Loss of vertical support for the denture (bone loss) can cause the mouth to "over-close". This can change the way the lips seal together and cause saliva to pool at the corners of the mouth. The excess moisture in this area may cause the skin to become irritated and may increase the risk of a candida (fungus) infection. The soreness may also be the result of a vitamin deficiency.
Wrinkles above/around lips or corners of mouth;
Denture has moved back in the mouth and no longer supports the lips. This may be due to bone loss and/or loss of skin elasticity and moisture loss.