they come with (or used to come with) sugar in the pouches, and sugar feeds bacteria that cause caries so it's not just receding your gumline, it's feeding the bacteria that destroy your teeth also (and now they're getting at the root of the teeth under the gumline) which is why people complain about it affecting their teeth. but let's be real, it's not gonna be much different from a can of coke every day. it's not good, you shouldn't do it, but you're not going to have your teeth fall out after 5 months, either.
Canada