It is a lot easier to blame the methadone for rotten, brittle, frail teeth then to take responsibility for why your teeth are REALLY bad. If someone tells me that they were busy brushing and flossing their teeth while in active addiction, I am not going to say they are lying, but they sure aren't telling the tooth! lol
Most of us that have been in recovery for a goodly amount of time realize the value of honesty and how crucial it is. Dishonesty/the inability to be honest with ourselves and/or others will keep us sick/in danger of relapse. I know how painful it is to come to terms with how much we hurt others and ourselves while in active addiction, but if one is to have some semblance of peace/recovery/growth it must be done.
Some folks are going to blame the methadone, no matter what. To do any less would mean that they actually have responsibility for the state of their oral hygiene.
If I actually believed methadone was rotting my teeth I would look to other options quick, fast, and in a hurry.
It bears noting that not even one scientific study to date has been published that shows that methadone rots teeth.