Orthodontic treatment with self-ligating bracket systems

Introduction

Contemporary orthodontics entails orthodontic tooth movement through a force, which is applied through arch wires and is transmitted to the teeth via brackets. The arch wire is often held into the brackets with a ligature or similar arrangement.

In the earliest era of orthodontics, silk was used to secure the teeth to the ‘bandeau’, the rigid metal band around the teeth. Later, at the beginning of the 20th century, fixed appliances evolved and became popular, and gold ligatures were used to hold the arch wire. After the introduction of stainless steel, stainless steel ligatures became the universally accepted mode of ligation. Stainless steel ligation is cheap and robust and permits ligation of the arch wire to the bracket and at a distance. However, the force generated through friction is much higher, limiting the tooth movement during the early stages of treatment. The potential drawbacks are trauma to the oral mucosa due to a loose end or displaced tag, additional time required to place and remove ligation, and enhanced friction, which may not be desired.

With the availability of elastomeric modules in the late 1960s, faster placement and removal of ligation and a reduction in traumatic incidences became possible. However, elastomeric ligatures fail to achieve full arch wire engagement in the bracket due to their degradation properties. Also, much higher friction between the arch wire and bracket was present compared to stainless steel ligature.

Stainless steel and elastomeric ligature modules are the most common conventional ligation systems used in orthodontics. Table 57.1 presents their limitations.

TABLE 57.1

Limitations of conventional ligation

•
Wire ligation is a time-consuming clinical procedure.
•
The arch wire secured in brackets with ligature wires offer significant friction to initiate and continue with the tooth movement.
•
Ligatures provide poor securing mechanisms for less than full size wires, which can compromise control on tooth movement.
•
For elastomeric, ligature modules the force decays over time and therefore, tooth control is not optimal.
•
Both wire and elastomeric ligatures sometimes become displaced.
•
Oral hygiene is potentially impeded.

Self-ligation in orthodontics

Overcoming the limitations of stainless steel ligature and elastomeric modules, the clinicians devised a ligation device within the bracket, and these methods of self-holding the wire evolved over the years. Such brackets are categorised as self-ligation system.

Self-ligation in orthodontics implies that the orthodontic bracket can secure the arch wire with an inbuilt locking mechanism. The self-ligation bracket systems have a movable component that closes off the bracket slot, thereby creating a fourth wall of the bracket slot, transforming the bracket slot into a tube.

The bracket with a built-in system within the bracket to hold the wire is called a self-ligating bracket.

The closing mechanics may actively hold the undersized wire into the depth of the bracket slot, a process called active self-ligation, or close the bracket slots like a lid, a process called passive self-ligation system.

The desired features of an ideal ligation system are summarised in Table 57.2 .

TABLE 57.2

Properties of an ideal ligation system

•
The ligation should be secure and robust. Once ligated, it is highly desirable that the system be resistant to inadvertent loss of ligation. Wire ligation is good, while elastomeric ligation is inferior due to its force decay.
•
It should ensure full bracket engagement of the arch wire. Arch wires can be fully engaged in the bracket slot and maintained there with certainty. Wire ligatures maintain the engagement once achieved, while elastomeric exerts insufficient force, causing subsequent degradation of elastic property and loss of full engagement.
•
It should exhibit low friction between the bracket and arch wire.
•
It should be quick and easy to use.
•
It should assist in the maintenance of good oral hygiene. They should not accumulate plaque and interfere with oral hygiene.
•
It should be comfortable for the patient. It should not get displaced between appointments and cause trauma or discomfort. Elastomeric are good in this respect, but wire ligatures require careful tucking of the ends to avoid soft tissue trauma, and can occasionally be displaced between appointments, cause discomfort and may be the reason for an unscheduled clinic appointment.

Evolution of self-ligating brackets

Historically, Charles E. Boyd filed the patent for the first locking attachment in an orthodontic bracket in 1933. James W. Ford filed a patent for the Ford lock design manufactured by the Dee Gold Company of Chicago, Illinois. Its production was abandoned because it was too expensive and bulky.

Stolzenberg introduced the first self-ligating bracket, ‘Russell Lock’ edgewise attachment, as early as 1935, aiming to reduce ligation time and improve clinical efficiency. It consisted of a primitive mechanism of a circular threaded opening in the face of the bracket ( Fig 57.1 A).

Image, AltText currently not available — Figure 57.1

It had an edgewise slot for round wire up to 0.022 in. or rectangular wire up to 0.022 × 0.028 in. The flat threaded screw was used for the fixation or removal of the arch wire by simply turning the key.

Later, in 1971, A. J. Wildman introduced passive edgelock self-ligating brackets. They consisted of a round body with a rigid labial sliding cap. A special instrument was required to open the slot by moving the slide. The cap could be closed with finger pressure, converting the bracket slot into a tube. These brackets were bulky and inconvenient for opening and closing the slide ( Fig. 57.1 B).

Dr. Franz Sander, 1974, introduced another design of self-ligating brackets with a variable slot called Mobil-lock. These brackets had a rigid semi-circular disc, which could be turned with the help of a screwdriver to open or close the labial surface of the slot. The resulting labial face of the slot was narrow, giving poor rotational control. The difficulty of accessing to opening or closing the premolar brackets was another disadvantage of these brackets ( Fig. 57.1 C). Many clinicians, in collaboration with industry, developed and evolved different types of self-ligation mechanisms, used and further improved them for clinical efficacy and comfort. Contemporary self-ligating bracket systems are nearly perfect and available in steel and porcelain ( Table 57.3 ).

TABLE 57.3

Evolution of self-ligating brackets

Decade	Year	Introduced by	Appliance and manufacturer	Type	Mechanism	Evidence/advantage
Contemporary designs	2021		Damon Ultima (Ormco)	Passive	Flexible sliding clip	Case study: Class I crowded malocclusion with moderate maxillary and mandibular crowding (dental-tribune.com)
Contemporary designs	2021	Thomas Pitts	Pitts21 (OC Orthodontics)	Passive	Flexible sliding clip	The Protocol \| OC Orthodontics (oc-orthodontics.com)
2011–2020	2020	Luis Carriere	Carriere SLX 3D (Henry Schien Ortho-dontics)	Passive	Flexible sliding clip	Case studies—Carriere System
	2018		Damon Q2 (Ormco)	Passive	Flexible sliding clip	Buyukcavus M. H. Non-extraction ortho-dontic treatment with Damon system: two case reports. Black Sea Journal of Health Science. 2021; 4(1): 44–47.
	2017		H4 self-ligating system (OC Ortho-dontic)
	2017		In-Ovation X (GAC)	Active	Flexible sliding clip	In-Ovation X self-ligating metal bracket design features and advantages, Dentsply Sirona. Harradine NWT. The history and development of self-ligating brackets. Semin Orthod. 2008; 14(1):5–18.
	2017		Lotus Plus DS (Ortho technology)	Active/Passive	Flexible sliding clip
	2016		Empower 2 (American Orthodontics)	Active/Passive	Flexible sliding clip	American Orthodontics’ Empower 2 Self Ligating Metal Brackets; March 2017. Available from: http://www.americanortho.com .
	2015		ProGate I (US Orthodontic Products)	Passive	Flexible sliding clip
	2014	Ronald M Rancone	BioQuick (Forestadent)	Passive	Flexible sliding clip
	2014	Luis Carriere	Carriere SLX (Henry Schien Orthodontics)	Passive	Flexible sliding clip
	2012		Sensation Ceramic (Ortho Technology)	Active/Passive	Flexible sliding clip
2001–2010	2010		Cabriolet (Gestenco)	Active/Passive	Flexible sliding clip
	2009		SmartClip SL3 (3M Unitek)	Active/passive	Mesial and distal flexible clips	Bhatia VS, Kalha A, Nanda SB. An evaluation of smart clip self-ligating bracket system: comparison of treatment outcome and patient response between self-ligating and conventional pre-adjusted edgewise appliance. Orthod J Nepal. 2014;4(2):12–15.
	2009		Damon Q (Ormco)	Passive	Flexible sliding clip	Singh G, Patil R. Clinical experiences with self-ligation brackets in India. Journal of Indian Orthodontic Society. 2018;52(4_suppl2):115–126
	2007		Discovery (Dentaurum)	Passive	Flexible lid
	2007		Clarity SL (3M Unitek)	Active/passive	Mesial and distal flexible clips
	2006		In-Ovation L (GAC)	Active	Flexible clip
	2006		In-Ovation C (GAC)	Active	Flexible clip
	2006	Bjorn Ludwig	Quick (Forestadent)	Passive	Snap flexible spring
	2005		Damon 3MX (Ormco)	Passive	Rigid solid slide	Singh G, Patil R. Clinical experiences with self-ligation brackets in India. Journal of Indian Orthodontic Society. 2018;52(4_suppl2):115–126.
	2004	Gary L. Weinberger	SmartClip (3M Unitek)	Active/passive	Mesial and distal flexible clips
	2004		Damon 3 (Ormco)	Passive	Rigid passive slide
	2004		Time 2 (Adenta/American)	Passive		Shorter treatment time/Case study of an adult Valant JR. Time: A self-ligating interactive bracket system. Semin Orthod. 2008;14:46–53.
	2002		In-Ovation-R (GAC)	Active	Flexible spring clip
1991–2000	2000		Damon 2 (A company/Ormco)	Passive	Solid indented slide
	2000	Michael C. Alpern	In-Ovation (GAC)
	1998	A. J. Wildman	TwinLock (Ormco)	Passive	Solid labial slider
	1996	Dwight Damon	Damon SL (A company)	Passive	Solid indented slide
	1994	Wolfgang Heiser	Time (Adenta)	Passive	Rigid rotational arm
1981–1990	1986	Erwin Pletcher	Activa (A company)	Passive	Rigid rotational arm	Harradine NW, Birnie DJ. The clinical use of Activa self-ligating brackets. Am J Orthod Dentofacial Orthop. 1996;109(3):319–328.
1971–1980	1980	Herbert Hanson	SPEED (Strite industries)	Active	Flexible spring clip	Berger JL. The SPEED System: An overview of the appliance and clinical performance. Semin Orthod. 2008;14(1):54-63.
	1974	Franz Sander	Mobil-Lock (Forestadent)	Passive	Rigid rotational disc
	1971	A. J. Wildman	Edgelok (Ormco)	Passive	Rigid sliding cap
1930–1940	1935	Jacob Stolzenberg	Russell Lock	Active/passive	Circular threaded opening and screw

Significant developments have occurred in self-ligating brackets regarding robustness and ease of use, and these have rapidly grown in popularity. Many orthodontic practitioners have found them superior for patients’ and operators’ comfort besides a reduction in chair time. Some clinicians have begun using exclusively self-ligating brackets in their practice. The requirements of ideal self-ligating brackets are presented in Table 57.4 .

TABLE 57.4

Ideal requirements of self-ligating brackets

Source: Adopted from Eliades T, Pandis N. Self-ligation in Orthodontics. Wiley-Blackwell, 2009.

1.
The self-ligating brackets should be easy to open and close with low forces applied to the teeth during these procedures and with all arch wire sizes and materials.

2.
It should never open inadvertently, allowing a loss of tooth control.

3.
It should have a ligating mechanism that never jams or breaks or distorts or changes in its performance through the treatment period.

4.
It should have a positively held open clip/slide position so that the clip or slide does not obstruct the view of the bracket slot or the actual placement of the arch wire.

5.
Self-ligation brackets should be tolerant of a reasonable excess of composite material without obstructing the clip/slide mechanism.

6.
It should permit easy attachment and removal of all the usual auxiliary components of an appliance, such as elastomeric chain, undertie ligatures, laceback ligatures, without interfering with the self-ligating clip/slide.

7.
It should permit easy placement and removal of hooks/posts and possibly other auxiliaries on the brackets.

8.
It should have a suitably narrow mesiodistal dimension to take advantage of the secure arch wire engagement and permit large inter-bracket spans.

9.
It should have the performance expected of all orthodontic brackets regarding bond strength and smoothness of contour.

10.
It should perform similarly to a conventional twin pre-adjusted bracket with additional built-in convenient features of comfortable self-ligation for saving chair side time and comfort to the patient.

Active self-ligating brackets

The bracket has a flexible component (spring clip) that encroaches on the slot from the labial or buccal aspect and presses against the arch wire. This component is flexible and can store and release energy through elastic deformation. Some examples of active bracket systems are SPEED appliance (Strite Industries Ltd., Cambridge, Ontario, Canada) and In-Ovation (GAC International Inc., Bohemia, NY). Proponents of active clip claim that it provides a ‘homing’ action on the wire when deflected, thereby providing more control with the appliance. These brackets have a flexible clip that creates a passive slot depth available in two slot sizes 0.0182 in. and 0.022 in. With small round wires, the bracket is passive, but with full-size wires, the flexible clip is deflected and provides an active seating force on the arch wire.

The SPEED appliance

The first active self-ligating bracket, the SPEED appliance, was introduced in 1980 by Dr. G. Herbert Hanson as a miniaturised bracket with a wingless design and super-elastic nickel titanium spring clip. The SPEED is a fully adjusted edgewise appliance available in slot sizes 0.018 and 0.022 in. Every SPEED bracket has two horizontal slots: the arch wire slot and the auxiliary slot. The auxiliary slot is located at the occlusal of the arch wire slot and is 0.016 in. square dimension. The SPEED Mushroom Hook is a miniaturised integral hook available in all brackets. This uniquely shaped hook easily grasps and securely holds any style of intraoral elastomeric. These hooks are positioned on the distal side of each bracket.

The clip can be moved occlusal using an explorer tip inserted into the labial window in the face of the spring clip. The bracket can be opened by applying a light occlusal directed sliding force to the gingival dimple indent. The slot can be closed by applying finger pressure over the clip in the gingival direction ( Fig. 57.2 ).

In-ovation

In-Ovation brackets were introduced by Michael C. Alpern in 2000. They are similar to SPEED brackets but have a true twin design. However, they were large and had difficulty opening and closing the clips. In 2002, smaller brackets for anterior teeth were introduced as In-Ovation R (reduced). These brackets have sliding spring clips labially, extending entirely through the vertical channel in the bracket body. Aesthetic brackets In-Ovation C were introduced in 2006. In-Ovation rare brackets are made from a ceramic material with a rhodium-processed clip for enhanced aesthetics.

The clip slides easily when gentle pressure is applied occlusally to the v-notched clip at the gingival side of the bracket using the explorer or a similar instrument. The clip can also be closed similarly to SPEED brackets with finger pressure on the incisal curve ( Fig. 57.3 A).

A comparative study to evaluate the force loss due to friction in various wire dimensions and materials in conventional and SL brackets showed increasing wire size results in greater force loss due to friction.

The GAC innovation produced the lowest frictional forces among the canine retraction in the self-ligating system.

Passive self-ligating brackets

The bracket has a rigid, movable component to entrap the arch wire. This component closes the slot, converting the bracket slot into a rigid tube, and does not apply active force to the wire. Arch wire remains passive at the bracket clip interface within the bracket slot, regardless of its size. Among the examples of the passive self-ligating brackets are Damon system [(‘A’ Company, San Diego, CA, USA)/(Ormco Corporation,1717 W. Collins Ave., Orange, CA, USA) and SmartClip (3M Unitek 3M Center, St Paul, MN, USA)]. Proponents of passive slides claim less friction in the appliance during sliding mechanics. Thus, the forces generated by the arch wire are transmitted directly to the teeth and supporting structures without absorption or transformation by the self-ligation device.

Damon system

In 1996, Dr. Dwight Damon introduced a self-ligation system known as Damon brackets. ^, These brackets work on the principle of using the threshold force, which is the minimum amount of force needed to initiate tooth movement.

Dr. Damon recommends that the Damon brackets should be positioned in the green or safe zone of vertical bracket positioning. This means that the brackets should be placed at the mid-crown level, which is considered the safe zone. This ensures that ideal or close to ideal torque expression occurs. If the brackets are placed outside this zone, it can lead to under-expression or overexpression of the torque prescription.

To cater to different clinical cases, the Damon prescription has variable torque prescriptions. A clinician can place the upper and lower mid-bracket slot within the green lines without dramatically impacting torque.

Damon bracket has a passive self-ligating design with conventional tie-wings. The first bracket of the Damon series, Damon SL (‘A’ Company, San Diego, CA), had a large sliding door which sometimes opened inadvertently due to the exterior position of the slide. With evolution, the brackets have become more comfortable for the patient. The slide mechanism has become more reliable and more straightforward to open and close ( Fig 57.3 B).

The next generation Damon brackets (Damon 2) was introduced in 2000 (Ormco Corporation, 1717 W. Collins Ave., Orange, CA); the slide was placed in the shelter of the tie-wings to eliminate the inadvertent slide opening ( Fig 57.3 C).

The third-generation Damon brackets (Damon 3) introduced in 2004 were made up of clear material and stainless steel for aesthetics ( Fig 57.3 D). It has an improved, easy and secure mechanism for opening and closing, but the main drawback remained the metal separation from the reinforced resin component. Recently launched all metal variants, Damon 3MX ( Fig 57.3 E) and Damon Q ( Fig 57.3 F), in addition to improved properties, have an additional vertical slot permitting placement and removal of drop-in hooks in this bracket. These brackets require a unique probe-like instrument to open the slot. Alternatively, a dental probe can be used. The slot can be closed by moving the slide back with gentle finger pressure.

Damon system has a new bracket in the market called Damon Q2. The company claims that this bracket has 2× rotational control for optimal precision, predictability and efficiency. The brackets have a modified prescription for upper central and lateral incisors standard torque brackets. The tie-wing design provides ample space under the tie-wing area to better accommodate all power chains, elastics, steel ligatures and other auxiliaries for treatment versatility. There is a new vertical scribe along with the rhomboid-shaped pad that helps guide the desired bracket placement.

1. Torque modification; 2. tie-wing; 3. vertical scribe.

SmartArch

The SmartArch is a patented technology laser-manufactured CuNiTi rectangular wire recommended during the finishing stages. The rectangular arch wire has seven distinct zones to deliver programmed force to each of the teeth to meet their biological needs.

The science behind this new wire technology is the pulsating laser, which programs SmartArch to deliver forces closely matching Dr. Viecilli and Dr. Burstone’s established ideals. The wire has no or little friction and claims to need fewer wire changes.

The Damon Clear 2 combines the properties of low friction passive self-ligating technology with the aesthetics that image-conscious patients demand. Damon Clear 2 is a highly aesthetic and yet fully functional appliance. The aesthetic properties are derived from its composition, which is polycrystalline alumina (PCA) material. PCA is resistant to staining. The bracket system does not require any elastomeric and minimises friction, providing efficient tooth movement ( Fig 57.3 G).

Damon ultima system

The manufacturer of Damon Ultima System claims that it is the first full-expression orthodontic system designed for faster and more precise finishing. It is completely re-engineered to virtually eliminate play for precise control of rotation, angulation and torque. The system allows for earlier control with rotations, completed in two stages: first, Damon Ultima round-sided rectangular wire, and second, a wire with full expression using the second Damon Ultima wire with lighter forces.

The Damon Ultima System is designed with a proprietary round-sided rectangular wire and parallelogram-shaped slot to deliver direct engagement at vertical and horizontal contact points to provide a ‘four point contact’ in contrast to a conventional passive self-ligation (PSL) bracket system ( Fig 57.3 H).

The round-sided rectangular Damon Ultima wire engagement at the horizontal contact points delivers rotation control.

The angulation is resolved earlier with vertical contacts, torque control and complete expression of the prescription with lighter forces.

The brackets are available in procline, neutral and retrocline options for enhanced torque control. They have smoother tie-wings, a bracket base with 80-gauge mesh, a rhomboid shape with an enhanced scribe line and convenient drop-in hook placement. The wire progression sequence is 0.0140 in., 0.0180 in., 0.014 in. × 0.0275 in. and 0.018 in. × 0.0275 in. Cu NiTi.

SmartClip appliance

SmartClip self-ligating brackets were initially designed by 3M scientist Ming-Lai Lai and introduced by 3M Unitek (St Paul, MN, USA) in 2004. It consists of two nickel-titanium clips attached to the mesial and distal aspects of the bracket. When force is exerted on the clips through the arch wire, these clips open and close through elastic deformation. These are the only self-ligating brackets with true twin design, where the clinician can selectively engage the arch wire in only one clip in a case of severely malaligned teeth. Also, they have a tie-wing design that allows the use of an E-chain when needed ( Fig. 57.4 A and B).

The smart nitinol clips present some resistance to the insertion and removal of the arch wire. For wire insertion, a double-ended instrument with a rectangular notch on one end allows the clinician to direct the archwire into the bracket slot by applying gentle pressure to pass the arch wire through the clips. The opposite end of the instrument is used as a torque key for easy insertion of the rectangular arch wires ( Fig 57.4 C).

The disengagement plier is used to disengage arch wires from the bracket slot. The instrument has two hooks to engage the wire, while its central part is held on the buccal surface of the brackets. The wire can be disengaged from the bracket slot by pressing the handles together ( Fig 57.4 D).

Due to high clip forces, arch wire insertion and removal was uncomfortable. However, an improved version of these brackets, introduced in 2009 as SmartClip SL3 brackets, significantly reduced clip force. The aesthetic version of these brackets was introduced as Clarity SL in 2007. The Clarity SL bracket has since been discontinued.

A new version of the SL3 smart clip bracket has been introduced, which is called the Smart clip SL3 ‘Enhanced’ bracket. The base of the bracket is a ‘pivot’ base, and the ‘ramp’ of the ligating clip mechanism is angled, refined and improved to adjust wire engagement and disengagement forces, resulting in increased patient comfort and enhanced efficiency. This has also minimised the slop in the slot, thereby improving the rotation control.

SL3 enhanced clip

The S3 Enhanced Clip Smart Clip bracket has 25% more rotation control with 0.016 × 0.025 wire and 57% more rotation control with 0.019 × 0.025 wire.

3M has also introduced their Clarity Ultra self-ligating ceramic bracket. This is the first time 3M has forayed into the group of slide category self-ligating brackets. These brackets offer rotational control, improved versatility and 3M’s unique stress concentrator designed for predictable, consistent debonding. The bracket can be called an ‘on demand’ bracket as this passive bracket can become active on-demand with the addition of metal or elastomeric ligatures. It has an oval under tie-wing area, which permits double ligation for treatment versatility. Clarity Ultra brackets are the only fully aesthetic self-ligating brackets available pre-coated with 3M APC-Adhesive Pre Coated Flash-Free Adhesive.

Clarity Ultra brackets come available pre-coated with APC Flash-Free Adhesive on the base, ready for bonding right out of the package with no flash to clear away before light curing.

The doors on Clarity Ultra brackets span the entire width of the slot. It is a wide door covering the total mesial/distal dimension of the bracket. This offers excellent rotational control. No auxiliaries need to be added.

Pitts21

The Pitts21 PRO, in combination with the Engage Early and Expand Early arch wire suite, provide immediate expansion and simultaneous first, second and third order control from very early in the treatment cycle. All Pitts21 System Arch forms fully leverage the concept of ‘Variable Modulus Orthodontics’, allowing variation (modulation) in the delivered force levels without varying the arch wire profile ( Fig. 57.5 ).

Key features are early initial engagement, early full engagement and patient friendly, light, biologically active forces. An uncomplicated single prescription system and dynamic arch wire suite allow for simultaneous early expansion and early engagement.

Progressive slot: The Pitts21 PRO’s progressive slot provides exceptional 3D control of the anterior teeth and third order control of the posterior teeth while allowing the arch wire to slide easily through the posterior brackets.

Arch wires: Available in a variety of arch forms including ‘Broad’, ‘Broad+’ and ‘Broad ++’. These arch wires are designed to work with Pitts21, Pitts21 PRO and Clear21 bracket systems.

Quick-Turn tool: The specially designed Quick-Turn tool is a critical component of both the Pitts21 PRO and Clear21 System and is required to operate the ligating door. It provides smooth insertion and rotation for quick bracket door opening.

The appended table provides the wire’s size and properties to be used during various phases of orthodontic treatment ( Table 57.5 ).

TABLE 57.5

Pitts21 appliance wire sequence in different phases of orthodontic treatment

Phase	Wire size	Wire type
Initial	0.014	Thermal activated
Working	0.018 × 0.018	Ultra-soft thermal activated nickel titanium ++
Working	0.020 × 0.020 (Upper) 0.020 × 0.020 (Lower)	Thermal activated nickel titanium ++ Thermal activated nickel titanium +
Finishing	0.019 × 0.019 0.020 × 0.020	Stainless steel + Beta titanium + can be used on upper

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Orthodontic treatment with self-ligating bracket systems

Introduction