Gandalf,
You are correct! The decay is caused from 'dry mouth' which can be a side effect of opiates! I have seen a lot of it. The decay rate is slower and usually not as severe as the problems caused from Meth use...we call it "Meth Mouth", but decay caused from opiate use is definately a problem too! ( I have been a Dental Hygienist for 25 years).-Hope