Polyacrylic acid (PAA) as a toothpaste ingredient is primarily used as a bioadhesive and as a vehicle for delivering other ingredients. It doesn't exert any direct effects but what it does is enhance the effects of other ingredients.
As for its safety, it is typically considered to be non-toxic since it is highly biocompatible and will degrade on its own.
Polyacrylic acid in toothpaste overview:
Description: Acrylic acid polymer; White fluffy powder when dried.
Benefits: Bioadhesive and ingredient delivery to teeth.
Side effects: Non-toxic, biocompatible, biodegradable; But high doses may cause GI irritation & Neurotoxicity.
Antagonists: Chlorhexidine gluconate.
What is polyacrylic acid?
Polyacrylic acid (PAA) is a polymer of acrylic acid and it often goes by its trade name, Carbomer. When it is dried, its appearance is that of a white fluffy powder.
Do you know where it can be commonly found? Disposable diapers.
That white powder inside of diapers which soak up bodily fluids and make the diaper expand is all due to PAA. Yes, it is primarily used as an absorbent in diapers because it absorbs water well and swells up in size afterwards. The amazing thing about it is that it can absorb up to 100x its weight in water.
Other uses:
Absorbent.
Paints and cosmetics.
Pharmacology - drug delivery.
Oral care products - remineralization and dentin conditioner.
In dentistry, GC makes a cavity conditioner which uses 20% PAA. It is used to clean and condition the dentin prior to placing the bonding material. In other words, it is already a commonly used dental ingredient.
Its benefits in toothpaste
The two main benefits of having polyacrylic acid in toothpaste is for its bioadhesive properties and its ability to deliver other ingredients to the tooth surface.
Bioadhesive
Polyacrylic acid is a bioadhesive/mucoadhesive with very good adhesion properties to various bodily structures. It is able to adhere to these surfaces and remain there for an extended period of time.
What PAA can adhere to:
Mucosal surfaces.
Skin.
Bone.
Teeth.
The benefit of having a bioadhesive like PAA in toothpaste is that it can increase the contact and working time for toothpaste ingredients. This will enhance/amplify their effects thus increasing their efficacy.
Potential enhanced effects:
Remineralization. Fluoride and hydroxyapatite based toothpastes will become more effective at stopping cavities.
Desensitization. Sensitive toothpastes with it can desensitize the teeth for a longer period of time thus reducing discomfort.
Antibacterial. Zinc in toothpaste can stick around longer and reduce bad breath for more time.
Overall the bioadhesion is very similar to another dentifrice ingredient, PVM/MA copolymer which is also found in toothpastes.
Delivers other toothpaste ingredients
Polyacrylic acid can also help deliver toothpaste ingredients to the surfaces of the teeth. This means it can securely transport various ingredients to the teeth so that they don't become compromised before reaching the teeth.
Example:
Fluoride can prematurely interact with calcium in the saliva to form calcium-fluoride, thus reducing its bioavailability.
This reduces the amount of free fluoride ions that can be used to strengthen the tooth enamel hydroxyapatite to fluorapatite.
Studies have shown that PAA is an acceptable carrier for fluoride ions.
In summary, use of a bioadhesive like PAA can safely and securely deliver the fluoride or various ingredients to the teeth. This helps to maximize the effects of these ingredients to be used for the teeth.
As further evidence, there are plenty of studies which have documented the use of PAA for delivery of hydrophobic drugs in the body. Yes, it can be used for more than just the mouth.
Side effects
Polyacrylic acid is generally considered to be a non-toxic substance because it is very biocompatible and also biodegradable. It can be degraded by lysozyme.
Cytotoxicity studies also found that the cytotoxic effects were negligible. However, when PAA is ingested in very large amounts, there can be adverse effects.
Side effects from large concentrations:
Vomiting
Altered mental state
Ataxia
Tremors
Tachypnea
Overall, in the study above, dogs that consumed excessive PAA exhibited significant gastrointestinal irritation and neurotoxicity. The neurotoxicity persisted for 96 hours before recovering.
Antagonists
Polyacrylic acid (Carbomer) interferes with the antibacterial activity of chlorhexidine gluconate (CHX).
Studies have shown that when the two are used concurrently, the amount of residual CHX on the teeth after rinsing with it are significantly less. That means if you did not use a PAA toothpaste, there would be more CHX remaining in the mouth and it would have a stronger antibacterial effect.
Why that is important: Chlorhexidine is an antibacterial prescription mouthwash that derives a lot of its benefits from its substantivity. It is able to stick around in the mouth and exert its antibacterial effect for up to 12 hours.
Mechanism for reduced efficacy: PAA adheres to the teeth but CHX also has strong adherence to the teeth. My thoughts are that they both compete for adhering to the tooth surfaces.
In summary, if you're currently using CHX mouthwash, you should use a non-polyacrylic acid toothpaste until you're done with the prescription. Your dentist probably prescribed it for you because you're having a gum issue that needs resolving at the moment.
Verdict
In my opinion, polyacrylic acid is a very interesting ingredient for toothpastes because it acts as an amplifier or enhancer of other ingredients. Where it seems to be used is for boosting remineralization and desensitization effects.
A lot of the sensodyne toothpastes contain PAA because it helps their anti-sensitivity agents work more effectively.
Overall, due to its non-toxic nature and superb bioadhesive effects, it is an ingredient that I would consider putting in my future toothpaste. Although the PVM/MA copolymer is also a candidate but I'll need to do a comparison between those two to see which is better.
That's everything our dentists in Long island City have to say about this ingredient in toothpaste.
