Rotation of rectangular wire in rectangular molar tubes. Part II. Pretorqued molar tubes.

Buccal tubes from five manufactures producing the new generation of preadjusted (straight wire type) appliances were tested to determine the amount of rotation various-sized rectangular wires produced prior to binding within the tube. This rotation reflected the amount of torquing force dissipated because of the interaction of the wires and tube. In addition, it indicated the degree of compensatory third-order bends needed in the wire to deliver the desired torque force to the tooth. Wire and tube dimensions were measured and compared to manufacturers' stated specifications. The amount of rotation for each manufacturer's tube was compared to the theoretical values based on calculations. Theoretical calculations and published charts of deflection angles based on these calculations give a false impression in that they do not revealed a true expression of the amount of torque dissipated through rotation of the rectangular wire in that tube. There is variation between the manufacturer's stated lumen dimension and the actual lumen size, even beyond the manufacturer's stated tolerances. Rectangular wire will rotate within a rectangular buccal tube to varying degrees, depending upon the size of the wire used and the manufacturer of the appliance. This means that additional torsion or angulation may need to be placed in the wire prior to application intraorally. The amount of this additional torquing of the arch wire will depend upon the manufacturer of the appliance used and will vary from tube to tube of the same manufacturer.