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Bonding accuracy of a novel lingual customized orthodontic appliance (INBRACE™): an in-vivo study

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Bonding accuracy of a novel lingual customized orthodontic appliance (INBRACE™): an in-vivo study

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Bonding Accuracy of A Novel Lingual
Customized Orthodontic Appliance
(INBRACE
TM
) :
An In-Vivo Study

By Zoey Gutierrez DDS

A Thesis Presented to the
Faculty of the USC Herman Ostrow School of Dentistry
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
Master of Science

Craniofacial Biology

May 2020

2
Acknowledgements
This research project would not have come to life without the mentorship and enthusiasm
from Dr. Andre Weissheimer. He came up with new ideas and took the time to guide me through
the process. He is a true role model as a clinician and educator. Kaifeng Yin was incredibly
helpful for running and re-running my statistics and giving helpful feedback on my overall
thesis. Katie Marsh was so kind as to be the second measurer of all the data in the study. She
measured every bracket position at two separate time points to make sure that the intra-reader
and inter-reader reliability was high in the study.

3

Table of Contents

1. Abstract 4
2. Introduction 6
3. Materials and Methods 12
a. Sample 12
b. Protocols 12
c. Superimposition 20
d. Statistical Analysis 20
4. Results 22
5. Discussion 24
6. Conclusions 28
7. References 30
8. List of Tables 33
9. List of Figures 43

4
ABSTRACT
Introduction: With digital technology workflow, orthodontic appliances can be digitally
designed and customized with computer-aided design and manufacturing. Following the digital
design and manufacturing of the brackets is an indirect bonding procedure to transfer the
brackets onto the dentition. It is important to know how accurate the indirect bonding procedure
is for any orthodontic appliance used clinically. The purpose of this study was to assess the
accuracy of an indirect bonding technique for INBRACE system, a computed-aid designed
customized appliance.
Material & Methods: In this retrospective study, the sample comprised of 12 individuals from
the USC Orthodontics clinic who had mild to moderate crowding and were undergoing
orthodontic treatment using the INBRACE appliance with brackets prescribed on the maxillary
and mandibular arches from molar to molar. Initial scans from each patient were saved as STL
files and used to virtually place brackets and fabricate custom CAD/CAM lingual appliances
through INBRACE. The brackets were indirectly bonded to the patient following the protocol
provided by INBRACE. Post-bonding scans were obtained clinically and again saved as STL
files. The initial scans containing the virtual bracket models (VBM) and the post-bonding models
(PBM) were 3D superimposed. Paired T-test was used to detect the potential difference in
bonding accuracy. One-Way ANOVA was used to determine if there was a difference in bonding
accuracy between the teeth divided into the same segments used clinically in the indirect bonding
trays, and between the teeth within each segment.
Results: Bracket positions between the VBM and the PBM showed a statistically significant
difference in bonding positions when comparing all the teeth in the sample (P < 0.001).
However, these differences are not clinically significant. The Root Mean Square (RMS) mean
5
error in bonding between all the teeth in the sample was 0.332mm. One-way ANOVA analysis
showed statistically significant differences in the bracket positioning between the 6 segmented
Indirect bonding (IDB) trays (P < 0.0001), with the lower posterior segments showing most
bonding errors. However, within each segment, the bonding errors did not differ significantly
between teeth (P > 0.05).
Conclusion: This study showed the INBRACE system had a good bonding accuracy (average
error 0.33mm) which is considered clinically accurate and acceptable for a customized lingual
appliance. The bonding accuracy was better for the anterior segments, in both maxillary and
mandibular arches, when compared to the posterior segments. Lastly, there was no difference in
the bonding accuracy for individual teeth within each IDB tray.

6
INTRODUCTION

Orthodontists have been bonding orthodontic appliances for many years. It is well known
that bracket positioning is one of the key factors for a successful and predictable treatment
outcome. According to Kim et al., accurate bracket positioning has a very strong influence on the
final result and length of orthodontic treatment (Kim et al., 2017). Treatment success relies on
correct bracket positioning during bonding, which will simplify the stages of orthodontic tooth
movement, and increase the predictability of results (Nojima et al., 2015). Many factors effect an
ideal bracket position on a tooth including; tooth shape and malformation and material of transfer
tray, along with others. In the straight wire appliance, inaccuracy of bracket positioning can
cause deviations in rotation, extrusion and intrusion, deviations in buccal and lingual position of
the teeth, unwanted tipping, and incorrect torque (Shpack, 2007).

In recent years, the demand for esthetic orthodontic treatment has increased dramatically,
especially in the adult population. Adults are seeking more convenient, truly esthetic orthodontic
solutions to improve their smiles without compromising their busy lifestyles. A recent study has
shown that adults seeking orthodontic care make decisions based on appearance and most often
prefer “invisible” treatment. While traditional braces are effective, they are unattractive and
require frequent office visits (Chambers, et. al.) Traditional lingual braces are the most esthetic
but are hard to use, expensive, and available from only a small number of doctors. Clear aligners,
although not invisible, are considered esthetic solutions. While the range of their clinical
application has expanded, clear aligners still depend heavily on patient compliance to ensure
results. Direct-To-Consumer (DTC) aligners are now on the market, attracting patients who want
7
low cost, more invisible, and more convenient treatment. The new INBRACE
®
system with
Smartwire
®
technology is based on the fundamental principles of orthodontics and incorporates
the latest advancements in indirect bonding, self-ligation, and computer-aided design and
computer-aided manufacturing (CAD/CAM) technology. The esthetic lingual orthodontics was
reimagined to improve ease of use and treatment efficacy and create a fully customized and
automated appliance that all orthodontists could use. It represents the new generation of esthetic
orthodontic treatment and it uses indirect bonding to place brackets that were digitally
positioned.

Bonding of brackets to the patient’s dentition is accomplished through either a direct or
indirect method. Direct bonding brackets involves positioning brackets directly onto the patient’s
dentition, without transferring them from a pre-planned position. In lingual orthodontics, direct
bonding of lingual brackets has been shown to be imprecise and may lead to problems due to the
anatomic variations in lingual tooth surfaces (Beyling et a., 2013). Thus, indirect bonding
techniques for lingual customized appliances is required. Indirect bonding is a technique where
brackets are transferred from dental casts or digital working models and bonded clinically onto
the patient’s teeth using a transfer device (Aksakalli, 2012). This transfer devices can be made
from different materials and are called indirect bonding trays (Mezomo, et. al.). Indirect bonding
was first developed in a laboratory process and was reported that the silicon based tray provided
better precision for bracket positioning when compared to a vacuum formed tray (Kim et al.,
2018). The indirect bonding process was first described in detail in 1972 by Silverman and
Cohen, who used cements for bonding brackets onto working models and prepared a
thermoplastic tray for transfer of the brackets to the dentition (Aksakalli, 2012). By the 1990’s,
8
light cured adhesives were introduced in the indirect bonding process, and it is still what we used
today (Aksakalli, 2012). Most recently, computer-aided design and computer-aided
manufacturing (CAD/CAM) has been used for indirect bonding procedures (Kim et al., 2018).
The CAD/CAM process for indirect bonding includes designing a virtual 3D model in a
CAD/CAM program to produce a transfer jig to be used clinically to bond the brackets to the
teeth (Kim et al., 2018). Currently, indirect bonding is the preferred technique when placing a
complete fixed appliance (Proffit 332). When visibility is poor, direct bonding becomes more
difficult and there is a greater need for indirect bonding (Proffitt 332). Because of this, indirect
bonding is necessary when bonding lingual appliances (Proffitt 332).

There are many advantages of indirect bonding technique. Among them, is the reduced
chair time and decreased unwanted premature occlusal contacts when optimum accuracy is
achieved with the technique (Aksakalli, 2012). Thus, risks of TMD, root resorption, and
elongation of treatment may be decreased with the use of indirect bonding by enabling the
clinician to bond the brackets at their ideal position on the tooth. Another advantage of indirect
bonding is that it is more cost effective since much of the work can be delegated to the staff as
compared to direct bonding, so doctor time may be better utilized. Indirect bonding stands out
for allowing better 3D visualization of tooth positioning which results in greater accuracy while
positioning brackets since the procedure is carried out in the laboratory (or digitally), followed
by transferring to the patient’s mouth through use of custom-fabricated trays (Nojima, 2015).

There are also disadvantages to indirect bonding compared to direct bonding. Indirect
bonding requires increased lab time, and greater staff education in bracket placement and
9
fabrication of transfer jigs (Aksakalli, 2012). Another disadvantage is that bonding a case
indirectly requires a second appointment for the patient to come in on a separate day than the
records are taken (Aksakalli, 2012). Other disadvantages include the errors in bracket positioning
caused by transfer of the brackets from the transfer trays to the patient’s dentition caused by
contamination of saliva or other interferences by the patient’s cheek or tongue. There are also
potential errors that may occur which are caused by tray fabrication or chair-side clinical
technique used in bonding. However, once a proper indirect bonding technique is obtained, these
disadvantages such as time-consuming laboratory procedures and additional material costs are
overcome by previously stated benefits (Nojima, 2015).

Many studies have been conducted to test the accuracy of indirect bonding compared to
direct bonding. In one study, Koo et al. concluded that bracket height when placed with indirect
bonding was closer to ideal than when placed with direct bonding, while there was no
statistically significant difference between the two techniques with regard to mesiodistal position
and angulation (Koo et al., 1999). In another study, Shpack et al. concluded that indirect bonding
was significantly (twofold) more accurate than direct bonding in labial orthodontics and
threefold more accurate than direct bonding in lingual orthodontics (Shpack et al, 2007).
With lingual appliances, there is limited visibility and access, greater variation in lingual
tooth surface morphology, clinical crown height is shorter than the labial clinical crown height,
there is a wide range of labio-lingual crown thickness, there are sloped lingual surfaces, smaller
interbracket distance, and tongue interferences (Shpack et al., 2007). These factors can all lead to
inaccurate bracket placement without indirect bonding.
10
The major advantage in a customized design and fabrication for an orthodontic appliance
is the unlimited individuality of the appliance (Wiechmann et al., 2003). There are three different
ways to customize orthodontic appliances. These include a customization of the individualized
archwire, customization of the bracket slot/ bracket base, or a combination of a customized
archwire and customized bracket (Grauer et al., 2012). Customization of the orthodontic
appliance allows the orthodontist to utilize the desired treatment outcome to fabricate the
appliance (Grauer et al., 2012). Bracket position accuracy is especially important in customized
appliances, where the bracket and/or wires are specifically fabricated to fit an exact location on
each individual patient’s tooth surface. If an error in the indirect transfer of the brackets, the
effectiveness of the customized appliance will be reduced since the brackets won’t be placed
where they were fabricated to be.

Customized lingual appliances, such as the insignia system, uses a customized slot that is
fabricated into the bracket at the desired position in order to produce the desired movement
(Grauer et al., 2012). With Insignia, the movement of the tooth does not depend on the position
of the indirectly bonded bracket, but rather it depends on the position of the slot within the
bracket (Grauer et al., 2012). The orthodontic treatment with Insignia can then be treated with
straightwires and sliding mechanics (Grauer et al., 2012). Suresmile, another customized
appliance, uses a robot fabricated customized wire that engages into the orthodontists bracket
system of choice (Grauer et al., 2012). The lingual customized appliance system, Incognito,
utilizes customized bracket bases, bracket slots, and archwires to generate a fully customized
lingual appliance (Grauer et al., 2012).

11
INBRACE is a customized lingual appliance that utilizes the latest advancements in
indirect bonding, self-ligation, and computer-aided design and manufacturing (CAD/CAM)
technology (Tong et al., 2019). Unlike most other lingual appliances that stem from the
traditional straightwire appliances where the prescriptions are within the brackets, INBRACE
uses zero prescription in the brackets. Instead, the full three-dimensional customization is built
into the INBRACE archwires, known as Smartwires. The Smartwire is a multiloop NiTi wire
that is designed digitally from the INBRACE virtual setup. Since the prescription is built into the
Smartwire, the Smartwire is designed to open and close space, and correct any in-out, up-down,
tips, rotations, and torques. Within the Smartwire are two different types of loops; interdental
loops and locking loops. Tooth movement is programed into the interdental loops, thus these
very in size and shape (Tong et al., 2019).

The aim of this study was to perform a three-dimensional assessment of the accuracy of
the INBRACE system indirect bonding technique. The specific goals of this study were to
identify the bonding accuracy for each one of the 6 indirect bonding segments used in the
INBRACE protocol, and between teeth within each segment.
12
MATERIALS & METHODS
This retrospective clinical study was exempt from review by the Institutional Review
Board at the University of Southern California. The sample included intraoral scans of twelve
patients with mild to moderate crowding who were being treated with INBRACE customized
lingual appliance on the upper and lower arches at the University of Southern California
Orthodontic Clinic. This study excluded patients with severe crowding and poor-quality intraoral
scans.
The sample comprised of pre-treatment and post-bonding intra-oral scans of twelve
patients scanned using the TRIOS 3 Intraoral Scanner (3Shape A/S, Copenhagen, Denmark) at
the University of Southern California Orthodontic Clinic between 2017 and 2019. The digital
scans were sent to INBRACE where after the creation of a digital setup, the brackets were
virtually positioned and the INBRACE appliance manufactured. Custom indirect bonding jigs
were fabricated to transfer the virtually positioned brackets to the patient.
The INBRACE appliance was indirectly bonded at the University of Southern California
Orthodontic Clinic by a trained resident under the direct supervision of Dr. Andre Weissheimer
and Dr. Hongsheng Tong. The bonding procedures were carefully followed from the INBRACE
bonding instruction published in the clinical guide and are listed here for ease of replication of
the study:
IDB tray preparation (as per the Indirect Bonding Instructions)
1. IDB Trays must be prepared in a low ambient light setting. Do not load the trays under
direct light.
2. Prime the brackets with a thin layer of Assure Plus while ensuring 100% coverage.
3. Dry each bracket with a tooth dryer for 3 seconds.
13
4. Check the IDB trays for holes or gaps between brackets and the gingival edge of the
tray using tip of an explorer. If a gap is found, apply a small amount of Reliance Light
Bond paste adhesive (regular viscosity). Use a microbrush to lightly spread (not push) the
adhesive to seal the gap and light cure for 5 seconds.
5. Use the Bracket Positioning Guide to determine the amount of adhesive to apply.
Reference the occlusal view of the cards and look for the thickness of the adhesive as
indicated by the RED color. If the thickness of the red is 1mm or less, the amount of
adhesive to use should be 1mm out of the syringe tip. For every additional 0.5mm shown
in red, use an additional 0.5mm of adhesive.
6. Using a plastic Hollenback instrument, plate out the correct amount of Reliance Light
Bond Paste adhesive on a mixing pad for each bracket.
7. Transfer the adhesive to the back of each bracket using the plastic Hollenback.
8. Use a microbrush lightly coated with Assure PLUS to dab the adhesive onto the
bracket base ensuring 100% coverage
9. Place the prepared IDB trays away from light in a dark-colored retainer box.

Preparation for Teeth to be Bonded
1. Instructions for teeth preparation apply only to teeth that are to be bonded with
INBRACE. Teeth to be bonded should be completely clear of plaque and any calculus
buildup.
2. Remove tongue preconditioning buttons and adhesive from teeth without injuring the
gingiva.
3. Sandblast the lingual surface of each tooth for 3 seconds and then rinse.
14
4. Install the NOLA cheek retractor with the tongue cage in place.
5. Dry the teeth with an air syringe and then apply Reliance gel or liquid etch (37%
phosphoric acid) to the lingual surface of each tooth. Leave the gel or liquid etch on for
no more than 30 seconds. Avoid interproximal areas. Check the Bracket Positioning
Guide to ensure that the gel or liquid etch covers the bracket locations.
6. Rinse each tooth with an air/water spray for 3 seconds.
7. Dry each tooth gently with an air syringe and then again with a tooth dryer for 3
seconds or until desiccated.
8. Apply a thin layer of Assure PLUS onto each tooth.
9. Dry each tooth with a tooth dryer for 3 seconds.

Bonding for Upper Arch
1. NOTE: Light curing requires 2 people – One person to hold the IDB tray segment in
place, and second person to use the high-power curing light to cure the adhesive.
2. For posterior segments, use lingual Weingart pliers to hold the IDB tray by the tab and
seat the tray in a lingualocclusal-buccal motion, ensuring a secure fit.
3. Hold the IDB tray with the index fingers of both hands, using one finger along the
length of the occlusal side and the other along the length of the lingual side.
4. While maintaining lingual and occlusal pressure on the tray, light cure each tooth for 5
seconds. Then release pressure from the IDB tray, leaving the IDB tray in place, and light
cure each tooth again for 5 seconds.
5. Carefully remove the IDB tray in a buccal-occlusal-lingual motion.
15
6. For the anterior IDB tray, hold the IDB tray between the index fingers of both hands
on the lingual side and the thumbs on the labial side. Affix the IDB tray in a lingual-
incisal-labial motion. Apply firm pressure on the lingual and labial sides of the IDB tray
while a second person light cures each tooth for 5 seconds.
7. Release pressure from the IDB tray, leaving the IDB tray in place, and light cure each
tooth again for 5 seconds.
8. To remove the IDB tray, pinch the tray from the canine areas, gently pushing toward
the midline. While pinching, remove the IDB tray in a labial-incisal-lingual motion.
9. Check for voids between any bonded brackets and teeth. If a void is present, apply a
small amount of flowable adhesive to the tip of an explorer and then fill the void.
10. Light cure all bonded brackets for 5 seconds after removing the IDB tray to complete
the bonding.

16
Figure 1. Indirect Bonding procedure on the upper arch.

Bonding for Lower Arch
1. NOTE: Light curing requires 2 people – One person to hold the IDB tray segment in
place, and second person to use the high-power curing light to cure the adhesive.
2. For the posterior segments, use lingual Weingart pliers to hold the IDB tray by the tab
and insert the tab in a lingual-occlusal-buccal motion, ensuring a secure fit.
3. Hold the IDB tray with the index finger along the length of the tray on the occlusal
side. To maintain lingual pressure on all brackets, insert 2 to 3 cotton rolls cut in half
between the NOLA tongue cage and the IDB tray, held in a vertical position.
4. To ensure no movement, apply even occlusal pressure while holding the IDB tray
steady. Light cure each tooth in the IDB tray for 5 seconds.
5. Let go of the IDB tray, remove the cotton rolls, and light cure each tooth again for 5
seconds, leaving the IDB tray in place.
17
6. Remove the IDB tray in a buccal-occlusal-lingual motion.
7. For the lower anterior IDB tray, sit in front of the patient and hold the IDB tray
between the index fingers of both hands on the lingual side and the thumbs on the labial
side and place onto teeth in a lingual-incisal-labial motion. Secure the tray firmly and
light cure each tooth from the incisal direction for 5 seconds.
8. Remove fingers from the IDB tray, and light cure each tooth for another 5 seconds.
9. Remove the IDB tray in the same fashion as with the upper arch.
10. Check for voids between any bonded brackets and teeth. If a void is present, apply a
small amount of flowable adhesive to the tip of an explorer and then fill the void.
11. Light cure all bonded brackets for 5 seconds without the IDB tray to complete the
bonding.

18
Figure 2. Indirect Bonding procedure on the lower arch.

19

Figure 3- (INBRACE, 2020): A. Segmented IDB trays for maxillary arch; B. Segmented IDB
trays for mandibular arch (UL, upper left; UA, upper anterior; UR, upper right, LL, lower left;
LA, lower anterior; LR, lower right)

After each case was indirectly bonded, a post-bonding scan of the bracket position was
obtained using the same TRIOS 3 Intraoral Scanner as was used in the initial scan, before any
smartwires were placed. The virtual bracket models from the initial scans and the post-bonding
models were saved as STL files and imported into the 3-matic 3D Modeling Software
(Materialise, Leuven, Belgium) for 3D superimposition. The post-bonding scans were
superimposed onto the virtual bracket set up models using the surface-based technique over the
teeth (best fit).
20

Figure 2- STL files Post-Bonding/Virtual Brackets superimposed. A. post-bonding model in
purple, B. superimposition of the post-bonding model and the virtual bracket models , C. Virtual
bracket models in grey

The superimposition accuracy was evaluated by iterative closest point (ICP) algorithm
and color codes maps to make sure the models were correctly superimposed. After that, virtual
bracket models and the post-bonding models, now registered, were exported as STL files and
transfer to the VECTRA Analysis Module (VAM) for the analysis of 3D images (version 2.8.3;
Canfield Scientific, Parsippany, NJ). The first step in the VAM software was to create a color
contrast between the two virtual models so that they could be differentiated in the
superimposition. Purple was selected for the virtual bracket set up, while light grey was selected
for the post-bonding scans. Second, the model was rotated so that a direct lingual view of the
bracket to be measured could be seen. Next, the “Paint Area Selection” tool was used to
highlight the bracket to be measured. Then, the “Color Surface by Distance” tool was selected,
where the “selected region of” option was highlighted (Scientific, 2018). Next, surface of the
virtual bracket position model was selected to be compared to the surface of the post bonding
scan. The color scale adjustment range was set from -0.3 to 0.3mm. The VAM software provided
minimum and maximum variation values with standard deviation, mean and root square mean
A. B. C.
21
values as well. These steps were repeated and measurements recorded for each tooth in each arch
by two different orthodontic residents for inter-examiner reliability. Both examiners repeated the
measurements 10 days after the initial measurements were taken for intra-examiner reliability.

V. Statistical Analysis
Intra-operator and inter-operator reliability were gauged by Cronbach’s Alpha.
Paired T-test was used to compare the accuracy of bracket positioning (bonding error) within the
entire sample. One-Way ANOVA was used to detect the differences in bonding errors between
the 6 different segments, and between different teeth within each segment. For the statistical
analysis, the arches were divided into three segments in the maxilla and three segments in the
mandible for a total of six segments for comparisons. The teeth within each segment were
selected to match the segmented indirect bonding trays utilized clinically for INBRACE’s IDB
protocol (one anterior segment and two posterior segments per arch). The posterior segments in
both the maxillary arch and the mandibular arch include second molar, first molar, second
premolar, and first premolar. The anterior segments consist of the canines, lateral incisors, and
central incisors. Segments are labeled URP (upper right posterior), UA (upper anterior), ULP
(upper left posterior), LRP (lower right posterior), LA (lower anterior), and LLP (lower left
posterior) (Figure 3).

22
RESULTS
Intra-operator reliability and inter-operator reliability (Cronbach’s Alpha) were above
0.9, indicating that measurements taken on the VAM software were highly consistent. Root
Mean Square (RMS) values were averaged for measurements made by both operators at different
time points. RMS values represent the sum of bracket position changes, regardless of the
direction of error. The mean surface changes from the virtual bracket position to the post
bonding scan of the entire sample were tested for potential differences using the paired T-test.
The bracket positioning in the clinical bonding (post-bonding models) was statistically
significantly different than the virtual bracket position (virtual bracket models) between all
maxillary and mandibular teeth in the sample (P < 0.0001). The average RMS is 0.332mm for all
teeth in the sample (Table 1).

To better relate the results to the clinical bonding protocol for INBRACE, One-Way
ANOVA analysis was used to determine if there was a significant difference in the bonding
discrepancy between the teeth grouped into the six segments used to indirectly bond the brackets
clinically. The results showed there were statistically significant differences in bonding errors
between the segmented IDB trays (P < 0.0001). However, these difference are not clinically
significant.

Post hoc analysis (Scheffé’s test) showed a statistically significant pairwise difference in
bonding errors between upper right posterior (URP) and lower anterior (LA) (p= 0.005), upper
anterior (UA) and lower right posterior (LRP) (p=0.039), upper anterior (UA) and lower left
23
posterior (LLP) (p= 0.015), lower right posterior (LRP) and lower anterior (LA) (p= 0.000), and
lower left posterior (LLP) and lower anterior (LA) (p= 0.000) (Table 3).
Descriptive statistical analysis of 3D Euclidean distances between orthodontic bracket
positions on the virtual bracket models and the post-bonding models (clinically bonded intraoral
scans) was performed to quantify the error in the indirect bonding protocol designed for
INBRACE (Table 4). The LRP and LLP segments showed the greatest bonding errors (0.55336
mm and 0.56340 mm, respectively) of the 6 segments, while the lowest bonding errors were
identified in UA and LA segments (0.45337 mm and 0.41032 mm, respectively) (Table 4).
To determine which teeth within each segment had the most bonding error, a separate
ANOVA was performed for each segment with tooth being the independent factor. The mean
RMS error between the upper right molar, and premolars showed no significant difference (P >
0.05) (Table 5), indicating that there was a similar amount of bonding error in all the teeth in the
URP segment. The mean RMS error between the upper canines, laterals, and centrals showed no
significant difference (P > 0.05) (Table 6), meaning that there was a similar amount of bonding
error in all the teeth in the UA segment. The mean RMS error between the upper left premolars
and 1
st
molar showed no significant difference (P > 0.05) (Table 7), meaning that there was a
similar amount of bonding error in all the teeth in the ULP segment. The mean RMS error
between the lower right 1
st
molar and premolars showed no significance (P > 0.05) (Table 8),
indicating that there was a similar amount of bonding error in all the teeth in the LRP segment.
The mean RMS error between the lower canines, lateral incisors, and central incisors showed no
significance (P > 0.05) (Table 9), meaning that there was a similar amount of bonding error in all
the teeth in the LA segment. The mean RMS error between the lower left premolars and 1
st

24
molars showed no significance (P > 0.05) (Table 10), meaning that there was a similar amount of
bonding error in all the teeth in the LLP segment.

DISCUSSION
Three-dimension superimposition is a technique used to register digital models in order to
evaluate treatment outcomes, improving clinical techniques such as indirect bonding.
Superimposition poses challenges because 3D landmark identification and superimposition
methods are hard to standardize (Ghoneima et al., 2017). Image registration is defined as
combining two or more images from different time points, each with its own coordinate system,
into a common coordinate system (Grauer et al., 2009). The Iterative closest point (ICP) method,
as used in this current study, allows superimposition by matching the corresponding closest
points on the same three dimensional surface of interest, instead of matching point registration
for superimposition (Ghoneima et al., 2017). Image registration based on an iterative closest
point (ICP) algorithm of surface-based registration (Besl and McKay, 1992) is more accurate
than landmark-based registration because surface-based registration is based on thousands of
surface points rather than a few landmarks selected manually (Ghoneima et al., 2017). Many
clinicians also consider that the surface-based registration method is more precise than landmark-
based registration because it uses more surface area compared to points (Ghoneima et al., 2017).
Because of its reported increased accuracy, surface-based image registration techniques, such as
ICP should be used when evaluating the accuracy of 3D digital models. Superimposition of the
scans using surface points calculated by 3D Euclidean distances is used to determine the
accuracy of the digital scans (Ender et al., 2016). The ability to draw valid conclusions about the
error in the IDB protocol relied on scanning accuracy and the superimposition technique. Thus,
25
surface-based superimposition of the virtual bracket models and post-bonding models using an
iterative closest point (ICP) algorithm was executed in this study for better accuracy (Besl and
McKay, 1992). Linear distances were measured between the superimposed surfaces. The
accuracy of the INBRACE bonding technique was assessed three-dimensionally using VAM’s
Color Surface by Distance tool (±300 µm visualization range) to explain linear surface changes
between the virtual bracket models (VBM) and the post-bonding models (PBM) (Scientific,
2018). VAM’s Paint Area Selection tool, which is designed for identifying regions of
dimensional differences (Claus et al., 2019), was used to create regional color maps on the
superimposed INBRACE brackets for quantitative analysis of the minimum values, maximum
values, root mean square (RMS) values, and standard deviations. RMS values represent the sum
of bracket position changes, regardless of the direction of change (Claus et al., 2019).
Most studies in current literature that have investigated bracket placement accuracy in
indirect bonding have based their measurements on a pre-determined ideal bracket position, such
as was done in this current study. The studies have compared direct versus indirect bonding by
comparing clinical bracket positioning to this pre-determined ideal position. Investigators such as
Koo et al., and Castilla et al., have used photography and calipers to measure bracket positioning
error (Koo et al., 1999, Castilla et al., 2014). Today, more accurate measuring techniques such as
digital intra-oral scans are available to provide a more precise determination of accuracy.
More recent studies on bracket placement accuracy in indirect bonding have investigated
the difference in material used for bracket transfer trays. Schmid et al. compared bracket position
accuracy with silicon transfer trays versus double vacuum formed transfer trays (Schmid et al.,
2018). Between the two types of trays, their findings showed that the silicon transfer trays
produced more accurate bracket positions (Schmid et al., 2018). This study used 3D digital scans
26
and a superimposition software, GOM Inspect Version 8 (GOM GmbH, Braunschweig,
Germany) to compare “ideal” models to “actual models (Schmid et al., 2018). In our study, the
INBRACE system also uses a silicon transfer trays which demonstrated to be accurate from the
clinical standpoint.
In the current literature, studies that describe the transfer accuracy between or for
different indirect bonding techniques are few, while most compare the accuracy of indirect
bonding to direct bonding (Schmid et al., 2018). There is a need for more in vivo studies on
indirect bonding bracket positioning accuracy, as most of the current literature is done in vitro.
This is one of the reasons we designed our clinical study; to provide evidence on the accuracy of
the IDB technique of the INBRACE appliance in order to evaluate and improve the bonding
technique.
In the present in vivo study, the average overall error of bracket position was 0.332mm
per tooth, which is not clinically relevant since this amount of inaccuracy can be negated by the
slop between the bracket and the wire that is inherent to any bracket system. When bonding
errors are greater (> .5mm), clinical discrepancies may be observed. INBRACE system has an
advanced digital technique called Digital Enhancement which can be used to overcome any
discrepancy in bracket positions between the virtual bracket models and the clinical bonding. If
treatment goals have not been met by the end of stage II in the INBRACE system, you can use
Digital Enhancement to accommodate any bracket position error that may have been made
(INBRACE, 2020). The Digital Enhancement will fabricate the wire specifically to match the
positions of the brackets after they are clinically bonded, instead of the initial set of wires that are
fabricated from the virtual bracket position set up (INBRACE, 2020). The clinician is guided to
take an intraoral scan of the patient, with all brackets, the stage II Smartwire fully engaged, and
27
all O-rings in place. The scan is then sent to INBRACE for a new digital setup, based on the
clinical (real) brackets position, for fabrication of a new set of maxillary and mandibular
Smartwires. The digital enhancement is a capability of resolving bracket position issues is not
found in any other customized lingual treatment. With the Digital Enhancement the captured
bracket position becomes more important than the virtual planned bracket position from the
initial set up, thus negating any inaccuracies caused by bonding errors.
In this study, the descriptive statistics showed the average error for each segment. The
anterior segments, in both the maxilla and the mandible showed better accuracy with the lowest
mean error in bonding (mean RMS value of .45337 mm and 0.41032 mm, respectively) (Table
4). This could be explained by the fact that the anterior segments have the easiest IDB access for
the clinician when compared to the posterior segments. The anterior segments are easiest for the
orthodontist to access when placing the IDB trays because there is less involvement with the
patient’s tongue or cheek tissue in the anterior. The posterior segments in both the mandible and
the maxilla are the segments that showed the greatest mean error and the highest maximum of all
the IDB segments (RMS values: URP; 0.53311mm, ULP; 0.50373mm, LRP; 0.55336mm, LLP;
0.56340mm) (Table 4). These values indicate that the IDB for INBRACE is slightly more
accurate in the upper and lower anterior segments than in the upper and lower posterior
segments. The discrepancy could be attributed to the limited visibility when positioning the IDB
trays in the posterior segments, along with the increased intraoral obstacles including the
patient’s tongue and cheek tissue, and the limited opening allowed by some patients. The Nola
isolation device used in INBRACE’s IDB protocol may also play a role in this greater error in
the posterior mandibular segments. Although the Nola helps to keep the tooth surfaces isolated,
the area keeping the tongue from the teeth can be bulky in some patients, making it more
28
challenging to position and secure the IDB trays on the second mandibular molars. Also, the
cotton rolls used to add lingual pressure to the posterior IDB trays in the lower arch may
interfere in the ideal IDB tray position. An alternative to the Nola for isolation could be the
Isolite systems, or something similar, that isolate one side of the mouth at a time, while keeping
the tongue farther away from the lingual tooth surfaces on the side being isolated. This would
involve slightly modifying INBRACE’s current bonding protocol which has the entire mouth
isolated all at once. It potentially would increase the bonding time but maybe would improve the
bonding accuracy in the lower posterior segment. However, this is a hypothesis has not been
tested yet.
The difference in bonding error for teeth within each segment was insignificant (P >
0.05), indicating that the error of one bracket in a segment was very similar to the error of the
other brackets in the same segment. This could be due to the rigidity of the IDB tray itself.
Clinically, it is important to know that there is no difference in error between the teeth within
each bonding segment to know that the IDB trays are adequate and not a contributing factor to
human bonding error. Since the clear silicon IDB trays used in the INBRACE system are semi-
rigid, there is not much play that can occur between one bracket and the next when placing the
tray on the teeth to be bonded.

CONCLUSION

This study showed the INBRACE system had a good bonding accuracy (average error
0.33m) which is considered clinically accurate and acceptable for a customized lingual
appliance. The bonding accuracy was better for the anterior segments, in both maxillary and
29
mandibular arches, when compared to the posterior segments. Lastly, there was no difference in
the bonding accuracy for individual teeth within each IDB tray.

30
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33
Table 1. Paired T Test
P value 0.0001***
Mean
Difference
0.332

*- p ≤0.05. The mean difference is significant at the 0.05 level
**- p ≤0.01
***- p≤0.001

34

Table 2. One-Way ANOVA of RMS values (mm) by IDB Segment
SS Df MS F P value
Between
Groups
0.916 5 0.183 8.862 0.00001***
Within
Groups
5.728 277 0.021
Total 6.644 282

SS, sum of squares; df, degrees of freedom; MS, mean squares; F, F statistic; F critical
value, P-Value
*- p ≤0.05. The mean difference is significant at the 0.05 level
**- p ≤0.01
***- p≤0.001

35

Table 3. Scheffé’s post hoc analysis of RMS values (mm) by tooth
segment.
Pair Mean Difference P value
URP v. UA 0.079740 0.185
URP v. ULP 0.029388 0.977
URP v. LRP -0.020248 0.996
URP v. LA 0.122791 0.005**
URP v. LLP -0.030290 0.974
UA v. ULP -0.050353 0.697
UA v. LRP -0.099988 0.039*
UA v. LA 0.043051 0.712
UA v. LLP -0.110031 0.015*
ULP v. LRP -0.049636 0.811
ULP v. LA 0.093403 0.082
ULP v. LLP -0.059678 0.658
LRP v. LA 0.143039 0.000***
LRP v. LLP -0.010042 1.000
LA v. LLP -0.153081 0.000***

URP, Upper right posterior, UA, Upper anterior; ULP, Upper left posterior; LRP,
Lower right posterior; LA, Lower anterior, LLP, Lower left posterior;
Sig, significance (P-value)
*- p ≤0.05. The mean difference is significant at the 0.05 level
**- p ≤0.01
***- p≤0.001

36

Table 4. Descriptive Statistics (mm)
Segment Min Max Median RMS Mean SD
URP 0.253 0.820 0.56913 0.53311 0.14796
UA 0.208 0.747 0.51246 0.45337 0.150867
ULP 0.262 0.895 0.52905 0.50373 0.155330
LRP 0.317 0.919 0.56830 0.55336 0.157598
LA 0.297 0.562 0.39191 0.41032 0.065449
LLP 0.251 0.927 0.55941 0.56340 0.185894

URP, Upper right posterior, UA, Upper anterior; ULP, Upper left posterior; LRP, Lower right
posterior; LA, Lower anterior, LLP, Lower left posterior; Min, minimum; Max, maximum; SD,
standard deviation

37
Table 5. One-Way ANOVA URP (teeth within segments)
Sum of
Squares
Df Mean
Square
F P value
Between
Groups
0.117 2 0.058 2.940 0.067
Within
Groups
.635 32 0.020
Total .751 34

SS, sum of squares; df, degrees of freedom; MS, mean squares; F, F statistic.

38
Table 6. One-Way ANOVA UA (teeth within segments)
Sum of
Squares
Df Mean
Square
F P value
Between
Groups
0.007 2 0.003 141 0.869
Within
Groups
1.564 67 0.023
Total 1.570 69

SS, sum of squares; df, degrees of freedom; MS, mean squares; F, F statistic; P-Value

39

Table 7. One-Way ANOVA ULP (teeth within segments)
Sum of
Squares
Df Mean
Square
F P value
Between
Groups
0.110 2 0.055 2.531 0.095
Within
Groups
.694 32 0.022
Total .804 34

SS, sum of squares; df, degrees of freedom; MS, mean squares; F, F statistic.

40
Table 8. One-Way ANOVA LRP (teeth within segments)
Sum of
Squares
Df Mean
Square
F P value
Between
Groups
0.095 2 0.048 2.255 .121
Within
Groups
.675 32 0.021
Total .770 34

SS, sum of squares; df, degrees of freedom; MS, mean squares; F, F statistic.

41
Table 9. One-Way ANOVA LA (teeth within segments)
Sum of
Squares
Df Mean
Square
F P value
Between
Groups
0.003 2 0.001 .305 0.738
Within
Groups
.254 58 0.004
Total .257 60

LA, lower anterior; SS, sum of squares; df, degrees of freedom; MS, mean squares; F, F statistic.

42
Table 10. One-Way ANOVA LLP (teeth within segments)
Sum of
Squares
Df Mean
Square
F P value
Between
Groups
0.102 2 0.051 1.546 0.229
Within
Groups
1.056 32 0.033
Total 1.158 34

SS, sum of squares; df, degrees of freedom; MS, mean squares; F, F statistic.

43

Figure 3. Illustration of VAM program used to calculate the distances in bracket position
between the virtually positioned bracket model and the post bonding scan. Column A. is the
virtually positioned bracket model with the bracket highlighted. Column B. is the image you see
after you select “calculate distances” on the right side of the software screen. Column C. is
showing the two models superimposed over one another.

A. B. C.
44

45

46

47

48

Figure 4. Step by step visualization of measurements taken within the VAM software.

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Asset Metadata

Creator Gutierrez, Zoey (author)

Core Title Bonding accuracy of a novel lingual customized orthodontic appliance (INBRACE™): an in-vivo study

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 02/26/2020

Defense Date 02/26/2020

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag accuracy,computer aided design and computer aided manufacturing,digital technology,INBRACE,indirect bonding,lingual appliance,lingual orthodontics,OAI-PMH Harvest,self ligating,Smartwire

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Paine, Michael (committee chair), Ahn, Ji Hyun (committee member), Sameshima, Glenn (committee member)

Creator Email zgutierr@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c89-275268

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