Is Dog’s Mouth Cleaner Than a Human’s?

I learned that in school, in a sex therapy course, and my dental hygienist confirmed it again, weeks ago. Who cares? Clients sometimes have concerns about oral sex because they are usually reluctant to put their mouths (which they consider clean) on another person’s genitals (which they consider dirty.) Sex Therapist thought that what most people should be concerned about is having a dirty mouth on their clean genitals.

I wanted to research the question in more depth myself, and the results led me to some interesting findings. Let’s go to the dogs, first:

A Dog Eat Dog World
There are very few diseases that can be transferred from dogs to humans. It is easier to spread germs within a species than between species. Dogs spread more germs to other dogs than they do to humans. That is, unless you eat the dog. Eating a diseased animal infected with particular microorganisms that species, such as mad cow disease and a related virus in wild deer and domestic sheep can be transmitted to humans. There are also other exceptions that don’t require injecting, such as rabies and roundworm. However, in North America, the handful of serious cases of roundworm or rabies passed each year from dog to human pales in contrast to the millions of cases of AIDS, hepatitis, herpes and even the common cold that our species exchanges year in and year out. Dogs, in contrast, don't get colds. "One particular organism that you don't normally find in people's mouths, and is associated with dog bites, is an organism called pasterella multocida," George Marchin, an associate professor of microbiology adds. "It is a more serious organism in terms of superficial infections” but with a normal, healthy animal, the risks of becoming ill are fairly minimal. (1)

So, therefore, a dog’s mouth is dirtier (more infectious) to another dog than it is to a human. For the most part, humans are immune to most dog germs. Fido is in no great danger if the mailman bites him, either.

You Dirty Dog
It also should come as no surprise that the bacteria in a dog’s mouth
has a lot to do with what it’s (change to "it has") been eating lately.
A healthy dog chowing on kibbles has, by and large, fewer kinds of bacteria and less
of them than your average human. According to my dental hygienist, your pet has about 200. But it is difficult to get exact estimates, partly because if Rover’s been chewing on a dead pigeon, his oral germs will skyrocket.

Canine behaviorist Ann Jackson, while studying microbiology, collected
smears from the mouths of several species of mammal including dogs and
humans. While the swab from the dog's mouth took three days to grow a
bacterial culture, the swab from the human's mouth sprouted a growth
within only 24 hours. (2)

Dogs rarely get cavities, but they do get gum disease. Paradoxically, if a dog’s overall health is good, and particularly if his gums are fine, his good and bad bacteria have an ongoing battle, each keeping the other in line. A kind of doggy Listerine TM If he is fed a dry kibble, rather than a wet diet, gum disease is delayed as well. Humans, however, are at a disadvantage of not only eating moist, wet food, they also use toothpaste and mouthwash, most of which kill off good bacteria, leaving more of the bad stuff to grow and multiply. (3) More on that later.


How the Story Started
The story about a dog’s mouth being cleaner than a human’s mouth actually got started when looking at statistics into Closed Fist Injuries (punch someone in the mouth, hit the teeth, and your hand gets infected). There were more cases of infection caused by Closed Fist Injuries, than through dog bites, in that statistical analysis. However, it turned out that other issues accounted for that fact, such as that the person with the infected hand waits before seeking treatment, and the mouth of the person he or she punches might not represent the “average” mouth. In reality, about 10% of dog AND human bites get infected. (6)

Wash Your Mouth Out
That’s what my mother threatened me, as a child if I kept up my dirty talk …with soap. The threat didn’t work, and neither would the soap be effective if Mom was interested in cleaning up the bacteria and viruses in my mouth. Depending on who you read, humans have anywhere from 700-10,000 bacteria in their mouths, along with oral microorganisms that can include fungal, protozoal, and viral species. The bacteria include hundreds of types of organisms of which only "22 predominant ones have been identified."(4) Part of the problem in getting an exact count is the trickiness of bacteria itself.
“Until quite recently we were limited by which bacteria we could grow as a culture in the laboratory. We know now that not only do cultured bacteria behave differently to those living ‘in the wild’ but there are very many species which cannot be cultured at all. One important discovery is that bacteria living in or on the body can be up to five hundred times more resistant to anti-microbial agents than a pure strain of the bacteria in a laboratory flask.”

...says microbiologist Dr Stuart Dashper. (2) He argues that there are more than six hundred species of bacteria that inhabit and interact in the human mouth. The behavior of mouth bacteria is influenced and altered by the behavior of the host human.

The oral cavity (the mouth) is actually the main entrance for two systems: the gastrointestinal and the respiratory system. Our breath or respiratory system can be the carrier of many other potentially harmful germs. Dentists practice “universal precautions” which are mainly barrier techniques such as gloves, masks, and glasses worn while seeing patients, and this is more for the breath than the blood. According to Dr. Stephen Geoghegan, hepatitis is more virulent, and therefore more of a concern to dentists, than AIDS.

It turns out that it’s easier to kill off “good” bacteria with our personal hygiene habits, but don’t toss the toothbrush away. While there is no mouthwash or floss that will kill off the bacteria that cause infectious diseases, our oral hygiene regimens reduce the quantity of bacteria in our mouths. Brushing our teeth is like weeding a garden: we control the growth of the bacteria so that they do not become so numerous that they begin to damage the crops (our teeth.) The new antimicrobial agent Kappacin is particularly effective against one of the microbes most responsible for tooth decay, Streptococcus mutans. Kappacin is made from whey, a by-product of cheese. (2)

The Mouth: Early Warning System
If I had any doubt about the value of good dental care, I lost it after researching this topic. Dentists are often the first professional to spot trouble in the mouth, and the mouth is often the first sign of trouble in other parts of the body. Mouth lesions and other oral conditions may be the first sign of HIV infection, and are used to determine the stage of infection and to follow its progression to AIDS. Studies of post-menopausal women suggest that bone loss in the lower jaw may precede the skeletal bone loss seen in osteoporosis.

In addition, the mouth can also be the source of infection. We now know that the same millions of microorganisms that float around in the mouth, causing oral infection, such as tooth decay or gum disease, can enter into the bloodstream if the bacteria gets out of control. It is a give-and-take system, where a healthy body helps maintain oral health, and oral health maintains a healthy body. For example, while we know that plaque causes gingivitis, not everyone with plaque build-up gets gingivitis. Usually an underlying illness or taking medication is necessary to render one’s immune system susceptible. Therefore, it is the disease process itself, such as diabetes, Addison disease, HIV, and other immune system diseases that create the lack of ability to fight bacteria invading the gums. Then, gum bacteria infect the rest of the body. Invaded by this bacteria in this weakened immune system, the germs can stick to the lining of diseased heart valves causing diseases such as infective endocarditis. Patients with a history of heart defects are at risk for endocarditis. Some dentists will treat particular patients ahead of time with antibiotics, just in case.

The balance of microorganisms maintains health in a healthy body. With a healthy immune system, an influx of oral bacteria, through dental work or even brushing and flossing, is harmless. Just more “germs” our body fights off every day. A mouth damaged by treating other diseases, such is chemotherapy, (that can damage mouth tissue), or medications (that reduce saliva flow), throw off this balance. Lifestyle choices also impacts. Smoking impacts saliva, and smokers are more likely to have calculus (hardened tartar) on their teeth, and the use of Crack cocaine opens the mouth to sores.

Saliva is Diagnostic
Saliva is also an excellent tool for detecting and measuring everything from hormones and environmental toxins to antibodies against viruses such as HIV, hepatitis A & B, and bacteria that causes peptic ulcers. There is soon to be released a test for Alzheimer’s disease using saliva alone as the “testing” agent.

Saliva can also be a “heads up” for women regarding other bodily fluids as well. Any substance that can dry up the mouth, such as cold remedies, and even red wine, is also likely to affect the volume of vaginal lubrication.

Bad Breath
There is also a lot to be learned about bad breath. Not everyone has it, because not everyone has the six bacteria living on the tongue that causes it. The ‘fresh breath’ folks apparently have yet a different group of bacteria than those with halitosis, according to Bruce Paster, (6), a researcher at the Forsyth Institute in Boston and an associate professor at the Harvard School of Dental Medicine. There is some overlap between the two groups but organisms present in high numbers in fresh mouths rarely appear in mouths with bad breath and vice versa.
Unfortunately, as mentioned above, getting rid of bad breath isn’t as simple as using the right mouth wash. Apparently, some mouths are just more inviting to some bacteria, and the ‘good’ bacteria won’t stay, even if they are put there intentionally. We know. People have tried.

Two of these oral pioneers are Sigmund Socransky and Jeff Hillman. Socransky at the Forsyth has tried to displace bad bacteria by swishing billions of good bacteria around his mouth and by packing them into his teeth. It didn’t work.

Jeff Hillman at the University of Florida is attempting to prevent or reduce cavities by pasting genetically engineered bacteria on teeth. Securely anchored on plaque, well-known microbes such as Streptococcus mutans produce an acid that erodes the hard enamel and starts the process of decay. If “anti-bacteria bacteria” can successfully colonize both tongues and teeth, people could enjoy fewer cavities as well as fresh breath. He’s still working on it.

Scrapping for Fresher Breath
Bad breath bacteria have Velcro-like projections on their surfaces that adhere to so-called receptors on your tongue. Normally, good bacteria build a coating that prevents bad guys from forming colonies. When this process becomes interrupted, the latter get a hold. "We don't have a good handle on how this happens," Paster admits.

The malodorous residents break down proteins from food, saliva, and other compounds in your mouth, and this activity releases sulfur-containing compounds, which cause pungent breath.
The first step in evicting the smelly organisms involves use of a tongue scraper, often labeled as "tongue debriders." Or you can just use a toothbrush on your tongue as you brush after every meal. If the tongue plaque is particularly tenacious, anti-microbial mouthwashes often do the job. But there’s a catch: "We are presently looking into a variety of such rinses to determine which ones work best on the bacteria we have identified," Paster notes. The trick is to develop microbial rinses that would suppress the activities of one and support the activities of the others.

Efforts are underway to “gene-map” the mouth using microchips which can identify many genes at once, and compare the active genes of people with sweet tongues to those with smelly mouths.

Lifecycle Changes and Tongue Piercing
Hormonal fluctuations in the body, such as pregnancy, puberty, and menopause, also leave the gums vulnerable to bacterial infection. Teens are vulnerable to oral problems, and, according to my hygienist, appear to have, as a group, less than ideal dental hygiene habits. Add tongue and lip piercing, and the stage is set for problems. Dentists warn that, “in addition to periodontal diseases tongue piercing may cause other complications such as tongue swelling, difficulties with chewing, swallowing and speech, increase of saliva flow, localized tissue overgrowth and metal hypersensitivity.” Even fatal infection, such as Ludwig's angina or endocarditis, according to a report in the May/June 2004 issue of General Dentistry, the Academy of General Dentistry's (AGD) clinical, peer-reviewed journal. (7)Ludwig's angina, a bacterial infection of the floor of the mouth, occurs after a tooth infection, mouth injury, oral surgery and oral piercings.

After getting an oral piercing, the mouth has an open wound which allows bacteria to travel through the bloodstream. Bacteria then cause the floor of the mouth to rapidly swell, which can block the airway or prevent the swallowing of saliva. At the dentist's office, a medical history is taken which helps the dentist determine who is at risk and those patients are given antibiotics prior to certain dental procedures in order to avoid this potentially fatal problem. Most body piercers are unlicensed and are not members of the medical profession. Because of this, health histories are not recorded or reviewed, emergency medical kits are not available, antibiotics are not prescribed and postoperative care is not available." The teenagers might be told to expect some “swelling,” but without follow-up care, how do they know what is “abnormal” swelling? The equipment may also not be thoroughly sterilized, causing other infections.

“That’s so cool! Can I touch it?” Touching piercings can also spread infections by their own or other’s fingers.

“I’d Like to Get to Know You. Can I Talk to Your Dentist?”
Maybe we would all benefit from paying a bit more attention to our own mouths and those we share our mouths with. If I walk away with any lesson from this study, it is that oral health should not be separated, or valued any less than other types of bodily health. If the eyes are the window to the soul, the mouth is the gateway to the entire body.

Pay attention to bleeding gums. Ask about the overall health of your mouth the next time you visit your dentist, and increase your visits to your hygienist to 3 or even 4 times a year, if your own regiment of clean isn’t doing it. I was amazed to find that I could get a computer print-out of the “gaps” in my gums, front and back and could get updated reports on just how well I’m closing them (and the “pockets of bacteria” they contain.) Each tooth in the printout was marked by numbers, with 3 mm being “normal” and my worst being 5 mm. (But not anymore!) I put it inside my medicine chest to remind myself which gum lines to focus on in particular. I also got a new automatic toothbrush and microbial rinse to help “clean up” the gaps each time I brush. I also use the tongue scraper regularly, especially after researching this blog entry.

Back to the Past
I collect stories, and the best ones are the ones that seem the most unlikely, but turn out to have truth in them. I’ll end by sharing three: Growing up, my mother was taught to spit out her mouth in the toilet while brushing. I considered the habit disgusting, and she, herself, abandoned it after she got married. However, my hygienist confirmed the wisdom of the practice saying “The bowls you used to spit into at the dentist’s office is now a thing of the past. That bowl was a cesspool of bacteria. Get used to this.” What “this” was appeared to be a straw that sucked out saliva. At least that’s what I thought it was suppose to do, and I’d choke on it each time I closed my mouth around it. “No, put it just inside your lips and spit into it.” It works! Have I started spitting into the toilet? Not yet.

My second oral tale is about the Inuit boy, who put his tongue on metal, and it froze there. The fast thinking father, pulled out his penis and urinated on it, releasing the tongue with his warm stream. The father’s penis didn’t touch the boy’s tongue, saving the father’s genital from the child’s oral bacteria. (That last part I just added.)

My last story is equally compelling, and I’ll talk about it and about oral sex and sexually transmitted infections (STI’s) in the next blog entry: In a study of HIV infection rates and oral sex, it was assumed that the most likely HIV infections would occur with receptive fellatio with ejaculation [8]. However, what they found was an elevated rate of HIV among men with genital piercings: In three of the five cases in which they judged oral transmission to be likely, insertive fellatio by a man with a penile piercing was the highest risk implicated. The piercings may act as a skin “breach” even when the skin has apparently healed on the surface, allowing for viral entry. The presence of a metal stud or ring may well cause ongoing subclinical inflammation. Although not discussed in this study, it left me wondering if tongue piercings hold the same risk of infection.
References
1.http://www.dogstuff.info/dog_kisses_ksu.html
2.http://www.nsnews.com/issues98/w110998/mouth.html
3.http://www.sciencealert.com.au/stories/CRCA/dental.htm
4.http://www.madsci.org/posts/archives/nov98/910747365.Mi.r.html
5.http://www.news.harvard.edu/gazette/2003/02.27/01-breath.html
6.http://www.madsci.org/posts/archives/Jun2003/1057075434.Zo.r.html
7.http://www.newomen.com/displayarticle189.html