Improving the predictability of Steven Jay Bowman

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.

like predictability because I know what I’m esthetic zone. Predictable, consistent, and com- I getting into. pleted results without adverse effects were —Actress Katherine Heigl requirements. First and foremost was a justified concern for patient compliance in wearing removable devices during the course of possibly Addressing limitations of clear aligner years of treatment. As Buzz Behrents cautioned, treatment compliance is the single most important factor in treatment success. The advent of using a series of clear aligners Cooperation in wearing aligners differs from came at the turn of the 21st century, despite the that of fixed braces in that wires and brackets basis for this concept originating over 55 years cannot be taken off and disregarded by the earlier.1 Although, the original fanfare of plastic patient, so the treatment might proceed toward aligners equitably replacing traditional metal at least “straighter” teeth. In contrast, if aligners braces quickly tarnished as early adopters are not worn as prescribed, the patient receives became painfully aware of limitations of the – no result. Consequently, an alternative track for concept.2 9 Some practitioners vacated, some the non-compliant patient must be a part of vacillated, and others simply dug-in to doggedly informed consent. invent ways to improve this innovation. Patients 10 The introduction of so-called Compliance desire “braceless” correction of their smiles and s Indicators for the Invisalign (Align Technology, thus far, the efforts to give them what they want San Jose, CA) product was evaluated during testing has led to continual advances and increasing of their Teen product (targeted for the audience number of applications and adjuncts for aligners – with the highest concerns for adherence to wear). in .11 23 The soluble, color-fading dots were found to rea- sonably demonstrate if patients had been con- Compliance, consequences, and quality of sistently wearing their aligners.24 If used as a life with clear aligners “policing” device, however, much like embedded timers in headgears or functional appliances, their If treatment with aligners was to be seen as effectiveness in actually eliciting cooperation is still completely successful, it was not enough to in question.24 More importantly, compliance by occasionally straighten some teeth just in the orthodontic patients with either braces or plastic is, on average, favorable and comparable.25 Non- Kalamazoo Orthodontics, Portage, MI; Adjunct Associate compliant patients likely suffer consequences of Professor, Saint Louis University, Saint Louis, MO; Instructor, The University of Michigan, Ann Arbor, MI; Assistant Clinical prolonged or compromised results no matter the Professor, Case Western Reserve University, Cleveland, OH; Visiting treatment method chosen. Clinical Lecturer, Seton Hill University, Greensburg, PA In terms of adverse effects, although there are Address correspondence to S. Jay Bowman, DMD, MSD, still concerns for decalcification, gingivitis, root Kalamazoo Orthodontics, 1314 West Milham Ave, Portage, MI. resorption, etc., with either fixed braces or E-mail: [email protected] & removable aligners, the oral hygiene advantage 2017 Elsevier Inc. All rights reserved. fi 1073-8746/12/1801-$30.00/0 for removable appliances is signi cant; however, http://dx.doi.org/10.1053/j.sodo.2016.10.005 the trade-off is the risk of patients failing to

Seminars in Orthodontics, Vol 23, No 1, 2017: pp 65–75 65 66 Bowman re-insert their aligners after eating and brushing. material and its conformation from the incisal All in all, it was not surprising that the quality-of- edge to the gingival margin of individual teeth, life satisfaction of teen aligner patients was found combined with the necessary duration of forces to be quite high.25 applied to specific teeth, can be problematic. It seems there must be a compromise between Aligner tracking heavier forces from thicker or less pliable plastic versus thinner or more resilient materials.27,28 In A common concern running consistently any event, some tooth movements (extrusion, throughout the history of aligner treatments has torque, and rotations) especially for certain teeth been that of teeth not following the predicted or (maxillary laterals and cuspids) have been clearly desired movement. This is despite the fact that the demonstrated to be less predictable and require – – – forces and moments produced with plastic are extra attention.1 3,11 13,29 32 These types of con- comparable to those generated with fixed braces.26 cerns led directly to the creation of bonded For instance, Chisari et al.13 found that just 57% of composite attachments with the intent to the tooth movement programmed for a single increase the surface area for plastic aligners to incisor was actually realized in a period of an 8- “grip” onto teeth. week investigation. In addition, researchers from More importantly, the design of the sequence the University of Illinois11 reported only a 41% and velocity of the movement of teeth during mean accuracy of predicted tooth movement. The treatment requires the greatest consideration. reasons for these frustrations are multi-factorial Sequential or simultaneous tooth movement and require a variety of responses to resolve. For plans are desirable in different situations. Simply example, specific teeth oft times do not remain expecting teeth to move from start to a finished seated within the confines of the plastic aligner occlusion without a specific plan in-between for trays as treatment progresses. This may produce an how these teeth will overcome obstacles (i.e., air gap between tooth and plastic termed “lag” or collisions, contact points, occlusal and muscular “tracking error.” Strategies to reduce “tracking forces, insufficient force, or contacts from the errors” will be described below. plastic) is unrealistic at best.9 Rohit Sachdeva has described the process of One of the earliest adjuncts to help seat aligner orthodontic finishing as “reducing the errors that trays, attempt to maintain “tracking,” and increase have accumulated during treatment.” These occlusal forces to elicit tooth movement was the errors can crop up quickly during the sequence introduction of aligner “chewies” (Chewies Aligner of aligners, resulting in a loss of tracking and Tray Seaters, Dentsply Raintree Essix, York, treatment “running off the rails.” These errors PA).15,19 These plastic “cotton rolls” are prescribed may include those of diagnosis and treatment for patients to use at least the first few days after planning, but with aligners these accrue at the changing to each new pair of aligners. Like the outset. They include issues with impression tak- concept of a tooth positioner, the patient places ing, laboratory scanning of those impressions, the device in a site where teeth are not tracking (i. tolerances in the creation of laboratory models e., a visible “air” gap is seen between the occlusal or (poured or printed), tolerances in the process of incisalofatoothandthealigner).Thepatientthen the molding of plastic over said models, limi- bites and holds onto the chewies repeatedly, over a tations of the plastic materials themselves, and, of few minutes of time daily, with their aligners in course, inconsistent compliance. place.15,19 The intent is to help seat the aligner on Much like issues in manufacturing of metal the teeth that are not tracking, slightly intrude the wires and braces, there are tolerances permitted teethadjacenttoatoothinquestion,andthe in fabrication that may limit the accuracy of tooth added perturbations may help to accelerate the movement. The same situation occurs in molding remodeling in that site to stimulate the tooth to plastic trays, especially when “simulated/pre- move as prescribed. dicted tooth movements” are involved. In addi- tion, thin plastic may mold around the undercuts Lack of space and interproximal spaces between teeth but might provide insufficient force to achieve the Crowded dentitions offer only two options for desired tooth movement. The flexibility of the resolution: create more space (expand) or Clear aligners 67 reduce tooth mass (IPR or extraction). Expan- rotation), tipping (bodily movement), and ensur- sion implies either development or growth of ing interproximal contacts are created at the – new bone in the buccal alveolus. This may end.35 38,44,45 The application of intramaxillary – potentially position teeth into less stable locations or intramandibular to miniscrews,41 43 due to change in equilibrium in the facial mus- intermaxillary elastics, and the increase in size culature and an associated potential loss of bone and type of composite attachments may be as teeth are pushed beyond the envelope of the needed to increase predictability.16 alveolus. Certainly, some modicum of expansion Predictable sequencing of space closure or appears to be tolerable or at least “retainable.” pushing individual teeth into alignment for any Unfortunately, aligners tend to expand a most of the previous scenarios may be best handled in unstable site: the mandibular intercanine small segments of tooth movement.16,20,23 In dimension.33 IPR to reduce the dimensions of other words, to control in small teeth to provide for their accommodation within increments, teeth adjacent to a specific tooth that the arch perimeter is useful, but should be is out of position are prescribed to be held in limited in scope. Extractions are a time-tested, place (no movement) until the irregular one is evidence-based approach to resolving significant moved to place and so on. This detailed arch length discrepancies; however, the results sequencing of small parts of a treatment plan are with aligners have been unpredictable. These intended to reducing tracking errors that are more complex cases often benefit from adjuncts sometimes experienced during simultaneous such as elastics, miniscrew anchorage, or even the movements of large numbers of teeth. – use of sectional fixed braces.16,34 43 In the simplest terms, if there is insufficient space for a tooth to move, it would not. To Rotations prescribe the unraveling of anterior crowding with aligners seems such a simple procedure. It seems quite obvious that attempting to rotate Without the creation of space, the “binding” some teeth with plastic is unlikely to occur due to collisions or contacts between irregular incisors their anatomy.7 For example, expecting to will prevent movement. As noted earlier, the reliably rotate a “round” premolar seems futile options to solve this are obvious and they can be unless a “handle” is placed on it to increase its combined (mild expansion þ mild IPR; extrac- profile asymmetrically. Molded composite tion þ IPR). attachments46,47 have increased the predict- Selecting IPR from the outset makes little ability of rotational control to some degree.48,49 sense, unless the original discrepancy is quite But, the simple application of a prominent minor. That leaves the application of some handle, of even a specific engineered design, degree of expansion (labially and laterally). cannot be depended upon without accompany- Expansion to resolve minor crowding may be as ing proper treatment planning. simple as prescribing the opening of “visible” The most unpredictable teeth to achieve space (40.2 mm) between specified teeth. Then rotation for in the esthetic zone are the maxillary reasonable amounts of IPR could be performed laterals and cuspids11; despite the use of more safely. Some perform this structural seemingly enormous attachments. Rotating reduction chairside with “lightning strips or these teeth appears to require the most disks.” Others provide abrasive strips to patients attention to detailed treatment sequencing.15 with prescribed directions to “floss” the strips Consider the typical position of a maxillary between contact points to create small amounts lateral incisor often accompanying a Class II of space. Once space is achieved, then more Division 2 . Simply prescribing that predictable correction of rotations and labiolin- this tooth be “straight” at the end of aligner gual discrepancies can be accomplished. Any treatment is absurd. Space must first be created small residual space that remains can be easily or this tooth will simply not move. This may be closed with the aligners as treatment progresses. accomplished by “expansion” laterally, but also If extractions are chosen, then an entirely arch perimeter may be increased as lingual root different group of concerns must be addressed torque is applied to often “rabbited” central from control of anchorage, torque (root incisors. Once visible space is open, then any 68 Bowman

Figure 1. Ineffectual movement of a crowded and rotated central incisor due to insufficient space. Additional space 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 desired change. Holding or preventing movement of the teeth adjacent to the rotated tooth in question (by staging in the setup) and using accent pliers to place indents on opposite sides of the plastic (The Vertical pliers, Clear Collection, Hu-Friedy, Chicago, IL) may enhance the intended biomechanical effect.15,50 desired IPR can be provided, but no rotation of Edward’s supracrestal fiberotomy for significantly the incisor can be started until there is room. rotated teeth that you do not want to return to The shape, size, and the position of the lateral their original position (i.e., lateral incisors in incisor between two larger neighboring teeth Class II Division 2). preclude much contact with plastic. This is fur- ther compromised if there is a desire to extrude Torque and root angulation the lateral and/or intrude the central incisors. There is simply insufficient retention of plastic Control of root movement with aligners has been stretched over the blade-shaped lateral. Con- an unfailingly constant concern.7,51,52 Rotation of sequently, a variety of attachments have been roots (torque), bodily tooth movement, and root designed and modified for use on laterals with paralleling have been deemed to be limitations of varying degrees of success.48 Unless combined applying relatively “loose” forces with plastic. with the prerequisite creation of space, the Fixed braces have the advantage of a more dimensions or design of an attachment are intimate junction between the forces generated pointless. In fact, the iatrogenic effect of by the deformation of wires bound in brackets applying these forces without space can actually bonded directly to the teeth. produce more , squeezing the tooth Plastic aligners, despite often covering the apically; thereby, increasing tracking error. majority of surface area of teeth, still do not have More predictable has been the introduction of the same connection; therefore, the crown of the adjunctive forces from orthodontic elastics as tooth may slip away from the plastic. Accordingly, described below. to alter the angle of roots (moving them some Expecting a tooth to be rotated into an ideal distance through bone) is much more difficult prescribed position, using flexible plastic (with than simple crown tipping. Complicate this with inherent errors or limits in tolerances), without the flexibility of plastic, including the differential asking for “over-rotation” also seems dubious. For in resilience and force levels from the gingival instance, it is probably necessary to prescribe margin to the occlusal of the aligners, and cre- 21–31 of “over-rotation” to ever be able to simply ating rotational couples for roots become diffi- reach “ideal.” Besides, over-correction has been a cult. If simultaneous movements of crown time-tested tenet in orthodontics. rotation, intrusion, extrusion, and unresolved Another option is to use detailing pliers (The crowding are added to the mix, predictability can Vertical, Clear Collection, Hu-Friedy, Chicago, be problematic. IL)15,50 to produce indentations into the plastic The application of torque, specifically for to create accented rotational couples (Fig. 1). maxillary anterior teeth, was identified early in Finally, just because the tooth was moved to the aligner history as unpredictable.12,32,53 As a result, desired spot does not guarantee it will remain. most changes noted in the angle of incisors For instance, it may be advisable to consider an occurred due to “flaring,”“rounding-out the arch,” Clear aligners 69

using The Horizontal pliers (Clear Collection, Hu-Friedy, Chicago, IL )(Fig. 2).15,50 Results from the Teen Study25 demonstrated that the predicted actual degrees of torque produced were reasonably achieved (Fig. 3). But, due to the flexibility of plastic and the inherent difficulty in moving roots through bone, prescribing over-correction of torque is sug- gested in order to just achieve the intended angulation. In addition, caution is warranted as these additional forces may tend to push the 52 Figure 2. Torque ridge indentations to increase the plastic incisally and increase tracking error. force applied to the crown to enhance a rotational Keeping the trays seated onto the incisor crowns couple with intent to change the angulation of a tooth. using some programmed intrusion may improve These ridges can be prescribed in some commercial s the response. Finally, do not ignore the appliances such as Invisalign or added using The unintended posterior effects from anterior Horizontal pliers (Clear Collection, Hu-Friedy, Chi- cago, IL).15,50 torque. Loss of posterior anchorage seen with mesial tipping and intrusion of the mesial marginal ridge of molars may be attendant to or facial tipping as crowding was resolved using anterior torque expression.16 expansive pushing forces. Unintended excess What is so important about anterior torque? overjet or bimaxillary protrusion may result. For More attention than ever is being paid to proper example, the Class II Division 2 malocclusion seems coupling of upper and lower anterior teeth as the an easy fix if you simply tip the upper central population of adult orthodontic patients has incisors labially. Unfortunately, the resulting overjet increased. The development of crowding, coin- accompanying a straighter “social six” is not exactly cident with deep , is often associated what most patients have in mind. with “upright incisors” (obtuse interincisal angle) The addition of so-called “torque ridges” to and the constricted envelope of anterior func- enhance forces for lingual root torque (limiting tion. The long-term consequence may be sub- labial crown tipping) was first evaluated during stantial loss of tooth structure from a the Invisalign Teen Research project.25 These combination of functional and dysfunctional ridges were added to the plastic at the gingival wear. Mix-in any unidentified Bolton tooth-size margin on the labial and at the incisal edge of the discrepancies (e.g., small maxillary lateral inci- lingual to generate a rotational couple to tip sors), acidic diet, or gastrointestinal reflex dis- roots palatally (and vice versa if labial root torque ease, and the damage to teeth can be dramatic. was desired). These ridges can also be added Consequently, it may not be simply enough to individually anywhere along the aligner tray line up the front teeth in short order to only

Figure 3. During the Invisalign Teen Study,25 torque ridge indentations were added to aligner trays with the intent to affect a rotation couple to improve the predictability of producing desired angulation of upper incisors. Although the “torque” amounts reasonably matched the planned “setups,” prescribing over-correction of this root movement may be required in order to achieve intended goals. 70 Bowman

substantial undercuts for retention) is unrealistic. At 29.6% effectiveness, extrusion was reported to be the least accurate tooth movement with aligners.11 Without some type of retention, the plastic will simply slip occlusally or incisally, leaving the tooth behind; resulting in a loss of aligner contact often termed “aligner lag.” These teeth are not lagging behind; they had no chance Figure 4. The American Board of Orthodontics to be moved. Once again, the knee-jerk reaction determined that the most common error noted in was to increase the size and shape of composite case reports failing the ABO examination were attachments to attempt to urge teeth occlusally inappropriate buccolingual inclination or torque of with bigger handles for the plastic to grip 54 posterior teeth. Attention to detail is critical in all onto.46,47,61 In situations where extrusion was still aspects of preparing virtual set-ups (e.g., adding buccal root torque). not seen, the concept of aligners itself was blamed for the “lag” without thinking through the limitations and finding solutions. satisfy patient’s esthetic requests. Informed If the intent is to extrude an incisor, then consent begs proper diagnosis and treatment certainly adequate retention of the plastic is planning to address possible functional concerns. required to produce the extrusive force. We Addressing root angulation or torque is not cannot expect a blade-shaped tooth to track limited to only anterior teeth. The American occlusally as if magically attracted to plastic above Board of Orthodontics described that the most it. But, is just a more prominent attachment common error found in case reports that failed simply enough? their examination was, in fact, insufficient pos- Tight interproximal contacts or significant terior buccolingual inclination (posterior tor- collisions (even without overlap or crowding) can – que),54,55 a concern shared in other reports.56 59 stop extrusion; therefore, adequate space must Unless the angle of posterior teeth is specifically be produced prior to attempting extrusion. This addressed in the virtual setup, an excessive curve is especially important when considering the of Wilson, prominent palatal cusps of uppers, shape of teeth adjacent to one that is to be improper posterior intercuspation with inap- “pulled-up.” Incisors or canines are often nar- propriate posterior overjet may result (Fig. 4).57 rower gingivally and taper to a wider dimension Marshall et al.56 advised, “For proper occlusion, incisally. In those instances, extrusion is an there should be no significant difference obvious non-starter without space creation. between the heights of the buccal and lingual Finally, the application of root tip or torque cusps of molars and premolars.” along with labiolingual positioning also play Attention to detail in setups by evaluating the intimate roles in extrusion. Sequential tooth posterior teeth from the lingual view can assist in movement to achieve the desired vertical change correcting these errors. In addition, increasing is much more complex than simply communi- posterior collisions during the completion of cating “an order” with a lab tech to just pull the treatments can significantly reduce the iatrogenic tooth occlusally. creation of posterior open bites from “passive ” posterior intrusion that can occur Adjunctive forces by simply wearing plastic trays long-term.60 Recent changes in some proprietary software have The addition of adjunctive forces to enhance permitted orthodontists to specifically address clear aligners is not a new idea.6 For example, the these issues with their own individual application of orthodontic elastics to enhance or manipulationoftoothmovementinvirtualsetups. facilitate various biomechanics was the earliest and most obvious addition. But, attempting to “ ” Extrusion improve aligner tracking and reduce the so- called “lag” for certain teeth has been the most Asking for extrusion where occlusal surfaces of perpetual dilemma affecting predictable results. teeth are “capped” with plastic (without Much like using intermaxillary elastics with Clear aligners 71

Figure 5. Preparing bootstrap biomechanics.15,62 Tear Drop pliers are used to cut notches in mesial and distal embrasures of the aligner plastic. Hole Punch pliers clear the aligner plastic to allow the addition of a bonded button. Orthodontic elastics are stretched from the button to the teardrop notches or, alternatively, to another button bonded on the opposite side of the tooth. (Clear Collection pliers, Hu-Friedy, Chicago, IL). braces to increase intercuspation when produc- stretched across the occlusal surface of the seated ing a solid final occlusion, a combination of clear aligner to attach to buttons and/or notches bonded buttons and elastics can also be used with cut into the tray on opposite sides. The gingival clear aligners. In these scenarios, buttons bonded margin of the aligner plastic must be relieved to on the buccal surfaces of posterior teeth can be avoid the buttons so as to permit the tray to seat used to apply “triangle, box, or up-and-down” fully (Figs. 5 and 6). elastics to seat teeth into the aligners and into the Intrusion of a segment of teeth can also be final occlusion prescribed in the setup.15,62 supported using elastics supported by miniscrew Therefore, the application of orthodontic elas- anchorage. The possibilities include applying the tics that are connected to the aligner plastic, orthodontic elastics or chain from buccal and/or bonded buttons on teeth, or to miniscrew palatal elastics to buttons bonded to teeth (while anchors have increased the variety of achievable relieving plastic from the trays to avoid those movements possible. attachments).15,62 As an example, bonded but- tons can be placed at the gingival margin of all Bootstrapping for predictability incisors (for a patient with a deep ) or of molars (for hypererupted posteriors). Ortho- The predictability of single tooth extrusion and/ dontic elastics from those buttons are stretched or rotation can be enhanced using orthodontic to miniscrews inserted interradicularly apical to elastics in a so-called “bootstrap” arrangement.63 the teeth to be intruded.15 Bootstrap mechanics involve placing bonded Posterior intrusion to enhance the closure of buttons at the gingival margin on the facial, anterior open bites is another option with elastics lingual, or both surfaces of a tooth that is and miniscrews. Sequential intrusion of posterior lagging.15,62 An orthodontic elastic is then teeth combined with some extrusion of anterior 72 Bowman

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

teeth to increase the curve of Spee22,23 can be Other options for improving the predictability reinforced with bootstrap elastics. In this sce- of skeletal correction have included “pre-cursor” nario, elastics are stretched across the occlusal of adjuncts used prior to beginning clear aligners. seated aligners from miniscrews to buttons, These have included the use of the Carrière arm notches in trays, or to another miniscrew in bone (Carrière Distalizer, Ortho Organizers, Henry on the other side of the alveolus.15 Schein, Melville, NY) to hold Class II elastics to distalize posterior segments14,67,68 or typical, Skeletal discrepancies stand-alone distalizers, such as the Pendulum or Distal Jet. Any of these devices may be supple- Addressing skeletal discrepancies were originally mented with miniscrew anchorage to avoid seen to be an anathema to be avoided with reciprocal adverse effects. aligners.3,4 Only limited changes in over or For example, the Horseshoe Jet (Specialty underjet were attempted with aligners, while Labs, Atlanta, GA), is a laboratory modification of expecting little if any anteroposterior correc- the Distal Jet (American Orthodontics, Sheboy- tion.64,65 Later, maxillary posterior distalization gan, WI), supported by miniscrews. These was attempted, but without consideration of appliances are used to produce molar distaliza- – anchorage concerns. This led to the application tion14,69 72 prior to initiating clear aligner of intermaxillary Class II elastics to make-shift treatment. After posterior teeth are moved into a notches cut into the plastic trays, then to buttons Class I occlusion, clear aligners are prescribed to bonded to the trays, and finally to buttons hold the molars in place while the remaining directly bonded to the teeth (or some combi- anterior teeth are retracted; just as they would be nation of those options).20 Once elastics were with fixed braces. This retraction is often sup- found to improve the chance of orthodontic ported with Class II elastics or even Class I movement for Class IIs, then employing intramaxillary elastics from miniscrews to reduce sequential supported by the possibility of anchorage loss.14,50,71 elastics20 was a logical strategy that has proven Finally, the introduction of a variety of successful with aligners.66 Currently, elastics on methods intended to accelerate the rate of tooth aligners have found their way into correcting movement have arisen in recent years. For Class IIs, IIIs, and open bites; especially for example, the use of a device to produce micro- growing individuals. vibrations or perturbations (AcceleDent, Clear aligners 73

OrthoAccel, Bellaire, TX) with the intent of 7. Rossini G, Parrini S, Castroflorio T, Deregibus A, fi stimulating tooth movement has been anecdo- Debernardi CL. Ef cacy of clear aligners in controlling orthodontic tooth movement: a systematic review. Angle tally described to reduce treatment time with – 16,43,73 Orthod. 2015;85(5):881 889. http://dx.doi.org/10.2319/ clear aligners, warranting further research. 061614-436.1 [Epub 2014 Nov 20]. 8. Lagravère MO, Flores-Mir C. The treatment effects of Invisalign orthodontic aligners: a systematic review. JAm – Predicting the future of clear aligners Dent Assoc. 2005;136(12):1724 1729. 9. Buschang PH, Ross M, Shaw SG, Crosby D, Campbell PM. Technology has continued to improve clear Predicted and actual end-of-treatment occlusion pro- aligner treatments since their inception. duced with aligner therapy. 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