Very interesting question and I'm looking for answers. Now I'm using

Salvadora persica as natural tooth cleaner.

Have you considered to use eugenol or an essential oil obtained from edible/non poisonous plant species proved as antimicrobial?

I agree with Alessandro, essential oils are widely studies for their preservative effects, however, eugenol could irritate mucous membranes.

Dear Dr Benzeggouta, thanks. You have pointed out an interesting aspect.

I've suggested to use eugenol because it has been used for decades in dentistry for its antimicrobial properties and therefore it should be effective.

Concerning the irritation potential it should be considered at which dose eugenol produces this side effect. In general the quantity of preservatives used in formulation is very low (i.e 0.5%) and could be compatible with a safe use. A literature survey on these aspects could be of help.

Thanks Dr. Alessandro Venditti, eugenol is always an option for the reasons specified by Dr. Naïrouz Benzeggouta but I need some dependable component that ensures the stability for 2 years or at least 18 months. We cannot have Eugenol (or Clove Oil) beyond a certain limit else it can be harsh on oral mucosa.

Same is the case with Tea Tree Oil, Cinnamon Oil, etc. We can use them only in minute quantities that guarantee therapeutic impact but not the desired preservative like effect on the product.

Still, I would go with your recommendation Doctor and keep a test batch with 0.5% Eugenol... shall update in case it shows success and desired effect.

Dr. Naïrouz Benzeggouta it is good to return to nature and use the basic herbs, Salvadora persica or Miswak / Toothbrush Tree is indeed one of the finest herbs but as an R&D person in herbal pharmaceuticals, we look at other aspects as well pertaining to oro-dental health and hygiene.

Thanks for your response Doctors :)

Looking forward to more views on this aspect.

Hello, I am not familiar for toothpaste, but one thing to consider is the long term stability, 6 month, 12, 24 month. PET test is a must do to ensure stability. Having said that would a combination of salicylic acid/1,2 octanediol and 2 phenoxyethanol be an option?

Thanks Laurent F Bornaghi ... will check at our end.

I agree with Dr Bornaghi, a middle-long term stability test should be conducted. I would also suggest to perform the challenge test which simulate the possible contamination of the product during its normal use. However, among the cited preservatives I would suggest to avoid phenoxyethanol, even if it is already used in cosmetic field. From personal experience it is not so effective if employed at concentration below 1% and several concerns are known i.e. allergy (see link below).

I would also suggest the possible use of lactic acid and/or sorbic acid or their salts which are already used as food preservatives.

http://www.safecosmetics.org/get-the-facts/chemicals-of-concern/phenoxyethanol/

Following.