Next time you get your teeth cleaned at the dentist, which you should be doing every 6 months or so, ask them to give you a fluoride treatment. They literally just brush this minty sweet stuff onto your teeth and let it sit for 5 or 10 minutes.
The fluoride will leech into your teeth and help reinforce any weak spots to decrease the likelihood of developing cavities.
I mean, if you're a conspiracy theorist then in theory it will calcify your third eye as well, but I have no way of verifying that claim, or even proving that the third eye exists other than the pineal gland in your brain, and I've never heard of anyone's pineal gland being calcified.