1. A method for detecting deviation during an orthodontic treatment plan, the method comprising the steps of: receiving an un-segmented current teeth image representing a patient's teeth after an orthodontic treatment plan has begun and before the orthodontic treatment plan ends for the patient; pre-processing the un-segmented current teeth image; comparing the un-segmented current teeth image with a previously segmented teeth model for an initial match; performing a surface matching step that matches the previously segmented teeth model to the un-segmented current teeth image, the surface matching step comprising: creating a grid on the previously segmented teeth model, selecting sampling points in the grid, and overlaying the grid onto the un-segmented current teeth image; and adjusting a position of a tooth in the previously segmented teeth model to a corrected stage if an error generated after the surface matching step is within a programmable threshold parameter value.