抄録
The purpose of the present paper was to clarify the ballista spring mechanism. An experimental apparatus was used to measure the orthodontic forces during traction of palatally impacted canines. The following results were found:
1. The length for clinical-use is from minimum 10.65 mm to maximum 24.03mm in perpendicular bending section and from minimum 15.24mm to maximum 22.46mm in horizontal bending section. 2. The load of ballista spring wire is narrow in proportion to its diameter, length of vertical and horizontal bending section, and active angle.
3. Since the active angle of wire became 160° and wire of each diameter exceeded the elastic limit, an adequate upper range in clinical pathology is surmised to be within 140°.
4. 0.014 inch diameter round wire has too weak to use as orthodontic power.
5. Use 0.016 inch diameter round wire if the vertical bending section is within 15mm use.
6. 0.014 inch diameter round wire is best for ballista spring appliance wire.
From the above, a diameter of 0.018 inch round wire is best suited for a ballista spring device, but in case of a short distance from the dental arch to an impacted tooth, it is necessary to get a week force by making the wire size small or by assembling the helical loop to elongate the wire length to the impacted tooth.
