Within 6 months of starting to wear a denture, you will have already lost about 40% of your jawbone structure.
If you have worn a denture for a few years, you already know about bone loss. The reason your denture doesn't fit like a year ago, is that you don't have the same jawbone structure to support it.
If you wear a partial denture, beware that you will have the same problem with bone loss.
Once the jaw bone structure is lost your options become limited. A dental implant is the logical choice to help stop bone loss, however, once the jaw bone structure is lost, your options become limited.