Science Friday - Ask A Dentist. Feb. 21, 2020, Part 1

Episode Date: February 21, 2020

Brushing Up On Tooth Science Most of us spend our time at the dentist holding our mouths open, saying “ahhh,” and occasionally sticking out our tongues. But if you could ask a dentist anything, what would you want to know? Ira asks University of Utah researcher Rena D’Souza and UPenn’s Mark Wolff about cavity formation, the oral microbiome, gum disease, and the future of stem cells in teeth restoration. Plus, NYU researcher Rodrigo Lacruz explains new research on how excessive fluoride can disrupt tooth cell functions and why you should still keep drinking that fluoridated tap water.  East Africans Battle A Plague Of Locusts Brought On By Climate Change A swarm of locusts the size of a city may sound biblical, but it’s the reality right now in East Africa. The pest is devouring the food supply of tens of millions of people, wreaking havoc on crops and pasturelands. Local residents are doing all they can to keep the swarms at bay, but the locusts may be here to stay for a while, as experts suggest their presence may be due to climate change.  Sarah Zhang, reporter at The Atlantic, tells us about the locust issue along with other science news from the week. Why Coal Country May Be Going Solar A new bill passing through the West Virginia state legislature would increase the state’s solar capacity by 2,500%. Environment reporter Brittany Patterson at West Virginia Public Broadcasting tells us the State of Science.   Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Plato. A swarm of locusts, the size of a city. Well, it may sound biblical, but it's the reality on the ground right now in East Africa, where the pests are devouring the food supply of tens of millions of people, wreaking havoc on crops and pasture lands. Local residents are doing all that they can to keep the swarms at bay, but the locusts may be here to stay for a while, as experts suggest, their presence may be due to, you know, climate change. For more on that story and other short subjects in science, we're joined by Sarah Zang, staff writer for the Atlantic. Welcome back, Sarah. Hi, Ira. Good to talk to you. Locust swarms, the size of cities? Tell us about that.

Yeah, it's almost hard to imagine, right? It's really the worst locust swarm in recent memory in East Africa. These swarms, they'll just land in the field of crops in the morning, and by afternoon, they'll just devoured and strip the entire field of all leaves. And so the reason, as you say, that there have been such huge swarms is because, because of rain. So desert locusts, which is what these swarms are, they laid their eggs in the soil. And starting about a year ago, there have just been several cycles and have just dumped rain all over the region, which helps trigger these eggs to hatch. So you might have several years

worth of eggs hatching. And locusts, they reproduce really quickly. So once they've hatched, they might have a new generation in just three months. And with each generation, the next one can be is 20 times as big as a previous one. So you can imagine in less than a year, you might have three generations, the number of nocus has just gone up by 8,000 times. So over the past year, they've just been exploding in numbers and migrating across the region. Anything you can do about it? Well, unfortunately, it's probably going to get a little bit worse before it gets better. You might be able to spray insecticides, but, you know, it's a huge region, and there just isn't always a civil infrastructure to cover everything. There's a lot of rain expected from March through May as well,

so there's probably going to be even more in the focus of the next few months, and eventually the rain stopped. Hopefully it will let up. Speaking of agricultural pests, farmers in Florida, I understand, are trying to save their orange crops from citrus greening disease. Tell us about that. Yeah, they're actually spraying pesticides. Sorry, not pesticides.

They're spraying antibiotics that are used in human diseases on their trees. So this is really an act of, if not last resort, really some desperation. So as you mentioned, there's this disease. called citrus greening disease, which over the past 15 years, this has just really devastated the Florida citrus crop. It's dropped something like 70%. This disease, which is a bacteria that affects trees, causes the trees that grow smaller fruits. And when they do grow them, they also turn green and kind of fall off the tree before they're really ripe. And so starting in 2016, and the EPA, the Environmental Protection Agency recently allowed, renewed this to allow farmers to use

emergency applications of human antibiotics. The idea is that if these human antibiotics work against the bacteria that cause human diseases, that may also kill the bacteria that cause citrus greening. The problem is that these are some of the same antibiotics that if you or I go to a doctor, for example, UTI or tuberculosis, those are the same antibiotics that they might be prescribing us. So experts are also really worried that this might lead to antibiotic resistance if farmers are just spraying acres and acres of citrus trees. Yeah, you know, walk through a cloud of that, right? Or it drifts and you're getting antibiotics, which is not a good thing.

Yeah, exactly. And the other controversial part is that sometimes it's not clear exactly how well it works. Maybe it doesn't get into the tree, so sometimes people have been trying actually injecting the tree itself with antibiotics. Of course, then you get the problem that the antibiotics are actually in the tree itself and maybe even in the fruit itself. This is a real experiment going on at that. time. Okay, let's move on to something else, something I never thought it'd have to think about. Researchers have identified that it only takes six weeks to compost a human body. That's right. So the reason researchers are actually trying this is that last year, Washington

State became the first state to legalize something called natural organic reduction, aka human composting, which a way to deal with dead bodies. So in a recent small study, scientists put six human bodies that were donated to science in essentially a large composting drum, along with some plant materials such as wood trips and alfalfa and straw. And they gave it a turn every few days as you would with your compost bin in your backyard. This is to make sure the microbes of oxygen. And so after four to six weeks, you end up with a soil-like material. And one human equals about one cubic yard of this compost. I'm not going to find that at Home Depot soon. Probably not.

I don't think so. So what do they do with the bones? What do you do with it? And you know, can you take Uncle George after he dies and just put them in your backyard in your garden? Yeah, that's the idea. So the bones itself actually also compost. But as I mentioned, one cubic yard of compost is actually a lot of material.

So there's a company that is trying to get this started by the end of this year. And it's actually kind of an open question. Our family's going to want to take all of this compost or will have to find other ways to maybe use of this human compost. Oh, I see one of these investigative detectives shows where they find the body in the compost or so that's just, he was just there naturally. Okay, let's move on because there are a lot of questions there. It seems like there have to have to be lots of rules associated with this, but we won't get

into that now. And I don't know. Are other countries doing this? Is it just a follow up? Yeah, no. Not though. Not, no. So Washington's actually the first state to do this.

And the idea behind it was really that, you know, dying in America is in some ways not a very green, right? Because we either cremate, which takes a lot of energy, or we bury people with a lot of embalming fluid, some of it, which is toxic, which can get into the water and the soil. So the idea is that this is a greener and more natural way to deal with our dad. We'll keep our eyes on it. Finally, scientists are looking into the medical usefulness of lobster blood, right? I know they use horseshoe blood, right? Yeah, exactly. So just a quick aside on horseshoe blood.

They're actually kind of scooped up out of oceans and blood for their blood because they're really good at detecting bacterial toxins. So we don't know yet about the exact properties of lobster blood, but there's a company in Maine that is trying. Lopster blood is that like bluish-gray stuff if you ever handle the raw lobster. It's a technical hemolymph. And what's kind of really interesting to me about this story is that Maine is at the end. of a 20-year boom in, like, lobster harvest. And so basically, Maine is just trying to figure out what to do with all of the parts of the lobster that they can't eat. So they have shells that they're turning into fertilizer, and now they're saying, well, there's this blood that's just literally going down the drain.

Let's see if we can find some uses for it. Yeah, a live lobster is not red. That's right. That's right. Thank you, Sarah. The interesting stuff. Sarah Zangstaff writer for the Atlantic. Thanks for dropping by.

Great to be here. You're welcome. And now it's time to check in on the state of science. This is KERNO, St. Louis Public Radio News. Iowa Public Radio News. Local science stories of national significance. You know that West Virginia, right, is coal country. But as of this week, state lawmakers are paving the way for it to be considered a solar country, too.

It's perhaps the last state you'd expect to adopt stronger renewable energy policies. Lawmakers are saying the economic benefit can no longer be ignored. For more on this about face, we're joined by Brittany Patterson, Energy and Environment Reporter for a West Virginia public broadcasting. She joins us by Skype. Welcome to Science Friday. Hi, Ira. So when did this finally sink in, West Virginia? Yeah, I mean, there have been some lawmakers talking about the need to expand solar in West Virginia.

But, you know, this is a state that is more than 90 percent of the electricity generated here is by coal. So what this bill would do is create a utility solar program. So it would be 400 megawatts of solar, 200 each by the state's two major utilities, and they could implement it in 50 megawatt chunks. Once they sold most of it, they could start building more. And this bill passed out of the Senate on Valentine's Day, actually, and has moved over to our House and is sitting in the House Judiciary Committee, and I talked to that committee chairman this week, and he says he's going to bring it up.

So if it gets out of that committee and goes to a house vote, there is a good chance it could pass. But this is pretty small potatoes, speaking of electricity. 50 megawatts chunks are not very much. Yeah, but to put it in perspective, we have about 8 megawatts of solar installed here in West Virginia right now. It says like one solar power tower. Yeah, you know, it's about enough solar power to power about 800. homes. So if we were going to fully implement this bill, all 400 megawatts, that's 50 times as much solar as we have right now, about 40,000 homes. That's not bad. Not bad at all. And what about if you want to

put your own solar panel on your own home? Can you then feed the grid and get maybe make some money back? So that is illegal here in West Virginia. And bills that would address that and make these third party solar installations legal have stalled. They haven't moved in the legislative session like this bill. And that's one of the reasons that there has been some opposition to this bill is that there's been some argument that it really puts more power in the hands of our already powerful utilities here in West Virginia. It gives them most of the monopoly on installing solar power and makes it, you know, doesn't make it any easier if you or I wanted to put solar panels on our homes. Has the coal lobby been pushing back on this? Yeah, we definitely heard some opposition from the coal lobby here in West Virginia, and, you know, also from a lot of lawmakers. There was some really, there was some education that needed to happen, not just about how the power grid works, but about how solar works.

And, you know, one main concern is that we install more solar and less coal is used. And there's actually provision in this bill that requires that we can't take any coal generation off. line. It's more about adding this solar. And what's interesting is the reason why this bill came about in the first place is because the State Department of Commerce asked for it. We heard testimony from our Commerce Secretary who said, hey, when we try to learn new businesses here to West Virginia, the first and second question they ask us is, can we have access to solar, renewable energy? And unless this bill passes, they can't. Wow, that is really interesting. People asking for it. that's kind of a game changer because you're talking about jobs, right?

They lose jobs coming to the state. Absolutely. Yeah, absolutely. And that was an argument that we heard from officials is that, you know, when the sun's not shining, if we can lure these new businesses to the state, they'll be taking power from our mostly coal grid during the nighttime hours. So this is a win-win, but it was definitely framed as a jobs proposition. So we have to watch a wage is way through the political system now? That's correct, yeah.

still needs to pass the House and then be signed by the governor. Though we have heard indications that he does support the bill. Great. Thank you, Brittany, for that great report. Brittany, Patterson, Energy and Environment Reporter for West Virginia Public Broadcasting. Thank you for taking time. Thanks for having me. You're welcome.

We're going to take a break, and we have questions. You have questions. We have answers about teeth. You always wanted to ask a dentist something which you couldn't because your mouth was, you know, full of all that stuff. Well, now we're going to have two dental experts on with us. You can ask a dentist anything you'd like to, our number 8447248255. You can also tweet us at SciFri. It is your chance to ask a dentist not only about your teeth but about research.

What's going on with dental research? So we'll talk about it after the break. Stay with us. This is Science Friday. I'm Ira Plato. Few doctor office visits are scarier than going to the dentist, right? There's the prospect of painful teeth scraping, invasive x-rays, not to make. mention the needle, the Novakane.

Notice I left out the dentist drill. I don't even want to go there. And when it's all over, your reward might include my cleaner teeth, a new filling, and a lecture on flossing more. Oh, don't forget that new hygienically wrapped toothbrush you get to take home. But what about all the other questions you were asked or you wanted it answered? How often should your brush? Is twice a day enough? What's the best floss to use?

What about mouthwash, fluoride, avoiding sugary foods? Of course, there is more to dentistry than filling holes, like, what's the latest in dental research? Will it be possible to one day grow back that impacted wisdom tooth I had removed? So we wanted to give you a chance to drill the dentist. That's what I did there, with questions of your own. So for the rest of the hour, it's time for ask a dentist. We'll cover the future of cavity prevention. what's new in tooth repair and how your genes may determine your gum health.

Oh, so much more. What would you like to know? You got a molar mystery to crack? Are you bicuspid curious? Yes, we want your cavity questions or grill us about the gums. You make the call. But only if you make the call. Our number is 844-724-8255-8-44-Sai Talk.

You can also tweet us at SciFri. Let me go. I'll try to keep all the dental puns out as much as I can today. Let me introduce my guests, Dr. Mark Wolf, Dean of the School of Dental Medicine, the University of Pennsylvania in Philadelphia. Welcome back, Mark. Hi, Ira, great to be back. You're welcome.

Dr. Rina DeSouza is professor of dentistry at the University of Utah in Salt Lake and former president of the International Association of Dental Research. Welcome, Dr. Sousa. Thank you, Ira. I'm a big fan. And a very loyal NPR devotee. Well, that's good. So I'm happy to be here.

Nice to be there. We're not at NPR, but we are public radio. Public radio, sorry. Okay, let me ask you. Let me ask you then, first, Arena. How do cavities form in the first place? What do you need to have a cavity form? Yeah, I think, you know, if you looked at the enamel that we see visibly,

coding the crown of a tooth, it is 97% mineral. So obviously, when you have something that is so hard and the cells that produce it are no longer in the mouth, then it's very susceptible to biofilms and deposits that lay on the tooth. So when you have a biofilm that builds up over time with bacteria, bugs being attracted to the film, and you provide these bugs with a lot of food. and typically that is substrates from carbohydrates principally. And then that interaction creates acids because the bacteria actually dissolves these food substances and produces acid that then dissolves that very hard surface of enamel that is made out of appetite.

And that is the beginning of a cavity. Dr. Wolf, why do we see cavities mostly where the teeth touch each other? So there's two reasons for that. One is that's where the sugars can get into and stay there. And second, saliva contains a number of things that actually can neutralize the acid that contains bicarbonate. It also can rinse away those foods, and it just can't reach in between the teeth easily. So the bacteria sit and eat, and they poop acids. Okay, now I've got a better mental picture of that.

Well, they don't hate us. All they do is eat, poop, and reproduce. And if we let them build up in a location, they have a nice family that eats lots of sugars that are readily available because of our diet, and they poop lots of acids, and we get cavities. All right, we've got so many questions. Let's go right to them. Let's go to Rich in Charlotte, North Carolina. Hi, Rich.

Hey, hi, hi, hi, there. Go ahead. Ask a dentist. I've recently dental visit to my middle-age student. They found a cavity on the outside and also where the bridges are on the top of the tooth. And they proposed the option of drilling and filling. And I'm just wondering, is it possible for an early stage cavity because it doesn't actually show on the x-ray? Is it possible for it to be reversed and possibly remineralized or repaired in any fashion without having a drill?

That's a great question. Mark, you want to take it? Yes. Yeah, that would. Monco. Oh, okay. So the answer is not all cavities can be seen. on dental x-rays, but if it's an early lesion just starting, they can be reversed by keeping

the sugars out of the mouth, reducing the amount of plaque that's in the area, but you have to do really well with that. But more importantly than that, we have agents like fluorides, which can help remineralize those surfaces and actually pack the mineral back in and make the tooth healthy. It's possible to take early tooth decay and totally reverse it and keep you in a healthy state. Because you brought it up, I was going to ask this later, but I'll ask it now, how important is it for you to have a dental x-ray? Because I've known dentists who say, you know, a good dentist can find a cavity or not subject you to x-rays that might be invasive in your brain or something like that. So that's exactly what was written in 1913 by the great-grandfather

of dentistry, GV. Black, that give me a bright light, a mirror, and an explorer, and I can find all tooth decay. As it turns out, dental radiographs help us find tooth decay at earliest stages where it is totally reversible. That being said, we should take as few radiographs, as few x-rays, as is indicated by the amount of disease the patient has. So if you're 30 years old, you've never had a cavity, your teeth are clean, your gums are beautiful, everything's working well, you should probably only get dental x-rays every two to three years. On the other hand, if you're a cavity machine and you're constantly making tooth decay, you need a more frequent radiograph annually, probably, but it's directly related to your risk of developing the disease.

Gina, tell us about periodontal disease. What is that? I'm glad I can talk about it because the The radiograph actually can go beyond detecting early decay or advanced forms of decay. So the peridonium is this hammock that keeps the tooth anchored in bone. And we need that hammock. Otherwise, we'd be chipping off teeth as we put forces on them as we eat and chew and things. So this little ecosystem that the peridontium is is very, very much in homeostasis and balance. Now, we can accept that just the way Mark talks. If we have a bar of film and plaque that develops over time, it attracts certain bacteria or bugs that love to spit out harmful products.

Now, in the case of peridontal disease, these harmful products actually seep into that crevice. And as they get deeper and deeper, they cause destruction of that attachment. And that is what we call the pocket that the dentist will probe. and it's a tough, tough ecosystem to get back to normal. So we strive in dentistry to keep gums healthy, to keep the inflammatory products that are the result of improper or not so good oral hygiene very much at the optimum. And that involves diet, it involves toothbrushing, flossing,

being aware of how your teeth are positioned, and taking care of each of these structures, that nature has given us for so many functions and take care of it by in multiple ways. So I think I capture the essence of paranormal disease. Well, I wanted to ask about a little bit more about that. Does gum disease have any indication about diseases in other parts of your body? Root, Rina. Yes.

Well, the oral cavity, to be honest, is truly the portal to the rest of the body. I mean, that we know because we're connected to the oral cavity, to the rest of the body. And I must say for centuries now, we've known about the implications of oral and systemic conditions. So the bacteria that produce these harmful substances, they circulate in the system. And very often they travel to distance sites. And so there is an association now building up between periodontal disease and susceptible heart valves or periodontal disease and pregnancy and early birth term rates. There's also a connection, believe it or not, between peridontal disease and Alzheimer's,

where the enzymes that are found that are actually common to both conditions. So clearly, the oral cavity is the portal. It is very much taking care of oral health is almost imperative for general health. And I'll give you what seems to be a negative answer. But if you think of what happens in the oral cavity, if you have dental a toothache, It's one of the worst pains you can endure. If you have a child who's born with a cleft palate, who can breastfeed or eat normally and requires extensive surgeries, if you have an autoimmune disease where your salivary glands are no longer functioning normally, or you've had cancer radiation therapy and they don't work, so you have a dry mouth, or you have cancers that are detected too late in the oral cavity, and you have to have half your tongue removed and half your lower lower.

jaw removed, all of that means that this part that we protect so vigorously in dentistry is really important for our overall health and well-being. There's another dental routine you might do every day without even thinking about it if you drink tap water in the U.S. Chances are good that there's fluoride in and that is not an accident. And when swallowed early in life, fluoride helps your dull teeth develop with a stronger kind of enamel than it might otherwise have. And later in life, fluoride that touches the tooth surface can help weaken spots remineralize, as we've talked about, to prevent cavities.

I want to bring on another guest, though, to talk about some new research. There's such a thing as too much of a good thing. Research shows that excessive fluoride in children can actually lead to weaker teeth. How does that happen? Dr. Rodrigo Lucruz from NYU's School of Dentistry is here with this new research on how fluoride affects calcium flow and tooth cells. Welcome to Science Friday. Thank you very much. Okay.

Thank you. So how can fluoride be too much of a good thing? So too much of a good thing. I'm not sure that that's what I would say, but what we were saying in our research is that fluoride is a very good thing in the right amounts, and so it's been known for decades that when there's an excess of fluoride ingested, causes a disease or a defect called dental fluorescence. So what we were trying to address is how the cells manage this fluoride and what are the effects in the cells caused by fluoride.

Excess of fluoride, that is. So what is going on with the excess of fluoride? So what we found in our research is that the calcium levels within the cells were disrupted, and we looked at a number of enamel cells. We looked at primary cells, taken from laboratory animals and so on. And so it's important for cells to maintain the appropriate levels of calcium within the cell for a number of reasons. And so how do the cells maintain these levels of calcium within the cell? One of those is to move calcium from the cytosol into one of the organelles called the endoplasmic reticulum,

and the endoplasmic reticulum needs calcium. So to do this operation, there is a pump in the membrane of the reticulum, which transfers calcium from the cytosol into the inside of the reticulum. And so when this pump is disrupted, cells undergo stress. So in our experiments, I think what we did is we looked at why the pump was not functioning optimally in cells treated with excessive fluoride. So this is trying to mimic what we see in the defect, not in the right amounts of fluoride, which is good, but only during the disease state.

And so what we found is that... The magnitude of that fluoride? Sorry? What was the magnitude of that fluoride exposure? So we looked at about 19 parts per million and something a little bit lower. So these are levels of fluoridation that you see in the waters of Estafka, for example, where this naturally occurring waters contains this amount of fluoride. Yeah, but routine water fluoridation is one part per million.

I'm sorry, Ira. It can only be one host at a time. Let me just remind everybody, and I'm Ira Plater. This is Science Friday from WNIC Studios. So, Rodrigo, you're not saying that adults should be afraid of consuming too much fluoride. You said that already. But you also say that kids should be prevented from swallowing their toothpaste that has fluoride in it. Yes, that's right.

I think one of the major issues in developing countries is that there's an excessive consumption of fluoridated toothpaste. So when you add that ingestion of fluoride, and that tends to happen in younger children, the ages of two, three, and four, for example, and when they do brush the teeth without supervision, this can happen. And if you add that consumption of fluoride to the drinking of water

and things like that, this accumulates over time. And so that can have a negative effect. So in how many places around the world is this a problem? in many places around the world. It's a minor problem in the United States. We have very good controls of fluoridation of water. Some areas of the United States have slightly elevated levels of fluoride, naturally occurring in the water, but it's very prevalent in many countries.

In India, for example, many millions of people are at risk or do have fluoresces. In East Africa, because of volcanic activity there, the waters naturally contain high levels of fluoride. So it's a very important problem across the globe. Dr. Rodriguez-Lau-Cruz, Associate Professor in NYU's College of Dentistry. Thank you so much for taking time to be with us today. My pleasure. Dr. Markwell, did you want to jump in on that? Yeah, I'm sorry, Ira.

We just need to make sure that the public is an understanding that the water levels of fluoride that we see in the United States are 0.1, 0.7 to one part per million. and what Rodrigo was referring to was 19 times that. We don't see that even in our worst areas in the United States with fluoride exposure in the water. This is not the type of cell issues that he was referring to are not specific to what we see here in the United States. Yes.

I could I add a dimension of understanding? I've got a minute. Until the break, go ahead. Okay. So what is really important is, is that teeth form in utero. So teeth are wonderful biologic hardware to record exposures to environmental toxins,

which could be fluoride if it goes over a certain amount, but they serve as wonderful registers of exposure to environmental toxins during prenatal development or during pregnancy. So when we consume high or exposed to high levels of bisphenol A, which is a common ingredient of plastics, and different phthalates, it gets recorded in teeth as little hypomineralization or a little white lesion defects.

So teeth are biological hallways, a very important indicators of exposure to the bad stuff that we expose to. That's interesting. And fluoride is an important example. All right, thank you. Could be. We're going to come back and talk more with Dr. Wolf and Dr. DeSuzza, and we have all kinds of questions.

The rest of the hour, we're going to just take all the phone questions and Twitter. tweet questions. We have all kinds of stuff like, why did gums recede? You know, what is, what is happening there? What is, what, I got so many here. I can't bring them up before we go to the break. Our number 844-8255. You can also tweet us, as a lot of people are doing at SciFRI. Ask a Dentist returns after the break. Stay with us. This is Science Friday. I'm Ira Plato. We're talking this hour about dental health, new research, taking your questions. It's Ask a dentist with two dentists, Dr. Mark Wolfe, University of Pennsylvania, Dr. Rina D'Souza, Professor of Dentistry University of Utah, our number 8447248255. We also had our Vox Pop working this week, and we had people wanting to know about dentistry, and this one from Barbara and Melbourne, Australia.

I want to know why we still don't have a carrius vaccine or a probiotic treatment that can neutralize harmful carous bacteria. And another from Bonnie in Milwaukee. I'm wondering if mouthwash harms the good bacteria in my mouth, or is it specifically formulated to only go after the bad bacteria, like my hygienist says? No, we have tweets that came in like that. That's why I chose them. Let me work backwards. Dr. Wolf, what about the mouthwash question?

Does it kill the good bacteria as well as the bad bacteria? Some mouthwashes are essentially perfumes. Other mouthwashes actually can kill bacteria, and they tend to be non-discriminate. They kill good bacteria and bad bacteria. This biofilm plaque that we refer to is an ecological colony. It's got lots of bacteria in it. And it's probably not the best way to manage it going in there and just trying to kill everything.

And Rina, what about this question about vaccine? Why do we still not have a vaccine for cavity? Because honestly, I think the disease is a multifactorial one. and it's complex. And we have just, for reference, 20 million microbes that reside in the oral cavity, just slightly lower than what's in the gut, right? So when you're thinking of a multifactorial complex condition

that develops because of environmental influences, it does take some sorting up. But I feel very optimistic. The microbiome era that we're in right now that became possible because of the genomic era offers us a tremendous opportunity to actually look at the connections between these bacterial colonies and viruses, by the way, as well, and also the connection between the oral microbiome and the gut microbiome. So the fact that we would have, if not a vaccine, but agents that actually selectively suppress the acid-producing bacteria

whilst keeping the rest of the relationships intact is probably likely the more practical way. to go in for it. And there is a product that is being developed right now, I think. That's a good segue to my phone call with Fred in Phoenix. Hi, Fred. Hi, how are you? Hi there. Go ahead.

Yeah, you know, I wanted to ask, you know, if there's any research going on into public mouth rins or, you know, mouth washes, you know, just to kind of encourage the positive bacteria in the mouth instead of the negative. Probiotic. mouthwash, good question. Any answers? Dr. Wolfe. There are plenty of, there's lots of research in this area, and whether we're talking about prebiotic, essentially fertilizing the plaque with something good that makes something good grow, or actually probiotic, which is introducing a

healthier bacteria. There's lots of work going on in this arena right now, and there are a number of toothpaste that are emerging with this as therapeutic abilities. It's showing up very positively in the research. Why not just eat yogurt and let it sit on my teeth? I'm serious. No, it's hard to get, it's hard to get bacteria into that ecosystem. So it's why when you talk about probiotics, they talk about you taking it every day and consuming it. It's tough to get healthy, bacteria to come into one of these biofilms that's well established. All right, let's go to the phones to Dana in Portland. Hi, Dana. Are you there?

Earhart in Portland. Hi. I'm Gerhard. Yes. I'm Gerhardt. Go ahead. Hi. Thank you for taking my call. I'm wondering about gum health. What sort of tissue are my gums? And do I have any hope of encouraging them to regrow? I have received gums. Good question. I think we all need. that advice.

Arena, do you have any advice? Yes, because, well, your gums are actually made out of the same fibers that are beneath your skin. So it's type 1 collagen and a few other collagen. And so that fibrous nature, as we get older, the number of cells we have to produce that collagen declines, right? That's why we sag and drag and things and we develop wrinkles. and we don't heal as spontaneously as we do when we're younger. So that applies as well to gingerous.

So we recede, our gums recede and create these little annoying black triangular spaces between teeth. And I must say it would be wonderful if we could come up with a way to rejuvenate these cells, either through activating stem cell populations that reside naturally in our mouth to kind of regrow. that research is ongoing, and I think it would be a wonderful way to not get things stuck between your teeth, that you've got to pull out with toothpicks and things like that. But it is a very annoying problem. If I brush vigorously and my gums start bleeding, is that a bad sign? Am I wrecking some of the tissue? Am I ripping it out? Well, if you think of the root of all evils, it is inflammation, right? So the inflammatory products of harmful effects on our tissues is normally manifested by blood vessels proliferating.

So they come to the surface and that makes them very susceptible to injury. So when you're brushing in a normal healthy mouth, you should not have bleeding. But when your gums are unhealthy and they're puffy and you have these barfilms all messed up and bad bugs and bad food substrates, then you're likely to cause more information and that means more enlarged blood vessels that are very susceptible to breakage and bleeding. Yeah. So it's not good. Not good.

Let's go to the phones. Oakland, California, where Michael is. Hi, Michael. Hi, Michael. Hi there. Do you experts know anything about a possible update or re-application of the American Dental Association 2011 guidance document on the use of fluorated water in infant formula? Mm-hmm. Not me. I do not.

Rina? You know, I'm going to try. I forgot what the latest iteration was on that topic. So I would also defer from an opinion right now. Here, I have a tweet coming in from Rabbi Ruth Adair. Hope I'm pronouncing it right, like the month. Does whitening damage health? No. Does it damage teeth?

No? No? Not when used according to instructions or reasonably. You can overbleach and actually strip the color out and teeth start to look gray and translucent. But when used normally, when used as a daily whitening toothpaste of an over-the-counter type whitening toothpaste, they haven't been associated with any damage to the enamel or to the tooth structure. They prevent stain from building up. They can whiten the tooth structure.

and they're fine, but you shouldn't be using commercial products that are designed to use for one week and use that forever. I agree. Is home remedy, the stuff you can buy in the drugstore for tooth whitening, is as good and effective as what your dentist would do for you? I don't. So most of the research says that dental supervised whitening can be better and more aggressive, but the over-the-counter whiteners, produced by a myriad of reputable companies, has been shown to really do a nice job at providing some whitening. Let me go to the phones again, to Mearside in Columbia, South Carolina.

Hi there. Hi, how are you guys? Fine, how are you? Go ahead, please. I like waterpick, dental waterpick, and my wife is big on dental flossing. So we always argue which I think is better. Is there any science in it comparing these two methods, which is actually better for your teeth maintenance?

Prina, can you tackle it? That is, it really does come down to a personal choice. And you can imagine the physical effect of spraying water under pressure. You're not having to deal with two hands necessary that have to delicately string into a tight space. and likely damage the tissues underneath. So the ladder requires more dexterity. I would say that I would lean towards the water pick

as being more able to flush out and invigorate and actually massage the tissues around that flossing may not do so well. That would be my instinctive comparison. I just have to ask you just for the record. You don't work for the water pick people. No, I don't. Not at all. I'm a lab rat.

I have a tweet that came in that something that I've been wondering about for years. Magalie says, should you floss before or after brushing? Do you want to comment, Rina? There's no science that actually shows one better than the other. Exactly. So my colleague, who I practice with in Houston, George Sayer, would always give this wonderful anecdote that if you take your hand, spread your fingers out a little bit, dip it into a can of paint, and then pull it out and then put your fingers together and brush them off and the paint would

wipe off but not between your fingers right so if you think about that analogy then obviously you want to brush first and brush thoroughly and then floss and perhaps do a rinse after that so that the looser fragments that are stuck between your teeth that the floss didn't get to can be flushed out by by physical force and that's what a water pick would do okay yeah Do both of them. Doesn't matter which order. Let me ask you about some research. We want to touch on some before we have to go.

What is the latest research on types of fillings, filling technology, filling your cavities and teeth? So you want me? Yeah. So the growing controversy is that amalgams that contain mercury alloys, that are mercury alloys, are harmful. Because, again, we're putting a metal supple. in the oral cavity and we tend to in dentistry be very advanced with our material development so right now we are trying to find a replacement material that has the aesthetics the durability and can withstand the stresses we place on the tooth

which is quite intense to replace that silver filling so there is a move now to create these new hybrid composite materials that look like the tooth that have anti-microbial properties that also can last a long time and really be the great substitute for Malam. So I see a very promising research in that area. Interesting. Very exciting stuff. That's great. I'm Ira Plato.

This is Science Friday from WNYC Studios. Answering as many questions as I can. I have never seen the board so lit up in our tweet. So many tweets. Let me go to this tweet, which is something I was going to ask. Anyhow, and Richard Watson asks it, why is dentistry insurance covered separately from general health insurance? Mark? Wow.

So, and that has to do with our employers and our government. So, for instance, Medicare covers your medical care as you turn age 65 or older, but there's no dental benefit. That was a decision that was made in the early 1960s when life expectancy was just about 68 years of age. and they said, well, we don't really need dental insurance. That's not today, and it's not what's healthy because, as Rina said, oral health is part of general health, and that's an issue. Our employers have the option to get purchase for us and have us contribute to the very best in dental insurance. It's expensive, and some employers choose to do so. Most do not. to say that there are lifetime caps on orthodontic care and periodontal care,

to say that adults don't get fluoride treatments, but children can, even though we know fluoride can help reduce decay in adults who are getting decay. This is a pretty backward step, and many of the insurers are stepping up to deal with today, and some of the states in the United States are actually doing a lot better, in providing adult dental care as part of a total health benefit. Do we know if any of the candidates, when they talk about Medicare for all, or Medicare for all if you wanted, do they cover dental also, or are we still stuck without it? I saw in a couple of candidates, a couple of words about dentistry,

but nobody really threw this as a major item in the campaign. But there is good news, though, that's emerging. on the universal front, on the global front. So you'd be happy to know that, and this happened when I had the privilege to serve as president of the IADR, when our CEO, Christopher Fox, worked very closely with the FDA, the World Health Organization and the UN to come up with the universal health coverage that included oral health. And so far, 18 countries have bought into this, and I expect good things to come. forth. And of course the U.S. is not involved currently, but the hope is that we could influence our public policy makers into believing that oral health is an indicator of systemic health. And systemic health, in turn, informs oral health. That bidirectional connection cannot be ignored anymore in our society. I can't say that anymore strongly. Because there are people, the disparities where you don't have

the burden of disease equally shared or distributed across society has become an increasingly bigger burden to bear. We know all about our health insurance. One last quick question for you, Mark. I read the ingredients of my toothpaste and it was mostly sand. Is that correct? Yeah, there's some soap, some sand and some filler particles. Yes, they use sand or silicate-like materials as the abrasive.

They have to be carefully crafted so that they don't aggressively wear the tooth. They have to be the correct size to manage that. But that's one of the main stain removers. Okay. We're going to leave it. We have so many questions on asking dentists, Dr. Mark Wolf, Dean of School of Dental Health, University of Pennsylvania. Dr. Rina DeSouza, Professor of Dentistry, University of Utah, and past president of IADR. Thank you for taking time and answering so many questions for us.

Thank you for having us. You're welcome. Charles Berkowitz is our director. producers are Alexa Lim, Christy Taylor, and Katie Feather. We are welcoming to our staff this week, Nigelort, our new chief content officer. Welcome to the show. We have technical and engineering help today from Rich Kim, Kevin Wolf, and Lisa Goslin, B.J. Leidem and composed our theme music.

Our Science Friday Vox Pop app, you heard them on the show today. We'll be continuing our degrees of change series next week with a discussion on sustainable building materials. We want to know from you, would you live in a city in town? made of wood if it meant reducing your carbon footprint. Download our Science Friday Vox Pop app and answer that question, would you live in a city made entirely of wood if it meant reducing your carbon footprint? Because there are now ways of making buildings out of wood, totally out of wood. We're going to talk about it on our Degrees of Change Series next week.

So please download the Voxpop app wherever you get your apps. I'm Ira Flato in New York.