In combination, an overdenture retention implant and an installation apparatus for installing the implant, wherein the implant comprises: - an elongate, externally threaded implant body to be screwed into a hole formed in a jawbone, the body having a central axis; and - an implant end structure at a proximal end (12.1) of the implant body, the implant end structure including a tool engagement portion (14.1) and a threaded boss (14.2) to be engaged in threaded manner by an overdenture retention cap configured for attachment thereto of an overdenture, wherein the tool engagement portion (14.1) and the boss (14.2) have a common, central axis which intersects the central axis of the implant body at an acute angle to that central axis, and wherein the installation apparatus comprises: - a fixture mount having a hollow first end defining a fixture mount socket shaped to engage in rotationally fast manner with the tool engagement portion of the implant end structure of the implant for the purposes of rotating the implant to screw the body into the hole in the jawbone and an opposite second end engagable in rotationally fast manner by a rotation tool which can be manipulated to rotate the fixture mount and hence an implant engaged thereby; and - an anchoring device for releasably anchoring the fixture mount in engagement with the implant, with the central axis of the implant body aligned and coaxial with a central axis of the fixture mount, while the fixture mount and implant are rotated; characterized in that: - the fixture mount socket has a central axis inclined relative to the central axis of the fixture mount by an angle which is the same as the angle by which the implant end structure is inclined relative to the central axis of the implant body; - a mouth of the fixture mount socket lies in a plane normal to the central axis of the fixture mount socket; and - the fixture mount socket includes an internal shoulder and the anchoring device comprises a cap which has a threaded cap socket for threaded engagement with the boss (14.2) of the implant end structure of the implant, a mouth of the cap socket being arranged to abut the internal shoulder of the fixture mount socket when the cap socket is threaded onto the boss, thereby to anchor the fixture mount in engagement with the tool engagement portion of the implant end structure of the implant. - an elongate, externally threaded implant body to be screwed into a hole formed in a jawbone, the body having a central axis; and - an implant end structure at a proximal end (12.1) of the implant body, the implant end structure including a tool engagement portion (14.1) and a threaded boss (14.2) to be engaged in threaded manner by an overdenture retention cap configured for attachment thereto of an overdenture, - a fixture mount having a hollow first end defining a fixture mount socket shaped to engage in rotationally fast manner with the tool engagement portion of the implant end structure of the implant for the purposes of rotating the implant to screw the body into the hole in the jawbone and an opposite second end engagable in rotationally fast manner by a rotation tool which can be manipulated to rotate the fixture mount and hence an implant engaged thereby; and - an anchoring device for releasably anchoring the fixture mount in engagement with the implant, with the central axis of the implant body aligned and coaxial with a central axis of the fixture mount, while the fixture mount and implant are rotated; - the fixture mount socket has a central axis inclined relative to the central axis of the fixture mount by an angle which is the same as the angle by which the implant end structure is inclined relative to the central axis of the implant body; - a mouth of the fixture mount socket lies in a plane normal to the central axis of the fixture mount socket; and - the fixture mount socket includes an internal shoulder and the anchoring device comprises a cap which has a threaded cap socket for threaded engagement with the boss (14.2) of the implant end structure of the implant, a mouth of the cap socket being arranged to abut the internal shoulder of the fixture mount socket when the cap socket is threaded onto the boss, thereby to anchor the fixture mount in engagement with the tool engagement portion of the implant end structure of the implant.