Interplay between resin cements and surface-treated Poly-Ether-Ether-Ketone (PEEK): effect of aging

Abstract

Aim

This study assessed the effect of thermal aging on the interfacial strength of resin cements to surface-treated PEEK.

Methods

Ninety-six PEEK blocks were allocated into 4 groups (n=24), according to following surface treatments: SB - sandblasting with aluminum oxide; SA - acid etched with 98% sulfuric acid; CA – coupling agent (Visio.link, Bredent) and CO - control group (untreated). Surface roughness (Ra) was measured and one cylinder (1-mm diameter and height) of Rely-X Ultimate - ULT (3M/ESPE) and another one of Panavia V5 - PAN (Kuraray) were constructed on the treated or untreated PEEK surfaces. Half of the samples of each group were thermal aged (1,000 cycles). Samples were tested at a crosshead speed of 1 mm/min in shear mode (µSBS). Ra and µSBS data were compared using one- and three-way ANOVA, respectively, and Tukey’s tests.

Results

SA and SB samples had the roughest surfaces, while CA the smoother (p<0.001). Thermal aging reduced µSBS regardless the surface treatment and resin cement used. There was interaction between surface treatment and resin cement (p <0.001), with ULT showing higher µSBS values than PAN. SA provided higher µSBS than SB for both resin cements, while for CA µSBS was higher (PAN) or lower than SB (ULT).

Conclusion

Aging inadvertently reduces interfacial strength between PEEK and the resin cements. If ULT is the resin cement of choice, reliable interfacial strength is reached after any PEEK surface treatment. However, if PAN is going to be used only SA and CA are recommended as PEEK treatment.

Polymers; Resin cements; Shear strength; Aging

Introduction

Poly-ether-ether-ketone (PEEK) is a thermoplastic polymer with attractive properties such as low allergenic potential, non-metallic color, high polishing, wear resistance, lightness and reduced biofilm formation make it as an alternative to prosthetic and restorative materials¹,². In Dentistry, the clinical applications of PEEK include framework for fixed and removable prostheses, crowns, abutments, dental implants, occlusal guards, orthodontic wires, and posts²-⁴.

Despite its versatility, PEEK has low free energy and inert hydrophobic surface which pose challenges to bonding procedures to dental materials⁵-⁷. In order to increase surface energy and provide functional groups for improved bond strength with resin materials, as a previous step to bonding, PEEK surface has been subjected to physical or chemical treatments, including sulfuric acid etching, sandblasting, silica coating, coupling agent, laser and plasma⁴,⁸-¹¹. However, the bonding result depends not only on the PEEK surface treatment, but also on the adhesive or resin cement itself and on the interplay between surface-treated PEEK surface and adhesive/resin cement⁷,¹¹. These two later aspects are especially important if one considers the myriad of available adhesives and resin cements and their compositions, which can affect bonding to PEEK. One example are resin cements containing 10-methacryloxydecyl dihydrogen phosphate (10-MDP). Although such component contributes to the overall polymerization process of some resin cements, such as in Panavia V5, there are speculations that 10-MDP negatively affect bonding to PEEK due to its phosphate group, which does not react with PEEK¹².

The understanding of the interaction of surface-treated PEEK-resin cement is even more important if one considers that such materials face biochemical and physicomechanical degradation processes in the oral cavity. Factors including saliva, acidic conditions, temperature oscillations, and masticatory stresses may hinder the properties of resin cements over time. Aging by simulating oral conditions, such as thermocycling, has been used to anticipate the impact of degradation processes¹³. However, to the best authors’ knowledge, to date, the effect of thermal aging has been investigated between surface-treated PEEK and resin cement has only been investigated plasma-treated PEEK¹⁴, which is less tangible to the clinicians. As for the combination surface-treated PEEK/adhesive/composite system, chances are that the repetitive temperature changes could strain the interface between surface-treated PEEK and resin cement, and affect the bonding stability, which would have the influence of the composition of the resin cement.

Based on the aforementioned rationales, this study aimed to assess the effect of thermal aging on the interfacial strength between surface-treated PEEK and resin cements. We tested the null hypothesis that there would be no effect of surface treatment of PEEK, resin cement and thermal aging, neither alone nor interacting, on micro-shear bond strength (µSBS) between PEEK-resin cement.

Material and methods

Experimental design

This study had two parts. In Part One, the samples were 24 PEEK blocks whose surface was subjected to four different surface treatments as follows: 98% sulfuric acid etching (SA); sandblasting (SB); pentaerythritol triacrylate (PETIA)-containing coupling agent (CA, Visio.link, Bredent, Germany) and untreated control surface (CO). The dependent variable was surface roughness. In Part Two of this study samples of Part One were bonded to two dual-cure resin cements (RelyX Ultimate – ULT and Panavia V5 - PAN, Table 1) and unaged or aged using thermocycling. The dependent variable was µSBS.

Table 1
Description of the resin cements.

Characteristics	RelyX Ultimate (ULT)	Panavia V5 (PAN)
Monomers	Base paste: methacrylate monomers catalyst paste: methacrylate monomers	Paste A: Bis-GMA, TEGDMA, hydrophobic aromatic dimethacrylate, hydrophilic aliphatic dimethacrylate paste B: Bis-GMA, hydrophobic aromatic dimethacrylate, hydrophilic aliphatic dimethacrylate
Inorganic fillers	43% by volume silanized filler particles, alkaline filler particles size: 13 µm	38% by volume silanized barium glass particles, silanized fluoralminosilicate glass particles, colloidal silica, silanized aluminum oxide particles size: 0.01-12 µm
Initiators	Sodium p-toluenesulfonate, sodium persulfate, terc.butil 3,5,5-trimethylperoxyhexanoate	dl-camphorquinone
Shade	A1	Clear
Manufacturer, batch #	3M/ESPE; 4471448	Kuraray; 000001

• Bis-GMA: bisphenol A-glycidyl methacrylate; TEGDMA: triethylene glycol dimethacrylate.

Based on a pilot study, in which the effect size was 0.183, a total of 21 samples per group would be required to detect significant difference, at 5% significance level and 80% of power. Three samples were added in each group in order to compensate for eventual sample loss due to premature failure during thermocycling. Each group had therefore 24 samples.

Part one – sample preparation, surface treatment, surface roughness evaluation and AFM imaging

Using a milling system (CNC Discovery D600, Indústrias Romi SA, Brazil), 96 PEEK blocks (MGM Plásticos de Engenharia, Brazil) were machined to 10x10x5.5 mm. PEEK blocks were then randomly allocated into four groups (n = 24) to receive one of the following surface treatments:

SA: 200 µl of 98% sulfuric acid etching (ECIBRA/CETUS, Brazil) for 60 s¹¹, followed by immersion in distilled water for 15 s to stop the chemical reaction and rinsing with distilled water for 15 s;

SB: sandblasting with aluminum oxide particles¹¹ (average particle size: 125 µm) for 20 s under 3 Bar (pressure), at an angle of 45 degrees and 10 mm-distance between the surface and the nozzle (Sandblaster Basic Master and Cobra, Renfert, Germany), and rinsing with distilled water for 15 s;

CA: application of PETIA-containing coupling agent¹¹ (Visio.link, Bredent, Germany), using a Microbrush® applicator and light-curing for 90 s (Valo, Ultradent Products, USA);

CO: Control (untreated surface).

After the surface treatments, PEEK blocks were measured for average surface roughness (Ra) using a profilometer (Mitutoyo SJ210, Mitutoyo Sul Americana Ltda, Brazil). The cut-off was set at 0.25 mm and total transverse length was 1.25 mm. Measurements were made in three different directions (0, 45 and 90^o) of the sample.

Representative images of surface-treated-samples were obtained under atomic force microscopy (Dimension® Icon AFM System with ScanAsyst®, Bruker Nano Surfaces Division, USA), operating in intermittent mode, with a scanning area of 2x2 µm.

Part two – fabrication and bonding of resin cement cylinders, thermal aging, µSBS testing and failure mode examination

Directly on the surface of each sample, two translucent Tygon tubes with an internal diameter of 1.0 mm¹⁵ and a height of 1.0 mm were used as matrices. One trained operator using magnifying loupes (Galilean HD 3.3, ExamVision, Denmark) positioned the matrices on the PEEK surface. The resin cements ULT e PAN were mixed according manufacturers’ direction. Each matrix carefully received one of each resin cement. A Mylar strip was positioned over the filled tube and gently pressed. The resin cements were light-cured through the Mylar strip, according to the recommendations of each manufacturer: 20 s for ULT and 10 s for PAN, with the Valo curing light (Ultradent Products, USA) at standard power (1000 mW/cm²). Matrices were then carefully removed using a sharp blade to expose the resin cement cylinders. Each cylinder was examined using magnifying loupes to identify possible defects (bubbles and flow of resin cement beyond the limits of the bonding area). All the samples, formed by the PEEK surface and one cylinder of each resin cement, were stored in distilled water at 37ºC for 24 h and randomly allocated to be either thermal aged or remain unaged.

The samples thermal aged underwent 1,000 hydrothermal cycles in water between 5ºC and 55ºC, with 30 s dwell time (MCT, Elquip, Brazil).

The samples were mounted into a jig attached to a universal testing machine (DL 200, EMIC, Brazil). A 0.2-mm diameter orthodontic wire was looped around the base of the resin cement cylinder as close as possible to the PEEK-cylinder interface and a shear force was applied to cylinder (Figure 1) at a crosshead speed of 1 mm/min until failure occurred¹⁶. The µSBS values was calculated in megapascals (MPa) by dividing the load at failure point (newtons) by the surface area of the PEEK-resin cement bonding.

Figure 1
Schematic drawing of the sample tested for micro-shear bond strength (on the left) and the four different possible failure modes.

Fractured µSBS samples were then examined for their failure modes with a stereomicroscopic loupe (EK3ST, Eikonal Equip, Brazil) at 10X magnification and classified into: adhesive failure (between PEEK and resin cement), cohesive failure in PEEK, cohesive failure in the resin cement and mixed failure (Figure 1).

Statistical analysis

Due to the lack of normality, data were square-root transformed. One-way analysis of variance compared surface roughness data (Part One), while the effect of surface treatment, resin cement, thermocycling and their interactions (Part Two) were tested using three-way analysis of variance. All multiple comparisons were performed with Tukey’s test. The calculations were run on SPSS (SPSS Inc., USA), at a significance level of 5%.

Results

Surface pre-treatments significantly affected roughness (p < 0.001), with both SB and SA groups significantly rougher than CO, whereas CA presented the smoothest surface (Table 2). Figure 2 shows AFM images and revealed that CO samples (Figure 2D) had a primary texture featuring some grooves caused by the extrusion process after casting, whereas samples that received CA (Figure 2C) expressed a flat surface with a micellar aspect. The samples of SB group (Figure 2B), on the other hand, exhibited an irregular surface, with few and sparse pits, while those etched by SA (Figure 2A) had the surface changed to a spongy pattern with marked and wider depressions.

Table 2
Means and standard deviations of surface roughness (Ra, µm) of PEEK after different physical or chemical treatments.

Surface treatment	Surface roughness
SA	1.412 (0.546) C
SB	1.528 (0.140) C
CA	0.127 (0.073) A
CO	0.465 (0.107) B

• SA (98% sulfuric acid etching); SB (sandblasting with aluminum oxide particles);CA (PETIA-based coating agent - Visio.link). Groups followed by dissimilar capital letters differ from each other.

Figure 2
AFM images of PEEK etched with 98% sulfuric acid (A), sandblasted (B), subjected to coupling agent (C) and untreated (control, D).

Table 3 presents µSBS data which demonstrated no significant interaction among surface treatment, resin cement and thermal aging (p = 0.575), but a significant interaction was noticed between surface treatment and resin cement (p < 0.001). This interaction was explored using Tukeys’ test and showed that compared to SB, SA provided higher µSBS to both PAN and ULT resin cements. However, while for PAN no difference existed between the µSBS when PEEK surface received SA or CA, for ULT, CA resulted in lower µSBS values. Regardless of the surface pretreatment performed, ULT resulted in higher values of µSBS to PEEK (Table 4). As no other significant interaction was detected (surface treatment x thermal aging: p = 0.182; resin cement x thermal aging: p =0.458), then it was checked the effect of the main variable, which was shown to be statistically significant. Specifically, regardless of the surface treatment and resin cement used, thermal aging significantly reduced µSBS between resin cements and PEEK surface by 15.6%, [thermal unaged: 18.46 MPa (11.85 MPa); aged: 15.57 MPa (12.64 MPa)].

Table 3
Means and standard deviations (MPa) of bond strength between resin cements and surface-treated PEEK, unaged and thermal aged.

Surface treatment	Panavia V5 (PAN)		Rely-X Ultimate (ULT)
	Unaged	Thermal aged	Unaged	Thermal aged
SA	16.05 (11.91)	11.69 (10.33)	30.44 (8.83)	33.22 (11.62)
SB	3.43 (2.76)	5.28 (10.07)	27.52 (7.97)	23.23 (5.77)
CA	14.44 (7.91)	7.18 (4.04)	18.89 (6.00)	12.51 (3.43)

• SB (sandblasting with aluminum oxide particles); SA (98% sulfuric acid etching); CA (PETIA-based coating agent - Visio.link). According to three-way analysis of variance: interaction among surface treatment x resin cement x thermal cycling (p = 0.575); interaction between surface treatment x resin cement: p < 0.001; interaction between surface treatment x thermal cycling: p = 0.182; interaction resin cement x thermal cycling: p = 0.458; main variable thermal cycling: p = 0.013).

Table 4
Bond strength means and standard deviations (MPa) between resin cements and PEEK subjected to different surface treatments, regardless whether thermal aged.

Surface treatment	Panavia V5 (PAN)	Rely-X Ultimate (ULT)
SA	13.96 Aa (11.16)	31.83 Ab (10.19)
SB	4.35 Ba (7.28)	25.38 Bb (7.15)
CA	10.81 Aa (7.17)	15.70 Cb (5.79)

• SA (98% sulfuric acid etching); SB (sandblasting with aluminum oxide particles); CA (PETIA-based coating agent - Visio.link). Means followed by different capital letters indicate difference among surface treatments within each column. Means followed by different lower-case letters indicate difference between resin cements within each row.

Adhesive failure was predominant in all groups. Mixed failures occurred in samples bonded with ULT but not with PAN. In samples that received CA pre-treatment, those thermal aged had adhesive failures only, while 8.33% of unaged samples had mixed failures. The same proportion of mixed failures was seem in the SA pre-treated group that was unaged. Still in unaged samples, 16.6% of SB group samples had mixed failures. When thermal aged, SA and SB groups mixed failures occurred in 50,0% of 33.3% of the samples. Cohesive failure within PEEK occurred in a single sample (8.33%) pertaining to SA group (unaged).

Discussion

The findings of this study demand rejection of the null hypotheses as thermal aging and the interplay between surface treatment of PEEK and resin cement significantly affected µSBS values. The reasons why thermal aging reduced the µSBS values are twofold: a) causing water sorption and hydrolytic degradation at bonding interfaces and, b) causing thermal stress due to differences in the coefficient of thermal expansion and condutivity between PEEK and resin cement¹⁷,¹⁸.

Water sorption can plasticize, break hydrogen bonds within the resin matrix, cause polymer swelling and ultimately hinder the properties of resin cements¹⁷. Water sorption can also cause hydrolytic degradation of the resin matrix, the filler/matrix interface, or the filler. In effect, there are reports showing that both ULT and PAN present water sorption. ULT contains phosphoric acid modified methacrylate monomers, which have the capability to bind water at hydroxyl groups¹⁸. In addition, ULT has alkaline fillers, which bind water by starting an acid-base reaction¹⁸. PAN, on the other hand, presents water sorption because it contains hydrophilic aliphatic dimethacrylate, but as there are no phosphate/hydroxyl groups or alkaline fillers, water sorption has been shown to be reduced¹⁸. As a result, for both resin cements (ULT e PAN) thermocycling increases water sorption and solubility¹⁸.

Still with respect to the explanations why thermocycling reduced µSBS values in the current study, cyclic temperature changes can generate expansion and contraction stresses, leading to microcracks within the resin cement¹⁸. Such events can cause microcracks and thereby increase water sortion and solubility of resin cements¹⁸. However, stress can concurrently occur at the PEEK-resin cement interface, as the coefficient of thermal expansion of pure PEEK has been described to be half of resin cements such as ULT¹⁹,²⁰.

One can argue that a higher number of thermal cycles could better represent the long-term aging, especially because 10,000 cycles have been described to correspond to approximately one year of clinical service²¹ and higher numbers of thermal cycles have been described in PEEK experiments⁵. However, it is worth mentioning that in these publications the samples were prepared for shear bond testing not for µSBS, as used in the current paper⁵. Preliminary experiments of our group showed that 10,000 thermal cycles caused debonding of 92% of the samples during thermocycling. Even during 5,000 thermal cycles an extensive proportion of samples prematurely failed (67%). The explanation for debonding may be probably found in the aggravated action of temperature oscillations in the PEEK-resin cement interface, because of a lower bonding area in µSBS testing in comparison to the shear bond method. Thus, in order to have minimal premature failure and make it feasible to mearure µSBS values, we run 1,000 cycles.

Interesting to notice is that previous literature data in which the authors thermocycled ULT 10,000x the bond strength of this resin cement was reduced in 14.7%²², an amount equivalent to that observed in our study (15.6%) using 1,000 thermal cycles. This similar reduction despite the different number of thermal cycles may be ascribed to the fact that in the cited paper the bonding area was increased and samples were tested in tensile rather than microtensile mode.

Besides the effect of thermal aging, surface treatment also played a role on µSBS values. Regardless of the resin cement, SA provided higher µSBS than SB. Figures 1A and 1B substantiate this finding showing, respectively, marked versus sparse pits on the PEEK surface. The effect of SA stems from the cleavage of benzene rings by attacking PEEK carbonyl and ether groups and the introduction of sulfonic acid groups in the PEEK polymer chains²³,²⁴. A micromorphological change is generated, but probably in a range not significantly different from SB in terms of Ra values, in accordance with a previous study²⁵. However, other papers have indicated that SB promotes smoother²⁶ or rougher surface than SA²⁷-²⁹. Such differences may be attributed to variation in the size of aluminum oxide particles, the pressure and duration of blasting³⁰,³¹. In effect, in the present study, the pressure used during blasting was higher than that used in some previous studies⁷,³². The pressure of 3 Bar was chosen in an attempt to achieve greater bond strength, since it has been reported that PEEK bond strength is enhanced by increasing blasting pressure²⁸,³³. However, bonding to sandblasted or any pretreated surface proved to be dependent on the resin cement used, as PAN systematically provided lower µSBS than ULT. This result substantiates the speculation that 10-MDP present in PAN can negatively affect bonding to PEEK is correct.

In this regard, however, it is relevant to verify whether the µSBS values reached the 10 MPa threshold, considered as a clinically acceptable value in a number of published papers as cited elsewhere¹⁰. Our data showed that in only one combination of surface treatment (SB) and resin cement (PAN) the µSBS was below the 10 MPa threshold. Despite the proximity between the average µSBS and the 10-MPa threshold, the combination between CA as a pretreatment for PEEK and PAN as the resin cement is electable. CA (Figure 2C) created a surface with micellar aspect promoted by the chemical interaction between PEEK and methylmethacrylate (MMA) and PETIA¹² that constitutes the coupling agent (Visio.link). However, the efficiency of such interaction has been significantly higher following air abrasion and sulfuric acid etching¹¹.

It is noteworthy noting that in a previous study that tested PEEK bonded to titanium bases showed that the weaker interface was between the PEEK and a resin cement³⁴. This finding validates the importance of the present paper in further explores the interfacial strength between PEEK and different resin cements, especially under aging. However, one should bear in mind that in continuation to this study, it would be valuable to test whether or not the bonding capacity of resin cements to PEEK and its longevity would hold when resin cements are sandwiched between PEEK and dental substrates (or composite resins). This set up would be feasible through micro-tensile testing. If possible obtaining micro-tensile samples using resin cements sandwiched between PEEK and other substrates, the results would allow gaining additional insights into the predictability of the interfacial strength under clinical circumstances involving PEEK usage.

Based on the current findings, thermal aging reduced the interfacial strength between PEEK and resin cements, but if ULT is the resin cement of choice, reliable interfacial strength is reached after any PEEK surface treatment. However, if PAN is going to be used only SA and CA are recommended as PEEK treatment.

References

• ¹
  Blanch-Martínez N, Arias-Herrera S, Martínez-González A. Behavior of polyether-ether-ketone (PEEK) in prostheses on dental implants. A review. J Clin Exp Dent. 2021;13:e520-6. doi: 10.4317/jced.58102.
• ²
  Papathanasiou I, Kamposiora P, Papavasiliou G, Ferrari M. The use of PEEK in digital prosthodontics: a narrative review. BMC Oral Health. 2020 Aug;20(1):217. doi: 10.1186/s12903-020-01202-7.
• ³
  Nahar R, Mishra SK, Chowdhary R. Evaluation of stress distribution in an endodontically treated tooth restored with four different post systems and two different crowns- A finite element analysis. J Oral Biol Craniofac Res. 2020 Oct-Dec;10(4):719-26. doi: 10.1016/j.jobcr.2020.10.004.
• ⁴
  Qin L, Yao S, Zhao J, Zhou C, Oates TW, Weir MD, et al. Review on development and dental applications of polyetheretherketone-based biomaterials and restorations. Materials (Basel). 2021 Jan;14(2):408. doi: 10.3390/ma14020408.
• ⁵
  Gama LT, Duque TM, Özcan M, Philippi AG, Mezzomo LAM, Gonçalves TMSV. Adhesion to high-performance polymers applied in dentistry: A systematic review. Dent Mater. 2020 Apr;36(4):e93-e108. doi: 10.1016/j.dental.2020.01.002.
• ⁶
  Bathala L, Majeti V, Rachuri N, Singh N, Gedela S. The role of polyether ether ketone (PEEK) in dentistry: a review. J Med Life. 2019 Jan-Mar;12(1):5-9. doi: 10.25122/jml-2019-0003.
• ⁷
  Tsuka H, Morita K, Kato K, Kawano H, Abekura H, Tsuga K. Evaluation of shear bond strength between PEEK and resin-based luting material. J Oral Biosci. 2017;59(4):231-6. doi: 10.3290/j.jad.b2288283.
• ⁸
  Rocha RF, Anami LC, Campos TM, Melo RM, Souza RO, Bottino MA. Bonding of the polymer polyetheretherketone (PEEK) to human dentin: effect of surface treatments. Braz Dent J. 2016 Oct-Dec;27(6):693-9. doi: 10.1590/0103-6440201600796.
• ⁹
  Parkar U, Dugal R, Madanshetty P, Devadiga T, Khan AS, Godil A. Assessment of different surface treatments and shear bond characteristics of poly-ether-ether-ketone: An in vitro SEM analysis. J Indian Prosthodont Soc. 2021 Oct-Dec;21(4):412-9. doi: 10.4103/jips.jips_199_21.
• ¹⁰
  Escobar M, Souza JCM, Barra GMO, Fredel MC, Özcan M, Henriques B. On the synergistic effect of sulfonic functionalization and acidic adhesive conditioning to enhance the adhesion of PEEK to resin-matrix composites. Dent Mater. 2021 Apr;37(4):741-54. doi: 10.1016/j.dental.2021.01.017.
• ¹¹
  Soares Machado P, Cadore Rodrigues AC, Chaves ET, Susin AH, Valandro LF, Pereira GKR, et al. Surface treatments and adhesives used to increase the bond strength between polyetheretherketone and resin-based dental materials: a scoping review. J Adhes Dent. 2022 May;24(1):233-45. doi: 10.3290/j.jad.b2288283.
• ¹²
  Keul C, Liebermann A, Schmidlin PR, Roos M, Sener B, Stawarczyk B. Influence of PEEK surface modification on surface properties and bond strength to veneering resin composites. J Adhes Dent. 2014 Aug;16(4):383-92. doi: 10.3290/j.jad.a32570.
• ¹³
  Morresi AL, D'Amario M, Capogreco M, Gatto R, Marzo G, D'Arcangelo C, et al. Thermal cycling for restorative materials: does a standardized protocol exist in laboratory testing? A literature review. J Mech Behav Biomed Mater. 2014 Jan;29:295-308. doi: 10.1016/j.jmbbm.2013.09.013.
• ¹⁴
  Stawarczyk B, Bähr N, Beuer F, Wimmer T, Eichberger M, Gernet W, et al. Influence of plasma pretreatment on shear bond strength of self-adhesive resin cements to polyetheretherketone. Clin Oral Investig. 2014 Jan;18(1):163-70. doi: 10.1007/s00784-013-0966-7.
• ¹⁵
  Armstrong S, Geraldeli S, Maia R, Raposo LH, Soares CJ, Yamagawa J. Adhesion to tooth structure: a critical review of "micro" bond strength test methods. Dent Mater. 2010 Feb;26(2):e50-62. doi: 10.1016/j.dental.2009.11.155.
• ¹⁶
  Muñoz MA, Baggio R, Mendes YBEM, Gomes GM, Luque-Martinez I, Loguercio, AD, et al. The effect of loading method and cross-head speed on resindentin microshear bond strength. Int J Adhes Adhes. 2014 Apr;50:136-41. doi: 10.1016/j.ijadhadh.2014.01.024.
• ¹⁷
  Walker MP, Spencer P, David Eick J. Mechanical property characterization of resin cement after aqueous aging with and without cyclic loading. Dent Mater. 2003 Nov;19(7):645-52. doi: 10.1016/s0109-5641(03)00008-3.
• ¹⁸
  Müller JA, Rohr N, Fischer J. Evaluation of ISO 4049: water sorption and water solubility of resin cements. Eur J Oral Sci. 2017 Apr;125(2):141-50. doi: 10.1111/eos.12339.
• ¹⁹
  Goyal RK, Tiwari AN, Mulik UP, Negi YS. Thermal expansion behaviour of high performance PEEK matrix composites. J Phys D: Appl Phys. 2008 Mar;41(8):085403. doi: 10.1088/0022-3727/41/8/085403.
• ²⁰
  Cakan U, Saygili G. Comparison of thermal stress on various restorative post and core materials generated by oral temperature changes using three dimensional finite element analysis. Clin Dent Res. 2015;39(1):27-35.
• ²¹
  Gale MS, Darvell BW. Thermal cycling procedures for laboratory testing of dental restorations. J Dent. 1999 Feb;27(2):89-99. doi: 10.1016/s0300-5712(98)00037-2.
• ²²
  Correr-Sobrinho L, Costa AR, Fugolin APP, Sundfeld Neto D, Ferracane JL, Pfeifer CS. Effect of experimental resin cements containing thio-urethane oligomers on the durability of ceramic-composite bonded interfaces. Biomater Investig Dent. 2019 Nov 27;6(1):81-9. doi: 10.1080/26415275.2019.1693274.
• ²³
  Stawarczyk B, Jordan P, Schmidlin PR, Roos M, Eichberger M, Gernet W, et al. PEEK surface treatment effects on tensile bond strength to veneering resins. J Prosthet Dent. 2014 Nov;112(5):1278-88. doi: 10.1016/j.prosdent.2014.05.014.
• ²⁴
  Yee RSL, Zhang K, Ladewig BP. The effects of sulfonated poly (ether ether ketone) ion exchange preparation conditions on membrane properties. Membranes. 2013 Aug;3(3):182-95. doi: 10.3390/membranes3030182.
• ²⁵
  Silthampitag P, Chaijareenont P, Tattakorn K, Banjongprasert C, Takahashi H, Arksornnukit M. Effect of surface pretreatments on resin composite bonding to PEEK. Dent Mater J. 2016;35(4):668-74. doi: 10.4012/dmj.2015-349.
• ²⁶
  Rosentritt M, Preis V, Behr M, Sereno N, Kolbeck C. Shear bond strength between veneering composite and PEEK after different surface modifications. Clin Oral Investig. 2015 Apr;19(3):739-44. doi: 10.1007/s00784-014-1294-2.
• ²⁷
  Çulhaoglu AK, Özkir SE, Sahin V, Yilmaz B, Kiliçarslan MA. Effect of various treatment modalities on surface characteristics and shear bond strengths of polyetheretherketone-based core materials. J Prosthodont. 2020 Feb;29(2):136-41. doi: 10.1111/jopr.12702.
• ²⁸
  Stawarczyk B, Beuer F, Wimmer T, Jahn D, Sener B, Roos M, et al. Polyetheretherketone - A suitable material for fixed dental prostheses? J Biomed Mater Res - Part B Appl Biomater. 2013 Oct;101(7):1209-16. doi: 10.1002/jbm.b.32932.
• ²⁹
  Adem N, Bal B, Kazazoglu E. Comparative study of chemical and mechanical surface treatment effects on the shear bond strength of polyether-ether-ketone to veneering resin. Int J Prosthodont. 2022 March/April;35(2):201-7. doi: 10.11607/ijp.6938.
• ³⁰
  Ourahmoune R, Salvia M, Mathia TG, Mesrati N. Surface morphology and wettability of sandblasted PEEK and its composites. Scanning. 2014 Jan-Feb;36(1):64-75. doi: 10.1002/sca.21089.
• ³¹
  Elawadly T, Radi WIA, El Khadem A, Osman RB. Can PEEK be an implant material? Evaluation of surface topography and wettability of filled versus unfilled PEEK with different surface roughness. J Oral Implantol. 2017 Dec;43(6):456-61. doi: 10.1563/aaid-joi-D-17-00144.
• ³²
  Tsuka H, Morita K, Kato K, Kimura H, Abekura H, Hirata I, et al. Effect of laser groove treatment on shear bond strength of resin-based luting agent to polyetheretherketone (PEEK). J Prosthodont Res. 2019 Jan;63(1):52-7. doi: 10.1016/j.jpor.2018.08.001.
  » https://doi.org/10.1016/j.jpor.2018.08.001
• ³³
  Stawarczyk B, Taufall S, Roos M, Schmidlin PR, Lümkemann N. Bonding of composite resins to PEEK: the influence of adhesive systems and air-abrasion parameters. Clin Oral Investig. 2018 Mar;22(2):763-71. doi: 10.1007/s00784-017-2151-x.
• ³⁴
  Yilmaz B, Gouveia D, Schimmel M, Lu WE, Özcan M, Abou-Ayash S. Effect of adhesive system, resin cement, heat-pressing technique, and thermomechanical aging on the adhesion between titanium base and a high-performance polymer. J Prosthet Dent. 2022 May 2;S0022-3913(22)00207-4. doi: 10.1016/j.prosdent.2022.03.026.

• Data availability
  Datasets related to this article will be available upon request to the corresponding author.

Edited by

Editor: Altair A. Del Bel Cury

Data availability

Data availability

Datasets related to this article will be available upon request to the corresponding author.

Publication Dates

• Publication in this collection
  26 Apr 2024
• Date of issue
  2023

History

• Received
  15 June 2022
• Accepted
  31 Aug 2022