Download Density value means in the evaluation of external apical root

Dentomaxillofacial Radiology (2007) 36, 130–137
q 2007 The British Institute of Radiology
http://dmfr.birjournals.org
RESEARCH
Density value means in the evaluation of external apical root
resorption: an in vitro study for early detection in orthodontic
case simulations
FE Eraso*,1, ET Parks2, WE Roberts1, WF Hohlt1 and S Ofner3
1
Department of Oral Facial Development, Indiana University School of Dentistry, Indianapolis, IN, USA; 2Department of Oral
Pathology, Medicine and Radiology, Indiana University School of Dentistry, Indianapolis, IN, USA; 3Division of Biostatistics,
Indiana University School of Medicine, Indianapolis, IN, USA
Objectives: The purpose of this study was to develop an alternative diagnostic tool for the early
detection of external apical root resorption (EARR).
Methods: Mandibular incisors (n ¼ 36) with and without simulated EARR lesions were used.
18 teeth with facial and proximal windows, each with a range of 2 sizes, were placed in 6 N
hydrochloric acid (HCl) baths for 10 min. A sample of the acid solution was analysed for calcium
concentration by atomic absorption spectrophotometry. Incisors were imaged at 808, 908 and 1008
under 3 test conditions (bracketed, non-bracketed and with subtraction registration templates
(SRTs)). The images were reconstructed and subtracted to determine the accuracy and sensitivity of
the method. Quantified histograms for each subtracted image were constructed.
Results: At either an angle of 808 or 1008, the bracketed group had the largest mean standard
deviation of the subtraction histograms while the SRT group had the smallest. Density values as a
function of total calcium removed were plotted indicating a linear relationship between subtraction
density units and calcium loss.
Conclusion: The use of the SRTs was significantly more accurate than the use of the brackets
alone for digital subtraction radiography reconstructions. This model shows promise for detecting
EARR prior to a noticeable decrease in root length. It may be useful for early detection of resorptive
lesions during routine orthodontic treatment.
Dentomaxillofacial Radiology (2007) 36, 130–137. doi: 10.1259/dmfr/97564373
Keywords: root resorption, digital subtraction radiography, root apex, orthodontics
Introduction
External apical root resorption (EARR) has been defined as
a reduction in the length of the root from the apex. The
amount of tooth structure lost is determined from
measuring the entire tooth length, incisal edge to apex in
anterior teeth and cusp tip to the most apical point of the
root in posterior teeth, both before and after treatment.1,2
Numerous histologic and radiographic studies have
produced conflicting results relative to the association of
apical resorption with orthodontic treatment. Most of this
variability can be attributed to the non-standardized
methodology, which limits the comparability of results
*Correspondence to: Dr Francisco Eduardo Eraso, Indiana University School of
Dentistry, Department of Oral Facial Development, Indianapolis, IN 46202-5186,
USA; E-mail: [email protected]
Received 12 July 2005; revised 27 March 2006; accepted 1 April 2006
from these different studies. In addition, radiographic
studies evaluate only apical root resorption; however,
buccal or lingual resorption is less perceptible in the
radiographs.1,3 Although histologic or scanning electronic
microscopic investigations provide exact results, they can
only be conducted on single representative teeth. Therefore, studies based on larger samples, within and between
patients, use only radiological methods.4
In orthodontic practice, studies have reported the
diagnosis of EARR using conventional radiographs
(periapicals, panoramic, lateral cephalograms and various
combinations).2,5 – 15 However, several factors play an
important role in radiographic interpretation, such as the
amount of distortion, magnification, lack of reproducibility
and the projection of three-dimensional structures in twodimensional planes (radiographic films). Furthermore, a
Evaluation of external apical root resorption
FE Eraso et al
large amount of mineral loss (30 – 60%) is needed to render
a defect visible on radiographs. These factors severely
limit the radiographic detection of early EARR.
Early detection of small resorptive lesions during
orthodontic treatment is essential for identifying teeth at
risk of severe resorption.16 Interruption of active treatment
can minimize adverse effects during subsequent treatment.17 Although conventional intraoral radiography is the
method of choice of orthodontists for detecting apical root
resorption during treatment, it has inherent disadvantages,
especially in the diagnosis of early resorption.
Quantitative measurements must be taken to determine
early EARR density changes. Digital subtraction radiography (DSR) satisfies this requirement. Detection limits of
DSR vs conventional radiographs show that DSR is more
sensitive to density changes.18 However, it is important to
compensate for the difficulties in accurately registering the
images and minimizing the amount of structured noise
present in the subtracted images. In this regard, a recent
study used an orthodontic bracket as a reference marker for
DSR and showed that the clinician can accurately monitor
and assess changes occurring in hard tissues (i.e. early root
resorption lesions) during orthodontic treatment.19
Using orthodontic bracket and subtraction registration
templates (SRTs) in addition to previously developed
techniques showed a reduction in the occurrence of
structured noise in subtracted images of disparate projection geometries. Improving the accuracy of digital
subtraction is important to assist in research applications
of interest to orthodontists, particularly with regard to the
detection of early root resorption. This would contribute to
the improvement of clinical applications, such as monitoring patients genetically susceptible to root resorption.
The potential advantage of early quantitative radiographic evaluation of root resorption has not been evaluated
clinically. The present study investigates this capability to
evaluate the risk of root resorption at the early stages of
orthodontic case treatment. Orthodontically induced apical
root resorption is progressive during treatment and followup radiographs are therefore mandatory.16,20 The present
study focused on the importance of early lesion detection
in vitro before it could be relied on in orthodontic patients.
The null hypothesis for the initial portion of the present
study was that digital subtraction images are not more
accurate when using an orthodontic bracket or SRT as
reference markers, as compared with images of teeth with
no brackets. For the second stage of the study, the null
hypothesis was that digital subtraction software used in
conjunction with brackets or SRT as references will not be
able to detect simulated EARR lesions as measured by
density changes. As previous studies indicated, DSR may
have the potential to be a sensitive technique for
quantitative evaluating root resorption; however, there is
currently no report in the literature applying DSR for early
detection of EARR in orthodontic case simulations.
131
Materials and methods
36 intact human mandibular incisors were used in this
study. For the image acquisition, an X-ray source with a
CCX Digital Computer Controlled X-ray Timer (Trophy
Radiologic Inc., Vincennes, France) operating at 70 kVp
and 8 mA was used. Images were acquired with the Sigma
size 2 digital sensor (Instrumentarium Imaging, Milwaukee, WI). A custom sensor holder was fabricated using
Exaflex vinyl polysiloxane impression material (GC
America Inc., Alsip, IL). The root tip of every tooth was
embedded into a mould with two pieces of 3 mm Splint
Biocryl to secure them and to simulate bone around the
apex. A 1 inch tissue-equivalent acrylic block was used,
which was found to be adequate for tissue equivalency in a
previous study.21 The Dental X-ray Co-ordinate System
DX-CS1 (RC Eggleton Consulting, Indianapolis, IN)
radiographic positioning device was selected to orient the
specimens, sensor and X-ray source in a reproducible
manner (Figure 1). This device has a specimen mounting
site designed to hold a Peel-A-Way embedding mould
(Rectangular-R30, Polysciences Inc., Warrington, PA).
Each specimen was imaged at 808, 908 and 1008 as
measured on the Dental X-ray Co-ordinate System DX-CS1
protractor. These measurements simulated 108 of labial
(808) and lingual (1008) tip rotation around the root apex.
The 908 image was not tipped and was used as the baseline
or reference image. Exposure time was 0.08 s for each
specimen. Images were captured and stored using CliniView 3.5 (GE Health Care, Milwaukee, WI) imaging
software. Each specimen was imaged at the aforementioned
angles with an orthodontic bracket and with fiducial
markers attached to the bracket. The additional fiducial
markers, four small lead spheres, measuring approximately
1 mm in diameter, were spaced 8 mm apart and custom
fitted to the orthodontic bracket for this study (Figure 2).
APC II Victory Series Low Profile MBT 0.018 slot lower
incisor orthodontic brackets (3M Unitek, Monrovia, CA)
were bonded 3.5 mm from the incisal edge using Transbond
Plus Self Etching Primer and Transbond resin (3M Unitek).
For the first part of the study, three digital images were
obtained per group (no bracket, bracket and bracket with
Figure 1 The Dental X-ray Co-ordinate System DX-CS1 (RC Eggleton
Consulting, Indianapolis, IN) radiographic positioning device was
selected to orient the specimens, sensor and X-ray source in a reproducible
manner
Dentomaxillofacial Radiology
Evaluation of external apical root resorption
FE Eraso et al
132
Figure 2 An example of an image of the resulting subtraction
registration template (SRT) containing four coplanar radiopaque spheres,
custom fitted to the orthodontic bracket
SRT) at 808, 908 and 1008 angulations, so nine images were
obtained per tooth. These images were exported from
CliniView and stored as tagged image file format files.
Image reconstruction and subtraction were performed using
the Emago/advanced 3.5 software (Oral Diagnostic Systems,
Amsterdam, The Netherlands) by two oral and maxillofacial
radiologists. This software offered geometric image reconstruction to accommodate differences in projection
Figure 3
geometry between images. This reconstruction attempted to
produce two images with identical image projection geometry
by mapping the information contained in one image onto the
projection plane of another image, called the reference
image.22 The reference image for each group was that taken
at 908 angulation. Each tipped image was reconstructed with
the following reference points. For the no bracket group: left
cemento-enamel junction (CEJ), right CEJ, apex and midpoint
of incisal edge; for the bracket group: left superior aspect of
the bracket, right superior aspect of the bracket, a point on
the middle inferior aspect of the bracket and the root apex;
and for the SRT group: the middle of the left superior sphere,
the middle of the right superior sphere, a point on the middle
inferior aspect of the bracket and the root apex.
The reconstructed images were then subtracted from the
reference image, 08 angulation (908). Linear subtraction was
used, resulting in the arithmetic difference of the grey values
of the two images at corresponding locations.22 The region of
interest (ROI) in the subtraction was defined as the apical third
of the root (Figure 3). The standard deviation and the mean of
the subtraction histogram in the ROI were recorded. The ROI
determination was repeated three times for each subtraction.
The standard deviation and mean were averaged.
EARR lesions were created using 6 N hydrochloric acid
(HCl) baths according to the model of chemically induced
lesions used in a previous study.23 This method produces
lesions with ill-defined borders that more closely resemble
naturally occurring EARR lesions. The 36 teeth used in the
previous reconstructions were coated three times at 1 h
intervals with a thin acid-resistant layer (nail polish), except
for the one area (2 £ 2 mm or 1 £ 1 mm) to be decalcified.
After pre-alteration radiographs (control group—no lesion)
were obtained, the teeth were demineralized in a sequential
fashion. 18 teeth with facial windows and 18 teeth with
proximal windows were placed individually in 15 ml tubes
containing 5 ml of 6 N HCl for 10 min intervals 6 times
An example of the area of interest in the subtraction images, defined as the apical third of the tooth root
Dentomaxillofacial Radiology
Evaluation of external apical root resorption
FE Eraso et al
10 minutes
20 minutes
133
30 minutes
INITIAL RADIOGRAPH
40 minutes
50 minutes
60 minutes
Figure 4 Digital subtraction radiography of an example for an orthodontic case simulation of a 2 £ 2 mm proximal EARR artificially created lesion after
10 min intervals of 6 N hydrochloric acid baths (908)
(Figure 4). Consequently, lesions were produced with a
range of two sizes and two locations.
A previous study determined the rate of decalcification
so that meaningful images were generated over specific
time intervals.23 For the present study, the acid solution
used for two teeth with 2 £ 2 mm lesions (one facial and
one proximal) was analysed for calcium concentration by
atomic absorption spectrophotometry (Perkin – Elmer 306
Atomic Absorption Specthrophometer) after each step in
the demineralization process. The teeth were sequentially
demineralized, placed back into the mounting device and
imaged in the manner described earlier. Reconstructions
and linear subtractions were performed for each tooth and
angle for the SRT group. The volume under the histogram
was computed, which gave a weighted density value of
each lesion in terms of density units.
were then used in the ANOVA model to test for differences
between the groups at each angle of rotation.
The sign test was used to test for significant median change
in density from baseline for teeth in the SRT group by lesion
size, surface, angle and time in the acid bath. Significant
median change in density demonstrates digital subtraction’s
ability, with use of the SRT reference point, to detect early
root resorption. For one facial and one proximal lesion,
regression lines were used to quantify the linear relationship
between density units and the amount of calcium lost.
The reconstructions and subtractions for ten randomly
selected teeth were completed twice, independently of
each other, to assess intraclass correlation coefficient (ICC)
and interrater reliability (IRR).
Results
Statistical methods
Since the mean of the subtraction histogram did not reflect the
closeness of the repositioned image to the original image, the
standard deviation of the subtraction histogram was considered to be a better measure of the ability of the software to
reposition the tipped image to the original image; therefore,
the primary comparison of the three groups was based upon
mean standard deviations of the subtraction histograms.
Mean standard deviations of the subtraction histograms
were summarized for each group and angle of rotation. For
each angle of rotation, groups were compared through use of
an analysis of variance (ANOVA) model with fixed effect for
group and random effect for tooth. The random effect allowed
for incorporation of any correlation that resulted from
repeated measurements of the same tooth. Residual plots
were examined for deviation from the model assumptions of
homogeneity of variance and normality. At each angle of
rotation, the Tukey–Kramer adjustment was used to control
the error of falsely claiming a significant difference (type 1
error). Since the residual plots showed some deviation from
the assumption of homogeneity of error, the standard
deviations were log-transformed. The log-transformed data
900 images from 36 teeth were measured using the Emago
software. At an angle of either 808 or 1008, the bracketed
group had the largest mean standard deviation of the
subtraction histograms, while the SRT group had the
smallest mean standard deviation (Table 1). Statistical
comparisons revealed that at both angles, mean standard
deviation for the bracketed group was significantly larger
than for the non-bracketed or SRT group. There was no
significant difference in mean standard deviation between
the SRT group and the non-bracketed group (Table 2).
Table 1
Mean standard deviation of subtraction histograms
Angle
(degrees)
Group
N
Mean
SD
Min.
Median
Max.
80
80
80
100
100
100
No bracket
Bracket
SRT
No bracket
Bracket
SRT
36
33
36
34
36
36
9.94
12.95
9.21
8.51
11.17
7.00
2.56
4.60
2.54
3.02
4.39
1.80
3.94
5.04
4.95
4.58
5.13
4.06
9.98
12.36
8.72
7.70
10.29
6.65
15.47
22.10
14.08
15.92
22.38
13.19
SD, standard deviation; SRT, subtraction registration template
Dentomaxillofacial Radiology
Evaluation of external apical root resorption
FE Eraso et al
134
Table 2
Comparisons of log-transformed mean standard deviations
Angle
(degrees)
Group
vs Group
Estimate
Std error
P value*
80
80
80
100
100
100
Bracket
Bracket
No bracket
Bracket
Bracket
No bracket
No bracket
SRT
SRT
No bracket
SRT
SRT
0.24
0.32
0.08
0.25
0.42
0.17
0.07
0.07
0.07
0.08
0.08
0.08
0.0040
0.0001
0.5088
0.0059
,0.0001
0.0895
*P value adjusted for multiple comparisons using Tukey – Kramer
adjustment. SRT, subtraction registraction template
Significant changes in median density were first seen in
the 1 £ 1 mm lesion group on the facial surface at 10 min,
30 min and 50 min at angles of 808, 908 and 1008,
respectively. For 1 £ 1 mm lesions on proximal surfaces,
significant changes in median density were first seen at
40 min at each angle of rotation (Table 3).
For the 2 £ 2 mm lesions on facial surfaces, significant
change in median density was first detected at 10 min at
rotations of 808 and 908. After 10 min, changes from baseline in median density were not statistically significant for
the 808 rotations. In contrast, significant changes in median
density were detected at each time point for 908 rotations.
Table 3
The first significant change in median density at 1008 was
detected after 60 min in the acid bath. For 2 £ 2 mm lesions
on proximal surfaces, significant changes in median density
were first detected at 10 min for rotations of 808 and 908.
Significant changes were also detected at each time point
after 10 min for these two angles. For the 1008 rotation, the
earliest detection of significant change in median density
occurred 30 min into the acid bath (Table 4).
The ICCs were high, indicating good repeatability of
mean density and standard deviations of subtraction
histograms at each angle of rotation. The ICC was lowest
for standard deviations at 808, where 11% of the total
variation comes from repeated measurements. The interexaminer IRRs were low, indicating poor repeatability of
measurements between the two examiners.
Table 5 shows mean calcium lost, the total calcium
removed, density values and changes in density for facial
and proximal lesion sites two teeth with 2 £ 2 mm lesions.
Density as a function of total calcium removed was plotted.
The regression lines indicate a linear relationship between
subtraction density units and calcium loss, and provide a
possible method of quantifying digital subtraction
examples (Figure 5).
Summary statistics of mean density for SRT group (1 £ 1 mm)
Size (mm)
Surface
1£1
Facial
Angle
80
90
100
Proximal
80
90
100
SD, standard deviation; SRT, subtraction template
Dentomaxillofacial Radiology
Time
n
Mean density
SD
Min.
Median
Max.
10
20
30
40
50
60
10
20
30
40
50
60
10
20
30
40
50
60
10
20
30
40
50
60
10
20
30
40
50
60
10
20
30
40
50
60
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
127.9
127.6
126.6
126.6
125.5
124.7
126.3
125.8
124.8
124.5
124.5
124.1
129.3
129.5
128.1
127.6
127.3
126.7
130.1
129.2
128.3
128.1
126.6
126.6
127.4
126.4
125.9
125.4
125.5
125.0
130.6
130.0
129.1
128.6
128.5
128.1
2.2
2.6
2.8
3.0
2.7
3.0
1.2
1.7
1.9
2.0
3.0
2.5
2.1
1.7
2.0
2.2
2.7
2.4
3.6
3.5
2.6
3.5
3.0
3.3
1.0
0.8
1.1
1.6
2.0
1.9
0.7
1.3
1.2
1.5
1.6
1.8
125.5
125.0
123.8
123.5
122.6
121.1
124.5
123.6
122.2
121.3
120.2
121.6
125.9
126.8
124.9
123.9
123.1
122.9
126.6
125.5
125.9
125.2
124.4
123.5
126.2
125.5
124.4
123.5
123.3
123.1
129.7
128.6
127.6
127.1
126.6
125.2
128.0
127.5
125.5
126.0
124.7
123.3
126.7
126.3
125.2
124.8
124.6
123.4
129.9
129.4
128.4
127.6
127.0
126.4
128.7
128.2
127.3
126.3
125.1
124.8
127.2
126.0
125.9
125.6
125.1
124.7
130.6
129.5
128.9
128.1
128.0
128.4
132.4
132.4
131.5
132.1
130.0
129.5
127.8
128.5
128.4
127.6
130.4
129.4
132.3
132.2
130.5
130.3
132.5
131.1
137.0
134.7
132.9
133.3
132.3
132.7
129.0
127.5
127.4
128.6
129.8
129.0
131.5
132.3
131.2
130.9
130.6
129.8
Evaluation of external apical root resorption
FE Eraso et al
Table 4
135
Summary statistics of mean density for SRT group (2 £ 2 mm)
Size (mm)
Surface
2£2
Facial
Angle
80
90
100
Proximal
80
90
100
Time
n
Mean density
SD
Min.
Median
Max.
10
20
30
40
50
60
10
20
30
40
50
60
10
20
30
40
50
60
10
20
30
40
50
60
10
20
30
40
50
60
10
20
30
40
50
60
9
9
9
9
9
9
9
9
9
9
9
8
9
9
9
7
8
8
8
9
9
9
8
8
9
9
9
9
9
9
9
9
9
9
9
9
131.8
131.5
130.8
129.9
130.1
129.2
125.6
124.7
124.0
123.3
123.6
123.6
129.4
128.2
128.2
129.3
127.5
126.6
131.8
131.7
131.3
130.6
130.0
129.0
126.0
125.0
124.2
123.7
123.5
122.1
131.1
129.9
128.2
127.5
127.8
126.8
3.9
4.4
4.8
5.0
5.3
5.3
1.8
1.9
2.2
2.3
2.8
2.6
3.0
3.3
3.9
3.7
4.0
3.0
2.6
2.6
2.6
2.3
2.5
2.6
0.8
1.2
1.3
1.2
2.0
1.5
2.8
1.6
1.8
2.2
2.1
1.7
127.2
126.2
125.5
124.1
123.7
121.5
121.1
120.3
120.0
119.3
118.3
117.6
125.1
123.9
123.5
122.6
121.7
121.3
127.8
126.4
125.4
125.2
124.3
123.9
124.8
123.1
122.9
122.2
120.1
119.6
128.0
127.5
124.3
123.2
124.4
123.9
130.7
133.2
132.5
132.1
130.9
129.9
126.1
125.3
124.8
123.5
124.6
124.5
128.9
128.0
127.5
129.6
126.9
127.2
132.9
132.4
131.5
131.5
131.0
129.6
126.1
125.4
124.0
123.6
123.5
122.2
130.1
129.9
128.7
127.5
127.4
126.5
139.7
139.2
138.8
137.6
136.8
136.3
127.0
126.5
126.0
126.0
126.0
125.4
134.1
135.1
134.4
133.5
133.9
130.3
134.3
134.4
133.7
133.0
132.1
131.5
127.0
126.5
126.2
125.6
127.2
123.9
136.5
131.7
130.1
131.1
131.1
129.6
SD, standard deviation; SRT, subtraction registraction template
Previous in vitro studies concentrated on the diagnostic
accuracy for detecting lesions using conventional intraoral
radiographs and DSR through receiver operating characteristics analysis. Teeth length as well as quantitative
analysis were done in these studies.23,24 Our in vitro model
showed promise for detecting EARR prior to a noticeable
decrease in root length, which may be useful for early
detection of resorptive lesions during routine orthodontic
treatment. It also confirmed previous reports24 that
Discussion
Early detection of small EARR lesions during orthodontic
treatment is essential for identifying teeth at risk of severe
resorption.16 The ability to accurately quantify these early
changes associated with EARR is valuable and has been
suggested as possible in our study. Even though the present
investigation was in vitro, it is important to take into
account its constraints to validate the methodology of
image reconstruction before it is relied upon clinically.
Table 5 For each acid bath, the mean and total calcium (Ca) removed, density values and change in density values for facial and proximal lesion sites for
the orthodontic case simulations
Ca removed
(mg ml21)
Total Ca removed
Density
D Density
No. of acid baths
F
P
F
P
F
P
F
P
0
1
2
3
4
5
6
0
0.11
0.07
0.04
0.05
0.07
0.07
0
0.12
0.06
0.05
0.04
0.01
0.03
0
0.11
0.19
0.23
0.27
0.34
0.41
0
0.12
0.17
0.22
0.26
0.27
0.30
127.00
125.78
123.98
121.36
120.52
119.79
.
127.00
124.78
123.41
123.02
122.65
120.13
119.55
0
2 1.20
2 1.80
2 2.62
2 0.84
2 0.73
0
22.20
21.37
20.39
20.37
22.52
20.58
F, facial; P, proximal
Dentomaxillofacial Radiology
Evaluation of external apical root resorption
FE Eraso et al
136
Figure 5
Plot of density values as a function of total calcium removed Y ¼ 128.63 2 27.99x for facial lesions Y ¼ 128.11 2 26.23x for proximal lesions
quantitative analysis of small amounts of apical root
resorption can be performed by means of DSR.
In vitro studies simulated EARR lesions by drilling the
entire depth of the dental bur heads.3,23 – 25 However,
changes in dentin that occur under biological conditions
will differ from the type of defects produced by a dental
bur. In addition, the borders of artificially created defects
are relatively sharp compared with those of biological
origin, which tend to be more diffused. Our simulation of
early EARR lesions was created using the model of
chemically induced lesions used in a previous study,23
which produced lesions with ill-defined borders that more
closely resembled naturally occurring EARR lesions.
As far as projection geometry, the first hypothesis
addressed one of the major obstacles in the use of digital
subtraction, which is the geometric reproducibility. In
the past, occlusal orthotics as well as cephalometric
stabilization methods have shown considerable reduction
in projection geometric errors.26,27 However, at the time
of clinical application they are costly, time consuming
and cumbersome. Our method explored digital subtraction using direct digital radiography and reference
points, including anatomical landmarks, orthodontic
brackets and additional fiducial marks as aids for
reconstructions. Due to stability over time, the use of
anatomical landmarks has been used in digital subtraction studies.24,28 Our study indicated that use of SRTs, in
conjunction with anatomical landmarks and orthodontic
brackets, is a reliable alternative in the assessment of
EARR in orthodontic case simulations.
This investigation also addressed changes of axial
inclination that would occur during typical orthodontic
tooth movement for EARR lesions located in the buccal
and proximal surfaces. Even though structural “noise”
produces visual confusion and limits the detection of small
lesion, as reported before,24 our study suggests that our
reconstruction model of DSR is a consistent method for
demonstrating density changes over time in simulated
EARR lesions located proximally or facially. These
findings will stimulate the application of DSR as a possible
part of routine orthodontic documentation, which would be
very useful in orthodontic practice to detect and control
EARR, particularly in patients considered to be at high risk
for this process.
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