Objective To compare the values of equivalent( von-misses) stress on periodontal ligament between two placement methods of ball-cap attachment. Methods The two 3-dimensional finite element models of ball-cap were built,attached with two placement methods with two different crown-root ratios( 0.96 and 1.5). The equivalent( von-misses) stress and the maximum principal stress on periodontal ligament were analyzed. Results Under two crown-root ratios,the equivalent( von-misses) stress and the maximum principal ...