Why Does Chlorhexidine Increase Tartar Formation?

Written & Reviewed by Dr David Chen

Rinsing with chlorhexidine mouthwash can increase tartar formation on teeth but why it happens has not been scientifically proven.

However, that doesn’t mean researchers don’t have theories to explain the increase in calculus. It also does not mean that this antibacterial rinse is bad for you because it can still be beneficial when used in the right situations.

Chlorhexidine - bathroom sink

Last but not least, the newly formed tartar is not permanent because it is removable.

Does chlorhexidine really increase calculus?

Yes, studies have shown that chlorhexidine (CHX) oral rinse can increase tartar on teeth by as much as 5 times when compared to a control. There is an increased uptake of calcium and phosphate ions into bacterial biofilm when exposed to CHX, which accelerates the calculus formation

Supporting scientific studies:

  • One study found that the CHX treated teeth had calculus on 26.19% of the surfaces vs 4.52% of the control group.
  • Another study found that there was more tooth staining and tartar formation for the experimental group using CHX.

In summary, using chlorhexidine will promote more tartar formation on your teeth than if you did not use it. The other major adverse effect would be teeth staining because CHX is notorious for producing brown discolorations on the enamel when used long term.

It’s a warning on the label

If you wanted additional evidence, look no further than what it says on the label of this prescription rinse.

Chlorhexidine rinse label - increase in tartar formation

It literally states that using this antibiotic rinse can increase tartar (calculus) on teeth. You may find this on the “what to expect when using chlorhexidine gluconate oral rinse” section.

Theory for increased tartar from chlorhexidine

The precise reason for chlorhexidine increasing tartar is unclear and not proven but there are two theories as to why it may happen.

Chlorhexidine is a positively charged compound

Chlorhexidine is a cationic compound (positively charged) which is strongly attracted to negatively charged bacterial cell surfaces. The calciums is also positively charged so it is strongly attracted to the bacterial surfaces. The combination of all three results in calculus formation.

Proposed mechanism of how it happens:

  • Due to charge differences, CHX kills all of the bacteria that are adhered onto tooth surface.
  • Dead bacteria bursts and leaves behind lipoteichoic acid which is negatively charged on the surfaces of the enamel.
  • Positively charged calcium ions are strongly attracted to the lipoteichoic acid.
  • The increased uptake of calcium results in tartar formation.

As a reminder, this is just a theory and has not yet been proven.

Chlorhexidine creates a conducive calcification oral environment

Chlorhexidine may be promoting calculus formation because it kills bacteria and brings the oral environment into a neutral pH.

Why a neutral pH encourages tartar:

  • When the mouth is in an acidic pH, teeth will demineralize meaning it loses calcium and phosphate ions.
  • However, when the mouth is in a neutral pH, the teeth will remineralize meaning it regains the lost calcium and phosphate ions.
  • Since the mouth stays in a remineralizing environment for an extended period of time while rinsing with CHX, it promotes calculus formation.

As another reminder, this is another theory and also not proven.

Is it a bad mouthwash to use?

Despite the adverse effect of calculus formation from chlorhexidine use, it is not a bad mouthwash due to two reasons.

  • The formed tartar consists of dead bacteria.
  • Helps treat a variety of periodontal conditions (periodontitis).
chlorhexidine rinse - blue colored liquid poured into cap
Chlorhexidine – Blue colored liquid

Dead bacteria in the tartar

Under normal circumstances, plaque biofilm is full of bacteria which transforms into tartar when it calcifies by taking in calcium and phosphate.

However, when the biofilm is exposed to chlorhexidine, the bacteria die but still remain on the surface of the enamel. The calculus will form over the already dead bacteria from the deposition of calcium and phosphate.

In other words, the tartar from CHX contains less bacteria than non-CHX treated tartar.

When using chlorhexidine is beneficial

The beneficial effects of CHX are undeniable because rinsing with it will reduce gum inflammation and bleeding. It is due to these properties that dentists prescribe it for various gingival conditions.

Periodontal conditions it can treat:

  • Mild gingivitis
  • Gum abscess
  • After a deep cleaning

Use of chlorhexidine typically expedites the gum healing after dental treatment has been rendered. It is often used as an adjunct to help with the aftercare and recovery.

How to remove the tartar

Fortunately, the tartar on the teeth from the chlorhexidine rinsing can be removed so it isn’t permanent. The way you remove it is no different from the regular tartar that you develop throughout the year.

How to remove the calculus:

  • Dental cleaning. A professional cleaning of the teeth will definitively remove all of the calculus on your teeth. Since you do develop 5x as much tartar while using the rinse, your cleaning appointment may take longer than usual.

There is actually no other way to remove tartar because you can’t do it without a dentist. However, there are ways to reduce and minimize the amount of it forming on your teeth.

How to prevent tartar on teeth from chlorhexidine

Good oral hygiene will go a long way to preventing and minimizing calculus.

  • Get a cleaning before starting the rinse. You should get your teeth cleaned before you begin treatment with the CHX rinsing. This way you minimize the amount of plaque and biofilm on your enamel.
  • Brush and floss prior to rinsing. If you brush and floss before you rinse, it will minimize the amount of biofilm on your teeth. That means there will be less chances for the rinse to produce tartar.


Chlorhexidine rinsing will increase tartar on teeth by as much as 5 times but why it happens is still unclear. Currently there are only theories as to how it happens because nothing has been proven.

With that being said, it is still a fantastic antibacterial mouth rinse to use and if your dentist prescribed it for you, you should use it. The total treatment time with CHX is only 2 weeks so you may get extra calculus during those two weeks.

Imagine if you had to use it for 6 months, you’d have a mouth full of calcified plaque which would be a nightmare for your dentist or hygienist. Thankfully the rinse has a short duration for usage but that is because dentists know that it causes staining and tartar build up.


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