When an orthodontic appliance is attached to the lingual side (back side) of teeth which is invisible from the outside, a large difference in level of the surface between adjacent teeth requires utilization of a wire bent in a complicated fashion. It has been found, however, that the difference in level between adjacent teeth is very small in a horizontal plane at a boundary between a crown and a root, thereby making it possible to draw a smooth envelope therealong. Based on this finding, with a view to placing a wire along such an envelope, a "lingual straight archwire" having a planar configuration comprising a simple curve and straight lines smoothly connected to ends of the curve and residing in a single horizontal plane and a bracket having a configuration suitable for the placement of the archwire are provided.

Transpalatal orthodontic appliances are disclosed which utilize a shape-memory or superelastic alloy member as the force-supplying member of the device. Suitable alloys include the nickel-titanium (NiTi) alloys, the titanium-molybdenum alloys (TMA), and any other alloy composition which possesses superelastic or shape-memory characteristics. The alloy composition may preferably have a working rang of at least about 30% and a modulus of elasticity not exceeding about 15.times.10.sup.6 psi.

A multiarch assembly comprises first and second parallel archwires, each formed into a segment of an orthodontic archform spanning a plurality of a patient's teeth, a multiarch bracket having a bracket body defining reentrant archwire slots along opposite occluso-gingival sides of the base for receiving and seating the first and second archwires in a base portion therein, the base portions of the slots having a predetermined center-to-center occluso-gingival spacing; and an interarch connector having a connector body formed of a resilient material with first and second archwire openings spaced apart along an occluso-gingival axis of elongation and sized for the first and second archwires to be threaded therethrough, the connector body being resiliently deformable along the axis of elongation to enable the archwires to be spread apart and then to urge the archwires toward one another in a direction of contraction along the axis of elongation; the holes in the interarch connector being spaced center-to-center a distance approximately equal to or less than the center-to-center spacing between the base portions of the occluso-gingival spacing of the archwire slots on opposite sides of the bracket; whereby the archwires, multiarch bracket and interarch connector exert force on the bracket, and thereby on the patient's teeth, with gradually increasing precision as the occluso-gingivally spaced archwires are urged by contraction of the interarch connector toward one another into the base portions of the spaced slots.

A lingual orthodontic bracket includes a body (12) having a three-sided archwire slot (14, 414), and a hinged closure member (22, 422) pivotally and pivotable across the archwire slot and into a closed position in the closure member slot. The closure member includes a cam shaped central portion (28, 428A, 428B) extending across the archwire to retain it in the archwire slot under shear. The cam portion is convexly shaped to seat the archwire in the slot during closure. A bumper or rotation member (340, 440) can be used to bias the archwire against the closure member. The closure member (422) is formed with two sides that enclose the sides of the bracket and locking ears (425A, 425B) that engage the bracket body. The bracket includes two oppositely directed wings (418, 426) for receiving a ligature or O-ring.

A lingual orthodontic bracket includes a body having a three-sided archwire slot, a closure member slot, and a hinged closure member pivotally and pivotable across the archwire slot and into a closed position in the closure member slot. The closure member includes a cam shaped portion extending across the archwire to retain it in the archwire slot under shear. The cam portion is convexly shaped to force the archwire to seat in the slot as the closure member is rotated toward the closed position, and has a neutral to over-center or negative camming action upon closure to retain the closure member in the closed position. The closure member includes a protrusion that wedges into the closure member slot in the closed position, The bracket includes two oppositely directed wings formed respectively on the body and the closure member for receiving a ligature or O-ring.