If you have been struggling with cavities, it’s because of the combination of in short your genetics, your mouth hygiene, and your diet. What causes cavities is not directly sugar but the cavity forming bacteria S. mutans, that feeds on the sugar, acidifies your mouth thus demineralizing the teeth (dissolving them). They also form the unaesthetic and gum-harming plaque, and create glues to stick to the teeth. When you understand how cavities are formed, you understand why mouthwash exists, and why it is extremely important in the fight against cavities. Virtually regardless of diet and genetics, adding mouth hygiene by using an effective mouthwash can bring the vast army of S. mutans to a near eradication and prevent further plaque and cavities. But which mouthwash? Well two things: I hate the taste of conventional mouthwash, I don’t fancy putting in my mouth broad antiseptics, and I’m always happier when I don’t rely on “cosmetic” products, so this white tea/green tea mouthwash really got my attention. But does it really work?
Dr. Michael Greger’s website has a wonderful video called “What’s the Best Mouthwash“. In this video, he compiled scientific evidence to compare the efficacy and safety of different mouthwash solutions, commercial or homemade.
The wining solutions used green tea, and immediately it raises the usual questions: How to make it? How to use it? Are there risks (like staining teeth)? Can I use white tea instead? None these questions were addressed, making such interesting information poorly actionable. So I decided to look into the literature cited and beyond, to get some answers and hopefully convert the scientific talk into something people can easily make at home, whether health-conscious, frugal, or in places of the world with limited resources.
For those in a hurry who already decided they would go for it:
Recipe and instructions for a 0.5%green tea mouthwash :
Put 5 grams of green tea (or white tea) in 1 liter of room-temperature water, let sit 1 hour and strain. Rinse with 15mL for 30 seconds and spit. Do this after brushing your teeth or before/after a meal. WARNING: Because of the natural variation in the content of active ingredients found in tea leaves, refer to section 6) to know how to test your batch and make sure it will actually work.
Cost: ~5cts for a 500mL bottle = 2 week supply. You can’t beat that!
Based on 250g of loose green tea at about US$5 in a Chinese shop, and assuming your tea is as potent as in the study.
1) Let’s re-cap
Different studies used green tea extract, one showing how green tea helps keep a high oral pH, lowers (cavity causing) S. mutans population and reduces oral bleeding. Another study showed how green tea dramatically reduces plaque accumulation, improves gingival index, and improves salivary pH. In the former study, oral pH remained above 6 (mildly acidic) without green tea, but plummeted below 5 without (relatively very acidic). In the latter study, mean plaque score goes from 1.45 to a ridiculously low 0.11, indicating a 94% reduction in plaque. You can read more here about plaque assessments, it’s interesting.
2) Figuring out a recipe and instructions
The first study was done one a single-shot basis (not over a long period of time) and people swished 10 ml, of a 2% green tea solution that people swished for 5 minutes . The sucrose solution (in your case: the meal) was taken 20 minutes after the end of swishing. Unfortunately, they mention nothing about how that “2% solution” is prepared.
The second study was done over 3 weeks. They used a 0.5% green tea solution. “The subjects were instructed to brush twice daily” and “15 ml of mouth was rinsed for 30 s after each brushing” . Unfortunately, how they prepared their green tea solution is confusing and imprecise.
When I looked into the recipe they used, I was disappointed to find a rather complicated way of explaining something simple, and they had used an ehow.com recipe: “Tea was extracted by combining 3 1/2 oz. (about 7 tablespoon) of green tea with 4 cups of still (not sparkling) mineral water. The tea was steeped at room temperature for 1 h and then poured in to the lidded container, straining the tea with sieve as it is poured followed by refrigeration. The loose tea is discarded. The 500 ml concentrated tea is mixed with 1000 ml of distilled water to get 0.5% solution of tea mouthwash”.
It doesn’t say of the water was boiled or not, so by default we’re going to assume it was not, and that it doesn’t matter whether is blended or not. There are chances all these factors make some difference in the extract content.
Nothing says where that “0.5%” figure came from, and everything about their recipe is misleading. Is it fluid ounces (volume) or weight ounces? Is the water boiled or not? 4 cups doesn’t give 500mL so why did they say “The 500mL concentrated tea” instead of just “500 mL of the concentrated”, did they use the official cup measurement or not? Ah…those moments when you wish the metric system was more popular than the Kardashians.
Anyway, I solved this ambiguity though another study about green tea  not mentioned in the video. That study says “As in previous studies (9), the concentration used during brewing was 2 g of tea leaves per 100 ml of hot water (2%, wt/vol)”. The percentage is in weight per volume. Problem solved.
3) Should you add amla or indian gooseberry?
You can, but the study on amla  used a solvent extract of amla, not a water extract. So it’s fair to wonder what is the active ingredient? is it water extractable? if so would it work? and if it interacts with green or white tea. More research reading needed there.
4) “Green teath” and the white tea alternative
Some people asked in the comments of the video if it’s possible to use white tea instead to prevent stains. White tea is the young leaf of green tea basically. First of all, do the stains happen if one swishes with cold tea or could it be the hot tea? Is it in people who drink sweetened green tea, or green tea alone? The concern for stains can only be in our heads until we get evidence that green tea swishing – not drinking – stains the teeth. There are two ways to answer the question about white tea: 1) Understand why green tea works and see if white tea has a similar same composition in that regard 2) Confirm that white tea works, for instance by doing something as simple as a pH test using paper pH testers at home, like they did in . I looked into the literature to get a feel of what is responsible for effect of green tea for oral health. That was done very fast and needs more in-depth work. This being said, it seems that it’s the catechins and especially EGCG that are at play. Does white tea have that? Yes, but it’s also a bit different : “White and green teas contain similar levels of EGCG but differ in the relative amounts of other polyphenols and caffeine” . This suggests white tea extract is likely to work as a mouthwash too, with the same recipe. If it doesn’t work as well that might be because of the difference composition, or just because of the greater general variation in the content of active ingredients between batches…
5) The problem of variations and how to hack it
You’re not using the same batch as in the study so the same expression “green tea” in practice can be a very different product each time.
We can be very obsessed about precise numbers in an effort to practice good science. All that precision becomes irrelevant when you start taking into account variations. In nature, the content of any compound in living things varies tremendously. That’s how selenium in a single Brazil nut can go from almost nothing to 20 times the RDI (Recommended Daily Intake). In my past work on growing methods for crops (where health begins) I came across a study showing a 10-fold difference in vitamins and minerals depending only on growing practices. Then the studies like that on Brazil nuts confirm that the composition of the soil have a profound impact on the composition and nutrient density of foods. Then you have freshness, storage, processing , distributors mixing batches from different locations, cooking/extraction technique. All this put together results in a very wide range of minerals, vitamins, and other compounds in any living things and food. Always take the nutritional values with a truckload of salt. In the case of tea specifically : “Total catechin content (TCC) for white teas ranged widely from 14.40 to 369.60 mg/g of dry plant material for water extracts […] TCC for green teas also ranged more than 10-fold” . In one of the studies  or  the authors state very clearly that other groups carrying out similar studies failed to find an improvement in oral health due to green tea. Content variation should be the number one suspect for inconsistencies in results from studies using extracts that are not titrated for their content of active ingredients.So how to hack this variation?
For practical reasons, a pH test of saliva is the best way to know if a green tea extract is potent enough or not. Paper tests can do the job, you want a pH test mostly sensitive for pH in the range the [4.5 to 6] and keep a pH above 6 when following the protocol of the study  that I summed up in paragraph 2 of this article. I’m sure there’s even a way to do this pH test with very low-tech means at home without even having to buy paper strip pH tests.
It’s tricky though, because this will work the first time, and if you’re consistent with green tea mouthwash, the pH test will not give you an acidic saliva reading and you’d find yourself confused. Why? There seems to be an increased benefit of green tea mouthwash overtime as described on the pH results in , very likely because of a gradual eradication of the acid-forming bacteria S. mutans overtime (a single wash cuts S. mutans population in about half in both saliva and plaque ). This means you’d have to test your new batches either by using a guinea pig (homo sapiens) that doesn’t use green tea, or by not using your mouthwash for a while, re-allowing your bad bacteria to develop and be able to score you a low pH again of you weer to have a sweet drink. For practical reasons I would go for the latter even if I don’t like the idea of allowing the bacteria population to grow again. So I don’t have to do that too often I would make large concentrated batches I can keep in the fridge. This would assure that I have a lot of a good batch saved whenever I make one.
1) This article is purely based on a literature review. It provides a prediction of what is expected to be the best method to sustainably achieve with low-tech means a green/white tea extract that is reliably potent. Experiments with the above method are needed to confirm or disprove what I described. The results are of interest to me, so do share in the comments what the results are for you or if you have a question.
2) The could be a possibility of the bacteria S. mutans adapting to the active ingredient in green or whit, rendering the mouthwash useless. Only long-term experimentation will tell.
 Int J Dent Hygiene 9, 2011; 110–116 DOI: 10.1111/j.1601-5037.2009.00440.x, “A pilot study of the role of green tea use on oral health”, Awadalla HI, Ragab MH, Bassuoni MW, Fayed MT, Abbas MO.
 Indian Journal of Dental Research, 24(1), 2013, ” Comparison of the effectiveness of 0.5% tea, 2% neem and 0.2% chlorhexidine mouthwashes on oral health: A randomized control trial“, Aswini Y Balappanavar, Varun Sardana1, Malkeet Singh
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 Unachukwu, U. J., Ahmed, S., Kavalier, A., Lyles, J. T. and Kennelly, E. J. (2010), White and Green Teas (Camellia sinensis var. sinensis): Variation in Phenolic, Methylxanthine, and Antioxidant Profiles. Journal of Food Science, 75: C541–C548. doi: 10.1111/j.1750-3841.2010.01705.
 Hasan S, Danishuddin M, Adil M, Singh K, Verma PK, et al. (2012) Efficacy of E. officinalis on the Cariogenic Properties of Streptococcus mutans: A Novel and Alternative Approach to Suppress Quorum-Sensing Mechanism. PLoS ONE 7(7): e40319. doi:10.1371/journal.pone.0040319