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