ARTICLE IN PRESS
Keywords
Air-Borne Particle Abrasion
Air-Abrasion
Indirect Veneering Composite Resin
PEEK
Shear Bond Strength
Surface Roughness
Authors
Sezgi Cinel Sahin *
(DDS)
Lamia Mutlu-Sagesen *
(DDS, PhD)
Isil Karaokutan *
(DDS, PhD)
Mutlu Özcan §
(DDS, PhD)
Address for Correspondence
Sezgi Cinel Sahin *
Email: sezgis@pau.edu.tr
* Associate Professor, Department of
Prosthodontics, Faculty of Dentistry, Pamukkale
University, Pamukkale/Denizli, Turkey
§
University of Zurich, Division of Dental
Biomaterials, Center for Dental Medicine,
Clinic for Reconstructive Dentistry, Zurich,
Switzerlandh
Received: 09.08.2023
Accepted: 31.01.2024
doi: 10.1922/EJPRD_2610Sahin08
European Journal of Prosthodontics and Restorative Dentistry Feb 21 2024
Effect of Particle Size
and Application Pressure
in Air-Borne Particle
Abrasion on the Adhesion of
Polyetheretherketone
ABSTRACT
Introduction: This study aims to investigate the effect of different particle sizes and
pressures on the shear bond strength (SBS) and the roughness (Ra) of polyetheretherketone. Materials and methods: A total of 117 polyetheretherketone specimens were fabricated and divided into a control (CN: no air-particle abrasion) and eight pre-treatment
groups (air-abraded with 50- or 110-µm Al2O3 particles at 1(A), 1.5(B), 2(C), and 2.5(D)
bar). The adhesive, Visio.link was used. Thermal aging was performed. Surface properties, SBS and failure mode were assessed. Data was analyzed by linear regression,
Pearson correlation and Dunnett’s T3 test for pairwise comparisons (p<0.05). Results:
The highest and lowest Ra were found in the 110D and CN groups respectively, and the
highest SBS results were obtained from the 50B group. Pressure and particle size showed
significant difference on the investigated properties (p<0.001). Only adhesive failure was
observed in the CN, and resin cohesive failure was observed in addition to adhesive failure
in the overall study groups. Conclusion: The air-borne particle abrasion procedures and
the adhesive material combination are critical to the strength of the polyetheretherketone bond. The combination of visio.link with the pre-treatment option of 50-µm Al2O3
particles applied at 1.5-bar pressure delivered the most favorable results.
INTRODUCTION
All modifications of the polyaryletherketone (PAEK) family are semicrystalline polymers, and the most well-known member of this family is
polyetheretherketone (PEEK).1-4 Because of its superior milling properties
that are suitable for use with computer-aided design/computer-aided
manufacturing (CAD/CAM) technology and excellent mechanical properties, PEEK can be used in many different dental applications.4-6
The long-term success of PEEK is possible if the material can provide
an ideal bond strength and bonding continuity to other dental materials (e.g., acrylic resins, direct or indirect composite resins, titanium, and
metallic frameworks or attachments) and dental tissues.7,8 However, inert
nature, low surface energy, and poor wettability of PEEK adversely affect
the bonding capacity of the veneering materials, which are recommended
to overcome the aesthetic deficiencies of PEEK, especially those related
to color.4,5 PEEK materials have a grayish-brown or pearly white opaque
color that might not meet the aesthetic expectations. A possible solution to
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
ejprd.org - Published by Dennis Barber Journals.
EJPRD
Copyright ©2024 by Dennis Barber Ltd. All rights reserved.
ARTICLE IN PRESS
European Journal of Prosthodontics and Restorative Dentistry Feb 21 2024
this issue is to use resin-based restorative materials to veneer
PEEK surfaces by employing either direct or indirect methods.
However, it is important to note that the most significant risk
associated with these applications is the difficulty in achieving
strong adhesion to the PEEK surface. This is widely considered
the primary clinical disadvantage of PEEK materials.4,7 For this
reason, pre-treatment applications and surface modification
processes constitute a very important step in establishing successful long-term material adhesion.5,8,9
Many methods, such as air-borne particle abrasion, tribochemical silica coating, etching with sulfuric acid or piranha
solution, laser applications, different types of plasma applications, and adhesive material applications, have been used
to activate the inert surface of PEEK.2,4,5,10-16 From studies examining the methods used for PEEK surface activation, it has
been determined that the air-borne particle abrasion method
increased the adhesion strength of PEEK and positively affected the adhesive properties.4,5,8,10-12,17 Therefore, the most
common approach recommended for PEEK surface modification currently is to abraded the surface of the material with
Al2O3 and apply an adhesive material containing methyl methacrylate (MMA) to the surface.8,10-12,15
The effect of different sizes of Al2O3 particle and air pressures on the bond strength between PEEK and the veneering
material has been investigated in previous studies,2,4,10,13,14,18
but the results of the studies were insufficient.4,5,8,10 In order to
reach a general conclusion on this subject, it is necessary to simultaneously evaluate the effect of particle size and pressure
differences used in the air-borne particle abrasion method on
the bonding properties and surface roughness of the PEEK.5
This study investigates the effect of different Al2O3 particle
sizes and pressures on the shear bond strength (SBS) of PEEK
bonded to indirect veneering composite resin and the surface
roughness of the PEEK.
The null hypotheses of the study are different particle sizes
and application pressures will not affect the SBS of the PEEK
bonded to indirect veneering composite resin, and the surface
roughness of the PEEK.
MATERIALS AND METHODS
SPECIMEN PREPARATION
A total of 117 PEEK (CopraPeek Light, Whitepeaks Dental
Solutions; polyetheretherketone (≈ 80%), titanium dioxide (<
20%), and other additives (< 0.1%)) specimens (10 × 10 × 2
mm) were fabricated by milling CAD/CAM production process
according to ISO 10477. All the specimens were embedded
in autopolymerizing acrylic resin (Meliodent, Heraeus Kulzer)
and polished with 200, 500, 800, and 1000 grit silicon carbide
abrasive papers (Struers) under continuous water cooling in
an automatic polishing machine (Mecapol P 230, Press) at 180
rpm for 1 minute at each grade. The polished specimens were
randomly divided into a negative control group and eight
P2
study groups (n=12 for SBS analysis, n=1 for scanning electron
microscopy analysis for each group) that air-borne particle
abrasion with Al2O3 particles with different properties (Renfert
Basic Classic, Renfert) as a pre-treatment of the PEEK surface:
CN group:
no air-borne particle abrasion
Group 50A:
50-µm particle size with 1-bar pressure
Group 50B:
50-µm particle size with 1.5-bar pressure
Group 50C:
50-µm particle size with 2-bar pressure
Group 50D:
50-µm particle size with 2.5-bar pressure
Group 110A:
110-µm particle size with 1-bar pressure
Group 110B:
110-µm particle size with 1.5-bar pressure
Group 110C:
110-µm particle size with 2-bar pressure
Group 110D:
110-µm particle size with 2.5-bar pressure
All air-borne particle abrasion procedures were performed
at a 45° angle and 10 mm from the specimen surface for 15
seconds. After the air-borne particle abrasion process was
completed, all specimens were cleaned in 70% isopropanol in
an ultrasonic cleaner (Eurosonic Energy, Euronda) for 15 minutes, washed with distilled water for 10 minutes, and dried
under light air pressure.
SURFACE ROUGHNESS AND TOPOGRAPHY
ANALYSIS
Surface roughness measurements were used to analyze
the surface properties of all groups after the air-borne particle abrasion protocol. Measurements were made with a
diamond-tipped contact profilometer (Mahr Perthometer
M2, Mahr) applying a measuring force of 0.7 mN with a trace
length of 6 mm. Measurements were made at three different
areas on each specimen by moving the diamond tip of the
device along the specimen surface in parallel, and the average
roughness data (Ra) of the specimens were calculated. After
each measurement, the profilometer was calibrated with a
special calibration block.
One random specimen selected for analysis by SEM, and the
surfaces of the specimens were coated with 80% gold and
20% palladium using a sputtering device (Q150R ES, Quorum
Technologies). The specimens were evaluated using 1000×
magnification at 20 kV.
INDIRECT COMPOSITE VENEERING PROCESS
The surfaces of the specimens were treated with visio.link
(Bredent) adhesive material according to the manufacturer’s
instructions for the indirect veneering process. Then, indirect
veneering composite resin (Gradia Plus, GC Dental Products)
was applied to the surface of the specimens using a diskshaped silicone mold with a 2-mm diameter and a 3mm
height. The silicone mold was removed after each composite
resin was polymerized according to the manufacturer’s instructions. Information about the composition of the adhesive
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
ejprd.org - Published by Dennis Barber Journals.
Air-Abrasion Effect on Bond of PEEK to Composite...
Copyright ©2024 by Dennis Barber Ltd. All rights reserved.
ARTICLE IN PRESS
European Journal of Prosthodontics and Restorative Dentistry Feb 21 2024
and indirect veneering composite resins and the application
protocol details are summarized in Table 1. After the veneering process was completed, the specimens were kept in distilled water for 1 day at room temperature in a dark environment. Next, all the specimens were aged by thermal cycling
in distilled water for 5000 cycles between 5 °C and 55 °C with
a dwell time of 20 seconds in an automated thermocycling
machine (Gökceler Machines, İstanbul, Türkiye).
SHEAR BOND STRENGTH TEST AND FAILURE MODE
OBSERVATION
A universal test machine (Autograph AGS X, Shimadzu) was
used for the SBS test at a crosshead speed of 1 mm/min. The
SBS values were calculated in megapascals (MPa) by dividing
failure load (N) by the area of the composite resin (a=P/A). The
failure types of all the specimens were analyzed using an optical microscope (MP 320; Carl Zeiss) at 50× magnification. The
failure types were categorized as adhesive failure at the interface between the PEEK and the indirect veneering composite
resin, cohesive failure in the PEEK, cohesive failure in the indirect veneering composite resin, and mixed failure (adhesive
and cohesive failure of at least 25% of the surface).
STATISTICAL ANALYSIS
The sample size for the study was calculated using the GPOWER software (version 3.1.9.2; Heinrich Heine Universitat,
Dusseldorf, Germany). It stipulated nine independent groups
according to an effect size of 0.4, 80% power, and 0.05 sampling error. The SPSS program for Windows, version 21.0
(SPSS Inc., Chicago, IL), was used for statistical analysis. The
normal distribution of the data was evaluated by the ShapiroWilk test. In the comparison of the Ra and SBS results of the
groups, MANOVA with Dunnett’s T3 post hoc test was used
for pairwise analysis. Pearson correlation analysis was used
to determine the correlation between the Ra and SBS values.
The main effect of the particle and pressure differences was
determined by linear regression analysis. Significance was
evaluated as p<0.05 and p<0.001.
RESULTS
SURFACE ROUGHNESS
The highest Ra was found in the 110D group, and the lowest Ra was observed in the CN group. Statistically significant
differences were found between the CN group and all study
groups (p<0.001 for all comparisons). The Ra values of all
groups and statistical differences between groups were summarized in Table 2.
SHEAR BOND STRENGTH
The highest SBS results were obtained in the 50B group, followed by the 50D, 110D, 110B, 110C, 50C, 50A, 110A, and CN
groups. Significant differences were found between the SBS
results of all test groups (p<0.001 for all comparisons) and
the CN group (Table 2). When the particle sizes and pressure
values were evaluated together in the study groups, the highest SBS value was determined in the 50-µm particle size with
1.5-bar pressure (50B) group and the lowest value was determined in the 50-µm particle size with 1-bar pressure group
(50A, p<0.001). In the 110-µm particle size groups, the highest
SBS values were obtained in the group with a 2.5-bar pressure
(110D), and the lowest values were observed in the 1-bar pressure (110A) group (p<0.001, Table 2).
In addition, when the 50-µm and 110-µm particle groups
were evaluated within themselves, it was observed that the
SBS values decreased in the 2-bar pressure groups compared
to the 1.5-bar and 2.5-bar pressure groups. Despite the decrease in the SBS values, no significant difference was found
between the 110C group and the 1.5-bar or 2.5-bar (50B, 50D,
110B, and 110D) groups (p>0.05), while the 50C group showed
a significant statistical difference with the 50B and 50D groups
(p=0.001 and p=0.029, respectively) (Table 2). There was positive correlation between Ra and SBS results (r=0.441, p<0.001).
Table 1. The composition and the application of the materials used in the study.
Product
Composition*
Application recommendation*
visio.link
MMA, 2-prepenoic acid reaction
products with pentaerythritol, diphenyl
(2,4,6-trimethylbenzoyl)-phosphine oxide
Apply the product to the material surface with a brush thinly
and only once. Then immediately apply 90 seconds of light
with a dental laboratory polymerization device (GC Labolight
DUO, GC Dental Products) at 370-400 nm wavelength range.
Gradia Plus®
indirect composite
(nano-hybrid)
1%–5% Bis-GMA, 5-10%TEGDMA,1%–5%
UDMA, ceramic filler
3 minutes of light application (at a wavelength of 380510 nm with approximate peaks at 395 and 475 nm)
in full mode with a dental laboratory polymerization
unit (GC Labolight DUO, GC Dental Products).
*Material contents are presented according to the manufacturer’s information. BisGMA: Bisphenol-A glycidyl dimethacrylate, MMA:
Methyl methacrylate, TEGDMA: triethyleneglycol-dimethacrylate, UDMA: urethane dimethacrylate.
EJPRD
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
ejprd.org - Published by Dennis Barber Journals.
Copyright ©2024 by Dennis Barber Ltd. All rights reserved.
P3
ARTICLE IN PRESS
European Journal of Prosthodontics and Restorative Dentistry Feb 21 2024
Table 2. SBS and surface roughness data (Ra) of all groups.
GROUPS
(n=13)
Ra
Mean ± SD
Min-Max (Median)
CN Group
0.29 ± 0.04a
Group 50A
SBS (MPa)
p*
Mean ± SD
Min-Max (Median)
0.23 – 0.38 (0.3)
11.24 ± 3.6a
2.9 – 14.4 (11.71)
0.45 ± 0.04b
0.4 – 0.56 (0.44)
74.58 ± 37.43b
18.32 – 142.9 (82.32)
Group 50B
0.55 ± 0.04b,c,d
0.46 – 0.59 (0.57)
156.82 ± 19.0c
98.3 – 175.41 (160.7)
Group 50C
0.63 ± 0.05c,e
0.49 – 0.73 (0.63)
86.25 ± 33.54b,f
32.4 – 174.47 (87.72)
Group 50D
0.54 ± 0.08b,c
0.44 – 0.7 (0.54)
139.05 ± 29.42c,d,e
97.71 – 178.93 (141.58)
Group 110A
0.61 ± 0.05c
0.51 – 0.69 (0.61)
57.1 ± 13.51b
34.5 – 77.39 (52.63)
Group 110B
0.72 ± 0.07e,f
0.63 – 0.89 (0.72)
101.95 ± 29.59b,e
50.94 – 146.88 (113.21)
Group 110C
0.81 ± 0.09f
0.68 – 0.96 (0.81)
106.05 ± 32.31b,c
60.36 – 176.72 (96.82)
Group 110D
0.88 ± 0.08f
0.67 – 1 (0.88)
132.47 ± 30.45c,d,e,f
87.28 – 192.74 (133.88)
<0.001
p**
<0.001
* MANOVA with Dunnett’s T3 post hoc multiple comparisons, **Kruskal–Wallis test and Mann–Whitney U test with pairwise analysis:
p<0.05 and p<0.001. No statistically significant difference existed between groups represented by the same letters, but a statistically
significant difference was found between the groups with different letters. SD: standard deviation, Min: minimum, and Max: maximum.
A regression model was established for different pressures
and different particles, and control groups were excluded in
the regression analysis. The linear regression model established to examine the effect of pressure and particles differences on SBS was statistically significant (F=34.637; p<0.001).
When the 50 µm air-borne particle abrasion process was taken
as a reference, the SBS value obtained in the 110 µm air-borne
particle abrasion process was 5.259 lower, but this value was
not statistically significant (p=0.416). When 1-bar pressure
value was taken as reference for the pressure variable, the
SBS value obtained at 1.5-bar pressure was 82.592, the SBS
value obtained at 2-bar pressure was 49.36, and the SBS value
obtained at 2.5-bar pressure was 88.967, and these values
statistically significant (p<0.001, Table 3). Significance was
also obtained in the linear regression model established to
examine the effect of pressure and particles on Ra (F=120.233;
p<0.001). When the 50 µm air-borne particle abrasion procedure was taken as reference, the Ra was obtained 0.238 units
more when the particle size was applied as 110 µm (p<0.001).
When the 1-bar pressure application was taken as a reference,
the Ra value was 0.152 higher for those with 1.5-bar pressure,
0.23 higher for those with a pressure value of 2-bar and 0.221
higher for those with a pressure value of 2.5-bar, and these
values were statistically significant. (p<0.001, Table 3).
When 1-bar pressure value was taken as reference for the
pressure variable, the SBS values for 1.5 bar, 2-bar and 2.5
bar were 82.592 MPa, 49.36 MPa and 88.967 MPa, respectively and statistically significant (p<0.001, Table 3). The effects
of pressure and particles on Ra were also statistically significant (F=120.233; p<0.001). When the 50 µm air-borne particle
abrasion procedure was taken as reference, the Ra was 0.238
P4
unit higher than 110 µm (p<0.001). When the 1-bar pressure
application was taken as a reference, the Ra value was 0.152
unit higher than 1.5-bar pressure, 0.23 unit higher than 2-bar
and 0.221 unit higher than 2.5-bar, and these values were statistically significant. (p<0.001, Table 3).
FAILURE MODE EVALUATION
Only adhesive failure was detected in in the CN and 110A
groups. In addition to adhesive failure, cohesion failure was observed in the indirect veneering resin material in the 50A, 50B,
50D, 110B, 110C, and 110D groups. In the 50C group, cohesive failure was detected in both the indirect veneering resin material
and the PEEK structure in addition to adhesive failure. Mixed
failure was not found in any of the study groups (Table 4).
SURFACE TOPOGRAPHY
SEM images of the surface topography of specimens after
applying air abrasion with different Al2O3 particle sizes and
pressures was shown in Figure 1. The CN group (no air–particle abrasion procedure) exhibited less roughness than the
others (Figure 1A). A homogeneous and dense microporosity was observed in the 50B group (Figure 1B), and alumina
particles embedded on the surface of the specimen were
observed in the 50D group (Figure 1E). In the 110A group, the
embedding of particles on the surface was intense, and there
were particle ruptures on the surface of the PEEK (Figure 1F).
A cleaner specimen surface was observed in the 110B and 110C
groups, with fewer alumina particles embedded than in the
110A group (Figure 1). In the 110D group, deep craters were
formed on the surface, and the embedded alumina particles
or particle ruptures were almost absent (Figure 1I).
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
ejprd.org - Published by Dennis Barber Journals.
Air-Abrasion Effect on Bond of PEEK to Composite...
Copyright ©2024 by Dennis Barber Ltd. All rights reserved.
ARTICLE IN PRESS
European Journal of Prosthodontics and Restorative Dentistry Feb 21 2024
Table 3. Investigation of the effect of pressure and particle differences on SBS and Ra by linear regression
SBS a
β0 (%95 CI)
49.425
Dependent
(37.773 – 61.077)
β1
SD
5.881
Ra b
t
p
VIF
β0 (%95 CI)
0.378
8.404 <0.001
(0.35 – 0.406)
SD
β1
t
p
VIF
0.014
26.971 <0.001
0.015
0.644 15.478 <0.001 1.026
0.021
0.345
0.021
0.522 11.071 <0.001 1.316
0.021
0.501 10.643 <0.001 1.316
50
µm*
Particle
-5.259
110
µm
(-18.023 – 7.506)
6.442 -0.052 -0.816
0.416
1.026
0.238
(0.207 – 0.268)
1-bar*
82.592
1.5bar
(65.309 – 99.875)
Pressure
2-bar
49.36
(32.077 – 66.642)
88.967
2.5bar
(71.684 – 106.25)
8.723
0.686
9.469 <0.001 1.316
8.723
0.410
5.659 <0.001 1.316
8.723
0.739 10.200 <0.001 1.316
0.152
(0.111 – 0.193)
0,23
(0.189 – 0.271)
0.221
(0.18 – 0.262)
7.330 <0.001 1.316
*Reference parameter. aF=34.637, p<0.001; R2=0.553, Adjusted R2=0.537; bF=120.233, p<0.001; R2=0.811, Adjusted R2=0.804, β0: Standardized
beta coefficient, β1: Nonstandardized beta coefficient, SD: Standard deviation.
Table 4. Failure mode evaluation results of the specimens.
Adhesive
Cohesive
(Veneering
resin)
Cohesive
(PEEK)
CN
12
-
-
50A
10
2
-
50B
1
11
-
50C
9
2
1
50D
6
6
-
110A
12
-
-
110B
10
2
-
110C
9
3
-
110D
2
10
-
Groups
Mix
None
DISCUSSION
The first and second null hypotheses, that different particle
sizes and application pressures would not affect the SBS of
the PEEK bonded to the indirect veneer composite resin or
the surface roughness data (Ra), were rejected in line with the
results of the study.
EJPRD
Like previous studies that tested different alumina particle
sizes and application pressures,14,18 increased pressure increased the SBS values in the current study. Regardless of particle size, the specimens abraded at 1-bar pressure exhibited
lower numerical SBS values than other groups in agreement
with previous studies. However, this numerical difference did
not create a statistical difference. Also, the application of 50µm particles at a pressure of 1.5 bar showed higher numerical SBS results than 110-µm particles at 1.5-, 2-, and 2.5-bar
application pressures, and 50-µm particles at 2- and 2.5-bar
application pressures. While these numerical differences
caused a statistical difference between some groups, they
did not create a statistical difference between other groups.
Although the Ra values were numerically higher in the specimens abraded with 110-µm particles at 1.5-, 2, and 2.5-bar
pressures and with 50-µm particles at 2-bar pressure, the SBS
results were numerically lower than those of the specimen
prepared with 50-µm particles at 1.5-bar pressure. Similar to
the SBS results, the numerical differences observed in terms
of Ra did not cause a statistical difference for each group. On
the other hand, the changes in SBS values positively correlated with the Ra according to the results of the correlation
analysis performed in the current study (r=0.441, p<0.001).
Many factors, such as the amount of substrate, viscosity and
molecular weight of the adhesive agent and veneering composite, and the penetration capacity of the adhesive materials, affect the bonding between materials.5 Micromechanical locking,
which is provided by the penetration of the bonding agent into
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
ejprd.org - Published by Dennis Barber Journals.
Copyright ©2024 by Dennis Barber Ltd. All rights reserved.
P5
ARTICLE IN PRESS
European Journal of Prosthodontics and Restorative Dentistry Feb 21 2024
Figure 1: SEM images at 1000× magnification of PEEK after air-borne particle abrasion with different Al2O3 particle sizes and different
application pressures. A) CN group. B) 50A group. C) 50B group. D) 50C group. E) 50D group. F) 110A group. G) 110B group. H) 110C
group. I) 110D group.
the microporosity, is an important factor in strengthening the
adhesion between PEEK and resin materials.14,18,19 For this reason, the different SBS values obtained in this study may be due
to the differences in particle size and application pressure and
the penetration capacity of the visio.link adhesive material into
the microporous areas. In addition, although surface roughness values increased in some of the study groups, the changes
in SBS values did not correlate with the Ra since the visio.link
adhesive material could not reach the same penetration depth.
In contrast, after applying high pressure, the roughness of
the specimen surfaces will increase, and the bond strength
will increase accordingly. However, the increase in pressure
may negatively affect the SBS by causing the alumina particles to be more easily embedded in the treated surface structure.5,14,18 After the pre-treatment, in addition to the non-homogeneous roughness on the surface of the PEEK specimens
in the SEM images of the current study, embedded alumina
particles were also observed on some surfaces. In particular,
the number of alumina particles embedded in the surface
increased in the 2.5-bar pressure group (50D) compared to
the other groups abraded with 50-µm particles. This increase
P6
led to a decrease in SBS values in the 2.5-bar pressure group
(50D) compared to the 1.5-bar pressure group (50B), which presented the highest values among the specimens abraded with
50-µm particles. These results were similar to the results of
Silthampitag et al.,14 in which similar particle sizes and pressures (50 μm and 2 bar) were tested. Similar to the present
study, irregular cracked grooves and crack patterns were
observed in the SEM images, and it was concluded that air
abrasion generally caused Al2O3 to be embedded in the PEEK
surface. The increased pressure may further increase this effect and embedding Al2O3 particles in the PEEK surface may
negatively affect the bonding capacity.14
Bond strength is also associated with surface oxygen concentration, surface roughness, and wettability.7 In this study,
it was assumed that increasing SBS values following air-borne
particle abrasion with increasing application pressures led
to a higher wettability by increasing the surface roughness,
which in turn increased the bond strength. This finding was
also supported by SEM images showing increased surface
roughness and crater formation (especially in the 110-µm
groups) when compared with the surface properties of the
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
ejprd.org - Published by Dennis Barber Journals.
Air-Abrasion Effect on Bond of PEEK to Composite...
Copyright ©2024 by Dennis Barber Ltd. All rights reserved.
ARTICLE IN PRESS
low-pressure groups in terms of increased particle size or applied pressure. Although more studies are needed to confirm
the present results, the combinations of 50-µm particles with
1.5-bar pressure, 50-µm particles with 2.5-bar pressure, 110µm particles with 1.5-bar pressure, and 110-µm particles with
2.5-bar pressure are suitable for increasing the bonding properties of the PEEK to the indirect veneering resin.
In previous studies investigating the bond strength, lower
SBS values were observed in the specimens where adhesive
material was applied without air-borne particle abrasion (similar to the CN group).7,11,12,17 However, even in the CN group,
the SBS was 11.24 ± 3.6 MPa. Considering the results of previous studies on adhesive materials, this result may be due to
2-propenoic acid reaction products with pentaerythritol-triacrylate (PETIA) in the visio.link adhesive material, which has
been reported to significantly affect PEEK surface activation
while bonding to the dimethacrylate polymer.4,9-11,15 This finding led to the expectation that the dominant failure type in the
CN group would be adhesive rupture of the interface, and the
study results supported this expectation.
In addition, as in previous studies,16 the most common failure type observed in this study was adhesive failure between
the PEEK and the indirect resin material bond surface (62.5%).
It is not unexpected that groups featuring lower SBS values
will solely experience adhesive failure, owing to a weak interface connection. It has been determined that with an increase
in SBS values, cohesive fractures are observed, specifically
within the resin structure, in conjunction with adhesive failure. As the strength of the bond increases, it is common to
observe cohesive fracture in the resin material. This is due to
the fact that the resin material has a lower fracture strength
when compared to the PEEK material. In a recent study, cohesive failure in the resin material was found to be the most
common type of failure in groups 50B and 110D, which exhibited the highest SBS data. The results of the study indicate that
when PEEK is combined with additional restorative materials
that possess high bond strength, there is a risk of failure in the
material that has lower fracture strength. This finding could
serve as a valuable resource for clinicians, enabling them to
anticipate complications that may occur during the clinical
use of the material, and subsequently plan for the appropriate solution to such complications.
Determination of Ra following the air-borne particle abrasion
procedures allowed accurate identification of the specimen
surfaces in terms of the effectiveness of the surface activation
by the adhesive materials.7 In this study, the analysis of the Ra
and the examination of the surfaces with SEM imaging helped
interpret the SBS results. Thus, a better analysis of the parameters (particle size, pressure type, or adhesive material) that
can be used to increase the bond strength on the sample surfaces is provided.7 Correct analysis of these evaluated parameters will also be beneficial in shaping future study designs.
EJPRD
European Journal of Prosthodontics and Restorative Dentistry Feb 21 2024
In this study, a thermal aging protocol was applied, which
aimed to imitate the changes in the oral environment during
eating, drinking, and breathing with 5000 cycles between 5
°C and 55 °C.20,21 However, there have been studies reporting that the current procedure may cause microcracks in the
material and bond surfaces, volumetric changes resulting in
weakening of the chemical bonding, and stress, in addition to
not affecting or increasing the bond strength.11,22,23 In short,
conflicting results have been reported for the effect of thermal cycling on bond strength for PEEK. The first limitation of
the current study was that there is no additional control group
that was not aged, so no result isolating the effect of the aging protocol has been obtained. There is a definite need for
further and comprehensive studies investigating the effect of
artificial aging on chemical binding to PEEK substrates in this
controversial area.
In increasing the bond strength between the PEEK and the
veneering resin composite materials, air-borne particle abrasion can be an effective pre-treatment in terms of cost, time,
ease of access, and applicability. The application of suitable
adhesive materials, in addition to the pretreated surfaces, is
critically important. Since the current study tested the combination of the visio.link adhesive material most commonly
used in laboratory applications with PEEK, as well as the specific particle size and application pressure, additional studies
are needed to improve on the current results. In addition to
the study groups, only the negative control group, designated
as the no pre-treatment group, was tested in this study. It may
be recommended to include more clinical application scenarios in the methodology to determine the method to be used as
a positive control group in future studies. For example, testing
another innovative dental material in terms of SBS values may
help to better understand the bond strength limits of PEEK
material. Therefore, including such materials as a positive
control group in future studies may increase the importance
of the study results.
Although positive correlation was detected between SBS
and Ra in the current study, the fact that the numerical differences detected in SBS and Ra values did not create a statistical difference for each group is a finding that should be
taken into consideration. Increasing the power of the study
and the number of samples may cause the existing numerical
data to change and this change to be reflected as a statistical
difference. Therefore, methodological changes in sample size
and statistical power of the study may be planned in future
studies. The in vitro design of this study cannot fully simulate
the intraoral clinical situation. With the current study design,
preliminary information can be given to the clinician regarding the possibilities required to achieve ideal bonding to the
PEEK. To reach more general conclusions, all scenarios tested
in vitro should be evaluated with long-term clinical studies.
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
ejprd.org - Published by Dennis Barber Journals.
Copyright ©2024 by Dennis Barber Ltd. All rights reserved.
P7
ARTICLE IN PRESS
European Journal of Prosthodontics and Restorative Dentistry Feb 21 2024
CONCLUSION
Deposition parameters of the air-borne particle abrasion procedure and the selection of the adhesive material for surface
conditioning are critical in obtaining improved bond strength.
In order to increase the adhesion between the PEEK and the
indirect resin composite and obtain stronger bonds, the combination of visio.link with the pre-treatment option of air-borne
particle abrasion with 50 µm Al2O3 particles at 1.5-bar pressure
was shown to be a successful option. The SBS values are affected by alumina particle size and applied pressure. High application pressures can cause alumina particles (Al2O3) to be
embedded in the PEEK surface, reducing the bond strength.
ACKNOWLEDGEMENTS
The study was approved by the Medical Ethics Committee of Pamukkale University (Approval number: 60116787020/54320 and 60116787-020/328882).
DECLARATION OF CONFLICTING INTERESTS
The authors declared that there is not any conflict of interest
and financial interest in the companies are included in this
article.
FUNDING
The authors declared that there is not any financial interest
in the companies included in this article.
AUTHOR CONTRIBUTIONS
Conceptualization: Sahin SC; Methodology: Sahin SC, MutluSagesen L; Formal analysis: Sahin SC, Mutlu-Sagesen L; Investigation: Sahin SC, Mutlu-Sagesen L, Karaokutan I; Özcan M, Writing-original draft preparation: Sahin SC; Writing- review, editing
and discussion: Mutlu-Sagesen L, Karaokutan I., Özcan M.
REFERENCES
1. Alexakou, E., Damanaki, M., Zoidis, P., et al. PEEK high performance polymers: A review of properties and clinical applications in prosthodontics
and restorative dentistry. Eur J Prosthodont Restor Dent 2019; 27:113–121.
2. Stawarczyk, B., Beuer, F., Wimmer, T., et al. Polyetheretherketone– A
suitable material for fixed dental prostheses? J Biomed Mater Res Part
B Appl Biomater 2013; 101:1209–1216.
3. Qin, L., Yao, S., Zhao, J., et al. Review on development and dental applications of polyetheretherketone-based biomaterials and restorations.
Materials (Basel) 2021; 14:1–25.
4. Stawarczyk, B., Taufall, S., Roos, M., Schmidlin, P.R. and Lümkemann, N.
Bonding of composite resins to PEEK: the influence of adhesive systems
and air-abrasion parameters. Clin Oral Investig 2018; 22:763–771.
5. Lümkemann, N., Strickstrock, M., Eichberger, M., Zylla, I.M. and Stawarczyk ,B. Impact of air-abrasion pressure and adhesive systems on
bonding parameters for polyetheretherketone dental restorations. Int
J Adhes Adhes 2018; 80:30–38.
P8
6. Schmidlin, P.R., Stawarczyk, B., Wieland, M., Attin, T., Hämmerle, C.H.F.
and Fischer, J. Effect of different surface pre-treatments and luting materials on shear bond strength to PEEK. Dent Mater 2010; 26:553–559.
7. Mayinger, F., Fiebig, M., Roos, M., Eichberger, M., Lümkemann, N. and
Stawarczyk, B. Bonding behavior between polyetheretherketone and
polymethylmethacrylate acrylic denture polymer. J Adhes Dent 2021;
23:145–158.
8. Gama, L.T., Duque, T.M., Özcan, M., Philippi, A.G., Mezzomo, L.A.M. and
Gonçalves, T.M.S.V. Adhesion to high-performance polymers applied in
dentistry: A systematic review. Dent Mater 2020; 36:e93–108.
9. Caglar, I., Ates, S.M. and Yesil Duymus, Z. An in vitro evaluation of the
effect of various adhesives and surface treatments on bond strength of
resin cement to polyetheretherketone. J Prosthodont 2019; 28:e342–349.
10. Keul, C., Liebermann, A., Schmidlin, P.R., Roos, M., Sener, B. and Stawarczyk, B. Influence of PEEK surface modification on surface properties and bond strength to veneering resin composites. J Adhes Dent
2014; 16:383–392.
11. Stawarczyk, B., Keul, C., Beuer, F., Roos, M. and Schmidlin, P.R. Tensile
bond strength of veneering resins to PEEK: impact of different adhesives. Dent Mater J 2013; 32:441–448.
12. Uhrenbacher, J., Schmidlin, P.R., Keul, C., et al. The effect of surface
modification on the retention strength of polyetheretherketone
crowns adhesively bonded to dentin abutments. J Prosthet Dent 2014;
112:1489–1497.
13. Rosentritt, M., Preis, V., Behr, M., Sereno, N. and Kolbeck, C. Shear
bond strength between veneering composite and PEEK after different
surface modifications. Clin Oral Investig 2015; 19:739–744.
14. Silthampitag, P., Chaijareenont, P., Tattakorn, K., Banjongprasert, C.,
Takahashi, H. and Arksornnukit, M. Effect of surface pretreatments on
resin composite bonding to PEEK. Dent Mater J 2016; 35:668–674.
15. Stawarczyk, B., Jordan, P., Schmidlin, .PR., et al. PEEK surface treatment
effects on tensile bond strength to veneering resins. J Prosthet Dent
2014; 112:1278–1288.
16. Younis, M., Unkovskiy, A., ElAyouti, A., Geis-Gerstorfer, J. and Spintzyk,
S. The effect of various plasma gases on the shear bond strength between unfilled polyetheretherketone (peek) and veneering composite
following artificial aging. Materials (Basel) 2019;12:1447.
17. Kern, M. and Lehman, F. Influence of surface conditioning on bonding
to polyetheretherketon (PEEK). Dent Mater 2012; 28:1280–1283.
18. Hallmann, L., Mehl, A., Sereno, N. and Hämmerle, C.H.F. The improvement of adhesive properties of PEEK through different pre-treatments.
Appl Surf Sci 2012; 258:7213–7218.
19. Cognard, J. Some recent progress in adhesion technology and science.
Comptes Rendus Chim 2006; 9:13–24.
20. Palmer, D.S., Barco, M.T. and Billy, E.J. Temperature extremes produced orally by hot and cold liquids. J Prosthet Dent 1992; 67:325–327.
21. Boehm, R.F. Thermal environment of teeth during open-mouth respiration. J Dent Res 1972; 51:75–78.
22. Liebermann, A., Wimmer, T., Schmidlin, P.R., et al. Physicomechanical
characterization of polyetheretherketone and current esthetic dental
CAD/CAM polymers after aging in different storage media. J Prosthet
Dent 2016; 115:321–328.
23. Fuhrmann, G., Steiner, M., Freitag-Wolf, S. and Kern, M. Resin bonding
to three types of polyaryletherketones (PAEKs)—Durability and influence of surface conditioning. Dent Mater 2014; 30:357–363.
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
ejprd.org - Published by Dennis Barber Journals.
Air-Abrasion Effect on Bond of PEEK to Composite...
Copyright ©2024 by Dennis Barber Ltd. All rights reserved.