Removable distalizing appliance (The Shamy): A three-dimensional tooth movement analysis after appliance use and subsequent fixed treatment

The objective of this retrospective study was to analyze tooth movements of 15 patients after use of a removable distalizing appliance (the Shamy) and then again after fixed therapy. Fifteen patients (9 girls and 6 boys; mean age: 12 years and 6 months) with either unilateral or bilateral Class II molar relationships were treated to a Class I molar relationship at a private orthodontic practice. Dental casts were taken immediately before (T0) and after Shamy use (T1) and after removal of subsequent fixed appliance therapy (T2). The casts were three dimensionally digitized and superimposed using rugae as landmarks. The resulting superimpositions were analyzed by selecting the same points on all casts. The mean maxillary first molar effective distalization after Shamy therapy was 6.3 mm with 15.4 degrees of tipping. Anchorage loss was expressed by an average 1.5 mm proclination of the central incisors. After fixed appliances almost all the tooth movements and effects from the Shamy were lost (P<.05) however the patient's class II molar relationship was now corrected.