A method of determining an optimal switchover moment for a hybrid orthodontic treatment of teeth. Creation of a digital three-dimensional model of at least part of a dental arch. Deformation of the initial reference model until the tooth models are in a target position. Acquisition of at least one two-dimensional image of the teeth. Deformation of the initial reference model until the at least one updated image corresponds to the initial reference model. Determination, from the updated reference model and from said target reference model, of a plurality of remaining-treatments for moving the teeth from their position represented in the updated reference model into their position represented in the target reference model. Determination of a profile including at least one value for an evaluation parameter. Evaluation of each profile by an evaluation rule. Determination the profile of which is optimal for replacing an orthodontic appliance with an aligner.