Molar distalization with a modified pendulum appliance--in vitro analysis of the force systems and in vivo study in children and adolescents

The standard pendulum appliance was modified by integrating a distal screw into its base and by special preactivation of the pendulum springs. The suitability of this Pendulum K for the translatory distalization of maxillary molars was investigated in an in vitro analysis and in an in vivo study in children and adolescents. The in vitro measurement of the resulting force systems revealed that all forces and moments remained virtually constant over a three-mm simulated distalization increment. The transverse force, Fx, increased from two to 11 cN and the weakly intrusively acting force, Fy, from six to eight cN, but these increases were not statistically significant. The distalization force, Fz, initially 201 cN, was still 199 cN after a three-mm distalization increment. The mesially acting moment, My, rose from 1654 to 1834 cN mm, whereas the palatally acting moment, Mz, declined slightly from 229 to 164 cN mm. The slight, consistent distoinclinatory moment, Mx, initially 306 cN mm, was 310 cN mm after three mm. In parallel, the in vivo study with its collective of 66 patients confirmed that the Pendulum K allows a virtually translatory molar distalization with slight tippings of 4.75 degrees to the palatal plane and 4.25 degrees to the anterior basal plane. Palatal movements of the first molars were avoided. The proportion of molar distalization in the total movement was 73.53%.