Complete dentures should be replaced approximately every 10 years. Over time your gums and bone change shape, causing dentures to become ill-fitting. When this happens you may be prone to mouth infections, and have pain and irritation due to your dentures rubbing. As denture teeth wear down you may find eating becomes more difficult, and you may get pain in your jaw joint, among other negative occurences. Your appearance and speech can also be greatly affected by poorly fitting and worn teeth.
Partial dentures may need to be replaced more often, depending on other changes to the natural dentition.