Why is sodium hydroxide an ingredient in toothpaste in why is it only present in tiny amounts?

Answer 1

They use it to correct the toothpaste's pH. Here's the deal: When toothpaste engineers create a new toothpaste, they use all sorts of chemicals to make it, and when they're done they want a product with a slightly alkaline pH. When you brush your teeth with alkaline toothpaste, it neutralizes cavity-causing mouth acids. They're looking for a pH of somewhere around 8 or 9--alkaline enough to neutralize the cavity-causing acids; not alkaline enough to strip the skin off your tongue. Cool so far? You're a toothpaste engineer. You have created WikiAnswers toothpaste, and the first batch you made has a pH of 8.2. Now your challenge is to make every other batch have that same pH, because if you don't people won't like your toothpaste--you'll get letters saying the new tube doesn't taste like the old one, that it doesn't foam up like the old one, that it hurts your mouth, whatever. But what's the problem? The ingredients you use aren't going to be exactly the same every time. This month, the ingredients might give you a pH of 8.2, and six months from now you might get a pH of 8.1. So, to fix the pH you'll add just a little bit of sodium hydroxide. It doesn't take much--maybe 100 grams in a 1000-kilogram batch of toothpaste. And that's why they use sodium hydroxide for this--it's so strong the amount you'd need to do the job wouldn't change the consistency of the toothpaste, whereas if you used borax, a very mild alkali, you'd have to add so much of it you'd make the toothpaste stiffer.