The Damon Passive Self-Ligating

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avid Birnie

The Damon System (Ormco Corp., 1332 South Lone Hill Ave., Glendora, CA

91740-0000) is a passive self-ligation system that was originally introduced

in 1994. Since then, both the bracket and the philosophy behind the system

have undergone continuous evolution. If the development of the Edgelok

(Ormco Corp.) appliance by Wildman in 1972 and the development of the

SPEED (Strite Industries Ltd., 298 Shepherd Ave., Cambridge, Ontario, N3C

1V1 Canada) appliance by Hanson in 1980 marked the start of modern

self-ligating appliances, then the Damon System has probably been responsible

for a fuller understanding of the influence of passive self-ligation on orthodontic

treatment and the increasing popularity and utilization of the concept. (Semin

Orthod 2008;14:19-35.) © 2008 Elsevier Inc. All rights reserved.

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he Damon Philosophy

full description of the Damon philosophyand treatment techniques are given by

amon.1 The Damon philosophy is based on therinciple of using just enough force to initiate

ooth movement—the threshold force. The un-erlying principle behind the threshold force is

hat it must be low enough to prevent occludinghe blood vessels in the periodontal membraneo allow the cells and the necessary biochemical

essengers to be transported to the site whereone resorption and apposition will occur andhus permit tooth movement.

A passive self-ligation mechanism has theowest frictional resistance of any ligation sys-em. Thus the forces generated by the arch-ire are transmitted directly to the teeth and

upporting structures without absorption orransformation by the ligature system. Theorces generated by elastomeric ligatures can

Consultant Orthodontist, Maxillofacial Unit, Queen Alexandraospital, Portsmouth, U.K.

Address correspondence to David Birnie, BDS (Edin), FDS,MI, RCSEd, FDS, MOrth, RCSEng, Consultant Orthodontist,axillofacial Unit, Queen Alexandra Hospital, Portsmouth, PO6

LY, U.K. E-mail: [email protected].© 2008 Elsevier Inc. All rights reserved.1073-8746/08/1401-0$30.00/0

●doi:10.1053/j.sodo.2007.12.003

Seminars in Orthodontics, Vol 14, N

ave unwanted side effects on treatmentrogress as shown in Figs 1-4.

Compared with conventional preadjusteddgewise appliances, it is suggested that the usef passive self-ligation results in a significant re-uction in the:

Use of anchorage devices because the fric-tional resistance generated by ligatures is notpresent. Srinivas2 has demonstrated that pas-sive self-ligating appliances use less anchoragethan conventional appliances. This supportsthe reduction in the use of anchorage devicesexperienced by users of passive self-ligation.Use of intraoral expansion auxiliaries such asquadhelices or W-springs because the force ofthe archwire is not transformed or absorbedby the ligatures and the necessary expansioncan be achieved by the force of the archwires.Need for extractions to facilitate orthodonticmechanics because alignment is not hinderedby frictional resistance from ligatures and cantherefore largely be achieved with small diame-ter copper nickel titanium archwires. Toothalignment therefore places minimal stress onthe periodontium as it occurs and so the possi-bility of iatrogenic damage to the periodontiumis reduced.

n addition, a passive edgewise self-ligation sys-em provides three key features:

Very low levels of static and dynamic friction,

19o 1 (March), 2008: pp 19-35

mail to: [email protected].

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20 D. Birnie

Rigid ligation due to the positive closure ofthe slot by the gate or slide, andControl of tooth position because there is anedgewise slot of adequate width and depth.

his allows extended intervals between treat-ent visits, particularly in the early stages of

reatment, a reduced number of visits during aourse of treatment, and shortened treatmentimes.

Although orthodontics is accepted as influ-ncing tooth position, alveolar bone, gingivalealth, and facial appearance, Damon suggests

hat orthodontic treatment can also affect

igure 1. At the start of treatment. Both upper per-anent cuspids are ectopic and palatally positioned.

Color version of figure is available online.)

igure 2. The upper cuspids have been exposed andre sufficiently erupted for traction hooks to belaced on them to move the cuspids into the line of

he arch. Space has been opened in the arch to ac-ommodate the cuspids. A 0.014� copper nickel tita-ium wire as been placed using figure of 8 ligatures toaximize archwire engagement and hence tooth con-

rol. (Color version of figure is available online.) (

peech, airway, and sleep disorders (Damon DH,ersonal communication, 2005). Although mostrthodontists would acknowledge the effect ofrthodontic treatment on the first four items,he last three are more contentious areas thatre closely related to soft tissues, their behavior,nd their relationship to orthodontic treatment.ne of the reasons that these areas are conten-

ious is that they are poorly understood becausef the difficulty in measuring them and the rel-tive ineffectiveness and unpredictability ofreatment strategies designed to influence them.

It is suggested that if the forces applied to theeeth are kept very low, then the lips will restrictnterior movement of the dentition and theongue may contribute to posterior expansion.

igure 3. Palatal view of upper cuspids and tractionooks taken at same visit as Fig 1. (Color version ofgure is available online.)

igure 4. One visit after Figs 2 and 3. The frictionaused by the elastomeric ligatures has prevented therchwire sliding through the brackets distal to the space.he archwire has therefore expressed itself by proclin-

ng the upper incisors resulting in an unwanted overjet.

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21Damon Passive System

his is demonstrated in Figures 5-7 wherehe right buccal segment has been distalized half

unit to allow eruption and alignment of thepper right permanent cuspid with gentle acti-ation of the coil spring only; during distaliza-ion, no increase in overjet occurred. In nonex-raction cases, this suggestion means that toothlignment results in:

Less incisor proclination and less labial pro-trusion than might be expected with a conven-tional nonextraction treatment;

igure 5. Start of treatment. Right buccal segmentalf a unit Class II. Right permanent cuspid in the linef the arch. (Color version of figure is available on-

ine.)

igure 6. Seven months into active treatment. Spaceas been opened for the upper right cuspid and thepper right buccal segment has been distalized half anit by placing an open nickel titanium coil springne bracket width wider than the interbracket spannd replacing at each visit. The overjet is unchanged.
Significant posterior expansion without theneed for auxiliary expanders such as rapidmaxillary expansion and quadhelices or W-springs; andPosterior expansion that is not produced bythe tipping movements normally expectedwith expansion achieved by the use of arch-wires and cross-elastics alone.

vidence for the Damon Philosophy

rchwire Placement and Removal

he speed of archwire ligation and release haseen studied by a number of authors3-6 andelf-ligating brackets have been shown to takeess time and also require less or no chairsidessistance. Turnbull and Birnie7 divided therchwires into four different groups in ascend-ng order of size. They found that:

The time taken to ligate archwires decreasedwith increasing archwire size. This was an un-expected finding; it might be expected thatligation of thicker wires might takes longerbecause of greater difficulty in obtaining fullarchwire engagement in the bracket. How-ever, the difficulty of obtaining full archwireengagement in the bracket with thicker arch-wires was offset by the tooth alignment pro-duced by earlier archwires.The time taken to open the Damon self-ligat-ing brackets and to remove elastomeric liga-

igure 7. End of treatment. Treatment duration, 22onths including time for upper right permanent

uspid to erupt. (Color version of figure is availablenline.)

tures was almost independent of archwire size.

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It took less time to ligate and release an arch-wire using Damon passive self-ligating bracketsthan with conventional brackets and elasto-meric ligatures.

ffect of Passive Ligation on Friction

any authors have found that static frictioneasured in vitro is much less with a passive

elf-ligating system than with any other type ofxed appliance.8-10 The static friction developedy passive self-ligating brackets is almost negligi-le as is shown in Fig 8. As angulation11 or

nclination12 is applied to the bracket, bindingccurs although the force generated by thisinding is less for self-ligating brackets than foronventional ligation. A further study13 thatooked at dynamic friction also suggested thatamon brackets had the lowest frictional resis-

ance of the four bracket types tested: conven-ional, ceramic, active self-ligating (GAC In-Ova-ion; GAC International, 355 Knickerbockerve., Bohemia, NY 11716) series, and passive

elf-ligation (Damon2).

linical Studies

ne of the extrapolations from these in vitrotudies might be that the low static and dynamicriction will result in more rapid initial align-

ent. One clinical study,14 which utilized a splitouth design, found that this did not in fact

ccur and that there was no difference in thepeed of alignment between conventional brack-

igure 8. Figure showing static friction for passive,ctive, TipEdge, and conventionally ligated brackets.he value for the passive self-ligating Damon SLracket was zero except for with the 0.019� � 0.025�tainless steel archwire. Reprinted with permission ofxford University Press.8

ts and Damon2 brackets when measured using d

ittle’s Index. This is a surprising finding partic-larly as other passive ligating systems, such ashe Begg technique, were known for their rapidooth movement.15 It may be accounted for byhe experimental design, which although inge-ious, did not allow independence between theffects of the conventional and self-ligatingrackets. In addition, a then-current but nowbsolete archwire sequence (0.014�, 0.016��.025� copper nickel titanium) was used.

Another study16 has shown that more initiallignment in a given time was produced withamon brackets than with conventional brack-ts by a factor of 1.7. When the experimentalroup was subdivided into less crowded andore crowded cases, the less crowded cases

ligned 2.5 times faster and the more crowdedases 1.4 times faster.

Cash and coworkers17 studied slot dimensionsn 11 different bracket types and determinedhat the Damon2 bracket had a convergent slotith a base dimension that was 17% oversize andslot opening that was 13% oversize. Bourauel

nd coworkers18 in a laboratory study foundamon2 brackets less effective in transmitting

orque than SPEED or brackets using conven-ional ligation and attributed this to greater playetween bracket and archwire. Pandis and Elia-es19 investigated the effectiveness of torque

ransmission with conventional and self-ligatingrackets in extraction and nonextraction casesnd found no difference between the tworacket types in their ability to torque upper

ncisors in either extraction or nonextractionases.

ength of Treatment

f alignment and space closure can be achievedore quickly with self-ligating brackets due to

educed friction, then treatment times might behorter using self-ligating brackets. Harradine3

n 2001 and Eberting and coworkers,20 also in001, showed reductions in treatment times of 4nd 7 months respectively.

racket Design

he bracket design of the Damon bracket hasad the following characteristics since its intro-
uction as the Damon SL bracket:

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A passive self-ligating design with conventionaltie wings, andA self-ligating gate, with a positive mechanismto keep the gate either open or closed, thatopens to allow operator to see into slot.

s the bracket has evolved, the following fea-ures have changed:

The bracket has become smaller, with a lowerprofile and more rounded contours resultingin a bracket that is more comfortable for thepatient.As a result of a clearer understanding ofbracket function and advances in manufactur-ing technology, the gate mechanism has be-come more reliable, and simpler to open andclose.

The D3 MX bracket has a vertical auxiliaryslot.

he most recent bracket design, the D3 MX, is aighly sophisticated piece of industrial designnd is shown in Figs 9 and 10; it is quite unlikehe simple drawn and milled standard edgewiserackets of 4 decades ago.

reatment Planning

reatment planning should be based on etiol-gy, and careful thought about why the pre-enting malocclusion occurred.

●Figure 9. Damon 3 MX bracket with gate closed.

Treatment planning involves five separate ar-as.

he Face

reatment planning should take into account:

The individual’s facial pattern and appear-ance, andThe likely growth, maturation, and aging ofthe patient’s face including the influence ofgenetic inheritance on their future facialappearance.

he Soft Tissues

he interpretation of soft tissue behavior and itsnfluence on tooth position and oral function iscknowledged but difficult to quantify in individ-al cases. The clinician should consider whetheroft tissue behavior has been a significant factorn the development of the malocclusion and, ifo, whether it can be modified. This includesonsideration of lip position and lip posture,ongue behavior, muscle tone, and mode ofreathing.

ental Factors

ental factors include:

Space analysis,

igure 10. Damon 3 MX bracket with gate open.ermanent bracket identification is cast into the basef the slot.

Arch width analysis, and

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24 D. Birnie

The inclination of labial and buccal segmentteeth.

everal decades ago, tooth extraction was neces-ary to obtain dental alignment because of theelatively unsophisticated appliances available.echnically, it is often no longer necessary, ex-ept in a few cases, to extract teeth to obtainlignment or to facilitate orthodontic mechan-cs. Extractions may be required, however, toptimize facial balance or because of dental oreriodontal pathology. In addition, tooth extrac-

ion does not necessarily prove a guarantee ofosttreatment or postretention stability.

ephalometry

ephalometry remains an important tool for therthodontist, but long and elaborate analysesre unnecessary in most cases. It remains subser-ient to facial analysis for many measurements.ome parameters (such as upper incisor inclina-ion) can be visualized directly rather than being

easured from a lateral skull radiograph. Inddition, treatment to mean values (such as forncisor inclination) do not recognize the signif-cant range of biological variability present inhe population nor is this strategy a guarantee ofreatment stability.

The response of the facial tissues to toothovement, particularly proclination, is unpre-

ictable and so tooth movements planned tochieve favorable, or prevent unfavorable softissue movements, should be executed withaution.

ral Health

atients with good oral health, excellent oral

able 1. Optional Torque Values in the Damon Syst

U1 U2 U

High torque �17° �10° �Standard torque �12° �8°Low torque �7° �3°

L1 L2 L

High torque �Standard torque �1° �1°Low torque �6° �6°

ygiene, and a normal gingival biotype seem to t

btain better orthodontic results than those withompromised oral health. Particularly in thereteen and teenage patient, the healthy peri-dontium seems to have significant powers ofdaptation and regeneration.

racket Selection

btaining the correct inclination of teeth duringrthodontic treatment has always been challeng-

ng with orthodontic appliances based on thedgewise system. The Damon System provides sev-ral torque options for incisor and cuspid teethnd these are shown in Table 1. In general, theorque selected in each bracket should be de-igned to over-correct tooth position.

igh Torque Brackets

xamples of where high torque brackets may besed on upper incisors are as follows:

Extraction cases where treatment mechanicsmay excessively retrocline the upper incisors;Class II Division 1 malocclusions where treat-ment mechanics may excessively retrocline theupper incisors; andClass II Division 2 malocclusions.

xamples of where high torque brackets may besed on upper cuspids are as follows:

First premolar extraction cases; andCases where the crowns of the upper cuspidsare palatally tipped.

tandard Torque Brackets

tandard torque brackets are used where thenclination of the teeth is satisfactory before

Upper Arch

U4 U5 U6 U7

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Lower Arch

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�12° �17° �28° �10°

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reatment and the treatment mechanics will not

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dversely affect the inclinations during treat-ent.

ow Torque Brackets

xamples of where low torque brackets may besed on upper incisors are as follows:

Excessively proclined upper incisors;Isolated upper incisors with palatally posi-tioned roots (eg, upper lateral incisor in thepalate);Malocclusions where treatment mechanicsmay result in excessive upper incisor proclina-tion;Moderate and severe upper arch crowding;andAnterior open bite cases with proclinedincisors.

xamples of where low torque brackets may besed on lower incisors are as follows:

Cases where it is necessary to control the pro-clination of lower incisors, eg; extreme lowerlabial segment crowding, cases using Class IIelastics, and fixed Class II correctors attachedto the brackets, buccal tubes, or archwires;and

Lingually placed lower incisors.

he brackets with optional torque values shouldot be used as “sets.” The clinician should study

he case carefully beforehand and individuallyelect the bracket with the correct torque forach tooth.

racket Positioning

racket positioning follows the principles sug-ested by Andrews21 where brackets are placedn the midpoint of the facial axis of the clinicalrown with the vertical bracket positioning keyeg, tie wings for D3 and D3 MX brackets) par-llel to this axis.

The following exceptions to this rule shoulde noted:

Lower cuspid brackets should be positioned0.5 mm to 1 mm mesial to the facial axis of theclinical crown to prevent the mesial edge ofthe cuspid tucking behind the distal part of
the lower lateral incisor.
For deep bite cases, cuspid and incisor bracketsshould be progressively placed slightly more in-cisally in both arches to aid bite opening.For open bite cases, cuspid and incisor bracketsshould be placed progressively slightly more gin-givally in both arches to aid bite closure.Where teeth have to undergo significant trans-lation, overangulation of the brackets to exag-gerate the root movement in the desired di-rection will ensure adequate root movementoccurs. Examples of malocclusions where thisstrategy is helpful include the correction ofpseudotranspositions, the opening of spacefor restorative implants, and closure of largespaces such as moving lateral incisors into cen-tral incisor spaces.Where teeth have incisal edge damage or aresubstituting for other teeth, position thebrackets to obtain the correct gingival emer-gence profile and adjust the subsequent in-cisal edge problem restoratively.Brackets are not inverted to change the torquevalues as this may make the gates more vulner-able to inadvertent opening, and rarely gen-erates enough torque to completely correctthe problem.

nstead, choose a bracket with a torque valuehat will exaggerate the tooth movement re-uired (such as a low torque bracket for a pala-ally placed upper lateral incisor). This solveshe first problem, but in most cases, additionalorque will need to be placed in the archwire tobtain ideal root position.

reatment Phases, Archwire Selection,nd Archwire Sequencing

hase 1: Light Round High Technology Wires

his phase of treatment uses 0.013�, 0.014�, or.016� copper nickel titanium archwires. Theims of this phase of treatment are to:

Obtain tooth alignment;Level the arches (excluding second molars).Second molars, although bonded from thestart of treatment, are not engaged by theinitial archwire until the second phase of treat-ment to prevent the archwire being dislodgedfrom the second molar tubes. The intertube
span between first molar and second molar is

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26 D. Birnie

too large to reliably support small-diameternickel titanium archwires;Substantially correct all anterior rotations andpartially correct posterior rotations; andInitiate arch development by using lightenough forces to allow the soft tissues to in-fluence arch shape.

his phase of treatment normally lasts 10 to 20eeks and appointment intervals are at 10eeks.

hase 2: High Technology Rectangular Wires

he second molars are normally engaged byhe first archwires in this phase except in pa-ients with anterior open bites. This phase ofreatment normally uses two archwires: 0.014�

0.025� followed by 0.018� � 0.025� copperickel titanium wires. In cases that are wellligned at the start of treatment, these tworchwires can occasionally be replaced by aingle 0.016� � 0.025� copper nickel titaniumire. The use of a wire with a 0.025� first orderimension is critical to obtain tooth alignmenty almost completely filling the 0.027� slotepth of a Damon bracket.

Where incisor intrusion is required, 0.017� �.025� or 0.019� � 0.025� copper nickel titaniumrchwires with preformed curves or reverseurves of Spee can be used in this stage. Addi-ional torque can also be applied at this stageith the use of 0.019� � 0.025� copper nickel

itanium archwire preformed with 20° of torquenteriorly.

The aims of this stage of treatment are to:

Fully correct all rotations and obtain full align-ment of all teeth,Consolidate any anterior space and maintaintooth contact,Initiate torque control,Initiate bite opening, andContinue arch development.

he duration of this phase of treatment is 20 to0 weeks. The first archwire is left in place for 8o 10 weeks and the second for 4 to 6 weeks.

hase 3: Major Mechanics

he archwires used in this phase are 0.019� �.025� preposted stainless steel archwires. Many
uccal segment crossbites will have corrected
pontaneously by this stage, particularly when, ass often the case, the crossbite has not includedhe second molars. Where buccal segment cross-ites persist, the use of a 0.016� � 0.025� pre-osted stainless steel archwire in the arch whereome buccal or lingual tipping is desired, to-ether with the use of a 3/16� (110 g) crosslastic, will assist crossbite correction.

The aims of this phase of treatment are to:

Maintain the archform developed in the firsttwo phases,Finish torque control,Consolidate posterior space, andCompletely correct anteroposterior, buccolin-gual, and vertical relationships.

his phase of treatment lasts 8 to 10 weeks withppointments at 10-weekly intervals. Wherelass II or Class III elastics are being used, buc-al segment correction occurs more quickly ifhe molar distal to those to which the elastic islaced are temporarily not included in the arch-ire.

hase 4: Finishing and Detailing

he stainless steel archwires may be continuedn this phase. However, some detailed adjust-

ents to individual teeth may be required, inhich case 0.019� � 0.025� ß-titanium archwiresllow individual adjustments to be made in therchwire to optimize tooth positions. Settlinglastics may be used to develop a well-interdigi-ated occlusion.

anaging Severely Displaced or Rotated Teeth

everely displaced teeth are managed by creatingpace for the teeth with open coil spring; thishould be done with low forces and the coil springhould be no longer than the width of the spacelus a bracket width (approximately 3 mm). A

raction hook is bonded to the displaced tooth.he displaced tooth is tied to the archwire withlastic thread. Two types of traction hook are used:

A very thin wire loop traction hook on a bond-able base. This is demonstrated in Figs 11 and 12and used where there is very little space for thedisplaced tooth or on rotated teeth some dis-tance from the line of the arch. It is positionedso that the lumen of the hook will allow the
archwire to pass through it as the tooth ap-

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proaches the line of the arch. Its minimalmesiodistal width maximizes interbracketspan although provides no intrinsic rotationalcontrol.A broader eyelet or traction hook (part no:DB22-0450; DB Orthodontics Limited, Rye-field Way, Silsden, Keighley, West Yorkshire,

igure 11. This patient has an upper left palatal cus-id that is rotated mesially. A traction hook has beenlaced on the mesial edge of the tooth to maximizeerotation as the tooth moves to wards the line of therch. The bracket system is Damon2 (D2) and therchwire 0.014� copper nickel titanium. A length ofoil spring one bracket width wider than the space haseen placed and the tooth attached to the archwireith elastomeric thread. (Color version of figure isvailable online.)

igure 12. Two visits after that of Fig 11. At the previousisit, the 0.014� copper nickel titanium (CuNiTi) arch-ire was put through the lumen of the bracket. All theovement of the upper left cuspid has been achievedith a traction hook and a 0.014� CuNiTi archwire in

wo visits. The D2 bracket was placed at this visit. (Color
ersion of figure is available online.)
BD20 0EF U.K.) used where greater space isavailable but insufficient to place a self-ligat-ing bracket in its correct position as shown inFigure 13. This type of traction hook is ori-ented in the same way as the other type oftraction hook but has the advantage of givingsome rotational control.

f the tooth is rotated, then two strategies may besed:

If the tooth is so displaced from the archwirethat it is not possible to engage the tractionhook directly with the archwire, the tractionhook is attached to the archwire with elasticthread and positioned so as to maximize cor-rection of the tooth’s position as it movestoward the arch.If the traction hook can be directly engagedwith the archwire, then elastomeric chain isplaced over the archwire, mesial or distal tothe traction hook depending on the directionof rotation required and then attached to abracket that has the archwire fully engaged soas to provide a very light derotation couple.This technique is particularly useful for ro-tated lower incisors and rotated premolarswhere initial placement of a full-sized bracket

igure 13. The upper left lateral incisor has a broadraction hook in place with the 0.014� copper nickelitanium archwire running through its lumen. Theres insufficient room to place a full-sized bracket. Theroader traction hook gives some rotational controlnd is usually replaced with a normal passive self-igating bracket after one visit. (Color version of fig-re is available online.)

in the correct position is impossible.

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rchwire Stops

assive self-ligating brackets have extremelyow levels of friction between archwire andracket. Archwires are free to swivel to mesio-istally and, if allowed to do so, cause “wireokes” distal to the terminal buccal attach-ents. The archwires therefore need to be

tabilized using archwire stops to prevent irri-ation to the buccal mucosa. Originally, a sin-le stop was placed in a short interbracketpan, such as between lower incisors or be-ween upper first and second premolars. Stopsould be made of composite, soft split stainlessteel tube, or stainless steel tube placed overhe archwire before insertion.

Many high technology archwires now comeith two stops preloaded on to the archwires and

he following recommendations for the use oftops are given:

To stop the archwire swiveling, stops areplaced either side of a bracket or at either endof an interbracket span.Stops should be placed on a section of thearchwire where little movement of the arch-wire relative to the bracket is expected to oc-cur. Thus stops should be placed as far aspossible from crowded, displaced, or rotatedteeth. Where crowding is bilateral, stopsshould be placed anterior to the crowding.Stops should be placed where they are unob-trusive and not easily seen. This normallymeans in the lower incisor region and in theupper second premolar region. Stops placedalso help to identify the archwire once it is

igure 14. A Damon splint and tongue trainer.Color version of figure is available online.)

removed from the mouth.

tops can also be used to prevent tooth move-ent. Examples of this are as follows:

Placement of the stops distal to the cuspidsmaintains consolidation of the anterior seg-ment.Placement of stops at either end of an inter-bracket span can maintain space for an une-rupted or prosthetic tooth.Placement of stops immediately mesial to up-per second molars in first molar extractioncases will maintain arch length to allow theresolution of anterior crowding.

tops are not required on preposted archwiress the posts act as stops; careful selection of theize, however, can mean that the posts can have

secondary function such as maintaining theonsolidation of anterior space.

nteroposterior Correction

lass II Malocclusion

nteroposterior correction of Class II malocclu-ion is often achieved before fixed appliancereatment using some form of functional appli-nce. If not, then Class II correction can bechieved during treatment using either classlastics or a fixed Class II corrector such as aerbst appliance attached to the archwires.The Herbst appliance is a more effective class

orrector than Class II elastics and so is usedhere more facial and dental correction is re-uired.

The Herbst appliance is fabricated to fit on tohe archwire directly. Its use is facilitated by these of self-ligating upper first molar tubes. A TPlip-Lock Herbst kit (TP Orthodontics Inc, 100enter Plaza, Laporte, IN 46350) is required

ogether with some thick-walled 0.022� � 0.028�nconel (trademark of Special Metals Corpo-ation, Huntington, WV) rectangular tubingOSCAR Inc., 11793 Technology Dr., Fisher, IN6038). The stages of fabrication and fitting ares follows:

Sections of the Inconel tubing are welded andsoldered to the underside of the Herbst axles(�4) so that the Inconel tubing is flush onone side of the axle and projects 2 mm on theother side.The patient should be in 0.019 � 0.025� pre-
posted stainless steel archwires.

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The Herbst axles are placed on the archwires.In the upper arch, the 2-mm Inconel tubeprojection should face anteriorly, and in thelower arch posteriorly. This is to maximize the

igure 15. Extraoral photographs at the start of treaacial appearance. (Color version of figure is available

distance between the axles.

In the upper arch, the Herbst axles are placedbetween the upper first and second molars. Inthe lower arch, the Herbst axles are placedbetween the lower cuspids and the lower first

t aged 14 years 0 months. Note relatively immatureine.)

Figure 16. Intraoral photographs atthe start of treatment. There is mod-erate crowding in the upper arch andsevere crowding in the lower arch.The clinical crown of the lower rightcentral incisor is longer than on theadjacent teeth. There is a left buccalsegment crossbite. (Color version offigure is available online.)

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premolars. The Inconel tube should be an

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30 D. Birnie

exact but not tight fit between the intertube/interbracket space.The Herbst piston/cylinder assembly is thencut to provide approximately 4 to 6 mm ofinitial protrusion. The piston should betrimmed so that it does not protrude morethan 3 mm out of the back of the cylinder inthe closed position so as to avoid irritation to

igure 17. Cephalometric radiograph at the start ofreatment.

the buccal mucosa. The cylinder is engagedfirst on the upper axles, the piston insertedinto the cylinder and then attached to thelower axle.The integrity of each buccal segment is main-tained by a wire ligature or elastomeric linkrunning from the hook on the second molarto the archwire post.The Herbst is activated 2 mm at each visit byplacing split tube spacers (TP OrthodonticsInc.) over the piston until a full edge-to-edgeocclusion is achieved.

nce a full edge-to-edge occlusion has beenchieved, the Herbst appliance is left in place forfurther 6 months.

etention

etention is normally with a fixed solid 0.026�tainless steel wire retainer from the lingualurface of lower cuspid to lower cuspid. Theire is only bonded to the lingual surfaces of

he lower cuspids, which are lightly sand-lasted before etching. The ends of the wirere flattened, contoured, and sandblasted toaximize retention. In the upper arch, a

raided retainer wire (Reliance Orthodonticroducts, PO Box 678, Itasca, IL 60143) isonded to the palatal surfaces of the fourpper incisors ensuring that it does not inter-

ere with the lower incisors. Upper and lower

Figure 18. Treatment progress ap-proximately 7 months into treat-ment. Alignment has been achievedin the upper arch. (Color version of
figure is available online.)

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acuum formed retainers are used in additionn a nighttime-only basis.

For patients who have had correction of a ClassI skeletal pattern, a Damon splint and tonguerainer is used to maintain Class II correction overhe long term. This is shown in Fig 14.

ummary

assive self-ligation offers the most directransmission of force from archwire to toothith very low friction, secure ligation, and ex-

ellent control of tooth position. All contem-orary modalities of orthodontic treatmentan achieve tooth alignment; passive self-liga-ion, however, does achieve results effectively,fficiently, and in a manner that correspondsith patient values. In addition, practitionersxperienced with the technique perceive thatdditional, unexpected patient benefits occurhat are not traditionally associated with con-entional orthodontic treatment. However,hese need further evaluation to understandnd substantiate them. Mastering self-ligation

Figure 19. Treatment progress 15months into treatment. Alignmentwithin the arches has been achievedalthough some spacing persists inthe upper arch and should havebeen consolidated and tooth con-tact maintained with a continuouswire tie or stops distal to the uppercuspids. (Color version of figure isavailable online.)

Figure 20. Patient at 25 monthsinto treatment. The second molarswere bonded 16 months into treat-ment and crossbite correction hasoccurred spontaneously without theneed for auxiliary appliances suchas a quadhelix appliance or crosselastics. (Color version of figure is
available online.)

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32 D. Birnie

s challenging, however, and it is not a tech-ique that requires less clinical judgment orroficiency. Effective health care interventionsust have an evidence base; that evidence

ase is a combination of clinically relevantesearch, clinical expertise, and patient val-es.22 For passive self-ligation, the clinicallyelevant research base is small because interestn the subject has only commenced relativelyecently, but is growing steadily; clinical exper-ise has allowed the technique to evolve and

ature and its flexibility allows it to respondo patients’ needs and preferences.

ase Presentation

his case is presented because it is challenging andontroversial. It was treated by the author shortlyfter changing over completely to passive self-liga-ion in 2001. There are many possible ways ofreating it. Important questions, however, are:

What caused the malocclusion?What treatment would provide the best opti-mization of facial appearance, smile esthetics,oral health, and stability?

atient 09038801 presented at 14 years 0 monthsith moderate upper arch crowding and severe

ower arch crowding. His facial appearance wasrepubescent, he did not seem to have enteredis pubertal growth spurt, and it was thought

hat significant nasal tip and chin growth would g

ccur during his teenage years. He has a leftnilateral crossbite. The lower right central in-isor has a long clinical crown (see Figs 15-17).ll permanent teeth were present on the dentalantomogram except for the upper third mo-

ars. His oral hygiene was good although stillapable of improvement.

Figure 21. Patient at 12 months af-ter the end of active treatment and1 year into retention. The clinicalcrown height of the lower incisorshas normalized. The crowding hasbeen resolved. The patient has di-rect bonded fixed retainers and vac-uum formed retainers that havebeen worn in the evenings and atnight only. (Color version of figureis available online.)

igure 22. The posttreatment cephalometric radio-
raph.

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Figure 18 shows treatment progress after 7onths of treatment. Alignment has been

chieved in the upper arch, but there is stillnsufficient space for the lower left lateral inci-or. No crossbite correction has yet taken place;ote that the right second molars, which are justisible, are not in crossbite.

Figure 19 shows 15 months into treatment.lignment within the arches has been achieved,ut crossbite correction has not yet taken place.nce alignment of the upper labial segment had

able 2. Cephalometric and Study Cast Values at thective Treatment (First Retainer Check)

Units

Skeletal measurementsSNA degreesSNB degreesANB degreesSN-maxillary plane degreesMaxillary-mandibular plane degreesLAFH mmUAFH mmLAFH/TAFH % percentLPFH mmUPFH mmPFH mmWits appraisal mm

TeethOverjet mmOverbite mmUI-Maxillary plane degreesLI-Mandibular plane degreesInterincisal angle degreesL1-Apo mmL1-Facial plane mm

Soft tissueUpper lip to E-plane mmLower lip to E-plane mmNasolabial angle degreesChin thickness mmB-NPo mmL1-Mandibular plane mm

Lower study castInter cuspid width mmInter first bicuspid width mmInter second bicuspid width mmInter first molar width mmInter second molar width mm

Upper study castInter cuspid width mmInter first bicuspid width mmInter second bicuspid width mmInter first molar width mmInter second molar width mm

NA, Sella-Nasion-A point; SND, Sella-Nasion-B point; ANB, Apper anterior facial height; LAFH/TAFH%, lower anterior

ower posterior facial height; UPFH, upper posterior facial he-plane, Rickett’s esthetic plane; B-NPo, B-Point-Nasion-Pog

een obtained, the consolidation should have a

een maintained with a continuous tie or stopsistal to both upper cuspids.

Figure 20 shows 25 months into treatment.he second molars were bonded 16 months into

reatment, and crossbite correction then oc-urred spontaneously without the need for aux-liary appliances or cross elastics. Once stainlessteel archwires were placed, the upper archwireas expanded and the lower contracted to en-

ure maximal correction.Figure 21 shows 12 months after the end of

rt of Treatment and Four Months after the End of

March 2002 11 March 2005 Difference

83.4 83.0 �0.477.9 77.3 �0.65.6 5.7 0.14.2 5.6 1.4

27.8 28.2 0.455.2 62.1 6.950.2 54.7 4.555.1 56.7 1.624.3 27.8 3.545.0 47.5 2.569.4 75.3 5.93.0 4.4 1.4

7.6 2.8 �4.83.2 1.3 �1.9

113.9 114.9 1.087.4 97.5 10.1

131.0 119.3 �11.70.2 3.4 3.23.0 6.1 3.1

�1.3 �5.1 �3.81.3 �0.2 �1.5

114.4 121.7 7.310.6 9.5 �1.1

�1.1 �2.4 �1.334.6 39.5 4.9

19.2 29.4 10.229.6 38.1 8.538.2 43.8 5.649.6 50.7 1.152.2 55.9 3.7

31.4 38.4 7.039.0 46.4 7.441.0 51.1 10.147.0 55.1 8.152.3 58.1 5.8

t-Nasion-B point; LAFN, lower anterior facial height; UAFH,height as a percentage of total anterior facial height; LPFH,UI, upper incisor; LI, lower incisor; Apo, A Point-Pogonion;.

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18

poinfacialight;

ctive treatment and 1 year into retention. The

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34 D. Birnie

igure 23. Extraoral photographs taken 12 months after the end of active treatment showing that significantacial maturation has taken place. Nasal growth has taken place and the hyoid bone is now much more
rominent. (Color version of figure is available online.)
igure 24. Superimposition of the start and finish cephalometric tracings. The amount of nasal growth relativeo lip growth is demonstrated. The upper incisors have retained their inclination, but there has been proclina-
ion of the lower incisors. (Color version of figure is available online.)

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linical crown heights of the lower incisors havequalized. In addition to the fixed retainers, theatient wears vacuum formed retainers in thevenings and at night.

Figure 22 shows the posttreatment cephalo-etric radiograph. Table 2 shows the cephalo-etric values at the start of treatment and at therst retainer check four months after the end ofctive treatment.

Figure 23 shows the patient’s facial appearance2 months after the end of active treatment. Sig-ificant maturation of the face has taken place

ncluding nasal tip growth and development of theyoid bone. The patient has changed from aoung boy to a young man.

Figure 24 shows the superimposition of startnd finish cephalometric tracings. Note nasal tiprowth relative to lip growth. Upper incisororque has not increased, but there has beenome proclination of the lower incisors.

eferences1. Damon DH: Treatment of the face with biocompatible

orthodontics, in Graber TM, Vanarsdall RL, Vig KWL(eds): Orthodontics: Current Principles and Tech-niques. St Louis, Elsevier Mosby, 2005, pp 753-831

2. Srinivas S: Comparison of canine retraction with self-ligated and conventional ligated brackets—a clinicalstudy. Thesis in fulfillment of postgraduate degree,Tamilnadu University, Chennai, India, 2003

3. Harradine NWT: Self-ligating brackets and treatmentefficiency. Clin Orthod Res 4:220-227, 2001

4. Maijer R, Smith DC: Time saving with self-ligating brack-ets. J Clin Orthod 24:29-31, 1990

5. Shivapuja PK, Berger J: A comparative study of conven-tional ligation and self-ligation bracket systems. Am JOrthod Dentofacial Orthop 106:472-480, 1994

6. Voudouris JC: Interactive edgewise mechanisms: form andfunction comparison with conventional edgewise brackets.Am J Orthod Dentofacial Orthop 111:119-140, 1997

7. Turnbull NR, Birnie DJ: Treatment efficiency of conventionalversus self-ligating brackets: the effects of archwire size andmaterial. Am J Orthod Dentofacial Orthop 131:395-399, 2007

8. Thomas S, Birnie DJ, Sherriff M: A comparative in vitro studyof the frictional characteristics of two types of self ligatingbrackets and two types of preadjusted edgewise brackets tied
with elastomeric ligatures. Eur J Orthod 20:589-596, 1998
9. Pizzoni L, Raunholt G, Melsen B: Frictional forcesrelated to self-ligating brackets. Eur J Orthod 20:283-291, 1998

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1. Thorstenson BS, Kusy RP: Comparison of resistance tosliding between different self-ligating brackets with sec-ond-order angulation in the dry and saliva states. Am JOrthod Dentofacial Orthop 121:472-782, 2002

2. Sims APT, Waters NE, Birnie DJ: A comparison of theforces required to produce tooth movement ex vivothrough three types of preadjusted brackets when sub-jected to determined tip or torque values. Br J Orthod21:367-373, 1994

3. Mah E, Bagby MD, Ngan PW, et al: Investigation offrictional resistance on orthodontic brackets when sub-jected to variable moments [abstract]. Am J OrthodDentofacial Orthop 123:A1, 2003

4. Miles PG, Weyant RJ, Rustveld L: A clinical trial ofDamon 2 vs conventional brackets during initial align-ment. Angle Orthod 76:480-485, 2006

5. Venezia AJ: Pure Begg and edgewise arch treatments:comparison of results. Angle Orthod 43:289-300, 1973

6. Pandis N, Polychronopoulou A, Eliades T: Self-ligatingvs conventional edgewise brackets in the treatment ofmandibular crowding. Am J Orthod Dentofacial Orthop132:208-215, 2007

7. Cash AC, Good SA, MacDonald F: An evaluation of slotsizes in orthodontic brackets—are standards as ex-pected? Angle Orthod 74:450-453, 2004

8. Bourauel C, Morina E, Eliades T: Torque capacity ofself-ligating brackets compared with standard edge-wise brackets. Abstracts of Lectures and Posters [ab-stract 115]. Amsterdam, European Orthodontic Soci-ety, 2005

9. Pandis N, Strigon S, Eliades T: Maxillary incisor torquewith conventional and self-ligating brackets: a prospec-tive clinical trial Orthod Clin Res 9:193-198, 2006

0. Eberting JJ, Straja SR, Tuncay OC: Treatment time,outcome and patient satisfaction comparisons ofDamon and conventional brackets. Clin Orthod Res4:228-234, 2001

1. Andrews LF. Straight-Wire: The concept and the appli-ance. San Diego: LA Wells and Co, 1989

2. Committee on Quality of Health Care in America, Insti-tute of Medicine: Improving the 21st century healthcaresystem, in Crossing the Quality Chasm: A New HealthSystem for the 21st Century. Washington, DC, National
Academy Press, 2001, pp 39-60

Documents

The Damon Passive Self-Ligating