Content uploaded by Alvin Wee
Author content
All content in this area was uploaded by Alvin Wee on Dec 28, 2020
Content may be subject to copyright.
Three-Dimensional Accuracy of Conventional Versus Digital
Complete Arch Implant Impressions
Berkman Albayrak, DDS ,1Cortino Sukotjo, DDS, PhD ,2Alvin G Wee, DDS, PhD, MPH,3
˙
Ismail Hakkı Korkmaz, PhD,4& Funda Bayındır, DDS, PhD5
1Department of Prosthodontics, Bahçe¸sehir University School of Dental Medicine, Istanbul, Turkey
2Department of Restorative Dentistry, University of Illinois at Chicago College of Dentistry, Chicago, IL
3Division of Prosthodontics, Department of Restorative Sciences, University of Minnesota School of Dentistry, Minneapolis, MN
4Department of Mechanical Engineering, Erzurum Technical University Faculty of Engineering and Architecture, Erzurum, Turkey
5Department of Prosthodontics, Atatürk University Faculty of Dentistry, Erzurum, Turkey
Keywords
Accuracy; angulated implants; conventional
implant impressions; digital implant
impressions; complete arch.
Correspondence
Dr. Berkman Albayrak, Department of
Prosthodontics, Bahçe¸sehir University School
of Dental Medicine Istanbul 34374, Turkey.
E-mail: berkmanalbayrak@gmail.com
Presented at the 25th Turkish Dental
Association International Dental Congress,
Istanbul, Turkey, September 2019
The authors deny any conicts of interest in
regards to this study.
Accepted September 10, 2020
doi: 10 . 1111 / j o p r. 1 3264
Abstract
Purpose: The accuracy of digital impressions is still controversial for complete arch
implant cases. The aim of this study is to compare the accuracy of different intrao-
ral scanners with the conventional technique in terms of trueness and precision in a
complete arch implant model.
Material and Methods: Eight implants were inserted asymmetrically in a
polyurethane edentulous mandibular model with different angulations. A 3-
dimensional (3D) reference model was obtained by scanning this polyurethane model
with an optical scanner. First, digital impressions were made by using 3 different in-
traoral scanners: Carestream 3500 (DC), Cerec Omnicam (DO) and 3Shape Trios 3
(DT). Subsequently, a nonsplinted open tray impression technique was used for con-
ventional impression group (C) and then the master casts were digitalized with a lab
scanner. Each 10 STL files belonging to 4 different impression groups were imported
to a reverse engineering program, to measure distance and angle deviations from the
reference model. All statistical analyses were performed after taking absolute values
of the data. After comparing the impression groups with one-way ANOVA, the true-
ness and precision values were analyzed by Tukey post hoc test and 0.05 was used as
the level of significance.
Results: The mean trueness of distance was 123.06 ±89.83 µm for DC, 229.72
±121.34 µm for DO, 209.75 ±47.07 µm for DT, and 345.32 ±75.12 µm for C
group (p<0.0001). While DC showed significantly lower deviation compared to
DO and C, no significant difference was found between DC and DT. C showed the
highest distance deviation significantly in all groups; and no significant difference
was found between DO and DT groups. In angle measurements; the trueness was
0.26° ±0.07° for DC, 0.53° ±0.42° for DO, 0.33° ±0.30° for DT, and 0.74° ±
0.65° for C group. There was no significant difference between the groups in terms
of angular trueness (p=0.074). In terms of the precision for distance, the results of
DC 80.43 ±29.69 µm, DO 94.06 ±69.96 µm, DT 35.55 ±28.46 µm and C 66.97
±36.69 µm were determined (p=0.036). The significant difference was found only
between DT and DO among all groups. Finally, angular precision was determined to
be 0.19° ±0.11° for DC, 0.30° ±0.28° for DO, 0.22° ±0.19° for DT, and 0.50° ±
0.38° for Group C. No significant difference was found between the groups, in terms
of angular precision (p=0.053).
Conclusions: All digital impression groups yielded superior data compared to con-
ventional technique in terms of trueness. DC formed the impression group with the
highest trueness in both distance and angular measurements. The results of this in
vitro study suggest the use of intraoral scanners compared to the conventional im-
pression techniques in complete arch implant cases with high angulations.
1
Journal of Prosthodontics 0(2020) 1–8 © 2020 by the American College of Prosthodontists
Accuracy of Complete Arch Implant Impressions Albayrak et al
Digital impressions made with intraoral scanners (IOS) have
started to find a comprehensive place in the clinical routine
in dentistry, which has entered the era of digital production.
The use of IOS, which has demonstrated its success in many
studies and clinical applications, has also become a current is-
sue in complete arch implant cases. To date, the standard treat-
ment approach for complete arch implant prosthesis is making
the implant impression with elastomeric impression materials
conventionally, obtaining a master cast and digitizing it with a
laboratory scanner and then performing the digital production
steps.1,2 However, in this conventional impression technique,
many factors result in the inability to transfer the impression
copings in accurate position or their exposure to micro-motions
within the impression. Insufficient interlocking between the
analog-impression coping, dimensional deviations in impres-
sion materials and gypsum can affect the success.3–5 Addition-
ally, the conventional procedures take too long and negatively
affect the comfort of patients.6–8
These limitations of conventional implant impressions were
eliminated by the use of the scan body and the 3-dimensional
(3D) positions of the implants were able to be transferred to
the digital system.9However, in edentulous cases IOS has lim-
ited reference points to continue scanning properly.10 Besides,
scanning the multiple scan bodies can be quite challenging for
the IOS to distinguish these parts from each other and create
an image in the correct position within the arch.11 Although
there have been many studies regarding the accuracy of digital
impressions on complete arch implant cases,12–18 in a current
systematic review published by Papaspyridakos et al19 only
one study comparing both digital and conventional impression
techniques in a jaw containing more than 6 implants has been
detected. Tan et al20 evaluated the accuracy of digital and con-
ventional impression techniques on 8 parallel implants placed
in the maxilla. To the best of the authors’ knowledge, there is
no study in the current literature that compares both impres-
sion techniques in an edentulous mandibula where 8 implants
are placed with angulations.
On the other hand, the features of the IOS and different scan-
ning strategies may also influence the accuracy of digital im-
pressions. It has been reported that different ways of obtaining
3D images, such as creating an image series (Carestream 3500)
or producing 3D structure with a video acquisition system
(Cerec Omnicam, 3Shape Trios 3);21 and different working
principles used by IOS such as active triangulation (Care-
stream 3500),22 optical triangulation and confocal microscopy
(Cerec Omnicam) and confocal microscopy with ultrafast
optical scanning (3Shape Trios 3); may affect the accuracy of
digital impressions at different levels.13 The scanning strategy
can affect the accuracy of digital impressions as well,23 so it is
important to follow the optimal scanning path for each IOS.
The aims of this study are two fold: first is to compare digital
and conventional impression techniques in a clinically unfavor-
able complete arch implant case, and secondly to compare the
accuracy of 3 different IOS with different imaging principles
in terms of trueness and precision. The null hypotheses were
that digital impressions to be made with different IOS provide
data with similar accuracy as conventional technique and the
scanners working with the video-acquisition system (3Shape
Trios 3 and Cerec Omnicam) would be superior to the scanner
working with the image-acquisition system (Carestream 3500),
when both trueness and precision parameters were evaluated.
Material and methods
The complete arch implant model was obtained by placing 8
Dyna Helix DC implants (Dyna Dental Engineering BV, the
Netherlands) (4.2 mmD and 11.5 mmL) in a polyurethane
lower jaw model (Promedicus, Poland). These 8 implants were
placed in the following areas: right second molar, right first
premolar, right canine, right central incisor, left canine, left first
and second premolar, left second molar. Four of them (right
and left second molars, right and left canines) were tilted dis-
tally with 40°, 20°, 15°, 25° angulation, respectively; and the
other implants were placed perpendicular to the occlusal plane.
By placing the implants with these distal angulations, the goal
was to obtain a complete arch model including tilted implants
such as in all-on-4 or all-on-6 cases and reflect the effects of
the angulations on different impressions techniques.
Eight Dyna universal Ti-base abutments (Dyna Dental Engi-
neering BV, the Netherlands) were attached and screwed to the
implants by hand force. Finally, before the digital scans, Dyna
scan bodies (Dyna Dental Engineering BV, the Netherlands),
which were designed to fit onto the Ti-base abutments, were
placed on the model. The reference 3D model was obtained by
scanning the lower jaw model with Activity 885 Mark 2 Scan-
ner (Smart Optics, Bochum, Germany) with accuracy of 6 µm
and it was exported as standard tesselation language (STL) file.
A single operator carried out all digital impressions to en-
sure the operator’s control over the working methods of dif-
ferent scanners. The first 10 trial scans were performed with
each IOS. Between each scanning, the scanner and the opera-
tor were given 5-minute intervals. All impressions were started
with scanning from the right posterior region (right second
molar) and continued towards left posterior region (left sec-
ond molar) on the opposite side of the arch and the scan paths
were determined according to the manufacturer’s instructions
for each IOS.24–26
In the scans carried out with Carestream 3500 (Carestream,
Rochester, NY), the occlusal surfaces of all scan bodies were
first displayed from right second molar to left second molar,
then buccal and finally the lingual surfaces were scanned and
the impression was completed. In Cerec Omnicam (Dentsply
Sirona, Bensheim, Germany), the scans started from the
occlusal surface and then continued by buccal and then the
lingual surface of the same scan body and the imaging was
completed in the left posterior region. For Trios 3 (3-Shape,
Copenhagen, Denmark), the scanning of occlusal surfaces was
performed starting from the right posterior region, followed by
lingual and finally buccal surfaces. The missing areas, partic-
ularly interproximal surfaces, were re-scanned and 10 digital
abutment-level impressions for each IOS were completed.
Finally, a total of 30 scans as determined in power analysis
were obtained and exported as STL files.
For conventional implant impressions, 8 open tray im-
pression copings (Fig 1) were used with 10 individual open
trays prepared to provide uniform thickness of the impression
material. The boundaries of trays were arranged to serve
as stops at 4 points, 2 of them in molar and 2 of them in
2Journal of Prosthodontics 0(2020) 1–8 © 2020 by the American College of Prosthodontists
Albayrak et al Accuracy of Complete Arch Implant Impressions
Figure 1 Complete arch implant model with open tray impression cop-
ings.
Figure 2 (A) Cast model with scan bodies (B) Angulation between scan
bodies.
premolar zone. Kerr polyvinyl siloxane (PVS) tray adhesive
(KaVo Dental GmbH, Bismarckring, Germany) was applied
to the trays 10 minutes before each conventional impression.
Afterwards, the normal set Elite HD +putty soft and Elite
HD +light body (Zhermack SpA, Italy) PVS were placed in
the tray and it was adapted to the lower jaw model by using
one-step impression procedure. The impression material was
allowed to set for 10 minutes (manufacturer’s setting time of
5.30 minutes). Then, analogs were attached to the impression
copings and Zhermack Gingifast Elastic (Zhermack SpA,
Italy) was applied around the copings. For the casts, standard
150 g GC Fujirock type IV dental stone (GC Corporation,
Tokyo, Japan) was used with a liquid-powder ratio of 1:5 and
the minimum separation time of the tray was increased to 2
hours with the cast model specified by the manufacturer, and
the trays were kept at room temperature during the setting.
In order to digitize 10 cast models obtained with conven-
tional technique and standardize the scans with abutment-level
impressions, 8 Ti-base abutments and 8 scan bodies were
placed on the cast models again (Fig 2A, 2B). They were
scanned with Straumann 7 Series laboratory scanner (Strau-
mann Group, Basel, Switzerland) and 3D models were ob-
tained. As a result, a total of 40 different STL files (30 scans
of digital technique, 10 scans of conventional technique) were
obtained to make the comparisons with 3D reference model, in
terms of distance and angular parameters.
In order to carry out measurements on 3D images, all STL
format files were transferred to Rapidform (INUS Technology
Inc., Seoul, South Korea), reverse engineering software. The
reference points were determined on the scan bodies. Two cir-
cles were created at a distance of 0.7 and 3.4 mm from the
Figure 3 (A) Two planes created on scan bodies, (B) The centers of two
circles, (C) The line between the centers of two circles.
triangular pyramid base to center the upper and lower parts of
the scan bodies and the center points of these circles where
the distance measurements would be made were determined
by “point” command (Fig 3A, 3B). Then, the lines connecting
these points were formed to be used in angle measurements
(Fig 3C).
Cartesian (x, y, z) coordinates of the specified points for all
8 scan bodies in a scan were exported from the software in
“.txt” format. The coordinates of the reference points of each
scan body were determined by using midpoint of the centers
of upper and lower circles. First, trueness level which is the
first parameter that constitutes accuracy, was calculated. In this
calculation, both distance and angular deviations between scan
bodies were determined. The distance between two reference
points of P1(x1,y1,z1)andP
2(x2,y2,z2) was calculated by us-
ing the following formula:
|P1P2|=(x1−x2)2+y1−y22+(z1−z2)2
The first scan body (P1) in the right posterior region (right
second molar) was taken as a reference and distance measure-
ments between the reference scan body and the others (P1-P2,
P1-P3, P1-P4, P1-P5, P1-P6, P1-P7, P1-P8) were performed from
the center coordinates, respectively (Fig 4).
The angle measurements were performed with this formula:
l1=x−x1
a1
=y−y1
b1
=z−z1
c1
l2=x−x2
a2
=y−y2
b2
=z−z2
c2
cos ϕ
Journal of Prosthodontics 0(2020) 1–8 © 2020 by the American College of Prosthodontists 3
Accuracy of Complete Arch Implant Impressions Albayrak et al
Figure 4 Measurements bet ween reference point (P1) and the other
scan bodies.
=
→
s1
→
s2
→
s1
|.|→
s2
=a1.a2+b1.b2+c1.c2
a2
1+b2
1+c2
1.a2
2+b2
2+c2
2
The procedure for measuring the angular deviation is based
on the line passing through the center points of the two cir-
cles designated for each scan body. In the above formula-
tion, the lines were found according to the points determined
first (l1,l
2) and their direction vectors (→
s1
,→
s2
). A vector
(→
s) was defined for each scan body, taking into account
the center points of scan body’s drawn circles. In a Carte-
sian coordinate system, a vector with a component “x,y,z”
can be calculated with this formula: (→
s)=ai+bj+ck”. The
letters “a,b,c” are the coefficients that express the direction
magnitude. Consequently, the angle between the reference
scan body (→
s1
) and the other scan body (→
s2
) was defined
in this way and it was calculated with the above formulation
(→
s1
→
s2
,→
s1
→
s3
,→
s1
→
s4
,→
s1
→
s5
,→
s1
→
s6
,→
s1
→
s7
,→
s1
→
s8
).
Precision, the second parameter of accuracy, was determined
through both distance and angular data revealed by impression
groups. First, the averages of the distance and angle measure-
ments between the reference scan body (right second molar)
and the other scan bodies of the 10 impressions belonging to
each impression group were determined. It was then estab-
lished how much of each impression deviated from the mean
value of its own impression group. Thus, distance and angular
precision values were determined by evaluating each impres-
sion within its own group.
The data were analyzed with IBM SPSS Statistics 20.0
Release Notes program. The difference between the mean
values of the variables with normal distribution was analyzed
by one-way ANOVA test; and Tukey multiple comparison
test was used to determine the groups having different dis-
tribution. All statistical analyses were performed after taking
absolute values of the data and 0.05 was used as the level of
significance.
Figure 5 Distance trueness of impression groups.
Figure 6 Angle trueness of impression groups.
Results
The data were obtained from the four groups: Carestream 3500
digital impression group (DC), Cerec Omnicam digital impres-
sion group (DC), 3Shape Trios 3 digital impression group (DT)
and conventional impression group (C). The trueness data were
submitted to a one-way ANOVA to assess the differences be-
tween impression groups as illustrated in Table 1. According
to the one-way ANOVA analysis, there was a significant dif-
ference between the groups in the distance parameter (p<
0.001), but no significant difference was found for the angu-
lar parameter (p=0.074), in terms of trueness. Multiple com-
parisons were made with Tukey post hoc test; DC showed the
lowest distance deviation. While there was no significant dif-
ference between DC (123.06 ±89.83 µm) and DT (209.75 ±
47.07 µm) (p>0.05), the difference between DC and DO
(229.72 ±121.34 µm) was found to be significant (p<0.05);
and no significant difference between DT and DO was ob-
served (p>0.05). C (345.32 ±75.12 µm) was the group that
showed the highest distance deviations significantly among all
groups. (Fig 5). While there was no significant difference be-
tween groups in angular deviations, the amount of deviation in-
creased from DC (0.26° ±0.07°) group as DT (0.33° ±0.30°),
DO (0.53° ±0.42°), and C (0.74° ±0.65°), respectively, sim-
ilar to distance deviations (Fig 6).
One-way ANOVA analysis was performed for precision data
and summarized in Table 2. According to this analysis, signif-
icant differences were found between groups in terms of dis-
tance (p=0.036), however no significant differences were ob-
served in terms of angular precision (p=0.053). In line with
4Journal of Prosthodontics 0(2020) 1–8 © 2020 by the American College of Prosthodontists
Albayrak et al Accuracy of Complete Arch Implant Impressions
Ta b l e 1 One-way ANOVA results of trueness for distance and angle parameters
Parameters Sum of squares df Mean square F Sig.
Distance Between Groups 251076.567 3 83692.189 10.922 0.000
Within Groups 275860.313 36 7662.786
Total 526936.881 39
Angle Between Groups 1.398 3 0.466 2.507 0.074
Within Groups 6.692 36 0.186
Total 8.090 39
Ta b l e 2 One-way ANOVA results of precision for distance and angle parameters
Parameters Sum of squares df Mean square F Sig.
Distance Between Groups 18815.700 3 6271.900 3.163 0.036
Within Groups 71387.709 36 1982.992
Total 90203.408 39
Angle Between Groups 0.574 3 0.191 2.822 0.053
Within Groups 2.442 36 0.068
To t al 3 .0 17 3 9
Ta b l e 3 Tukey post hoc tests used to evaluate the differences between
impression groups for distance precision
Group N 1 2
DT 10 35.55 ±28.46
C 10 66.97 ±36.69 66.97 ±36.69
DC 10 80.43 ±29.69 80.43 ±29.69
DO 10 94.06 ±69.96
Sig. 0.128 0.532
Ta b l e 4 Tukey post hoc tests used to evaluate the differences between
impression groups for angular precision
Group N 1
DC 10 0.19° ±0.11°
DT 10 0.22° ±0.19°
DO 10 0.30° ±0.28°
C 10 0.50° ±0.38°
Sig. 0.059
distance precision, DT (35.55 ±28.46 µm) group was found to
provide the most consistent data. The impressions of C (66.97
±36.69 µm), DC (80.43 ±29.69 µm), and DO (94.06 ±69.96
µm) groups, respectively, provided data in a wider spectrum
within their own impressions. After the Tukey post hoc test for
difference analysis, only DT and DO impression groups dif-
fered significantly (p<0.05) (Table 3). Finally, it was observed
that the angular precision increased from DC (0.19° ±0.11°)
to DT (0.22° ±0.19°), DO (0.30° ±0.28°) and C (0.50° ±
0.38°), respectively; however, there was no significant differ-
ence between the impression groups as illustrated in Table 4
(p>0.05).
Discussion
The present article is a comparative in vitro study between
3 different IOS and conventional impression technique con-
ducted on a lower jaw model with 8 implants. Based on the
results of this study, the null hypothesis that the digital impres-
sions would provide accuracy similar to the conventional tech-
nique used as a standard in complete arch implant cases has
been rejected. The open tray impression technique showed the
highest deviations in distance and angular trueness, and also
angular precision. Digital impression groups performed better
in terms of accuracy than conventional technique.
The positional, rotational and angular displacements that
may occur during the transfer of impression copings from
mouth to tray in complete arch implant cases may pose an
important problem in terms of conventional impression tech-
nique. As a result of a study carried out on a model with 8
implants having 0°, 15°, and 25° angulations by Mpikos et al27,
it was stated that the deviations increased significantly with the
high angles, especially for the implants with 25° angulation.
In 2018, Alikhasi et al12 compared the accuracy of nonsplinted
open tray and closed tray techniques by using PVS and the
digital impressions made with a 3Shape Trios scanner. The
impressions were made from a total of 4 implants, two straight
and two 45° distally tilted in an edentulous maxillary model.
The results of the comparison, in parallel with our study,
found that the digital technique was the most accurate group
with 188 µm. Accuracy of open tray technique was 280 µm
and closed tray technique showed the highest deviation with
885 µm.
One possible reason why the conventional impression group
was less accurate than digital impression groups in the present
study may be the use of nonsplinted open tray technique.
In a systematic review by Papaspyridakos et al28 regarding
conventional implant impressions, it was stated that splinting
Journal of Prosthodontics 0(2020) 1–8 © 2020 by the American College of Prosthodontists 5
Accuracy of Complete Arch Implant Impressions Albayrak et al
significantly increases impression accuracy especially in
complete arch implant cases. In order to increase the impres-
sion accuracy by splinting the copings, preangled multi-unit
abutments are required; however these abutments can correct
the angle discrepancies in a range of 15° to 30°.29 Therefore,
the use of these standard abutments in higher angulations such
as 40° may not provide sufficient parallelism, so customized
abutment production may be more useful in such nonideal
cases.
On the other hand, when the intraoral scanners used in this
study were evaluated within themselves the best trueness re-
sults were obtained with Carestream 3500 scanner in both an-
gle and distance measurements. The deviations in the impres-
sions made with Cerec Omnicam and 3Shape Trios 3 were
higher. In the evaluation of precision of IOS, it is seen that
Trios 3 can obtain high consistency data in both distance and
angular terms and Carestream provided the lowest deviation in
angular precision. According to these results, the null hypoth-
esis that Cerec Omnicam and 3Shape Trios 3 scanners operat-
ing with video-acquisition system would scan the model with
higher accuracy than Carestream 3500 that works with image-
acquisiton, was rejected.
Accuracy of digital impressions can be influenced by the
working principles, data processing algorithm, power appli-
cation methods, scanning strategies and learning curves of
IOS.30,31 The IOS used in this study operate with different
principles such as active triangulation, confocal microscopy
and ultrafast optical scanning; these methods may affect find-
ing the reference points to continue scanning and establishing
3D structure. In particular for digital implant impressions, it
is difficult to find the reference point for IOS due to the use
of scan bodies with the same shape and form, and it may not
be possible to accurately match the scanned area to the pre-
vious images.9In the present study, especially in the regions
between right second molar and right first premolar and also
right central incisor and left canine where the body distances
are long, the scanners often lost the reference point during the
impression and it was difficult to keep scanning. In these body
regions, it is thought that the software of IOS might combine
the images improperly and this situation may affect the accu-
racy. This loss of reference point was frequently observed in
the scans performed with Carestream 3500 and the scan was
continued after the required calibration. The fact that the DC
group obtained high-accuracy data suggests that this situation
may not directly affect accuracy.
In the research conducted by Renne et al32 accuracy of 6 IOS
and 1 lab scanner were compared and it was stated that within
the IOS, Carestream 3500 and iTero provided the best accu-
racy, but were also the slowest . The IOS that performed most
accurately in this study, Carestream 3500, was also the slow-
est. However, it should be considered that this feature may be
a disadvantage in scanning intraorally.
As a result of research regarding digital implant impres-
sions, it was stated that the increase in the number of im-
plants and the body distances may affect the accuracy of dig-
ital impression negatively. Imburgia et al13 and Mangano et
al,33 compared 4 different intraoral scanners’ performances on
both partial and total edentulous jaw models; they found that
all IOS yielded more accurate data in short distances and par-
tial edentulous models. Besides, in parallel with the present
study, Carestream 3500 and Carestream 3600 scanners gave
the best results in those studies, compared to Cerec Omni-
cam and 3Shape Trios. Kim et al34 inserted 6 implants to the
mandibula with partial edentulism and placed one of the im-
plants in the left second molar region mesially and the other
distally with angle of 30°. At the end of the comparison be-
tween 5 IOS (Cerec Omnicam, Carestream 3600, Medit i500,
iTero Element, and 3Shape Trios 3), it was stated that Medit
i500 and Trios 3 yielded the best data and the accuracy of the
impressions for each scanner decreased as the scanning area
expanded.
The measurement technique of the distance and angles be-
tween the scan bodies and the selection of the reference point
for the measurements can also affect the results. In many stud-
ies comparing various implant impression techniques in terms
of accuracy, different measurement methods have been used.
Some researchers13,15,17 calculated the accuracies of different
impression techniques by superimposing 3D models to the ref-
erence model and determining the deviations from the original
coordinates of each scan body. However, there may be some
difference during the superimposing of the images and this dif-
ference may affect the result. For this reason, Moura et al18 and
Gimenez et al,35 in their studies performed on complete arch
implant cases, selected the implants in the most posterior re-
gion as a reference and measured the distances between these
implants and other implants; then they determined the devia-
tion from the reference model. In this present study, this tech-
nique was preferred and the scan body in the right posterior
region was accepted as the reference and measurements of the
accuracy of the complete arch implant case were completed by
using it.
Due to the fact that our study was carried out in vitro, some
patient-related factors were eliminated. It is thought that fac-
tors such as saliva, transparency and the amount of reflection of
light from the oral tissues, patient movements and inability of
the scanner tip to reach the posterior regions, especially in pa-
tients with limited mouth opening, may affect the accuracy of
digital impression.36 Additionally, differences in the mucosal
surface due to jaw movements may affect the scanner’s abil-
ity to locate the reference point in order to continue imaging,
which can lead to various problems during software combin-
ing the acquired images.11 In order to consolidate these results
or to adjust them for clinical life, digital and conventional im-
plant impressions should be compared in in vivo studies. Since
the reference optical scanners cannot be used intraorally, the
compatibility of the implant-supported prostheses and screws
produced by both techniques should be tested with abutments
by methods such as Sheffield testing, and microscopic and/or
radiographic evaluation. Comparison of long-term results af-
ter the application of these prostheses to the patients would be
very useful for selecting case-based impression techniques. In
further studies, it can also be investigated how the accuracy of
the impressions is affected by using multiple scan bodies with
different shapes.
6Journal of Prosthodontics 0(2020) 1–8 © 2020 by the American College of Prosthodontists
Albayrak et al Accuracy of Complete Arch Implant Impressions
Conclusion
In a clinically unfavorable complete arch implant case with
high angulations and asymmetric distribution, digital impres-
sion methods achieved superior results in both distance and
angular parameter comparted to a conventional method using
nonsplinted open tray impression technique. Different acqui-
sition methods and working principles of IOS can also affect
the accuracy. When trueness and precision were evaluated to-
gether, Carestream 3500 and 3Shape Trios 3 obtained more ac-
curate data compared to Cerec Omnicam.
Acknowledgments
The authors thank Dyna Dental Company for supplying all im-
plant components, Zhermack Dental and GC Corporation for
their support in terms of impression and cast materials, and
Ömer Akbulut for his assistance with statistical analysis.
References
1. Cheng CW, Chien CH, Chen CJ, et al: Complete-mouth implant
rehabilitation with modified monolithic zirconia
implant-supported fixed dental prostheses and an
immediate-loading protocol: a clinical report. J Prosthet Dent
2013;109:347-352
2. Rhee YK, Huh YH, Cho LR, et al: Comparison of intraoral
scanning and conventional impression techniques using
3-dimensional superimposition. J Adv Prosthodont
2015;7:460-467
3. Sorrentino R, Gherlone EF, Calesini G, et al: Effect of implant
angulation, connection length, and impression material on the
dimensional accuracy of implant impressions: an in vitro
comparative study. Clin Implant Dent Relat Res 2010;12:63-76
4. Lee H, So JS, Hochstedler JL, et al: The accuracy of implant
impressions: a systematic review. J Prosthet Dent
2008;100:285-291
5. Kim S, Nicholls JI, Han CH, et al: Displacement of implant
components from impressions to definitive casts. Int J Oral
Maxillofac Implants 2006;21:747-755
6. Gjelvold B, Chrcanovic BR, Korduner EK, et al: Intraoral digital
impression technique compared to conventional impression
technique. A randomized clinical trial. J Prosthodont.
2016;25:282-287
7. Mangano F, Gandolfi A, Luongo G, et al: Intraoral scanners in
dentistry: a review of the current literature. BMC Oral Health
2017;17:149
8. Wismeijer D, Mans R, van Genuchten M, et al: Patients’
preferences when comparing analogue implant impressions
using a polyether impression material versus digital impressions
(intraoral scan) of dental implants. Clin Oral Implants Res
2014;25:1113-1118
9. Andriessen FS, Rijkens DR, van der Meer WJ, et al:
Applicability and accuracy of an intraoral scanner for scanning
multiple implants in edentulous mandibles: a pilot study. J
Prosthet Dent 2014;111:186-194
10. Holst S, Persson A, Wichmann M, et al: Digitizing implant
position locators on master casts: comparison of a noncontact
scanner and a contact-probe scanner. Int J Oral Maxillofac
Implants 2012;27:29-35
11. Flügge T, Att W, Metzger M, et al: A novel method to evaluate
precision of optical implant impressions with commercial scan
bodies—an experimental approach. J Prosthodont
2017;26:34-41
12. Alikhasi M, Siadat H, Nasirpour A, et al: Three-dimensional
accuracy of digital impression versus conventional method:
effect of implant angulation and connection type. Int J Dent
2018;2018:1-9
13. Imburgia M, Logozzo S, Hauschild U, et al: Accuracy of four
intraoral scanners in oral implantology: a comparative in vitro
study. BMC Oral Health 2017;17:92
14. Ribeiro P, Herrero-Climent M, Díaz-Castro C, et al: Accuracy
of implant casts generated with conventional and digital
impressions—an in vitro study. Int J Environ Res Public Health
2018;15:1599
15. Amin S, Weber HP, Finkelman M, et al: Digital vs. conventional
full-arch implant impressions: a comparative study. Clin Oral
Implants Res 2017;28:1360-1367
16. Vandeweghe S, Vervack V, Dierens M, et al: Accuracy of digital
impressions of multiple dental implants: an in vitro study. Clin
Oral Implants Res 2017;28:648-653
17. Papaspyridakos P, Gallucci GO, Chen CJ, et al: Digital versus
conventional implant impressions for edentulous patients:
accuracy outcomes. Clin Oral Implants Res 2016;27:465-472
18. Moura RV, Kojima AN, Saraceni CHC, et al: Evaluation of the
accuracy of conventional and digital impression techniques for
implant restorations. J Prosthodont 2019;28:530-535
19. Papaspyridakos P, Vazouras K, Chen YW, etal: Digital vs
conventional implant impressions: a systematic review and
meta-analysis. J Prosthodont. 2020;
https://doi.org/10.1111/jopr.13211.
20. Tan MY, Yee SHX, Wong KM, et al: Comparison of
three-dimensional accuracy of digital and conventional implant
impressions: effect of interimplant distance in an edentulous
arch. Int J Oral Maxillofac Implants 2019;34:366-380
21. Nedelcu R, Olsson P, Nyström I, et al: Finish line distinctness
and accuracy in 7 intraoral scanners versus conventional
impression: an in vitro descriptive comparison. BMC Oral
Health 2018;18:27
22. De Angelis F, Pignatiello G, Brauner E, et al: Accuracy and
precision of an intraoral scanner in complex prosthetic
rehabilitations: an in vitro study. J Int Dent 2017;10:52-58
23. Passos L, Meiga S, Brigagão V, et al: Impact of different
scanning strategies on the accuracy of two current intraoral
scanning systems in complete-arch impressions: an in vitro
study. Int J Comput Dent 2019;22:307-319
24. CS 3500 Real-Time Full Arch Scan I Streamhealth Dental:
https://www.youtube.com/watch?v =sMEykCIrBkI&t =31s
Accessed 5/18/2020
25. Tutorial: CEREC Omnicam Scanning Technique:
https://www.youtube.com/watch?v =E5hzbRNK7pk&t =95s
Accessed 5/18/2020
26. 3Shape TRIOS Scan Strategy - Full Arch:
https://www.youtube.com/watch?v =M_KbWcCianY&t =
126s. Accessed 5/18/2020
27. Mpikos P, Kafantaris N, Tortopidis D, et al: The effect of
impression technique and implant angulation on the impression
accuracy of external- and internal-connection implants. Int J
Oral Maxillofac Implants 2012;27:1422-1428
28. Papaspyridakos P, Chen CJ, Gallucci GO, et al: Accuracy of
implant impressions for partially and completely edentulous
patients: a systematic review. Int J Oral Maxillofac Implants
2014;29:836-845
29. Cavallaro Jr J, Greenstein G: Angled implant abutments: a
practical application of available knowledge. J Am Dent Assoc
2011;142:150-158
Journal of Prosthodontics 0(2020) 1–8 © 2020 by the American College of Prosthodontists 7
Accuracy of Complete Arch Implant Impressions Albayrak et al
30. Park JM: Comparative analysis on reproducibility among 5
intraoral scanners: sectional analysis according to restoration
type and preparation outline form. J Adv Prosthodont
2016;8:354-362
31. Müller P, Ender A, Joda T, et al: Impact of digital intraoral scan
strategies on the impression accuracy using the TRIOS Pod
scanner. Quintessence Int 2016;47:343-349
32. Renne W, Ludlow M, Fryml J, et al: Evaluation of the accuracy
of 7 digital scanners: an in vitro analysis based on 3-dimensional
comparisons. J Prosthet Dent 2017;118:36-42
33. Mangano FG, Veronesi G, Hauschild U, et al: Trueness and
precision of four intraoral scanners in oral implantology: a
comparative in vitro study. PLoS One 2016;11(9),
https://doi.org/10.1371/journal.pone.0163107
34. Kim RJY, Benic GI, Park JM: Trueness of digital intraoral
impression in reproducing multiple implant position. PLoS One
2019;14(11), https://doi.org/10.1371/journal.pone.
0222070
35. Giménez B, Özcan M, Martinez-Rus F, et al: Accuracy of a
digital impression system based on active wavefront sampling
technology for implants considering operator experience,
implant angulation, and depth. Clin Implant Dent Relat Res
2015;17:54-64
36. Chia VA, Esguerra RJ, Teoh KH, et al: in vitro three-dimensional
accuracy of digital implant impressions: the effect of implant
angulation. Int J Oral Maxillofac Implants 2017;32:313-
321
8Journal of Prosthodontics 0(2020) 1–8 © 2020 by the American College of Prosthodontists
