A retainer cooperating with a plurality of teeth and configured to stabilize the plurality of teeth, the retainer including at least one elongated arc which is shaped overall adapted to a natural curvature of a lower jaw or an upper jaw, wherein the at least one elongated arc is locally adapted individually to a surface contour of respective abutting teeth, wherein the retainer is machined from a sheet metal plate and includes two mutually parallel surfaces, wherein the sheet metal plate is made from a nickel titanium alloy, preferably a nitinol, wherein the retainer contacts a tooth surface in an installed condition of the retainer, wherein a machined surface of the retainer faces the tooth surface in the installed condition of the retainer, and wherein an upper side or a lower side of the retainer corresponds to an original surface plane of the sheet metal plate.