AN EVALUATION OF THE TORSIONAL MOMENTS DEVELOPED IN ORTHODONTIC APPLICATIONS - AN IN-VITRO STUDY

The amount of play between brackets and wire and the magnitude of the torsional moments developed have been investigated for six different r ectangular wires. The study simulated the situation occurring when tor que is applied to an individual central incisor. The observed play bet ween wire and bracket ranged from about 5-degrees- between an 0.018 x 0.025 inch in an 0.018-inch bracket slot, to approximately 20-degrees for a 0.016 x 0.022 inch in an 0.018-inch bracket slot. The observed r ate of change after the play had been eliminated, varied from 0.24-deg rees/Nmm to 0.37-degrees/Nmm for the steel wires, whereas 0.017 x 0.02 5-inch nitinol had a rate of change of approximately 1.07-degrees/Nmm. The use of ligatures demonstrated that a torque effect could be obser ved even though the play had not been completely eliminated.