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Dr Haylea Blundell, Tony Weir,
Brett Kerr & Elissa FreerDiscipline of Orthodontics,
University of Queensland
THE UNIVERSITY
OF QUEENSLAND
AUSTRALIA
INTRODUCTIONCorrecting the vertical dimension in orthodontics
is challenging.1,2
Clear aligner therapy is becoming increasingly
demanding by patients, however there is currently
insufficient evidence to support the efficacy of
clear aligners to correct a deep overbite.
ClinCheck® software (Align Technology®) is used
by clinicians to treatment plan Invisalign® cases.3
The predicted outcomes of Invisalign® treatment
using ClinCheck® have been questioned due to
uncertainty of accuracy when compared with
actual post-treatment outcomes. 3-7
Since the introduction of Invisalign® in 1998, there
has been limited and conflicting evidence in the
literature regarding the efficiency of this appliance
in deep overbite correction. 8-11 Therefore, the aim
of this study was to investigate and determine the
accuracy of Invisalign® in correcting deep overbite
by comparing the predicted outcome from
ClinCheck® to the actual post-treatment outcome.
The null hypothesis states there is no difference
in overbite when comparing ClinCheck® and
achieved post-treatment overbite
SUBJECTS &
METHODOLOGYA retrospective study involving 42 adult (>18years old)
patients with pre-treatment and post-treatment intra-oral scans
using an iTero Element scanner treated with Invisalign® by Dr
Tony Weir at his private orthodontic practice in Brisbane,
between January 2013 - July 2018.
Additional inclusion criteria included compliant patients, the
presence of second maxillary molars, dual arch Invisalign
treatment, patients treated with a minimum of 14 aligners,
non-extraction treatment plan with an overbite depth up to
8mm. Patients treated with IPR, anterior build-ups,
orthognathic surgery treated, or in combination with auxiliaries
such as vertical elastics, anterior bite ramps, cross elastics or
fixed appliances were excluded from the study.
A pilot study was performed to determine the sample size.
Pre-treatment, predicted (ClinCheck®) and actual post-
treatment overbite for each patient were imported into
Geomagic® Control X software (Version 2017.0.3.69;
Geomagic, Morissville, NC, USA) and compared.
The models were aligned to a horizontal reference adjusted
from Grunheid et al7 (Fig. 1) using the interproximal papillae
instead of the occlusal surfaces. Overbite depth was
measured from the mid point of the 21 incisal edge (Fig. 2) to
the mid point of a vector from the 31 and 32 incisal edges
(Fig. 3). Intra-operator error was measured using 20 randomly
selected patients at two intervals, two weeks apart. Inter-
operator error was measured on 10 patients by an operator
with experience with Geomagic® Control X.
Figure 1 Reference points for the horizontal
reference plane adapted from Grunheid et al (2017)
Figure 2 Models aligned to the horizontal reference
line with the mid-point of 21 incisal edge and the
vector between 21-32.
Figure 3 Linear measurement of overbite between
the incisal edge of the 21 and the vector between
31-32
RESULTS
• Intra- and inter-operator error for overbite measurement showed excellent agreement (> 0.997).
• In 40/42 cases, ClinCheck over-predicted the post-treatment reduction in overbite (Fig. 4)
• 50% of the sample groups overbite was >4.0mm pre-treatment and 30% of patients post-treatment still
had an increased overbite >4.0mm post-treatment. (Table 1)
• Overall, only 39.2% of the prescribed overbite reduction was achieved using the Invisalign ® appliance
Table I. Frequency and percentage of overbite
Overbite Depth
Overbite Mean Normal Moderate Deep
± SD 0 to 2mm 2 to 4mm >4mm
mm n(%) n(%) n(%)
Pre-treatment overbite 3.9 ± 1.4 5 (12) 17 (38) 21 (50)
Post-treatment overbite 3.3 ± 1.3 7 (17) 23 (55) 12 (30)
Predicted (ClinCheck) overbite 1.9 ± 0.7 25 (60) 17 (40) -
0
1
2
3
4
5
6
7
1.6
8
1.8
1.8
1.8
6
1.8
7
2.2
2
2.3
5
2.3
7
2.5
1
2.7
2.7
2.8
5
2.8
6
2.9
3.1
7
3.2
9
3.4
2
3.6
3
3.7
2
3.8
3
3.9
4.0
8
4.1
4.4
4.4
3
4.5
3
4.5
4
4.6
4.6
4.6
6
4.7
4
4.8
2
4.9
5
5.0
6
5.1
7
5.3
3
5.3
3
5.6
4
5.7
1
6.1
3
6.2
3
7.7
2
Ove
rbit
e (
mm
)
Pre-treatment overbite (mm)
ClinCheck predicted overbite Post-trearment overbite
Figure 4 Difference between predicted (ClinCheck) and post-treatment overbite
RESULTS
Table II. Estimate post-treatment overbite with Invisalign® treatment (95%CI)
ClinCheck (mm)
0 1 2 3
Init
ial O
verb
ite
(m
m)
4 2.9 3.2 3.4 3.6
(2.0, 3.8) (2.7, 3.6) (3.1, 3.7) (3.1, 4.2)
5 3.5 3.8 4 4.2
(2.5, 4.5) (3.1, 4.4) (3.7, 4.3) (3.7, 4.7)
6 4.1 4.3 4.6 4.8
( 3.0, 5.3) ( 3.6, 5.2) (4.1, 5.1) ( 4.3, 5.4)
7 4.7 5.0 5.2 5.5
(3.4, 6.1) (4.0, 6.0) (4.5, 5.9) (4.8, 6.1)
• Table II highlights the greater overbite correction (mm) required, the larger the discrepancy between the
predicted (ClinCheck ®) and the achieved overbite post-treatment.
• The regression coefficient analysis shows that on average, only 30.5% of overbite reduction will be
achieved when reducing an initial 4.0 – 7.0mm overbite to 0mm. (Table II)
DISCUSSION
In the present study all patients had a prescribed reduction (ClinCheck®) in overbite to less than
4.0mm. However, clinically 30% of patients still had a deep overbite (>4.0mm) post-treatment,
highlighting the shortfall of overbite reduction using the Invisalign® appliance, where ClinCheck®
over-predicted overbite reduction in 95.3% of the patients in the sample.
Two patients produced greater overbite correction than prescribed on ClinCheck®. The reason
for this was not investigated within this study, however this could be due to individual biological
response to orthodontic tooth movement. It is also important to note that as these two outliers
were included in the overall data, therefore the overall accuracy of achieved overbite using the
Invisalign appliance® has been affected in the current sample of patients.
Overall, the data showed a general, positive linear trend between prescribed overbite reduction
and the actual post-treatment overbite depth. Using the linear regression analysis we were able
to predict overbite reduction depending on the initial pre-treatment overbite depth (Table II).
Reducing a pre-treatment overbite of 7mm to 0mm on ClinCheck® as estimated, would produce
a post-treatment overbite of 4.7mm, where only 32.9% of the prescribed overbite reduction is
achieved. From the available data, the overall clinical expression of overbite reduction using the
Invisalign® appliance is 39.2%. This finding is considerably lower than previously published
articles by Drake et al12 (72%), Chisari et al13 (57%) and Brenner14 (51.9%) although similar to
the results presented by Kravitz et al15 (41%).
It is worth noting that the use of bite ramps and intermaxillary elastics were exclusion criteria,
and these may assist aligners in achieving improved overbite correction. Equally, the exclusion
of cases which had extractions, interproximal reduction or space closure eliminated the role of
relative extrusion which could further challenge overbite correction outcomes.
The authors acknowledge the flaws in any retrospective study, where there is an inherent risk of
selection bias.
Further investigations to determine the reasons for the inability of aligners to correct overbites
to the prescribed amount should be carried out. An investigation into the role of arch
depth/incisor flaring in determining final overbite in the current sample is presented in a
separate poster.
CONCLUSIONS
AcknowledgementsThis project wouldn’t have been possible without the support
from the University of Queensland and the ASO-FRE.
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1. On average, the Invisalign appliance expressed 39.2% of the
programmed overbite reduction when compared to the prescribed
outcome in the ClinCheck Software.
1. The deeper the overbite is pre-treatment, the more challenging it may
be to express the overbite reduction with Invisalign aligners alone
2. ClinCheck overestimated bite opening in 95.3% of cases. Therefore,
programmed movement in ClinCheck software may not be a clinically
useful determinant of the expression of overbite reduction