Diet soda is either on the same level of harm as seltzer, or is worse.
What's wrong with seltzer?
What's wrong with seltzer?
I wonder what is the pH of glass of carbonated water with a squeeze of lime?
Remember that I mentioned moderation though? A glass or two of OJ, lemonade, tea, coffee, or seltzer a day isn’t going to materially impact your health assuming you’re not diabetic, and practice good oral hygiene. There are also many worse things for your teeth than seltzer, such as potato chips, and poor oral hygiene. If most of what you’re drinking is water, don’t sweat the glass or two of something other than water. Unfortunately too many poeple drink very little unadulterated water, and it does impact their health.
Moderation is the key.
('Notable cases' include recorded death.)
That said, the amount of ways your body adapts to osmotic balance problems is in the dozens, so poisoning your body with water, while possible, is hard to the tune of it requires something like drinking 20 liters of water in less than an hour. I mean, it seems to be possible but I cannot imagine succeeding at that even if I'm trying. That's 2 full buckets (and that's just LD50, as in, if you're >70kg it's more than that).
There is an exception: purified water. You cannot drink mineral-poor* or distillated water safely in even small quantities. Why not ? Because that will locally, suddenly and very strongly disrupt the osmotic balance in what you bring it into contact with. It probably not kill you (not without repeated application), but it may cause serious issues in your mouth, throat and stomach. It should also not be used to make coffee or tea and drunk, that merely lessens the effect it doesn't stop it.
* mineral-poor water is something used in chemical and medical laboratories
Acidity of most beverages on its own is usually not problematic as saliva (buffered at 6.5 pH) rapidly restores normal pH. It does become an issue if the salivary glands are damaged (as in the case of meth users) or stomach acid comes into contact with teeth.(severe acid reflux or bulimia) However these cannot be considered normal.
The number one cause of dental cavities is always sugar.
So no, there is a rebuilding process, but the kind of damage done by acidic substances (including the excretions of bacteria) can sometimes be reversed to some extent. The trend is usually erosion however, and moderate intake of something like seltzer or soda is at least an order of magnitude less than straight water. In addition, while water toxicity is a thing, you’d have to overcome a pretty strong urge to vomit. Short of that, water is doing you no harm, and will never contribute to the erosion of your dental enamel.
A number of toothpaste brands in Japan claims to remineralise teeth with a hydroxyapatite based formula but the results are yet to be confirmed.
Dentists have been using zinc oxide gels and other material to seal exposed dentin but the results are mixed and eventually the filling will fail. Once cavities reach a certain size not much can be done about it.
My kids have no cavities / perfect teeth. My wife and I, by that age range, had tons of cavities.
More acidic than: water milk tea ice tea beer
About that same as: coffee (coffee with milk, however, is essentially not acidic) wine (depends a bit on the kind of wine, sweet wine is less acidic) orange juice (from sweet oranges, the sour ones are usually less acidic)
Less acidic than: lemon juice (coke is a LOT less acidic than lemon juice)* grape juice (esp. when adding lemon juice for more sweetener) lime juice things like "lemon ice tea" (and of course actual tea with lemon in it. It depends on how much lemon. If you add enough lemon to allow for much additional sweetness, it will be a lot more acidic than carbonated beverages)
With fruit things can vary. Apparently the rule is, the sweeter, the more acidic (the opposite of what your tastebuds will tell you, although it's really more a case of if you taste sweetness you ignore sourness. Sweet taste doesn't necessarily mean something is acidic, obviously, but (from a certain level) it does mean you won't notice at all whether something is acidic or not, or how much).
If you're worried about this, even a small sip of milk will eliminate any acidity in your mouth in seconds (milliseconds actually).
* I've heard of medical cases where people managed to dissolve their stomach lining by drinking pure lemon juice (about 1.5 liter), and died due to the stomach juices coming into the abdominal cavity. Yes, that's right, your stomach lining, specifically designed to be able to handle strong acidity, cannot deal with lemon juice.