If you are missing teeth, dental implants are the best option for replacing them.
Dental implants consist of a root form, that is surgically implanted in the jawbone, and then a crown is attached to that root form. The crown is the visible part of the tooth. As such, they mimic the root and crown of a natural tooth.
Other options for tooth replacement:
A dental bridge
A removable partial denture
Or, when all the teeth are missing, a complete denture.
However, when teeth are missing, the body begins to resorb the bone that used to support those teeth. Minerals from that bone are used elsewhere in the body. If this process is allowed to progress for ten or twenty years, it results in facial collapse. Dental implants prevent facial collapse.