Improving the predicta

bility of clearaligners Steven Jay Bowman

& 20171073-87http://d

KalamaProfessor, SThe UniverProfessor, CClinical Lec

AddressKalamazooE-mail: info

Once limitations of clear aligner treatments were identified, conceptualizing

techniques to improve the predictability in producing desired results was the

next logical step. The present communication offers a variety of concepts

methods to enhance the efficiency and effectiveness of clear aligners. (Semin

Orthod 2017; 23:65–75.) & 2017 Elsevier Inc. All rights reserved.

I like predictability because I know what I’mgetting into.—Actress Katherine Heigl

Addressing limitations of clear alignertreatment

The advent of using a series of clear alignerscame at the turn of the 21st century, despite thebasis for this concept originating over 55 yearsearlier.1 Although, the original fanfare of plasticaligners equitably replacing traditional metalbraces quickly tarnished as early adoptersbecame painfully aware of limitations of theconcept.2–9 Some practitioners vacated, somevacillated, and others simply dug-in to doggedlyinvent ways to improve this innovation. Patientsdesire “braceless” correction of their smiles10 andthus far, the efforts to give them what they wanthas led to continual advances and increasingnumber of applications and adjuncts for alignersin orthodontics.11–23

Compliance, consequences, and quality oflife with clear aligners

If treatment with aligners was to be seen ascompletely successful, it was not enough tooccasionally straighten some teeth just in the

Elsevier Inc. All rights reserved.46/12/1801-$30.00/0x.doi.org/10.1053/j.sodo.2016.10.005

zoo Orthodontics, Portage, MI; Adjunct Associateaint Louis University, Saint Louis, MO; Instructor,sity of Michigan, Ann Arbor, MI; Assistant Clinicalase Western Reserve University, Cleveland, OH; Visitingturer, Seton Hill University, Greensburg, PAcorrespondence to S. Jay Bowman, DMD, MSD,Orthodontics, 1314 West Milham Ave, Portage, MI.@kalamazooorthodontics.com

Seminars in Orthodontics, Vol

esthetic zone. Predictable, consistent, and com-pleted results without adverse effects wererequirements. First and foremost was a justifiedconcern for patient compliance in wearingremovable devices during the course of possiblyyears of treatment. As Buzz Behrents cautioned,compliance is the single most important factor intreatment success.

Cooperation in wearing aligners differs fromthat of fixed braces in that wires and bracketscannot be taken off and disregarded by thepatient, so the treatment might proceed towardat least “straighter” teeth. In contrast, if alignersare not worn as prescribed, the patient receivesno result. Consequently, an alternative track forthe non-compliant patient must be a part ofinformed consent.

The introduction of so-called ComplianceIndicators for the Invisaligns (Align Technology,San Jose, CA) product was evaluated during testingof their Teen product (targeted for the audiencewith the highest concerns for adherence to wear).The soluble, color-fading dots were found to rea-sonably demonstrate if patients had been con-sistently wearing their aligners.24 If used as a“policing” device, however, much like embeddedtimers in headgears or functional appliances, theireffectiveness in actually eliciting cooperation is stillin question.24 More importantly, compliance byorthodontic patients with either braces or plastic is,on average, favorable and comparable.25 Non-compliant patients likely suffer consequences ofprolonged or compromised results no matter thetreatment method chosen.

In terms of adverse effects, although there arestill concerns for decalcification, gingivitis, rootresorption, etc., with either fixed braces orremovable aligners, the oral hygiene advantagefor removable appliances is significant; however,the trade-off is the risk of patients failing to

6523, No 1, 2017: pp 65–75

Bowman66

re-insert their aligners after eating and brushing.All in all, it was not surprising that the quality-of-life satisfaction of teen aligner patients was foundto be quite high.25

Aligner tracking

A common concern running consistentlythroughout the history of aligner treatments hasbeen that of teeth not following the predicted ordesired movement. This is despite the fact that theforces and moments produced with plastic arecomparable to those generated with fixed braces.26

For instance, Chisari et al.13 found that just 57% ofthe tooth movement programmed for a singleincisor was actually realized in a period of an 8-week investigation. In addition, researchers fromthe University of Illinois11 reported only a 41%mean accuracy of predicted tooth movement. Thereasons for these frustrations are multi-factorialand require a variety of responses to resolve. Forexample, specific teeth oft times do not remainseated within the confines of the plastic alignertrays as treatment progresses. This may produce anair gap between tooth and plastic termed “lag” or“tracking error.” Strategies to reduce “trackingerrors” will be described below.

Rohit Sachdeva has described the process oforthodontic finishing as “reducing the errors thathave accumulated during treatment.” Theseerrors can crop up quickly during the sequenceof aligners, resulting in a loss of tracking andtreatment “running off the rails.” These errorsmay include those of diagnosis and treatmentplanning, but with aligners these accrue at theoutset. They include issues with impression tak-ing, laboratory scanning of those impressions,tolerances in the creation of laboratory models(poured or printed), tolerances in the process ofthe molding of plastic over said models, limi-tations of the plastic materials themselves, and, ofcourse, inconsistent compliance.

Much like issues in manufacturing of metalwires and braces, there are tolerances permittedin fabrication that may limit the accuracy of toothmovement. The same situation occurs in moldingplastic trays, especially when “simulated/pre-dicted tooth movements” are involved. In addi-tion, thin plastic may mold around the undercutsand interproximal spaces between teeth butmight provide insufficient force to achieve thedesired tooth movement. The flexibility of the

material and its conformation from the incisaledge to the gingival margin of individual teeth,combined with the necessary duration of forcesapplied to specific teeth, can be problematic. Itseems there must be a compromise betweenheavier forces from thicker or less pliable plasticversus thinner or more resilient materials.27,28 Inany event, some tooth movements (extrusion,torque, and rotations) especially for certain teeth(maxillary laterals and cuspids) have been clearlydemonstrated to be less predictable and requireextra attention.1–3,11–13,29–32 These types of con-cerns led directly to the creation of bondedcomposite attachments with the intent toincrease the surface area for plastic aligners to“grip” onto teeth.

More importantly, the design of the sequenceand velocity of the movement of teeth duringtreatment requires the greatest consideration.Sequential or simultaneous tooth movementplans are desirable in different situations. Simplyexpecting teeth to move from start to a finishedocclusion without a specific plan in-between forhow these teeth will overcome obstacles (i.e.,collisions, contact points, occlusal and muscularforces, insufficient force, or contacts from theplastic) is unrealistic at best.9

One of the earliest adjuncts to help seat alignertrays, attempt to maintain “tracking,” and increaseocclusal forces to elicit tooth movement was theintroduction of aligner “chewies” (Chewies AlignerTray Seaters, Dentsply Raintree Essix, York,PA).15,19 These plastic “cotton rolls” are prescribedfor patients to use at least the first few days afterchanging to each new pair of aligners. Like theconcept of a tooth positioner, the patient placesthe device in a site where teeth are not tracking (i.e., a visible “air” gap is seen between the occlusal orincisal of a tooth and the aligner). The patient thenbites and holds onto the chewies repeatedly, over afew minutes of time daily, with their aligners inplace.15,19 The intent is to help seat the aligner onthe teeth that are not tracking, slightly intrude theteeth adjacent to a tooth in question, and theadded perturbations may help to accelerate theremodeling in that site to stimulate the tooth tomove as prescribed.

Lack of space

Crowded dentitions offer only two options forresolution: create more space (expand) or

Clear aligners 67

reduce tooth mass (IPR or extraction). Expan-sion implies either development or growth ofnew bone in the buccal alveolus. This maypotentially position teeth into less stable locationsdue to change in equilibrium in the facial mus-culature and an associated potential loss of boneas teeth are pushed beyond the envelope of thealveolus. Certainly, some modicum of expansionappears to be tolerable or at least “retainable.”Unfortunately, aligners tend to expand a mostunstable site: the mandibular intercaninedimension.33 IPR to reduce the dimensions ofteeth to provide for their accommodation withinthe arch perimeter is useful, but should belimited in scope. Extractions are a time-tested,evidence-based approach to resolving significantarch length discrepancies; however, the resultswith aligners have been unpredictable. Thesemore complex cases often benefit from adjunctssuch as elastics, miniscrew anchorage, or even theuse of sectional fixed braces.16,34–43

In the simplest terms, if there is insufficientspace for a tooth to move, it would not. Toprescribe the unraveling of anterior crowdingwith aligners seems such a simple procedure.Without the creation of space, the “binding”collisions or contacts between irregular incisorswill prevent movement. As noted earlier, theoptions to solve this are obvious and they can becombined (mild expansion þ mild IPR; extrac-tion þ IPR).

Selecting IPR from the outset makes littlesense, unless the original discrepancy is quiteminor. That leaves the application of somedegree of expansion (labially and laterally).Expansion to resolve minor crowding may be assimple as prescribing the opening of “visible”space (40.2 mm) between specified teeth. Thenreasonable amounts of IPR could be performedmore safely. Some perform this structuralreduction chairside with “lightning strips ordisks.” Others provide abrasive strips to patientswith prescribed directions to “floss” the stripsbetween contact points to create small amountsof space. Once space is achieved, then morepredictable correction of rotations and labiolin-gual discrepancies can be accomplished. Anysmall residual space that remains can be easilyclosed with the aligners as treatment progresses.

If extractions are chosen, then an entirelydifferent group of concerns must be addressedfrom control of anchorage, torque (root

rotation), tipping (bodily movement), and ensur-ing interproximal contacts are created at theend.35–38,44,45 The application of intramaxillaryor intramandibular elastics to miniscrews,41–43

intermaxillary elastics, and the increase in sizeand type of composite attachments may beneeded to increase predictability.16

Predictable sequencing of space closure orpushing individual teeth into alignment for anyof the previous scenarios may be best handled insmall segments of tooth movement.16,20,23 Inother words, to control anchorage in smallincrements, teeth adjacent to a specific tooth thatis out of position are prescribed to be held inplace (no movement) until the irregular one ismoved to place and so on. This detailedsequencing of small parts of a treatment plan areintended to reducing tracking errors that aresometimes experienced during simultaneousmovements of large numbers of teeth.

Rotations

It seems quite obvious that attempting to rotatesome teeth with plastic is unlikely to occur due totheir anatomy.7 For example, expecting toreliably rotate a “round” premolar seems futileunless a “handle” is placed on it to increase itsprofile asymmetrically. Molded compositeattachments46,47 have increased the predict-ability of rotational control to some degree.48,49

But, the simple application of a prominenthandle, of even a specific engineered design,cannot be depended upon without accompany-ing proper treatment planning.

The most unpredictable teeth to achieverotation for in the esthetic zone are the maxillarylaterals and cuspids11; despite the use ofseemingly enormous attachments. Rotatingthese teeth appears to require the mostattention to detailed treatment sequencing.15

Consider the typical position of a maxillarylateral incisor often accompanying a Class IIDivision 2 malocclusion. Simply prescribing thatthis tooth be “straight” at the end of alignertreatment is absurd. Space must first be createdor this tooth will simply not move. This may beaccomplished by “expansion” laterally, but alsoarch perimeter may be increased as lingual roottorque is applied to often “rabbited” centralincisors. Once visible space is open, then any

Figure 1. Ineffectual movement of a crowded and rotated central incisor due to insufficient space. Additionalspace must be created by either IPR and/or expanding to open visible space on either side of the affected tooth;otherwise, no movement is possible. Once space is created, a rotational couple is necessary to produce the desiredchange. Holding or preventing movement of the teeth adjacent to the rotated tooth in question (by staging in thesetup) and using accent pliers to place indents on opposite sides of the plastic (The Vertical pliers, ClearCollection, Hu-Friedy, Chicago, IL) may enhance the intended biomechanical effect.15,50

Bowman68

desired IPR can be provided, but no rotation ofthe incisor can be started until there is room.

The shape, size, and the position of the lateralincisor between two larger neighboring teethpreclude much contact with plastic. This is fur-ther compromised if there is a desire to extrudethe lateral and/or intrude the central incisors.There is simply insufficient retention of plasticstretched over the blade-shaped lateral. Con-sequently, a variety of attachments have beendesigned and modified for use on laterals withvarying degrees of success.48 Unless combinedwith the prerequisite creation of space, thedimensions or design of an attachment arepointless. In fact, the iatrogenic effect ofapplying these forces without space can actuallyproduce more intrusion, squeezing the toothapically; thereby, increasing tracking error.More predictable has been the introduction ofadjunctive forces from orthodontic elastics asdescribed below.

Expecting a tooth to be rotated into an idealprescribed position, using flexible plastic (withinherent errors or limits in tolerances), withoutasking for “over-rotation” also seems dubious. Forinstance, it is probably necessary to prescribe21–31 of “over-rotation” to ever be able to simplyreach “ideal.” Besides, over-correction has been atime-tested tenet in orthodontics.

Another option is to use detailing pliers (TheVertical, Clear Collection, Hu-Friedy, Chicago,IL)15,50 to produce indentations into the plasticto create accented rotational couples (Fig. 1).Finally, just because the tooth was moved to thedesired spot does not guarantee it will remain.For instance, it may be advisable to consider an

Edward’s supracrestal fiberotomy for significantlyrotated teeth that you do not want to return totheir original position (i.e., lateral incisors inClass II Division 2).

Torque and root angulation

Control of root movement with aligners has beenan unfailingly constant concern.7,51,52 Rotation ofroots (torque), bodily tooth movement, and rootparalleling have been deemed to be limitations ofapplying relatively “loose” forces with plastic.Fixed braces have the advantage of a moreintimate junction between the forces generatedby the deformation of wires bound in bracketsbonded directly to the teeth.

Plastic aligners, despite often covering themajority of surface area of teeth, still do not havethe same connection; therefore, the crown of thetooth may slip away from the plastic. Accordingly,to alter the angle of roots (moving them somedistance through bone) is much more difficultthan simple crown tipping. Complicate this withthe flexibility of plastic, including the differentialin resilience and force levels from the gingivalmargin to the occlusal of the aligners, and cre-ating rotational couples for roots become diffi-cult. If simultaneous movements of crownrotation, intrusion, extrusion, and unresolvedcrowding are added to the mix, predictability canbe problematic.

The application of torque, specifically formaxillary anterior teeth, was identified early inaligner history as unpredictable.12,32,53 As a result,most changes noted in the angle of incisorsoccurred due to “flaring,” “rounding-out the arch,”

Figure 2. Torque ridge indentations to increase theforce applied to the crown to enhance a rotationalcouple with intent to change the angulation of a tooth.These ridges can be prescribed in some commercialappliances such as Invisaligns or added using TheHorizontal pliers (Clear Collection, Hu-Friedy, Chi-cago, IL).15,50

Clear aligners 69

or facial tipping as crowding was resolved usingexpansive pushing forces. Unintended excessoverjet or bimaxillary protrusion may result. Forexample, the Class II Division 2malocclusion seemsan easy fix if you simply tip the upper centralincisors labially. Unfortunately, the resulting overjetaccompanying a straighter “social six” is not exactlywhat most patients have in mind.

The addition of so-called “torque ridges” toenhance forces for lingual root torque (limitinglabial crown tipping) was first evaluated duringthe Invisalign Teen Research project.25 Theseridges were added to the plastic at the gingivalmargin on the labial and at the incisal edge of thelingual to generate a rotational couple to tiproots palatally (and vice versa if labial root torquewas desired). These ridges can also be addedindividually anywhere along the aligner tray

Figure 3. During the Invisalign Teen Study,25 torque ridgeto affect a rotation couple to improve the predictabilityAlthough the “torque” amounts reasonably matched the plmovement may be required in order to achieve intended

using The Horizontal pliers (Clear Collection,Hu-Friedy, Chicago, IL )(Fig. 2).15,50

Results from the Teen Study25 demonstratedthat the predicted actual degrees of torqueproduced were reasonably achieved (Fig. 3).But, due to the flexibility of plastic and theinherent difficulty in moving roots through bone,prescribing over-correction of torque is sug-gested in order to just achieve the intendedangulation. In addition, caution is warranted asthese additional forces may tend to push theplastic incisally and increase tracking error.52

Keeping the trays seated onto the incisor crownsusing some programmed intrusion may improvethe response. Finally, do not ignore theunintended posterior effects from anteriortorque. Loss of posterior anchorage seen withmesial tipping and intrusion of the mesialmarginal ridge of molars may be attendant toanterior torque expression.16

What is so important about anterior torque?More attention than ever is being paid to propercoupling of upper and lower anterior teeth as thepopulation of adult orthodontic patients hasincreased. The development of crowding, coin-cident with deep overbites, is often associatedwith “upright incisors” (obtuse interincisal angle)and the constricted envelope of anterior func-tion. The long-term consequence may be sub-stantial loss of tooth structure from acombination of functional and dysfunctionalwear. Mix-in any unidentified Bolton tooth-sizediscrepancies (e.g., small maxillary lateral inci-sors), acidic diet, or gastrointestinal reflex dis-ease, and the damage to teeth can be dramatic.Consequently, it may not be simply enough toline up the front teeth in short order to only

indentations were added to aligner trays with the intentof producing desired angulation of upper incisors.

anned “setups,” prescribing over-correction of this rootgoals.

Figure 4. The American Board of Orthodonticsdetermined that the most common error noted incase reports failing the ABO examination wereinappropriate buccolingual inclination or torque ofposterior teeth.54 Attention to detail is critical in allaspects of preparing virtual set-ups (e.g., adding buccalroot torque).

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satisfy patient’s esthetic requests. Informedconsent begs proper diagnosis and treatmentplanning to address possible functional concerns.

Addressing root angulation or torque is notlimited to only anterior teeth. The AmericanBoard of Orthodontics described that the mostcommon error found in case reports that failedtheir examination was, in fact, insufficient pos-terior buccolingual inclination (posterior tor-que),54,55 a concern shared in other reports.56–59

Unless the angle of posterior teeth is specificallyaddressed in the virtual setup, an excessive curveof Wilson, prominent palatal cusps of uppers,improper posterior intercuspation with inap-propriate posterior overjet may result (Fig. 4).57

Marshall et al.56 advised, “For proper occlusion,there should be no significant differencebetween the heights of the buccal and lingualcusps of molars and premolars.”

Attention to detail in setups by evaluating theposterior teeth from the lingual view can assist incorrecting these errors. In addition, increasingposterior collisions during the completion oftreatments can significantly reduce the iatrogeniccreation of posterior open bites from “passiveposterior intrusion” that can occurby simply wearing plastic trays long-term.60 Recentchanges in some proprietary software havepermitted orthodontists to specifically addressthese issues with their own individualmanipulation of tooth movement in virtual setups.

Extrusion

Asking for extrusion where occlusal surfaces ofteeth are “capped” with plastic (without

substantial undercuts for retention) is unrealistic.At 29.6% effectiveness, extrusion was reported tobe the least accurate tooth movement withaligners.11 Without some type of retention, theplastic will simply slip occlusally or incisally,leaving the tooth behind; resulting in a loss ofaligner contact often termed “aligner lag.” Theseteeth are not lagging behind; they had no chanceto be moved. Once again, the knee-jerk reactionwas to increase the size and shape of compositeattachments to attempt to urge teeth occlusallywith bigger handles for the plastic to griponto.46,47,61 In situations where extrusion was stillnot seen, the concept of aligners itself wasblamed for the “lag” without thinking throughthe limitations and finding solutions.

If the intent is to extrude an incisor, thencertainly adequate retention of the plastic isrequired to produce the extrusive force. Wecannot expect a blade-shaped tooth to trackocclusally as if magically attracted to plastic aboveit. But, is just a more prominent attachmentsimply enough?

Tight interproximal contacts or significantcollisions (even without overlap or crowding) canstop extrusion; therefore, adequate space mustbe produced prior to attempting extrusion. Thisis especially important when considering theshape of teeth adjacent to one that is to be“pulled-up.” Incisors or canines are often nar-rower gingivally and taper to a wider dimensionincisally. In those instances, extrusion is anobvious non-starter without space creation.Finally, the application of root tip or torquealong with labiolingual positioning also playintimate roles in extrusion. Sequential toothmovement to achieve the desired vertical changeis much more complex than simply communi-cating “an order” with a lab tech to just pull thetooth occlusally.

Adjunctive forces

The addition of adjunctive forces to enhanceclear aligners is not a new idea.6 For example, theapplication of orthodontic elastics to enhance orfacilitate various biomechanics was the earliestand most obvious addition. But, attempting toimprove aligner “tracking” and reduce the so-called “lag” for certain teeth has been the mostperpetual dilemma affecting predictable results.Much like using intermaxillary elastics with

Figure 5. Preparing bootstrap biomechanics.15,62 Tear Drop pliers are used to cut notches in mesial and distalembrasures of the aligner plastic. Hole Punch pliers clear the aligner plastic to allow the addition of a bondedbutton. Orthodontic elastics are stretched from the button to the teardrop notches or, alternatively, to anotherbutton bonded on the opposite side of the tooth. (Clear Collection pliers, Hu-Friedy, Chicago, IL).

Clear aligners 71

braces to increase intercuspation when produc-ing a solid final occlusion, a combination ofbonded buttons and elastics can also be used withclear aligners. In these scenarios, buttons bondedon the buccal surfaces of posterior teeth can beused to apply “triangle, box, or up-and-down”elastics to seat teeth into the aligners and into thefinal occlusion prescribed in the setup.15,62

Therefore, the application of orthodontic elas-tics that are connected to the aligner plastic,bonded buttons on teeth, or to miniscrewanchors have increased the variety of achievablemovements possible.

Bootstrapping for predictability

The predictability of single tooth extrusion and/or rotation can be enhanced using orthodonticelastics in a so-called “bootstrap” arrangement.63

Bootstrap mechanics involve placing bondedbuttons at the gingival margin on the facial,lingual, or both surfaces of a tooth that islagging.15,62 An orthodontic elastic is then

stretched across the occlusal surface of the seatedclear aligner to attach to buttons and/or notchescut into the tray on opposite sides. The gingivalmargin of the aligner plastic must be relieved toavoid the buttons so as to permit the tray to seatfully (Figs. 5 and 6).

Intrusion of a segment of teeth can also besupported using elastics supported by miniscrewanchorage. The possibilities include applying theorthodontic elastics or chain from buccal and/orpalatal elastics to buttons bonded to teeth (whilerelieving plastic from the trays to avoid thoseattachments).15,62 As an example, bonded but-tons can be placed at the gingival margin of allincisors (for a patient with a deep overbite) or ofmolars (for hypererupted posteriors). Ortho-dontic elastics from those buttons are stretchedto miniscrews inserted interradicularly apical tothe teeth to be intruded.15

Posterior intrusion to enhance the closure ofanterior open bites is another option with elasticsand miniscrews. Sequential intrusion of posteriorteeth combined with some extrusion of anterior

Figure 6. Bootstrap mechanics15,62 to forcibly erupt “lagging” teeth using orthodontic elastics. Adult female withClass II Division 2 malocclusion, deep overbite, crowding, rotations, and uneven maxillary anterior teeth. Initially,Invisaligns treatment featured angulated, horizontal beveled attachments bonded to the facial of the lateralincisors.48 After limited improvement noted in the overbite, torque of central incisors, and extrusion/rotation ofthe lateral incisors, a bootstrap setup was created at “refinement.” Clear buttons were bonded at gingival margin onthe facial and metal buttons on the lingual of both upper laterals. Plastic was relieved from the aligners toaccommodate those buttons using The Hole Punch pliers.62 Orthodontic elastics were stretched from the lingualto the palatal buttons across the seated plastic aligners. The virtual setup featured arch expansion with visible spacecreated adjacent to the laterals, forced extrusion of the laterals, intrusion and torque for central incisors, intrusionof lower anterior teeth, and over-rotation for the lateral incisors.15

Bowman72

teeth to increase the curve of Spee22,23 can bereinforced with bootstrap elastics. In this sce-nario, elastics are stretched across the occlusal ofseated aligners from miniscrews to buttons,notches in trays, or to another miniscrew in boneon the other side of the alveolus.15

Skeletal discrepancies

Addressing skeletal discrepancies were originallyseen to be an anathema to be avoided withaligners.3,4 Only limited changes in over orunderjet were attempted with aligners, whileexpecting little if any anteroposterior correc-tion.64,65 Later, maxillary posterior distalizationwas attempted, but without consideration ofanchorage concerns. This led to the applicationof intermaxillary Class II elastics to make-shiftnotches cut into the plastic trays, then to buttonsbonded to the trays, and finally to buttonsdirectly bonded to the teeth (or some combi-nation of those options).20 Once elastics werefound to improve the chance of orthodonticmovement for Class IIs, then employingsequential molar distalization supported byelastics20 was a logical strategy that has provensuccessful with aligners.66 Currently, elastics onaligners have found their way into correctingClass IIs, IIIs, and open bites; especially forgrowing individuals.

Other options for improving the predictabilityof skeletal correction have included “pre-cursor”adjuncts used prior to beginning clear aligners.These have included the use of the Carrière arm(Carrière Distalizer, Ortho Organizers, HenrySchein, Melville, NY) to hold Class II elastics todistalize posterior segments14,67,68 or typical,stand-alone distalizers, such as the Pendulum orDistal Jet. Any of these devices may be supple-mented with miniscrew anchorage to avoidreciprocal adverse effects.

For example, the Horseshoe Jet (SpecialtyLabs, Atlanta, GA), is a laboratory modification ofthe Distal Jet (American Orthodontics, Sheboy-gan, WI), supported by miniscrews. Theseappliances are used to produce molar distaliza-tion14,69–72 prior to initiating clear alignertreatment. After posterior teeth are moved into aClass I occlusion, clear aligners are prescribed tohold the molars in place while the remaininganterior teeth are retracted; just as they would bewith fixed braces. This retraction is often sup-ported with Class II elastics or even Class Iintramaxillary elastics from miniscrews to reducethe possibility of anchorage loss.14,50,71

Finally, the introduction of a variety ofmethods intended to accelerate the rate of toothmovement have arisen in recent years. Forexample, the use of a device to produce micro-vibrations or perturbations (AcceleDent,

Clear aligners 73

OrthoAccel, Bellaire, TX) with the intent ofstimulating tooth movement has been anecdo-tally described to reduce treatment time withclear aligners, warranting further research.16,43,73

Predicting the future of clear aligners

Technology has continued to improve clearaligner treatments since their inception.Replacing impressions with increasingly moreaccurate intraoral scanners, 3D printing insteadof plaster models, individual tooth movementand staging in virtual setups, and improvementsin aligner materials and attachments are allexamples of recent advancements. Simulta-neously, general practitioners with limitedtraining are providing more “social six” treat-ments (disregarding the fit and function ofteeth) and nearly every orthodontic lab (in or outof the orthodontist’s practice) is offering sometype of clear plastic product. Can all options(specialist or general dentist; scanner withcomputer setup versus bench model setup)provide equal or similar results? Clearly, alignertreatments are here to stay, but are we all equallytrained to serve the best interests of our patientsusing these devices or are some depending uponlab techs to provide the diagnosis and prescribethe treatment plan? All practitioners simply needto be as honest with ourselves as we are with thosethat choose to have us treat them.

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