referring to the drawings , fig1 is a side elevational view of a ribbon arch self - ligating bracket system 5 provided in accordance with one embodiment of the present invention . system 5 is comprised of brackets for anterior and posterior teeth on both the upper and lower arch , linked with a ribbon archwire . fig2 is an enlarged partial side - elevational view of the bracket system of fig1 showing brackets 10 on the upper and lower incisor . fig3 to 9 show bracket 10 from various angles , both with and without inserted archwires . bracket 10 comprises a base 12 and a body 14 extending from the base 12 in a buccal / labial direction . base 12 is adapted to face and be bonded to a patient &# 39 ; s tooth in a known manner , such as a mesh bonding pad , or an integral base . an archwire slot 16 extends across body 14 in a generally mesial - distal direction . archwire slot 16 is bounded on three sides by a buccal / labial wall 18 , a lingual wall 20 , and a gingival wall 22 . archwire slot 16 , therefore , has a vertical orientation . according to the embodiment shown , an opening 24 of archwire slot 16 faces in an occlusal direction ( i . e . towards the tip of the tooth ). each of buccal / labial wall 18 and lingual wall 20 have at least one rail 26 extending towards the middle of archwire slot 16 for providing a smaller archwire contact area . rail 26 in lingual wall 20 also enables improved tooth control by an archwire than if the archwire were seated directly against lingual wall 20 . gingival wall 22 is partially arched in profile , also to provide a smaller archwire contact area . lingual wall 20 is beveled in a portion adjacent to slot opening 24 so as to form an entry ramp 28 for ease of insertion of an archwire into archwire slot 16 . a slotted leaf spring 32 is located in archwire slot 16 for releasably retaining an archwire therein . a sectional view of the relationship of slotted leaf spring 32 with bracket 10 is shown in fig9 . a perspective view of the slotted leaf spring 32 is shown in isolation in fig1 . slotted leaf spring 32 is made of nickel - titanium alloy , and its gingival end 34 is inserted into a vertically - oriented recess 33 in body 14 . slotted leaf spring 32 is free to move within recess 33 . a curved portion 35 of slotted leaf spring 32 connects gingival end 34 to a buccal / labial end 36 , and generally arcs through archwire slot 16 . slotted leaf spring 32 then curves away from archwire slot 16 in a generally buccal / labial direction . like gingival end 34 , buccal / labial end 36 of slotted leaf spring 32 is not fixed to body 14 . rather , it is free to move against the bias of slotted leaf spring 32 in a generally buccal / labial - lingual direction along a niche 30 formed in body 14 . tiewings 37 extend from body 14 and provide other ligation options such as conventional manual ligation using o - rings or the like , if desired by a clinician . there are two tiewings 37 shown on each bracket . a horizontal reference line 44 is cut or otherwise marked onto a buccal / labial - facing surface of body 14 and , in conjunction with a similarly - formed vertical reference line 46 , provides alignment guidance to a clinician when bonding bracket 10 to a tooth . horizontal reference line 44 denotes the centre of the archwire slot 16 and is placed parallel to the incisal edge of the associated tooth . vertical reference line 46 denotes the centre of the long axis of the associated tooth . horizontal reference line 44 and vertical reference line 46 are meant to cross at the theoretical centre of the associated tooth . height gauge channel 48 , also formed in the buccal / labial - facing surface of body 14 , is sized and shaped to receive the blade of various commercially available bracket height gauges , as would be understood by one of ordinary skill in the art . an indentation 50 on the buccal / labial - facing surface of body 14 marks the disto - gingival orientation of bracket 10 . indentation 50 receives a quantum of colored ink . the color of the ink identifies for a clinician in which quadrant bracket 10 is to be used . slotted leaf spring 32 is biased to the rest position shown in fig5 ( shown in this case with a round archwire 200 ), in which opening 24 is partially obstructed , in order to retain an archwire in archwire slot 16 . slotted leaf spring 32 is moveable against its bias by application of sufficient force in a buccal / labial and / or occlusal - gingival direction to a release position , in which opening 24 is sufficiently unobstructed in order to insert or remove an archwire . because of the configuration of curved portion 35 with respect to archwire slot 16 , force exerted by an archwire under influence in a generally occlusal direction against curved portion 35 of slotted leaf spring 32 will cause buccal / labial end 36 to move in a buccal / labial direction through niche 30 . similarly , gingival end 34 will move freely through recess 33 . as it moves through niche 30 and recess 33 , slotted leaf spring 32 recedes from slot opening 24 thereby allowing the archwire to be removed from vertical archwire slot 16 . in a similar manner , force exerted by an archwire under influence in a generally gingival direction from the direction of opening 24 will cause buccal / labial end 36 of slotted leaf spring 32 to move in the buccal / labial direction through niche 30 . similarly , gingival end 34 will move freely through recess 33 . as it moves through niche 30 and recess 33 , slotted leaf spring 32 recedes from slot opening 24 thereby allowing the archwire to be inserted into vertical archwire slot 16 . it can be seen that slotted leaf spring 32 cooperates with lingual wall 20 and gingival wall 22 in order to retain an archwire . an archwire of large enough dimensions is fully seated against lingual wall 20 and gingival wall 22 by pressure from slotted leaf spring 32 in both a lingual and a gingival direction due to slotted leaf spring 32 being held against its bias by such an archwire in archwire slot 16 . in the rest position , slotted leaf spring 32 covers up to about 60 % of the width of slot opening 24 , in order to ease insertion and removal of an archwire . preferably , a 0 . 011 inch gap between slotted leaf spring 32 and lingual wall 20 is suitable for retaining archwires as small as 0 . 014 inches in diameter . due to the cooperation between slotted leaf spring 32 , lingual wall 20 and gingival wall 22 , small archwires with , for instance , round cross - section , may be retained within archwire slot 16 without being forced into a fully seated position by slotted leaf spring 32 . this enables gradual correction of the tooth . during treatment , archwires of different wire stiffness and sizes may be employed in order to incrementally provide increased expression of the torque , tipping and rotational forces required to move the teeth to their ideal position . it will be understood that over the duration of treatment , different shaped archwires will be employed in order to efficiently move the teeth as desired . fig5 shows bracket 10 having received a round archwire 200 . slotted leaf spring 32 retains round archwire 200 in archwire slot 16 . because of the size of round archwire 200 , however , slotted leaf spring 32 does not seat round archwire 200 completely in archwire slot 16 . instead , round archwire 200 provides guidance for bracket 10 during tooth movement for initial phases ( known as the leveling phase ) of orthodontic treatment . fig6 shows bracket 10 having received an oval ribbon archwire 202 . oval ribbon archwire 202 provides a clinician with gradual control over torquing forces , in particular . some rotation generally about a mesial - distal axis by oval ribbon archwire 202 is possible as treatment progresses because wire leaf spring 32 enables some degree of both labio - lingual and occlusal - gingival movement of the archwire with respect to the bracket . this provides for leveling , rotation and initial torquing forces while at the same time preventing absolute rigidity and restrictive binding in archwire slot 16 . fig7 shows bracket 10 having received a rectangular ribbon archwire 204 . rectangular ribbon archwire 204 provides a user with still further increased control over torquing forces , in particular . a light constant force is applied by spring 32 against archwire 204 , which force gradually expresses the prescriptive torque value of the bracket 10 . fig8 shows bracket 10 having received a 5 - sided ribbon archwire 206 . 5 - sided ribbon archwire 206 provides maximum control over torquing forces , in particular . slotted leaf spring 32 fully seats archwire 206 in archwire slot 16 by exerting spring force in both a gingival and a lingual direction against gingival wall 22 and lingual wall 20 , respectively . as would be known , such a 5 - sided ribbon archwire 206 is used in the end stages of treatment . as can be seen , slotted leaf spring 32 has a configuration with respect to the walls of archwire slot 16 that can accommodate different cross - sections and sizes of archwire , while at the same time providing correct seating and therefore correct force expression from an archwire via bracket 10 to the associated tooth . fig9 is a cross - sectional side view of bracket 10 with slotted leaf spring 32 . it can be seen that the edges of niche 30 are rounded for reduced friction , and that slotted leaf spring 32 rests on the occlusal wall of niche 30 . slot recess 33 permits gingival - occlusal sliding of gingival end 34 of slotted leaf spring 32 through slot recess 33 when slotted leaf spring 32 is being forced against its bias . a short post 31 extends vertically from the occlusal wall of niche 30 through the slot of slotted leaf spring 32 to ensure that slotted leaf spring 32 remains loosely coupled to bracket 10 during use . post 31 is short enough to allow slotted leaf spring 32 to be slid above it through niche 30 when first coupling slotted leaf spring 32 and bracket 10 . fig1 is a perspective view of slotted leaf spring 32 , and its relationship to post 31 when in niche 30 . fig1 is a perspective view of an alternative slotted leaf spring 32 a with a gingival end 34 a and curved portion 35 a similar to gingival end 34 and curved portion 35 of slotted leaf spring 32 shown in fig1 . however , at buccal / labial end 36 a of alternative slotted leaf spring 32 a , the slot is open - ended . buccal / labial end 36 a may be received in a single niche 30 , or in two , smaller niches . fig1 is a perspective view of an alternate widened slotted leaf spring 32 b , with a widened and open - ended slot . gingival end 34 b is wider than gingival end 34 of the slotted leaf spring 32 shown in fig1 . also , the slot of the widened slotted leaf spring 32 b is wider through curved portion 35 b , and is open at buccal / labial end 36 b . buccal / labial end 36 b would be received in two niches 30 , as shown in fig1 , 20 and 21 . fig1 is a perspective view of another alternate widened slotted leaf spring 32 c , with widened and open - ended slot . gingival end 34 c is similar to gingival end 34 b of the slotted leaf spring 32 b shown in fig1 , except gingival end 34 c is generally u - shaped rather than flat . also , through curved portion 35 c , the spring slot has an arched shape . these differences give leaf spring 32 c a generally h - shaped configuration . fig1 is a perspective view of an alternative retention spring in the form of a wire leaf spring 132 . gingival end 134 of wire leaf spring 132 is free to move within recess 33 . a curved portion 135 of wire leaf spring 132 connects its gingival end 134 to its buccal / labial end 136 , and generally arcs through archwire slot 16 . wire leaf spring 132 then curves away from archwire slot 16 in a generally buccal / labial direction . like gingival end 134 , buccal / labial end 136 of wire leaf spring 132 is not fixed to body 14 . rather , it is free to move against the bias of wire leaf spring 132 in a generally buccal / labial - lingual direction along niche 30 formed in body 14 . as an alternative to a single recess 33 in body 14 , there might be two smaller cylindrical recesses ( not shown ) for receiving the two portions of the gingival end 134 of the wire leaf spring 132 . fig1 is a bottom - perspective view of a bracket 10 , showing a second alternative wire leaf spring 132 a retaining a five - sided archwire 206 . wire leaf spring 132 a has a gingival end 134 a , a curved portion 135 a and a buccal / labial end 136 a . it can be seen that wire leaf spring 132 a is similar to alternative slotted leaf spring 32 b in that it is wide , and has an open - ended slot configuration . in this example , the portions of buccal / labial end 136 a of wire leaf spring 132 a move along respective cylindrical niches ( not shown ) that are similar in function to niche 30 except that they do not extend entirely through the bracket body . due to its overall width , gingival end 134 a is free to move in an occlusal - gingival direction along a wider recess ( not shown ). fig1 is a bottom view of the bracket of fig1 , showing the arched gingival wall 22 of slot 16 and the slot opening 24 partially obstructed by the second alternative wire leaf spring 132 a . it can be seen in fig1 that alternative wire leaf spring 132 a spans nearly the length of the archwire slot 16 , with the wire portions of its buccal / labial end 136 a being spaced apart such that they align with respective tie wings 37 , rather than between them . fig1 and 18 show a bracket 10 , according to an embodiment of the invention , showing a 5 - sided archwire 206 retained by leaf spring 32 , and a hook 38 integral with one of the tie - wings 37 . integral hook 38 provides a hold for auxiliary tooth movement devices such as elastics , coil springs , elastic springs , for example , as would be understood by one of ordinary skill in the art . fig1 is a front elevational view showing a bracket 10 for anterior use similar to that shown in fig1 and 18 . however , there are two spaced - apart niches 30 instead of a single niche 30 . in this embodiment , therefore , an alternative slotted leaf spring such as that shown in fig1 or fig1 is employed . in fig1 , a round archwire 200 is being retained . fig2 is a front perspective view of the bracket 10 shown in fig1 , retaining a rectangular ribbon archwire 204 . fig2 is a bottom - side perspective view of the bracket 10 shown in fig1 , retaining a 5 - sided archwire 206 . fig2 shows an alternative bracket 10 for anterior use having a generally trapezoidal shape . according to this embodiment , archwire slot 16 is not perpendicular to “ vertical ” reference line 46 . in fig2 , a round archwire 200 is being retained . fig2 and 24 show a lower 1 st molar bracket 70 with a convertible buccal tube 72 by virtue of a convertible cap 74 . convertible cap 74 is a removable element that has been attached to the bracket 70 by tack welding or soldering during its assembly process . the convertible buccal tube 72 is very useful for en masse archwire insertion and removal prior to placing the second molars in treatment . once the 2 nd molar brackets 90 are used in treatment , convertible cap 74 may be removed from the 1 st molar brackets 70 , thereby making the entire slot amenable to insertion of an archwire in the second molar bracket 90 . the archwire ends may be inserted into the 2 nd molar tubes and the archwire inserted into the remaining brackets in the occlusal - gingival direction into open archwire slots 16 , as will be described below . also shown is hook 76 used for auxiliary traction with one or more elastics or retraction coils , as would be understood by one of ordinary skill in the art . fig2 and 26 show an upper first molar bracket 80 having a buccal headgear tube 82 for receiving an extra - oral device such as headgear , and a convertible buccal tube 72 by virtue of convertible cap 74 . buccal headgear tube 82 is generally round in cross - section and has a diameter opening between 0 . 045 and 0 . 051 inches . a roller bearing 84 is seated in slot 86 of bracket 80 to facilitate movement of an archwire within the slot to reduce friction during treatment . as can be seen , the retention spring functions in conjunction with the walls of the archwire slot to retain an archwire . where the archwire is large enough , each the spring engages the archwire and provides partial or full seating and accordingly , torque transmission due to being held by an archwire against their rest position bias . the bracket , therefore , either fully seats an archwire in its archwire slot , or more gently moves the tooth appropriately under influence of the spring bias to its correct position . referring to fig2 , a colored bracket cover 66 , molded from a single piece of plastic , metal , rubber , ceramic or combinations thereof may be snapped into a notch 68 in body 14 ( bracket 10 shown ) or otherwise fitted onto the outside of body 14 . depending on a patient &# 39 ; s preference , the colored bracket cover 66 may be tooth - colored for making the bracket less visible , or of another color . as can be seen , bracket cover 66 does not interfere with slot 16 nor interfere with the archwire , and thus does not interfere with the free sliding mechanics in leveling , aligning , or opening and closing of the slot opening 24 . fig2 shows a cutaway side view of the bracket of fig2 and its relationship with the bracket cover 66 . it will be understood that other relationships between bracket cover 66 and bracket 10 that enable bracket 10 to be covered in this manner may be conceived . it will be understood by one of ordinary skill in the art that some patients , particularly children , have not formed 2 nd molars suitable for appropriate use of a 2 nd molar bracket . as such , the convertible brackets 70 and 80 bonded to 1 st molars may be used to “ anchor ” an archwire . during treatment , the 2 nd molars may erupt and need to be included in the treatment . in this case , the convertible caps 74 of the convertible brackets 70 and 80 may be removed with a conversion tool to facilitate insertion of an archwire into the 2 nd molar tubes . once convertible caps 74 have been removed , the 1 st molar brackets 70 and 80 operate in a similar manner as brackets 10 . fig2 a - 29 e show a round archwire 200 being installed into the self - ligating system 5 on a patient &# 39 ; s lower arch . the convertible caps 74 are first removed from the two 1 st molar brackets 70 ( only one portion of the arch is shown for ease of understanding ), and the two ends of archwire 200 are inserted into respective 2 nd molar tubes 90 . once its ends are in the 2 nd molar tubes 90 , the arched archwire 200 is pivoted downwards generally about an axis connecting the two 2 nd molar tubes 90 to progressively enter slots 16 of first the 1 st molar brackets 70 and then those of successive remaining ones of anterior brackets 10 . as the archwire 200 is pivoted to a plane generally parallel with the occlusal plane , it slides into respective bracket slot openings 24 along ramp 28 of lingual wall 20 against the bias of the respective leaf spring 32 ( or whichever retention device is being employed ). once the archwire 200 has been pushed sufficiently far into the archwire slots 16 , each leaf spring 32 will move back under its bias towards its rest position to retain the archwire 200 . the installation is the same for other types of archwires ( such as oval archwire 202 , rectangular archwire 204 and 5 - sided archwire 206 ). depending upon the dimensions of the archwire , leaf spring 32 will either push the archwire against lingual wall 20 and gingival wall 22 in order to seat it within slot 16 , or simply move all the way back to its rest position , enclosing but not forcibly seating the archwire within slot 16 . advantageously , there are no individual latches or clips to manipulate , as leaf spring 32 cooperates with archwire slot 16 to retract from slot opening 24 when force in a generally occlusal - gingival direction from an archwire is applied to leaf spring 32 . fig3 shows an enlarged perspective top - view of the 2 nd molar tube 90 and 1 st molar bracket 70 receiving archwire 200 . as can be seen , the convertible cap 74 is removed from 1 st molar bracket 70 during insertion of archwire 200 . fig3 a - 31 e show a round archwire 200 being installed into the self - ligating system 5 on a patient &# 39 ; s upper arch . the process is the same as insertion of an archwire on a lower arch , as described above . the convertible caps 74 are first removed from the two 1 st molar brackets 80 ( only one is shown for ease of understanding ), and the two ends of archwire 200 are inserted into respective 2 nd molar tubes 90 . once its ends are in the 2 nd molar tubes 90 , the arched archwire 200 is pivoted downwards generally about an axis connecting the two 2 nd molar tubes 90 to progressively enter slots 16 of first the 1 st molar brackets 80 and then those of successive remaining ones of anterior brackets 10 . as the archwire 200 is pivoted to a plane generally parallel with the occlusal plane , it slides into respective bracket slot openings 24 along ramp 28 of lingual wall 20 against the bias of the leaf spring 32 ( or whichever retention device is being employed ). once the archwire 200 has been pushed sufficiently far into the archwire slots 16 , each leaf spring 32 will move back under its bias towards its rest position to retain the archwire 200 . a clinician removes an archwire from the upper or lower arch of system 5 by grasping the archwire between the central brackets 10 and pulling down ( upper arch ) or pulling up ( lower arch ). as with installation , for removal , individual manipulation of latches or clips is not required , and the entire archwire may be removed in a single movement . in practice , using a weingart plier , a clinician clutches the archwire in the middle of its arch and pulls it , in a gingival to occlusal direction , out of the slots of the brackets 10 and 80 ( 70 ). fig3 a - 32 c are elevational side - views of an embodiment of the bracket 10 showing the successive stages of insertion into bracket 10 of a rectangular ribbon archwire 204 during installation in a self - ligating system 5 . as would be clear to one of ordinary skill in the art , removal of archwire 204 is effected in the reverse order as described above . the shape - memory properties of the nickel - titanium ( niti ) leaf spring can be employed to assist with insertion and removal of archwires . based on the relative amount of nickel to titanium , the niti leaf spring will have a transition temperature below which it becomes soft and pliable . as such , a clinician may slightly cool the spring in order to insert an archwire . when the spring becomes warmer that its transition temperature , it assumed its curved shape and can retain an archwire . in a similar manner , removal of the archwire may be facilitated by slightly cooling the spring below its transition temperature in order to make it soft and pliable . typically , the ni : ti ratio will be chosen such that the transition temperature of the niti leaf spring is around room temperature . it will be understood , particularly with reference to the accompanying drawings , that an additional benefit accruing from the embodiments of the present invention described herein is that , because the spring is within the slot and on its inside wall , it is for most practical purposes inaccessible by a patient and also not exposed to patient tissue . this has the advantage of making the system more comfortable than prior art self - ligating designs . while the spring has been shown in the described embodiments on the buccal / labial wall of the slot , it will be understood that the spring may be on , for instance , the lingual wall of the slot . although specific embodiments have been described and illustrated , those of skill in the art will appreciate that the variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims . for instance , slotted and wire leaf springs of various configurations have been shown to be particularly elegant and advantageous to the embodiments disclosed herein . however , it will be understood that other spring means such as combinations of coil springs or spring - cushioned ball bearings may function effectively to seat full - sized archwires into the archwire slot , while also being capable of functioning to retain archwires of a range of sizes in the archwire slot . furthermore , multiple springs of the same or other complementary configurations may be employed in order to achieve the functions described for the archwire retention device . the spring retention device may be received by the bracket in the lingual wall , rather than the buccal / labial wall of the slot . it will be understood that recess 33 may be formed such that it extends all the way through body 14 from slot 16 . this would permit leaf spring 32 to do the same or even extend beyond body 14 to some degree . in the case where leaf spring extends beyond body 14 , leaf spring 32 might be annealed and bent back downwards above the point at which it extends beyond body 14 , in order to hold it more positively in the bracket 10 . the leaf springs described herein have been formed of a shape memory alloy called nickel - titanium alloy . such a material is advantageous during manufacture , because when cooled , it is pliable and easy to insert into recess / recesses 33 and niche / niches 30 , and also may be cooled in order to facilitate insertion and / or removal of an archwire . when brought back up to body temperature range , the material reverts to its curved shape and assumes its springing properties . however , one of ordinary skill in the art would understand that , for instance , springs of different materials such as steel , chrome - cobalt alloy , titanium - molybdenum alloy , or molded shape - memory plastics would function , and relate to body 14 in much the same manner as described above . shape - memory plastics , however , are generally required to be warmed above a transition temperature ( rather than cooled below a transition temperature as with niti ) in order to become soft and pliable . as such , a clinician would warm the shape - memory plastic spring or springs in order to facilitate insertion and removal of an archwire . in the embodiments shown , the spring in its rest position obstructs about 60 % of the slot opening . this configuration is advantageous for ease of insertion of an archwire into the slot . during insertion , an archwire can abut the ramp and , because of the combination of partial obstruction and the shape of the spring , push the spring in a buccal / labial direction along the niche . however , within the scope of the invention are embodiments in which the spring could obstruct up to 100 % of the opening . it will be understood that configurations of less than 60 % obstruction may be used in some embodiments of the invention , providing that the functional aspects of the spring as a retention device are achieved . of particular note are cases where a shape - memory material is used for the spring , as the shape - memory material may be cooled ( or warmed as may be the case if shape - memory plastic ) to enable the archwire to enter / exit the slot without requiring the archwire to exert very much force on the spring against its bias during entry / exit . furthermore , while the smallest dimension of archwire retained by the retention device in the embodiments disclosed above is 0 . 014 inches , it will be understood that different situations and applications of the present invention may find need for configurations which permit retaining of smaller archwires . it is also conceivable that , depending on patient requirements or preference of the clinician , the archwire slot of the orthodontic appliance described herein may receive multiple archwires , as would be understood by one of ordinary skill in the art .