I’ve found out the following things:
- Fluoride is hard to get in small quantities and/or as a consumer
- The type of fluoride matters
- Soluble calcium in the formulation reacts with fluoride to give insoluble calcium fluoride, making it less effective unless you don’t rinse and drink anything for several hours after
If I want the best fluoride action, I should get soluble sodium fluoride, and I should not use calcium compounds as the abrasive. This is why the toothpaste tablets I buy from the store have cellulose and silicate instead of calcium carbonate, I think.
I could spend €20 to get 100 grams of sodium fluoride which would last me a lifetime, but I’d prefer to not have so much of a toxic compound in a drawer so I’m continuing to look for smaller quantities.
Cellulose (microcrystalline cellulose, MCC, E460): this is also less abrasive than most other most other toothpaste binders. I can’t find a good source for buying it yet.
Sources for what ingredients to use: this study, this site
Mild abrasives
- Calcium carbonate – makes fluoride less effective
- Sodium bicarbonate – more of a filler, not abrasive enough on its own
- Magnesium carbonate – also makes fluoride less effective, but magnesium fluoride is slightly more soluble
- Dehydrated silica gels – too hard/abrasive (Mohs 7 vs enamel’s 5)
- Silicates – too hard/abrasive
- Hydrated aluminium oxides – I don’t want aluminium, also way too hard (Mohs 9)
- Phosphate salts, e.g. dicalcium phosphate dihydrate (DCPD), insoluble sodium metaphosphate (IMP), sodium hexametaphosphate. Having a hard time finding any of these
Thickening agents
- Mineral colloids, e.g. clay
- Seaweed colloids e.g. carrageenan
- Natural gums
- Xylitol
- Cellulose gum; Carboxymethyl cellulose (CMC)
- Hydroxyethylcellulose (HEC)?
- Xanthan gum
- Synthetic cellulose
- Microcrystalline cellulose (MCC)?
Other stuff:
- Surfactant: SDS, SLS (anionic, don’t want), sodium cocoyl glutamate (anionic), cocamidopropyl betaine (amphoteric), lauryl glucoside (nonionic), coco glucoside (nonionic). Nonionic is mildest on salivary pellicles
- Fluoride: I want sodium fluoride or sodium monofluorophosphate (MFP)
- Zinc (zinc chloride 47.98%, zinc citrate 22.77%, zinc acetate 35.64%, zinc gluconate 13.29%): inhibits plaque formation, prevents halitosis. Allowed up to 1%, although there was a proposal to lower this to 0.1% for toothpaste but in this study 1% was deemed to be perfectly safe. I’m finding it difficult to find any food safe soluble zinc powder as a consumer though. Perhaps zinc oxide (80.35%) works ok? Colgate uses it
I’ve decided that calcium carbonate base would still be the easiest, even if it makes the fluoride less effective. Many toothpaste products still combine these two.
Total formulation:
- 50% calcium carbonate – 500 g makes 2.0 kg for €6.88
- 20% sodium bicarbonate – 454 g makes 2.3 kg for €1.70
- 25% xylitol – 300 g makes 1.2 kg for €4.99
- 2% coco glucoside – 250 mL makes 12 kg for €4.75
- 1.5% coco betaine – 250 mL makes 16 kg for €4.45
- 1.2% zinc oxide – 100 g makes 8.3 kg for €4.55
- 0.3% sodium fluoride – 100 g makes 33 kg for €21.12
- up to 0.25% essential oils to taste
plus water, approx. 20%
With each tablet being about 0.3 to 0.5 g, this set of ingredients would make me about 3000 tablets for €48.44 (€0.016 each), compared to about €0.042 each at the store. Including the €5.99 silicone mould the break even point for 1 person is about 2 years worth of toothpaste tablets (~1500).
The surfactants I only need very little of, and I’m already buying them for other products, so I guess the total cost for this project is a little lower. The zinc oxide and sodium fluoride I will have way too much of, but the calcium carbonate, sodium bicarbonate and xylitol are easy to get more of so if I really wanted to I could make 20,000 tablets for around €100 (€0.005 each) which would last me about 27 years.