Mick the hot water with lemon is the myth most discussed on the internet, but it says of course water maybe more palatable with a little lemon.
And of course the acid in the lemon can cause tooth corrosion too !
Its too late to prevent tooth decay, at 71 I do not have many teeth left
A lot of mine had root cannels and capes years ago and they then just broke off at gum level!
I will at some stage, need them all out and have false ones.
Mick.