System for implementing a method for monitoring the positioning of the teeth of a patient, the patient corresponding to any person for whom said method is implemented in order to monitor the teeth, said system being configured to implement the method comprising the following steps: a) production of a digital three-dimensional reference model of the arches of the patient, or "initial reference model" and, for each tooth, definition, from the initial reference model, of a digital three-dimensional reference model of said tooth, or "tooth model"; b) acquisition, by using a retractor, of at least one two-dimensional image of said arches, called "updated image", in real acquisition conditions; c) analysis of each updated image and production, for each updated image, of an updated map relating to a discriminating piece of information, the discriminating piece of information being chosen from the group composed of contour information, colour information, density information, distance information, brightness information, saturation information, information on reflections and combinations of such information; d) optionally, determination, for each updated image, of rough virtual acquisition conditions approximating said real acquisition conditions; e) searching, for each updated image, for a final reference model corresponding to the positioning of the teeth upon the acquisition of the updated image, and f) for each tooth model, comparison of the positioning of said tooth model in the initial reference model and in the final reference model, in order to determine the displacement of the teeth between the steps a) and b), the initial reference model supplying information on the positioning of the teeth with an error less than 1/10 mm, the system comprising a 3D scanner for the implementation of the step a), a mobile phone for the acquisition of the step b), and a computer for the implementation of the subsequent steps. a) production of a digital three-dimensional reference model of the arches of the patient, or "initial reference model" and, for each tooth, definition, from the initial reference model, of a digital three-dimensional reference model of said tooth, or "tooth model"; b) acquisition, by using a retractor, of at least one two-dimensional image of said arches, called "updated image", in real acquisition conditions; c) analysis of each updated image and production, for each updated image, of an updated map relating to a discriminating piece of information, the discriminating piece of information being chosen from the group composed of contour information, colour information, density information, distance information, brightness information, saturation information, information on reflections and combinations of such information; d) optionally, determination, for each updated image, of rough virtual acquisition conditions approximating said real acquisition conditions; e) searching, for each updated image, for a final reference model corresponding to the positioning of the teeth upon the acquisition of the updated image, and f) for each tooth model, comparison of the positioning of said tooth model in the initial reference model and in the final reference model, in order to determine the displacement of the teeth between the steps a) and b), <EOS>