An orthodontic assembly configured for moving the relative positions of upper and lower dental arches each having an occlusal reference plane, the assembly comprising: an upper molar appliance having a passage; an upper arm comprising a solid cylindrical rod having a distal end segment and a mesial segment, a portion of the distal end segment received in the passage, the mesial segment having a length extending in a generally mesial direction from the upper molar appliance and the distal end segment, wherein the longitudinal axis of the distal end segment extends at an angle relative to the longitudinal axis of the mesial segment when viewed in directions perpendicular to an occlusal reference plane, and wherein the mesial segment culminates in a coupling segment, the coupling segment bent at an angle of 70 degrees to 110 degrees relative to the longitudinal axis of the mesial segment when viewed in directions parallel to the upper occlusal reference plane; a stop coupled to the distal end segment and disposed distal to the passage; a lower module comprising a hollow first member having a tubular elongate shape and a second member comprising a solid cylindrical rod received at least partially within the first member, the second member pivotally connected to the upper arm at a central pivot link including a first segment having a first passage and a second segment having a second passage, the first and second segments (133, 131) coupled by a hinge defining a first axis of rotation extending generally perpendicular to the distal end segment of the upper arm, wherein the coupling segment is received in the first passage and the second member is received in the second passage; the first and second members (210, 220) coupled to a helical compression spring coaxial with at least a portion of said first member and said second member; and a lower molar appliance, wherein the lower module is rotatably coupled to the lower molar appliance at an end cap of the first member for rotation about a second axis generally parallel to the first axis of rotation, wherein, when the upper and lower arches are closed, the first passage extends along a generally occlusal-gingival axis, and wherein the second passage extends along a generally mesiodistal axis and is located nearer the upper arch than the first passage, and wherein the upper arm is pivotable relative to the lower module about the first axis of rotation. an upper molar appliance having a passage; an upper arm comprising a solid cylindrical rod having a distal end segment and a mesial segment, a portion of the distal end segment received in the passage, the mesial segment having a length extending in a generally mesial direction from the upper molar appliance and the distal end segment, wherein the longitudinal axis of the distal end segment extends at an angle relative to the longitudinal axis of the mesial segment when viewed in directions perpendicular to an occlusal reference plane, and wherein the mesial segment culminates in a coupling segment, the coupling segment bent at an angle of 70 degrees to 110 degrees relative to the longitudinal axis of the mesial segment when viewed in directions parallel to the upper occlusal reference plane; a stop coupled to the distal end segment and disposed distal to the passage; a lower module comprising a hollow first member having a tubular elongate shape and a second member comprising a solid cylindrical rod received at least partially within the first member, the second member pivotally connected to the upper arm at a central pivot link including a first segment having a first passage and a second segment having a second passage, the first and second segments (133, 131) coupled by a hinge defining a first axis of rotation extending generally perpendicular to the distal end segment of the upper arm, wherein the coupling segment is received in the first passage and the second member is received in the second passage; the first and second members (210, 220) coupled to a helical compression spring coaxial with at least a portion of said first member and said second member; and a lower molar appliance, wherein the lower module is rotatably coupled to the lower molar appliance at an end cap of the first member for rotation about a second axis generally parallel to the first axis of rotation, wherein, when the upper and lower arches are closed, the first passage extends along a generally occlusal-gingival axis, and wherein the second passage extends along a generally mesiodistal axis and is located nearer the upper arch than the first passage, and wherein the upper arm is pivotable relative to the lower module about the first axis of rotation.