Fridy,
You may be able to get some help from the Healthshare site that Kiwi offered. To make it easier to navigate, I am giving you the actual link to the dental question section.
What is the success rate of dental implants?
| Healthshare
In my opinion it would behoove you to be very careful about who you consult regarding your dental case because your situation does NOT in any way, shape or form fall into the uncomplicated dental implant category where the success rate is 80-90%. Your situation being that the teeth needing replacement were extracted 20 years ago presents a HUGE complication all in of itself. It is important to be cautious or guarded with any dentist who tries to sell you on a high success rate regarding the placement of dental implants in that area of your mouth.
I did not skim through the whole dental question section just the first page. Based on what I read there, the two dentists on that page that I think "may" offer you some straightforward information are:
Dr Keith Hengpoonthana
Dr Jeremy Rourke
Please keep us posted on how things are going.