A comparison of three appliance systems in the treatment of Class III malocclusion.

The modes of action of the Function Regulator III, Upper Removable Appliances and the Edgewise appliance were compared by analysing the cephalometric records of 66 subjects, treated for Class III malocclusion, with anterior crossbite, both by means of conventional and tensor methods. These were found to be similar for the three appliances and were characterized by a change in mandibular posture, increasing lower face height and reducing angle SNB, as compared with a control group, combined with varying degrees of incisor proclination and retroclination. The FR.III group, however, showed a small but significant increase in cranial base flexure compared with the other groups, as well as greater improvement in skeletal relationships as compared with the URA group, particularly when assessed by Enlow's method. The differences in upper and lower incisor inclinations combined with other effects produced by the appliances were assessed by an ‘efficiency ratio’ which related the amount of change in incisor inclination produced for each millimetre of increase in overjet as follows: FR.III = 1.8, Edgewise = 2.1 and URA = 2.8.