Predictability of orthodontic tooth movement with aligners: effect of treatment design

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Abstract

Backgrounds

The present study was designed to define: (1) which are the less predictable OTM with Invisalign aligners when the treatment plan is designed by expert operators, (2) if the presence and shape of attachments influence the predictability of OTM and (3) if patients’ demographics influence OTM predictability. The sample comprises 79 prospectively recruited patients (mean age 30.8 years; SD 12.0; 23 M, 56 F), treated by expert operators with an average of 27 aligners (SD 15) in the maxillary arch and 25 aligners (SD 11) in the mandibular arch. Post-treatment digital models and final virtual treatment plan models were exported from ClinCheck ^® software as STL files and subsequently imported into Geomagic Qualify ^®software, to compare final teeth positions. The differences were calculated and tested for statistical significance for each tooth in the mesial–distal, vestibular–lingual and occlusal–gingival directions, as well as for angulation, inclination and rotation. In addition, the statistical significance of categorical variables was tested.

Results

The lack of correction was significant for all movements and in all group of teeth ( P < 0.01) except for the rotation of maxillary first molar. The prescribed OTM, the group of teeth and movement, the frequency of aligner change and the use of attachment influence the outcome. The greatest discrepancies in predicted and achieved tooth position were found for angular movements and rotation of teeth characterized by round-shaped crowns, for a ratio of approximately 0.4° per 1° prescribed. Optimized attachments for upper canines and lower premolar rotation seem not working properly. Second molar movements are mostly unexpressed. Furthermore, changing the aligner every 14 days will reduce the lack of correction of the 12% with respect to 7 days aligner change.

Conclusions

Predictability of orthodontic movement with aligners still has limitations related to the biomechanics of the system: the shape of some attachments and the characteristics of aligner material need to be redefined. However, the results of this study allow to properly design the virtual treatment plan, revealing how much overcorrection is needed and which attachments are most effective.

Related collections

Most cited references 47

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Efficacy of clear aligners in controlling orthodontic tooth movement: a systematic review.

Gabriele Rossini, Simone Parrini, Tommaso Castroflorio … (2015)

To assess the scientific evidence related to the efficacy of clear aligner treatment (CAT) in controlling orthodontic tooth movement.

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How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign.

Neal Kravitz, Budi Kusnoto, Ellen A. BeGole … (2009)

The purpose of this prospective clinical study was to evaluate the efficacy of tooth movement with removable polyurethane aligners (Invisalign, Align Technology, Santa Clara, Calif). The study sample included 37 patients treated with Anterior Invisalign. Four hundred one anterior teeth (198 maxillary and 203 mandibular) were measured on the virtual Treat models. The virtual model of the predicted tooth position was superimposed over the virtual model of the achieved tooth position, created from the posttreatment impression, and the 2 models were superimposed over their stationary posterior teeth by using ToothMeasure, Invisalign's proprietary superimposition software. The amount of tooth movement predicted was compared with the amount achieved after treatment. The types of movements studied were expansion, constriction, intrusion, extrusion, mesiodistal tip, labiolingual tip, and rotation. The mean accuracy of tooth movement with Invisalign was 41%. The most accurate movement was lingual constriction (47.1%), and the least accurate movement was extrusion (29.6%)- specifically, extrusion of the maxillary (18.3%) and mandibular (24.5%) central incisors, followed by mesiodistal tipping of the mandibular canines (26.9%). The accuracy of canine rotation was significantly lower than that of all other teeth, with the exception of the maxillary lateral incisors. At rotational movements greater than 15 degrees, the accuracy of rotation for the maxillary canines fell significantly. Lingual crown tip was significantly more accurate than labial crown tip, particularly for the maxillary incisors. There was no statistical difference in accuracy between maxillary and mandibular teeth of the same tooth type for any movements studied. We still have much to learn regarding the biomechanics and efficacy of the Invisalign system. A better understanding of Invisalign's ability to move teeth might help the clinician select suitable patients for treatment, guide the proper sequencing of movement, and reduce the need for case refinement.

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The use of percentage change from baseline as an outcome in a controlled trial is statistically inefficient: a simulation study

Andrew Vickers (2001)

Background Many randomized trials involve measuring a continuous outcome - such as pain, body weight or blood pressure - at baseline and after treatment. In this paper, I compare four possibilities for how such trials can be analyzed: post-treatment; change between baseline and post-treatment; percentage change between baseline and post-treatment and analysis of covariance (ANCOVA) with baseline score as a covariate. The statistical power of each method was determined for a hypothetical randomized trial under a range of correlations between baseline and post-treatment scores. Results ANCOVA has the highest statistical power. Change from baseline has acceptable power when correlation between baseline and post-treatment scores is high;when correlation is low, analyzing only post-treatment scores has reasonable power. Percentage change from baseline has the lowest statistical power and was highly sensitive to changes in variance. Theoretical considerations suggest that percentage change from baseline will also fail to protect from bias in the case of baseline imbalance and will lead to an excess of trials with non-normally distributed outcome data. Conclusions Percentage change from baseline should not be used in statistical analysis. Trialists wishing to report this statistic should use another method, such as ANCOVA, and convert the results to a percentage change by using mean baseline scores.

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Author and article information

Contributors

Tommaso Castroflorio: tommaso.castroflorio@unito.it

Ambra Sedran:

ORCID: http://orcid.org/0000-0003-3269-3510

ambra.sedran@gmail.com

Matteo Reverdito: matteo@reverdito.com

Sabrina Mutinelli: sabrinamutinelli109@gmail.com

Simonas Grybauskas: simonas.grybauskas@gmail.com

Mantas Vaitiekūnas: m.vaitiekunas90@gmail.com

Andrea Deregibus: andrea.deregibus@unito.it

Journal

Journal ID (nlm-ta): Prog Orthod

Journal ID (iso-abbrev): Prog Orthod

Title: Progress in Orthodontics

Publisher: Springer Berlin Heidelberg (Berlin/Heidelberg )

ISSN (Print): 1723-7785

ISSN (Electronic): 2196-1042

Publication date (Electronic): 16 January 2023

Publication date PMC-release: 16 January 2023

Publication date Collection: 2023

Volume: 24

Electronic Location Identifier: 2

Affiliations

[1 ]GRID grid.7605.4, ISNI 0000 0001 2336 6580, Department of Surgical Sciences, , Dental School of the University of Torino, ; Via Nizza 230, 10126 Turin, Italy

[2 ]Poggibonsi, Italy

[3 ]Turin, Italy

[4 ]Cuneo, Italy

[5 ]Caserta, Italy

[6 ]GRID grid.5608.b, ISNI 0000 0004 1757 3470, Department of Neuroscience, School of Dentistry, Section of Pedodontics, , University of Padova, ; Via VII Febbraio 2, 35122 Padua, Italy

[7 ]University of Ferrara, Vilnius, Lithuania

[8 ]GRID grid.6901.e, ISNI 0000 0001 1091 4533, Kaunas University of Technology, ; Kaunas, Lithuania

Author information

Ambra Sedran http://orcid.org/0000-0003-3269-3510

Article

Publisher ID: 453

DOI: 10.1186/s40510-022-00453-0

PMC ID: 9840984

PubMed ID: 36642743

SO-VID: 3d9a69cb-c9cb-47e7-ab9c-08f8d54eaa78

License:

Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

History

Date received : 17 November 2022

Date accepted : 17 December 2022

Funding

Funded by: FundRef http://dx.doi.org/10.13039/501100006692, Università degli Studi di Torino;

Award ID: CAST_RIC_COMP_18_01

Award Recipient : Tommaso Castroflorio

Custom metadata

Keywords: clear aligners,orthodontic tooth movement,attachments,treatment design

Data availability:

Keywords: clear aligners, orthodontic tooth movement, attachments, treatment design