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SmartTrack, Invisalign JDO 54 Fig. 10:SmartForce is effective in two ways: 1. Built into the aligner, such as power ridges designed to control torque. 2. Active surface on an optimizedattachment to control tooth movement precisely.such as a lower third molar, the active surface willface mesially (Figs. 11, 12). The force developed tobodily move any tooth must be carefully balancedwith an appropriate moment or the tooth will tip.The type of tooth movement depends on the M:Fassociated with the applied load.There are many applications for SmartForce,depending on the design of the mechanics. The five Fig. 11 :In this stage, retraction (“distalization”) of LR8 (#17) is planned. Theshape of the #17 attachment on the aligner is a little different fromthe one on the template. This configuration produces a force thatpushes on the attachment of #17. Fig. 12:The active surface on an optimized attachment produces a couplethat is designed as an anti-tip moment during space closure.basic movements for a tooth are rotation, extrusion,intrusion, torque control of the crown, and rootcontrol. If multiple types of movement are desired,there is a hierarchy for applicable attachments thatis based on the Invisalign data base. Every optimizedattachment comes with a set of rules based on thelongterm experience of the manufacturer. Doctorscan assess treatment progress, but changingoptimized attachments is not an option. However,during a refinement (reboot) procedure, optimizedattachments can be replaced with conventionalones if desired.885

JDO 54 Special TopicSmartStageIn 2015, Invisalign released G6 along with SmartStageto improve aligner performance for first premolarextraction treatment.9 SmartStage is engineered tooptimize tooth movement progression, but it is anabstract concept in mechanics that is challengingfor many clinicians. The first application is to modifythe shape of an aligner, and the other is to adjustthe sequence of tooth movement. CombiningSmartForce with SmartStage can enhance thepredictability of clinical outcomes. A carefulapplication of the method controls unwantedtipping and anterior extrusion of incisors duringretraction.10SmartStage Features1) Optimaized Aligner ShapeDistal incisor tipping ( anterior torque loss ) andbuccal segment mesial tipping ( posterior torqueloss ) are common side effects when closing firstpremolar extraction spaces.11 With fixed appliances,clinicians can reduce these side effects with archwireadjustments such as a curve of Spee adjustment,gable bends or selecting a full-size rectangulararchwire.12 Clear aligners can simulate these effectsif they are designed to change form or modify inshape. These aligner activations work together withoptimized attachments to effectively close extractionspace. These mechanics require precise engineeringto control both the moment to force ratio on eachsegment, and the equilibrium of the entire forcesystem (Fig. 13).86 Fig. 13:Aligner activation (Smar tStage) compliments optimizedattachments (SmartForce) to eliminate undesirable tippingextrusion during retraction. Magenta curved arrows are tippingmoments when closing first premolar space. Red curved arrows arecounter moments resulting from the aligner applying active forceon optimized attachments. Dark blue curved and straight arrowsshow the direction of root control in addition to preventing anteriorextrusion.

SmartTrack, Invisalign JDO 542) Optimized Tooth Movement SequenceSmartStage technology is designed to optimizealigner shape and tooth movement progress toachieve more predictable clinical outcomes. Topreserve posterior anchorage, a two-step anteriorretraction method is proposed instead of enmass space closure;13 however, this tends to be anunattractive approach because it opens maxillaryanterior spaces. Aligners can utilize this approachwithout an appreciable esthetic deficit becausealigner material fills the space during the retractionprocess. Canines are retracted about 1/3 of theextraction space and then all six anteriors areretracted later, utilizing posterior arch anchorage(Fig. 14).9 SmartStage adapted this modified two-stepanterior retraction process, although not all cliniciansaccept this approach as effective and efficient.14,15Mini-screw anchorage for en-mass retraction withaligners is another option.Attachments DesignAre attachments necessary to move teethwith aligners?Aligners can accomplish many types of toothmovement without attachments because loads areapplied to the teeth by the surrounding material.Tipping the crowns of teeth and incisor rotationrarely require any attachments. Complex toothmovement and rotation of most teeth is difficult toaccomplish without attachments. Attempting tocorrect major malocclusions without attachments is Fig. 14:SmartStage can be programmed to optimize tooth movementsequence. Invisalign G6 is designed to retract canines first for about1/3 of the predicted space closure movement. The six-anteriors arethen retracted. This approach increases treatment time but mayhelp preserve posterior anchorage. See text for details.87

JDO 54 Special Topiclikely to be frustrating for both the patient and theforces, but applying a significant moment to theclinician. Attachment design is an important aspectcrown of a tooth requires a couple, which dependsof diagnosis and treatment planning.on the active surface of an attachment. Optimizedor vertical attachments can translate teeth byTooth movement requiring attachments?1) RotationPremolars have a small contact surface and relativelyround shape, so they usually require attachments forrotation (Fig. 15).2) ExtrusionAligners use other teeth as anchorage to developextrusive force, but the mechanics are ineffectiveincreasing the moment to force ratio (M:F) of theapplied load. For pure translation, the M:F mustapproximate the equivalent force system, meaningthe moment must be adequate to simulate a forcepassing through the center of resistance of theroot. An inadequate moment results in tipping ofa tooth while an excessive moment produces rootmovement without changing the relative position ofthe tooth.unless the aligner has a firm attachment to the4) Mesial Tooth Movementsurface of the crown to be extruded. It is very difficultAnterior translation of posterior teeth such as aif not impossible to effectively extrude most teethwithout attachments.3) TranslationBodily movement (translation) requires a relativelyhigh moment to force ratio and substantialanchorage. Aligners are effective for deliveringsecond molar is very difficult because the crownheight is limited. Thus attachments are not effectivefor generating a large moment. With aligners themesial force on the molar must be relatively low toavoid overcoming the limited moment generatedby the attachment to prevent tipping the molaranteriorly. When substantial movement of molars isrequired, aligners may not be the optimal approach.Fixed appliance are much more effective in achievingsubstantial mesial translation of molars.165) IntrusionWhen intrusion is prescribed, attachments areu n n e ce s s a ry b e ca u s e t h e a l i g n e r ca n ea silydevelop intrusive force. However, there may bean undesirable extrusion of anchorage teeth.Like translation of a tooth, intrusion can easily 88Fig. 15:Attachments are required for tooth rotation, extrusion, translation,protraction (“mesialization”), and intrusion.compromise anchorage because it is much easier toextrude a tooth than to intrude it. Attachments are

SmartTrack, Invisalign JDO 54usually required, for stabilization of anchorage teethextrusion. Attachments are not required for incisorsinto segments, to resist extrusion.intrusion ( Fig. 16 ), but the premolars serving asanchorage, do require them (Fig. 17). The attachments5 Questions for Attachments DesignClinicians are often confused by attachments.There are 5 questions to help define and designappropriate auxiliaries.can be conventional (for retention) or optimized (forextrusion and retention).Molar-Intrusion AttachmentsThe intruded molars do not need any attachments1. W h a t i s t h e p l a n n e d d i r e c t i o n o f t o o t hmovement? Mesial, distal, extrusion or intrusion?2. What is the function of the attachment?because the occlusal surfaces are adequate fordelivering the axial load. However, the adjacentpremolars do need attachments to resist theAnchorage or delivering an active load?3. Which is the active surface of an attachment? Thiscalculation is critical for estimating the amount offorce and the couple generated by programmedrecoil of the aligner. The M:F, plane of forcesystem, and underlying root structure dictate thepath of tooth movement. Like archwires, alignerstie the arch together which is helpful for keepingtooth movement under control as the active Fig. 16:The blue circle indicate there is adequate surface area on each toothfor the aligner to apply the intrusive forces. Fig. 17:Attachments designed for managing deep-bite. The solid broadarrow indicates intrusive force. The dotted arrow is the resulting(counter) extrusive force.surface of attachments move individual teeth.4. Is it feasible for an active load from an alignerto produce the desired tooth movement? Forinstance, severely crowded teeth may requireextraction, arch expansion and/or enamelstripping to avoid undesirable lip protrusion.5. Is the active force parallel to the direction oftooth movement? If so, surface attachments area wise choice.Deep-bite AttachmentsThe solutions for a deep-bite are upper incisorintrusion, lower incisor intrusion, or buccal segment89

JDO 54 Special Topicresulting extrusive loads (Fig. 18). Again, attachmentson the premolars can be conventional for retention,or optimized for extrusion and retention. Fig. 18:Attachments are designed for molar intrusion (solid broad arrows)and dotted arrows show the counter extrusive forces. Fig. 19:These 3 key points allow us to monitor our treatment resulteffectively at every appointment. Fig. 20: Teeth are not fitting into the aligner (off-tracking).3 Key Points for Invisalign G6 Recall-CheckThe Invisalign G6 is well designed to support firstpremolar extraction cases. It combines the threeinnovations of Smart Technology, to provide morepredictable and efficient root alignment. Themechanics depend on carefully monitoring threekey points: 1. aligner adaptation (fit), 2. attachmentpositions, and 3. anchorage preparation (Fig. 19).Aligner Adaptation (Fit)Teeth not fitting well into an aligner is deemedoff-tracking, which is the most common problemwith Invisalign aligners (Fig. 20). The first sign of offtracking is a gap between the aligner and the incisaledges or cusps of the teeth. This may occur for tworeasons. The first is extrusion of anterior teeth wasprogrammed into the aligner, or a canine is movingdistally. Initially there will be a small space betweenthe incisal edge or cusp of the tooth and the aligner.90This is normal when the aligners are changed, butit should not be allowed to increase as an aligneris worn. For example, the patient (Fig. 21) should beadvised to bite on aligner “chewies” especially in theoff-tracked area. The second reason for off trackingmay be that aligners are changed too frequently,before the teeth have moved to the plannedposition for the next stage of treatment. The patient

SmartTrack, Invisalign JDO 54may be trying to speed up treatment by changingAttachment Positionaligners at 7-day intervals or less. The most commonG6 SmartForce features an Optimized Retractioncorrection is for the patient to wear the problemaligner 3-5 days longer to determine if adaptation isself-correcting (Fig. 22).Attachment that is designed to work withSmartStage technology to achieve effective bodilymovement during canine retraction. The multitooth unit and staging of the G6 system is a complexsystem that is not adjustable. It is an all or noneoption (Figs. 23 and 24). Fig. 23: The G6 features and biomechanics for space closure. Fig. 24:In the Invisalign treatment sheet, the blue horizontal bar meansthe multi-tooth unit that belongs to the same group and should bemaintained. The red notation indicates tooth movement desiredwith aligner treatment.Fig. 21:Patient was advised to bite on the “chewies” to seat the aligner intoan appropriate position for better adaptation.Fig. 22: Aligner adaptation problems and the relative solutions.91

JDO 54 Special Topic Fig. 25: Illustrations are shown for maximum anchorage and moderate anchorage in the G6 system.The doctor's responsibility is to carefully check everysupplemented with Class II elastics or temporaryattachment at each appointment. Any missinganchorage devices (TADs) (Fig. 26).attachment must be replaced quickly with thetemplate supplied. A full compliment of attachmentsis critical for space closure mechanics, so the patientIntegrating Aligners and Fixed Appliancesis also asked to check the tooth surfaces with a fingerAchieving precise tooth movement to resolveevery time they take out the aligner. If an attachmentmalocclusion is the primary goal for orthodontics.is lost, an appointment with the doctor is requiredAligner therapy is popular with patients, who dowithin 7 days to repair the problem.not want to wear braces, but success with theseremovable appliance is dependent on both theAnchorage PreparationThe G6 system can be programmed with SmartStagetechnology to provide maximum anchorage. Molarstability is programmed to hold the A-P positionfor achieving maximum retraction of the anteriorsegment. Moderate posterior anchorage permits 5mm of molar mesial movement (Fig. 25 ). Theseanchorage options are programmed with theClinCheck system and must be carefully examined bythe doctor prior to approval. In order to accomplishan ideal result, anchorage preparation can be92 Fig. 26:The intermaxillary elastics and TADs can be used as anchorage for abetter treatment outcome.

SmartTrack, Invisalign JDO 54doctor and patient following instructions precisely.intelligence ( AI ), a type of technology based onThe principles for applied mechanics and anchoragemassive data bases that is increasingly prevalentare the same for all tooth movement, but the clinicalin dentistry. Utilizing vast resources, Invisalign hascourse for each approach is distinct. Both archwiresdeveloped 3 innovative technologies to expand theand aligners are indeterminate mechanics17soperiodontal ligament stress throughout the arch isscope of aligner therapy and make patients morecomfortable during treatment.unknown so the precise response to applied loadsare variable. The same risks apply to aligners andAt the initial consult, patients should be encouragedarchwires: uncertain course of tooth movement,to share their chief complaint(s) so the doctor canrelatively long treatment times, and root resorption.properly diagnose the malocclusion, relative to thepatient's needs, and decide on a general treatmentThe Insignia technology for fixed applianceplan. If a fixed appliance is selected, the mechanicstreatment was the first patent in orthodontics forare described in a straight-forward manner. On thecomputer-aided design (CAD) and computer-aidedother hand, an Invisalign consolation should focusmanufacturing (CAM). However, Align Technologyon desirable outcomes and the necessity to follow(Invisalign ) was the first company to actually marketinstructions precisely. The actual mechanics areCAD/CAM appliances to move teeth. Invisalign hasdetermined by technicians, utilizing automateda long history of aligner innovations and clinicalroutines and attachments based on industrialmonitoring to improve outcomes. A trial andexperience. The process is not intuitive so the doctorerror approach is appropriate for indeterminateand the patient are not going to “ understand ” it,mechanics because the path and course for toothbut must accept the necessity to adhere to themovement cannot be calculated. Most teeth do notinstructions provided, to achieve a predictablemove precisely along the direction of the force, soclinical outcome. Some problems, mechanics, andconsiderable R&D is required to define how teethpatients may be better suited to another CAD/CAMwill move in response to a given force system. Theappliance, e.g. the Insignia system.Invisalign team have monitored many outcomes todefine the treatment scenarios available to manageAligner material is based on sophisticated polymercomplex malocclusions. Consequently, alignerscience and progressive mechanics are a stepwisetherapy is less intuitive than fixed mechanics foriterative approach for applying loads directlyboth the doctor and patient. The advice of Invisalignto teeth and/or via attachments. The greatesttechnicians is based on algorithms developed withadvantage for aligners is esthetics during treatment,a massive data base which is the actual sciencebut space management and protrusion can be aof the mechanics. One can view the process forproblem so enamel stripping and/or extractions aresophisticated aligner treatment as a form of artificialoften required. Fixed mechanics are based largely93

JDO 54 Special Topicon metals technology with an increasing emphasisuncertainty relative to planning treatment andon long range superelastic loads. The latter hasmonitoring progress. The doctor must understandsubstantial potential for controlling indeterminatethat Invisalign is a very sophisticated therapeuticmechanics to decrease treatment time for a precisesystem that is not intuitive, so the aligners must becorrection of malocclusion. In addition, most severeapplied as prescribed. If progress is disappointing,skeletal problems can be conservatively managedit may be necessary to refine (reboot) the treatmentwith determinate mechanics, that is anchored withprocess to achieve the desired outcome. Standard17extra-alveolar bone screw anchorage. It is clear thatattachments can be changed at that time becauseboth CAD/CAM technologies (Invisalign and Insignia)a new series of aligners will be made. However, it isare in the realm of a well-trained orthodontist.important for the clinician to refrain from changingmechanics while a series of aligners is being worn.In addition personalized treatment is rapidlyThe “see it and fix it” mentality that is common withadvancing, based on specific genetic andfixed appliances is inappropriate for complex aligner18treatment. Clinicians should practice and master theOrthodontist of the future must evaluate the3 check points as described in this article. The onlypatient carefully to prescribe an appropriateperiodic adjustments by the doctor are to replacetherapy. The preference of the patient will usuallyattachments, increase the time an aligner is worn, orbe the determining factor, because both CAD/to insure that the teeth are well seated in the alignerCAM approaches (aligners and fixed appliances) offerwith “chewie” exercises. The doctor and the patientexcellent outcomes. The choice for the patient ismust precisely follow instructions to benefit from theesthetic treatment with aligners, but the treatmentefficiency and precision of the prescribed treatment.environmental factors presented by the patient.time will be substantia

81 SmartTrack, Invisalign JDO 54 three diff erent varieties: 1. LD30 (0.75mm) for Invisalign aligners, 2.EX40 (1.02mm) for Vivera and Invisalign retainers, and 3. EX15 ( 0.75mm) for Invisalign templates.SmartTrack Features 1) Improved Control Align Technology reports proprietary data from a pilot study of 1015 patients at 5 months follow-up.