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Why do we brush our teeth with toothpaste? Why do we floss our teeth? What is the role of a mouthwash other than making your breath smell better? These are all questions that we all think about at one point or another in our lives if we in fact are inquisitive about things that we learn to do or are told to do in order to take care of ourselves.

When we eat sugar and carbs, plaque starts forming which is a physical mix of food, bacteria (those that are in our mouths) and their byproducts. And the byproduct of that is acid that gets formed. That acid then starts dissolving the surface of our teeth that is composed of hydroxyapatite (HA) which is called demineralization of the surface. Our bodies in turn try to remineralize the surface in an effort to keep the surface of the teeth protective of what is inside it (dentin and pulp which is the blood supply and the nerve endings); that process, the remineralization usually utilizes calcium and phosphate that is present in our saliva. And this process is assisted with fluoride (from toothpaste/water/mouthwash). There is usually a balance or equilibrium that is present, like a lot of other reactions in nature, that keeps things in a steady state. There are also elements that could shift this equilibrium towards remineralization or demineralization; meaning that teeth surfaces can become stronger or weaker respectively.

So with eating carbs/sugars, the pH in the mouth becomes acidic, and with that, the equilibrium shifts towards more demineralization, resulting in losing minerals off the surfaces of the teeth more than remineralization; this is how “cavities form”. Once that starts happening, this chemical reaction becomes more and more difficult to halt and control; this means that the decay/cavity on the tooth becomes deeper as it harbors more bacteria physically, the environment becomes more acidic, and further demineralization takes place in the site. That is why when a decay starts showing itself, ideally one wants to have it addressed ASAP. Addressing it could take different levels of effort and treatment depending on the extent and location.

The idea behind using toothpastes is to not only clean the surface of the teeth off of food by mechanical debridement with a toothbrush, but also to treat the surface to be resistant to accumulation of plaque and bacteria & their subsequent acidic byproducts; that would mean subsequently reducing the chance of decalcification (or decay formation) on tooth surfaces. This is the main reason for using toothpastes. Furthermore, in many cases, we want to reduce the sensitivity of the teeth by using toothpastes, while many of us want to whiten the surfaces of the teeth to have a whiter brighter smile; these are also several functions that a toothpaste can help with.

So toothpastes can be good in reducing plaque formation, removing the plaque, increasing the pH of the mouth, reducing the amount of bacteria in the mouth, remineralizing the surfaces of the teeth by reinforcing them with minerals, reducing sensitivity, removing stains and whitening the surfaces by either physically whitening them or changing the optics of the surfaces of the teeth. And there are a few different types of materials known to us at this point that can help with achieving some or all of these objectives for toothpastes. And there are many schools of thought that would be supportive or opposing the effect of these materials/products as well just as with any other materials these days.

The only anti-decay/anti-caries substance recognized by the FDA (Food & Drug Administration) in the US is fluoride. And that is recognized in 3 forms/compounds: sodium monofluorophosphate, sodium fluoride, and stannous fluoride.

Fluoride’s effect on teeth was based on an observation in early 1900’s in Colorado, but it took until 1940’s for the NIH to formally look into it. Fluoride from drinking water/toothpaste/mouthwash adsorbs (attaches) to the surface of the teeth and prevents demineralization & dissolution of that surface. This adsorption also attracts calcium and phosphates onto the surface and increases their concentration and moves them back into the tooth surface. Fluoride also disrupts bacterial activity by crossing the bacterial cell walls in the form of HF, an acid, & then releasing fluoride which disrupts their metabolism and subsequently kills them. Fluorapatite that is formed on the surface of the teeth has increased stability, reduced solubility and increased hardness relative to the natural tooth surface. So fluoride increases remineralization, and reduces the effective bacteria present on site, along with creating a harder surface.

There are other substances that have been used that have been proven and yet not verified/approved by the FDA yet for this purpose. One of the main widely recognized and utilized substances is hydroxyapatite which as stated above is the building block of our teeth.

Hydroxyapatite (HA), a type of calcium phosphate, that is over 95% of our enamel and 70% of our bones. Interestingly enough, NASA used this biomimetic (meaning that it mimics the biology of our bodies) material in the 1970’s in order to help the astronauts rebuild their enamel and teeth. It was the Japanese, Sangi Co LTD, that subsequently bought that patent and started testing it in Japan on people during the 80’s and 90’s. In 2003 they developed the first nano size HA (nHA) in toothpastes.

Both Fluoride and HA can rebuild the tooth structure; the biggest difference is that HA is the same as what is already in our teeth in terms of components and it is biomimetic as stated, hence non-toxic. HA can make the teeth look whiter as well since it fills in the surface imperfections without any whitening agent that is.

There are some toothpastes that have nano size particles of HA while there are others with micro size particles. The nano sized ones are synthetic while the micro sized ones are not; and the micro ones are closer to the size of the small tubules that are making up the dentin of our teeth (the 2nd inner layer of our teeth).

HA creates a more homogeneous remineralized surface compared to fluoride and at a deeper level. So in that respect, HA has an advantage over FL. HA gets absorbed into the tooth though and rebuilds the surfaces from inside out. For that reason alone, it can remineralize surface caries better than fluoride. This is while fluoride, when used in a toothpaste, rebuilds the surfaces of teeth by making a new component called fluorapatite; it also signals for more calcium and phosphate uptake to strengthen the teeth surface. So the mechanism of action is different between FL and HA when you get into it. HA furthermore, absorbs into the bacterial cell walls and helps them stick together, thus removing the plaque on the teeth to be much easier. Also if there is fluoride in the mouth (eg. from water that is drunk), it can still bind to the HA and create fluorapatite which is quite resistant to acid attack.

The concentration of HA that has shown to be effective in remineralizing the surface the same as fluoride has shown to be needing to be 10% or more. The challenge though has been to have a way of keeping the HA on the teeth for long enough to be fully used and absorbed by the teeth surface; historically, that has meant advising the consumer that the toothpaste should not be rinsed with water after, and ideally not eating/drinking for 20-30 minutes post use. To keep the HA on the tooth surface, several proteins have been tested. vVardis in Switzerland has developed a fascinating combination of Self- Assembling Peptide Matrix (SAPM) and HA, where the SAPM stays on the teeth surface temporarily, allowing HA to get absorbed much better than without it. While doing that, the new surface that is added changes the light reflection off of the surface, creating an optical effect of a whiter surace. The effect from that, after a week of application lasts for 30 days.

Another factor that can shift the demineralization-remineralization equation is the pH of the environment as pointed out. The pH needs to be more neutral for HA to be effective in remineralizing a surface compared to the pH needed for Fluoride to do the same (5.5 for HA vs 4.5 for FA). So, toothpastes or products in general that ensure that, are more successful in delivering the full effect of the remineralization that is desired.

As for desensitization, there are a few different substances that could be helpful when used in toothpaste such as potassium nitrate and 8% argening/calcium carbonate; SAPM is also shown to help with that as well as ozone in certain instances.Casein Phosphopeptide can also help with reducing sensitivity by creating a source of calcium and phosphate on the surfaces that it is applied to, and remineralizing the surface; sometimes fluoride is added to that formulation as well to create a stronger more resisting surface. SAPM has furthermore been shown to be quite effective in reducing sensitivity in teeth just as much as 8% argening/calcium carbonate which is used on some toothpastes to address sensitivity.

Whitening effect in toothpastes is achieved by either removing stains and revealing a surface that is free of those or alternatively actually whitening the surface by changing its enamel shade (via the use of peroxide, whether hydrogen or carbamide peroxide). There is now a third alternative where the surface is “filled in” more and therefore reflects light differently than otherwise and is therefore seen as whiter. Toothpastes with abrasives buff the surface away from stains but won’t whiten the enamel there on; the abrasive agent usually could be silica, baking soda, or dicalcium phosphate. If one wants whiter teeth that are achieved with those toothpastes, then we have to look into toothpastes with peroxide which is the whitening agent in them. The bleaching toothpaste essentially has peroxide in it which is a strong oxidizer; it removes the stains on the surface of the teeth but also penetrates mildly onto the surfaces with time and removes some of the stains that are below the surface (by lending a free O atom that can bind with stains and break them apart). This can create some sensitivity though for some people. If a deeper white shade is desired for the teeth, then teeth whitening, with methods other than just toothpaste usage should be considered.

A very different class of materials that has been utilized in making toothpastes has been anything that would reduce the amount of bacteria present in the mouth. Ozone is an oxidizing material used since the early 1900’s that can help in this sense. It has antibacterial properties. Ozone, whose chemical formula is O3, wants to become O2 (the stable oxygen molecule), giving out a free O radical. That makes for a quick oxidation of bacteria in the site where it is present. So, ozonated toothpastes reduce decay by affecting the amount of bacteria present in the vicinity of teeth surfaces primarily. They are not directly creating a harder surface. They are indirectly affecting remineralization by shifting the pH in the mouth and making it less acidic by controlling the amount of bacteria. This is assuming that the individual has enough calcium, phosphate and fluoride to go through remineralization of the surfaces usually.

Now that we have gone over toothpastes, let’s look at mouthwashes. They are geared towards reducing the bacterial load in the mouth primarily; this is quite important when someone has a surgery for example or a deep cleaning. But changing the type of bacteria present in the mouth long term may not be ideal. We do need bacteria in our mouths just as we do in the rest of our bodies. Certain types are harmful but many are needed. So certain types of mouthwashes are to be used for short periods of time only. There are many that can be used long term though. The biggest consideration that has come to light has been to ensure that they don’t have any alcohol in them as to not dry out the soft tissue in the mouth; and also to preferably use mouthwashes with neutral pH. Interestingly, most of the mouthwashes in the market are quite acidic which does not help with remineralization of the teeth surfaces; in fact, works against it as stated many times. There are some mouthwashes that have been manufactured recently that are paying attention to this fact, and neutralize the pH of the mouth which is great.

Flossing is primarily geared towards removing the debris from in between the teeth which is where bristles of the toothbrush can’t physically get to. Those are also areas where food typically gets packed into when we are chewing. So cleaning them physically is quite important to not have demineralization happen in between the teeth, but also to ensure that the gum that is in between the teeth stays healthy and not inflamed due to extensive bacteria that are seeking the otherwise impacted food particles there. There are some flosses that are also trying to remineralize the surfaces that they come in contact with; and they try to do that with either having fluoride or HA recently.

Finding a toothpaste or mouthwash that has fluoride and/or HA and is also cognisant of the pH of the mouth of the user is quite important to be able to get the full benefit of using the product and incorporating it into one’s daily oral hygiene routine.

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