get inside is most of the bugs in the house are bugs that wandered in from outside. So it makes sense that in houses where you’ve got a greater variety of bugs outside, you’ll have a greater variety inside.

IRA FLATOW: Here in the big cities like New York, we have lots of bugs, but they sort of crawl out in the middle of the night. You know, when you turn on the kitchen light–

SOPHIE BUSHWICK: I would much rather they stayed that way. I don’t want to see them in the full light of day.

IRA FLATOW: All right, Sophie, thank you very much. Sophie Bushwick, a senior editor at Popular Science, who is joining us here in our CUNY studios. Welcome back. Good to see you.

SOPHIE BUSHWICK: You too.

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