Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 01 Sept 2023

Predicted overbite and overjet changes with the Invisalign appliance: a validation study

,
, and
Page Range: 10 – 16
DOI: 10.2319/041323-269.1
Save
Download PDF

ABSTRACT

Objectives

To investigate whether the predicted changes in overbite (OB) and overjet (OJ) in Align Technology’s (Santa Jose, Calif) digital treatment plan for the prescribed course of treatment with the Invisalign appliance were consistent with those same changes in OB and OJ measured with the Geomagic Control X (Geomagic US, Research, Triangle Park, NC) metrology software system.

Materials and Methods

Geomagic Control X software was used to determine OB and OJ differences between the pretreatment and predicted outcome. STL files for patients satisfying inclusion criteria and undergoing nonextraction orthodontic treatment with the Invisalign appliance. The differences were compared, using the Bland-Altman analysis, to the corresponding data provided by Align Technology’s digital treatment-planning interface, ClinCheck.

Results

Data regarding 76 adult patients who satisfied strict inclusion criteria were assessed. The Shapiro-Wilks test indicated normality (P > .05). The Bland-Altman analysis showed high levels of agreement between the two measurements, with a bias range of −0.131 to 0.111 for OB and −0.393 to 0.03 for OJ recorded.

Conclusions

Clinicians and researchers can be confident that measurement data provided by Invisalign’s ClinCheck digital treatment-planning facility concerning OB and OJ changes from the initial to the predicted treatment outcome are valid.

Keywords: Clear aligner therapy; Invisalign; Metrology; Overbite; Overjet; Validation

INTRODUCTION

Clear aligner therapy (CAT) is commonly used to address malocclusion, with the Invisalign (Align Technology, San Jose, Calif) appliance being among the most frequently prescribed CAT appliances globally.1–4 One of the proposed advantages of CAT is the use of three-dimensional (3D) technology for treatment planning and the manufacture of aligners.5

Align Technology uses an online facility called ClinCheck that enables the orthodontist to modify tooth position and plan treatment procedures virtually, such as interproximal reduction, until an acceptable digital treatment plan (DTP) is finalized.5 An additional feature is the ability to view the predicted outcome from the finalized DTP. Also, Align Technology provides supplementary treatment information, including the initial and predicted overbite (OB) and overjet (OJ) measurement values, via the facility.

3D metrology is a commonly used tool to assess treatment changes associated with orthodontic therapy.6 Among the most commonly used metrology software systems is Geomagic Control X software (Geomagic US, Research, Triangle Park, NC). It has been used in several investigations to compare changes in malocclusion traits between the initial pretreatment occlusal state, the predicted occlusal outcome, and the actual treatment outcomes with the Invisalign appliance.7–12 In addition, it has been shown to be accurate in the measurement of linear tooth movements on digital scans and changes in some tooth movements associated with digital superimpositions and is considered to be a “gold standard” in metrology-associated research.13,14

Information regarding the accuracy of numerical treatment information provided by CAT provider DTP interface facilities is limited in the literature. Recent studies, however, have indicated that some values provided by Align Technology may be incorrect.15,16 A recent investigation, for example, established that Align’s mesiodistal tooth size measurements, and the Bolton analysis derived from it, was subject to systematic error and did not match two other gold standards.15 In addition, Smith et al.16 noted that the angular measurements supplied in the ClinCheck Tooth Movement Table were not consistently supported by independent metrological analysis. Relevant data, however, regarding OB and OJ measurements are lacking.

Knowledge in this regard can aid orthodontists in determining the accuracy of information provided by ClinCheck. It can also enable researchers to determine whether data provided by Align Technology regarding OB and OJ changes can be used in future relevant studies. If the pertinent information provided by Align Technology has been validated against accepted metrology software-derived values, researchers may be able to reduce the time-consuming and expensive metrological processes for some studies, and clinicians may feel more confident in basing treatment planning and case analysis upon this readily available data source.

The aim of the investigation, therefore, was to determine whether the predicted changes in OB and OJ in Align’s DTP for the prescribed course of treatment with the Invisalign appliance were consistent with those same changes in OB and OJ measured with the Geomagic metrology software system.

MATERIALS AND METHODS

Ethical approval was granted by the University of Adelaide for this retrospective study using de-identified data of orthodontic patients treated with the Invisalign appliance between 2014 and 2022. The digital models were from a database curated by a single practitioner (Dr. Weir) and comprise of a total of 12,000 patients treated with the Invisalign appliance by 14 experienced specialist orthodontists. All patients signed informed consent forms to indicate their consent to orthodontic treatment and for their data to be used for research purposes before treatment commenced.

The de-identified digital models of 76 patients to be used for evaluation of changes between the initial and predicted OB and OJ in the current study corresponded to the sample evaluated in a recent study investigating the predictability of anterior open bite treatment with Invisalign.17 Strict inclusion/exclusion criteria were applied for patient inclusion in the study.

Inclusion Criteria

  • Aged 18 years or older before commencing orthodontic treatment

  • Nonextraction orthodontic treatment with the Invisalign appliance only

  • Completion of an initial phase of dual-arch Invisalign therapy consisting of at least 14 aligners

  • Apparent open bite associated with one or more central incisors in the maxilla according to clinical images

  • Prescribed anterior open bite reduction in the ClinCheck DTP

  • Began treatment using SmartTrack aligner material no earlier than January 2014

  • Availability of the initial, predicted, and end of initial sequence of aligner digital models

Exclusion Criteria

  • Uncaptured teeth in the intraoral scanning process

  • Combined CAT/orthognathic surgery patients

  • Patients requiring restorative intervention during treatment

  • Medical conditions altering tooth movement or bone metabolism

Data regarding patient gender and age were recorded in a Microsoft (Redmond, Wash) Excel spreadsheet. Initial and predicted OB and OJ measurement values provided by the DTP in ClinCheck information tables were also documented. The corresponding Geomagic measurements were obtained by the creation of a horizontal reference plane via the palatal interproximal papilla between the upper first and second molars and the midpoint of the superior margin of the incisive papilla.7,17 This was used to align the .STL files of each patient at the initial and predicted time points (Figure 1). The initial and predicted digital models were aligned to this reference plane. Figure 2a shows the midpoint of the incisal edge of the upper left central incisor. Figure 2b indicates the vector determined by the midpoint of the incisal edges of the lower left central incisor and the lower left lateral incisor. The horizontal and vertical linear distance between the upper left central incisor midpoint and the vector midpoint were used to measure the OJ and the depth of OB (Figure 3) for the initial and predicted digital models. Intra- and interexaminer scores for the Geomagic measurements were excellent.17

Figure 1.Figure 1.Figure 1.
Figure 1. Horizontal reference plane showing the palatal interproximal papilla between the upper first and second molars and the midpoint of the superior margin of the incisive papilla.

Citation: The Angle Orthodontist 94, 1; 10.2319/041323-269.1

Figure 2.Figure 2.Figure 2.
Figure 2. (a) Midpoint of the upper left central incisor incisal edge as measurement point for overjet and overbite. (b) Lower arch point defined as the midpoint between the midpoints of the lower left central incisor and the lower left lateral incisor incisal edges for overjet and overbite measurements.

Citation: The Angle Orthodontist 94, 1; 10.2319/041323-269.1

Figure 3.Figure 3.Figure 3.
Figure 3. Linear measurement (in millimeters) of overjet (Y plane) and overbite (Z plane) between the midpoint of the upper left central incisor incisal edge and the midpoint of the vector between the lower left central incisor and the lower left lateral incisor.

Citation: The Angle Orthodontist 94, 1; 10.2319/041323-269.1

Statistical Analysis

Statistical analyses were computed via R (version 4.0; R Core Team, Vienna, Austria) and SPSS (version 25; IBM Corp, Armonk, NY) and were presented in tabular, graphic, and text formats. As points of reference and centers of rotation used by ClinCheck were not defined in a manner allowing reproduction with metrology software, direct comparisons at the initial (I) and predicted (P) time points were not possible. Therefore, the difference (I − P) for each method was compared. The Bland-Altman analysis was used to determine agreement between the differences of each method using the bland R package.18,19 The Shapiro-Wilks test was used to test for normality.

RESULTS

The data of 53 females and 23 males, with a mean age of 35.17 years at the start of treatment, were available for evaluation.

Table 1 outlines the summary statistics for the initial and predicted OB and OJ measurements evaluated via the Geomagic metrology software and the corresponding measurements provided by ClinCheck. The mean (SD) predicted OB measurement provided by Geomagic was 1.66 (0.81) mm compared with the mean (SD) predicted OB measurement provided by ClinCheck of 1.61 (0.92) mm.

Table 1. Initial and Predicted OB and OJ Measurementsa
Table 1.

The Bland-Altman plots of the changes in OB and OJ are displayed in Figures 4 and 5, respectively. The dashed lines represent the summary Bland-Altman statistical data, namely, (1) bias, (2) upper limit of agreement, and (3) lower limit of agreement. The dotted lines represent confidence intervals for the summary statistics, and the blue solid line represents a regression line measuring any proportional bias. If the regression slope is significantly different from zero, it may indicate proportional bias.

Figure 4.Figure 4.Figure 4.
Figure 4. Bland-Altman plot comparing the difference between Geomagic and ClinCheck initial and predicted overbite differences. CC indicates ClinCheck Geo, Geomagic; I, initial; LOA, level of agreement; OB, overbite; and P, predicted.

Citation: The Angle Orthodontist 94, 1; 10.2319/041323-269.1

Figure 5.Figure 5.Figure 5.
Figure 5. Bland-Altman plot comparing the difference between Geomagic and ClinCheck initial and predicted overjet differences. CC indicates ClinCheck Geo, Geomagic; I, initial; LOA, level of agreement; OB, overbite; and P, predicted.

Citation: The Angle Orthodontist 94, 1; 10.2319/041323-269.1

For OB, there was no proportional bias, and the sample bias was very close to zero, indicating the two methods were similar on average. Most of the points fell between the lower and upper limits of agreement or within their respective confidence bands.

For OJ, there may have been some proportional bias. However, the 95% confidence interval for the regression slope contained zero, indicating the slope was not significantly different from zero; therefore, there was no proportional bias. The sample bias was −0.181. However, the confidence interval contained zero; hence, no significant bias was present. Most of the points fell between the lower and upper limits of agreement or within their respective confidence bands.

Checking Assumptions

The validity of confidence intervals depended on the normality of the measure involved. This assumption was checked for the differences involved using normal quantile plots and a Shapiro-Wilks test (Figures 6 and 7). The OB plot and P value confirmed its normality, and although the OJ data showed some deviation from normal, the P value was >.05, indicating no serious problem with normality.

Figure 6.Figure 6.Figure 6.
Figure 6. Normal quantile plot of overbite measure difference.

Citation: The Angle Orthodontist 94, 1; 10.2319/041323-269.1

Figure 7.Figure 7.Figure 7.
Figure 7. Normal quantile plot of overjet measure difference.

Citation: The Angle Orthodontist 94, 1; 10.2319/041323-269.1

DISCUSSION

The global popularity of the Invisalign appliance and the widespread use of Geomagic metrology software in CAT studies highlighted the relevance of the present study. The findings indicated that the differences in the initial and predicted OB and OJ values provided by Invisalign’s ClinCheck software facility were consistent with the corresponding differences from the Geomagic metrology software.

A sample of patients with reduced OB or anterior open bite was chosen for the study presented here, as one of the proposed strengths of CAT over fixed appliance therapy is its effectiveness in deepening a reduced OB anteriorly.20 Exact agreement with the specific numbers involved was not sought in the present study, as it was uncertain how Align Technology measures OB and OJ. However, consistency in the changes of both traits between initial and predicted measurements via ClinCheck and Geomagic were accepted as validation of the numerical data provided by Align Technology. Since recent studies have indicated problems with some measurements provided by Align regarding mesiodistal tooth size measurements and mesiodistal tooth uprighting, it was encouraging that the present study indicated acceptability of the data regarding OB and OJ changes provided by ClinCheck.15,16

The findings suggested that the algorithms used by Align Technology for their OJ- and, particularly, OB-related data were similar to that observed via the methodology used with the Geomagic software in the present study. Further investigation and information from Align Technology, however, are required to confirm this. The data from this investigation, nevertheless, can provide orthodontists with reassurance regarding the accuracy of the numerical information related to OB and OJ changes provided by ClinCheck. It will also enable researchers to use these data in future studies, thus facilitating the reduction of time-consuming and expensive metrological processes in some investigations.

A limitation of the present study was that the findings may not be applicable to patients with an initial presentation of very deep OB. Also, the study did not validate additional numerical data provided in the ClinCheck facility. A strength of the investigation was the excellent intra- and interexaminer reliability in the Geomagic measurements. An additional strength was the use of the Bland-Altman analysis to compare the two methodologies for changes in OB and OJ measurements. The analysis provided a rigorous, visual, easy-to-interpret estimation of the agreement or reliability between two measurements of the same object and is superior to the use of correlation coefficients and t tests in this regard.21,22

Further investigation, however, is necessary to determine why two points fell outside the lower and upper limits of agreement for OB and three points fell outside the lower and upper limits of agreement for OJ. Future research is also required to determine the accuracy and validity of the additional numerical data provided by Align Technology’s ClinCheck facility and the numerical data by other companies’ DTP interface facilities.

CONCLUSIONS

  • The predicted changes in OB and OJ during treatment with the Invisalign appliance as reported by Align Technology are consistent with the changes in OB and OJ reported by direct measurement using the gold standard Geomagic metrology software system.

  • Clinicians and researchers can be confident that measurement data provided by Invisalign’s ClinCheck digital treatment-planning facility concerning OB and OJ changes from the initial to the predicted treatment outcome are valid.

  • Further research is required to determine the validity of additional numerical data provided by Invisalign’s ClinCheck facility and the numerical data provided by other CAT providers’ DTP interface facilities.

ACKNOWLEDGMENTS

The authors acknowledge the support provided by the Australian Society of Orthodontists Foundation for Research and Education and the University of Adelaide Kwok Paul Lee bequest. The funding bodies did not have any role in the study design, collection, analysis, interpretation, or writing of the manuscript.

REFERENCES

  • 1. 

    Meade MJ, Weir T. A survey of orthodontic clear aligner practices among orthodontists. Am J Orthod Dentofacial Orthop. 2022; 162: e302–e311.

  • 2. 

    Abu-Arqub S, Ahmida A, Da Cunha Godoy L, Kuo CL, Upadhyay M, Yadav S. Insight into clear aligner therapy protocols and preferences among members of the American Association of Orthodontists in the United States and Canada. Angle Orthod. 2023; 93: 417–426.

  • 3. 

    Meade MJ, Dreyer CW. A content analysis of orthodontic treatment information contained within the websites of general dental practices. J Consum Health Internet. 2022; 26: 396–409.

  • 4. 

    Arun M, Usman Q, Johal A. Orthodontic treatment modalities: a qualitative assessment of Internet information. J Orthod. 2017; 44: 82–89.

  • 5. 

    Meade MJ, Ng E, Weir T. Digital treatment planning and clear aligner therapy: a retrospective cohort study [published online ahead of print April 1, 2023]. J Orthod. doi:10.1177/14653125231166015

  • 6. 

    Weir T. The application of 3D metrology software in the quantitative and qualitative assessment of aligner treatment outcomes. Austral Orthod J. 2021; 37: 100–108.

  • 7. 

    Blundell HL, Weir T, Kerr B, Freer E. Predictability of overbite control with the Invisalign appliance. Am J Orthod Dentofacial Orthop. 2021; 160: 725–731.

  • 8. 

    Bowman E, Bowman P, Weir T, Dreyer C, Meade MJ. Occlusal contacts and treatment with the Invisalign® appliance: a retrospective analysis of predicted versus achieved outcomes. Angle Orthod. 2023; 93: 275–281.

  • 9. 

    Goh S, Dreyer C, Weir T. The predictability of the mandibular curve of Spee leveling with the Invisalign appliance. Am J Orthod Dentofacial Orthop. 2022; 162: 193–200.

  • 10. 

    Houle JP, Piedade L, Todescan R Jr, Pinheiro FH. The predictability of transverse changes with Invisalign. Angle Orthod. 2017; 87: 19–24.

  • 11. 

    Maree A, Kerr B, Weir T, Freer E. Clinical expression of programmed rotation and uprighting of bilateral winged maxillary central incisors with the Invisalign appliance: a retrospective study. Am J Orthod Dentofacial Orthop. 2022; 161: 74–83.

  • 12. 

    Bowman E, Bowman P, Weir T, Dreyer CW, Meade MJ. Evaluation of the predicted vs. achieved occlusal outcomes with the Invisalign® appliance: a retrospective investigation of adult patients. Int Orthod. 2023; 21: 100746.

  • 13. 

    Adel SM, Vaid NR, El-Harouni N, Kassem H, Zaher AR. Digital model superimpositions: are different software algorithms equally accurate in quantifying linear tooth movements? BMC Oral Health . 2022; 22: 1–2.

  • 14. 

    Adel SM, Vaid NR, El-Harouni N, Kassem H, Zaher AR. Tip, torque & rotations: how accurately do digital superimposition software packages quantify tooth movement? Prog Orthod . 2022; 23: 8.

  • 15. 

    Shailendran A, Weir T, Freer E, Kerr B. Accuracy and reliability of tooth widths and Bolton ratios measured by ClinCheck Pro. Am J Orthod Dentofacial Orthop. 2022; 161: 65–73.

  • 16. 

    Smith JM, Weir T, Kaang A, Farella M. Predictability of lower incisor tip using clear aligner therapy. Prog Orthod. 2022; 23: 37.

  • 17. 

    Blundell H, Weir T, Byrne G. Predictability of anterior open bite treatment with Invisalign®. Am J Orthod Dentofacial Orthop, In press. https://doi.org/10.1016/j.ajodo.2023.04.017

  • 18. 

    Bland JM, Altman D. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986; 327: 307–310.

  • 19. 

    Datta D. blandr: a Bland-Altman Method Comparison package for R. (Zenodo. https://doi.org/10.5281/zenodo.824514, https://github.com/deepankardatta/blandr, 2017). Accessed April 2, 2023.

  • 20. 

    Harris K, Ojima K, Dan C, et al. Evaluation of open bite closure using clear aligners: a retrospective study. Prog Orthod. 2020; 21: 1–9.

  • 21. 

    Donatelli RE, Lee SJ. How to report reliability in orthodontic research: Part 1. Am J Orthod Dentofacial Orthop. 2013; 144: 156–161.

  • 22. 

    Donatelli RE, Park JA, Alghamdi YM, Pandis N, Lee SJ. Assessment of reliability in orthodontic literature: a meta-epidemiological study. Angle Orthod. 2022; 92: 409–414.

Copyright: © 2024 by The EH Angle Education and Research Foundation, Inc.
Figure 1.
Figure 1.

Horizontal reference plane showing the palatal interproximal papilla between the upper first and second molars and the midpoint of the superior margin of the incisive papilla.

Figure 2.
Figure 2.

(a) Midpoint of the upper left central incisor incisal edge as measurement point for overjet and overbite. (b) Lower arch point defined as the midpoint between the midpoints of the lower left central incisor and the lower left lateral incisor incisal edges for overjet and overbite measurements.

Figure 3.
Figure 3.

Linear measurement (in millimeters) of overjet (Y plane) and overbite (Z plane) between the midpoint of the upper left central incisor incisal edge and the midpoint of the vector between the lower left central incisor and the lower left lateral incisor.

Figure 4.
Figure 4.

Bland-Altman plot comparing the difference between Geomagic and ClinCheck initial and predicted overbite differences. CC indicates ClinCheck Geo, Geomagic; I, initial; LOA, level of agreement; OB, overbite; and P, predicted.

Figure 5.
Figure 5.

Bland-Altman plot comparing the difference between Geomagic and ClinCheck initial and predicted overjet differences. CC indicates ClinCheck Geo, Geomagic; I, initial; LOA, level of agreement; OB, overbite; and P, predicted.

Figure 6.
Figure 6.

Normal quantile plot of overbite measure difference.

Figure 7.
Figure 7.

Normal quantile plot of overjet measure difference.

Contributor Notes

a Associate Professor, PR Begg Chair in Orthodontics, Adelaide Dental School, University of Adelaide, Adelaide, Australia.
b Associate Professor, La Trobe Rural Health School, La Trobe University, Bendigo, Victoria, Australia.
c Honorary Clinical Senior Lecturer, Orthodontic Unit, Adelaide Dental School, The University of Adelaide, Adelaide, Australia.
Corresponding author: Dr Maurice J. Meade, Associate Professor and PR Begg Chair in Orthodontics Orthodontic Unit, Adelaide Dental School, Level 10, Adelaide Health and Medical Sciences Building Corner of North Terrace and, George St, Adelaide SA 5000, Australia (e-mail: maurice.meade@adelaide.edu.au)
Received: 01 Apr 2023
Accepted: 01 Jul 2023
  • Download PDF