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Treatment With Invisalign

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  • 8/4/2019 Treatment With Invisalign


    Single-lower-incisor extrac-

    tion cases have rarely beenpublished, perhaps because thereare few patients who meet thestandards for such treatment.The following diagnostic char-acteristics are usually requiredfor single lower incisor extrac-tions: Class I molar relationship. Moderately crowded lower in-cisors. Mild or no crowding in the

    upper arch. Acceptable soft-tissue profile. Minimal to moderate overbiteand overjet. Minimal growth potential. A tooth-size discrepancy, suchas missing lateral incisors or peglaterals, that can be used to re-solve the inevitable tooth-sizediscrepancy without interproxi-

    mal stripping.1

    In any such case, a full di-agnostic setup should be made toensure the occlusal results willbe acceptable.1 Unfortunately,diagnostic setups usually involvelong and laborious laboratoryprocedures of cutting, setting,and waxing the teeth in place. Inaddition, conventional methodsof tooth repositioning with re-movable appliances require al-teration of the casts by resetting

    the teeth, or by scraping awayplaster from the teeth to bemoved and blocking out spacefor them with wax.2

    New diagnostic softwarenow makes it simple, quick, andefficient to perform virtual set-ups using the Invisalign Sys-tem,* an alternative to tradition-al orthodontic appliances. This

    article will show how a series of

    clear aligners can sequentiallymove teeth from start to finish ina case involving a single lowerincisor extraction.


    A 24-year-old female pre-sented with a chief concern oflower incisor crowding. Shehad undergone orthodontic treat-ment 10 years previously and

    had recently had gingival graftson her upper and lower anteriorteeth.

    Clinical examination re-vealed full incompetent lips withthe chin deviated to the right(Fig. 1). The patient had a

    VOLUME XXXVI NUMBER 2 2002 JCO, Inc. 95


    Lower Incisor Extraction Treatmentwith the Invisalign SystemROSS J. MILLER, DDS, MSTRANG T. DUONG, DDS, MSMITRA DERAKHSHAN, DDS, MS

    Dr. Miller Dr. Duong Dr. Derakhshan

    Dr. Miller is Chief Clinical Officer, Dr. Duong is Director ofClinical Research, and Dr. Derakhshan is a Staff Orthodontist,Align Technology, Inc., 851 Martin Ave., Santa Clara, CA 95050.The authors are shareholders in the company. Dr. Duong is alsoin the private practice of orthodontics in Manteca, CA. ContactDr. Miller at

    *Registered trademark of Align Technology,Inc., 851 Martin Ave., Santa Clara, CA


    p/u 4/00,p. 203

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    Fig. 1 24-year-old female patient before treatment.

    Lower Incisor Extraction Treatment with the Invisalign System

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    straight profile with mentalismuscle strain; on smiling, shedisplayed 100% of her incisorsand 1mm of gingiva. The molarand canine relationships wereClass I. The patient had a 10%overbite and 3mm overjet, withthe lower midline shifted 3mm tothe right. Good oral hygiene wasevident, although slight gingivalrecession was found in the areasof the upper first bicuspids and

    the lower right lateral incisor.The maxillary arch was

    well aligned, with a peg-shapedleft lateral incisor; Bolton analy-sis indicated a maxillary tooth-size deficiency of 1mm. Bothcuspids showed occlusal wear,and the right second bicuspidwas lingually positioned and ro-tated mesially. There was 5mmof crowding in the lower anteriorregion, with lingually tipped

    lower cuspids and right secondbicuspid.The radiographic analysis

    showed a full permanent adultdentition with previous extrac-tion of third molars and minorrestorations. The patient hadmild generalized bone loss withnormal root morphology andlength. Cephalometric findingsincluded a well-positioned max-illa and slightly prognathicmandible, resulting in a slightlyexcessive sagittal jaw relation-ship or Class III tendency (Table1). The upper and lower incisorswere protrusive and proclined.

    Treatment Planning

    The treatment objectives inthis case were primarily to re-

    solve the lower crowding,achieve good overjet and over-bite, and avoid any further pro-clination of the upper and lowerincisors with their thin attachedgingivae. Further goals includedimproving the lower midline andresolving the Bolton discrepan-cy.

    There were three treatmentalternatives in this case. The firstwas to expand both arches to al-

    leviate the crowding and to bondveneers to the upper lateral in-cisors at the end of treatment toresolve the tooth-size discrepan-cy. The problem with this optionwas that the midlines could notbe centered.

    The second alternative wasto alleviate the lower crowdingby reproximation. The lower an-terior region was not suitable forstripping, however, due to the

    shape and small size of the lowerincisors. Reproximation of theposterior segment was not agood choice because of the ClassI posterior occlusion.

    The final alternative was toextract a lower incisor to allevi-

    ate the crowding. The upper mid-line could then be aligned withthe middle of the lower teeth.This plan would minimize pro-clination of the lower incisorsand would also address the ClassIII tendency and Bolton discrep-ancy. A diagnostic setup showedthat the treatment would indeedrelieve crowding and allow thecase to be finished with goodoverbite and overjet. The major

    drawback was that a lower in-cisor would have to be extracted.The lower right lateral incisorwas selected because it was themost misaligned and thus con-tributed most to the crowding,and because its attached gingivawas the least satisfactory of allthe lower incisors.

    Treatment Progress

    The patient was referred tohave the lower right lateral in-cisor extracted, and upper andlower polyvinyl siloxane impres-sions were taken for Invisalignappliances. A vacuum-formedretainer was made to hold the


    Fig. 2 Pretreatment computer images of both arches with lower rightlateral incisor extracted. Objects on facial surfaces of lower anteriorteeth represent composite attachments used to help resist tipping dur-ing space closure.

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    teeth in position until the align-ers were delivered. The patientsfinal tooth setup and stages oftooth movement were generated

    by the three-dimensional AlignTechnology software and re-viewed by the orthodontist on acomputer, using the proprietary

    ClinCheck system (Fig. 2).Prior to delivery of the first

    aligner, 1mm 3mm compositeattachments were bonded verti-

    Fig. 4 Schematic representation of planned maxillary tooth movements. Each column represents one tooth;each row represents an aligner stage.

    Fig. 3 Schematic representation of planned mandibular tooth movements. Each column represents one tooth;each row represents an aligner stage.

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    cally to the lower incisors andright cuspid to prevent tippingduring space closure. Lower-arch treatment was initiated withthe teeth adjacent to the extrac-tion site moving first (Fig. 3).Upper aligners were not used foreight weeks, until sufficientoverjet was achieved to enableincisor alignment (Fig. 4). Theteeth were programmed to un-dergo no more than .8mm net

    movement per stage.The patient was seen every

    four weeks for delivery of newaligners and monitoring of treat-ment progress and aligner fit(Fig. 5). Aligners were changedby the patient weekly at first, andlater at two-week intervals.Twelve stages were required inthe upper arch and 22 in thelower, with the last five mandib-ular aligners used in finishing to

    add mesial root tip of the lowerright cuspid.Total treatment time was

    11 months. The patient was thengiven Hawley-type upper andlower retainers to be worn atnight.

    Treatment Results

    Post-treatment facial pho-tographs showed little change infacial profile (Fig. 6). Althoughthe patient was protrusive beforetreatment, her profile was ac-ceptable to her, and there was noplan to change it. The Class Imolar and canine relationshipwas maintained, and the mandib-ular spaces were completely

    closed. The overjet was slightlyexcessive due to the thick mar-ginal ridges of the upper in-cisors; otherwise, good overjetand overbite were achieved de-spite the extraction of a lower in-cisor. The gingival recession inthe lower right central incisor re-gion increased during treatment.

    Both arches showed goodalignment, with the upper mid-line centered on the middle of

    the lower incisors. Comparisonof the post-treatment occlusalphotographs with the computerimages of their final stagedemonstrated the accuracy of theappliance in achieving the de-

    sired result (Fig. 7).The post-treatment pano-

    ramic x-ray revealed excessivedistal root tip of the lower rightcuspid and a slight mesial roottip of the lower right incisor,along with mild root resorptionof the lower right central incisor.The lateral cephalogram showedreduction of the overjet and in-creased proclination of the lowerincisors (Table 1). Because the

    pre- and post-treatment lateralcephs were taken on differentmachines, the tracings were notsuperimposed. Superimpositionof the occlusograms, however,revealed minor alignment withbuccal expansion of the upperright second bicuspid, a shift ofthe mandibular midline to theright, and buccal expansion inthe lower right second bicuspidregion (Fig. 8).

    Small interocclusal gapsbetween the first and second mo-lars could be attributed to exces-sive forces placed on the posteri-or occlusion during aligner wear.Such spaces are usually transient


    Pretreatment Post-Treatment Norm

    SNA 82 82 82SNB 77 78 80ANB 5 4 2MP-SN 42 39 33UI-NA 20 18 22UI-NA 8mm 7mm 4mmLI-NB 32 41 25

    LI-NB 11mm 12mm 4mmLI-MP 94 101 94

    Fig. 5 Patient after two months oftreatment. Note gingival reces-sion around lower right centralincisor and composite attach-ments on facial surfaces of ante-rior teeth.


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    Fig. 6 Patient after 11 months oftreatment.

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    in nature, but patients should bemade aware that bite settlingwith appliances such as Hawleyretainers, positioners, or up-and-down elastics may be requiredtoward the end of treatment. Inthis case, the patient was givenHawley instead of vacuum-formed retainers, and the pos-terior occlusion settled, as evi-denced by photographs takenone year after retention (Fig. 9).


    The Invisalign System re-quires polyvinyl siloxane im-pressions for longer shelf life,better accuracy, and multiplepours. Full-arch impressions are

    difficult to take with this materi-al, but are critical to the tech-nique.

    Invisalign treatment re-quires the clinician to plan outsequential movements for everytooth from beginning to endasomewhat different diagnosticprocess than with conventionalappliances. ClinCheck allowsthe clinician to evaluate the en-tire treatment carefully and criti-cally in all three planes of space.In the present case, the increasedproclination of the lower incisorswas overlooked by the orthodon-tist during the ClinCheck proce-dure. This proclination may haveexacerbated the gingival reces-sion in the lower incisor region.

    Tipping of the teeth into theextraction site may have been theresult of overly aggressive toothmovementas much as .38mmper week. That is more than thecurrent Align Technology rec-ommendation of .33mm perstage, with each aligner worn fortwo weeks.

    All in all, however, it ap-pears that lower incisor extrac-tion was an appropriate choice inthis case. The slight Class IIItendency, Bolton discrepancy,well-aligned upper arch, andcrowded lower arch all con-tributed to a good result.

    This was the first lower in-cisor extraction case treated withthe Invisalign System. The treat-

    Fig. 7 Comparison of final-stage computer images and post-treatmentintraoral photos.

    Fig. 8 Superimposition of pre- andpost-treatment occlusograms.


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    ment time was comparable tothat of fixed appliances, andtherefore offers evidence of a vi-able alternative to conventionaltechniques.

    ACKNOWLEDGMENTS: The authors

    would like to thank Amanda Ramirez for herhelp and Justin Tindall for his assistance withimaging.


    1. Owen, A.H. III: Single lower incisorextractions, J. Clin. Orthod. 27:153-160,1993.

    2. Sheridan, J.J.; LeDoux, W.; and McMinn,R.: Essix appliances: Minor tooth move-ment with divots and windows, J. Clin.Orthod. 28:659-663, 1994.

    Fig. 9 Patient one year post-retention.

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    Lower Incisor Extraction Treatment with the Invisalign System