Teeth Nightmare: Cavities

Tooth
Figure 1: Tooth structure (Gordon, n.d.)

I must admit that I have a lot of teeth cavities. Needless to say, going to the dentist has been – and still is – a nightmare for me. Perhaps my tendency of getting tooth cavity is inherent (Fotek, 2012), or perhaps it is simply due to my lack of care when I brush my teeth. Either way, I am curious about how cavities actually form, so I’ve decided to explore tooth decay in hope of finding a way to keep my teeth healthy.

Simply put, cavity – also known as dental caries (Gordon, n.d.) – is a teeth infection that is related to bacteria and causes the decay of the tooth enamel. The enamel is the outermost layer of the teeth and the hardest and most mineralized substance in the body (Gordon, n.d.) (see figure 1). However, despite its hardness, the enamel can be damaged when interacting with bacteria and food, typically the carbohydrates. While the mouth has many different types of bacteria, only few, such as Streptococcus mutans, Lactobacillus casei, and acidophilus, are associated with cavities (Gordon, n.d.). These bacteria stick to the surface of the teeth and form a sticky film called dental plaque (National Maternal & Child Oral Health Resource Center, n.d.). When carbohydrate-containing food is consumed, these bacteria eat the carbohydrates and release acids, attacking the teeth enamel, usually within 20 minutes of eating (Briseno, n.d.). Normally, the pH in the mouth is about 6.2 to 7.0, but it drops after eating. When the pH reaches 5.2 or below, the acid begins to dissolve the enamel (Gordon, n.d.). Continuous acid attacks result in cavities, which, if not treated, can extend into the living pulp tissues (see figure 1), where the bacterial infection can spread to other parts of the face and body (National Maternal & Child Oral Health Resource Center, n.d.).

Here, acid’s reaction with the tooth links into our study in IB Chemistry of acid’s corrosive property. The enamel, or calcium-deficient carbonated hydroxyapatite (, is composed of mineral, protein, lipid, and water that form a crystal lattice (Lussi, 2006). The hydrogen ions, released by the acid in the mouth’s aqueous environment, react with carbonate and phosphate ions in the enamel, causing the mineral ions to be etched away and hence demineralizing the tooth, as illustrated below (Lussi, 2006):

Ca10xNax(PO4)6y(CO3)z(OH)2uFu + 3H+ →  (10-x)Ca2+ + xNa+ + (6-y)(HPO42) + z(HCO3) + H2O + uF

(note: Ca10xNax(PO4)6y(CO3)z(OH)2uFu + 3H+ is the enamel)

As a result, the enamel surface is reduced and softened (British Dental Association, 2004), which can cause toothaches (Fotek, 2012). Fortunately though, our body has a way of combating tooth decay. Through minerals in the saliva that act as buffers, our body is able to remineralize and repair the damaged enamel automatically (British Dental Association, 2004). Similarly, the fluoride in toothpastes also has the same effect (British Dental Association, 2004).

Essentially, the culprit for teeth decay is the acid and not the sugar. In fact, acid can also erode the teeth when consumed directly. Acidic drinks, such as soft drinks and lemon juice, double the damage to the teeth, because these drinks are high in both acid and sugar. Interestingly, yogurt is low in pH yet it doesn’t have erosive potential due to its high content in calcium and phosphate (Lussi, 2006). Therefore, the erosive potential of acidic drinks depends on a variety of factors, including their pH, mineral content, type of acid, and adhesion to the teeth (Lussi, 2006).

After knowing acid’s pernicious effects to the teeth, I can now understand why dentists ask us to brush our teeth regularly. As mundane as it may sound, brushing the teeth is the easiest way we can maintain our dental health. In addition, fluoride toothpaste should also be used, because study has shown that regular brushing by itself doesn’t prevent teeth decay while brushing with fluoride toothpaste does (British Dental Association, 2004). As a general rule of thumb, eating starch-based food with acidic drinks should be minimalized if not avoided.

In my research, I also came across physical factors that cause tooth wear, but I’ve decided not to go further as my focus was on teeth decay. However, for further exploration, an interesting area to go into could be gum diseases, because they are also caused by plaque buildup but involve studies of the bones and tissues that support the teeth (National Institute of Dental and Craniofacial Research, 2012).

You may ask, after reading all this, so what – what’s the big deal with dental awareness? Many of us take our teeth for granted, and perhaps don’t realize just how crucial a role they play. Without a set of healthy teeth, we will not be able to enjoy the scrumptious dishes we consume everyday. In short, our teeth are a fundamental if not indispensable link to our dietary health. It is, therefore, important to understand the nature of tooth decay to help us prevent it. Hopefully, after the short reading from above, you’ll think twice before you eat sugar-rich food and soft drinks the next time.

Bibliography

Briseno, T. (n.d.). What wears down tooth enamel, and how can you prevent it?.Discovery Fit & Health. Retrieved March 2, 2013, from health.howstuffworks.com/wellness/oral-care/problems/what-wears-down-tooth-enamel1.htm

Fotek, P. (2012, February 22). Toothaches. Medline Plus. Retrieved March 2, 2013, from www.nlm.nih.gov/medlineplus/ency/article/003067.htm

Gordon, J. (n.d.). Cavities and Fillings 101. Discovery Fit & Health. Retrieved March 2, 2013, from http://health.howstuffworks.com/wellness/oral-care/problems/cavity1.htm

Lussi, A. (2006). Dental Erosion. Basel: Karger.

Periodontal (Gum) Disease: Causes, Symptoms, and Treatments. (2012, August). National Institute of Dental and Craniofacial Research. Retrieved March 2, 2013, from http://www.nidcr.nih.gov/OralHealth/Topics/GumDiseases/PeriodontalGumDisease.htm

Tools. (2004). British Dental Association. Retrieved March 2, 2013, from www.3dmouth.org/1/1_2.cfm

Tooth Decay. (n.d.). British Dental Association. Retrieved March 2, 2013, from www.3dmouth.org/2/2_3.cfm

What is Tooth Decay. (n.d.). National Maternal & Child Oral Health Resource Center. Retrieved March 2, 2013, from www.mchoralhealth.org/OpenWide/media/flash/decay_flash.htm

Image

Gordon, J. (n.d.). Cavities and Fillings 101. Discovery Fit & Health. Retrieved March 2, 2013, from http://health.howstuffworks.com/wellness/oral-care/problems/cavity1.htm

Lussi, A. (2006). Dental Erosion. Basel: Karger.

2 thoughts on “Teeth Nightmare: Cavities

  1. As a fellow student who is also a victim of teeth cavities problems, I thought it was necessary that I understand how toothpaste can properly prevent teeth cavities. In her post, Angela mentioned how fluoride toothpaste can be used to maintain dental health, but how? I researched in an attempt to understand what and why certain chemicals are found in toothpaste, and how they are able to prevent the acid-secreting bacteria from reacting with the enamels of our teeth.

    To understand how toothpastes are able to maintain one’s dental health, one must first understand what are the chemicals and their required characteristics that are found in toothpaste. Since teeth cavities are created by the bacterial plaques, toothpastes designed to physically scrub away the plaques and prevent future plaque buildups. While different companies have different toothpaste formulas that appeal to different consumer needs, most toothpaste includes chemical ingredients that are abrasives, detergents, humectants, thickeners, preservatives and flavor and color enhancers. (The Cosmetic, Toiletry, and Perfumery Association [CTPA], 2013). Calcium carbonate is often used as the preferred abrasive since it has a hardness greater than the plaques and other contaminates, but less than that of tooth enamel to prevent ironic creation of cavities and damage to the dentine, the bony tissues underneath the enamel. Using a toothbrush, the repeated rubbing of the abrasive with the surface of the teeth will eventually remove the plaques and contaminates off the enamel of the teeth. (Wikipedia, n.d.)(WebMD, n.d.). Detergents, such as sodium lauryl sulphate, are used to reduce the surface tension of toothpaste to allow it to be spread across the teeth. Simply put, detergents are responsible for the creation of foam when one brushes his or her teeth. (Beach, E., 2011) Thirdly, toothpastes contain humectants, such as glycerol, that are responsible for moisture retention to prevent the toothpaste from drying out. In addition, cellulose gums, a common thickener in toothpastes, are also extracted from seaweeds to provide and maintain toothpastes with their gel-like texture and characteristics so that it can be effectively transferred on a toothbrush. (WebMD, n.d.) Antimicrobial ingredients and preservatives, such as triclosan, can also be commonly found in toothpaste to prevent bacterial growth in the toothpaste as well as future plaque build-ups. (CTPA, 2013) Last but not least, toothpastes usually contain flavoring and coloring agents to make the toothpastes aesthetically and tastily pleasing.

    Image 1: Toothpaste Ingredients: http://www.volunteerorganic.com/2012/03/20/recommended-dental-care/

    While there is a myriad of chemical ingredients used in toothpastes, there is one chemical that is universal chemical, fluoride. “Fluoride is a naturally occurring mineral,” that is found in most, if not all, of the most popular and most effective toothpaste brands. In fact, studies show that fluoride was responsible for the dramatic drop in tooth decay and cavity occurrence over the past 50 years. (WebMD, n.d.). Fluoride is capable of protecting your enamels from acid-secreting bacteria in two ways. One way it does this is by strengthening the enamel to reduce the chance that it will suffer acid damage. This is because the fluoride ions are chemically bonded to the calcium and phosphate minerals that make the enamel less susceptible to demineralization, the dissolving process that causes cavities, by the acids. (Vankevich, 2011). “The presence of fluoride causes the formation of enamel fluroapatite by substitution of hydroxyl molecules with fluoride in the hydroxyapatite crystal.” Secondly, fluoride is able to remineralize enamel areas that are affected with early stages of acid damage. During the remineralizing process, “the fluoride ions react with the partially dissolved enamel crystallites and attracts calcium and phosphate ions into the saliva to the demineralized dental enamel.” (Roberts, M., Wright, T., 2009).

    Image 2: Demineralization and Remineralization: http://kquinto.livejournal.com/1794.html

    Image 3: Demineralization and Remineralization: http://www.dimensionsofdentalhygiene.com/ddhright.aspx?id=5380

    Understanding the chemical ingredients that make up toothpaste can have both positive and negative implications. An example of positive implication is that the knowledge can aid your decision making the next time you needs to purchase a new tube of toothpaste. Knowing that fluoride is the most important chemical in toothpaste, reading the ingredient list of the toothpaste can help you decide which brand is most beneficial to your dental health. Toothpaste ingredients can also have negative implications as well, especially regarding its temporary effects on your taste. I, for one, experienced the unpleasant taste of orange juice after brushing my teeth. It has been theorized, but not confirmed, that the sodium lauryl sulphate, the detergent chemical found in most toothpastes, represses the sweet receptors and destroys phospholipids that act as inhibitors on bitter receptors. This suggests that toothpaste can affects a person’s tasting ability after brushing his or her teeth. (Clark. J, n.d.). Another negative implication regarding fluoride toothpaste is its long-term ironic consequence that can discolor and crumble your teeth caused by excessive use. In addition, a number of studies have linked, but not confirmed, that fluoride can cause as many as 10,000 cancer deaths per year, majority resulting in bone cancer. (Global Healing Center, 2002). While these implications show the negative effects of fluoride toothpaste, it does not mean that fluoride toothpaste is not equally beneficial to the body. The implications show that while fluoride toothpaste can decrease tooth decay and cavities, fluoride toothpaste should be used moderately and not excessively.

    References:

    Beach, E. (2011, June 15) What Are The Dangers Of Sodium Lauryl Sulfate in Toothpaste?. Livestrong. Retrieved April 14, 2013 from http://www.livestrong.com/article/210934-what-are-the-dangers-of-sodium-lauryl-sulfate-in-toothpaste/

    CTPA (2013) How Does Toothpaste Work?. The Cosmetic, Toiletry and Perfumery Association. Retrieved April 14, 2013 from http://www.thefactsabout.co.uk/content.asp?menuid=31&submenuid=115&pageid=115&menuname=How+does+toothpaste+work%3F&menu=sub

    Clark, J. (n.d.) Why Does Orange Juice Taste Bad After You Brush Your Teeth? How Stuff Works. Retrieved April 14, 2013 from, http://science.howstuffworks.com/life/human-biology/orange-juice-toothpaste1.htm

    Global Healing Center. (2002, July 15) Dangers of Fluoride in Toothpaste and Water. Global Healing Center. Retrieved April 14, 2013 from, http://www.globalhealingcenter.com/health-hazards-to-know-about/where-the-yellow-went

    Roberts, M., Wright, T. (2009, July) The Dynamic Process of Demineralization and Remineralization. Dimensions of Dental Hygiene. Retrieved April 14, 2013 from, http://www.dimensionsofdentalhygiene.com/ddhright.aspx?id=5380

    Vankervich, P. (2011, February 16) How Does Fluoride Strengthen Teeth And Why Add it to the Public Water Supply? Tufts Now. Retrieved April 14, 2013 from, http://now.tufts.edu/articles/fluoride-teeth-public-water-supply

    WebMD. (n.d.) Weighing Your Toothpaste Options. WebMD. Retrieved April 14, 2013, from http://www.webmd.com/oral-health/guide/weighing-your-toothpaste-options

    Wikipedia. (n.d.) Abrasive. Wikipedia. Retrieved April 14, 2013 from
    http://en.wikipedia.org/wiki/Abrasive

    Wikipedia. (n.d.) Toothpaste. Wikipedia. Retrieved April 14, 2013 from http://en.wikipedia.org/wiki/Toothpaste

    Images:

    Demineralization-Demineralization Process [Image] (2009) Retrieved from, http://www.dimensionsofdentalhygiene.com/ddhright.aspx?id=5380

    The Demineralization of teeth When Sucrose Turns into Acid, Which Sequesters Hydroxy Apatite. [Image] (2011) Retrieved from, http://kquinto.livejournal.com/1794.html

    Toothpaste Ingredients [Image] (2012) Retrieved from, http://www.volunteerorganic.com/2012/03/20/recommended-dental-care/

  2. As another student plagued with the blessing of corrective braces, my dentist also warned me of the dangers of plaque and how to keep it at bay with proper brushing and flossing. Although I haven’t had a cavity since getting braces, I remember when I first had them put on, my dentist gave me very specific instructions on not only how to brush, but also what to eat and how. She told me that although I needed to brush, floss, and use a fluoride containing mouthwash to maintain the health of my gums and teeth, I also wasn’t allowed to eat or drink certain foods such as coffee, tea, dark berries, and other teeth staining foods. As I read Angela’s post, I recalled my dentist’s warning not to eat staining substances in order to maintain the uniform color of my teeth when the braces were removed. Currently, my dentist has informed me that I will be relieved of my braces in a little more than a month, however, during the time I had (have) my braces, I still drank some tea and certainly ate several berries. Therefore, worried that my teeth have stained, I decided to look into how teeth stains are removed.

    Image 1: Extrinsically Stained Teeth
    http://www.prestige-dental-care.com.my/blog/wp-content/uploads/2011/02/chlorhexidine-staining.jpg

    Image 2: Intrinsically Stained Teeth
    http://www.prestige-dental-care.com.my/blog/oral-surgery-oral-pathology-oral-medicine/teeth-discolouration.html

    There are two kinds of teeth staining, extrinsic and intrinsic. Extrinsic staining occurs when the colored particles and chromogens of food become attached to the surface of your enamel (A Closer Look at Teeth Whitening and Types of Teeth Stains – REMBRANDT®, n.d.). Contrary to how the surface of your teeth may feel when you touch and brush them, the surface of enamel, which is composed largely of hydroxyapatite crystals arranged in hexagonal tubes, is riddled with pits, ridges, and microscopic tubules that can hold chromogens – chemical substances that can be converted into pigments or dyes (Freeman, n.d.). When the pigments found in food bond to the chromogens (similar with how a ligand can bond to a metal ion and create a visible spectrum of color) the chromogens can then attach and become lodged in the rough surface of the enamel. Because extrinsic staining occurs when colored foods “stain” or coat the surface of the enamel, they tend to build up near tooth cracks, in between the teeth, and along the gums, however, they can be removed relatively easily. Good brushing techniques, proper flossing, and if needed, a trip to the dentist to polish and scrub off the particles can remove the extrinsic stain build up (Tooth Discoloration – Common Causes of Tooth Discoloration, n.d.).

    Image 3: Tooth Diagram
    http://img.webmd.com/dtmcms/live/webmd/consumer_assets/site_images/articles/image_article_collections/anatomy_pages/tooth2.jpg

    Intrinsic staining occurs when the dentin – the material inside the tooth that creates the yellow tinge of teeth as well as protects the pulp of the tooth where the nerve endings are – becomes stained or when the white enamel thins (Watson, n.d.). With age and wear, the enamel that covers the dentin becomes thinner and the dentin’s natural, yellow to brown color, becomes more apparent; this gives rise to the “stained” appearance of the (Watson, n.d.). People are often told to avoid staining foods and drinks because of their staining properties, such as the tannin in tea and the color of red wine; however, the acidity of a food can also “stain” the teeth by thinning the layer of enamel (Freeman, n.d.). In the case of red wine, although it has a dark staining color, is also very acidic with a pH of approximately 3.5-3.7. Due to this acidity, the enamel wears down and exposes the yellow color of the dentin beneath it, therefore “staining” the teeth (Pandell, n.d.) by eroding the enamel and making it easier for chromogens to gain access to the dentin and attach to the enamel.

    However, when the dentin is stained (intrinsic staining) particles of pigmented chromogens from food pass through the crystal microtubules in the enamel to the dentin. Dentin, although stronger than bone, is composed of a matrix of mineral and calcium ions; within this matrix, there exist several tubules and holes making the dentin quite porous (What is Dentin?, n.d.). As such, when the chromogens and pigmented food particles pass through the enamel layer, they can bond to the ions within the dentin layer. This results in a darker color of dentin that cannot be removed through mere scrubbing and polishing (What is Dentin?, n.d.).

    Image 4: Tooth Enamel
    http://www.webmd.com/oral-health/healthy-teeth-10/slideshow-sensitive-teeth-causes

    To remove the stains in the dentin, carbamide peroxide (CH6N2O3) and hydrogen peroxide (H2O2) (Gordon, n.d.) are generally used in concentrations ranging from 15-35% to bleach the dentin. When you get your teeth whitened, or bleached, at the dentist’s they will use a mold of your teeth to make a tray for the peroxide gel, and clean the surface of your teeth with pumice. Then, when your teeth have been cleaned, they cover your gums with a protective coating, place the peroxide gel in the tray and place the tray on your teeth. They then leave the tray on for 5-20 minutes before removing the tray and rinsing the mouth. This process is known as bleaching as the peroxide enters through the hydroxyapatite tubes of the enamel and into the dentin. The peroxide then reacts with the mineral and calcium ions in the dentin in an oxidation reaction (Gordon, n.d.); this both removes some of the staining particles, and changes the bonds in the staining chromogens from double to single bonds and results in a whiter color (Watson, n.d.).

    Image 5: Structure of Carbamide Peroxide (both molecules) and Hydrogen Peroxide
    http://upload.wikimedia.org/wikipedia/commons/thumb/e/ec/Carbamide_peroxide.png/200px-Carbamide_peroxide.png

    However, when the teeth are bleached with peroxide, it widens the tubules in the enamel and leaves it open to more staining. After being whitened, the teeth can regain their yellow staining due to the increased accessibility for chromogens and colored food particles to both the enamel and dentin. With frequent whitening, teeth will become yellow faster as the enamel is worn down and the tubules expanded (Maxted, 2011). Also, because the teeth are bleached via oxidation reactions within the mineral matrix with the calcium ions, the chemical structure of the teeth changes therefore making the teeth weaker and more prone to tooth decay. After excessive teeth bleaching, teeth not only become more prone to decay and crumbling, but the enamel wears down and leaves teeth more susceptible to further staining at an increased rate. The increased diameter of the tubules in the enamel can create teeth sensitivity due to the increased exposure the weakened dentin has and make eating hot or cold foods painful for users. During the treatment, the peroxide gel can also irritate and even burn gums if left for too long (Pray, 2010).

    Prior to reading about how teeth are whitened, I was prepared to try various bleaching strips and gel kits in order to obtain a “perfect smile” after my braces are removed. However, after reading how teeth are bleached and how the chemical structure of the dentin teeth is altered and used in oxidation reactions, I am less willing to intrinsically whiten my teeth. I used to think that whitening teeth had little impact on the health of the mouth and teeth, however, I found that the risks can outweigh the benefits as the very stains you can try to remove, can return even more quickly after whitening them (Maxted, 2011). In my case, my teeth and gums are both healthy and relatively white, therefore, rather than risk permanent dentin damage as well as weakened enamel (mine is already very thin), I will simply leave my dentin intact and healthy. In the future though, I will try to avoid eating foods with acidic and staining properties in order to help my teeth last longer and continue to be cavity free. Rather than intrinsically bleach my teeth, I will try the common baking soda toothpaste remedy to help buff off some of the extrinsic staining on my teeth (as I’m sure some has built up near the difficult to reach places around my braces) (Teeth Whitening: 8 Home Remedies, n.d.). In the long run, the health of my teeth and gums is more important than whether or not they are pearly white.

    Image 6: Healthy Teeth
    http://www.prevention.com/pvnstatic-assets/images/298x232_article_size/beauty/298x232_LB_teeth_grtwhit_ST.jpg

    References
    A Closer Look at Teeth Whitening and Types of Teeth Stains – REMBRANDT® . (n.d.). REMBRANDT® | Whitening that’s fast and lasts. Retrieved April 21, 2013, from http://www.rembrandt.com/teeth-whitening

    Freeman, D. (n.d.). Foods and Habits That Stain Your Teeth. WebMD – Better information. Better health.. Retrieved April 20, 2013, from http://www.webmd.com/oral-health/features/foods-stain-teeth-feature

    Gordon, J. (n.d.). HowStuffWorks “How Tooth Whitening Works”. HowStuffWorks “Science”. Retrieved April 21, 2013, from http://science.howstuffworks.com/innovation/everyday-innovations/tooth-whitening1.htm

    How Does Coffee Stain Teeth?. (n.d.). Colgate: Toothpaste & Toothbrushes | Products for Oral and Dental Health. Retrieved April 21, 2013, from http://www.colgate.com/app/CP/US/EN/OC/Information/Articles/ColgateNewandNow/Personal/2013/February/article/SW-281474979067209.cvsp

    Maxted, A. (2011, March 17). The dark side of white teeth: DIY whiteners can be dangerously addictive, cause chemical burns and leave teeth yellower than before Read more: http://www.dailymail.co.uk/health/article-1366290/The-dark-white-teeth-DIY-whiteners-dangerously-addictive.html.

    Pandell, A. J. (n.d.). The Acidity of Wine. http://www.wineperspective.com. Retrieved April 21, 2013, from http://www.wineperspective.com/the_acidity_of_wine.htm

    Pray, S. (2010, November 17). USPharmacist.com > Tooth Whitening Products for Home Use. USPharmacist.com . Retrieved April 23, 2013, from http://www.uspharmacist.com/content/d/consult_your_pharmacist/c/23852

    Teeth Whitening: 8 Home Remedies. (n.d.). Breaking News and Opinion on The Huffington Post. Retrieved April 25, 2013, from http://www.huffingtonpost.com/2011/01/20/teeth-whitening-8-home-remedies-for-whiter-teeth-_n_811178.html

    Tooth Discolorization – Common Causes of Tooth Discolorization. (n.d.). Colgate: Toothpaste & Toothbrushes | Products for Oral and Dental Health. Retrieved April 20, 2013, from http://www.colgate.com/app/CP/US/EN/OC/Information/Articles/Oral-and-Dental-Health-Basics/Common-Concerns/Tooth-Discoloration/article/Tooth-Discoloration.cvsp

    Watson, S. (n.d.). Dentin – Definition of Dentin. Dental Care – All About Dentistry and Dental Care from About.com. Retrieved April 21, 2013, from http://dentistry.about.com/od/termsanddefinitions/g/dentin.htm

    What Is Dentin? . (n.d.). wiseGEEK: clear answers for common questions. Retrieved April 20, 2013, from http://www.wisegeek.com/what-is-dentin.htm

    Images:
    Extrinsic Causes [Image] (n.d.) Retrieved from,
    http://www.prestige-dental-care.com.my/blog/wp-content/uploads/2011/02/chlorhexidine-staining.jpg

    Intrinsic Causes [Image] (n.d.) Retrieved from,
    http://www.prestige-dental-care.com.my/blog/oral-surgery-oral-pathology-oral-medicine/teeth-discolouration.html

    Image Collection: Human Anatomy [Image] (2009) Retrieved from,
    http://img.webmd.com/dtmcms/live/webmd/consumer_assets/site_images/articles/image_article_collections/anatomy_pages/tooth2.jpg

    What Causes Tooth Sensitivity? [Image] (November 15, 2011) Retrieved from,
    http://www.webmd.com/oral-health/healthy-teeth-10/slideshow-sensitive-teeth-causes

    Carbamide Peroxide Chemical Structure [Image] (n.d.) Retrieved from,
    http://upload.wikimedia.org/wikipedia/commons/thumb/e/ec/Carbamide_peroxide.png/200px-Carbamide_peroxide.png

    Healthy Teeth [Image] (n.d.) Retrieved from,
    http://www.prevention.com/pvnstatic-assets/images/298x232_article_size/beauty/298x232_LB_teeth_grtwhit_ST.jpg

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