What happens to my new dentures after recent extractions ?

There will be substantial bone absorption and gum shrinkage around the extractions and this will continue to happen for  approx. 12 months or more before it slows down.
You will likely require to have ongoing adjustments and possibly temporary linings done in order to improve the fit and comfort of your denture(s).
When the bone absorption has slowed  you will then need a permanent lining placed into the denture(s).