Holographic determination of centers of rotation produced by orthodontic forces.

A new tool for measuring tooth movement--laser holography--offers an accurate, noninvasive approach for determining movement in three dimensions. This in vitro study is designed to establish the required force system applied on the crown of a maxillary incisor that would produce different centers of rotation, as in lingual tipping, translation, and root movement. The relationship between moment-to-force ratios and centers of rotation is shown. The experimental data are compared to theoretic approaches. With respect to the location of the center of resistance and centers of rotation, force systems needed to produce different centers of rotation are given for a central incisor of average root length.