What’s the Best Mouthwash?

Goal: To educate about the active ingredients in mouthwashes and to help make an informed decision in your purchase.

Motivation: I’m an indecisive person when it comes to buying products with so many varieties such as mouth washes and toothpastes. I once spent so long looking at ingredients and googling them on my phone that the store clerk asked me “you’ve been here an awful long time, are you sure you don’t need any help?”. I’ve decided to lay out what I’ve learned so that I can help those other indecisive folks some time.

Oral health can be broken down into a few primary targets:

  • Reduction of bacteria in, on, and in between teeth and gums: Bacteria in your mouth create biofilms in which they reside  to help them survive and stick around. These buildups of bacteria and secreted biofilm are more commonly known as “plaque”. Bacteria are bad because the byproducts of their metabolism/digestion is acidic. These acids break down your teeth, causing cavities and other bad things. If bacterial infection creeps into and around the gums, your body’s immune system will attack them, causing inflammation (gum diseases) and possibly tooth loss.
  • Whitening:  This may seem like a purely cosmetic concern, however appearance is nonetheless very important in social interaction and self-esteem. If a boss is constantly distracted by your brown teeth or you are self conscious about talking and showing your teeth, that can definitely have an effect on your career success and/or mental health.
  • Strengthening of teeth: Making your teeth more resistant to acid induced enamel decay should be obvious.

Now after looking through all of the fancy bottles of mouthwash and toothpastes, I noticed a couple of common themes. The active ingredients weren’t as varied as the packaging and primarily included:

  • Fluoride based chemicals
  • Hydrogen peroxide
  • Antibacterial compounds
  • Ethanol

And here is how each of them work:

Fluoride compounds:

  • Fluoride works by preventing demineralization at the surface of your teeth, it helps to remineralize teeth into a form that is more resistant to acid degradation than it was previously, and it also helps to inhibit enzymes that bacteria may use to break down things that they see as “food”.
  • It may be interesting to note that we actually secrete calcium and fluoride in our saliva. (Natural re-mineralization?) This means that fluoride is also important to have in our diets, especially in the years where we are developing our adult teeth.
  • References:
    • “Prevention and reversal of dental caries: role of low level fluoride”, John D. B. Featherstone, Community Dentistry and Oral Epidemiology, 1999, Volume 27, Issue 1, pages 31–40
    • “In vitro studies on the effects of lfuoride on de- and remineralization”, Ten Care JM, J Dent Res. 1990 Feb

Hydrogen Peroxide:

  • Hydrogen peroxide (H2O2) is used to whiten your teeth. It is used as a dilute solution (usually around 1.5% in mouthwashes). It is a highly reactive oxygen species that has a very high oxidizing capacity. It breaks down into free radicals (hydroxyl radicals) that can react with lots of other compounds and basically rip them apart. It’s interesting to note that  H2O2 is made naturally within cells as a byproduct and that cells have evolved enzymes that work at the limit of diffusion (very fast) to convert this compound into harmless water and oxygen. This makes sense because if H2O2 were to stick around for a while, it would start to rip apart the cell and mess up your DNA.
  • So you may be asking then why would we want to put this stuff in our mouths?! When it “rips things apart”, it’s basically acting like bleach. The peroxide basically enters your teeth and attack stains. The stains are usually organic materials in a non-crystalline form, so the destructive power of the free radicals would preferentially attack those compounds, destroying them and making your teeth whiter. Whitening agents may also destroy cells in your mouth, but at the low concentrations used in over the counter products combined with the fact that the cells in your mouth regenerate very quickly anyways, the risk associated with that is minimized. (But of course, moderation is key.)
  • Whitening strips usually have a hydrogen peroxide concentration between 3% and 16%, so the ~1.5% you would find in your mouthwashes are going to be much less effective. Basically, if you want to see results within days or weeks, you need to up your H2O2 concentration by using a special product that is applied for hours per day, otherwise, don’t expect to see noticeable results by getting a whitening toothpaste or mouthwash.
  • It’s not entirely marketing that whitening claims are on mouthwash or toothpastes. Some hydrogen peroxide is better than no hydrogen peroxide at whitening teeth; just don’t expect miracles.

Antibacterial compounds:

  • Since bacteria cause tooth decay and all the nasties, it makes sense that antibacterial compounds would be included in oral hygiene products. These antibiotics are usually fairly commonly used in related over the counter products like soaps. They act by killing and preventing bacteria from growing. Antibiotics in the right concentration range generally don’t have any bad effects on human cells.
  • An interesting result of using an antibacterial mouthwash can be that you may be selecting for and breeding bacteria that are resistant to the specific antibiotic used in your product. Sure, the first time you use your antibacterial mouthwash most of the bugs will die from it since they most likely don’t have the resistance to it. However, bacteria grow very fast and there are a ton of them in your mouth. There may be, for example, enzymes that are used by the cell to break down a related compound that exist in the bacteria normally. It may take only one or a few mutations to turn an existing enzyme into something that will break down your antibiotic and as soon as one of the billions of bacteria undergo that mutation, it will repopulate your mouth without any competition.
  • Basically, your antibacterial mouthwash may not be doing anything with continued use. You may be able to extend your usable lifetime of your antibacterial mouthwash by switching between products with different active ingredients. (Or swapping in an ethanol rinse every once in a while since that is almost impossible for bacteria to become resistant to).


  • Ethyl alcohol (more commonly known as “The thing that gets you drunk”) is used in many antiseptics and mouthwashes. Basically, the ethanol is capable of dissolving membranes and thus killing cells. (Your own cells included). It may be an effective way to kill bacteria since it is MUCH harder for a cell to evolve to survive without a cell membrane. There is some controversy as to whether constant killing and replenishment of your own cells via mouthwash can lead to higher cancer rates of the mouth.
  • If you’re in a rush and just want to kill everything in your mouth, perhaps ethanol mouth washes are the main game in town. However, if you just brush your teeth with toothpaste, it can act as a surfactant and loosen up bacteria very well also. Once you brush and rinse, you’ve done fairly well already at clearing out the bacteria from the unwanted places.
  • The literature at this point in time will tell your that there is no conclusive link between the two, but it makes sense simply by looking at the hayflick limit of cells. (The hayflick limit is the limit to the number of times that a cell can divide before it runs out of teleomeres.) When a cell runs out of telomeres, it either becomes senescent (stops growing, but doesn’t die) or it can result in a higher probability of the cell becoming cancerous.
  • Granted, the hayflick limit is almost never reached during a normal human lifespan and it’s a stretch to make it an argument against ethanol based mouth washes. Perhaps the amount that it kills your own cells will not be significant enough to cause any increases in cancer rates. However, it’s obvious that it can under the right conditions, even if only by this stretched logic. As I value my health above all else, I would ere on the side of caution when it comes to anything that is still in contention.

So what did I end up doing?

I wanted a mouthwash that contained a Fluoride compound since it has many upsides.

I avoided ethanol based mouth washes due to the harshness of using it and the unknown downsides  of increased oral cancer rates.

I figured that antibacterial compounds weren’t going to really help much due to eventual resistance.

I wanted a mouth wash that contained hydrogen peroxide to help whiten my teeth with little effort, but for some reason all of the “whitening” mouthwashes charged an exorbitant price! I thought that was ridiculous, considering you can buy a good 750mls of 3% hydrogen peroxide for like… a buck in the next isle over.

So basically, I bought the most basic fluoride based mouthwash without ethanol or antibiotics, and I added 3% hydrogen peroxide to it before I use it.

I found this is the cheapest way to get all the positives that mouthwashes can possibly offer.

Also! I’ve recently added a Water Pik to my arsenal. It seems that I finally got around the misconception that it was only for old people. (As the only other person I know who owns one is my mother) I’ve loaded up my recently purchased Water Pik with a diluted mouth wash solution and it seems to work very well. It seems that the water pik cleans differently from flossing, brushing, or using mouth wash. It’s able to shoot a high pressure stream of liquid between the tooth and the gums, cleaning areas that are especially difficult to reach otherwise. It felt as if I had come back from a dentist’s cleaning appointment the first time I used it. I think the combination of flossing, brushing, and using this Water Pik is a good combination for oral care.