I had an infection in a crown on a lower molar, the gum at the side used to get a sort of spot, which I'd pop every couple of days and yellow grunge would come out. Sounds gross, I know. My dentist talked about dentures and implants and tried to talk me into the implant, but the quote was £2300, which I thought was crazy. He mentioned about bone loss etc. Not sure why, but I didn't fancy the denture.
Anyhow, this went on for five years (yes, five). It did get progressively worse (soreness and the tooth got more wobbly) so a couple of years ago, after a change of dentist, I had it pulled out. It came out really easily and almost immediately I felt generally better.
I haven't had anything put in to replace, can't really see the point.