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Dental Myths with Dr. David Murchison

07/16/20 David F. Murchison, DDS, MMS, The University of Texas at Dallas|Texas A&M School of Dentistry;

Season 2 | Episode 6




>> Joe: Hello again, and welcome to the Merck Manuals Medical Myths podcast, where we set the record straight on today’s most talked about medical topics and questions. I’m your host, Joe McIntyre, and, on this episode, we welcome Dr. David Murchison. Dr. Murchison is a clinical professor in the department of biological sciences at the University of Texas at Dallas. But, we have him on the podcast today to talk about his expertise in dentistry. He’s been a practicing dentist for more than forty years, and also spent more than thirty years in the Air Force doing comprehensive dentistry and a lot of dental education, as he says. He’s also a professor at the Texas A&M College of Dentistry in the Department of Orthodontics and the Department of Comprehensive Dentistry. Dr. Murchison, thanks for coming on the show.

>> Dr. Murchison: Thank you, Joe. Looking forward to it.

>> Joe: Now, many of us, or all of us ideally, should have some experience in visiting a dentist, sometime in our lives or for one reason or another. But, as you told me before we started recording, Dr. Murchison, we shouldn’t just see our dentist only when our teeth hurt or only when they’re bothering us. Can you explain why that is and how often we should be seeing our dentist?

>> Dr. Murchison: Well, Joe, dentistry has really prided itself on being a profession that really practices prevention. And, so, in order to prevent, you need to go in even when your teeth aren’t hurting. It allows for a clinical examination, first of all, because we’re not only looking at cavities in the teeth or gum disease, as we’ll speak about a little bit later, but any growths or tumors or unusual findings that we can find, and, again, prevention works best when you find things early. And, so, a preventive practice in dentistry is the best way to go, and, so, if you’ve waited until the teeth start to hurt, that usually means that it’s progressed to the point that some intervention is going to be necessary, whereas, especially with gum disease and gingivitis, just a little bit of hygiene tweaking, a little bit of better cleansing of the oral cavity, will certainly help and will reverse gingivitis, and in some cases these days, even reverse very small, what we term small enamel white legions, which is just a little bit of demineralization, and so you can actually prevent cavities by the application of some topical fluoride or some fluoride varnishes or very, very small dental restorations before they get large and actually cause the teeth to hurt.

>> Joe: Now, you mentioned gum disease there. I think this is something we’ve seen or heard of for a long time. Is gum disease something that’s rare, not something necessary that people need to worry about, or is it more common than people think?

>> Dr. Murchison: Much more common than people think, and gum disease actually, in most of the Western world and, really, probably, across boundaries, is, by far, the leading cause of tooth loss after the age of late-twenties, mid-thirties or so, and it has to do with the loss of bone that accompanies periodontal disease, periodontitis, which is an inflammatory disease, and, so, gum disease is not rare. In fact, it’s a very, very common occurrence, and, as I said before, as we age, it becomes the most common cause for the loss of teeth.

>> Joe: Now, I have seen some fodder on line that says gum disease may not just be a concern only for your mouth. Is that true?

>> Dr. Murchison: That’s very true. There’s been a link between, actually, gum disease and some cardiovascular problems because it’s a disease that’s set up with inflammatory aspects. And, so, inflammatory aspects from cytokines and other kind of localized that can become systemic effects. It can actually set up as a potential for cardiovascular problems. The second thing is it’s exacerbated by specific systemic problems, and, so, if somebody has a compromised immune system by, say, something like diabetes, leukemia, it advances the progression of the periodontal disease or the periodontitis or the gum disease. And, so, all of these things need to be taken into account, and that’s why your dentist takes a very thorough medical history as well as doing a clinical evaluation when you go in for your annual examinations.

>> Joe: So, one myth that we’ve also seen a lot online, and, I’m sure, many of us have heard some time or another when we were kids, is that chewing sugar-free gum can be either a substitute for flossing or, at worst case scenario, a substitute for brushing your teeth. I’m assuming that’s not the case, but can you explain why?

>> Dr. Murchison: That’s certainly not. Now, sugar-free gum is certainly preferable to sugared gums because it doesn’t allow the oral bacteria to feed on the sugars, and they can be glucose or sucrose or all kinds of the sugars that break down to cause acids that actually are the cause of tooth decay. Sugar-free gum is not a substitute for flossing because it doesn’t reach those especially hard-to-reach areas which are between where the teeth meet each other, or what are known as dental contacts, and that’s where food debris and plague tends to collect, and, so, the flossing is able to go in there, remove those bacterial colonies which are dental plague, and the flossing can get in there where gum cannot get in between the teeth.

>> Joe: Now, along that same vein, are diet sodas technically better for your teeth because they don’t have sugar in them?

>> Dr. Murchison: They are, but, again, everything in moderation. Diet sodas, because they have saccharin or sucralose or other different kinds of artificial sweeteners in them, as opposed to sugars, they don’t feed the bacteria. But, the problem is, they’re carbonated and they’re acidic, and, so, it’s the acids that tend to work as well, and, so, we see a lot of people, when I was in the Air Force, we had a lot of people that had jobs where they either had to listen in for a long time or they were monitoring things, and they sat there with a carbonated beverage, a soda, a cola, and they were sipping on those all day, and it has to do with the acids working on those teeth all day long. And, it’s the same thing if you have sugar in your coffee, and you’re sipping on the coffee all day long, and, so, it’s an exposure duration, and your saliva just can’t buffer it for that long, and so those people tend to have a lot of dental cavities because they have acids working on the teeth all day.

>> Joe: So, it’s not only sugar that’s the cause of teeth decay, but it’s acids, carbonation and sugar that combine to cause this issue?

>> Dr. Murchison: Correct, and, again, especially for people, let’s say, a medically-comprised person that has had some kind of head and neck cancer, that has gone through radiation, and the radiation is diminished or completely taken away their saliva flow. Those people are at high risk for dental cavities. And, it’s because there’s no buffering effect that’s left in the saliva. The saliva also contains some semblance of fluorides, and, so, again, saliva buffers that, but, if you’re continually challenging that with a very low-PH, carbonated beverage, a sugar-contained beverage, as well, that forms the acids from the bacteria, you’re going to overcome the protective aspects of the saliva and the fluoride that you use in your toothpaste and start to have those demineralized areas that form cavities.

>> Joe: Whether you’re a parent or a seasoned professional, a medical student or a caregiver, the Merck Manuals has the right medical information in the best format, and it’s always free, easy to access, and readily available for you.

>> Joe: Let’s talk a little bit about how we can prevent some of those cavities. One main key aspect of that, I’m sure, is brushing your teeth. Now, when it comes to brushing your teeth, does it matter what time of time you do brush your teeth?

>> Dr. Murchison: Every dentist, I think, will recommend brushing after meals, and that helps to remove food debris as well as break up the bacterial colonies, the plague that’s in your teeth, but, certainly, in the morning, before or after breakfast, depending on what you prefer, and then right before you go to bed at night. At least those two times a day, twice a day brushing, will break up that dental plague that we were talking about as the bacterial colonies that harbor those bacteria that can cause both the gum problems, the periodontitis or the gingivitis, as well as the dental cavities, the dental caries there. So, by breaking up those cavities, you’re able to do that.

>> Joe: Now, I’ve always been told growing up that I should have a soft-bristled toothbrush, but you would think that having hard bristles may be more likely to remove some of that plague and debris that’s in your teeth. Is that not actually the case?

>> Dr. Murchison: No, that’s exactly opposite. The hard bristles have been shown to really cause a lot more damage, and the soft bristles, two aspects: one, they’re not as abrasive when you’re using them with the toothpaste, and that’s what you’re doing, is the bristles themselves are taking the abrasive portions along with the sudsing portion, which is a sodium lauryl sulfate, it’s kind of a detergent in our mouth, but, in terms of actually the toothbrush bristles themselves, the soft bristles get up under the gum tissue and remove the plague better. The hard bristles tend to be more abrasive, and they don’t splay, or move in under the gum tissue as well. They can also cause damage to the gums, so we don’t want to do that. We don’t want to cause any recession, which is an actual moving of the gum tissue away because of either a habit, a tooth brush habit that’s too hard, or a fingernail habit or somebody has a bobby pin or something like that that they use, and, so, there are a lot of pernicious habits that hurt as well. But, hard bristles are not good. Soft bristles are good, and especially for children.

>> Joe: Now, you mentioned brushing hard. Is there a recommended pressure that someone should use when brushing their teeth to avoid brushing too hard and causing some of that recession that you mentioned?

>> Dr. Murchison: Joe, what you really don’t want to do is just a back and forth motion. It’s more of a rotary, or kind of a roundabout motion, at about a forty-five degree angle toward the gum tissue, and that allows for those bristles to move up into what’s known as the sulcus, the gingival sulcus, which is the little space between the gum and its attachment to the tooth there. And, so, by doing kind of a back and forth motion as opposed to a tremendous amount of bushing hard in a straight force, by using that rotational motion, the circular type of motion, you’re able to remove a lot more of the plague and you don’t cause the same kind of problems with the enamel.

>> Joe: Now, let’s switch over to something that people look up online, whether it’s in the Merck Manuals or just simple searches online all the time, this idea of how to make their teeth whiter. Everybody wants to make their teeth whiter. We’ve seen remedies such as lemon juice on your teeth, charcoal, coconut oil. Are any of these quote-unquote natural remedies helpful for whitening your teeth, or are they quite exactly the opposite and actually damage your teeth?

>> Dr. Murchison: Lemon juice specifically, and we actually see a lot of that down in Texas. There are cultures that tend to actually suck on lemons, and you get a lot of acidic erosion of the enamel of the tooth. Enamel is made of calcium and phosphates, a material called hydroxyapatite. And, the problem is, when you have a very acidic material like citric acid that comes from lemon juice or oranges and things like that, it actually erodes as an erosive agent for the enamel of the teeth, and we see a lot of the enamel loss. You mention charcoal. That has not been shown as being as efficient in removing the plague of the teeth, and, secondly, it doesn’t have the addition of fluoride, which is really, really important from a preventive standpoint. The last thing you mentioned, coconut oil is used again in other cultures, specifically known as a pulling technique, where you place coconut oil in your mouth and then swish and try to move it between the teeth there to try and help remove the dental plague. The problem is most of that requires ten to fifteen minutes of swishing your mouth. Well, I’ve had children, now I have grandchildren. Trying to get them to brush their teeth for five seconds, much less ten or fifteen minutes of this pulling, it’s very, very difficult. So, I can tell you the American Dental Association has no research that shows that there is a preventive aspect or a better aspect from the use of coconut oil alone, and, certainly, as an adjunct, they haven’t shown that it’s detrimental, but brushing and flossing, twice a day, with fluoridated toothpaste is the recommendation from the American Dental Association.

>> Joe: Is it true that when your teeth are whiter, they’re healthier?

>> Dr. Murchison: They’re not healthier, Joe, but, what they have done is removed organic stains. So these are the stains that come from coffee, wine, different kinds of fruits and vegetables, beets and things like that. And, so, the hydrogen peroxide actually removes those stains. It’s a transient kind of thing. It’s temporary. It lasts for a little while, and, certainly, there are some techniques, also, if you go to a dentist and they do an in-office bleaching, some of the dehydration that happens to the teeth will make them appear brighter as well. But, these are relatively safe, again, moderation is the key. And, so, if you bleach, either a home bleaching or an office bleaching regimen, that’s followed in the recommendation from the manufacturers’ materials, you can whiten those teeth. But, again, it’s a transient kind of thing. And, to keep that same whiteness, you’re going to have to either change your diet, away from a lot of different things, or get this done on a periodic basis.

>> Joe: Now, we’ve talked about the importance, obviously, of brushing your teeth. Can you get a little into flossing? Why it’s valuable, why it’s important and how it helps us remove some of that plague that brushing may miss?

>> Dr. Murchison: Flossing gets between the teeth, and it gets under the gum tissue, and, when done correctly, it breaks up the bacterial plague, and, so they don’t have the chance to colonize down there. And, for cavities, by breaking up the bacteria, they haven’t had time to demineralize the enamel of the tooth. And, so, again, they have to take in sugars, take in different starches and things to break them down into acids that cause the dental cavities. And, so, the floss just breaks them up and then allows, again, used in conjunction with brushing, the removal of that dental plague. And, so, by using flossing, by having the dentist go down and remove some of the calculus or the tartar, which is the harder deposits of the teeth, you’ve removed some of the nooks and crannies also that tend to form down there. So, by preventing that calculus or the tartar, the floss, again, is removing the plague so it doesn’t harden to form an area, again, that then those anaerobic bacteria can form underneath to actually cause the progression from gingivitis to periodontitis or the gum disease.

>> Joe: We’ve seen this a lot online. I’m sure it’s not necessarily true, but I want it to come from your mouth. Does flossing create spaces between your teeth?

>> Dr. Murchison: Flossing does not create the spaces of the teeth. What usually happens is we get drifting of the teeth, and this is especially prevalent in patients that have severe periodontal disease. And, they lose bone support, and the teeth start to move and, specifically, in ways that the mouth tends to function. And, so, as you move your lower jaw forward or a protrusive kind of movement, it can actually work on those upper front teeth, and you start to form some spaces in there. So, flossing is not the cause of that. It’s the loss of bone.

>> Joe: Now, it can be easy when someone is flossing to see some blood, maybe in their spit when they’re cleaning out their mouths. Is that a reason to stop flossing, or, if you’re brushing your teeth and you see blood, to stop brushing?

>> Dr. Murchison: The blood is showing that there is an inflammatory process going on, and, so, the body reacts to inflammation in a couple of different ways. It sends more blood supply there to send some of the kind of white blood cells and lymphocytes and things that tend to fight inflammation, and, so, first of all, you start to get a redder looking area, and that’s why gingivitis tends to have some red gums. You tend to have edema, or a swelling, in that area. And, so, the gums tends to be swollen as well. And, finally, if left long enough, you can actually get little abscesses in there, and, so you can actually get some purulent, or some puss, coming out of those areas, and that, again, is usually an indication that periodontal disease has started with the loss of bone associated with that as well. If it’s kept in gingivitis, again, so if it’s bleeding, that shows you need to spend a little more time not brushing harder but a little more thorough to remove the bacteria, and you’ll see that, with continued flossing in that area, and continued brushing, taking a little bit more time, and, if necessary, having the teeth cleaned to remove any of the tartar or the calculus in that area, you’ll see the bleeding finally reduce and then, hopefully, go away.

>> Joe: Now, speaking from personal experience, a few years ago, I switched to sensitive toothpaste, sensitive teeth toothpaste because I was dealing with some sensitivity in my teeth. Is tooth sensitivity only a result of enamel loss?

>> Dr. Murchison: Joe, actually not. It can be associated with enamel loss, but it is often associated with a little bit of gingival recession, and, so, it tends to be just as the patients are moving from, say, the late twenties to the thirties to the forties, and you’re starting to get a little bit of gingival recession to the gum tissue moving down towards the root of the tooth, and where the enamel and the cementum meet there, if you have an aggressive brushing style, if you’ve had a cavity in that area, or, more frequently, if you tend to have what are known as abfraction lesions, where you’ve formed kind of a V-shaped area where you’ve lost some of the cementum due to some motion of the tooth, some flexing of the tooth in that area, you’ve now exposed dentin. And dentin is a vital structure underneath both the enamel and the cementum, and it’s made up of little tubules. And those tubules are what causes the sensitivity because they are fluid filled, and the movement of that fluid stimulates some nerves that are down near the nerve of the tooth itself. Now, about ten percent of the population is born with a gap between the enamel and the cementum. And, so, if you happen to be one of that ten percent, as soon as you get a little bit of gingival recession when you drink some iced tea or you drink something sweet or drink something very hot, it causes that stimulation of the dentin. And, so, there are a couple of different ways to handle that. You can put a restoration on that; that’s invasive. You can apply a desensitizing agent which works for a little while. Or you can use, as you just spoke about, a desensitizing toothpaste, and most of those contain potassium nitrate within a toothpaste or some types of gels. Some bleaching agents even have some potassium nitrates to try and reduce tooth sensitivity. But, by using that, it actually acts at the source of the nerve near that tooth, but, the thing is, it takes a certain amount and a certain amount of time of that sensitivity toothpaste. And, so, if you go to the dentist, and the recommend that, and you ask for that because of tooth sensitivity, they’ll usually say give it four to six weeks because it takes time for the actual activity of the potassium nitrate to work on the nerves themselves.

>> Joe: Alright, as we kind of wrap up here, Dr. Murchison, I want to talk about wisdom teeth. I had my wisdom teeth taken out probably around four years ago, relatively painless procedure and no issues afterwards. Can you explain to our listeners why people get their wisdom teeth out and what maybe some of those reasons would be?

>> Dr. Murchison: It’s an individual call for each patient. So, you’ll be interested to know, Joe, that wisdom teeth tend to be the teeth that tend to be missing at birth for quite a few people. So, some people never have any wisdom teeth, or they’re missing one or two or sometimes all four. But, they’re the most commonly missing teeth, and, so wisdom teeth aren’t required for you to be wise. I don’t even know where that moniker came from. But, wisdom teeth are third molars, basically, and, actually, you’ll find that sometimes wisdom teeth don’t have to be taken out. Sometimes, patients have had orthodontics in the past, and they’ve lost bicuspids as the orthodontist has moved the teeth around, and they’ll have room in their mouth for those wisdom tooth. Some people have large enough jaws that the wisdom teeth can come in and not be covered by a portion of the gum tissue back there or cause any kind of chronic inflammatory process back there. Unfortunately, for many people, the wisdom teeth come in at an angle, and, so, they’re never going to erupt, and so they cause, at that point in time, a real potential problem by potentially being trouble to the tooth in front of them, the second molars which we really need for chewing efficiency, and, so, if the dentist or the oral surgeon that is evaluating the patient for removal of the wisdom teeth decides that the angle of these teeth, their position, is going to become a problem, or if the tooth is never going to erupt and there’ll be a continuous inflammatory process and, potentially, and infected process back there because bacteria loves to hide under these little flaps of tissue that cover some of the lower wisdom teeth back there. And the problem is the upper wisdom teeth can sometimes bite on that little flap, and it’s called pericoronitis, which is peri-, around the crown, -corona-, of the wisdom tooth down on the bottom, and, so, there is a constant kind of inflammatory process down there, and, so, again, you don’t want infection in the mouth, and that’s what can happen over time. So, if you maintain wisdom teeth in your mouth, you need to be evaluated over time with dental X-rays that show that tooth to make sure that nothing is being stirred up by having that tooth remain within the bone over time.

>> Joe: Now, I’m sure we’ve only just touched the tip of the iceberg when it comes to dental questions or dental myths. We only have about a half hour here. So, if someone has a question about a dental issue, a dental question, a myth that they’ve heard that they want clarified, Dr. Murchison, where should they go for those answers?

>> Dr. Murchison: Well, preferably, Joe, they’re asking their dentist as they go see him or her on a six-month or an annual basis to be evaluated, and, so, again, the dentist is looking at your specific situation, and, so, they’ll be able to give you your specific answers. But, if they’re going online, certainly the Merck Manuals have some great dental authors that write the chapters on some of the things that we’ve talked about today. They talk about dental emergencies. They talk about periodontal disease. They talk about pediatric dentistry and eruption of teeth and things like that. So, there’s a plethora of knowledge out there on the Merck Manuals at The American Dental Association provides a lot of free information, and a lot of the dental manufacturers. So, you go to, again, I have no beholding to any of these manufacturers, but if you go to any of the toothpaste companies that are out there that provide oral hygiene, you can get some information about the ingredients in there for whitening your teeth or fresh breath, for sensitivity and things like that. But, the American Dental Association will provide a lot of information on specific topics, and they use an evidence-based science approach as well, and, so a lot of the, quote, myths that are out there, whether it’s a material that’s used in your mouth, whether it’s some type of potential allergen that’s out there, the American Dental Association is a great place to see that.

>> Joe: Well, Dr. Murchison, thank you again so much for joining us. I think this has been a super helpful conversation. I know I’ve learned a lot about dental health and how to make sure my teeth are protected and as healthy as possible.

>> Dr. Murchison: Joe, it’s been my pleasure to talk to you, and I appreciate you asking me on today.

>> Joe: And, I’ll leave our listeners with something as we say every time we do at the Merck Manuals

>> Dr. Murchison: Medical, and dental, knowledge is power. Pass it on.

>> Joe: Thank you so much.