I wouldn't give them money. I'm all for helping those who can't help themselves, but your comments about believing they could be debt free, but not knowing if they have the will to do it or not would make me hesitate to offer any further financial assitance in this situation. No one likes to see anyone suffer, especially family, but if you continue to help them in this way, you will deprive them of the dignity of being self sufficient. That is the only thing that is likely to break the cycle of financial dependency that they have come to rely upon. If there are other circumstances that prevent them from being able to help themselves, by all means spend all of your time and treasure on them. If you do it for less than that, you may be doing it for the rest of their lives.
As far as solutions, I would see if your mother's dentist offers a payment plan. I would also have them look into account opening bonuses like those found here -
$5,370 in free cash from banks for some easy cash. There are also bonuses for opening up credit cards, but with their background I don't know if they'd qualify or if it would be wise. Here' s the link in case it might be of help -
Credit Cards that offer cash bonus for applying - $1000 up for grabs
Based on my own family experience, I sympathize with you as you struggle with these often emotionally difficult decisions.