10.59987/ads/2011.1-2.23-27
Aim. The aim of this study was to evaluate the changes in the transverse dimension and the perimeter of the maxillary arch produced by low friction self-ligating brackets TIME 3 compared to the Invisalign technique.
Materials and methods. Both the self-ligating sample and the Invisalign group were composed of 20 subjects, evaluated at the beginning (T0) and at the completion of therapy (T1). All subjects presented a Class I malocclusion with mild crowding in a permanent dentition, without craniofacial anomalies, missing teeth or a history of orthodontic treatment. Dento-alveolar measurements were made on the maxillary dental casts at T0 and T1. Significant differences between the treated groups were assessed with Independent Samples t test (p&lt;0.05).
Results. Statistically significant differences between self-ligating sample and Invisalign group were recorded for CWC, FPWF, FPWL, SPWF, SPWL, and AP measurements. No significant changes were found for CWL, MWF, MWL, and AD values. There was not a statistically significant difference between the treatment durations of the groups: 1.8 years for both patients. These data suggest that Invisalign treatment cannot be somewhat faster than fixed appliances. Moreover the final occlusion might not be as ideal.
Conclusions. The low fiction self-ligating system produced statistically significant different outcomes in the transverse dento-alveolar width and the perimeter of the maxillary arch during treatment when compared to Invisalign tecnique.
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Annali di stomatologia
Invisalign
Self-ligating versus Invisalign: analysis of dento-alveolar effects
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Original Article
2022-08-18
2022-08-18
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2023-12-04
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Ann Stomatol (Roma)
P. Cozza
2011
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Invisalign
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Self-ligating versus Invisalign: analysis of dento-alveolar effects
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                                                                                                                Original article



    Self-ligating versus Invisalign:
    analysis of dento-alveolar effects




                                                                                                            li
                                                                                                         na
    Chiara Pavoni, DDS                                            Introduction
    Roberta Lione, DDS
    Giuseppina Laganà, DDS, MS                                    The Invisalign system (Align Technology, Santa Clara, Ca,




                                                                                                      io
    Paola Cozza, MD, DDS, MS                                      USA) an estethic orthodontic treatment with removable, clear
                                                                  semielastic polyurethane aligners has become more often
                                                                  a common treatment choice since its first appearance in 1997.




                                                                              az
                                                                  This computer-aided modeling technique can fabricate nu-
    University of Rome “Tor Vergata”, Rome, Italy                 merous aligners to move teeth with relative precision to ob-
    Department of Orthodontics                                    tain a good occlusion. These aligners are made from a thin,
                                                                  transparent plastic that fits over the buccal, lingual/palatal and
                                                                  occlusal surfaces of the teeth. They conventionally are worn




                                                                            rn
                                                                  for a minimum of 20 hours per day and are changed se-
                                                                  quentially every two weeks. Invisalign has been indicated by
    Corresponding author:                                         its manufacturer to be used in adults and adolescents who
    Giuseppina Laganà                                             have fully erupted permanent dentitions (1,2).




                                                                  te
    Via G. Baglivi, 5-E                                           Align Technology provides guidelines for the types of mal-
    00161 Rome, Italy                                             occlusion that can be successfully treated with Invisalign.
    Mobile +39 335 5310894, fax +39 06 44232321                   Cases for which Invisalign is indicated include mild to mod-
    E-mail: giuseppinalagana@libero.it
                                                         In       erate crowding (1-6 mm), mild to moderate spacing (1-6
                                                                  mm), nonskeletal constricted arches, and relapse after fixed
                                                                  appliance therapy (3). The manufacturer claims that In-
                                                                  visalign can effectively perform the following orthodontic
    Summary
                                                                  movements: space closure, alignment after interproximal
                                                   ni
    Self-ligating versus Invisalign: analysis of dento-alveolar
                                                                  reduction, dental expansion, flaring, and distalization (4).
    effects.
                                                                  The Invisalign system has become a popular treatment
    Aim. The aim of this study was to evaluate the changes
                                                                  choice for clinicians because of the esthetics and comfort
                                       io


    in the transverse dimension and the perimeter of the          of the removable clear aligners compared with tradition-
    maxillary arch produced by low friction self-ligating         al appliances.
    brackets TIME 3 compared to the Invisalign technique.         One of the more commonly encountered types of patients
                             iz



    Materials and methods. Both the self-ligating sample          who request Invisalign treatment are those who have pre-
    and the Invisalign group were composed of 20 subjects,        viously received orthodontic treatment using fixed appli-
    evaluated at the beginning (T0) and at the completion of      ances and do not want fixed appliances for their present
                                                                  orthodontic treatment. Esthetic concerns during follow-
             Ed




    therapy (T1). All subjects presented a Class I malocclu-
    sion with mild crowding in a permanent dentition, with-       up orthodontic treatment may be a significant factor, with
    out craniofacial anomalies, missing teeth or a history of     many patients not wanting to show metal or partially clear
    orthodontic treatment. Dento-alveolar measurements            fixed appliances with arch wires when they smile. Anoth-
    were made on the maxillary dental casts at T0 and T1.         er group of patients who want Invisalign are teenagers who
    Significant differences between the treated groups were       wish to improve their esthetics, but are not interested in
    assessed with Independent Samples t test (p<0.05).            having the appearance of fixed appliances (5).
 IC




    Results. Statistically significant differences between        To this date, little clinical research has been published to
    self-ligating sample and Invisalign group were recorded       comprehensively study the effectiveness of Invisalign treat-
    for CWC, FPWF, FPWL, SPWF, SPWL, and AP measure-              ment (1-3). The lack of such objective information on this
    ments. No significant changes were found for CWL,             product has made it difficult for clinicians to objectively char-
    MWF, MWL, and AD values. There was not a statistically
C




                                                                  acterize the efficacy of Invisalign as compared to fixed ap-
    significant difference between the treatment durations
                                                                  pliances.
    of the groups: 1.8 years for both patients. These data
                                                                  In the last 20 years self-ligating brackets have undergone
    suggest that Invisalign treatment cannot be somewhat
    faster than fixed appliances. Moreover the final occlu-       a renaissance because the concept of self-ligation having
©




    sion might not be as ideal.                                   been pioneered in 1930s. Self-ligating brackets have a built-
    Conclusions. The low fiction self-ligating system pro-        mechanism to close off the edgewise slot, obviating the
    duced statistically significant different outcomes in the     need for elastomerics or steel ties to secure the archwire
    transverse dento-alveolar width and the perimeter of the      in the bracket slot. The chief advantages of self-ligating sys-
    maxillary arch during treatment when compared to In-          tem over conventional appliances are claimed to include
    visalign tecnique.                                            reduced friction, more robust ligation, more efficient tooth
                                                                  movement and sliding mechanics that can reduce treat-
    Key words: self-ligating, crowding, Invisalign.               ment time (6,7).

    Annali di Stomatologia 2011; II (1-2): 23-27                                                                                 23
    C. Pavoni et al.


    The aim of the present investigation was to compare the         •   first interpremolar width (lingual): distance between the
    dento-alveolar effects of the Invisalign system and of self-        most lingual point on the lingual surface of the maxil-
    ligating multibrackets treatment in particular relatively to        lary first premolars;
    transverse dimension, arch perimeter and arch depth on          •   first interpremolar width (fossa): distance between the
    maxillary jaw.                                                      central fossae on the occlusal surface of the maxillary
                                                                        first premolars;




                                                                                                            li
                                                                    •   second interpremolar width (lingual): distance between
    Subjects and methods                                                the most lingual point on the lingual surface of the max-




                                                                                                         na
                                                                        illary second premolars;
    A sample of 40 Caucasian subjects (19 males, 21 females)        •   second interpremolar width (fossa): distance between
    who sought for orthodontic treatment was selected con-              the central fossae on the occlusal surface of the max-
    secutively at the Department of Orthodontics “Tor Verga-            illary second premolars;




                                                                                                      io
    ta”, Dental school, University of Rome. The inclusion cri-      •   intermolar width (lingual): distance between the lingual
    teria for the enrollment in the study group were Class I mal-       fissure locations on the lingual surface of the maxillary
    occlusion, mild crowding in mandibular arch (mean crowd-            first molars;
    ing 4.4 ± 0.8 mm), permanent dentition, vertebral matu-         •   intermolar width (fossa): distance between the mesial




                                                                                az
    ration as assessed on lateral cephalograms more advanced            fossae on the occlusal surface of the maxillary first mo-
    than CS4 (postpubertal) (8) and no previous orthodontic             lars;
    treatment. All subjects were divided into two groups ac-        •   arch depth: distance from a point midway between the
    cording to the following treatment protocols:                       facial surfaces of the central incisors to a line tangent




                                                                              rn
    1. the self-ligating group comprised 20 subjects (9 female,         to the mesial surfaces of the first permanent molars;
         11 males) who were treated consecutively with self-        •   arch perimeter: sum of the segments between contact
         ligating brackets Time 3 at the Department of Ortho-           points from the mesial surface of the first permanent
         dontics of the University of Rome “Tor Vergata”;               molar to the mesial surface of the opposite first per-




                                                                    te
    2. the invisalign group included 20 subjects (12 female,            manent molar.
         8 males) who were treated consecutively with a series
         of invisible removable aligners at the Department of Or-
         thodontics, University of Rome “Tor Vergata”.              Statistical analysis
    These subjects were instructed to wear each aligner 22
                                                           In
    hours a day, 7 days a week for 2 to 3 weeks. All patients       All measurements were made by 1 operator (C.P.) and re-
    were asked to complete a daily compliance log during treat-     peated a month later. Casual and systematic errors were
    ment, recording the number of hours the aligners were worn      calculated comparing the first and the second measure-
    each day (9).                                                   ments with paired t-test and Dahlberg’s formula. Descriptive
                                              ni

    Success of the therapy at the end of the observation pe-        statistics were calculated for all maxillary dental cast meas-
    riod was not a determinant factor for selection of patients.    urements at T1 and T2, and for the T2-T1 changes. The
    Pretreatment records consisted of initial dental casts, or-     Independent Sample T tests were used to analyze statistical
                                    io


    thopantomography, and lateral cephalograms (T1); for each       differences between T1 and T2 values. The level of sig-
    patients the same records were taken immediately after          nificance was set at P<0.05
    treatment to avoid any relapse (T2).                            A control group is not required when investigating den-
                           iz



    The average age of the self-ligating group was 15 years         toalveolar changes during a short observation period as
    6 months at T1. The mean age of the invisalign group was        described in the present study (18 months). Transverse and
    18 years 4 months at T1. Mean duration of treatment was         sagittal arch changes in untreated subjects in the per-
            Ed




    18 months ± 3 months in the self-ligating group and 18          manent dentition at an average age of 15 years 6 months
    months ± 2 months in the invisalign group.                      are expected to be minimal.
    The treatments protocols comprised:
    1. preadjusted self ligating brackets Time 3 (AO Ameri-
         can Orthodontics Products), superelastic nickel titanium   Results
         archwires (.014-in followed by .016-in and .016x.022-
         in) of Form I – Force I (AO American Orthodontics),        No systematic error for any measures were found. Ran-
 IC




         and stainless steel archwire .017x.025-in (AO Amer-        dom error ranged from 0.2 to 0.4 mm. Descriptive statis-
         ican Orthodontics),                                        tics are reported in Tables.
    2. a series of nearly invisible appliances, Invisalign          In the self-ligating group intercanine width (cusp) showed
         (Align Technology, Santa Clara, Calif.), to incremen-      significant increase from T1 to T2: 3.15 mm. The first in-
C




         tally move the teeth from their crowded initial position   terpremolar widths (lingual and cusp) had significant in-
         to their final straightened position. The anterior teeth   creases of 3.40 mm and 2.45 mm, respectively, similar to
         were reduced at each interproximal location by means       the second interpremolar widths (lingual and cusp), with
         of diamond-coated finishing strips used for interprox-     significant increases of 2.50 mm and 2.15 mm, respectively
©




         imal reduction.                                            (Tab. 1).
    The following measurements were made on the maxillary           The invisalign group showed statistically significant increase
    dental casts at T1 and T2 (10):                                 in second interpremolar width at the fossa point (0.45 mm)
    • intercanine width (lingual): distance between the             and in intermolar widths at the fossa (0.50 mm) (Tab. 2).
         most lingual points on the lingual surface of the max-     Significant difference was found between the 2 groups for
         illary canines;                                            the intercanine widths, the change at the cusp was sig-
    • intercanine width (cusp): distance between the tips of        nificantly larger in the self-ligating group (2.65 mm) (Table
         the cusps of the maxillary canines;                        3).

    24                                                                                  Annali di Stomatologia 2011; II (1-2): 23-27
    Self-ligating versus Invisalign: analysis of dento-alveolar effects


    Table 1 - Descriptive statistics and comparison of maxillary measurements at T1 and T2 in self-ligating group.




                                                                                                               li
                                                                                                            na
                                                                                                         io
                                                                                  az
                                                                                rn
    Table 2 - Descriptive statistics and comparison of maxillary measurements at T1 and T2 in Invisalign group.




                                                                       te
                                                              In
                                                   ni
                                       io
                             iz
             Ed




    The comparison between two groups of the first inter-              thought that removable aligners cannot be this accurate.
    premolar measurements showed an improvement in the                 Fixed appliances produced better treatment outcomes than
    self-ligating subjects significantly bigger at the lingual point   Invisalign in orthodontist’s hands, given his level of ex-
    (2.30 mm), and at the cusp (3.35 mm), similar to the sec-          pertise. Particularly important to the outcome of In-
    ond interpremolar widths (lingual and cusp), with signifi-         visalign is proficiency in using Align Technology’s Clincheck
    cant increase of 1.85 mm and 2.05 mm, respectively.                program that allows the practitioner to accept or modify the
 IC




                                                                       treatment plan of tooth movements before the aligners are
                                                                       actually fabricated (11).
    Discussion                                                         Interestingly, there was not a statistically significant dif-
                                                                       ference between the treatment durations of the groups: 1.8
C




    There was not a statistically significant difference between       years for both patients. These data suggest that In-
    the ages of the Invisalign and braces groups. The mean             visalign treatment cannot be somewhat faster than fixed
    age in the Invisalign group was greater than that in the           appliances. Moreover the final occlusion might not be as
    braces group by almost 3 years. This discrepancy was ex-           ideal (12).
©




    pected because young adults are more likely to be inter-           Arch form development and posterior expansion of the den-
    ested in treatment with greater esthetics and comfort.             tal arches have been indicated as effects of low-friction me-
    However, tooth movement should be similar regardless of            chanics with self-ligating brackets during the initial phas-
    age with all other things being equal, such as periodon-           es of treatment with superelastic nickel-titanium .014-in
    tal condition and patient compliance.                              wires (13). Our findings showed statistically more signifi-
    Fixed appliances should have an advantage because of               cant increases in maxillary arch perimeter with low-friction
    the ability to make precise wire adjustments within 0.5 mm         brackets than invisalign during treatment. No differ-
    to intrude or extrude teeth as necessary; it has been              ences were found in maxillary arch depth between two

    Annali di Stomatologia 2011; II (1-2): 23-27                                                                                 25
    C. Pavoni et al.


    Table 3 - Descriptive statistics and comparison between two groups.




                                                                                                              li
                                                                                                           na
                                                                                                        io
                                                                                 az
                                                                               rn
                                                                      te
                                                             In
                                               ni

    groups. Statistically significant increases were found for all    maxillary arch perimeter (on average 3.5 mm), a clinical-
                                     io


    width measurements between the lateral and posterior              ly favorable result for nonextraction treatments.
    teeth, with the exception of the first molars measured lin-       The invisalign group showed not statistically significant
    gually only in braces group.                                      changes in intercanine widths (lingual and cusp), and in
                            iz



    Increases in arch width that used lingual points for meas-        the first interpremolar widths (lingual and cusp). The change
    urement were consistently smaller than the increases              in the second intermolar width at the lingual point was not
    recorded by using points located at cusps or occlusal fos-        statistically significant (0.30 mm).
            Ed




    sae.                                                              A significant change in intermolar widths at the fossa was
    The self-ligating system consent a significant increase in        found (0.50 mm), while the measurement at lingual point
    Intercanine widths (cusp) during treatment (3.15 mm),             was not significant (0.05 mm). The arch dept and arch
    whereas the measurements at the lingual point was not             perimeter had not a statistically significant T2-T1 increase
    statistically significant. The first interpremolar widths (lin-   (-0.05 mm and 0.00 mm).
    gual and cusp) had significant increases, while the               No significant differences were found between the 2 groups
    changes in intermolar width at the lingual point and at the       for the intercanine widths at lingual point (0.75 mm), where-
 IC




    fossa were not statistically significant (0.90 mm and 0.30        as the change at the cusp was significantly larger in the
    mm, respectively). The arch dept and arch perimeter had           self-ligating group (2.65 mm).
    not a statistically significant T2-T1 increase (1.30 mm and       The changes in arch dept and arch perimenter were not
    1.90 mm).                                                         significantly different from T1 to T2.
C




    This indicates that expansion of the maxillary arch in self-      In invisalign subjects there was not expansion in maxillary
    ligating group was achieved with a component of buccal            arch in all measurements considered.
    inclination of canines and posterior teeth (14).                  Interproximal reduction was performed as prescribed, but
    The greatest transverse increases were recorded at the            no other modifications were made to augment tooth
©




    level of the premolars and the canines, whereas smaller           movement (16). Therefore, the pass rate for Invisalign cas-
    increases were found at the level of the molars. A possi-         es might be higher if more sophisticated techniques, such
    ble reason for this differential effect might be the shape of     as auxiliaries, interarch elastics, or combination treatment
    the archwires used for alignment of the maxillary teeth (Tru-     with braces had been used. On the other hand, the braces
    Arch form); these have an accentuated width in the canine         patients were treated with tip-edge fixed appliances,
    first premolar region (15).                                       which can make fine adjustments with uprighting springs,
    The significant increases in the transverse widths of the         rotation springs, interarch elastics, and other auxiliaries in
    maxillary arch led to a statistically significant increase in     addition to the tooth movements made possible by the

    26                                                                                    Annali di Stomatologia 2011; II (1-2): 23-27
    Self-ligating versus Invisalign: analysis of dento-alveolar effects


    bracket prescription (17).                                             3.    Djeu G, Shelton C, Maganzini AL. Outcome assessment of
    However, there are several reasons that Invisalign might                     Invisalign and traditional orthodontic treatment compared with
    not be as effective as fixed appliances. Primary among                       the American Board of Orthodontics objective grading sys-
    them is compliance. Because the aligners are removable,                      tem. Am J Orthod Dentofacial Orthop 2005; 128(3):293–298.
                                                                           4.    McNamara JA, Brudon WL. Orthodontics and dentofacial or-
    the orthodontist must rely on the patient’s motivation and
                                                                                 thopedics. Ann Arbor (Mich): Needham Press; 2001.
    dependability to achieve the desired results. The remov-




                                                                                                                        li
                                                                           5.    Boyd RL. Esthetic Orthodontic Treatment Using the In-
    ability of Invisalign is an advantage to the patient but not                 visalign Appliance for Moderate to Complex Malocclusions.
    to the clinician. Another reason that Invisalign fails to com-




                                                                                                                     na
                                                                                 Journal of Dental Education 2008; 72(8): 948-67.
    pare with braces is that Invisalign minimally addresses the            6.    Harradine NW. Self-ligating brackets: where are we now? J
    occlusion (18). Boyd et al. (16) admitted that, when eval-                   Orthod;30:262-273. 2003
    uating the occlusal outcome of an Invisalign case, it was              7.    Fleming PS, DiBiase AT, Sarri G, Lee RT. Efficiency of
    evident that the same or an even better result could have                    mandibular arch alignment with 2 preadjusted edgewise ap-
                                                                                 pliances. Am J Orthod Dentofacial Orthop 2009; 135:597-602.




                                                                                                                  io
    been achieved with conventional braces in arguably less
                                                                                 Baccetti T, Franchi L, MaNamara JA jr. An improved version
    time.
                                                                                 of the cervical vertebral maturation (CVM) method for the as-
    Therefore, the major advantages of Invisalign over braces                    sessment of mandibular growth. Angle Orthod Aug
    are that the aligners are esthetic, removable, and com-




                                                                                         az
                                                                                 2002;72(4):316-23.
    fortable, but there are no biomechanical advantages.                   8.    Align Technology, Inc. The Invisalign reference guide. Santa
                                                                                 Clara, Calif; 2002
                                                                           9.    Franchi L, Baccetti T, Camporesi M, Lupoli M. Maxillary arch
    Conclusions                                                                  changes during levelling and aligning with fixed appliances




                                                                                       rn
                                                                                 and low-friction ligatures. Am J Orthod Dentofacial Orthop
    •    Self-ligating multibrackets treatment resulted effective                2006; 130:88-91.
                                                                           10.   Boyd RL, Vlaskalic V. Three-dimensional diagnosis and or-
         to solve mild crowding by increasing arch width and
                                                                                 thodontic treatment of complex malocclusions with the In-
         correcting buccolingual inclination, occlusal contacts                  visalign appliance. Semin Orthod 2001; 7:274–93.




                                                                           te
         and root angulations.                                             11.   Harradine NWT. Self-ligating brackets and treatment efficiency.
    •    Invisalign treatment has also had success with                          Clin Orthod Res 2001; 4:220-7.
         straightening arches by derotating teeth and by leveling          12.   Damon DH. The Damon low-friction bracket: a biologically com-
         arches.
    •    Invisalign can easily tip crowns but cannot tip roots be-
                                                                  In       13.
                                                                                 patible straight-wire system. J Clin Orthod 1998; 32:670-80.
                                                                                 BeGole EA, Fox DL, Sadowsky C. Analysis of change in arch
         cause of lack of control of tooth movement.                             form with premolar expansion. Am J Orthod Dentofacial Or-
    •    No statistically significant differences between the two                thop 1998; 113:307-15.
                                                                           14.   Thorstenson GA, Kusy RP. Effect of archwire size and material
         groups are evident when malocclusions start relatively
                                                                                 on the resistance to sliding of self-ligating brackets with sec-
                                                   ni
         well aligned roots.                                                     ondorder angulation in the dry state. Am J Orthod Dentofa-
                                                                                 cial Orthop 2002; 122:295-305.
                                                                           15.   Boyd RL, Miller RJ, Vlaskalic V. The Invisalign system in adult
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C
©




    Annali di Stomatologia 2011; II (1-2): 23-27                                                                                             27
