Complete dentures replace all the teeth in a persons mouth, upper and lower (unless specified as a complete upper denture or complete lower denture) They are usually made of acrylic(plastic). They stay in place because they fit very accurately against the gums. They are not as secure as any of the previously described items and for this reason dental implants are often used to provide more grip for a denture.
Partial dentures are used where some of the teeth remain. The partial denture may rest entirely on the gums or entirely on the teeth or a combination of both. When possible it is far better to have the remaining teeth support the partial denture giving it more grip. The partial denture that is supported entirely by the gums is usually made of acrylic (plastic) and the one supported entirely or partly by the teeth has a metal framework to support the plastic (so it is stronger).
Overdentures (also see Dental Implants)
Sometimes keeping the roots of some teeth under the denture has the advantage of keeping the bone that gives the denture something to grip. (When a tooth is lost completely, the bone that was around the tooth usually disappears). Attachments such as studs (like raincoat fasteners) and magnets can be fitted to the root to add to the grip of the denture. When we keep some of the roots under the denture we call the denture an overdenture.