A patient's dentition is analysed to determine an orthodontic treatment plan by simulating an intervention in advance. 3D imaging techniques and computer technology are used to simulate and predict tooth movement as a function of the chosen treatment, i.e. a specific orthodontic appliance. In this way treatment options can be compared and the most optimal (shortest treatment time, lowest forces . . . ) treatment for each individual patient can be selected. Sub-steps of the tooth movement are not predefined but computed based on a simulation of orthodontic elements and wire as they would be used in the orthodontic treatment of the patient. This means that the sub-steps are calculated based on the relationship between the applied loads and the tooth movement; only one of both parameters can be chosen freely. Thus, either the tooth load is specified and applied in order to calculate the resulting tooth movement or vice versa the tooth movement is specified and applied in order to calculate the tooth load that should be applied. Moreover, the current invention allows predicting the time at which brackets and / or archwire should be changed, and comparing different treatment options with respect to tooth loading and duration.