A method of determining an orthodontic treatment comprising: obtaining a 3D model of a simulated position of upper and lower teeth following a simulated orthodontic treatment, the 3D model comprising a point cloud representation comprising a plurality of vector points； in a 3D grid having cells onto which the plurality of the vector points have been mapped, identifying cells containing vectors points representative of the upper teeth and applying a first mask to these cells； identifying cells containing vectors points representative of the lower teeth and applying a second mask to these cells； determining the simulated orthodontic treatment as the determined orthodontic treatment if the 3D grid does not include at least one cell which includes both the first mask and the second mask.
