2007年03月05日
Recent topics on self-ligation orthodontic systems
Abstract
There has recently been a renewed interest in self-ligation orthodontic systems. This was triggered by the launch of Damon 3 with minor changes added to the Damon System, a representative passive self-ligation system. This paper will discuss characteristics, advantages and disadvantages of passive vs. active self-ligation systems through comparison with the SPEED system as a representative active self-ligation system and presentation of clinical cases. Particular emphasis will be placed on the three rediscovered aspects of orthodontics, i.e. self-ligation, low friction and light force. Various look-alike self-ligation systems incorporating these aspects will be introduced. The report will also describe the SPEED Appliance Technique and presents cases treated with the technique. Key words: SPEED Appliance, Self-ligation, Low friction, Light force Toshihisa YAMAZAKI DDS, PhD, Aoto Orthodontic Office
Introduction
There is a renewed interest in self-ligation in orthodontics, perhaps triggered by the launch of the Damon 3 bracket with minor changes to the original Damon system, a notable passive self-ligation system. Although the features and treatment procedures of self-ligation systems may look new, the basic self-ligation technique has evolved within the context of the straight wire technique. The basic philosophy behind this technique dates back further to the anchorage concept of the Tweed standard edgewise technique and the light-force concept of the Begg technique. These concepts have undoubtedly been passed on from one generation to another, contributing to the development of the self-ligation approach to orthodontic treatment. However, it is the advent of shape memory archiwires that has brought about the recent dramatic advances of self-ligation systems. This paper will introduce recent topics on self-ligation systems with a focus on the three aspects that have been revisited with renewed interest, namely self-ligation, low friction and light force.
Development of self-ligation systems
Self-ligation systems may be viewed as new developments, but the first self-ligation appliance was developed in the early 1930’s. The ones developed in the 1970’s and thereafter are still available today. All these systems have been promoted as having the advantages of decreased chair time, improved oral hygiene, lower risk of infection, reduced pain, longer interval between appointments and shorter treatment time. Modifications have been made to the self-ligation mechanism itself, as well as to the system as a whole with the introduction of archwires that capitalize on the characteristics of the system, during the last quarter century.
The first self-ligating orthodontic attachment developed is said to be the Boyd band/bracket introduced in 1933, though its further development was abandoned due to the bulkiness and high production cost1. Ford Lock came onto the market in the 1930’s, followed by the Russell appliance, Schurter device and Rubin device in the 1950’s, and Branson in 1966. None of these attachments are available today. All had passive mechanisms to hold archwires in place. The SPEED system developed in 1972 (Fig. 1) adopted a spring clip as the first active holding mechanism ever developed, an epoch-making invention. The SPEED system has been supplied and used in clinical practice to date.
The Edgelok bracket (passive mechanism, Fig. 2) developed in 1972 gave way to the Mobil-Lock bracket (passive mechanism, Fig. 3) developed in 1979. The Activa bracket (Fig. 4) developed in 1986 was well-known for some time as a low-friction bracket with a passive mechanism, but its production was discontinued. There have been successive launches of different self-ligation systems since 1990.
The Time bracket (Fig. 5) launched in 1995 has a rotational arm, similar to a spring clip, to hold archwires, though classified as a passive mechanism due to the stiffness of the rotational arm. This bracket is still available with a few modifications.
The Damon bracket (Fig. 6) developed in 1996 has recently drawn much attention as a passive self-ligation system. The bracket has undergone three model changes since the development of the original. The Damon 2 and Damon 3 brackets are available today. The latter was developed in 2004 and comprises a combination of composite resin and metal.
The TwinLock bracket (passive, Fig. 7), presently unavailable, adopted a sliding-door design similar to the Damon bracket by adding the fourth wall to an open edgewise bracket slot.
The In-Ovation bracket (Fig. 8) was developed in 2000 and has an active spring clip similar to that of the SPEED System.
The SmartClip bracket (Fig. 9), which was developed in 2004, is labeled as a passive self-ligating bracket despite the use of a nitinol clip to hold archwires.
Of six currently available self-ligation systems, two are active models (SPEED system and In-Ovation) and four are passive models (Mobil-Lock, Time, Damon 2 and 3, Smart Clip). In addition, there are lingual and translucent self-ligation systems, which will be discussed later.
Mechanisms and characteristics of currently available self-ligation systems
1. Active self-ligation systems
1) SPEED system
The SPEED system1-19 (Strite Industries Ltd., Fig. 1), a representative active self-ligation system, was developed more than 30 years ago. SPEED stands for Spring-loaded Precision Edgewise Energy Delivery.
The term ‘self-ligation system’ may carry a special connotation, but it is merely a pre-adjusted edgewise appliance with a self-ligation mechanism built in to retain archwires. The mechanism of self-ligation offers a major advantage of facilitating a low-friction, low-force treatment technique, as described below in more detail.
Structurally, the SPEED bracket is characterized by the built-in spring clip (Fig. 1-a). The clip opens and closes very easily to help reduce the chair time required for placement and removal of archwires, and increase the time spent for patient care. The SPEED bracket has many advantages, most of which are derived from the built-in spring clip. These include: 1) small size and improved hygiene, 2) ease of archwire change, 3) excellent control, 4) effective use of sliding mechanics, 5) a built-in auxiliary slot, and 6) shorter treatment time. The auxiliary slot is 0.016”×0.016” in dimension and useful when adding a hook or inserting a double wire. The action of the spring clip provides excellent control of tooth position without the use of an uprighting spring in the auxiliary slot. The mushroom hook on the bracket for the buccal segment causes little tissue irritation because of the round shape and is useful in placing an elastic or elastomeric chain.
The SPEED bracket has been modified in many ways over the years to maximize its advantages. The SPEED Wire (Fig. 1-e) developed concurrently with the SPEED bracket has a unique cross sectional configuration and provides superior torque control in conjunction with the spring clip. The Supercable Wire developed in 1993 (Fig. 1-d) is a 7-strand nickel-titanium coaxial wire that produces extremely light continuous forces, contributing to further development of the low-friction, light-force technique. The built-in spring clip was modified with a new material and a new window design. The 21st century super-elastic model of the SPEED bracket (Fig. 1-a) is made of NiTi instead of stainless steel with a 4-fold increase in elasticity. The new spring clip also has a labial window in the center for greater ease of opening and closing.
2) In-Ovation
The In-Ovation system (GAC International, Inc., U.S., Tomy International K.K., Japan, Fig. 8) is the only active self-ligation system besides the SPEED system. The bracket has a twin shape with a built-in cobalt-chrome clip. It is promoted as the only twin bracket with a built-in active spring clip, while the SPEED bracket has a single wing.
The product brochure of the In-Ovation system lists 11 structural advantages (Fig. 8). (A) The conventional twin-bracket design with four tie wings offers rotational control and versatile use of auxiliaries. (B) The cobalt-chrome active clip provides full slot coverage to gently seat the arch wire. (C) A horizontal auxiliary slot accommodates sectionals, uprighting springs and rotational springs. (D) Smooth rounded mini-posts provide versatility and comfort. (E) A slot blocker prevents the arch wire from escaping the bracket slot. (F) A rhomboid-shaped base facilitates bracket placement. (G) Metal injection molding allows for low profile design. (H) Torque-in-base permits level slot alignment. (I) CNC milling ensures precision and smoothness. (J) A compound contoured base gives a more anatomical fit. (K) An ID marker in the center of the slot facilitates placement orientation.
The brochure quotes the words of Dr. Raymondo C. Thurow from the Edgewise Orthodontics Journal to justify the twin-shaped bracket design. He states that a bracket 3.5mm wide will be suitable for bicuspids, cuspids and upper incisors in providing root control in the mesiodistal plane and in axial rotations. This implies that the Damon 2 bracket (Fig. 6-b), which also has a twin-shaped design but a shorter working span of 2.08 mm similar to the 1.8mm span of a single bracket, would not be as advantageous as the 3.8mm span of the In-Ovation bracket and GAC’s other twin brackets in mesiodistal root control or axial rotations.
The brochure also says that In-Ovation combines the rotational control of a conventional twin with an active clip for full control, while providing reduced resistance and that the horizontal slot allows the use of sectionals, uprighting and rotational springs. It is not difficult imagine that the horizontal slot was incorporated to give the same feature as the SPEED bracket. However, the addition of such a slot creates a disadvantage of increased bracket thickness. To avoid this problem, a low-profile version without a horizontal auxiliary slot is also available.
In-Ovation bracket is currently included in the GAC “R” Systems series and marketed as In-Ovation-R (Fig. 8b) with a rounded, low-profile design for patient comfort. The built-in spring clip was renamed to “interactive clip”, which not only spares the periodontium from detrimental effects of ligation but also serves as a cushion for the tissue according to the company.
2. Passive self-ligation systems
1) Mobil-Lock bracket (Fig. 3)
The Mobil-Lock bracket (1979) with precision opening and closing mechanism and refined structure took over the place of the Edgelock bracket (1972, Fig. 2), but its acceptance was limited partly due to its large size and partly due to the explosive spread of elastomeric ligature ties in the 1970’s. The two bracket systems have excellent designs that well represent the passive systems, equivalent to their active counterpart SPEED appliance. Both are still available, though seldom seen. The author made every effort to find information on these systems with little success. The 4th edition of the Graber textbook1 contains some design descriptions of these brackets.
2) Time bracket (Fig. 5)
The Time bracket (American Orthodontics) is a narrow twin-shape bracket with a spring clip and closely resembles the SPEED bracket in its external appearance. The opening and closing mechanism is similar to that of the Activa bracket with a rotational arm. This may be due to the stiffness of the spring clip with low elasticity and little flexibility. There is a small hole in the center of the labial (buccal) surface of the spring clip, into which a special instrument is inserted to rotate the spring clip open gingivally. This rotational arm mechanism is said to require ‘gentle rolling force’, much lighter opening and closing force than other self-ligation systems. The manufacturers demonstrates this with a graph showing that the Time 2 bracket needs the lowest opening and closing force, followed by SPEED, In-Ovation-R and Damon 3 in this order. The small hole cut into the spring clip for ease of opening and closing is so useful that it inspired the manufacturer of the SPEED bracket to make a minor change in the opening and closing mechanism. A small hole, called labial window, was incorporate into the SPEED bracket to facilitate opening and closing of the spring clip when the bracket material was changed from stainless steel to nickel titanium. The spring clip of the Time 2 bracket (Fig. 5-b), a modification of the original Time bracket, is advertised as an interactive ‘smart’ clip that is kind to the peridontium with rounded edges. The Time 2 bracket also has what is called torque rails to increase torquing efficiency at the final stage of treatment.
3) Damon 2 (Fig. 6-b) and Damon 3 (Fig. 6-c)
The Damon 2 bracket maintains the design standard of the Damon SL bracket (Fig. 6-a) while offering improved rotation and torque control. The bracket width is 35% narrower for patient comfort, which also provides better rotation and tip control because of the increased inter-bracket distance. The configuration of the slide was also improved for easier and more reliable opening and closing. The bracket slot becomes a complete tube when the slide is closed, increasing torque control. The manufacturer calls it the world’s best selling self-ligation system.
Damon 3, the third generation Damon bracket, was launched as an esthetic and reliable passive self-ligation system. Its design characteristics includes: 1) a combination of clear material and stainless steel to meet patient esthetic needs, 2) remarkably easy-to-use sliding mechanism to facilitate wire changes, 3) ultra-smooth contours and rounded edges for comfort, 4) slot with four solid walls to allow fast and controlled tooth movement, and 5) high-retention mechanical bonding base to assure strong, reliable bonding. According to the manufacturer, it has been clinically proven that a combination of passive self-ligation brackets, high-tech archwires and the low-friction, low-force Damon technique greatly simplifies treatment planning while providing superior control and treatment results to conventional orthodontic techniques.
4) SmartClip (Fig. 9)
SmartClip (3M Unitek) is said to have been developed as a self-ligating bracket that capitalizes on the features of the MBT System following more than four years of research and development. It has a typical twin bracket design with a Nitinol clip on each side of the bracket to retain the archwire. They call it a true self-ligating bracket. Special instruments are available for archwire insertion and removal, though archwire insertion can be accomplished with a simple push. Insertion force inevitably increases with an increasing wire size, but not to the extent that the patient complains of severe pain. For archwire removal, forceful pulling of the archwire is likely to cause the brackets to debond, necessitating the use of the removal instrument. Data suggests that higher stress is applied to the clips during archwire removal than during insertion. The removal instrument is rested against the gingival wings to pull out the archwire with a lever action. The instruments have recently been modified to facilitate archwire insertion and removal.
In addition to the advantages of extended interval between appointments and reduced patient discomfort, this passive self-ligation system is said to offer an additional advantage of allowing continued use of conventional techniques because of the familiar twin shape and structure. Despite the many advantages the manufacturer claims, the inter-bracket space is decreased by the clip placed outside either bracket wing, making it difficult to handle severely crowded or rotated teeth. The body of SmartClip is a stainless steel twin bracket, to which Nitinol clips are mechanically retained outside the bracket wings. It is most likely that this design was adopted to allow future integration of the clips with their esthetic ceramic bracket.
Benefits of low friction in self-ligation systems
Each self-ligation system has a unique archwire sequence designed to make the system passive, interactive or active depending on the stage of treatment. Thus, the level of friction will not remain constant throughout treatment.
1. Commitment to low friction
1) Origin of low friction
Tweed used single brackets. Needless to say, the slot size was 0.022”×0.028”. Despite a common misconception that twin brackets provide superior control of tooth positions, they may be only slightly more advantageous in correcting rotations and tips. Single brackets allows for increased interbracket distance, thereby providing good tip control through deflection of a larger size wire. For rotation control, Tweed used eyelets on anterior teeth and lingual cleats on posterior teeth.
The way Tweed achieved low friction had to do with the configuration of the archwire he used, which had rounded edgewise sides rather than a true rectangular shape. This archwire was made by press forming a round wire into a rounded rectangular shape to decrease the area of wire-slot contact to a point contact. Tweed used this archwire in combination with single brackets, resulting in low friction. In addition, he used the 0.022” slot size, which delivered light forces when small size wires were used. Thus, Tweed had already been incorporating low friction, light force mechanics into his technique when stainless steel was the only wire material available.
2) New ideas for bracket designs
The Synergy bracket (RMO, Fig. 10) has a triple-wing configuration, and all three walls comprising the bracket slot are curved to reduce the contact area between the archwire and slot for low friction. The bracket also offers ligation options to adjust the level of frictional force for rotation control. This feature appears to be very useful, since it allows initial rotation control, as well as adjustment of friction and control for a block of teeth or individual teeth during extraction space closure by sliding mechanics.
The Delta bracket (Ortho Organizers, Fig. 11) has a triangular shape as the name indicates. Like the Synergy bracket, it has a capability to adjust the level of friction and the magnitude of control with different ligation options. The Delta bracket is made of ceramic.
In conventional bracket systems, elastomeric ligature ties bind the archwire to the bracket, which becomes the most significant source of friction. In contrast, the brackets introduced above are designed in such a way that an elastomeric ligature grips the archwire outside of the bracket wings to eliminate undesirable binding. These brackets are also capable of tightly gripping the archwire for good rotation control when biding is desired. There are an increasing number of products based on similar ideas available to the market in efforts to minimize friction, though these brackets are not self-ligation systems.
3) Attachments for archwire ligation to create low friction
Clear Snap (Dentsply-Sankin, Fig. 12) is a clip type attachment for archwire ligation launched in 2004. This product was designed as a new method of ligation different from conventional stainless steel and elastomeric ligatures. The clip designed for use in combination with the Clear Bracket SL is made of a translucent white material for better esthetics that is less susceptible to discoloration, degradation and plaque accumulation than transparent elastomeric ties. It also provides the benefit of low friction, since it does not bind the archwire. The use of 0.010” or 0.012” Ni-Ti archwire is recommended for initial alignment with the Clear Snap system to produce a similar effect to self-ligation systems based on low friction and low force. The extra super-light power chain developed specially for this system has a thickness of 0.2mm and generates much lighter retraction force than the conventional 0.5mm thick power chain. It is most suitable for use with self-ligation systems. Neo-Clip (GAC, Fig. 13) is similar to Clear Snap and specially designed to fit their own ceramic bracket. This product is not available in Japan. Slide (Leone, Fig. 14) is an elastomeric tie which remains passive without binding the archwire outside of the bracket wings. It is similar to a figure-eight tie but has a much wider crossing to keep the archwire more stable.
All these new ideas are intended to achieve low friction with conventional bracket designs.
2. Low friction vs. control in active self-ligation systems
1) SPEED System (Fig. 1)
Most of the self-ligating brackets developed so far have non-active mechanisms with where the fourth wall is closed with a sliding door to retain the archwire in the slot. When the door is closed, the slot becomes a tube. In conventional non-self- ligating systems, the archwire is tightly held to the bracket with ligature ties, which produces friction. Whenever the archwire is tied, friction is unavoidable, though the level of frictional force differs depending on the type of ligature (stainless steel vs. elastomeric ring) or tie (0 vs. 8) used. Friction also depends on the size relationship between the bracket and archwire. The thinner the archwire is, the lower the friction becomes. A small size wire placed in a self-ligating bracket allows the wire to slide freely with little frictional resistance. The SPEED bracket, one of the few active self-ligating brackets available on the market, retains the wire with a resilient spring clip. Berger4 verified in 1990 that this spring clip mechanism produces much less friction than with a stainless steel or elastomeric ligature on an edgewise bracket.
In the SPEED System, the seven-stranded nickel titanium coaxial wire Supercable17 (Fig. 1-d) that generates extremely light forces is used in the initial aligning stage. A combination of the SPEED bracket and this wire constitutes a virtually friction-free system where the anterior teeth are kept from flaring by lip support while being aligned with super-light orthodontic force. The posterior teeth are aligned spontaneously as they migrate into extraction space. This eliminates the need for a separate cuspid retraction stage to create space in moderately crowded cases. In severely crowded cases, the Supercable wire can be used as a double wire11,12 in the auxiliary tube of the SPEED bracket to unravel crowding while creating spaces for alignment of displaced teeth. In non-extraction cases, arch expansion can be accomplished with the double wire while controlling anterior flaring of the anterior teeth. Initial alignment can be completed in 6 to 10 months in late mixed dentition and approximately 3 months in adults6-8.
The prime feature of the SPEED bracket is the built-in spring clip. When the archwire is placed in the slot of the SPEED bracket on a malpositioned tooth, the spring clip is deflected by the force of the wire. This allows the wire-bracket relationship to return to the correct “home position” (Fig. 15), which brings the tooth into the arch. The energy stored in both the resilient spring clip and archwire (Fig. 16) is gradually released to initiate tooth movements. Thus, the active SPEED system controls the spatial relationship between the archwire and bracket, which is the greatest advantage of this system.
The author measured the interaction between the archwire and spring clip in an experimental model17. The experiment with 1 to 3mm of lateral incisor displacement (Fig. 17) showed that a combination of a Ni-Ti round wire and the SPEED bracket produced significantly higher forces on the teeth adjacent to the lingually displaced lateral incisor than a combination of an edgewise bracket and the same wire when the amount of displacement was 1mm. This can be attributed to a large spring-back action of the Ni-Ti round wire and deflection of the spring clip of the SPEED bracket. The same effect was observed with 1mm lateral incisor displacement when the Supercable wire was used in place of the Ni-Ti wire.
The three-point bending test the author conducted also clearly demonstrated the effect of the spring clip (Fig. 18). It is well known that a shape memory alloy wire shows hysteresis during loading and unloading in a bending test. The unloading curves observed with the SPEED bracket were completely flat, indicating that a constant level of orthodontic force is sustained over time. In the other experiment, the force vectors generated with 1mm lateral incisor displacement were larger than those with 2mm displacement when the Supercable wire was used. These findings cannot be explained only by the relationship between wire deflection and force level, suggesting the effectiveness of the spring clip of the SPEED bracket in controlling tooth positions.
Fig. 19 shows the correction of mesial rotation of the upper first molar with the SPEED system. The molar was moved to a good rotational position in 2.5 months with the use of 0.016” Supercable wire followed by 0.016” Ni-Ti wire. Not only does the SPEED system provide an efficient rotational control, but it also minimizes molar anchorage loss during space closure with sliding mechanics by retaining the wire in the home position of the bracket (Fig. 15). Therefore, no additional anchorage is required when the SPEED system is used. Furthermore, space closure by sliding mechanics can be accomplished with very light forces because of the low-friction design of the SPEED bracket, which also saves molar anchorage. In space closure, the molars are pulled mesially as the anterior teeth are retracted, and begin to rotate mesially. With the use of heavy forces, this initial change would continue without recovery and cause mesial movement of the molars. The SPEED bracket has a built-in mechanism to constantly correct this mesial molar rotation, making the molars less susceptible to anchorage loss. Thus, the SPEED system requires no anchorage reinforcement with a headgear, Nance holding arch or transpalatal arch.
The SPEED archwire (Fig. 1-e) has a unique configuration in cross section with a rounded labio-gingival corner. The archwire was developed concurrently with the SPEED bracket to produce effective torque control in synchrony with the built-in spring clip in the final stage of treatment.
In summary, the SPEED system functions as a low-friction system with the help of the resilient spring clip in the initial stages of treatment and as a more active system with the spring clip increasing its active control in later stages, thus taking full advantage of the spring clip action throughout treatment.
2) In-Ovation® (Fig. 8)
In-Ovation® has recently been remodeled to In-Ovation-R (GAC, Fig. 8-b) along with the renaming of the built-in spring clip to “Interactive Clip”, which strongly emphasizes the feature of interactive force. GAC has an archwire system called BioForce. Generally, orthodontic suppliers develop archwires and adhesive materials to go with their brackets and combine them into a system, which makes sense for business reasons. In addition, each bracket has a unique bonding base, which should ideally be bonded with an adhesive optimally designed for the base. Indeed, forerunners of many orthodontic suppliers were well versed in adhesives.
Going back to the topic of BioForce, the manufacturer says that the archwire is designed to deliver ideal orthodontic forces for histological movement of the crowns and roots. It generates progressive forces from the midline to the molars without the application of excessive forces to the roots. BioForce corrects rotations through delivery of interactive and gentle torquing forces.
The manufacturer also refers to various combinations of the In-Ovation-R bracket and BioForce archwires. The bracket creates a passive mechanism that delivers low forces when combined with the round archwire. The bracket becomes interactive when combined with the mid-size square wire, and provides full control by active mechanism in combination with the full-size rectangular archwire.
3. Low friction vs. control in passive self-ligation systems
1) Activa (Fig. 4)
The Activa bracket (‘A’- Company) was manufactured in the latter half of the 1980’s to simplify the sliding mechanics, which gained popularity then, through the introduction of self-engating mechanism. The company explains that the mechanism also contributed to the reduction of frictional resistance, allowing faster tooth movements. Irwin Pletcher, the developer of this passive, low-friction bracket, says that reduced friction means lighter forces required for tooth movements, which provides a direct benefit to the patient. He also stresses the importance of eliminating factors causing the wire to bind in sliding mechanics. Recent studies demonstrated that friction was reduced using ligatureless brackets with metal-to-metal contact to approximately one half of the friction produced with conventional ligated brackets. Sims et al20 showed in their study on friction in sliding mechanics that the level of friction was the lowest with the Activa bracket and that friction was much less with the SPEED bracket than stainless steel twin brackets tied with elastomeric, 0 or 8 ties. Kemp21 and Weiss22 demonstrated that friction was reduced with the self-ligating Activa and SPEED brackets compared with conventional tied brackets, particularly when the tip was 0°. They also showed that the presence of 10°tip between the bracket and archwire increased friction to the same degree for these self-ligating brackets as conventional tied brackets. Pletcher points out that tip and torque cause binding between the bracket and archwire and that good archwire engagement during the rectangular wire stages of the straight wire technique would easily solve this problem. He says all these factors allow the Activa bracket to produce precise and rapid tooth movements.
2) Time bracket (Fig. 5)
The Time bracket has a rotational arm for opening and closing, similar to that of the Activa bracket, and therefore is categorized as a passive self-ligation system. The spring clip of the Time 2 bracket (Fig. 5-b) is described as an interactive “smart” clip and may be more appropriately classified as an active, rather than passive, system since the clip function as a passive ligation mechanism during initial round-wire stages and becomes interactive with the archwire during rectangular wire stages for torque control. The manufacturer says that smaller wires slide easily within the slot of the Time 2 bracket during leveling and unraveling because of low friction. They criticize that a passive self-ligation bracket can function only as a low-friction system with poor control of torque and rotation subjecting the orthodontist to frustrating challenges in the final stage of treatment. They go on to say that the Time 2 interactive “smart” clip presses the archwire toward the corners of the slot, allowing full expression of torque and enhancement of rotation control.
3) Damon 2 (Fig. 6-b) and Damon 3 (Fig. 6-c)
Three active treatment steps using three archwires are proposed for treatment with the Damon 2 (Fig. 6-b) and Damon 3 (Fig. 6-c) brackets. In the initial step, a small dimension archwire (0.013” Damon Copper Ni-Ti or 0.014” Align SE Ni-Ti) is used to “apply just enough force to stimulate cellular activity without crushing the vascular supply in the periodontium”. This stimulates biocompatible, efficient tooth mvement23, reduces patient discomfort, and shortens treatment time for adults close to that for children. The perioral muscles, particularly the obicularis oris and mentalis, prevent the incisors from flaring as the anterior teeth unravel into extraction spaces. Arch form expansion takes place buccally and posteriorl in non-extraction cases and constricted arches. Damon describes these phenomena through many treated cases. He also demonstrates how the alveolar process is reformed and expanded using CT images24.
The next step is aimed at eliminating all rotations using 0.016”×0.025” Align SE Ni-Ti wire. Because of the importance of having 0.002” to 0.003” play between the archwire and slot for rotation control, the slot depth of the Damon bracket has been reduced to 0.027”. Rotation control needs to be completed in this phase of treatment to give adequate time for settling of the corrected teeth. Failure to do so and repeating rotation control in the final stage of treatment would compromise the stability of end results.
In the third step, a 0.019”×0.025” pre-posted stainless steel wire is used for space closure with sliding mechanics. Well-aligned bracket slots maximize the effect of sliding mechanics. Ni-Ti closed coil springs and Alastics are used for retraction and placed carefully to avoid gingival irritation and poor oral hygiene. This is clearly important for good blood supply needed for bone remodeling. Damon does not limit the definition of sliding mechanics to space closure but uses a wider definition in emphasizing the advantages of the passive self-ligation system. He stresses the need and importance of passive relationship between the bracket slot and archwire in correcting all kinds of orthodontic problems such as high cuspids, in-out discrepancies, curve of Spee and arch form.
Thus, the Damon system is actively promoted as a passive self-ligation system. The brochure states in the section on superior tooth control that the Damon system provides full control with full engagement of a full size 0.019”×0.025” archwire in the 0.022”×0.027” slot.
4) SmartClip™ (Fig. 9)
The SmartClip system is simply described as a passive self-ligation system with dramatically reduced friction. The archwire sequence is the same as the MBT system, consisting of 0.016” heat-activated Nitinol, 0.019”×0.025” heat-activated Nitinol and 0.019”×0.025” stainless steel wires.
Light force technique with a self-ligation system and its effects
All self-ligation systems take advantage of their low friction design properties to achieve efficient tooth alignment in the initial stages of treatment.
1. Auto-alignment
All self-ligation systems are reported to provide efficient initial alignment of teeth. This is also supported by clinical data. Whoever has experienced a combination of low friction and light force will be stunned and excited with the efficiency of initial alignment, opening up a new vista of orthodontic tooth movement.
Light force prevents the incisors from flaring with the help of lip pressure. In extraction cases, the anterior teeth move into extraction spaces as the small dimension archwire slides through the bracket slot with minimal friction, eliminating the crowding. Woodside calls this process auto-alignment. No archwire adjustments are needed. The orthodontist simply has to watch with patience. In the meantime, a labially displaced high cuspid comes down and moves back to give room for the lateral incisor. Otherwise, the cuspid is pushed into extraction space as the lateral incisor is brought into the arch. In either case, crowding is eliminated in 2 to 3 months as the anterior teeth move into extraction spaces without the posterior teeth moving mesially. In non-extraction cases, constricted arches are expanded and molar rotations are corrected.
2. Control vs. guide
No special technique is required to induce the above described initial changes with a self-ligation system. A combination of any self-ligation system and light force would produce these changes. It is not the skills of the orthodontist that control tooth movements. The author is using the term “control” less and less, since the teeth are guided into position by low force.
3. Supercable
Supercable, a 7-strand Ni-Ti coaxial wire, was developed for use in combination with the SPEED bracket in 1993 by Hanson, the developer of the SPEED system, based on his treatment philosophy of using light force. The author demonstrated that the 0.016” Supercable wire placed in the 0.022” slot of the SPEED bracket produces 60-70g of continuous force in correcting 1 to 3mm of lateral incisor displacement (Fig. 18). The level of force produced with this combination is far lighter than what has been traditionally regarded as light force and is therefore called minute force. The teeth are guided and auto-aligned into place with the combination of low friction and minute force. Fig. 20 shows a case treated with minute force of the Supercable wire to illustrate the concept of auto-alignment. The patient, a girl in early permanent dentition, had previously been treated elsewhere by non-extraction approach. The orthodontist had finished active treatment without waiting for the eruption of the second molars. The posttreatment panoramic radiograph revealed horizontal impaction of both lower second molars. The new orthodontist who took over this case extracted the lower third molars and placed tubes on the buccal surfaces of exposed lower second molars. He patiently waited with the 0.016” Supercable wire in place. The impacted molars were uprighted significantly as the roots were moved mesially in approximately 6 months, and uprighted completely with subsequent use of a 0.016 Ni-Ti wire.
4. 0.014” Align SE Ni-Ti or Damon CU Ni-Ti
The 0.014” Align SE Ni-Ti and 0.014” Damon CU Ni-Ti wires are excellent archwires. Only one size is available and can be used for either upper or lower arch. Their arch form is larger than a regular arch form and is expanded posteriorly. The Damon philosophy disregards cephalometric hard-tissue criteria and stresses the importance of soft-tissue symmetry. Damon says that the passive structure of the Damon system allows low forces to work in conjunction with the muscles of the face, tongue, bone and tissue and that many cases can be treated to a symmetrical facial result without high-force expansion or extractions.
The case the author treated using the SPEED brackets and 0 .014” Damon CU Ni-Ti wire (Fig. 21) also showed marked improvement in arch form symmetry through arch expansion. The patient had constricted upper and lower arches in addition to asymmetry of the upper arch. Her treatment began with the placement of the 0.022” slot SPEED brackets and insertion of the 0.016” Supercable wire as an initial wire. The initial wire was used for 3 months, followed by 2 months of the 0.014” Damon CU Ni-Ti wire. Both arches were expanded and re-aligned in 5 months. Symmetrical arch form was obtained with an increase in the arch width between the buccal cusps of the upper first bicuspids from 35mm to 40mm.
5. Supercable vs. Damon CU Ni-Ti
A combination of the Damon 3 bracket and 0.014” Damon CU Ni-Ti wire is certainly very effective. Fig. 22 shows a case treated with this combination. Dramatic changes occurred in only 34 days. However, patients often complain of pain when treated with this combination. Orthodontic treatment is always associated with some pain at the beginning of tooth movement even when light forces are used. In the author’s clinic, the orthodontist or staff calls each patient soon after appliance placement, on the following day as much as possible and within 3 days at the latest. The pain threshold or ability to endure pain varies from one patient to another. Very few patients never complain of pain. Most patient respond positively by saying “bearable”, “able to eat”, “no problem” and “very little pain”. However, many of the patients who had the 0.014” Damon CU Ni-Ti wires placed complained of pain in the author’s and staff’s experiences.
In contrast, the combination of the 0.018 Supercable wire and Damon 3 bracket is often associated with less pain (Fig. 23). This combination also comprises a friction free system and offers rapid initial alignment in approximately 3 months (Fig. 24, Fig. 25, Fig.26). A 0.013 Damon CU Ni-Ti wire has recently been launched and added to the Damon system. Damon himself admits that the 0.013” wire is kinder to the tissue. This seems to imply that slightly heavier forces produced by the 0.014” Damon CU Ni-Ti wire give rise to various adverse reactions including pain.
The author uses the 0.014 Damon CU Ni-Ti in combination with the SPEED bracket, because of the effectiveness of the wire in arch development, only as a second wire following 2 to 3 months of the Supercable wire to minimize pain.
6. In-Ovation-R
A Class I crowding case in early permanent dentition was treated with a combination of the In-Ovation-R bracket and Supercable wire. The initial wires were 0.016” Supercable for the upper arch and 0.018 Supercable for the lower arch (Fig. 27-a). The upper second molars were partially erupted, and the lower second molars were tipped mesially due to early loss of the first molars. A decision was made to extract the upper first bicuspids only. The teeth were aligned using light intermaxillay triangular elastics with the apex of the triangle positioned at the upper cuspid. Auto-alignment of the upper teeth into extraction spaces was achieved in 3 months without the flaring of the anterior teeth. In the lower arch, uprighting of the second molars and rotation corrections progressed smoothly (Fig. 27-b). Although the interbracket distance is slightly reduced with the In-Ovation-R bracket due to an increased bracket width compared with the SPEED bracket, there is no major difference in effectiveness. The patient was able to maintain good oral hygiene around the appliance.
7. Time
The spring clip of the Time bracket rotates open gingivally, while that of the SPEED bracket opens toward the occlusal surface. As a result, the archwire enters the slot from an entirely different direction with the Time bracket than with the SPEED bracket. To compare the two, a case was treated by split-mouth design using the Time brackets on the left side of the mouth and the SPEED brackets on the right side from cuspid to cuspid in the upper arch and from first bicuspid to first bicuspid in the lower arch (Fig. 28). In the latter half of the treatment, the 0.020”×.025” Ni-Ti SPEED wire with a rounded labio-gingival corner. The spring action of the Time bracket produced friction in the area where the bracket contacted the wire. Although there seems to be no problem with the use of a large-size rectangular wire in conjunction with the Time bracket, this comparative study revealed that the SPEED wire should be placed upside down when placed into the Time bracket. The time bracket showed a similar effect in initial alignment of the teeth to other self-ligation systems.
8. SmartClip
SmartClip follows the same archwire sequence as the MBT system, using the 0.016” heat-activated Nitinol wire as an initial archwire. Initial alignment progresses at an adequate speed by Week 7 (Fig. 29). However, because of a narrow interbracket space, wire insertion is more difficult in areas where adjacent teeth are in close proximity due to severe crowding or rotations. This causes the wire to be slightly deformed when forced into each slot. In this male patient, a new archwire was placed at Week 3. By Week 7, rotations of the buccal teeth were improved enough to allow the placement of the 0.016”×.022” heat-activated Nitinol wire.
9. Clear Snap
The Clear Snap is a clip-type ligation attachment. Simple placement of this clip on the clear bracket creates a friction free state. With the use of a 0.010” or 0.012” Ni-Ti archwire, the combination of the Clear Snap and clear bracket produce the effects of auto-alignment and pain reduction similar to self-ligation systems. The manufacturer calls this method a super light force technique.
Fig. 30 shows the progress of a non-extraction case treated with this system. Initial alignment was completed using a 0.012” Ni-Ti archwire for only 2 months. In the upper arch, a 0.016”×0.022” Ni-Ti gold archwire could be placed.
Fig. 31 shows the use of the 0.014” Damon Align SE Ni-Ti wire in combination with this system. The case is a transferred retreatment case. Marked changes occurred in 2 months. The friction free system provided by the Clear Snap took full advantage of the Damon archwire, which guided each individual tooth into good alignment. The upper and lower arches were reshaped as the upper arch was expanded and as the lower molars were uprighted. Thus, occlusal improvement was accomplished efficiently, only in 2 months.
Lingual self-ligation systems and translucent self-ligation systems
These brackets and attachments are very valuable for patients seeking esthetics, but each patient should be fully informed of their disadvantages as well. The author is often asked about the use of esthetic brackets by his colleagues. They say, “Metal brackets are so visible that some patients find them unacceptable, and these patients want treatment with less visible brackets. The SPEED bracket, a metal bracket, would give you a disadvantage in this regard.” They express mixed feelings of admiration and sympathy about my patients’ acceptance of the metal bracket. The fact that the SPEED bracket is a metal bracket is not a hindrance at all. Patients should be educated about treatment objectives, namely, fast and high quality treatment without relapse. The author shows each patient both metal and esthetic brackets and explains differences between the two. The only advantage of esthetic brackets is that they are less visible. Metal brackets are superior in all other aspects. Esthetic brackets has many disadvantages such as being bulky, ease of breakage and wear, longer chair time, greater compromise in treatment results, and discoloration and uncleanliness of clear elastomeric ties. The patient is then informed of advantages of the SPEED bracket over other metal brackets from a self-ligation standpoint; much shorter treatment time, reduced pain, outstanding treatment effect and great end results. Given these explanations, most patients choose the SPEED appliance in the author’s clinic.
1. Evolution SLT bracket (Fig. 32)
The Evolution SLT bracket (Adenta) is a lingual version of the Time bracket. An individual transfer cap and a smart jig are attached to the bracket for bracket positioning and transfer to the lingual surface of each tooth. The opening and closing mechanism called interactive spring clip is the same as the rotational arm of the Time bracket.
2. Use of the SPEED bracket for lingual treatment (Fig. 33)
The author has been using the SPEED bracket for lingual treatment of the lower anterior teeth in retreatment cases with moderate crowding. Post-orthodontic crowding of the lower anterior teeth seen in many cases should more appropriately be defined as late-onset crowding rather than recurrent crowding. Many adult patients are concerned with moderate crowding in the lower anterior area but do not want appliance therapy. A lingual approach is a good choice for these patients. The SPEED bracket is a single width bracket and therefore more applicable to lingual treatment of the lower anterior teeth than wider brackets. The spring clip has recently been modified with a change in the material to Ni-Ti and addition of a labial window for ease of opening and closing even on the lingual side. However, precise bracket positioning on the lingual surface is more difficult, often necessitating archwire bending. Rectangular wires cannot be used since the torque prescription is not for lingual use.
3. Oyster ESL bracket (Fig. 34)
The Oyster ESL bracket (Gestenco) was launched as the world’s first metal free self-ligating bracket system. At the time, metal allergy came under close scrutiny and gold-plated brackets were introduced to the market The Oyster ESL bracket retains the archwire with a snap-on cap. Although the copolymer material is resistant to discoloration, it limits the types of archwires used to only soft wires such as superelastic and beta-titanium wires. According to the manufacturer, the archwire can slide in the slot freely since it is not tied with an elastomeric ligature. This system is also promoted as kind to the oral tissue without conventional ligation.
4. Opal bracket (Fig. 35)
The Opal bracket (Ultradent) is promoted as a low friction, passive self-ligation bracket made of a translucent nickel-free glass filled material. The bracket is highly resistant to staining and fracture and has a single-piece design. The manufacturer says that the self-ligating mechanism realizes more efficient tooth movement and reduces pressure to the teeth, and expects that the esthetic and smooth surface structure matching the tooth enamel will offer patient satisfaction.
5. Clear Button (Fig. 36)
The Clear Button (DENTSPLY-Sankin), developed for use in conjunction with the Clear Snap system, is a button that resembles a bracket. It is an attachment with a horizontal tube and without opening and closing mechanism. The button is intended for temporary use with a wire in severely crowded areas.
What can be done with the SPEED system?
Various types of cases will be presented below. The author aims to complete treatment in 1.5 years regardless of the type of malocclusion, patient age and sex, and choice of extraction. Extraction treatment takes somewhat longer in adults than non-extraction treatment, while there is no difference in treatment time between the two approaches in growing children. Class I crowding cases can be treated fastest, within one year in many cases. The fastest case so far is an adult Class I crowding case treated in 8 months. Fast treatment with unstable results makes no sense. Cses treated with the SPEED system remain stable for a long time post treatment, which are attributable to all the benefits of the self-ligation system described in this paper.
Case 1: Class II div. 1 non-extraction mixed dentition (Fig. 37A-C)
Treatment was initiated with upper and lower 0.018” Supercable wires. Four months and one week into treatment, the 0.020”×0.025”stainless steel SPEED wire was placed to stabilize the lower arch for anchorage. Three weeks earlier or 3 months, 2 weeks into treatment, 2.5 ounce (80g) Class II elastics were started. This was followed by unilateral vertical elastic wear for 2.5 months to stabilize the occlusion. The appliance was removed in 8 months, 3 weeks. The molar relationship was improved to super Class I. The occlusion remained stable throughout the retention period, and stability is still maintained 2 years, 8 months after the end of treatment. Damon states that the Damon system with the use of the 0.014” Damon Cu Ni-Ti wire produces positive changes as the arch develops. Similar changes occur with the SPEED system as well. In the present case, both the upper and lower arch widths between the first bicuspids increased 6mm with treatment and returned 1mm during retention.
Case 2: Adult Class II div. 1 non-extraction (Fig. 38 A-C)
The patient presented with severely proclined upper anterior teeth and full-step Class II molar relationship. Upper molar extraction was out of consideration since four third molars had already been removed. She had a good profile, upright lower incisors (FMIA of 66.5°) and FMA of 19.5°. Given the options of upper first bicuspid extraction and non-extraction, the patient chose the latter and agreed to cooperate.
The author generally moves two teeth at a time when distalizing posterior teeth. This can be accomplished with the low friction feature of the SPEED appliance that facilitates sliding mechanics. This method is a modification of the original step to move one tooth at a time described in the SPEED users’ guide and textbook1.
Once the upper and lower teeth are well aligned and the lower arch receives a full-size 0.020”×0.025” stainless steel SPEED wire, a dual-dimension archwire is placed in the upper arch to initiate molar distalization with Class II elastics. An elastic force of 2.5 to 3 ounce (approximately 70 to 85g) is adequate. The SPEED system has a dual-geometry archwire, 0.021”×0.021” square in the anterior section and 0.020”round in the posterior section. For this patient, the author fabricated a dual-dimension arch consisting of a 0.020”×0.021” stainless steel incisor section for full control of the incisors and 0.020” round SPEED wire from the cuspid posteriorly with a brass wire post soldered at the joint on each side.
For molar distalization, a Ni-Ti open coil spring (50g or 100g) is threaded between the first bicuspid and first moar to distalize the first molar. No bracket is placed on the second bicuspid. The second molar is pushed distally by the first molar.
For bicuspid distalization, a stop is placed mesial to the first molar bracket upon completion of molar distalization, and a Ni-Ti open coil spring is then placed between the cuspid and first bicuspid. There is no need to bracket the second bicuspid since the first bicuspid pushes it distally. The patient is required to wear Class II elastics full-time.
Cuspid and incisor retraction is started upon completion of bicuspid distalization. The coil spring is removed and a Class II elastic is placed directly to the hook of the cuspid bracket to retract the cuspid. Another Class II elastic is placed to the post on the archwire to retract the incisors simultaneously.
For occlusal stabilization, the second biscuspids are bracketed and the archwire is extended to the second molars and cinched back at the distal of the second molar (the author bends the end of the wire inward rather than toward the gingiva). This is to prevent space opening. A full-size 0.020”×0.025” stainless steel SPEED arch is used for finishing. A vertical elastic is placed in the cuspid area in addition to a Class II elastic.
Active treatment time was 19 months with good patient compliance for Class II elastic wear. Facial improvement and adequate retraction of the upper anterior teeth were achieved. The profile has settled and looks more natural 3 years, 3 months after treatment.
Case 3: Adult Class II div 2 upper first bicuspid extraction (Fig. 39-A, B)
The patient had a deep bite with severely retroclined upper incisors and full-step Class II molar relationship, a typical Class II div 2 case with a good facial profile. Class II div. 2 malocclusions are generally treated by non-extraction or extraction in the upper arch only if extraction is indicated. Extraction in the lower arch is contraindicated due to a difficulty of moving the lower molars mesially and a risk of further retracting the lower anterior teeth and creating a dished face. Extraction of the lower second bicuspids for correction of full-step Class II molar relationship would necessitate the closure of all extraction spaces by mesial movement of the molars. The patient was an adult with restorations on the lower posterior teeth. A decision of treating the lower arch by non-extraction was made for the purpose of leaving as many as teeth in the lower arch as possible and shortening treatment time.
Treatment began first in the upper arch. Two ounce (approx. 60g) intra-arch elastics were worn to help the aligning process from the time of 0.016” Supercable wire placement as an initial archwire. By the time the appliance was placed in the lower, the upper arch was nicely aligned. Treatment progressed to the point where upper and lower archwires became parallel to each other at 15 months, so that the upper molars could be moved mesially with Class III elastics into a stable occlusion. Harmonious facial profile and good occlusion were obtained after 19 months of active treatment. The occlusion remains stable 6.5 years out of treatment.
Case 4: Class III non-extraction open-bite permanent dentition (Fig. 40-A, B)
The patient had an overjet and overbite of 0.5mm and -1.5mm, respectively. Initial archwires were the 0.018” Supercable wires for both arches. Three ounce (approx. 85g) vertical elastics were worn in the cuspid areas from the beginning of treatment. The effect of the vertical elastics began to show in 2 months, and the same elastics were continued to maintain the overbite while sequentially increasing the wire size and stiffness.
Treatment progress enough to place both upper and lower 0.020”×0.025” stainless steel SPEED wires at 8 months. Lower posterior brackets were removed first to allow the occlusion to settle. The vertical elastics in the cuspid area were continued throughout treatment.
A good occlusion was obtained with proper overjet and overbite in 14 months of active treatment. Occlusal radiography revealed little root resorption in the upper anterior area.
There may be a concern with possible root resorption caused by a long-term use of vertical elastics. Light intermaxillay elastics would not cause root resorption unless used for an extended period of time. However, it is prudent to take precautions against root resportion in the upper incisor area such as wearing the elastic in the cuspid area from the very beginning and wearing it from the post soldered on the archwire.
Case 5: Adult Class III non-extraction (Fig. 41-A, B)
The mandible could be manipulated into a slightly more posterior position prior to treatment. Upper and lower 0.020” Supercable wires were used as initial archwires, followed by 0.017”×0.022” heat-activated Nitinol wires after 3 months. The bite was jumped by adding an extra length to the archwire. Upper and lower full-size 0.020”×0.025” stainless steel SPEED wires could be placed at 10 months and used for 6 months for stabilization. Active treatment was finished in 16 months.
Case 6: Adult Class I extraction with anterior crossbite (Fig. 42-A, B)
The lower anterior teeth were severely proclined. The upper lateral incisors and lower first bicuspids were extracted because of severe caries affecting the upper left lateral incisor. A three ounce (approx. 85g) intra-arch elastic was placed from the hook of the lower cuspid bracket on each side of the arch from the beginning of treatment to help align the teeth. The upper archwire was changed to the 0.020”×0.025” Ni-Ti SPEED wire at 6 months. A 0.020” stainless steel round wire was inserted in the lower to retract the anterior teeth into a positive overjet with 3 ounce intra-arch elastics and intermaxillary elastics by using the upper arch for anchorage. A good occlusal relationship was obtained in 16 months of active treatment.
Case 7: Adult skeletal Class III extraction with anterior crossbite (Fig. 43)
The final case, a borderline non-surgical case without functional shift of the mandible, was treated by lower first bicuspid extraction. Nineteen months of active treatment led to the establishment of a good occlusion.
Summary
Various types of self-ligation systems have been launched and many of them are currently available. These systems more or less share the same advantages such as reduced chair time, good infection control, friendliness to the periodontium, reduced pain, increased appointment interval and shorter active treatment time. The act of ligation with ligature wires, elastmeric ligatures and other attachments can be eliminated, providing opportunities for increased efficiency. The biggest advantage of self-ligation would be reduced chair time. Berger and Byloff25 demonstrated that the amount of time required for removing old ties and placing new ties from second bicuspid to second bicuspid in both arches, 20 ties in total, was only over 50 seconds as opposed to over 200 seconds for elastomeric ligatures, a 4-fold difference. Ligation with steel ligatures took approximately 4 times longer than with elastomeric ligatures. They also reported that the Damon SL, TwinLock and Time self-ligating brackets saved an enormous amount of time compared with elastmeric ligatures, though inferior to the SPEED bracket. The brochure of the SPEED system shows the amount of time saved with self-ligation vs. elastomeric ligation. In an orthodontic office with 25 patients a day, the saving of 150 seconds per patient translates into a total of 3,750 seconds or 62.5 minutes a day. Approximately one hour of chair time can be saved each day. Another advantage of self-ligation lies in infection control since no pig tail is required. Pig tails may stick the operator’s finger and injure the lips or buccal mucosa of the patient. Oral hygiene Elastomeric ties collect plaque, compromising oral hygiene. Self-ligation is friendlier to the periodontium.
The level of friction depends on the type of self-ligation and wire size. The same self-ligation system can be passive, interactive or active depending on the size of the archwire used and the stage of treatment. Thus, the level of frictional force does not remain the same throughout treatment even within the same system.
All self-ligation systems are basically passive and therefore have low friction during initial alignment. They change to interactive control in the stages of space closure, cuspid retraction and molar distalization by sliding mechanics, and then become more active with increasing wire size in the final stage of ideal tooth positioning.
Orthodontist have no difficulty producing the seemingly opposite effects of promoting initial alignment and reducing reciprocal action by taking full advantage of light force and low friction features of self-ligation systems in the initial stages of alignment. This provides patients with the benefits of pain reduction and comfort.
There is nothing special about a self-ligation system. It is simply a pre-adjusted edgewise appliance with the mechanism of self-ligation to hold the archwire. The mechanism of self-ligation saves the orthodontist from the laborious work of tying the archwire into each bracket slot, in addition to many other advantages. One of the concerns expressed about pre-adjusted appliances is the setup of brackets and archwires based on average values, that is, a lack of personalization. The concept of “one size fits all” implies that it fits no one. The author thinks it is the play between the archwire and bracket slot that allows personalization. The interplay between the bracket and archwire in a self-ligation system is what guides individual teeth into position and helps them adapt to a new environment. The concept of self-ligation differs from the conventional orthodontic philosophy of the orthodontist’s taking full control of treatment and making overcorrections as needed to achieve stability. When using a self-ligation system, it is not the orthodontist but the patient’s own tissue that is in full control. As stated by Damon, although a good facial balance can be obtained with a conventional technique, a self-ligation system can create a condition where orthodontic forces work in conjunction with the perioral tissues to produce favorable responses in a fuzzy way. Would the teeth settle into a stable position when forcefully moved into the ideal occlusal relationship according to a treatment plan? The ability to make a correct diagnosis, broad experience and great skills on the part of the orthodontist together with excellent patient compliance and uneventful progress of treatment would likely produce satisfactory and stable results. However, the occlusion would more likely be stable if the teeth are guided into their individualized optimal positions and given a chance to restore harmony to the surrounding tissues. This is in agreement with the concept of biocompatible orthodontics proposed by Damon.
The author often debates which slot size to use in straight wire technique, the 0.018” or 0.022” slot. The more flexible the archwire is, the more efficient the initial alignment is. In which slot size is the 0.014” Ni-Ti round wire more flexible? In contrast, the stiffer the archwire is, the less the reaction will be during extraction space closure. In which combination is the archwire stiffer, a 0.016”×0.022” wire in a 0.018” slot or a 0.019”×0.025” wire in a 0.022” slot (the archwire is thinner diagonally by approximately 12% in either case) ? The 0.022” slot is clearly more advantageous in both situations. This is in line with the above-mentioned treatment flow with a self-ligation system from initially passive to finally active. Treatment taking advantage of all these aspects will bring the benefits of longer interval between appointments and shorter active treatment time.
The best way to maximize treatment efficiency is to simplify treatment steps, which is a challenge for every orthodontic office from a practice management standpoint as well. Many orthodontists tend to spend excessive time and effort treating the symptoms their patients present with, due to the misconception that the symptoms are so diverse. They are urged to do something the minute they see a problem. This is the trap that good wire benders and orthodontists confident of their own treatment skills tend to fall into. When self-ligating brackets are used in combination with Ni-Ti and other high-technology archwires, there is no need for frequent archwire changes. The orthodontist should simply watch and wait for 3 months by letting the archwire do its job, although regular checkups are necessary to find out any complication that the patient is unaware of and that may slow down treatment, such as loose brackets and wire breakage. A 6-week interval between appointments seems to be appropriate.
In the Damon 0.022” slot system, the archwire sequence is simplified to the use of 3 archwires; 0.013” Damon Ni-Ti, 0.016”×0.025” Align SE Ni-Ti and 0.019”×0.025” pre-posted stainless steel. The SmartClip 0.022” slot system is also based on the use of 3 archwires; 0.016” heat-activated Nitinol, 0.019”×0.025” heat-activated Nitinol and 0.019”×0.025” stainless steel.
The author treats extraction cases in 4 steps; initial alignment with 0.018” Supercable, improvement of arch form and torque with 0.020” stainless steel or 0.020”×0.025” Ni-Ti SPEED archwire, space closure by sliding mechanics with 0.021” ×0.021” ×0.020” dual-geometry stainless steel, and establishment of final occlusion with 0.020”×0.025” stainless steel SPEED hwire. The same 4 steps are used in non-extraction cases with molar distalization, while non-extraction cases without molar distalization require another Ni-Ti high-technology archwire in the initial step in place of sliding mechanics.
What needs to be done in each step differs depending on the need for extraction and the severity of crowding since diagnosis varies from one case to another. The author believes it is desirable to proceed with treatment in the following steps. 1. Guide the teeth into initial alignment with a low-friction system. 2. Use the Supercable wire as an intial archwire to reduce pain. 3. Use a thermo-activated archwire for arch form establishment. 4. Interactive mechanism is desirable during sliding mechanics. 5. Active action is needed to ensure root alignment in the final step. This is only a personal opinion and is not meant to criticize any other system. All self-ligation systems have similar advantages with little difference in effectiveness as mentioned at the outset. However, each system has its pros and cons. It is important for the orthodontist to fully understand its features for optimal use of the system of his or her choice.
References
1）Woodside DG, Berger JL and Hanson GH: Chapter 17 Self-Ligation orthodontics with the SPEED Appliance, In: Orthodontics, Current Principles and Techniques, 4th ed., eds Graber T M, Vanasdall R L and Vig K W L, St.Louis, 2005, Mosby Co., 734-752.
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10）Toshihisa YAMAZAKI and Masae ARIMOTO: SPEED Appliance Technique in adult cases —Part 2. Using bite block with SPEED Appliance —, J. Japan Adult Orthod. Soc. 5: 55-72, 1998.
11）Yamazaki, T., Itoi, K., Homme, Y., Nakajima, A. and Namura, S.: The force distribution of aligning a lateral incisor in lingual version using the SPEED Appliance with double wire method. Nihon Univ. Dent. J. 73: 223-231, 1999.
12）Toshihisa YAMAZAKI: SPEED Appliance Technique in adult cases — Part 3. Alignment of a lingual version tooth using double wire and torque control with SPEED Appliance —, J. Japan Adult Orthod. Soc. 7-1: 13-24, 2000.
13） Donald G. WOODSIDE, Takayuki KURODA, Toshihisa YAMAZAKI: Global Outlook of Orthodontic Treatment --- a message from Toronto (Part 1). Journal of Orthodontic Practice 2002・11: 11-24, 2002.
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15）Toshihisa YAMAZAKI: An adult anterior open bite case 5 years out of treatment., J. Japan Adult Orthod. Soc. 11-1: 20-25, 2004.
16）Tatsuyoshi SUGAI and Toshihisa YAMAZAKI: An adult Class I four first bicuspid extraction case in which 28 teeth were aligned including four third molars., .J. Japan Adult Orthod. Soc. 11-2: 95-100, 2004.
17）Toshihisa YAMAZAKI: SPEED Appliance Technique in adult cases - Part 4. The properties of seven stranded nickel-titanium coaxial wire (Supercable) and its clinical use-, .J. Japan Adult Orthod. Soc. 12-1: 7-27, 2005.
18）Toshihisa YAMAZAKI, Jun OHTANI and Tatsuyoshi SUGAI : SPEED Appliance Technique in adult cases - Part 6. Treatment of deep overbite cases and depression of maxillary anteriors -,.J. Japan Adult Orthod. Soc. 12-2: 13-22, 2005.
19）Toshihisa Yamazaki, Chiemi Kamata, Jun Ohtani, Tatsuyoshi Sugai: SPEED Appliance Technique in adult cases - Part 7. Open bite cases treated with SPEED Appliance -,.J. Japan Adult Orthod. Soc. 12-2: 23-31, 2005.
20） Sims A P T , Waters N E, Birnie D J and Pethybridge R J : A comparison of the forces required to produce tooth movement in vitro using two self-ligating brackets and a pre-adjusted bracket employing two types of ligation. Euro J Orthod 15: 377-385, 1993.
21） Kemp D W : A comparative analysis of frictional forces between self-ligating and conventional edgewise orthodontic brackets. Diploma thesis, Department of Orthodontics, University of Toronto: 1992.
22） Weiss L: Frictional characteristics of aesthetic brackets in sliding mechanics. Diploma thesis, Department of Orthodontics, University of Toronto: 1993.
23） Profitt W R and Field H W :The Biological Basis of Orthodontic Therapy,Contemporary Orthodontics, 266-288, 1993
24）Damon D H: Chapter 18 Treatment of Face with Biocompatible Orchodontics, In: Orthodontics, Current Principles and Techniques, 4th ed., eds Graber T M, Vanasdall R L and Vig K W L, St.Louis, 2005, Mosby Co., 753-831.
25） Berger J and Byloff F : The clinical efficiency of self-ligated brackets, J Clin Orthod 35: 304-308, 2001.
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