Brushing teeth on Tisha B’Av

I know that most Poskim forbid it. If my hands are dirty, then I am permitted to remove the dirt with water and soap if necessary, preferably up to the knuckles if possible.

Now that we know that our teeth are actually dirty with plaque.

From Wikipedia

Components of plaque

Plaque consists of microorganisms and extracellular matrix.
The microorganisms that form the biofilm are mainly Streptococcus mutans and anaerobes, with the composition varying by location in the mouth. Examples of such anaerobes include fusobacterium and actinobacteria.
The extracellular matrix contains proteins, long chain polysaccharides and lipids.
The microorganisms present in dental plaque are all naturally present in the oral cavity, and are normally harmless. However, failure to remove plaque by regular tooth brushing means that they are allowed to build up in a thick layer. Those microorganisms nearest the tooth surface convert to anaerobic respiration; it is in this state that they start to produce acids.
Acids released from dental plaque lead to demineralization of the adjacent tooth surface, and consequently to dental caries. Saliva is also unable to penetrate the build-up of plaque and thus cannot act to neutralize the acid produced by the bacteria and remineralize the tooth surface.
They also cause irritation of the gums around the teeth that could lead to gingivitis, periodontal disease and tooth loss.
Plaque build up can also become mineralized and form calculus (tartar).

I understand that on Yom Kippur we have an additional issue of Inuy, afflicting oneself.

ילמדינו רבינו
Why isn’t plaque considered like “dirt” that may be removed?
It could be argued that nobody, even a dog, would swallow tooth paste let alone listerine.
Why not allow brushing with a half a cupful of listerine or similar?

Author: pitputim

I've enjoyed being a computer science professor in Melbourne, Australia, as well as band leader/singer for the Schnapps Band. My high schooling was in Chabad and I continued at Yeshivat Kerem B'Yavneh in Israel and later in life at Machon L'Hora'ah, Yeshivas Halichos Olam.

15 thoughts on “Brushing teeth on Tisha B’Av”

    1. Bruce,
      Unfortunately after 120 years unless Eliyahu comes earlier to herald the new era, I know I have much much more to answer.
      That being said, thanks for your blessing!


    1. Also, what about people with Fremde Tzeyne (false teeth, you have to love Yiddish!!!)

      Can they leave them over night in steradent or whatever, dry them and put them back in? Why are Fremde different to Eyginer?


        1. Hirshel, while I’d normally defer to your superior Yiddish despite its Hungarian roots, I’m pretty sure my version is authentic.

          I asked a friend of mine a few years ago whose mother was from heilige bundist stock, and she claimed ignorance. Perhaps they would never admit to losing their teeth 🙂

          Anyway, you have to admit Fremder Tzeyn is much more delicious linguistically?


      1. Definitely not joking.

        In fact even i didnt envisage the full severity.

        During a subconscious teeth floss with a beard hair a particle was indeed swallowed and the after taste indicated that it was a bit of meat.

        So not only was food consumed,but fleishigs noch


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