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Letter to the editor

Editor, I refer to Professor Reynolds' excellent review of the safety implications of toothpaste ingredients (Aust Prescr 1994;17:49-51).

Probably the agents most likely to cause an allergic reaction are methyl and propyl parahydroxybenzoates, which seem to be the most commonly used preservatives in toothpastes available in Australia. As far as I am aware, SensodyneF (regular and gel) and the entire Aim and Colgate ranges are free of any preservative.

Professor Reynolds' discussion of the potential hazards of ingestion of silicareminds me that, not only are siliceous earths used as abrasives, but also that hydrated silica (silica gel), colloidal anhydrous silica and aluminium magnesium silicate are often used as thickening/binding agents. A few toothpastes are silica free, including Macleans Regular Mint, OralB Dental Paste, Colgate Fluoriguard (regular and cool mint only), Ultrabrite and Dentagard.

The use of gum arabic (gum acacia), gum tragacanth and Indian tragacanth (karaya) as binders/thickeners is less common nowadays due to a possibility of sensitization reactions. Carrageenan gum (which incidentally is identical to Irish Moss extract), guar gum, xanthan gum, silica compounds and cellulose derivatives seem to be the most commonly used.

The only sorbitol free toothpaste that I can trace is Macleans Smokers Toothpaste! Of course, sorbitol is not the only potential laxative in toothpastes since several of the thickening/binding agents may exert this effect if swallowed in sufficient quantity.

Toothpastes containing 0.3% triclosan, as a plaque inhibiting antibacterial, are currently readily available (e.g. Colgate Total and the Aim range).

T.E. Bridges
Senior Lecturer in Pharmacology
Department of Dentistry
University of Adelaide
Adelaide, S.A.


Author's comments

Professor E.C. Reynolds, the author of the article, comments:
In my article I stated that occasionally the flavours, colourings or preservatives of toothpastes can cause allergic reactions. My reference1,and also another2, state that the flavourings are the most common allergens. In one case where the preservatives as well as the flavourings were involved, only the preservative chloroacetamide was an allergen, even though the preservatives also included benzoates.

After consideration of a large number of studies, it was concluded in the review that silica containing toothpastes are safe and effective.

The FAO/WHO has recommended sorbitol intake to be less than 150mg/kg/day. Fora 10 kg child, this is equivalent to 1.5 g of sorbitol per day, and for a 70%sorbitolcontaining children's toothpaste, this would be equivalent to 2.1 gof toothpaste ingested per day, a quantity that could easily be achieved byun supervised brushing. Binders are 1-2% of the toothpaste. Therefore, to ingest the same quantity of binder, the child would have to ingest 100-200g (1-2 tubes)of toothpaste.

The reason why triclosan was included as an antimicrobial toothpaste ingredient in my review was because it is an active ingredient in Colgate's Total which is available in Australia. Triclosan is only an ingredient in the Aim Gum Health variant which does not have wide distribution in Australia relative to the standard Aim. The point I was making in my review was that triclosan containing pastes are not available in the U.S.A. The Food and Drug Administration would not allow triclosan to be marketed as an antimicrobial toothpaste additive until its efficacy and safety had been established.

T.E. Bridges

Senior Lecturer in Pharmacology, Department of Dentistry, University of Adelaide, Adelaide, S.A.

Eric C. Reynolds

Associate Professor and Reader, School of Dental Science, University of Melbourne, Melbourne