A method and a system for determining an orthodontic treatment for a subject are provided. The method comprises: acquiring a raw 3D representation of an arch form of the subject comprising a 3D mesh having a plurality of vertices further comprising: constrained vertices associated with a defined portion; unconstrained vertices initially associated with an undefined portion; generating a set of confirmed constrained vertices, including the constrained vertices, for providing the augmented 3D representation of the given tooth by: iteratively, for a given constrained vertex, identifying at least one associated unconstrained vertex which is adjacent to the given constrained vertex in the 3D mesh, and based on an angular difference between associated normal vectors, identifying the at least one associated unconstrained vertex either to be a constrained vertex or an unconstrained vertex; causing display of the augmented 3D representation of the given tooth based on the set of confirmed constrained vertices.