I have a full upper denture. My problem is the front teeth on the denture appear to be smaller than the back or side teeth. When I smile, you don't see the front teeth at all, you just see the back or side teeth. Can the denture be repaired, or will I have to get a new upper denture?

You should be able to have the teeth replaced on the denture depending on the age of it.
If the denture is a number of years old you would be better off to have a new one made.