Oral hygiene has been a problem plaguing America for many years now. From reminding children to brush their teeth at least twice daily to encouraging regular dentist visits, there have been numerous efforts to keep America's oral hygiene as clean as possible. Bad oral hygiene can cause diseases such as gingivitis, periodontitis, and oral cancer. These can all be caused by simple lack of cleaning or neglect in taking care of infections. However, one of the main causes of deterioration in the oral cavity that often goes overlooked is that of tobacco use. Smoking alone has been shown to increase a person's chance of getting oral cancer by two or even five times more than a nonsmokers' (Winn, 2001). According to the World Health Organization, over fifteen billion cigarettes are smoked in one day worldwide. As if this staggering statistic was not enough, even smokeless tobacco can cause oral cancer in its users (Rodu et al., 2004). Together, these two forms of tobacco consumption severely increase the chances of a person developing some form of oral disease. While many oral problems such as gingivitis can be treated with medication and do not become fatal over time, the symptoms and health problems associated with oral cancer can be extremely painful and can even lead to death. Different sanctions have been placed on cigarette and tobacco sales to help minimize these risks, but the tobacco industry in America and other countries continues to grow and affect more people every day. Thereby, the problem of tobacco and the effects it has on the oral cavity is one that needs attention and should be dealt with.
Types of Tobacco
There are many different types of tobacco on the market worldwide, thereby increasing the target population for each type of product. For those who would prefer to light the tobacco and smoke it, there are varying types and degrees of tobacco available. For the majority of the world there are cigarettes, which themselves are a very dangerous type of tobacco. However, if not cigarettes, consumers have options such as pipe tobacco, cigars, and even some other forms of tobacco in foreign countries. One such example is the bidi, a small cigarette smoked by nearly half of all smokers in India (Ray et al., 2009). While smaller than most cigarettes, and sometimes containing even less tobacco, bidis can contain even more nicotine and carcinogenic agents than most conventional cigarettes. Even though there has been heavy government taxation on many of these products, smoking tobacco continues to be one of the largest industries in the world today, and certainly one of the largest in the United States.
As if smoking tobacco was not enough to entice consumers with its varying forms, there are also many forms of smokeless tobacco that can actually turn out to be even more destructive to the oral cavity than combustible tobacco. The two most common kinds of smokeless tobacco are chewing tobacco and snuff tobacco, and should not be confused with one another. According to the Mayo Clinic, snuff tobacco is basically fine cut tobacco that can be pinched into a little ball or segment and then placed into the mouth. The nicotine and various other components of the tobacco are then directly absorbed by the saliva. On the contrast, chewing tobacco is the use of whole leaves of tobacco that are placed in the mouth, usually between teeth and cheeks, and then ground by chewing to release flavor and nicotine. Both of these forms of tobacco are said by some groups to be less destructive to the oral cavity, while others claim that they are even more carcinogenic than smoking tobacco. There is not significant evidence to really support either side, however, the fact that the same chemicals that are carcinogenic in cigarettes are also contained in smokeless forms of tobacco would indicate that smokeless tobacco is just as harmful if not more harmful than smoking tobacco.
Smoke vs. Smokeless
There are many manifestations of tobacco in our world today. Perhaps the most studied and recognized form is that of cigarettes, which release harmful smoke when burnt both to the smoker and to the surrounding environment. Smoking has long been considered one of the primary causes of death related to cancer in the United States, as nearly 40-45% of all cancer-related deaths are due to smoking; of these, nearly 85% of all oral cancer deaths are derived from smoking (Johnson, 2001). Smokers enjoy the many chemicals that are used to make cigarettes, including chemicals such as ammonia, nicotine, and even mace powder. Of these chemicals, nearly 300 have been found to be carcinogenic (Johnson, 2001). Cigarette tar contains most of these carcinogens, and even some other forms of smoking tobacco, such as pipe tobacco contain these compounds. Even non-smokers can be put at risk for cancer because of other smokers. Studies have shown that simply from their environment, people who are exposed to secondhand smoke are 1.6 times more likely to develop periodontal disease than those not exposed, and can contain as many as 60 different carcinogens (Arbes et al., 2001).
Smokeless tobacco has also been shown to cause cancer in its users. In countries such as India, smokeless tobacco is not only used as much as cigarettes, but actually contains more nicotine than most American cigarettes (Ray et al., 2009). The danger in this is that these certain brands of smokeless tobacco are even more addictive due to the raised levels of nicotine, and also contain up to 20 different carcinogens, including various nitrosamines and inorganic compounds (Ray et al. 2009). Additionally, the risk for other oral diseases besides cancer caused by smokeless tobacco is also increased due to the increased exposure to tobacco chemicals for a longer period of time.
The levels of carcinogens in both smoking tobacco and smokeless tobacco vary depending on the brand and type of each. There are many different types of cigarettes available in each country. In America alone, there are many different types of cigarettes available, as well as numerous types of smokeless tobacco. Depending on the filter, the method of inhalation or intake of the tobacco, as well as the individual production method of each brand, the various chemicals can have different effects on the individual using them; the only constant, it seems, is the ability of each brand and type to cause some sort of oral malignancy.
Tobacco and Oral Cancer
As stated above, tobacco products contain many different compounds that can cause and proliferate oral cancer. Most malignancies first present themselves in the oral cavity as a squamous cell carcinoma (Johnson, 2001). They can then either be removed via surgery, or, if gone undetected, they can become malignant cancers extremely dangerous to the patients' health. The tissues that are most commonly affected by the cancer are those of the lips and tongue, although almost any tissue in the oral region can be affected. The most common way to identify cancer in the oral region comes from testing or examination of a lesion, ulcer, or otherwise displaced epithelial condition such as a lump or some form of discoloring. Tobacco products can cause most of these conditions without their harmful chemicals simply from irritating the various mucous membranes of the oral region from heat and smoke, or juices found in smokeless tobacco. The ulcer or lesion can then become a cancer if certain oncogenes are activated. The mode of this activation is so far unknown, but there has been a strong correlation shown between cancer patients and tobacco users. Oral cancer patients, especially, have a high percentage of tobacco users.
There has been extensive research into the various components of tobacco products that could potentially be carcinogens. Nearly 300 different compounds have been shown to have a connection with the formation of cancer cells either through the transmission of smoke through the body or through absorption of chemicals through saliva (Johnson, 2001). Some of the most studied carcinogens include different hydrocarbons, especially benzo-pyrene, and many different nitrosamines (Johnson, 2001). The carcinogen acts by coming into contact with cells and structures that will metabolize and form DNA adducts that, once incorporated, will initiate carcinogenesis (Warnakulasuriya et al., 2005). Additionally, there has been a correlation seen with alcohol and tobacco in causing cancer in patients who used both (Johnson, 2001). Although there is little evidence that alcohol alone can cause oral cancer, in conjunction with carcinogens from tobacco products it can significantly raise the advent of cancerous cells in the oral region of a user.
Another family of carcinogens common to many tobacco products is that of the nitrosamines. Different tobacco products have a different nitrosamine component, but many different nitrosamines have been shown to be carcinogenic. In fact, nearly 90% of all nitrosamines have been shown to be carcinogenic in humans. Nitrosamines are developed during the tobacco curing process as nicotine and other related compounds undergo a nitrosation reaction. Unlike aromatic hydrocarbons, the other major carcinogen found in tobacco products, nitrosamines can be found in both smoking and smokeless tobacco, because they simply need nicotine and other smaller components found in all tobacco to be produced. Therefore, these are even more dangerous than hydrocarbons, which are usually found only in combustible tobacco. However, nitrosamines are found in both kinds of tobacco, and are actually a major component of the carcinogenic molecules in both. Nitrosamines also work a lot like aromatic hydrocarbons, in that they bind to DNA chemically to form a DNA adduct that will later go on and mutate to form cancerous cells.
Together, these two carcinogens account for most of the cancer-causing activity in tobacco. A less studied, but also dangerous component of tobacco products is nicotine. Although it has not been shown to be carcinogenic in cells alone, there have been very few studies to research whether or not nicotine can become carcinogenic in conjunction with other compounds found in tobacco products. Also, nicotine is the addictive factor of most tobacco products, ensuring that consumers continue to buy and use tobacco products even if they do not want to. In addition, nicotine has been shown to prevent apoptosis, which is the mechanism the body uses to rid itself of unwanted cells. Cancer cells are some of the cells that the body uses apoptosis to destroy, and if apoptosis is impeded by nicotine, then some cancer cells, which may normally have been destroyed, remain intact. In this way, nicotine can help initiate and complicate oral cancer.
Buccal Cell Mutations
Often the first signs of oral cancer can go unnoticed, further complicating the disease that could be prevented or treated if caught early enough. However, one of the good things about oral manifestations of cancer is that the oral region is easily viewed and monitored by the naked eye. Researchers are thereby able to perform various tests and experiments to view the changes that the oral cavity may undergo when exposed to tobacco products. For example, researchers can use tissue dyes in the mouth to see lesions develop and to identify them as malignancies before they have a chance to develop and become harmful to the patient (Proia et al., 2006). Oral cells, or buccal cells, are excellent for monitoring mutations to see the progression of cancer as a result of tobacco use. Some of the changes they might see include genetic changes as well as non-genetic changes that all point to a mutation that may lead to cancer.
In buccal cells, the mutations occur at a cellular level, either changing cell morphology or causing a mutation in the DNA, rendering the cells to perform functions other than their own. These mutations have been hypothesized to be caused by tobacco chewing and smoking in various studies (Proia et al., 2006). In many of these studies, it seems that smoking has a positive correlation with buccal cell mutations, and chewing tobacco has an even higher correlation as well as a higher percentage of cells mutating in response to exposure to the tobacco (Proia et al., 2006). However, further research is needed to correctly identify the mechanisms of infection as only the correlation has been proven thus far. However, the research and examination of buccal cells is an integral part of learning about the true adverse effects that tobacco products and their constituents have on the oral cavity.
Periodontal Disease
Periodontal disease is basically a dysfunction of any one of the periodontal tissues located in the oral cavity. The two most general and common of these diseases are gingivitis and periodontitis.
Gingivitis is usually just inflammation of the gums, caused by foreign toxins or bacteria introduced to the gums. While plaque formed by bacteria and their toxins is usually the primary cause for gingivitis, there are other factors that can also bring about inflammation of the gums and in turn extreme discomfort to a patient. Because even the smallest change or collection of chemicals can cause gingivitis, tobacco chewing and smoking are ideal candidates to bring about the disruption of the gingiva (or gums). Many of the components of cigarettes and smokeless tobacco have a very negative effect in the mouth, and one of the most sensitive parts of the mouth are the gums. When elements such as lead are released from cigarette smoke, they can attach to and irritate the gingival area and cause inflammation. Studies also show that the amount a person smoked in one day was directly proportional to the onset of periodontal disease (Winn, 2001). People who smoke more have a higher risk of periodontal disease than those who smoked less. In addition, people who smoke but develop some form of periodontal disease from another cause, such as bad hygiene, have a much harder time recovering from the disease than non-smokers (Winn, 2001). Once again, tobacco not only causes disease in the oral region, but also complicates the healing process from other diseases.
Gingivitis, if gone untreated, can cause further complications. Loss of teeth, long-term gingivitis, or further infection are all possible scenarios. The irritation also opens up the possibility of more chemicals being absorbed into the oral cavity and further complicating what started as a simple irritation or inflammation. Gingivitis can lead to more serious diseases, such as periodontitis.
Periodontitis occurs when the tissues that support the teeth become inflamed or infected, and eventually can lead to massive tooth loss. There are many different things that can cause periodontitis, such as plaque build-up due to bad hygiene, or even malnutrition. However, periodontitis can occur as an extension of gingivitis, which can occur from smoking or chewing tobacco. Also, if one of the chemicals in a certain brand or type of tobacco is toxic to the periodontal tissue, it can bring about the onset of periodontitis. As is true with gingivitis, periodontitis can be treated, however, for smokers it is once again much harder to treat and cure periodontitis than it is for non-smokers.
Gingival Recession
Gingival recession is yet another periodontal malfunction that can be caused by tobacco. Mainly a product of chewing tobacco, which can disrupt and sometimes destroy the mucus membrane that lines a person's mouth, gingival recession is basically periodontal tissue dying or being lost, exposing the roots of teeth. This can often lead to problems with tooth stability, and if allowed to go on for an extended period of time, could lead to severe gum loss as well as tooth loss (Winn, 2001). The increased area of the gums that is exposed to bacteria and other dangerous components of the oral cavity also poses a problem, as a person who is chewing tobacco will probably continue to do so, allowing the chemicals to begin breaking down not only what is left of the periodontal tissue but also the teeth and their foundations which are now more exposed. Smoking or chewing tobacco at the time of disease can also lead to complications when trying to better the condition, especially if trying to use periodontal surgery with techniques such as those involving grafting. Because smoking and chewing tobacco can damage all parts of the mouth, the grafts needed to replace the damaged periodontal tissue may be hard to find, and may also be harmed later on if the patient continues to use the tobacco product (as a result of addiction) (Johnson et al., 2001). The problem with tobacco products lie not only in the onset of a particular disease or disorder, but also with the impediment of treatment for the disease later on.
Early Child Caries
One of the biggest problems in the United States, early childhood caries is a very infectious disease that is highly communicable (Hanioka et al., 2008). Caused by specific bacteria that can convert carbohydrates on teeth surface into acid can lower the pH of the dental plaque, slowly destroying teeth and causing ECC. Recently studies have hypothesized that pre-natal smoking can cause or facilitate ECC as well. In some experiments, it was found that maternal smoking did indeed have a direct correlation with ECC; paternal smoking also had somewhat of an effect, but the causational relationship could not firmly be proven (Hanioka et al., 2008). While there are many other factors that can be the cause for ECC, it seems that all these factors are heightened and become more severe due to smoking by the mother during carriage of a child. Environmental factors are also an issue, as decay can be brought on by secondhand smoke in the environment. While this topic is still being researched, and can actually have a lot to do with dental hygiene trends in parents that smoke as much as it has to do with the actual acts of smoking. For example, parents that smoke may for some reason also not brush their developing child's teeth as much as they are supposed to, or not pay attention to the child's diet, since a diet high in carbohydrates may also cause early decay and ECC. Whatever the reason may be, there is definitely some sort of correlation between children of smokers and their knack of developing ECC.
Cannabis Smoking and Periodontal Disease
A recent study had some interesting findings about the younger generation that may never have smoked tobacco, but still had periodontal disease. As it was later determined through experimentation, the disease was actually related to smoking large amounts of cannabis (Hujoel, 2008). The study focused on younger age groups, because even though periodontal disease was thought to affect only those aged 35 and older, the onset and detection of periodontal disease in smokers of either tobacco or cannabis could potentially allow caretakers to identify later, more serious diseases developing in the patient. However, the findings are in their first stages, and there is still much more research to be done in this area. For example, the same experiments must be done with removal of bias, less variable factors, and in different countries with separate genetic dispositions. However, the findings themselves are very interesting, as they indicate that something besides the chemicals in cigarettes made during production may have something to do with the onset of periodontal disease.
Halitosis
Another less dangerous, yet equally irritable condition that can come about by tobacco use is halitosis, or persistent bad breath. Although it can be caused by many different things, such as periodontal disease or poor oral hygiene, smoking is another factor that can contribute to a distinct bad odor secreted from the smoker's mouth (Knaan et al., 2005). Furthermore, smoking can cause some of the main reasons for bad breath. As stated above, periodontal disease is one of the reasons people have bad breath, and smoking is one of the reasons people can develop periodontal disease, thereby making the act of smoking the original cause of halitosis in some people.
Leukoplakia
Leukoplakia can also be one of the effects of smoking on the oral cavity. Although not a particular disease itself, Leukoplakia is simply the growth of white lesions within the oral cavity. While themselves not terrible for a person's health, they are often believed to be pre-cancerous, and a sign of worse things to come (Mishra et al., 2005). Cigarette smoking, chewing tobacco, and other forms of tobacco are cited as the main reasons for Leukoplakia. Coupled with any sort of bacterial infection in the oral cavity, Leukoplakia could indeed become very painful and extremely harmful to a patient's health. Additionally, the advent of white lesions all over the oral cavity may lead to the loss of a few things that many people take for granted, such as the sense of taste.
Passive Smoking
Secondhand smoke can also be a problem for people who do not even smoke regularly (WHO, 2004). Because secondhand smoke contains the same chemicals that the smoke that smokers inhale, it also contains the same carcinogens, such as aromatic hydrocarbons and nitrosamines. Furthermore, it is far more concentrated since the cigarette smokers have a filter on their cigarettes which filters out a lot of the tar and certain chemicals that secondhand smokers cannot avoid. Although most of the effects of passive smoking seem to occur in parts of the body other than the oral cavity, it has been shown that tooth decay, in children especially, is facilitated and complicated due to inhalation of secondhand smoke (Avsar et al., 2008).
Oral Candidiasis
Oral Candidiasis is an oral overgrowth of yeast caused by any one of the pathogenic Candida species: Candida albicans, Candida glabrata, and Candida toropicalis. Normally only a fungal infection, the onset of oral candidiasis can be advanced by the presence of tobacco smoking (Soysa et al., 2005). While the specific pathogenicity of cigarette smoke may not be known in accordance to the Candida species, it has been shown that smokers are at a higher risk of developing oral candidiasis than non-smokers. There has even been some research that suggests that the infection will recede and dissipate if the smoker simply stops smoking, without even the need for anti-mycotic treatment (Soysa et al., 2005). While there are many different causes for oral candidiasis, including diabetes or a compromised immune system, smoking had been one of the causes that had only been considered but not proven for a long time. Recent research, however, suggests there is a stronger correlation between the two, and as is shown by the dissipation of the infection once a smoker has given up smoking, oral candidiasis can be a direct result of smoking cigarettes. Another interesting study that was performed was that of seeing the correlation between smoking and another known cause of oral candidiasis. For example, studies were done on people who had diabetes and were also smokers. While the carrier rate of oral candidiasis infection was increased, the density of the infection was not (Soysa et al., 2005). Therefore, smoking only increased the chances of getting the infection, but did not actually complicate or increase the rate of infection. Even when patients undergoing chemotherapy who smoked were monitored for infection, those who were smokers had a higher rate of infection than those who did not (Soysa et al., 2005).
Thus, a correlation has been found, but the mode of pathogenicity is yet to be determined absolutely. While many hypotheses have been made, especially centering around epithelial disturbances promoting the growth of infectious diseases, there has not been any conclusive evidence as of yet for the mode of pathogenesis by which cigarette smoking causes oral candidiasis.
Porphyromonas gingivalis
One of the pathogens found in the oral cavity that is known to cause periodontal disease, Porphyromonas gingivalis has been shown to be even more likely to cause disease if introduced to tobacco smoke (Bagaitkar et al., 2009). A non-motile bacteria, P. gingivalis is gram negative, rod-shaped, and is anaerobic. Thus, the loss of oxygen from the oral cavity as a result from smoking only benefits the organism and allows it to grow. Tests were done where the bacteria was exposed to cigarette smoke extract and then plated and observed to determine results. For comparison, there was also a control group that was not exposed to cigarette smoke extract. The bacteria that had been exposed elicited a far less toxic response from immune system cells from the body, whereas the control bacteria found itself in the typical toxic environment it could expect from the body's monocytes and other immune cells (Bagaitkar et al., 2009). The study also used DNA microarrays to see if there was any conformational change in the DNA once the bacteria was exposed to cigarette smoke, and as it turned out, there was close to a 6.8% change in the gene pattern for the bacteria once exposed to the smoke extract. Furthermore, there was a significant change in the outer surface proteins of the bacteria, which are in fact the portion of the pathogenic agent that actually bring about the onset of disease (Bagaitkar et al., 2009). All of these findings are extremely relevant and very interesting, because they suggest that smoking alone can alter an already pathogenic species in the oral cavity and make it something worse and increase its pathogenicity. In conclusion of the study, it seemed that this altered state of P. gingivalis was actually more likely to cause periodontal disease than the original state. Therefore, smoking alone had caused a conformational change in the species and made the host more susceptible to periodontal disease. As an extension to this same general idea was that the components in cigarette smoke may also cause changes in the host cell environments, rendering some of them less potent against invading cells. This is true for chemicals such as nicotine, which can suppress the release of certain inflammatory chemicals that can help rid the body of intruding bacteria. Coupling the botched immune system as well as the increased pathogenicity of the bacteria present, cigarette smoke can easily and quickly increase the chances of a smoker getting periodontal disease.
The Future
The future of tobacco research seems to be growing and continues to be one of the most debated industries in the world. While tobacco consumers continue to buy various products to satiate their thirst for nicotine, oral health advocates scream for reform and outline the many different adverse effects that any type of tobacco can have on the oral cavity. As outlined in this paper, there is still plenty of research to be done. While the specific carcinogens in tobacco have been identified and their mode of infection outlined, there is a need to figure out how to prevent and maybe even stop their route to oral disease. From casual halitosis to deadly oral cancer, there are many adverse effects of tobacco use; however, consumers continue to smoke and use tobacco just as much, if not more, than they used to. The concept of quitting is an easy one to understand, by simply not smoking, one can lower the risk of getting periodontal disease or oral cancer by a significant margin; however, very few people in today's world find the power to quit tobacco once they have become addicted. They are the minority, and instead of preaching to them about quitting, there is plenty of research that can be geared towards prevention and possibly even reversal of tobacco's adverse effects.
There is still some consternation about the specific effect of smoke upon the oral cavity. As the experiment with cannabis showed that there was indeed some correlation with simply smoking and periodontal disease, it is important to find out the common factors between cigarette and cannabis smoke that can increase a person's potential to develop some form of periodontal disease. Also, in the studies regarding oral candidiasis, there was definitely a correlation between cigarette smoke and infection, but once again more research was needed to determine the actual virulence factor in cigarette smoke that brings about this relationship. Many of the main carcinogens that are found in cigarettes are not in cannabis, but there may be aspects of both that coupled with other things can lead to oral cancer still, even if the known carcinogens were removed. As the experiment with P. gingivalis proved, smoking itself can cause conformational changes in cells in almost any environment. Buccal cell mutations have been observed, but there is a need for calculation and even prediction for the rates and changes that these mutations will occur at, so that the outcome of each can be predicted. While we have seen what can occur, we need to observe and research until we can fully predict what will occur.
Another aspect of research that a lot of studies have not focused on that needs to be dealt with in the future is that of increasing the subject pool to include more than one genre of person. For example, a lot of studies focused on solely the effect of tobacco smoke and its constituents do not take into account genetic predisposition and how various diets from other countries might have an effect on the cigarette smoking. Most of the research done until now has focused solely on the problems of tobacco on the oral cavity, but now that a lot has been understood and outlined, it is imperative to study the difference between different cultures and how various gene pools will react to the same stimuli.
Finally, the studies that have been developed for now tend to use random subjects that may or may not be trusted, as well as subjects that have the same general smoking habits. For example, a study might ask a number of non-smokers to begin smoking and then measure the adverse effects. In contrast, another study might choose a large number of smokers and then base their results off of them. Because each person's body reacts differently to any given drug and the various changes that each individual person goes through is impossible to measure, there are a number of variables that cannot be tested. The best results come from experiments where simple cells are taken and then exposed to tobacco constituents, but even then the results can depend on where the cells were obtained, and are once again not great indicators for what would happen in an actual human body environment.
Conclusion
The tobacco industry worldwide is a very large and lucrative one. Despite numerous studies, steady taxation, warning labels, and other campaigns aimed at hindering the use of tobacco worldwide, it continues to be one of the most addictive and used products in the world. From smoking tobacco products to using smokeless products such as chewing or snuff tobacco, the many varieties, flavors, and brands available in the market only raises the opportunity that a new youngster will find something to his taste and, like so many others, feel the pain and agony that often accompanies extensive tobacco use.
The world of oral hygiene is very well-studied and delved into, and as of late there are many different effects that tobacco has on the oral cavity that have been discovered due to these efforts. From learning about the various agents found in tobacco products that may be carcinogenic, to understanding the methods of causing periodontal disease by the various agents found in tobacco products, scientists and researchers have come to a greater understanding of how tobacco affects the oral cavity, and can now take steps to define and develop new ways to prevent further manifestations of oral disease. While cancer remains an elusive foe that has baffled many a researcher in the past years, understanding what causes it and where the carcinogens come from is a vital part of solving the puzzle.
The biggest problem with the world of tobacco users is their inability to understand what constant tobacco use can do to the oral cavity. Some lesions are not malignant and tobacco users might ignore them and continue to use tobacco, causing further complications. Perhaps the greatest tool in preventing oral disease in the future is continuing to educate users before they get started, and work on ways to help combat the negative effects of tobacco for those who have already begun.
