An orthodontic wire for Crozat appliance meets special requirements. A high value for the yield strength is necessary as well as a remarkable plastic strain. In order to bent a spring over a considerable distance with a small stress resulting a low modulus of elasticity will be advantageous. Besides this properties a special wire developed on the basis of precious metals may be repeatedly softened and hardened by a simple method of heat treatment. Research was done about the forces transmitted from the body wire of a Crozat appliance to the opposite molars. For the case of a simplified lower body wire a formula was derived which allows to calculate the applied force.