Treatment changes in Class I and mild Class II malocclusions using the en masse removable appliance

The aim of this retrospective study was to examine the dental changes which occurred during buccal segment retraction in 39 subjects considered suitable for treatment with headgear to the maxillary dentition. Initially, a removable en masse appliance was fitted to distalize the buccal segments. Once the molar relationship was corrected, fixed appliances were placed for upper arch consolidation and/or alignment. Only five subjects required lower appliance therapy. Twenty-nine individuals had upper second molars extracted as an adjunct to treatment: in the remaining 10 patients these teeth were left in situ. Corresponding lower second molars were extracted in 19 children, whilst 20 pairs of teeth were not removed. Measurements were made at the start of treatment, the completion of buccal segment retraction, and when active treatment was complete. After the first stage, molars and premolars had been retracted nearly 4 mm, whilst the canines showed 2 mm spontaneous distal drift. The inter-molar width had increased by 4 mm and arch perimeter by 5 mm. There was a 5 per cent reduction in crowding. Spontaneous changes were also seen in the lower arch, despite the absence of any therapy. Crowding was slightly improved and inter-molar width increased, apparently as a response to the expansion in the opposing jaw. At the end of treatment, upper arch retraction and expansion were reduced as the teeth were integrated with the lower dentition: the canines required less than 1 mm further retraction. In the lower arch, the expansion of the molars was essentially stable. The extraction of upper second molars did not appear to influence the outcome of treatment. Although slightly more movement appeared to occur in the extraction group, few measurements showed statistical significance.