ABSTRACT
Dentistry has existed in a paradigm or understanding of bacterially caused dental diseases. Recent efforts to link periodontal disease to diabetes and cardiovascular disease have not been able to determine if bacteria are causal or casual to the relationship. This article presents evidence that inflammation caused by oxidative stress is the common link. The realization that bacteria are not the cause, but only casual to dental disease, presents both ramifications and opportunities for dentistry. The dental profession is encouraged to explore the treatment, prevention, public health and legal implications of this new paradigm.
In recent years, we have seen a trend towards a broader perspective of dentistry. Rather than viewing dental care as a specialized, oral interest which is unconnected to systemic health, much attention has been focused on the links of periodontal disease to diabetes and cardiovascular disease in particular. Causal or casual seems to be the main question, but there are many others that remain difficult to answer. At this point, one has to wonder if or when an answer will be discovered. Alternately, maybe we are looking in the wrong place for our answers.
THE PRESENT PARADIGM
A paradigm is like a map which guides us. The power of a paradigm lies in its ability to guide us to answers in uncharted territory. If we use a map of Toronto when we are in Toronto, it is an excellent tool to get us to places in the city that we have never previously been. If we try to use the same Toronto map when we are in Vancouver, it will be a very frustrating experience. Is our present dental paradigm frustrating us?
One of the most powerful paradigms in science occurred in the 1860’s when Mendeleev developed the Periodic Table which now hangs in every science classroom. By using the paradigm of his Periodic Table as a map, he predicted several elements to exist that no one had ever discovered. In his lifetime, three of them were discovered. Such was the power of his paradigm.
Louis Pasteur’s ‘germ theory’ paradigm seemed to serve dentistry and medicine well in the era of infectious diseases. Antibiotics revolutionized how the professions treated infectious diseases. Abscessed teeth and periodontal infections could be controlled. In fact, our whole system of dental care is now designed to control bacteria because they are perceived as the root cause of the problem in an infectious disease paradigm. So why don’t we develop an antibiotic toothpaste? Why does periodontal disease appear as a localized and episodic event while bacteria are more generalized and constantly present? Recent discoveries in periodontal research are now recognizing periodontal destruction as an inflammatory response of the host, rather than due to bacterial infection. It is speculating that, while bacteria are always present, they may not necessarily be the cause of the breakdown. Infectious diseases do exist, but most degenerative, lifestyle diseases like periodontal disease and tooth decay are inflammatory, not infectious. The evidence that bacteria are merely casual rather than causal leaves a huge hole in dentistry’s infectious disease paradigm.
The paradigm that inflammation is the root cause of not only periodontal disease, but dental caries, cardiovascular disease, diabetes, arthritis and many more is rapidly emerging. This will not necessarily be embraced by a profession trained in the infectious disease model. Remember the early 1500’s when the widely accepted “Flat Earth Society” tried to discredit Copernicus with his round earth and sun-centric universe theories. Today, medical doctors and dentists focusing on treating symptoms or results of bacterial damage related to their special area of expertise is the accepted norm just as a flat earth was the norm in the 1500s. Who is treating the common cause of inflammation on a preventive level? This is not meant to demean the efforts to control infectious diseases, because they do exist. It is meant to indicate that to go beyond where we are now, we need a new map. The new map will focus not on infection, but on inflammation. It will not focus on bacteria but on the body’s inadequately regulated immune response.
QUESTIONING WHERE WE ARE
The dental profession has led all others in prevention. Ideally positioned with a clientele of reasonably healthy people of all ages seeking elective care on a recurring basis gives dentistry a significant advantage. As a caution, however, a quote comes to mind with respect to this leadership potential. “Good managers climb a ladder quickly. Good leaders make sure the ladder is leaning against the right wall.” Given the evidence that is emerging, we must have serious doubts about the bacteria wall or paradigm that our ladder is leaning against and begin to understand the inflammation wall where it should be leaning.
Skin, our largest organ, is an incredible barrier and extremely specialized to serve many functions. Our bodies are like a hollow tube. Skin on the outside of the tube is quite uniform. Skin on the inside of the tube, however, is very specialized. It can be periodontal skin, the surface of the lungs, stomach lining, the intestinal wall or the colon. All of these surface areas are outside the body, but inside the tube. Food and waste products in the gut are outside the body waiting for absorption. Bacteria are all over these outside skin surfaces. They are ready and willing to penetrate and cause infections like periodontal abscesses, pneumonia, peptic ulcers and the complications of a ruptured appendix. Antibiotics in the blood stream work when bacteria have penetrated the surface, but are not necessary without surface penetration. Given the ubiquitous nature of bacteria, it is easy to see why we would draw the conclusion that bacteria are the cause of skin diseases in the periodontium, stomach lining and the lungs. But they are also present in health, so maybe they are simply casual to the situation while the real breakdown is caused by overwhelming the inflammatory response of the body itself.
Substantial research and clinical success already exists to support the inflammation paradigm. Local therapies such as placing time-release, micro-dose doxycycline (Atridox) directly into periodontal pockets is available. Systemic therapies such as low dose doxycycline (Periostat) taken twice a day for several months are also effective. Neither focus on the antibiotic qualities of doxycylcine, but on its ability to alter the host inflammatory response through regulation of matrix metalloproteinases. Neither, however, is used as a preventive measure, since they both wait until there is measurable disease parameters before being instituted.
Let’s apply the inflammation paradigm to see what is really happening. If it has the power to explain presently unanswered questions, we should be able to use it as a map to direct us to better prevention and therapies, not only locally but systemically.
The words “gingivitis” and “periodontitis” recognize that it is not the infectious bacteria but the chronic insult of their toxic by-products that are irritating the skin and causing inflammation. Trauma also violates the skin barrier and produces the same inflammatory reaction by the body. In short, bacterial toxins traumatize our skin. Less trauma is good, so cleaning your teeth and gums is the right thing to do. The goal of all dental procedures is to improve cleansability. Restoring carious lesions, scaling, pocket elimination and straightening teeth all have the same cleansability objective, which is to minimize bacterial trauma. The real war, however, is not what kind of trauma is happening on the skin surfaces, but how the host is responding from the inside.
When a trauma occurs, whatever the cause, the host response is the same. Chronic irritation or acute trauma both trigger an inflammatory response to heal it. Acute irritation is repaired by a short-lived inflammatory response, which is then shut down or controlled by
the body when it is no longer necessary. This is like a sliver in your finger or an extracted tooth. Chronic irritation on the other hand, can set up a low grade or sub-clinical response which may or may not overwhelm the body and cause breakdown. How often have we said to people that periodontal disease happens more in later years due to decreased resistance of the host rather than more aggressive bacteria?
TIME TO MOVE ON
Let’s start from the very beginning to explain the inflammation process. The basis of this could well be known as ‘Free radical theory’. A free radical is a short-lived, charged molecule which is often oxygen. To stabilize itself quickly, it must steal an electron from another molecule. In its haste, it can create substantial damage to the mitochondria, the cell wall and even the cell’s DNA if that is where it steals the electron. Since a small amount of free radicals are produced in the normal energy production in the mitochondria of the cell, known as endogenous free radicals, the body has its own defense mechanisms to control them. These are antioxidants like glutathione, catalase and superoxide dismutase which readily and harmlessly donate an electron to neutralize the free radical. They are our body’s defense against the oxidation forces of free radicals. Bacteria do not have this antioxidant defense system, so that is why the body uses controlled oxidation to effectively eliminate bacteria without harming itself. Oxidation causes an apple to turn brown, steel to rust and a body to age. Essentially, with uncontrolled oxidation, we accelerate the rusting, aging or diseasing processes unless we have adequate antioxidant defenses. Excessive exercise is an intentional way to increase energy production, but it also increases endogenous free radical production. Dietary or outside sources of antioxidants from fruits and vegetables are sometimes necessary to cope with the excess demand.1
In health, the forces of oxidation are balanced by the antioxidant defense system and there is no reason for concern or a reaction. If the oxidation forces increase, especially be adding exogenous sources of free radical oxidation, they may overwhelm the body’s antioxidant defenses. This excess of oxidation over antioxidation is known as oxidative stress which the body copes with through an inflammatory response. Matrix metalloproteinases (MMP’s) are released by the body to clean up dying tissue and the results of the inflammation war. Whether you have a sliver in your finger or plaque on your teeth, once the irritant is removed or reduced below oxidative stress levels, the inflammatory response is halted. In a chronic situation, however, it continually bombards the system. Breakdown due to oxidation occurs in the form of periodontal disease,2 dental caries, cardiovascular disease3 and explains why diabetics age faster than the normal population.4
Traditional dentistry has done an excellent job at trying to decrease the forces of oxidation, even if we were doing it for the wrong reasons. We were trained that the bacteria were causing the damage, while really they are only creating excessive exogenous oxidation and the body’s inflammatory defense system is creating all the damage to itself. Other exogenous or outside the body sources of oxidation are smoking, pollution, medications, excessive sunlight and a poor diet. The body really doesn’t distinguish what is causing the oxidation, whether it is cigarettes or plaque. Its inflammatory reaction is the same, only more widespread with smoking and more localized with plaque.
How does the inflammatory theory explain dental caries? Recent research reported by Sorsa offers compelling evidence that breakdown in the dentin layer of the tooth, similar to periodontal tissues, is due to the body’s own MMP’s.5 Previously it was thought the dentin collagen breakdown was done by the bacteria’s MMP’s. Now evidence is leaning more to the concept of MMP’s within the tooth’s own odontoblasts causing the degradation of the dentin organic matrix when stimulated by acid. Essentially, enamel is serving as a very specialized skin over the crown of the tooth. Once it is violated by acid, bacterial or otherwise, then oxidative stress and an inflammatory response to the acid environment occurs in the dentin. This is what we recognize as caries. In short, it is not the bacteria but the acid that is critical, which is why you should be alert for the use of probiotics in dentistry to reduce the acid producing potential of Strep mutans.6,7 It is also why cheese has been touted as a good thing to eat after meals. While studies often give several reasons why cheese might be effective in reducing caries potential, it would seem that buffering the ph might be one of the more significant factors.8 While there are not a lot of studies to demonstrate it, there are some that measure the same rate of decay in sugar-free soda pop drinkers as sugar laden ones.9 In short, the problem is not the sugar, it’s the acid! We have large numbers of people volunteering for studies like this as they consume large amounts of acid containing, sugar-free soda pop and still get cavities even though they aren’t feeding the bacteria.
On a local level, what is dentistry to do? In short, everything we have been doing. Continuing to decrease oxidative insult by improving cleansability is good. If we see this as reducing the bacterial cause of disease, however, it is doing the right thing for the wrong reason. Going forward, we realize that with the infectious or bacterial paradigm we have run out of options other than more of the same. While this is lucrative and comfortable, it is not what people expect of health professionals. Dental health leadership will require a new understanding of the disease and the health process to grow to our full potential.
A MAP FOR UNCHARTED TERRITORY
Let’s test the power of this new inflammation paradigm in the area of oral/systemic health links. Type 2 diabetes mellitus has been directly linked to periodontal disease.10 This has become common knowledge in the dental community today. A high glycemic meal, like coffee with sugar and a donut for breakfast, creates a hyperglycemic challenge or a blood sugar spike followed by an insulin surge. This activity has been shown to increase oxidative stress both by increasing oxidation and reducing antioxidants.11 Pre-diabetes, also called Syndrome X and Metabolic Syndrome, is a process of diabetesing that could take 7-10 years. This is a critical time for people because the disease process is often reversible but not significant enough to be treated with insulin.12 Dentists, through monitoring of periodontal health, have a direct window to the person’s health.
The significance of this realization is huge. In the past, dentists have been sued for not diagnosing periodontal disease. In the future, it is easy to speculate how dentists will be held liable for not informing the patient/client of their pre-diabetic condition. Described as the epidemic of the 21st Century, the American Diabetes Association claims “There are 41 million people in the United States, ages 40 to 74, who have pre-diabetes. Recent research has shown that some long-term damage to the body, especially the heart and circulatory system, may already be occurring during pre-diabetes.” That’s almost 15% of the population and many of them are in our dental offices today. Doctors Tenenbaum and Goldberg published an article on dentist’s responsibilty in the February, 2006 issue of the Journal of the Canadian Dental Association (Page 38-39). If dentists are going to assume a doctor role, they must also assume the responsibility for oral/systemic health links like perio/diabetes. Scaling and root planning, while lucrative, is a technical service that could be recommended by a dental hygienist.
Dentists should and will be held accountable on a systemic level. Many are not prepared for this challenge. How would you explain the relationship of periodontal disease, traditionally known as a bacterial disease, to type 2 diabetes
mellitus, traditionally known as an insulin deficiency disease? The inflammation paradigm links both periodontal disease and diabetes to excessive oxidative stress. Periodontal breakdown by the body’s own immune system is a localized symptom for dentists, while the rapid aging, neuropathies, retinopathies and cardiovascular complications of diabetics appear as more generalized symptoms. The disease, however, is the same. It is free radical disease causing oxidative stress, resulting in inflammation and breakdown either in areas of abuse or genetic weakness. The same case can be made for cardiovascular disease,13 osteoarthritis14 and even some cancers.15
Now that we understand the linkages of all these symptom diseases through the inflammatory response, we should be able to use our new paradigm or map to plot a course of action, just as Mendeleeev did with his Periodic Table. As traditionally trained professionals, we now recognize that we are not so much health professionals but specific area, disease symptom therapists. I can tell you from personal experience that this can be very upsetting. We now understand that there is a common disease root for all of the lifestyle related, degenerative, inflammatory disease symptoms in all parts of our body. It is free radical disease, or more accurately, free radical diseasing. It is a process. Therefore, whatever we do as dentists to minimize the oxidation caused by free radical disease in the oral cavity will have a whole body impact. For example, C-reactive protein is implicated as a predictor of cardiovascular disease.16 Periodontal disease can stimulate C-reactive protein and periodontal therapy can decrease it.17 Germ theory cannot explain this fact. Free radical theory can by understanding that as we decrease free radicals and oxidation locally, we decrease oxidation systemically. This decreases oxidative stress and the need for the inflammatory response and the progression of degenerative symptoms system wide.
Preventive care is health support rather than disease repair. It focuses on diseasing (verb) rather than the disease (noun). Above all, however, it requires each person to take responsibility for themselves. Clients seek information, education, support and want to be involved in the process. Patients need to be motivated, controlled and passive in a procedure dependant on the dentist. There is little we can do that the client/patient can not overcome by neglecting responsibility. This fact is precisely why I believe dentistry is presently better positioned than any other discipline to lead in the health and wellness paradigm. Time will tell whether we use this advantage wisely.
Management guru, the late Peter Drucker, used the example of the railroads. Back in the 40’s, railroads were in the lead position to found the airlines. They had the ticket agencies, the hotels, the food services, and more. BUT, they defined their business as driving trains instead of moving people and cargo. This was a critical business error as the airlines soon almost put the railroads out of business. Will dentistry define its business as fixing teeth and do everything to focus its efforts on treating people like patients, or will it define its business as facilitators of health and wellness to serve the growing segment of clients? It is beyond the scope of this article to speculate on this decision, but the former option will be a lot more comfortable than the latter. The former requires management. The latter requires leadership.
Our existing tools like toothbrushes, floss, mouthwashes and others are well suited to decreasing local oxidation. Regular recall dentistry supports this as well. Reducing acidic soda pop, either with or without sugar is necessary. Sorsa’s research indicates that it is the acid that causes the oxidative stress and stimulates the tooth to break itself down. Sugar only serves as a fuel for bacteria to produce a constant source of acid. If you change the carbohydrate from sucrose to zylitol, there is no acid production.18 If you change the strep mutans to a non-acid producing hybrid like Hillman did in Florida,19 there is no acid, no oxidative stress and no decay. If you provide only acid like sugar free soda pop drinkers, there is nothing to feed the bacteria, but still the acid and still the decay. Bacteria do not cause the dental decay. Localized oxidative stress caused by acid overwhelms the body’s antioxidant defense system and decay is the result of the body’s inflammatory response breaking down the tooth’s collagen. Supporting the antioxidant defense system is a preventive tool which dentistry has never seriously considered. While some antioxidants like green tea catechins have been studied for their beneficial effects on dental health,20 one wonders if the effect was really local or is it systemic based on the inflammation paradigm. In short, catechins are really enhancing the odontoblast’s antioxidant potential to minimize dentin matrix breakdown, so their greatest effect is when they are swallowed and absorbed rather than rinse and spit. When this is the case, we should see other systemic effects as well. We do! This is the same for periodontal tissues.21,22 Go further systemically, catechins have also been shown to have a beneficial effect on diabetes mellitus,23 cardiovascular disease24,25 and cancer.26 Now this is truly whole person, health centred dentistry.
There is also dentistry’s growing responsibility and our potential in the area of nutritional glycemic control. There is an insurance code for nutritional counseling, but it does not appear in the Ontario Dental Association’s list of the top codes used. Would that be because it is not a code that insurance companies pay for or because it is something that dentists simply are not doing or feel incompetent to do? Will it take a lawsuit to move the profession to take nutrition seriously? The trial lawyer will ask the defending dentist if he was aware of the potential diabetic implications of the patient who he had been treating for periodontal disease for 7 years but never thought to mention the diabetes connection. As soon as the dentist says “Yes”, the judge says “Guilty of negligence”. A dental hygienist is only responsible for assisting the dentist with the technical service. The dentist, however, is held responsible for diagnosis and treatment planning. It is a rude awakening when we find there is little economic support for our doctor role, but significant support for our hygiene supervisor role. Clearly, there is a problem that needs to be addressed here, but that too is beyond the scope of this article.
Let’s apply the inflammation paradigm to public health. As an example, let us use the aboriginal areas of Northern Ontario, which are known to be high risk for diabetes and dental decay.27 Dental hygienists have used these areas as examples of why we need independent hygiene services in Ontario. If bacteria were the cause of oral disease, this would be a good argument. However, it is very labour intensive and costly. Educating people to change lifestyles, improve oral hygiene and alter dietary habits is always a challenge. Why don’t we begin a public health initiative to provide multivitamin/mineral/antioxidants to the native communities. Swallowing a pill doesn’t take extra time or effort for the individual, involves no lifestyle changes, is relatively economical and would have an effect not only on their dental health but on their diabetic risk level by reducing inflammation. This is the same philosophy that dentistry used with fluoridation. Focus first on changing the system by adding fluoride or antioxidants rather than treating the people with more fillings and scaling or lifestyle changes.
DECISION TIME
The emerging discipline of whole person dentistry will move the profession into uncharted waters. While education of dental team members and clients will take time, the biggest hurdle will be in unlearning what we already know about infectious and bacterial disease patterns and relearning a new inflammation paradigm. Regarding the question
of whether dentists should assume a leadership role in whole person health or not, I personally don’t think we have a choice. It is our professional obligation to do so. The bigger question is whether our ladder is leaning against the right wall?
Dr. Ken Southward graduated from the University of Toronto’s Faculty of Dentistry in 1971. He has practiced general dentistry in Beamsville, ON, since that time.
Oral Health welcomes this original article.
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Dentistry has existed in a paradigm or understanding of bacterially caused dental diseases. Recent efforts to link periodontal disease to diabetes and cardiovascular disease have not been able to determine if bacteria are causal or casual to the relationship. This article presents evidence that inflammation caused by oxidative stress is the common link. The realization that bacteria are not the cause, but only casual to dental disease, presents both ramifications and opportunities for dentistry. The dental profession is encouraged to explore the treatment, prevention, public health and legal implications of this new paradigm.
