A prosthesis mounting device and assembly for securing a prosthesis on an implant supported in bone tissue. A metallic appendage or "preppable abutment" is carried by a dental implant and is milled or "prepped" into a shape suitable to accept a dental prosthetic. A recess extends axially upwardly from an axial bottom end of the appendage and is shaped to fit over an O-ring receiver abutment or "O-ball" of a dental implant.