But that's not what I'm talking about this time.
I noticed that some of the people who I love most have bad breath. Sometimes, I've heard, even I have bad breath. Occasionally, despite having awesome oral hygiene, my mouth tastes kind of skanky and I could definitely believe that it wouldn't be pleasant to be in intimate conversation with me. So what is in my mouth that is nasty? Definitely not rotting food, because that is gone after I brush my teeth and has no way of magically reappearing. The taste, and smell, is worst after sleeping, during which time salivation is minimal and the natural washing action of the tongue is almost non-existent. Some people believe that nasty breath smells come from the sinuses or the stomach, but my knowledge of the plumbing of these areas suggests that I need look no further than the actual oral cavity. Genetic methods have identified over 600 species of bacteria in the mouth, most of which have not been well characterized. Some species lead to dental caries, others produce chemicals such as hydrogen sulfide or methyl mercaptan which smell nasty, while others modulate the oral environment to produce a healthy and disease resistant mouth. Dentists have identified Streptococcus mutans and Streptococcus sobrinus as being strongly associated with caries, but other patients with rampant caries did not harbor those bacteria and instead had multiple other identifiable bacterial types which may have been causal in their oral ill health. Still other bacteria may produce nasty smells but have no particular association with tooth or mouth problems. Some bacteria cleave sugars attached to proteins making it possible for other bacteria to digest those proteins, and thus produce smelly chemicals.
The human microbiome project was launched in 2008 to identify the bacteria which colonize us, including those of the mouth, gut, skin, vagina, lung and sinuses. This may well contribute to more effective therapeutics for the chronic diseases of these organs which are at present poorly treated by the heavy hitting pharmacological agents we are so good at developing. Antibiotics, so important in treating serious infection, can also kill bacteria indiscriminately leading to the growth of resistant organisms. They can also cause side effects on the kidneys, liver and bone marrow as well as serious allergic reactions. Immune modulating medications reduce our resistance to infection and cost ridiculous amounts of money. All of these are used to treat conditions of organs which have rich bacterial communities, without addressing the issue of what makes those communities healthy. Characterizing the flora of the mouth in health and disease could lead to novel therapies that might reduce gum disease and cavities as well as preventing things like strep throat and canker sores. Also bad breath.
Fecal transplant, that is introducing the bowel contents of a healthy person into a person with intestinal disease (limited right now to treatment of chronic Clostridium difficile infection) has proven to be powerful, simple and curative for people with bacterial diarrhea in whom antibiotics fail.There is increased interest now in all kinds of natural probiotics, helpful bacteria that are in foods, for overall gut health, with the hope of curing non-specific gut discomfort as well as intolerance of various food substances such as gluten and lactose. Might there be a precedent for oral bacterial transplants? Fecal transplant is abhorrent enough to humans that we have not come close to exploring its potential applications, and I can find nowhere on the internet describing a similar process for the mouth. Why would it not be useful to take oral bacteria from a person with excellent oral health and swab it into the mouth of someone who gets cavities at the drop of a hat or someone with rotten fish breath?
Presently I can't bring myself to request a sample of mouth bacteria from a friend with awesome oral health. It sounds like a great idea, but I am not adequately motivated and also am not sure I would actually trade up. I have very few cavities and never have mouth or throat infections, so maybe the bacterial community in my mouth, despite not always smelling sweet, is doing a fine job. Still, I haven't been able to resist trying a few of the easily available treatments that I have read about for sweetening the breath. Oral health experts recommend brushing the back of the tongue, where the tastebuds grow high and the bacteria tend to congregate. After brushing and gagging, my mouth does taste better for awhile. I have used mouthwashes a bit, but probably will not do so again after thinking about the implications of carpet-bombing my oral flora with chlorhexidine and alcohol. There is absolutely no reason to believe that the random bacteria which grow up after I use chlorhexidine will be any more beneficial than the ones I have now. I have bought oral probiotics which are chewed or dissolved in the mouth and contain beneficial strep strains, such as Streptococcus salivarius, which are purported to outcompete more harmful strep species. They taste nice, but I have not been impressed with any change in what I perceive as my mouth's health. Perhaps I chose the wrong brand. I have been most impressed with an ancient remedy, recommended by Hippocrates and Galen for diverse ills and prized by sultans' wives for sweetening the breath. Mastic gum, from the Pistacia lentiscus tree in Greece, is harvested by allowing the sap to leak from the tree and dry to hard chunks on the ground. When chewed, it tastes a bit like cedar and softens into a substance much like chewing gum. I bought some on Amazon, and it arrived from Greece a couple of weeks ago. I think I like it. It makes the bacterial soft plaque that I notice on my teeth go away and my mouth tastes fresh. My teeth feel like they do after a dental cleaning, more smooth and shiny than they do normally, and the effect lasts for a day at least. A study from 2002 shows an antibacterial affect against Strep mutans. I don't swallow it, but a study over a decade ago showed it to be effective against Helicobacter pylori in the stomach which can cause ulcers and stomach cancer. It's not clear that even mastic gum is benign to the good oral bacteria, but it has sure been delightful to have shiny teeth!
Xylitol, a synthetic sugar alcohol that is common in sugarless chewing gums, has attracted quite a bit of attention as a preventative for tooth decay, and probably also for bad breath. A study that was reported in 1995 looked at 277 primarily school aged children given chewing gum flavored with sucrose, sorbitol, xylitol or a combination of xylitol and sorbitol to chew regularly. There was a slight increase in cavities with sugar sweetened gum and a significant decrease when the subjects used non-sucrose sweetened gum, especially xylitol sweetened gum. A more recent controlled trial of xylitol lozenges in adults at high risk of caries did not show significant reduction in cavities, except in the case of root caries. Xylitol use reduces bacteria that cause caries, and possibly bad breath as well, though I don't find any actual studies to that effect. My own totally unscientific opinion, based on chewing xylitol gum and sucking on the lozenges, is that there doesn't seem to be any lasting effect at all on breath taste or smell. Xylitol is also toxic to dogs, in whom it causes hypoglycemia and sometimes liver failure. It is not apparently toxic to humans, and doesn't increase blood sugar in diabetics, which is handy. It is not, however, completely calorie free, but it is so sweet that it takes very little of it to sweeten something.
Bad breath is interesting not only because it is mysterious and socially significant, but also because it is an expression of complex bacterial interactions. The mouth is a small cave, populated with an interdependent community of bacteria whose health can have pretty far reaching consequences. It will be good to see what comes of the Human Biome Project. It has such wide ranging implications for understanding the human body in health and disease. Treatments like mastic gum or dietary probiotics and even ideas like oral bacterial transplant are exciting for treatment of annoying and socially very significant conditions such as tooth decay and bad breath. They unfortunately do not have the driving force of pharmaceutical companies behind their development. Treatments that can be inexpensive and in the control of people who are not in healthcare professions have the potential to make powerful changes without associated costs. The paucity of research into this sort of thing can be traced to the fact that we do not have a very good mechanism for scientifically exploring therapies that don't make anybody money.
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