The invention concerns a device (1) for editing a virtual 3-D model (2) of teeth (2.1, 2.2, 2.3, 2.4) positioned in a dental arch (9, 11) by means of a virtual tool (21, 22, 23, 24, 25, 26, 27, 28, 50). The tool (21, 22, 23, 24, 25, 26, 27, 28, 50) can be used on a first tooth (2.1, 2.3) of the 3-D model (2), whereby the corresponding application is carried out on a second mirrored tooth (2.2, 2.4), contralateral to the first tooth with respect to a plane of symmetry (12), that is, on the tooth on the other side of the plane of symmetry (12), which is positioned as a mirror image of the first tooth (2.1, 2.3) with respect to the plane of symmetry (12).