Abstract: An appliance for separating a pair of adjacent teeth comprising a wire spring formed into an approximate U-shape having two leg segments and a connecting bridge segment. The leg segments are drawn to either side of a reference plane such that the bridge segment is in torsional strain when the leg segments are near coplanar. This torsional strain causes the legs to apply a force to the proximal walls of the adjacent teeth. One leg has a hook end which acts an an anchor in the lingual or the buccal embrasure during installation of the spring, while the other leg has an abrupt bend which acts as an antirotational feature.