transpalatal orthodontic appliances of the present invention contemplate a variety of configurations , all of which include a force - supplying member of a low modulus , shape - memory or superelastic alloy . examples , of suitable alloys include nickel - titanium alloys in various stoichiometric ratios , as disclosed in u . s . pat . no . 4 , 037 , 324 . u . s . pat . no . 5 , 044 , 947 discloses a nickel - titanium and copper alloy which may also be suitable for use in the present invention . the disclosures of these patents are hereby expressly incorporated herein by reference . it will be appreciated that each alloy composition will possess a different shape - memory characteristic , a different transformation temperature ( a f ), a different modulus of elasticity , and a different working range . thus , the particular alloy composition to be utilized in the orthodontic appliances of the present invention will be selected based on the desired forces supplied by the appliance upon activation thereof and / or the transition temperature of the alloy . in all embodiments of the present invention , the force - supplying member of the appliance has a predetermined configuration determined by the clinician . once the appliance is placed in the patient &# 39 ; s mouth , the force - supplying member is activated , whereupon the shape - memory characteristic thereof causes the force - supplying member to transform or return to its predetermined configuration , thereby imparting desired expansive or contractive forces to move the patient &# 39 ; s teeth to desired positions and / or to expand the midpalatal suture . the forces exerted may be in the range of about 300 - 3 , 000 grams . with reference to the drawings , fig1 - 4 and 8 - 15 show various alternative embodiments of orthodontic appliances of the present invention . fig1 shows appliance 10 mounted in the upper dental arch 12 of a patient . appliance 10 comprises a trans - palatal arch bar member 14 made of a shape - memory or superelastic alloy . shape - memory or superelastic alloy member 14 supplies the desired corrective forces to the teeth in a dental arch upon activation thereof . the corrective forces are substantially constant and ar exerted along substantially a single axis in generally opposed directions . in this particular embodiment , member 14 has its terminal ends 16 embedded in teeth - abutting members 18 which may be acrylic or other suitable material . teeth - abutting members apply the corrective forces supplied by member 14 to several teeth on opposite sides of the dental arch . this serves to expand the palate of the patient by moving the teeth outwardly and expanding the arch , and may have the capability of opening the midpalatal suture . in an alternative embodiment shown in fig2 terminal ends 16 of force - supplying transpalatal arch member 14 are coupled directly to the first molars in the dental arch by means of brackets 20 affixed to the teeth . in fig2 the force - supplying member exerts outwardly - directed corrective forces on the teeth to which it is attached . fig3 shows a pair of orthodontic appliances 10 in the form of transpalatal arches mounted in a patient &# 39 ; s upper dental arch 12 . the arrows indicate forces supplied by the transpalatal arches upon activation of the force - supplying members . in this embodiment , both arches 10 provide outwardly - directed expansive forces on the teeth to which they are affixed . fig4 shows another alternative embodiment , similar to that shown in fig3 wherein two transpalatal arches are affixed to different pairs of teeth in the dental arch . in this embodiment , the corrective forces supplied are generally in opposite directions , as indicated by the arrows . more particularly , upon activation of the force - supplying members , transpalatal arch 30 exerts expansive forces on the first bicuspids and transpalatal arch 32 concurrently exerts contractive forces on the first molars . with this combination of appliances , and variations thereof , virtually any desired tooth or arch manipulation can be achieved . it will be appreciated that in embodiments of the present invention such a those shown in fig3 and 4 , the corrective forces supplied by the transpalatal arches may be in the same or opposite directions . it will also be appreciated that forces of substantially the same or different magnitudes may be supplied , depending on the required tooth or arch manipulation . in the embodiments shown in fig1 - 4 , the force - supplying members in the orthodontic appliances comprise a transpalatal arch which includes a u - shaped , spring - like section 40 . various alternative configurations of the transpalatal arch will be apparent to persons of ordinary skill in the art . several contemplated alternatives are shown in fig8 - 11 . the transpalatal arch shown in fig8 a and 8b has a zig - zag configuration . fig8 a shows a plan view of the arch prior to activation and fig8 b shows the arch subsequent to activation . in fig9 a and 9b , the transpalatal arch consists of continuous s - shaped curves . fig9 a shows the arch prior to activation and fig9 b shows the arch subsequent to activation . fig1 a and 10b , respectively , show a frontal view of a transpalatal arch with a u - shaped medial segment in its pre - and post - activation configurations . finally , fig1 a and 11b show an embodiment of the present invention wherein the force - supplying member is generally in the shape of a ring 50 having bracket members 60a and 60b on diametrically opposite sides thereof for attachment to the desired teeth in the dental arch . fig1 a shows ring member 50 prior to activation and fig1 b shows ring member 50 subsequent to activation . fig7 illustrates one drawback associated with some prior art transpalatal arches . due to the nature of the forces exerted by stainless steel or other relatively high modulus materials , i . e ., an initially high force which rapidly decreases , the teeth 70a and 70b to which the arch is affixed may be tipped , as shown in fig7 . in many instances this tipping or torquing of the teeth is undesirable and may occur to the exclusion of the desired translating movement of the teeth . the tipping must then be corrected utilizing a secondary procedure . fig6 shows an embodiment of an orthodontic appliance of the present invention which overcomes the above - described drawback of prior art arches . as shown in fig5 and 6 , terminal portions 75a and 75b of orthodontic appliance 76 are pre - torqued or pre - stressed to counteract the tendency of the expansive forces to tip teeth 72a and 72b . fig5 shows terminal portion 75b of orthodontic appliance 76 as it is fitted into cooperation with bracket 78 attached to tooth 72b . pre - torquing the terminal portion 75b may be accomplished by twisting the terminal portion from a predetermined configuration such that upon activation thereof it returns to its predetermined configuration , thereby counteracting any torquing or tipping forces applied to the teeth by transpalatal arch 76 . in an alternative embodiment shown in fig1 , an orthodontic appliance 80 of the present invention includes a force - supplying , superelastic or shape - memory alloy member 82 with rigid structure at its terminal ends 84a , 84b for attachment to a patient &# 39 ; s teeth . more particularly , fig1 shows a transpalatal arch 80 comprising a medial shape - memory alloy segment 82 and terminal end segments 84a and 84b of stainless steel or other relatively rigid material . since the generally u - shaped medial segment 82 is a shape - memory alloy , it supplies substantially constant corrective forces upon activation . this embodiment is advantageous when more rigid structure is required at the point of connection to the patient &# 39 ; s teeth . fig1 shows an alternative embodiment of an orthodontic appliance comprising a shape - memory alloy member for supplying the corrective forces and rigid structure for attachment to the teeth . orthodontic appliance 100 is shown in fig1 affixed to several teeth in an upper dental arch 102 . appliance 100 comprises a force - supplying member 104 in the form of a ring of superelastic or shape memory alloy . appliance 100 further comprises a plurality of relatively rigid legs 106 ( e . g ., stainless steel ) which transmit the forces supplied by ring 104 to the teeth in the dental arch to which they are affixed , as by brackets 108 . fig1 and 15 show additional alternative embodiments of an orthodontic appliance of the present invention . this particular embodiment is suitable for providing contractive forces ( or , with design modifications , expansive forces ) on selected teeth in a dental arch . as shown in fig1 , appliance 110 includes a coil spring 112 of superelastic or shape - memory alloy and first and second ligation wires 114 and 116 , respectively . appliance 110 also includes a pair of end caps 118 , 120 designed to receive the terminal ends 122 , 124 , respectively , of first and second ligation wires 114 and 116 , such that coil spring 112 is captured therebetween . in the particular embodiment illustrated , each of the end caps 118 , 120 has a generally cupshaped configuration for receiving a respective terminal end of spring 112 . associated with each end cap 118 , 120 are first and second ligature wires , 114 , 116 , respectively . terminal ends 122 , 124 of ligature wires 114 , 116 are sized and configured such that they will not pass through the openings in the end caps . as shown in fig1 , the terminal ends 122 and 124 comprise an enlarged bulbous section which is integrally formed at the end of the wire . however , it is to be understood that the terminal ends may be formed in any desired manner ; the only requirement is that the terminal ends of the wires 114 , 116 not pass through the openings in the end caps . the free end 126 , 128 of each ligature wire is used to ligate the appliance to the appropriate orthodontic brackets 130 that have been affixed to teeth 132 in the patient &# 39 ; s mouth . when appliance 110 is ligated to brackets 130 , coil spring 112 is in compression . upon activation of the shape - memory or superelastic alloy spring 112 , it tends to expand , thereby exerting expansive forces outwardly against end caps 118 , 120 , which , in turn , apply contractive forces on teeth 132 via ligating wires 114 , 116 . the size , shape and alloy composition of coil spring 112 are selected to provide the desired contractive forces . the orthodontic appliance embodiment shown in fig1 is similar to that shown in fig1 . in fig1 , the ligature wires 114 , 116 have disks 140 , 142 affixed to their terminal ends . disks 140 , 142 are sufficiently large in diameter that they will not pass through coil spring 112 , thus obviating the need for end caps these spring / ligature combinations may also be used as class ii , class iii , space closure and headgear devices or for correction of tooth discrepancies relative to one another . while the orthodontic appliances of the present invention have been described with reference to the drawings , the scope of the present invention is not intended to be limited to the particular examples shown or described . it is contemplated that variations in design will be apparent to persons skilled in the art . therefore , the scope of the present invention is defined by the appended claims .
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 alloys , the titanium - molybdenum alloys , 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 × 10 6 psi .