Jacoby H
Am J Orthod. 1979 Feb;75(2):143-51. doi: 10.1016/0002-9416(79)90183-0.
The ballista spring system is a simplified orthodontic system for treating impacted teeth. The impacted tooth is retracted by a spring that accumulates a continuous force from being twisted on its long axis. The necessary operation on the impacted tooth is simple and less traumatic. The force exerted on the tooth is vertical, without compressing the impacted tooth toward the adjacent roots. This force is well controlled and easily modified. By the lack of appliance on the front teeth during a great part of the treatment, the esthetic side of the treatment is respected. Complicated impacted teeth in adults can be treated.