A prosthesis with fixed teeth applied over four implants is a  relatively simple, painless and uncomplicated treatment process, with a short surgery. The four implants are inserted into the jaw, and the prosthesis is screwed to the implants, making it fixed and stable. 

This is the most economical solution that allows you to re-establish your complete dentition without having to resort to numerous dental implants and prolonged interventions and recoveries.
From the age of majority, there is no age limit to undergo this type of treatment, 

A well-kept prosthesis, barring the appearance of disease, can last a lifetime, if hygienic care and regular maintenance are ensured.