Most commonly, a lower denture is supported with two to four implants underneath it. The more implants you have the more stable the denture is.
If I gave you a stool with two legs, could your sit on it? Yes you could! It would take some balance on your part, but you could sit on it. An overdenture with two implants, works like that. The denture is held in very strongly, but it can still move in the back.
In a two-implant overdenture, the implants are purposely placed in the front part of the jaw.
If you added a third leg to the stool, would that make it more stable?
Of course! Especially if the three legs were equally spaced away form each other.
The average denture has fourteen teeth on it. So the more implants, the better. Four implants are the best option for stability. It is a four-legged stool. The implants make the overdenture even more stable when a bar connects all the implants. This “splints” them together and creates strength in numbers.
Even two or three implants and be splinted together with a bar for added stability.
Five or more implants in the lower jaw is usually strong enough to replace the denture all together! Meaning the teeth would no longer come out. They can be fixed in place.
The upper jaw generally requires six implants to have a non-removable fixed bridge.
The basic theme is: the more stability you want, then the more implants are needed. Also, the more bone you have missing, requires more implants to be stable over time and avoid bone loss on the new implants.
This concept is sometimes confusing. Please comment below if you have a question!
Ramsey A. Amin, D.D.S.
Diplomate of the American Board of Oral Implantology /Implant Dentistry