The aim of this study was to determine tooth movements in the upper dental
arch using a simulated original model during the time of activation of two
active plates modifications, symmetrically and asymmetrically cut plates. T
he changes of the dental arch dimensions and precise evaluation of the dist
ribution of the forces produced by appliance were analysed by recording too
th movements. In order to register tooth movements more precisely true refe
rral points were notched on each tooth thus creating 38 variables which def
ined weight and lengths of the dental arch. The symmetrically cut active pl
ates used to obtain transversal expansion affect equally both sides and cau
se symmetrical movements of premolars, less of molars and canines, whereas
they have no effect on incisors. The asymmetrically cut active plates used
to obtain transversal expansion affect more the side of smaller active part
of the plate. Movements are larger at the premolars than at molars and can
ines, and minimal at incisors. The results of this study confirm the data f
rom the Literature and a logical interdependence of the force and movements
thus emphasising the importance of anchorage in orthodontic therapy.