UNIVERSIDADE ESTADUAL PAULISTA
“JÚLIO DE MESQUITA FILHO”
Instituto de Ciência e Tecnologia
Campus de São José dos Campos
ORIGINAL ARTICLE DOI: https://doi.org/10.4322/bds.2024.e4366
1
Braz Dent Sci 2024 Apr/Jun;27 (2): e4366
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
Dimensional accuracy of provisional complete crown made by the
3D printing method
Acuidade dimensional de coroas totais provisórias confeccionadas pelo método de impressão 3D
Ellen Randoli PEREIRA1 , Luigi Giovani Bernardo SICHI1 , Marcelle Simões COELHO1 , Gabriel Cirone LOPES1 ,
Rodrigo Máximo de ARAÚJO1
1 - Universidade Estadual Paulista “Júlio Mesquita Filho” - UNESP, Instituto de Ciência e Tecnologia, Departamento de Materiais
Odontológicos e Prótese, Campus de São José dos Campos, SP, Brazil
How to cite: Pereira ER, Sichi LGB, Coelho MS, Lopes GC, Araújo RM. Dimensional accuracy of provisional complete crown made by the
3D printing method case. Braz Dent Sci. 2024;27(2):e4366. https://doi.org/10.4322/bds.2024.e4366
ABSTRACT
Objective: This study evaluated the dimensional accuracy of provisional complete crowns printed with photopolymerizable
resin using an LCD-type 3D printer through optical metrology, varying the printing angle and the number of complete
crowns printed at once on a single-build platform. Material and Methods: The complete crowns were printed with
temporary crown resin, A2 temporary (Wilcos do Brasil), divided into four groups with n=12: Group A - 3 complete
crowns positioned at 150° on the x-axis; Group B - 4 complete crowns positioned at 150° on the x-axis; Group C - 3
complete crowns positioned at 180° on the x-axis; and Group D - 4 complete crowns positioned at 180° on the x-axis.
Dimensional accuracy was assessed by overlaying images in the Gom Inspect measurement software, where the STL
of each complete crown was aligned and compared to the master model. For statistical analysis, one-way ANOVA
and Shapiro-Wilk tests were used. Results:Nosignicantstatisticaldifferencewasobservedbetweenthedifferent
angles, or the number of complete crowns printed at once. Conclusion: Based on dimensional accuracy, the printing
ofprovisionalcompletecrownswithanLCD-type3Dprintershowsnosignicantstatisticaldifferencewitheitherthe
150 or 180-degree angle variations, and there is also no difference when printing 3 or 4 complete crowns at once.
KEYWORDS
CAD-CAM; Dental crowns; Dental prosthesis; Prosthodontics; 3D printing.
RESUMO
Objetivo: Este estudo avaliou a acuidade dimensional de coroas totais provisórias impressas com resina fotopolimerizável
por uma impressora 3D tipo LCD por meio da metrologia optica, variando angulação de impressão e número de coroas
impressas por vez em uma única plataforma de construção. Material e Métodos: As coroas foram impressas com resina
para coroa provisória, A2 temporário (Wilcos do Brasil), divididas em quatro grupos com n=12: Grupo A - 3 coroas
posicionadas a 150° no eixo x; Grupo B - 4 coroas posicionadas a 150° no eixo x; Grupo C - 3 coroas posicionadas a
180° no eixo x e Grupo D - 4 coroas posicionadas a 180° no eixo x. A acuidade dimensional foi feita com a sobreposição
de imagens no programa de aferição Gom Inspect, em que o STL de cada coroa foi alinhado e comparado ao modelo
mestre. Para análise estatística, foram utilizados os testes ANOVA um fator e Shapiro-Wilk. Resultados: Não foi
vericadadiferençaestatísticasignicativaentreasdiferentesangulaçõesouquantitadadedecoroasimpressasem
uma única vez. Conclusão: Com base na acuidade dimensional, a impressão de coroas provisórias com impressora
3DtipoLCDnãoapresentadiferençaestatísticasignicativecomnenhumadasduasvariaçõesangulaçãode150ou
180 graus e não há diferença também ao fazer a impressão de 3 ou 4 coroas de uma única vez.
PALAVRAS-CHAVE
CAD-CAM; Coroa dental; Prótese dental; Odontologia protética; Impressão 3D.
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Braz Dent Sci 2024 Apr/Jun;27 (2): e4366
Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
INTRODUCTION
The making of high-precision dental crowns
became possible in dentistry through the wax
elimination technique, introduced by Taggart in
1907 [1], however, because it depends on a high
level of skill in casting by the dental prosthesis
technician, this technique is subject to a multitude
of errors during obtaining the piece.
The introduction of the automated CAD/CAM
system, computer-aided design/computer-aided
manufacturing (GPT-9 2017) in 1970 aimed to
simplify the manufacturing processes in dentistry,
reducing the dependence on the manual skill of
the technician, reducing the chances of errors
during obtaining the part [2] reducing clinical
and laboratory time, increasing productivity
and ensuring quality of the final part with
predictability in the treatment, without changing
patients’ perception of satisfaction [3,4]. CAD/
CAM technology facilitates the daily life of the
clinician, performing direct teeth scans of a patient
using an intraoral scanner is quicker and facilitates
simple digital bite registration, for example, in
the manufacture of provisional complete crowns,
in which there is a need for gingival conditioning
by adding material to the provisional crowns [5].
This increase can be made by producing temporary
complete crowns with a progressive increase in
height so that these cases can be rehabilitated faster
than the conventional method [6]. For example,
we can also mention the manufacture of prostheses
on unitary provisional implants in cases performed
with guided surgery for immediate dental implant
installation, in which it is possible to plan the
exact position of the dental implant through
virtual space analysis and, consequently, this
information allows the provisional prosthesis to
be made before the implant installation surgery.
In the conventional method, it is necessary to
perform the surgery for implant installation before
preparing the provisional prosthesis. In summary,
the integration of CAD/CAM for designing dental
prostheses, facilitated by the development of rapid
prototyping(RP),allowstheefcientproductionof
frameworks. This approach offers advantages such
aspreciset,simpliedfabrication,reducedcosts,
shortened treatment times, and the potential for
mass production, thereby saving materials, time,
and effort [7].
The elements of the CAD/CAM system are
divided into (1) acquisition of informative data,
which consists of image capture through scanning
andobtainingthedigitalle;(2)design(CAD),
in which the data obtained in the previous phase
in design software, or digital design program, will
beprocessedtoplanthedesignofthedenitive
prosthesis; and (3) manufacturing process of
the prosthesis (CAM), at this stage, automatic
machines follow information from a digital
design program to manufacture the project of
the previous phase [2].
Within the part manufacturing process
(CAM) is included, the means of subtractive
fabrication or CNC (computer numerical control)
(GPT-9 2017), which uses milling machines,
and also additive manufacturing, which uses 3D
printers.
3D printing was classified in 2017 by
Tahayeri et al. [6] according to their manufacturing
process, which divides the methods into
4 categories: (1) Fused-deposition modeling, (2)
Inkjet printing, (3) Selective laser sintering and
(4) lithographic printing. Light or lithographic
printing uses photopolymers kept in a vat; direct
exposure of the polymer to light builds the 3D
object as the sample support moves up or down.
Inserted in light printing, are printers by
stereolithography (SLA), printers by digital
light processing (DLP) and printers by liquid
crystal display (LCD), which are the most used
in dentistry.
The applications of 3D printing in dentistry
are variable, such as the making of surgical
guides, models, occlusal splints, oral and
maxillofacialprostheses,xedpartialdentures,
removable partial dentures, complete dentures
and provisional prostheses. 3D printing allows
many customized products to be produced at
relatively low costs [8].
3D printing of complex geometries, such
as complete crowns, becomes more precise
by adjusting the printing parameters, which
vary according to the object to be built and
the material made. Processing by 3D printing
goes through the curing process, in which the
construction of the layers is done, and the process
ofpost-curing,inwhichthenalpolymerization
of the object is done. The printing angle is one of
the parameters that, when appropriate, increases
thevolumetricaccuracyofthenalresult,and
reduces printing time and production cost. In the
processing, the printing angle makes it possible
to support the material during its manufacture.
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Braz Dent Sci 2024 Apr/Jun;27 (2): e4366
Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
This support, similar to the sprue in the wax
elimination technique, is made through supports
of the material itself that will be made. The ideal
is that as few supports as possible be placed, to
reduce the polymerization contraction of the
material during the manufacture, before the post-
curing process. In addition, a smaller amount of
support reduces the amount of material used.
In the post-curing process, these supports will also
undergo polymerization contraction, if they are
in excessive quantity they can interfere with the
volumetric accuracy of the result. The programs
used for the 3D printing processing step, called
slicing software, offer the operator the automatic
option to make these supports or the operator’s
option to manually insert each support, varying
in the number of supports, position and diameter
of each support. In the literature, the proposed
angles for 3D printing concerning the X-axis
of the slicing software platform are 150° and
180° for complete crowns. However, there is no
standardization related to the anatomy of the
object, so more studies should be conducted for
a clinically acceptable adaptation [9].
Another relevant parameter is the amount of
high-complexity objects that can be made in the
same print, that is, the reproducibility of printed
materials. The precision of the final piece is
inuencedbythelightintensitythatthematerial
receives on the construction platform [10].
Although there is research that considers
the parameters of angle of inclination and
reproducibility in 3D prints, the lack of
standardization of these parameters is still a
recurring problem and there are no studies that
relate these two variables together. Inappropriate
printing angles can result in a lack of material and
failures in the morphology of the object.
The reproducibility and angulation of
printing complete crowns can be tested using
opticalmetrology,morespecicallydimensional
accuracy, because it evaluates in a three-
dimensional way a complex geometry, being
relatively simpler and faster than conventional
techniques such as the silicone replica technique
or the technique of direct visualization in
microscopy. About the silicone replica, optical
metrology allows evaluation without the
destruction of the part, in addition, it is not
necessarytomakecutsinaxespre-denedbythe
work, reducing the possibilities of manipulation
errors, which can be the result of the choice of
favorable plans for evaluation. Concerning the
technique of direct visualization in microscopy,
optical metrology makes it easier to obtain the
measurement points, since they are precisely
denedbythesoftware[10].
Thus, to analyze the dimensional accuracy
of provisional complete crowns printed, the
present study made this analysis utilizing optical
metrology, varying printing angles and the
number of complete crowns printed at the same
time on a single construction platform, to indicate
an appropriate methodology for 3D printing of
provisional complete crowns, since there is still
no standard established by the literature.
MATERIAL AND METHODS
In a resin mannequin tooth (MOM© -
Manequins Odontológicos Marília, Marília, São
Paulo, Brazil), corresponding to the dimensions of
arstrightuppermolar,apreparewasmadefora
unitary complete crown with a bevel end, occlusal
reduction of 1.5 mm and convergence angle of six
to ten degrees, about the long axis of the tooth,
for the manufacture of the master model. For the
preparation, diamond tips mounted in high-speed
handpiece under constant irrigation were used,
respecting the axial inclinations - spherical tip
for wear orientation grooves, thin conical-trunk
tip for removal of interproximal contacts, ogival
end tip for axial and occlusal wear and rounded
end tip for delimitation of the marginal groove.
Thenishwasmadewiththesamediamondtips
mounted on a micromotor and low-speed drill,
to remove irregularities that may have remained
in the region of the cervical termination and
roundthepreparation.Theaspectofthenalized
preparation is shown in Figure 1.
Figure 1 - Preparation of complete crown for making the master model.
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Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
The image acquisition was made by scanning
the master model with a contact scanner
CS3700 (Carestream Dental LLC, Atlanta, USA),
toobtainadigitalle(Figure 2). After scanning,
the image acquisition is transferred to the digital
language in the form of a mesh in STL (Standard
Triangle Language) format, which is a digital
meshbuiltbytriangles.Thescanninglewas
exported to the design software EXOCAD Dental
DB 2.4 Plovid 7290 (Exocad GmbH©, Darmstadt,
Germany), in which the design of the complete
crown was made (Figure 3).
Next,thedesignlewasexportedtothe
W3D Printer Slicer V1.0 printing program (Wilcos
do Brasil Indústria e Comércio Ltda, Petrópolis,
Rio de Janeiro, Brazil).
The W3D Printer Slicer V1.0 (Wilcos do
Brasil Indústria e Comércio Ltda, Petrópolis,
Rio de Janeiro, Brazil) program features a
support table that makes it possible to plan
the print. The printing parameters, described
in Figure 4, include a print layer thickness of
0.03mm and an exposure time of 12s per layer.
These parameters are important because they
inuencetheaccuracyoftheobjecttobecreated.
The groups were divided as follows: Group A -
3 crowns positioned at 150° on the x-axis; Group
B - 4 crowns positioned at 150° on the x-axis;
Group C - 3 crowns positioned at 180° on the
x-axis and Group D - 4 crowns positioned at 180°
on the x-axis, with a sample number equal to
12. To reach the sample number, groups A and
C were printed four times and groups B and D
were printed three times (Figure 5).
The printing of the complete crowns was
made of photopolymerizable resin Resilab 3d
Premium Temporary color A2 (Wilcos do Brasil
Indústria e Comércio Ltda, Petrópolis, RJ, Brazil)
(Figure 6A) in a SLA type printer W3D Print
(Wilcos do Brasil Indústria e Comércio Ltda,
Petrópolis, RJ, Brazil) (Figure 6B).
Figure 2 - Scanner CS 3700, Carestream.
Figure 3 - Design of the complete crown in Exocad software.
Figure 4 - Print parameters in W3D Printer Slicer V1.0 software.
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Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
The prints were removed from the 3D
printer and washed with isopropyl alcohol, then
submerged in an ultrasonic tub Anycubic Wash &
Cure Machine 2.0 (Anycubic©, Shenzhen, China),
(Figure 6C) with isopropyl alcohol for 5 minutes.
The post-cure Anycubic Wash & Cure Machine
2.0 (Anycubic©, Shenzhen, China) was done
for 45 minutes, according to the manufacturer’s
instructions. The complete crowns were detached
from the printing table with clinical tweezers,
theexcessmaterialwasremovedandnished
and polished the outside of the complete crown
was with polishing drills mounted on a straight
piece. All processes were done following the
manufacturer’s recommendations, without
compromising the internal or marginal area.
All printed complete crowns were scanned
andtheSTLleobtainedwasexportedtothe
GOM Inspect inspection program (GOM©
Braunschweig, Germany) for dimensional
accuracy analysis by means of overlapping images,
a procedure that allows you to evaluate point-to-
point any discrepancy in the characteristics of the
completecrown.Intheprogram,theCADleis
the reference (the design of the complete crown
madebythedesignsoftware).MESHisthele
of the scanned complete crown. Both CAD and
MESH were imported into the program in STL
format and first underwent a pre-alignment,
basedontheglobalbest-talgorithm,withan
additional point of aid in the center of the pulp
wallofthecompletecrown.IntheMESHle,
the internal region of the crown, which includes
marginal, axial, and occlusal parts, was selected
for the main alignment, best-fit-local, and
maximum search distance at 1mm (Figure 7A, B,
C). With the meshes properly aligned, the surface
comparison between them was performed, with
a maximum search distance of 1mm and closed
color legend for color histogram, at 120 µm
(Figure 7D).
Figure 5 - Print of the software print table, representing each group. Group A, with 3 complete crowns positioned at 150° on the x-axis, totaling
4 impressions to make 12 complete crowns: group B, with 4 complete crowns positioned at 150° on the x-axis, totaling 3 impressions to make
12 complete crowns; group C with 3 complete crowns positioned at 180° on the x-axis, totaling 4 impressions to make 12 complete crowns and
group D, with 3 complete crowns positioned at 180° on the x-axis, totaling 3 impressions to make 12 complete crowns).
Figure 6 - Representation of materials and methods. (A) Resin resilab 3d Premium Temporary color A2 from Wilcos; (B) Wilcos W3D Print LCD
Printer; (C) Utrasonic Cuba Anycubic Wash & Cure Machine 2.0.
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Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
Deviation labels were distributed in the
internal area of each complete crown, totaling
129 points of deviation, 1mm equidistant
(Figure 8). To ascertain the clinical acceptability
of the complete crowns, the deviation values
were compared to the reference values for
marginal adaptation suggested by the literature
≤ 1 µm McLean and von Fraunhofer, 1971 [11].
The values of these deviations were exported
to Excel software (Microsoft©, 30 Washington,
USA) to calculate the root mean square (RMS),
or effective value, of the 129 measured deviation
labels of each of the complete crowns.
The mean RMS values were evaluated in
the Bioestat 5.0 statistical program. The results
of the deviations were used for the root mean
square (RMS) of each complete crown, in
which the square root of the arithmetic mean
of the squares of the deviations of each crown
will be made. As for normality, the distribution
of the data was analyzed using the Dwass-
Steel-Critchlow-Fligner and Shapiro-Wilk tests.
The ANOVA one-factor test was used to compare
average values. The significance level was
established at P ≤0.05anda95%condence
interval. To ascertain the clinical acceptability of
complete crowns, reference values for marginal
adaptation suggested by the literature ≤ 120 µm
were used [11].
A comparison of the volume deviations in
mm3 was made between the design of the complete
crown made in the EXOCAD Dental DB 2.4 Plovid
7290 (Exocad GmbH©, Darmstadt, Germany)
and the scanning of each printed complete
crown, using the Gom Inspect program (GOM©
Braunschweig, Germany). Initially, the volume
of the design complete crown (325.45 mm3) was
calculated; this value was used as a reference
Figure 7 - Alignment of STL files. (A) CAD file; (B) the Mesh file; (C) alignment between the two files; (D) Surface comparison with closed color
legend for color histogram, at 120 µm.
Figure 8 - Visualization of the distribution of equidistant deviation
labels.
to compare the volume deviations between the
design (nominal value) and the printed complete
crowns (current value) (Figure 9).
Since there is no methodology for 3D printing
of provisional complete crowns supported by the
literature to date, a pilot study has been made to
calibrate the main 3D printing parameters used in
this study, which are: the thickness of the printing
layer (layer thickness); normal exposure time;
shutdown time (off time); lower exposure time
(bottom exposure time) and amount of lower
layers (bottom layers). These parameters were
used to establish the most appropriate printing
angle and the ideal quantity of complete crowns
per print. The density and quantity of supports
alsoinuencedtheaccuracyoftheprinting.
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Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
The thickness of the layer is related to
the precision or final resolution of the piece,
in an inversely proportional way, because the
smaller the thickness of the layer, the greater
the resolution, due to the formation of a greater
number of layers to compose the final piece,
whichwillpresentwell-deneddetailsandhigh
surface smoothness. In the same way, the bigger
thethicknessofthelayers,thelowerthenal
resolutionofthenalpiece.Thenormalexposure
time is related to the thickness of the layer; the
thicker, the longer the exposure time of the layer
tolight.Thisparameterisdenedaccordingtothe
thickness of each layer, the complexity of model
details, and the resin material. The shutdown
time is the interval that UV light is turned off
between the formation of each layer. The lower
exposure time is the time of exposure to light of
therstlayersformed,whicharecalledlower
layers or “bottom”. These layers ensure the
adhesion of the resin to the platform and, to
perform their function, they must receive a large
dose of energy in their formation. To receive the
necessary amount of light, the lower layers must
be exposed to light for at least 30s. The number
of lower layers is also related to the adhesion of
the resin to the 3D printer platform.
Initially, a print of 9 complete crowns
was made: 3 complete crowns positioned at
90 degrees concerning the X-axis, 3 complete
crowns positioned at 180 degrees concerning
the X-axis, and 3 complete crowns positioned at
150 degrees concerning the X-axis (Figure 10).
The following printing parameters were used:
print layer thickness 0.05mm; normal exposure
time 60s; shutdown time 1s; lower exposure
time 60s, 8 lower layers, and light density for the
construction supports. The 3D printer was unable
to print the complete crowns properly with this
conguration,because,attheendofprinting,
the material was adhered to the platform and
at the bottom of the resin tank, indicating that
therewasinsufcientlightexposure.Asecond
impression was made with these same settings,
changing the exposure time to 12s and support
density to medium. This time, there was the
3D construction of the complete crowns, but
there was a visible misadaptation of the crown
to the master model, mainly of the complete
crowns printed at 90 degrees, that is, there was
a lower resolution than necessary. As discussed
in this section, the 90-degree construction angle
producedsupportxationinthecompletecrown
margin, resulting in the complete crown with
margin misadaptation. A third print was then
made, adjusting the layer thickness to 0.03mm
and 9 lower layers, moreover reducing the
number of complete crowns to 3 complete crowns
per print and increasing the number of supports
per complete crown (Figure 11). The 90-degree
printing angle was discarded, using a 150-degree
angle concerning the X-axis. This last impression
obtained complete crowns with visible marginal
Figure 10 - Printing platform of the pilot study. Pilot study with printing of complete crowns positioned at 90 degrees (A); 180 degrees (B);
and 150 degrees (C) concerning the X-axis.
Figure 9 - Volume deviation between design and printed complete
crown.
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Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
adaptation to the master model (Figure 12), so
the same printing parameters were used to make
the samples and, later, evaluate dimensional
accuracy.
RESULTS
The data were explored for normality by
checking the distribution of the data and using
the Dwass-Steel-Critchlow-Fligner and Shapiro-
Wilk tests. The ANOVA one-factor test was used
to compare average values. The significance
level was established at p ≤ 0.05 and a 95%
condenceinterval.Table I presents RMS data
for the crowns of each group. Even the groups
presenting homogeneity according to the Levene
test (p=0.728), except for the 180° group
with four samples, the other groups did not
follow normal distribution, because their values
according to the Shapiro- Wilk test, were below
thesignicancelevelα=0.05.
Table II shows the multiple comparisons
for dimensional accuracy between the groups
studied, showing that there was no a statistically
signicantdifference(p≤ 0.05).
Table III presents the results from the
Kruskal-Wallis test between the groups studied,
the test reveals that there is no statistically
significant difference between the groups for
dimensional accuracy (p value= 0.340), that
is,p-valueabovethesignicancelevelα=0.05.
Table IV presents volume values for the crowns of
each group. Table V presents the results from the
Kruskal-Wallis test between the groups studied,
the test reveals that there is no statistically
significant difference between the groups for
volume (p value= 0.084), that is, p-value above
thesignicancelevelα=0.05. Finally, Table VI
presents multiple comparisons between the
groups for volume value analyses.
Figure 11 - Printing of 3 complete crowns with an angle of 150º degrees concerning the X-axis.
Figure 12 - Marginal adaptation of complete crowns printed in the pilot study. Provisional complete crowns printed without marginal adaptation
to the master model (A) and printed complete crowns adapted to the master model (B).
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Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
Table I - Nominal values of RMS per crown
Grup A (150 - 3) Grup B (150 - 4) Grup C (180 - 3) Grup D (180 - 4)
0.149297874 0.079381668 0.099005929 0.096150546
0.051898731 0.128141679 0.114629207 0.102345677
0.095500209 0.105658734 0.142159841 0.072176314
0.059180298 0.077464344 0.060585003 0.126465324
0.06366378 0.090750531 0.040985912 0.031364326
0.128652783 0.034763877 0.042270814 0.042307475
0.072446427 0.04668881 0.032397722 0.048119683
0.04668881 0.039854386 0.037695228 0.059337427
0.077464344 0.032943456 0.032943456 0.040280028
0.04668881 0.040985912 0.033154559 0.066478416
0.048086461 0.04 0.034450279 0.052095619
0.031364326 0.035535766 0.031364326 0.060585003
Table II - Multiple comparisons Dwass-Steel-Critchlow-Fligner – Dimensional accuracy
Multiple comparisons - RMS (mm)
W p
150° - 03 Impressions at a time 150° - 04 Impressions at a time -1.430 0.743
150° - 03 Impressions at a time 180° - 03 Impressions at a time -2.246 0.386
150° - 03 Impressions at a time 180° - 04 Impressions at a time -0.368 0.994
150° - 04 Impressions at a time 180° - 03 Impressions at a time -1.225 0.822
150° - 04 Impressions at a time 180° - 04 Impressions at a time 0.980 0.900
180° - 03 Impressions at a time 180° - 04 Impressions at a time 1.879 0.545
Table III - ANOVA one factor (non-parametric Kruskal-Wallis) - Dimensional accuracy
Kruskal-Wallis
χ2gl P
RMS (mm) 3.35 3 0.340
Table IV -. Volume values per crown, in mm3
Grup A (150 - 3) Grup B (150 - 4) Grup C (180 - 3) Grup D (180 - 4)
343.35 344.26 368.31 375.77
319.82 362.35 363.72 358.18
351.88 359.5 368.56 352.74
365.04 314.89 343.36 376.19
373.98 379.23 350.52 357.14
380.2 364.84 351.46 347.13
368.1 375.29 348.85 340.02
373.52 373.5 345.44 364.43
357.99 378.23 336.26 337.02
353.77 361.53 350.42 363.48
374.08 371.45 339.48 339.65
363.2 351.58 329.68 352.42
CAD reference value= 325.45 mm3.
10
Braz Dent Sci 2024 Apr/Jun;27 (2): e4366
Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
DISCUSSION
It is important to emphasize that the
evolution of printed materials has been taking
place without a consensus in the literature on the
ideal standards for 3D printing. Thus, in addition
to analyzing the properties of printed materials,
it is important to specify the methodology used
to establish the ideal parameters for printing
materials for dental purposes.
The image overlay method used in the
present study proved to be a suitable method
and followed the study by Chaturvedi et al.
in 2020 [12]. To evaluate the adaptation of the
complete crowns, the authors of this study used
direct visualization measurement tools in the
SEM (scanning electron microscopy). They cited
adaptation evaluation techniques, such as the
triple scanning technique and the silicone replica
(SRT) technique. The SRT has as a disadvantage
thedifcultyinlocatingthemargins,ruptureof
the silicone layer, presence of defects in the surface
of the silicone (for example the incorporation
of bubbles), and errors in the cutting planes.
Thus, in addition to studying the properties of
materials developed by CAD/CAM technology, it
is interesting to study more effective methods for
the accuracy of the adaptation of these materials,
such as, for example, optical metrology through
the overlapping of images, which is an example
of a digital method of measurement.
LCD (liquid crystal display) printers are the
most used in dentistry because they have a good
cost-benet[13-15]. In general, these printers
have high precision and are suitable for fine
details and functional printing [15], however,
the DLP-type printers are less accurate and have
slower processing [13,14]. DLP-type printers have
minor disadvantages precision in larger parts of
the 3D object, so they are not suitable for work
with larger pieces that require high precision,
for example, printing of working models [15].
The LCD printer, on the other hand, can print
working models with high precision. For the
printing of temporary prostheses, LCD-type
printers have similar performance to DLP printers
about the accuracy, provided that a powerful
post-polymerization unit is used or a long post-
curing time. In addition, they are printers with
a lower cost of obtaining compared to DLP-type
printers, facilitating their acquisition in dental
clinics [13]. Thus, the present study used an
SLA-type printer for printing provisional crowns,
respecting the appropriate polymerization unit
and post-curing time, since it is the type of printer
mostusedindentalclinics,duetothecostbenet.
It is supported by the literature that the
orientation of printing, the angle of construction,
andthepositioninuencenotonlytheaccuracy
of the printing but also other properties, such
as compressive strength, surface morphology,
and the bacterial response of printed provisional
complete crowns [16]. Regarding the mechanical
properties, the 90° angle about the X-axis of
the construction platform produces a more
resistant piece to compression [6] compared to
Table V - ANOVA one factor (non-parametric Kruskal-Wallis) - Volume
Kruskal-Wallis
χ2gl P
Volume (mm3) 6.66 3 0.084
Table VI - Dwass-Steel-Critchlow-Fligner multiple comparisons - Volume
Multiple comparisons - Volume (mm3)
W p
150° - 03 Impressions at a time 150° - 04 Impressions at a time 0.163 0.999
150° - 03 Impressions at a time 180° - 03 Impressions at a time - 2.858 0.180
150° - 03 Impressions at a time 180° - 04 Impressions at a time - 1.470 0.726
150° - 04 Impressions at a time 180° - 03 Impressions at a time - 3.103 0.125
150° - 04 Impressions at a time 180° - 04 Impressions at a time - 1.878 0.545
180° - 03 Impressions at a time 180° - 04 Impressions at a time 1.633 0.656
11
Braz Dent Sci 2024 Apr/Jun;27 (2): e4366
Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
a piece printed at 180° due to the orientation
of the layers [15]. However, concerning the
accuracy of complete crowns, the angle of 90° is
not indicated, because perpendicular angles to
the construction platform can result in support
xationclosetotheedgeofthecompletecrown
and, consequently, complete crowns with
unsatisfactory adaptation [9,16].
The best marginal adjustment of complete
crowns was obtained with construction angles of
120° and 135° about the X-axis of the construction
platform and 150° and 180° [9,16]. The present
study used angulations of 150° and 180°, following
the guidelines of the study by Ryu et al. [9],
because it deals with the printing of provisional
complete crowns, as was done in this study.
The literature shows that the accuracy of
thenalpieceisinuencedbythenumberof
specimens printed on the same construction
platform [10] and by the printing angle concerning
the X-axis of the platform [9]. The degree of light
energy applied when there is only one specimen
can be excessively high, which may result in a
larger piece than that provided for in the digital
leandalackofprecisioninthenerdetails.
Similarly, with six specimens on the printing
platform, the light is distributed very widely
to provide the necessary light energy, and the
transferencetothetargetisinefcient,which
may result in smaller parts than predicted in
thedigitalle,partialortotalprintingfailure
and parts with impaired resistance. The printing
of three specimens at a time on the same
construction platform results in complete crowns
with adequate precision for clinical use, as there
is adequate light distribution [10]. However, until
the present study, there has been no research
that evaluated the accuracy of complete crowns
printed by a construction platform with four
and five complete crowns at the same time,
since there is a gap between the ideal number
of complete crowns printed at the same time
(three) and the number that results in complete
crowns without adequate precision (six). Thus,
the present study evaluated whether the precision
pattern of complete crowns printed with three
specimens on the same construction platform
is maintained with four specimens. The results
showed that there were no statistical differences
in the dimensional accuracy of complete crowns
printed with three and four specimens at the same
time, indicating that printing with four specimens
bringsgreatercostbenetcomparedtoprinting
with three specimens, in addition to reducing the
time of making the piece.
The choice of print material is associated
with the application and the type of
printer that will be used. In the studies of
Tahayeri et al. [6] and Ryu et al. [9], a micro-
hybrid 3D printing photoactivated resin was used,
indicated for long-lasting provisional prostheses
(NextDent C&B), which has flexural strength
and polishing capacity suitable for provisional
prostheses. The study of de Tahayeri et al.
[6] used a 3D printer of the SLA type and the
study of Ryu et al. [9] used a 3D printer of
the DLP type, both use a light source for the
polymerization of the material. In the present
study, the photoactivated resin Resilab 3D
(Wilcos do Brasil Indústria e Comércio Ltda -
Brasil, Petrópolis, RJ) was used, which can be
used in printers that use light processing and this
materialhaspropertiesofresistancetoexion
and polishing capacity suitable for provisional
prostheses, as in previous studies. Already, the
study of Mukai et al. [17], presented that the
photoactivated resin E-Guide Tint (EnvisionTEC)
was used to evaluate the accuracy of printed
materials through the overlapping of images,
as was done in the present study. This resin has
propertiesofresistancetoexionandpolishing
capacity similar to the resin used in the present
study and the resins used in the studies cited
in this paragraph, however, it has greater
biocompatibility, because its indication is for the
manufacture of surgical guides [17].
A pilot study was made to delimit the sample
number of the present study. In the pilot study,
n=3 was used for groups A and C, because
they are groups that were printed 3 crowns on
the same construction platform, varying the
angulation. Following this reasoning, n=4 was
used for groups B and D. According to the results
of the pilot study, n=12 was used because it is the
lowest common denominator between 3 and 4.
The absolute values for RMS of the printed
complete crowns obtained through the distance
deviations between the CAD and MESH files
corroborate the absolute cementation line
evaluation values, in which the reference values
for marginal adaptation are less than 120 µm [11].
The overlap of images made possible an analysis
qualitative comparison of the surface with color
histogram between the CAD and MESH files.
The patterns of distortion in the pulp walls
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Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
have a predominance of red and yellow colors,
indicating an excess of material, while in the axial
walls, green colors are predominant, indicating
deviations close to zero, and blue, indicating a
lack of material in this region.
The present study showed results that follow
the study by Ryu et al. [9], because the complete
crowns showed clinically adequate dimensional
acuity with printing angles of 150° and 180°.
According to Siqueira et al. [18] variables such
as build orientation and printing angle have an
impact on material properties, product accuracy,
and even biocompatibility. Although analyzing
the results for RMS and volume deviation
objectively, there were no statistical differences
between the construction angulation variables
(150° and 180°) and the number of specimens
printed on the same platform (three or four
crowns at a time). Although they did not present
statistical differences in the present study, the
crowns printed at 150° obtained distance values
closer to 120 micrometers (reference value
for clinical acceptability), about the complete
crownsprintedat180°.Thejusticationforthis
mayberelatedtotheowoftheresin,since
the complete crown is parallel to the platform
when positioned at a 180° angle, resulting in an
accumulation of resin in the lower region. In a
complete crown positioned at 150° about the
construction platform, there is less chance of resin
accumulation,becausethereisaowareaforit.
The results for dimensional accuracy and
volume deviation showed no statistical differences
between the groups with three complete crowns (A
and C) and the groups with four complete crowns
(B and D) printed on the same printing platform.
This shows that the printing of four complete
crowns at a time has a greater cost-benefit
compared to the printing of three complete crowns
because it can maintain an adequate precision
standard and a greater number of complete crowns
can be produced in less time.
In general, the dimensional acuity values of
the complete crowns found in this study show that
3D printing processing is suitable for dentistry
and follows previous studies presented above in
the discussion. 3D printing is certainly promising
in dentistry, so much so that Yildirim’s study [19]
even recommends printed complete crowns rather
than milled or heat-pressed complete crowns by
the conventional method, which corroborates
the results for the dimensional accuracy of the
present study. The number of complete crowns
printed with a stereolithographic printer interferes
withthenalresolutionofthepieceasmuchas
the printing parameters, because the material
can receive an excessive or inefficient amount
of light [13,14,20-22]. It is supported by the
literature that the printing of 3 crowns at a time
obtains complete crowns with better resolution
than the printing of 9 complete crowns at the
same time [10]. This information follows the
results of the present study because there was no
statistical difference in the dimensional acuity of
complete crowns printed with 3 or 4 complete
crowns at a time on the same construction
platform. The printing angles of 150 degrees and
180 degrees about the x-axis produced satisfactory
results for dimensional acuity in the present study,
agreeing with the angulation of 150 degrees and
180 degrees indicated in the previous study [9].
Moreover,asignicantclinicalimplication
supporting the preference for printed complete
crowns over conventional ones could be self-
polymerizableresinsposeasignicantchallenge
in this regard, relying on a chemical activator
rather than heat to establish numerous chemical
bonds, which can lead to higher levels of uncured
material. These levels may vary depending on
thespeciccompositionofeachproductandthe
processing techniques employed. Additionally,
utilizing the fastest digital scanning and printing
processes helps mitigate potential issues
associated with provisional elements, such as
minimizing their impact, for example, mitigating
allergies related to these components [23].
The present study presents as a limitation the
use of only one type of resin for printing and one
type of 3D printer, since it would be interesting to
compare these results with other types of resins
and 3D printers, given the diversity currently
available for dental use.
In addition to the issues of printing angulation
and the number of complete crowns printed at
the same time, the present study contributes to
thedenitionofamethodologyfor3Dprinting
in dentistry, because it is a factor that is not yet
clear in previous studies, due to the great diversity
of printers and materials available for printing.
Thus, it is important to emphasize that more
studies are needed to compose this methodology
in a sedimented way in the literature, to make
this knowledge more accessible to dentists in the
daily life of the clinic.
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Pereira ER et al.
Dimensional accuracy of pro visional complete crown made by the 3D printing method
Pereira ER et al. Dimensional accuracy of provisional complete crown made by
the 3D printing method
CONCLUSION
Considering the results obtained, the present
study concludes that, based on dimensional
accuracy and volume deviation, the printing of
provisional complete crowns with an LCD-type
3D printer has adequate accuracy both with an
angle of 150 degrees about the X-axis, and with
an angle of 180 degrees about the X-axis of the
construction platform. There is no difference
between printing three or four complete crowns
printed at the same time on the same construction
platform. Thus, the printing of four complete
crowns on the same construction platform has
agreatercost-benetcomparedtotheprinting
of three complete crowns, as it offers similar
precision and shorter manufacturing time.
Additionally, this type of manufacturing facilitates
obtaining the part, reduces allergenic risks to the
patient, and mitigates potential human errors
during the conventional manufacturing process.
Author’s Contributions
ERP: Investigation, Data Curation and
Writing – Original Draft Preparation. LGBS: Data
Curation, Formal analysis. MSC: Writing – Review
& Editing. GCL: Writing – Review & Editing. RMA:
Supervision and Project Administration.
Conict of Interest
Noconictsofinterestdeclaredconcerning
the publication of this article.
Funding
Theauthorsdeclarethatnonancialsupport
was received.
Regulatory Statement
None.
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Gabriel Cirone Lopes
(Corresponding address)
Universidade Estadual Paulista “Júlio Mesquita Filho” - UNESP,
Instituto de Ciência e Tecnologia, Departamento de Materiais
Odontológicos e Prótese, Campus de São José dos Campos, SP, Brazil
Email: gabriel.cirone@unesp.br
Date submitted: 2024 May 23
Accept submission: 2024 July 07
