I have been taking opiods for approx 2 years for TOS and RSD. My dentist has found that the opiods make my mouth really dry, and that has caused a great deal of the decay. He says he finds that fairly often with chronic pain patients, and with people who have Sjorgrens. He tells me you need to salivate freely, but the medication can reduce the amount of saliva produced, and as a result it is more difficult for you to "wash" the bacteria off of your teeth.
His suggestion to me was to brush after every meal, and drink LOTS of water.
Hope that helps.
Trix