Baking soda can whiten your teeth by removing extrinsic surface stains from the enamel since it is mildly abrasive but it can't oxidize intrinsic tooth stains.
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Baking soda whitens teeth by removing extrinsic stains
According to the Journal of the American Dental Association, there are two types of teeth staining, extrinsic and intrinsic stains. The former is removed by mechanically abrading away the stains such as with using toothpastes. The latter is removed by a chemical reaction that oxidizes the stain using a type of peroxide.
Plain baking soda does not contain any hydrogen peroxide within it so the method that it uses to whiten teeth is via mechanical abrasion. This means that the inherent abrasiveness of baking soda (sodium bicarbonate) is what gives it the ability to remove extrinsic stains.
A study showed that baking soda, charcoal toothpaste, and strawberries produced a statistical difference in tooth shade. So yes they will whiten your teeth.
What are extrinsic stains?
Just so that we are crystal clear, the mechanical abrasiveness can only remove extrinsic stains. These are stains that are covering the external surfaces of the enamel and are not the ones that deeply embedded within the tooth.
Individuals who commonly get extrinsic stains are those who drink a lot of coffee or tea. Those two drinks are notorious for leaving stains on teeth. These people tend to develop a lot of brown and black dots all over the surfaces of their enamel.
The only way to get rid of these extrinsic stains is by mechanically abrading them away. Your toothpaste with baking soda does have the capability to do this. Therefore they are effective in whitening your teeth by getting rid of these external stains. It is for this reason that they are considered a whitening toothpaste.
However, there are times where these stains build up too much and your toothpaste becomes ineffective against it. When this happens you will need to get a professional dental cleaning in order to remove them.
Baking soda will not remove intrinsic stains
Baking soda may be effective in removing extrinsic stains, what it will not do is remove the intrinsic stains. That is due to the fact that it lacks hydrogen peroxide within its formulation, especially plain baking soda.
It is the hydrogen peroxide which can diffuse through the tooth to oxidize all of the organic structures. The intrinsic stains are all embedded deep within the organic matrices of the tooth. You can't remove it by mechanically abrading it because it needs to be chemically oxidized.
What are intrinsic stains?
When we talk about intrinsic stains, we mean the ones that are NOT on the surface but rather deeply embedded within the tooth. Stains like these are more similar to wine stains.
In fact, the situation is similar to a white t-shirt getting a wine stain on it. You can scrub it all you want by hand with soap but you can only remove whatever is on the external surface of it. At the end of the day, it will still have that wine stain on it since it is deeply embedded within the fabric.
The only way to get it white again is to bleach the shirt with some type of peroxide product. The peroxide will oxidize the intrinsic stain within the t-shirt to get it white again. The same exact situation happens with your teeth. If you're trying to whiten your teeth when you have intrinsic stains, it won't whiten. This is the case for those who brush everyday but their teeth are still yellow.
Despite it not being able to remove intrinsic stains due to the lack of peroxide, there are exceptions. For instance, there are many toothpastes which have a combination of baking soda and hydrogen peroxide mixed together.
Brands of toothpaste that have baking soda with peroxide:
Colgate baking soda with peroxide
Arm & hammer advanced whitening
Toothpastes that utilize peroxide within their formulation are able to add in the additional characteristic of being able to oxidize the intrinsic stains. This of course gives them an edge in whitening your teeth over the plain baking soda formulations.
Manufacturers know that a lot of people have been utilizing do it yourself remedies such as adding the hydrogen peroxide to their baking soda to make it more effective. Well, they just made your life easier since they put it all together and now you no longer have to mix it. The great part is that it doesn't even cost more than the regular toothpaste.
How long does it take for it to whiten your teeth?
Unfortunately we were unable to find any studies documenting how long it took for plain baking soda to whiten your teeth. Most of the studies with it had some hydrogen peroxide mixed within its formulation to make it more effective.
This just goes to prove that using a product with peroxide is not only superior but also more effective. After all, the addition of peroxide gives it the ability to get rid of extrinsic and intrinsic stains.
Now without further ado, a study in the Journal of Clinical Dentistry tested the effectiveness of baking soda with a 1% hydrogen peroxide in whitening teeth. What they found was that after EIGHT HOURS of treatment, they noticed a significant decrease in yellowness and an increase in whiteness of the tooth.
A second study from the same journal compared the whitening effects of arm & hammer dental care extra whitening vs Crest. The former was a baking soda peroxide formulation while the latter was not.
The results were that the baking soda was much better at removing extrinsic stains.
After two weeks, the difference in whitening was significantly different. The arm and hammer was superior to the crest.
What do all of these studies mean?
To summarize, the whitening from the toothpastes don't happen overnight. The first study said it took a total treatment time of 8 hours to see results and we only brush for about two minutes twice a day so it would take at least a couple of days to see results.
The second study found a difference in whiteness after about two weeks of usage. Once again that implies that it does not happen immediately. Overall, you should expect the baking soda peroxide formulated toothpaste to take at least two weeks for you to see results.
This is actually supported by a study by the British Dental Journal which found that lower concentrations of hydrogen peroxide took LONGER to whiten teeth than a more concentrated one. That means professional products produced results faster than OTC ones.
How long will the whitening last?
The whitening results from using a toothpaste with baking soda and hydrogen peroxide should be maintained indefinitely. The reason we say that is because you're using it every single day without stopping. There is no reason for it to stop whitening since you're continually using it.
According this study which tested how long the teeth whitening lasted with a 3% hydrogen peroxide solution, they found that it was still maintained after six months. This was with a two week treatment with no additional sessions.
If two weeks of treatment can last for six months, daily use of a toothpaste with it should theoretically not lose its effectiveness.
Is the abrasiveness of baking soda safe to use?
Since the way baking soda whitens by utilizing its abrasive characteristic, you may be wondering if it is safe to use on your enamel. We would have to say that it is totally safe to use baking soda to whiten your teeth because it's abrasiveness is actually very mild.
When compared to other types of toothpastes, plain baking soda actually has one of the lowest abrasiveness. The only dentifrice that is less abrasive than it is plain water.
What we're trying to say is that you'd definitely be safe using baking soda on your teeth. If you wanted reassurance, the ADA also explicitly states that it has low abrasivity, which provides a healthy margin of safety for your enamel. Even if the patient brushes aggressively with it, it is still considered less harmful than all the other types of toothpastes.
Baking soda really can whiten your teeth because it is mildly abrasive so it removes extrinsic stains. In fact, its extrinsic stain removal capabilities are superior to non-sodium bicarbonate counterparts. Despite having an abrasiveness to it, it is still safe to use since it is actually one of the lowest abrasiveness toothpastes on the market.
Last but not least you should keep in mind that a pure baking soda formulation will only get rid of the external stains and not the internal ones. In order to get rid of the latter you will need a formulation which includes peroxide. Only hydrogen peroxide or a derivative of it can oxidize the intrinsic stains.
Fortunately for you, most of the baking soda toothpastes do come in versions that contain peroxide. Our recommendation for maximum whitening effectiveness would be to choose one with peroxide!