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.2023.e3873
1
Braz Dent Sci 2023 July/Sept;26 (3): e3873
Effect of laboratory and chairside polishing methods on the
surface topography of occlusal splint materials manufactured using
conventional, subtractive and additive digital technologies
Efeito de métodos de polimento em laboratório e em consultório na topografia de superfície de materiais de
splint
oclusal
fabricados usando tecnologias digitais convencionais, subtrativas e aditivas
Halenur BILIR1 , Suzan Eda EYYUPOGLU1 , Enes KARAMAN1 , Mutlu ÖZCAN2 , Nenad LUKIC2
1 - Istanbul Medipol University, School of Dentistry, Department of Prosthodontics. Istanbul, Turkey.
2 - University of Zurich, Center of Dental Medicine, Clinic of Masticatory Disorders and Dental Biomaterials. Zurich, Switzerland.
How to cite: Bilir H, Eyyupoglu SE, Karaman E, Lukic N. Effect of laboratory and chairside polishing methods on the surface
topography of occlusal splint materials manufactured using conventional, subtractive and additive digital technologies. Braz Dent Sci.
2023;26(3):e3873. https://doi.org/10.4322/bds.2023.e3873
ABSTRACT
Objective: This study evaluated the polishing properties of the occlusal splint materials obtained using subtractive
and additive manufacturing methods with the laboratory-type polishing (LP) and chairside-type polishing (CP)
procedures. Material and Methods: Specimens (N=180, n=60 each group) were manufactured using one of
the following methods: subtractive manufacturing method (SMM) (M-PM Disc, Merz Dental GmbH), additive
manufacturing method (AMM) (Freeprint Splint 2.0, DETAX GmbH & Co. KG), and the conventional manufacturing
method (CMM) (Promolux HC, Merz Dental GmbH). Following LP and CP procedures, surface roughness of the
specimens was measured using a digital surface prolometer. One representative specimen was selected from each
group, and a scanning electron microscope (SEM) image was made. Results: Both the manufacturing method
and the polishing procedures signicantly affected the results (P<0.01). Interaction terms were also signicant
(P<0.001). Conclusion: With both polishing methods, surface roughness of the AMM group was the highest
and the CMM group the least. Although the CP procedure was more effective than LP with both methods, surface
roughness was below the 0.2 μm threshold after both polishing procedures tested.
KEYWORDS
CAD-CAM; Dental materials; Occlusal splints; PMMA; Surface properties.
RESUMO
Objetivo: Este estudo avaliou as propriedades de polimento dos materiais de splint oclusal obtidos usando
métodos de fabricação subtrativos e aditivos com os procedimentos de polimento laboratorial (LP) e polimento
em consultório (CP). Material e Métodos: As amostras (N=180, n=60 para cada grupo) foram fabricadas
usando um dos seguintes métodos: método de fabricação subtrativo (SMM) (M-PM Disc, Merz Dental GmbH),
método de fabricação aditivo (AMM) (Freeprint Splint 2.0, DETAX GmbH & Co. KG) e o método de fabricação
convencional (CMM) (Promolux HC, Merz Dental GmbH). Seguindo os procedimentos de LP e CP, a rugosidade
da superfície dos espécimes foi medida usando um perlômetro de superfície digital. Um espécime representativo
foi selecionado de cada grupo, e uma imagem de microscópio eletrônico de varredura (SEM) foi obtida.
Resultados: Tanto o método de fabricação quanto os procedimentos de polimento afetaram signicativamente os
resultados (P<0,01). Os termos de interação também foram signicativos (P<0,001). Conclusão: Com ambos os
métodos de polimento, a rugosidade supercial do grupo AMM foi a maior e a do grupo CMM a menor. Embora
o procedimento CP tenha sido mais ecaz do que LP com ambos os métodos, a rugosidade da superfície cou
abaixo do limite de 0,2 μm após ambos os procedimentos de polimento testados.
PALAVRAS-CHAVE
CAD-CAM; Materiais dentários; PMMA; Propriedades de superfícies;
splints
oclusais.
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Braz Dent Sci 2023 July/Sept;26 (3): e3873
Bilir H et al.
Effect of laboratory and chairside polishing methods on the surface topography of occlusal splint materials manufactured using conventional, subtractive and additive digital technologies
Bilir H et al. Effect of laboratory and chairside polishing methods on the
surface topography of occlusal splint materials manufactured
using conventional, subtractive and additive digital technologies
INTRODUCTION
Temporomandibular disorder (TMD) is
a general term that encompasses a variety of
clinical complaints involving the masticatory
muscles, temporomandibular joint (TMJ), or
associated orofacial structures [1]. The etiology
is multifactorial and involves a large number
of indirect and direct causal factors such as
parafunction, trauma, and the causes of increased
joint friction, alone or together [2-5]. Although
the relationship between bruxism and TMD is
still controversial, a relationship between sleep
bruxism (SB) and TMD was found in self-reported
studies evaluating the presence of SB [6].
The use of occlusal splints as a non-invasive
procedure for known bruxism is quite a common
treatment [7,8].
The compression molding technique
and vacuum thermoforming are commonly
applied in manufacturing occlusal splints.
Porosity, polymerization shrinkage, and residual
monomer content are factors encountered in
these conventional methods that have an adverse
effect on the quality of occlusal splints [9-11].
The increasing use of new technologies in dentistry
has replaced conventional manufacturing with
digital workflows in various processes [12].
In computer-aided design and computer-aided
manufacturing (CAD/CAM) technology, the
subtractive manufacturing method (SMM) and
additive manufacturing method (AMM) are
also implemented in manufacturing occlusal
splints [13,14].
The SMM is based on manufacturing
occlusal splints by milling a polymer disc.
The advantage of this method is that an industrial
polymethylmethacrylate (PMMA) disc is used
which provides a better passive t in the mouth
due to the high degree of double bond conversion
and the absence of polymerization shrinkage.
The disadvantage however is the significant
amount of unusable material waste created by
milling the industrial disc [14]. The AMM, on
the other hand enables the manufacturing of
more complex objects yielding to less waste
material and without applying excessive force as
the manufacturing takes place layer by layer in a
three-dimensional (3D) printer from 3D model
data [13].
Numerous AMMs are currently available
according to the material used and the method
of application. The methods used to provide
polymerization with ultraviolet light for polymeric
resins are stereolithography (SLA), PolyJet, and
digital light processing (DLP) [15,16].
It is crucial for the surfaces of occlusal
splints to have smooth surfaces. An ideally
polished surface prevents discoloration and
bacterial adhesion and does not irritate the
mucosa [17,18]. In previous studies, it has been
reported that the tip of the tongue can detect a
roughness up to 50 μm [19,20]. The clinically
acceptable polishing threshold of an appliance to
be placed in the mouth is below 0.2 μm [21,22].
There is no consensus regarding the polishing
procedure for occlusal splints as a function of LP
and CP procedures. In the literature, polishing
procedures are generally divided into two types:
two-body wear abrasion and three-body wear
abrasion [23]. During the polishing of resin
occlusal splints, standard polishing procedures
(i.e. polishing burs, pumice, and high-shine
polishing protocols) are followed similar to
polymethylmethacrylate based other dental
appliances [24]. However, the suitability of these
methods for occlusal splints produced using the
SMM or AMM is unknown.
The aim of this study therefore was to evaluate
the polishing properties for the occlusal splints
obtained using three manufacturing methods and
LP and CP polishing procedures. The rst null
hypothesis of the present study was that there
would be no signicant difference in the surface
topography of the splints produced with the
three manufacturing methods. The second null
hypothesis was that there would be no signicant
difference between LP and CP procedures in the
polishing of occlusal splints.
MATERIALS AND METHODS
The specimens were manufactured using
three methods: SMM (n=60), AMM (n=60),
and CMM (n=60). The details of the materials
used in all three production methods are shown
in Table I. The manufacturing of the specimens
and polishing procedures were performed by a
single researcher (H.B.) in order to prevent the
effect of differences between practitioners on the
outcomes who was blinded to the groups.
Specimen preparation
The discs (diameter: 15 mm; thickness;
3 mm) were designed in the CAD program
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Braz Dent Sci 2023 July/Sept;26 (3): e3873
Bilir H et al.
Effect of laboratory and chairside polishing methods on the surface topography of occlusal splint materials manufactured using conventional, subtractive and additive digital technologies
Bilir H et al. Effect of laboratory and chairside polishing methods on the
surface topography of occlusal splint materials manufactured
using conventional, subtractive and additive digital technologies
(SolidWorks 3D CAD, Dassault Systèmes
SolidWorks Corporation, Waltham, Canada).
The data were used as a master standard
tessellation language (STL) le to fabricate all
the milling and printing specimens. For the SMM
group, PMMA discs (M-PM Disc, Merz Dental
GmbH, Lütjenburg, Germany) were milled
using a 5-axis milling machine (M30, CAMCube,
Montreal, Canada). The specimens of the AMM
group were printed at 50 μm layer thickness
by curing the photopolymerized acrylic resin
liquid (Freeprint Splint 2.0, DETAX GmbH & Co.
KG, Ettlingen, Germany) using a DLP 3D printer
(D20+, Dental Wings Inc, Montreal, Canada) with
the wavelength of 385 nm, at a building angle
of 0°. The specimens were rinsed in isopropanol
(99%) twice for 2 minutes in order to prevent
the formation of non-polymerized monomer
residues. The polymerization of the specimens
was completed by curing them for 10 minutes
in an ultraviolet polymerization device (SHERA
flash-light Plus, Shera Material Technology
GmbH & Co. KG, Lemförde, Germany) twice with
2000 ashes and a 5-minute break.
The specimens in the CMM group were
fabricated using the compression molding
technique. First, disc-shaped patterns (diameter:
15 mm; thickness; 3 mm) were milled from wax
discs in accordance with the data prepared in the
CAD program. The disc-shaped waxes were then
placed in a ask with hard dental plaster type
IV (Fujirock EP, GC Europe, Leuven, Belgium).
The wax patterns were eliminated in 70°C
water for 20 minutes. Thereafter, the ask was
opened, and wax elimination was completed by
washing the wax residues with water at the same
temperature. The monomer and polymer of the
heat-polymerized PMMA (Promolux HC, Merz
Dental GmbH, Lütjenburg, Germany) were mixed
according to the manufacturer’s instructions.
The mixture of PMMA was tapped in the place
of the wax patterns. The ask, tightened with a
clamp, was placed in the polymerization device
(C-11, Ermetal Dental, Ankara, Turkey) with
water at room temperature. After reaching 100°C,
polymerization began at this temperature for
30 minutes. At the end of this period, the ask
was removed from the polymerization device and
left to reach room temperature. The specimens
were then stored in water at room temperature for
48 hours. They were pre-polished for 2 minutes at
a contact pressure of 0.3 MPa under continuous
water cooling in a polishing machine (Polishing
Machine, Mecatech 334 SPC, Presi France, Eybens,
France) with 400-, 800-, 1200-, and 1500-grit
silicon carbide papers (Silicon Carbide Grinding
Paper, Struers ApS, Ballerup, Denmark) [17].
Twenty pre-polished specimens from each group
were used as the CG (CG).
Labside polishing
A platform was designed in the CAD
program (SolidWorks 3D CAD) by curing the
photopolymerized acrylic resin liquid (Freeprint
Splint 2.0) using a DLP 3D printer (D20+, Dental
Wings Inc.) to apply the standard polishing
procedure to all specimens. A round-shaped
area with the diameter of the specimens and a
depth of 2 mm was arranged in the middle of the
platform. The height of the platform was adjusted
so that the specimen surfaces to be polished
were in full contact with the polishing heads
attached to the LP device. This platform was
supported by the practitioner (H.B.) to prevent
the movement of the specimens during the
polishing steps. A lathe bristle brush (Polishing
Brushes Chungking White, Bredent GmbH & Co.
KG, Senden, Germany) was attached to the LP
Table I - The brands, types, manufacturers, chemical compositions, and batch numbers of the materials used in the current study
Brand Type Manufacturer Chemical Composition Batch number
M-PM Disc Clear
Clear disc suitable for
production by milling
method
Merz Dental GmbH,
Lütjenburg, Germany
Polymethylmethacrylate (PMMA)
and cross-linked polymers based on
methacrylic acid esters, dibenzoyl
peroxide, residual monomer <1%
21118
Freeprint Splint 2.0 Photo-polymerized
liquid resin
DETAX GmbH &
Co. KG, Ettlingen,
Germany
Acrylate resin, aliphatic urethane acrylate,
tripropylene glycol diacrylate (TPGDA),
tetrahydrofurfuryl methacrylate (THFMA),
thermoplastic polyolefins (TPO)
230101
Promolux HC Heat-polymerized
resin (powder, liquid) Merz Dental GmbH
Powder: PMMA copolymer,
dibenzoylperoxide, organic colorants,
inorganic pigments. Liquid: MMA,
dimethylmethacrylate
1020003
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Effect of laboratory and chairside polishing methods on the surface topography of occlusal splint materials manufactured using conventional, subtractive and additive digital technologies
Bilir H et al. Effect of laboratory and chairside polishing methods on the
surface topography of occlusal splint materials manufactured
using conventional, subtractive and additive digital technologies
device (Poliereinheit PE5, Degussa AG, Hanau,
Germany), and 20 specimens from each group
were brushed with laboratory-type pumice
slurry (Pumice Fine Grits, Kerr Corp., Orange,
CA, USA). Then, pumice slurry application was
continued with a rag wheel (Abraso-sil Acrylic,
Bredent GmbH & Co. KG, Senden, Germany).
After the specimens were washed, polishing paste
(Universal Polishing Paste, Ivoclar Vivadent Inc.,
Schaan, Liechtenstein) was applied with a soft
cloth wheel (High Luster Buff Acrylic, Bredent
GmbH & Co. KG, Senden, Germany) to obtain a
glossy surface. All the polishing steps were applied
to each specimen for 2 minutes at 3000 rpm.
Finally, the specimens were ultrasonically cleaned
(Eurosonic Energy, Euronda SpA, Vicenza, Italy)
for 1 minute and left to dry.
Chairside polishing
In order to ensure standardization in the CP
procedure, a stabilizing unit for a micromotor-
coupled handpiece (STRONG 206, SAESHIN,
Daegu, Korea) and a platform where the
specimens would be placed were designed in the
CAD program (SolidWorks 3D CAD) and printed.
The height of the platform and the depth for
placing the specimens were adjusted as specied
in the LP procedure. Twenty specimens from each
group underwent CP with a polishing kit (EVE
Denture Polishing Set, EVE Ernst Vetter GmbH,
Keltern, Germany). For that, the green, gray, and
yellow rubber polishers included in the set were
used. After that, polishing was continued with the
brown rag wheel followed by the pink rag wheel
included in the set. After the specimens were
washed, polishing paste (Universal Polishing
Paste, Ivoclar Vivadent Inc.) was applied with
a soft cloth wheel to obtain a glossy surface.
All polishing steps were applied to each specimen
for 2 minutes at 5000 rpm. Finally, the specimens
were ultrasonically cleaned (Eurosonic Energy)
for 1 minute and left to dry.
Measurement of surface roughness and SEM
Analysis
The surface roughness (Ra) was measured
immediately after the production of the
specimens, after pre-polishing, and after applying
the LP and CP procedures using a digital surface
profilometer (Perthometer M2, Mahr GmbH,
Gottingen, Germany). The highest point of
the diamond stylus of the profilometer was
measured at a constant speed of 1 mm/s and the
measurement length of 2 mm on each specimen’s
surface. The surface roughness was calculated by
measuring 3 vertical and 3 horizontal lines for
each specimen and taking the average of these
6 lines [18]. The profilometer was calibrated
before measuring each specimen.
After the specimens were produced and after
all the polishing procedures had been carried out,
one representative specimen was selected from
each group, and scanning electron microscopy
(SEM) (Carl Zeiss EVO LS 10, Carl Zeiss NTS
GmbH, Aalen, Germany) images were obtained
at x600, 1500, and 2500 magnication.
Statistical analysis
A sample size of 12 in each group was
estimated with 95% confidence (1-α), 95%
test power (1-β), and f=0.40 effect size (PASS
15 Power Analysis and Sample Size Software-2017,
NCSS LLC., Kaysville, Utah, USA). The number of
specimens was determined to be 20 in each group
to increase the power of the study and to account
for the possibility of damage occurring in any of
the specimens. Data were analyzed with SPSS
version 23 (IBM). The assumption of normality
was tested using the Kolmogorov-Smirnov test.
Two-way ANOVA and Tukey`s tests were used
to compare the Ra values according to polishing
procedures and manufacturing methods. Data
were presented as mean and standard error.
P<0.05 was considered as statistically signicant
in all tests.
RESULTS
Both the manufacturing method and the
polishing procedures signicantly affected the
results (P<0.01). Interaction terms were also
signicant (P<0.001).
There was a signicant difference between
the surface roughness values according to
the polishing types (P=0.001), where the
specimens that underwent CP showed the lowest
surface roughness values (Table II). The mean
Ra values of the CG, the CP group, and the
LP group were 0.195±0.005, 0.064±0.005,
and 0.099±0.004 μm, respectively (Table III,
Figure 1).
Regarding manufacturing methods, the
lowest mean Ra value was obtained in the CMM
group (P=0.001). The mean Ra values of the AMM,
CMM p, and the SMM groups were 0.168±0.006,
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Bilir H et al.
Effect of laboratory and chairside polishing methods on the surface topography of occlusal splint materials manufactured using conventional, subtractive and additive digital technologies
Bilir H et al. Effect of laboratory and chairside polishing methods on the
surface topography of occlusal splint materials manufactured
using conventional, subtractive and additive digital technologies
0.083±0.006, and 0.099±0.006 μm, respectively
(Table III, Figure 1).
The mean Ra values of the splints produced
via the AMM did not show a signicant difference
compared to those produced using CP and LP
(P=0.700). Similarly, the specimens produced
using the CMM and SMM did not show a
significant difference in the CG (P=0.811)
(Table III, Figure 1).
According to the means of the total Ra
values before-polishing, the CP group, and the
LP group were 1.073±0.091, 0.087±0.012,
and 0.118±0.005 μm, respectively (Table IV,
Figure 2). In the AMM group, CP and LP did not
show a signicant difference (Table IV, Figure 2).
SEM images form specimens immediately
after production showed more irregular and
rough areas in the CMM group among all three
manufacturing methods, while the surface
topography was smoother in the SMM group
(Figure 3). After the surfaces were treated with
silicon carbide papers (CG), lines and slight
indentations were observed in the SMM and CMM
groups, while the traces of grooves in the AMM
group were more prominent. After the CP and
LP procedures roughness decreased and smooth,
homogeneous surfaces became evident in all
groups, but there were more grooves present in
the AMM group than in other groups.
DISCUSSION
In the present study, the surface topography
of occlusal splint materials obtained using three
manufacturing methods were evaluated after two
polishing procedures. The splints manufactured
using the CMM had the best topography, and
Table II - ANOVA results comparing the Ra values with Robust
ANOVA according to polishing type and manufacturing methods
Ra
Test
statistics
P
Polishing method 731.4 0.001
Manufacturing methods 292.7 0.001
Polishing method x Manufacturing
methods 58.1 0.001
Table III - Mean Ra values of AMM, CMM and SMM groups as a function of polishing procedures and multiple comparison of polishing methods
and manufacturing methods
Manufacturing methods
Total
AMM CMM SMM
Polishing method
Control group (μm) 0.243 (±0.011)C0.171 (±0.005)A0.169 (±0.007)A0.195 (±0.005)b
Chairside-type polishing (μm) 0.135 (±0.003)B0.038 (±0.002)D0.044 (±0.001)F0.064 (±0.0048)a
Laboratory-type polishing
(μm) 0.142 (±0.007)B0.063 (±0.003)E0.101 (±0.004)G0.099 (±0.004)c
Total 0.168 (±0.001)a0.083 (±0.006)b0.099 (±0.001)c
a-c There is no difference between polishing types/manufacturing methods with the same letter. A-G No difference between polishing methods
and manufacturing method interactions with the same letter.
Figure 1 - Surface roughness (Ra) of AMM, CMM, SMM groups with applied polishing procedures. The blue dashed line represents the clinical
threshold for surface roughness (0.2 μm).
Manufacturing methods
Ra (μm)
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Bilir H et al.
Effect of laboratory and chairside polishing methods on the surface topography of occlusal splint materials manufactured using conventional, subtractive and additive digital technologies
Bilir H et al. Effect of laboratory and chairside polishing methods on the
surface topography of occlusal splint materials manufactured
using conventional, subtractive and additive digital technologies
the splints manufactured by the AMM showed
the worst polishing properties. Manufacturing
method and polishing method significantly
affected the results. Thus, based on the results,
the rst null hypothesis that there would be no
signicant difference in the polishing properties
of the splints produced using three manufacturing
methods was rejected. The second null hypothesis
that the LP and CP procedures would cause no
signicant difference in the polishing of occlusal
splints was also rejected.
Occlusal splints are generally used at night,
and the salivary flow rate decreases during
sleep [25]. Without mechanical cleaning, mature
Table IV - Mean Ra (μm) values of the AMM, CMM and SMM groups before and after applying polishing procedures and multiple comparison
of polishing methods and manufacturing methods
Manufacturing Methods
Total
AMM SMM
Polishing method
Before 1.407 (±0.048)C0.654 (±0.047)D1.073 (±0.091)a
Chairside-type polishing 0.136 (±0.004)A0.045 (±0.002)B0.087 (±0.012)b
Laboratory-type polishing 0.145 (±0.008)A0.104 (±0.005)E0.118 (±0.005)c
Total 0.391 (±0.117) 0.168 (±0.049)
a-c There is no difference between polishing types. A-E No difference between polishing types and manufacturing methods interactions with the
same letter.
Figure 3 - Representative SEM images of the SMM, CMM, AMM groups after manufacturing and polishing procedures (original magnification.
Figure 2 - Surface roughness (Ra) of AMM, CMM, SMM groups with and without applying polishing procedures. The blue dashed line represents
the clinical threshold for surface roughness (0.2 μm).
Manufacturing methods
Ra (μm)
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Effect of laboratory and chairside polishing methods on the surface topography of occlusal splint materials manufactured using conventional, subtractive and additive digital technologies
Bilir H et al. Effect of laboratory and chairside polishing methods on the
surface topography of occlusal splint materials manufactured
using conventional, subtractive and additive digital technologies
plaque on an occlusal splint can contribute to
gingival diseases and caries [26]. In occlusal
splints, the material type, surface roughness,
and surface free energy are important in terms
of plaque accumulation [27]. In a study by
Quirynen et al. [22], it was reported that
when the surface roughness of the titanium
surface around the implant is less than 0.2 μm,
a biofilm layer is not present. This specific
value is referred to as a threshold value for the
smoothness of dental materials [21,22]. In the
study of Schubert et al. [27], more
C. albicans
accumulation was observed on splint materials
produced through digital methods compared to
those produced using a conventional method.
In the study by Freitas et al. [28] regarding
denture bases, milled and conventional splints
were found to be more successful than printed
splints in terms of preventing
C. albicans
adhesion. In both studies, the surface roughness
of the splints produced using additive method
was the highest, which is in accordance with the
current study. In the present study, the highest
surface roughness was found in the AMM group
compared to occlusal splints produced using other
methods both before and after polishing. As the
surface roughness values remained below 0.2 μm
after both polishing procedures, it is thought
that splints produced using the AMM method
will not pose a clinical problem. Yet, these
ndings need to be further observed clinically.
In the measurements made immediately after
manufacturing, the specimens in the CMM group
were too rough to be measured with a digital
surface prolometer, as seen in the SEM images.
Although the SMM specimens were extremely
smooth when viewed with the naked eye surface
roughness values were above 0.2 μm.
It is not easy to compare the results of
current study with the literature due to the
variability of many parameters about polishing
studies. In this study, the surface topography of
splints produced by conventional and subtractive
methods were found to be more successful than
those produced by the additive method. In the
study of Grymak et al. [18], it was observed
that the surface roughness of heat polymerized
splints was less than the splints produced with
the subtractive method when they were first
produced. After they used various polishing
methods, they stated that the splints produced
with heat-polymerized and subtractive methods
were better polished in consistence with the
current study. In addition, they stated that the
production angles for splints produced by the
additive manufacturing method are important
for polishability. In another study [29], only
polishing machine was used and the surface
roughness was found to be the least in the splints
produced by the additive method and the most
with the subtractive method. The reasons for
the difference with the present study may be the
difference in the polishing device, the differences
in the production angles in the additive group,
and the material differences in the subtractive
and conventional groups.
Previously it was shown that on the den-
ture bases, manual and mechanical polishing
procedures performed with a polishing kit
demonstrated surface roughness being lower in
manual polishing [30]. The same methods were
applied in two different polishing procedures.
The reason for the differences could be attributed
to the pressure applied by the practitioner. In the
current study, platforms were produced in accor-
dance with the specimens and polishing methods
in both LP and CP procedures in order to avoid
deviations in polishing procedures.
In this study, CP was more effective than LP
for polishing of occlusal splints. In the literature,
the duration of occlusal splint treatment in TMDs
varies between 1 and 12 months [31]. In this
process, after the contacts of the occlusal splints
are checked during the follow-ups of the patients,
and the necessary procedures are carried out on
the occlusal splints where CP is often preferred
because it is practical and enables successful
polishing.
Different 3D printing methods are
implemented in several disciplines in dentistry
of which SLA and DLP technologies are frequently
used in the production of occlusal splints [32].
In the current study, DLP technology was used
to obtain the specimens where rougher surfaces
were observed compared to CMM and SMM
technologies. In the review of Shaikh et al. [32],
superior surface finish quality was advocated
using the SLA method. Future studies should focus
on SLA and DLP technologies for manufacturing
occlusal splints and evaluate their surface texture.
The surface roughness of the splints
produced with the AMM was affected by many
parameters such as the resin type, the resolution
of the printer, the polymerization duration and
the shape, intensity of the laser, along with the
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Effect of laboratory and chairside polishing methods on the surface topography of occlusal splint materials manufactured using conventional, subtractive and additive digital technologies
Bilir H et al. Effect of laboratory and chairside polishing methods on the
surface topography of occlusal splint materials manufactured
using conventional, subtractive and additive digital technologies
orientation of printing [33,34]. In the study of
Campbell et al. [35], the lowest surface roughness
was obtained at an orientation angle of 0 degrees.
In addition, in the study of Grymak et al. [18]
with 3D-printed occlusal splints, it was reported
that the samples produced with a 0-degree angle
had the lowest surface roughness compared to
milled and heat-polymerized splints in the pre-
polishing evaluation. Authors even claimed that
there was even no need for polishing. Here, a
0-degree angle was chosen to produce the AMM
specimens. The reason for choosing a 0-degree
angle in the manufacturing in the AMM group
was to produce specimens with as smooth
surfaces as possible and compare them with other
production methods.
The limitations of present study were
that polishing procedures were employed in a
controlled manner which may not be clinically
always feasible. New AMM technologies that
allow for lower layer thickness should be further
investigated.
CONCLUSIONS
From this study, the following could be
drawn:
1. The chairside polishing procedure tested
was more effective in obtaining a smooth
surface for the splint materials manufactured
using conventional, subtractive and additive
digital methods.
2. After both chairside and labside polishing
procedures, the surface roughness was the
highest with the additive method and the
least with the conventional method.
3. Both chairside and labside polishing
procedures were sufcient to obtain a mean
average roughness value of 0.2 μm set as
a threshold, with all splint materials and
manufacturing methods.
Acknowledgements
The authors acknowledge DETAX GmbH
& Co KG for generous provision of the photo-
polymerized liquid resin.
Author’s Contributions
HB: Conceptualization, Methodology, Data
Curation, Writing – Original Draft Preparation.
SEE: Data Curation, Writing – Review & Editing.
EK: Data Curation, Writing – Review & Editing.
MÖ: Conceptualization, Methodology, Data
Curation, Writing. NL: Data Curation, Writing –
Review & Editing.
Conict of Interest
No conicts of interest declared concerning
the publication of this article.
Funding
This research did not receive any specic
grant from funding agencies in the public,
commercial, or not-for-prot sectors.
Regulatory Statement
The study was waived of ethical approval
because it did not include patients or animals.
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Halenur Bilir
(Corresponding address)
Istanbul Medipol University, School of Dentistry, Department of Prosthodontics,
Istanbul, Turkey.
Email: halenurbilir@gmail.com Date submitted: 2023 May 05
Accepted submission: 2023 June 07
