1. A method for automatically evaluating the efficacy of plaque removal and whitening capabilities for different toothbrushes and toothpastes on a tooth-by-tooth basis in real-time, comprising: determining a central portion of each tooth with a watershed segmentation algorithm using a center of each tooth as a seed point; applying a reverse watershed segmentation algorithm using an external boundary surrounding each tooth and an internal portion of each tooth as two seed regions, wherein the point at which the two seed regions intersect correspond to the actual tooth boundary; applying a line-based morphing procedure to automatically overlay a grid on each segmented tooth; and classifying plaque regions of each tooth.