If there is a lack of jaw bone to support the denture, your denture may need to be adjusted to get them to fit better and remove any spots that may be causing pain. I would recommend that you go back to your dentist to have the area evaluated again.
Your dentist may also suggest using fixodent or some other type of denture adhesive to try to help hold the denture in place.
Another possibility is the placement of dental implants which are titanium "screws" that are placed in the jaw to help retain the denture with little snap-on attachments. This helps hold the denture in place.
Lower full denture is a bad news...If the dentures were inserted at the same time as the extractions...the way bone heals is over the period of first 4-6 weeks the initial bone healing takes place when the extraction sockets heal and gum grows over to close those gaps....the bone changes but the denture stays the same therefore at this time(i.e after 6 weeks) you need some thing called a soft reline to accomodate the lost bone. Over period of six month u continue to loose the bone at slower rate. After six months either you should make a new denture or get a hard reline for it to fit better.
If the teeth are missing for a very long time..you might not have enough bone in the lowers...in that case implants are the best solution. Four mini implants spread over the anterior jaw bone...dentures get the housing and keeps the denture in place like a ball and socket joint.
Adhesives a are also available in the market but are not suppose to be permanent solution. In my experince fixodent powder is better easy to apply and more hygenic. Hope it helps!!