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Article

Flexural Behavior of Biocompatible High-Performance Polymer Composites for CAD/CAM Dentistry

by
Hanin E. Yeslam
Department of Restorative Dentistry, Faculty of Dentistry, King Abdulaziz University, P.O. Box 80209, Jeddah 21589, Saudi Arabia
J. Compos. Sci. 2023, 7(7), 270; https://doi.org/10.3390/jcs7070270
Submission received: 5 June 2023 / Revised: 24 June 2023 / Accepted: 28 June 2023 / Published: 30 June 2023
(This article belongs to the Special Issue Innovations in Direct and Indirect Dental Composite Restorations)
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Abstract

:
High-performance polymeric materials have been used in computer-assisted design/ computer-assisted milling (CAD/CAM) dental restorative treatments due to their favorable esthetics as well as their mechanical and biological properties. Biocompatible poly-ether-ether-ketone (PEEK) and glass-fiber-reinforced composite techno-polymer (FRC) resins reportedly possess good flexural and shock absorption properties. However, intraoral thermal fluctuations may adversely affect them. This study aimed to investigate the flexural strength and effect of thermal aging on two commercially available high-performance polymers intended for CAD/CAM milled frameworks for definitive restorations. A total of 20 bar specimens were prepared using two CAD/CAM materials (n = 10); PEEK(P) and Bioloren FRC(F). Specimens from each material group were randomly divided into two sub-groups (n = 5): before aging (uP and uF) and after aging, with 10,000 thermocycles (5–55 °C) (aP and aF). All specimens were subjected to a three-point bending test in a universal testing machine. Flexural strength (Fs) values were calculated for all specimens, and their means were statistically analyzed using a t-test, and a general linear model (GLM) repeated measure ANOVA (p < 0.05). There was a statistically significant decrease in the Fs of (F) materials after aging (p = 0.03). (F) specimens exhibited significantly higher Fs than (P) before and after aging (p < 0.001). This type of material had a significant effect on Fs (p < 0.001). Within the limitations of this study, both materials exceeded the ISO recommendations of dental resins for flexural strength. However, FRC materials may benefit CAD/CAM milled long-span fixed partial dentures and implant-supported denture frameworks.

1. Introduction

Since their development in the 1960s, dentists have been utilizing high-molecular-weight epoxy and methacrylate-based resins [1,2]. While metal-based restorative materials are strong and durable, they pose risks, negative biological responses, poor esthetics, and unfavorable thermal conductivity [3,4,5]. Tooth-colored polymeric materials for dental restorations have better thermal insulation than metals but can release free monomers and have weaker strength and lower durability [6,7]. Thus, the focus is on developing new polymeric resins and biopolymers with enhanced biocompatibility, long-term durability, repairability, and esthetic qualities [8,9]. Restoring teeth with dental materials can be challenging due to intraoral factors such as biofilm, mechanical stress, and changes in temperature [10,11]. These factors could reduce the durability of dental restorations by adversely affecting their mechanical and esthetic properties.
Digital technology has revolutionized restorative dental care, with computer-assisted design/computer-assisted milling (CAD/CAM) technology now used to create reliable dental restorations [12]. The demand for faster and safer dental care and treatments has risen with technological advancements. This led to the increased popularity of digital dental treatments, such as CAD/CAM, which require less time in the dentist’s chair and fewer appointments. Both dental practitioners and patients have found these options to be more appealing [13]. CAD/CAM allows the innovation of new restorative materials that can debatably be used as an alternative to strong ceramic materials [14]. The polymeric materials utilized in CAD/CAM technology are produced under optimal conditions that ensure high-quality control and conversion rates. This results in materials with excellent properties, including biocompatibility, structural and aesthetic durability, and excellent mechanical strength. These materials, which are generally milled into dental restorations using CAD/CAM technology, are also free of methyl methacrylate (MMA) and provide both functional and aesthetic benefits [15,16].
Dental biopolymers are used in a wide range of restorative dental applications, including the treatment and/or replacement of body structures and functions [14]. High-performance reinforced composites used in other fields, such as aerospace engineering and medicine, were obtained for use in dentistry [17]. Fiber-reinforced ceramics (FRCs) are polymers with dispersed fiber such as glass, that increases the strength and distributes the stress [14,18]. Recently introduced materials; Trilor (Bioloren S.r.l, Saronno, Italy), a tooth-colored high-performance biocompatible FRC with multidirectional glass-fibers, is indicated for the CAD/CAM fabrication of RPDs and full arch implant-supported prosthesis due to its good flexural properties. Due to its bone-like resilience, it is also indicated for the milling of frameworks for esthetic tooth and implant-supported restorations veneered with zirconia, ceramics, and/or composites [14]. Poly-ether-ether-ketone (PEEK) has been utilized in medicine as a metal-free implant material with elastic properties such as bone [19]. These polymers have strong properties, making them suitable for use in engineering, medicine, and dentistry. They are also safe and biocompatible for such applications [20]. Biomedical grade PEEK and FRC materials reportedly have higher flexural strength values than the minimum ISO 10477:2020 values for dental plastic materials [14,19,21,22]. Highly durable dental PEEK materials, such as JUVORA™ Dental Disc (JUVORA LTD, Lancashire, UK), were recently developed for the digital milling of definitive restorative frameworks of fixed partial dentures (FPDs), and telescopic, secondary, attachment, and/or screw-retained dental restorations, and implant-supported supra-structures [23].
Polymeric CAD/CAM materials are a cost-effective and biocompatible alternative to weaker polymers, ceramics, and noble metals. They also offer great esthetics [19]. Data regarding these polymeric materials’ flexural behavior in response to intraoral stresses are scarce [24]. This is partly due to their relatively recent introduction to dental restoration’s digital fabrication. Therefore, the current study aimed to investigate the flexural strength and effect of thermal aging on two recently introduced commercially available high-performance polymeric CAD/CAM blanks intended for the digital milling of definitive FPDs. The null hypothesis was that there is no statistically significant difference in the effect of thermal aging on the flexural strength of PEEK and FRC blanks.

2. Materials and Methods

2.1. Study Design

A total of 20 bar-shaped specimens were prepared from two commercially available high-performance polymeric materials for CAD/CAM milled FPDs (P and F). To determine the sample size, statistical power analysis was conducted using G*Power statistical software (G*Power Ver. 3.0.10, Franz Faul, Universität Kiel, Kiel, Germany). The total sample size was set at n = 20, with 10 samples in each group. The power analysis considered a power (1-ß error probability) of 0.95, error probability (α) of 0.05, and effect size of 1.8, resulting in an actual power of 0.967. The manufacturer-provided details of the materials are listed in Table 1.
Each material group (N = 10) was subdivided into aged (aF and aP) and unaged groups (uF and uP, (n = 5)). All specimens were immersed following fabrication in distilled water for 24 h at 37 °C. Aged specimens were subjected to 10,000 cycles (5–55 °C) in distilled water in a thermocycling machine with a dwell time of 5 s. A mini-flexural test was performed and the mean flexural strength values (Fs) were statistically analyzed.

2.2. Specimen Preparation

Bar-shaped specimens (2 × 2 × 12 mm) were prepared [25,26,27] from PEEK (P) and FRC (F) discs using a super-thin 0.23 mm core-thick diamond Lapidary saw blade (Jingling, China) in a precision low-speed saw cutting machine (TechCut 4™ precision low-speed saw, Allied, Cerritos, CA, USA) under continuous water cooling. Each specimen was finished and polished using wet 600, 800, 1000, and 1200 grit silicon carbide papers (3M ™ Wetordry™ Sandpaper, St. Paul, MN, USA). The size of the final specimens was verified with a digital caliper (vernier caliper 200 mm/8 in, Hi-Wendy, New Taipei, Taiwan). Every specimen was visually inspected for signs of fractures, voids, or cracks. Any flawed specimens were discarded.

2.3. Thermal Cycling

Two material groups, aF and aP, were thermally aged with 10,000 cycles of 5–55 °C water baths and 5 s dwell times (Thermocycler THE 1100/1200, SD Mechatronik, Feldkirchen-Westernham, Germany). The machine’s cycle was 40 s and water tanks were refilled daily to compensate for evaporation.

2.4. Mini-Flexural Test (MFT)

The Instron universal testing machine (5940 Series UTS (1 kN load cell), Instron, Norwood, MA, USA) was used to conduct a 3-point bending test on all specimens with a 0.5 mm/min crosshead speed. To determine the flexural strength in mega Pascals (MPa), the equation below was utilized:
Fs = 3fl/2wh2
where f is the maximum applied load, in Newtons, l is the span distance between the supports (10 mm), w is the width of the specimen (2 mm), and h is the height of the specimen (2 mm). All specimens were loaded until complete deformation. The setting of the specimens in the Instron machine is shown in Figure 1.

2.5. Statical Analysis

The statistical analysis of the results was performed using SPSS statistical software (IBM SPSS Statistics, Version 28, IBM Corporation, Armonk, New York, NY, USA). We calculated the descriptive statistics for flexural strength and analyzed their means. The Shapiro–Wilk normality test was conducted, and a paired t-test was used to compare the aged specimens’ flexural strength to an unaged copy of the same material. An independent sample t-test was used to compare the flexural strength between the two materials. The general linear model (GLM) repeated measure mixed-design analysis of variance (ANOVA) analyzed the effect of time and materials on Fs. All statistical tests used a 5-percent significance level (p = 0.05).

3. Results

The mean flexural strength values in MPa for the tested material specimens are detailed in Table 2.
GLM repeated measure mixed-design ANOVA tests of within-subjects effects showed that time was a main effect and the interactions between the time and materials were statistically significant (p = 0.01 and 0.03, respectively). Tests of between-subjects effects showed that the type of material as a main effect was statistically significant (p < 0.001). The significant change in mean Fs due to aging is demonstrated in Figure 2.
The Shapiro–Wilk test showed that all variables have not deviated from normality. Therefore, parametric tests were applied. Paired samples t-test showed a statistically significantly lower mean Fs in aF than uF (p = 0.03). Mean Fs were not significantly different in aP than uP (p = 0.53). The independent sample t-test for comparing Fs between the two materials showed a significantly higher mean Fs for both aF and uF groups than the aP and uP groups (p < 0.001). The detailed comparative analysis is shown in Table 3.

4. Discussion

CAD/CAM technology creates dental prostheses such as inlays, crowns, and dentures. It is also used for fixed-implant-supported and maxillofacial prostheses. The current study aimed to investigate the flexural strength and effect of thermal aging on two commercially available high-performance polymers intended for the CAD/CAM milling of frameworks for definitive FPDs. Both materials were indicated for CAD/CAM milling of durable biocompatible and metal-free FPDs, telescopic restorations, and RPD frameworks. The two PEEK and FRC polymer blanks tested in the study were relatively new; therefore, manufacturers provided the most data available on the mechanical properties. The null hypothesis was that there is no statistically significant difference in the effect of thermal aging on the flexural strength of PEEK and FRC blanks. The hypothesis was rejected as a significant difference in Fs was detected when the type of material was analyzed as a main effect (p < 0.001).
When selecting restorative materials, it is crucial to consider their physical properties to ensure high quality. Specifically, biocompatible materials with strong compressive, flexural, and tensile strength are important for withstanding the occlusal forces of posterior teeth [28]. Biocompatible high-performance polymers are advantageous in the prosthetic replacement of dental hard tissues due to their high strength and biomimetic properties [29]. The current study compared two materials that were designed and advertised to possess high biocompatibility and physical characteristics. The material group (F) was made from a techno-polymer composite that includes thermosetting resin and fiberglass reinforcement in multiple directions (Trilor, Bioloren S.r.l, Saronno, VA, Italy) [30]. Its reliable production ensures good bonding between fibers and resin matrix, resulting in strong stress resistance. This makes it a durable option for various applications [30,31]. However, the (P) material group was made from a thermoplastic poly-ether-ether-ketone (PEEK) polymer with up to 10% titanium oxide (JUVORA PEEK, Juvora LTD, Lancashire, UK) [32,33].
In the current study, F (uF 1014.01 MPa, and aF 949.25 MPa) had significantly higher flexural strengths than P (uP 341.40 MPa, and aP 334.27 MPa) before and after thermal aging. Compositional variation in polymeric CAD/CAM materials was found in the literature to affect the amount of water absorbed into its matrix and eventually affected its strength [34]. The two materials’ different matrices, filler types, arrangement, and/or amount could account for the difference in flexural strength and response to thermal aging between them [29]. Adding fiber reinforcement to composite resins and PEEK polymers improved their flexural strength in previous studies [9,14,19,20,35], which supports the result of the current study. The Trilor FRC (F) has a much higher elastic modulus (according to the manufacturer; 26 GPa) than Juvora PEEK (P) (4 GPa), which is similar to the elastic modulus of enamel (40–80 GPa), dentine (15 GPa), and cortical bone (20–25 GPa) [30,36,37]. This suggests that the F material may be more suitable than P for the definitive restoration of teeth and implants. Both investigated materials are strong (flexural strengths of 540 and 170 MPa, respectively, according to manufacturers), repairable, and lightweight, weighing up to five times less than zirconia [30,32]. To properly mill a full anatomic contour single-tooth restoration from F or P materials, it is necessary to follow the manufacturer’s guidelines, which include a minimum occlusal reduction of 1.5 mm, a thickness of at least 1 mm in the axial walls, and an axial taper ranging from 4 to 12 degrees [30,33]. There are differences between the requirements for finish lines and substructure thickness for the two materials, F and P. For F, a chamfer finish line of at least 0.8 mm and a substructure axial thickness of 0.5 mm (or 0.3 mm) is needed for esthetic materials such as resin composite, lithium silicate ceramics, and zirconia. Meanwhile, P requires a thicker accentuated chamfer finish line of 1 mm and a minimum substructure axial thickness of 0.7 mm when using polymeric and resin composite esthetic materials [30,33]. In the current study, it was observed that F had a higher flexural strength compared to P. This means that F requires less material thickness when veneered than P. Furthermore, F has the ability to have a thinner finish line, as per the manufacturer’s recommendations, which is indicative of its higher strength compared to P.
Polymer-based materials for dental restorations are required to have a minimum Fs of 80 MPa [38]. Both tested materials tested higher flexural strengths than the minimum. The Fs value of the P material was comparable to a previous study [19] but was higher than that supplied by the manufacturer. In the current study, the maximum load used to calculate Fs for P material was registered after complete deformation, which could have resulted in higher Fs values. The Fs values of the F material in the current study were almost double what was provided by the manufacturer. This could be explained by FRCs’ unique anisotropic mechanical properties, which differ according to the applied load direction [29]. In two studies, applying a load perpendicular to fiber direction resulted in a 2.5 times increase in Fs compared to the parallel direction [39,40]. The load in the current study was applied perpendicularly, which could account for the higher Fs value. A mini-flexural test specimen dimensions could have increased the Fs values in the current study, as suggested by Calheiros et al. [41]. The manufacturer of P tested the material’s flexural strength according to ISO 2079 testing specifications for denture base materials [42], with a different specimen size than that for the mini-flexural test. Comparing the direct value of our study to previous ones in the literature may be complicated. Nevertheless, we can compare the general trend of the tested materials’ resulting Fs to those in previous literature.
According to this study, the average flexural strength of the uF composite material was significantly greater than that of uP plastic material (p < 0.001). The fiber-reinforced composite showed a recorded flexural strength of (1014.01 ± 107.39 MPa), which is very similar to the flexural strength of Yttrium-stabilized zirconia polycrystals ceramics (YSZPCs) that maintain tetragonal phase crystals that were tested in a previous study by Al-Aali et al. (1036.3 ± 229.6, and 1171.3 ± 266 MPa) [43]. The tested FRC material for the CAD/CAM fabrication of dental restorations shows promising clinical performance, making it comparable to zirconia. The study revealed that, as PEEK and FRC aged, their flexural strength decreased. Previous studies detected a decline in the mechanical properties of Zirconia ceramics and composite blocks for CAD/CAM, which supports this observation [43,44]. This study indicated that in comparison to FRC and YSZPC in Al-Aali et al.’s research, PEEK material (with a flexural strength of 341.40 ± 31.81 MPa) exhibited a significantly lower strength [43]. According to a study by Lucsanszky et al., the composite CAD/CAM blocks had weaker flexural strengths compared to the ceramics, specifically lithium disilicate [44]. In a previous study conducted by Vichi et al., the flexural strengths of leucite-reinforced glass ceramic, lithium aluminosilicate, and lithium silicate zirconia ranged between 120 and 170 MPa [45]. According to a study by Vichi et al., the CAD/CAM lithium disilicates that require firing after milling had a comparable flexural strength of approximately 350 MPa [45], which is comparable to the flexural strength of PEEK in the current study. PEEK can be viewed as a feasible option for creating individual restorations without the need for thermal treatment.
In the current study, P materials were further bent until partial thickness fracture occurred, displaying higher deformation, which agrees with the fractographic analysis of a previous study by AlGhazzawi et al. wherein fractures were instigated by a dimple caused by a micro void coalescence that propagated until an eventual brittle crack occurred [46]. This feature was noted by Babaier et al. where all PEEK materials bent without fracture regardless of the aging protocol [29]. Fractured F specimens in the current study had exposed glass fibers without complete thickness fracturing. Peterson et al. demonstrated a similar fracture pattern in FRCs due to their lateral crack deflection and unique energy adsorption mechanism [9].
Previous studies indicated that storage conditions could significantly affect the flexural strength values of polymeric materials even within 24 h of storage [14,29,41]. This is a clinically relevant concern as these materials would be intraorally subjected to hydrolytic challenges [47]. Water absorption weakens the bond between filler and matrix, causing expansion and instability of milled restoration intraorally [14,41]. The current study showed a significant reduction in the flexural strength of FRC due to thermal aging in distilled water (p = 0.03). In contrast, the PEEK material was not significantly affected by the same aging protocol (p = 0.53). This agrees with a recent study by Babaier et al., where the flexural strength of a similar CAD/CAM FRC material (TRINIA, Bicon Europe, Ltd., Limerick, Ireland) was adversely affected by 7-day storage in water at 37 °C, and PEEK material demonstrated flexural strength stability when subjected to the same conditions [29]. Additionally, Wendler et al. demonstrated that accelerated thermal aging had a similar negative effect on other CAD/CAM resin materials [48]. This phenomenon may be caused by polymer network breakdown in water, leading to polymer chain separation and unreacted monomer release [41]. Thermal variation during aging may affect polymeric chains and trap radicals [49]. However, these findings disagree with an earlier study, where thermal aging did not significantly affect an experimental fiber-reinforced composite [50]. This disagreement could be due to compositional (PMMA vs. epoxy) and/or fiber direction differences in the tested materials between the two studies. Further research into combining the positive attributes of both materials into one biocompatible high-performance polymer for CAD/CAM milling of dental restorations and investigating the effect of other intraoral influences would be advised.
In this study, the mini-flexural test (MFT) bar-shaped material samples were analyzed instead of utilizing ISO 20795, ISO 4049, ISO 10477-sized samples [22,38,42]. According to Yap et al., MFT was found to be a suitable way to predict the mechanical performance of dental composites under realistic clinical conditions than the ISO standard flexural test. MFT was also more efficient and showed to be a good replacement for ISO 4049 in both dynamic and static flexural testing [25,51]. It was found in a previous study that the durability of indirect restorations was affected by the bonding technique and surface treatment used [52]. Thus, to prevent any potential influence from bonding agents, techniques, or surface treatments related to their type and thickness, the material samples were not milled into anatomically contoured restorations. This study provided valuable insights into the durability of metal-free, biocompatible materials that can be used for creating dental restorations with either full anatomic contour or as a substructure for veneering. This study also examined how these materials responded to simulated aging. This information can assist restorative dentists in making informed material choices for different clinical scenarios.
However, it is important to note that the study has limitations. For instance, the study was conducted in vitro, so it could not account for the influence of various factors found in the oral cavity, including parafunctional habits, dynamic occlusal load, neuromuscular forces, tooth brushing, thermocycling, and food with varying degrees of abrasivity, stainability, an acidity. When used in clinical settings, materials can undergo chemical changes, mechanical changes, and aging. It is recommended for further studies in the future to consider the effect and interaction of other factors, such as cyclic loading. Although a standard protocol was followed for preparing and finishing test specimens, it is impossible to control the presence of internal porosity due to possible material blocks manufacturing, production errors, and the release of stresses during finishing and polishing procedures. During intraoral function, CAD/CAM milled dental restorations are subject to varying multidirectional forces. Further studies on the effects of such forces on strength and surface properties could prove beneficial.

5. Conclusions

The null hypothesis that there was no statistically significant difference in the effect of thermal aging on the flexural strength of PEEK and FRC CAD/CAM blanks was rejected. Within the study’s limitations, CAD/CAM composites and PEEK polymers exceeded ISO flexural strength recommendations for dental resins. FRC and PEEK are indicated for dental restoration, especially for long-span dentures and implant-supported frameworks, thanks to their high flexural strength.

Author Contributions

Conceptualization, H.E.Y.; methodology, H.E.Y.; formal analysis, H.E.Y.; investigation, H.E.Y.; resources, H.E.Y.; data curation, H.E.Y.; writing—review and editing, H.E.Y.; visualization, H.E.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are available upon request.

Conflicts of Interest

The authors declare no conflict of interest.

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Jcs 07 00270 g001 550
Figure 1. FRC specimen undergoing 3-point bending test. Key: f = maximum applied load, in Newtons; l = the span distance between the supports (10 mm); w = the width of the specimen (2 mm); h = the height of the specimen (2 mm).
Figure 1. FRC specimen undergoing 3-point bending test. Key: f = maximum applied load, in Newtons; l = the span distance between the supports (10 mm); w = the width of the specimen (2 mm); h = the height of the specimen (2 mm).
Jcs 07 00270 g001
Jcs 07 00270 g002 550
Figure 2. The significant effect of time and type of material (where F is a fiber-reinforced composite and P is poly-ether-ether-ketone) on the mean flexural strength (Fs) with aging.
Figure 2. The significant effect of time and type of material (where F is a fiber-reinforced composite and P is poly-ether-ether-ketone) on the mean flexural strength (Fs) with aging.
Jcs 07 00270 g002
Table
Table 1. Materials used in this study.
Table 1. Materials used in this study.
BrandAbbreviationsTypeManufacturerFlexural Strength (MPA ***)
JUVORA™ Dental discPEEK * (P)Unfilled, poly-ether-ether ketoneJUVORA Ltd., Global Technology Centre,
Lancashire, UK
(Lot J000077)		170
TRILOR® discFRC ** (F)Techno-polymer, fiber-reinforced compositeBioloren® S.r.l Metal free dental solutions, Saronno, VA, Italy (Lot 2219)540
* PEEK is poly-ether-ether-ketone. ** FRC is fiber-reinforced composite. *** MPa is mega Pascal.
Table
Table 2. Descriptive statistics of flexural strength (Fs) values of the tested groups.
Table 2. Descriptive statistics of flexural strength (Fs) values of the tested groups.
Descriptive
Statistics		MaterialNMean (MPa)Standard
Deviation (MPa)		SEM
Fs before aginguF51014.01107.3948.03
uP5341.4031.8114.23
Total10677.70362.28
Fs after agingaF5949.25123.0355.02
aP5334.2711.154.99
Total10641.76334.42
Key: Fs = flexural strength; uF = unaged fiber-reinforced composite; uP = unaged poly-ether-ether-ketone; aF = aged fiber-reinforced composite; aP = aged poly-ether-ether-ketone; MPa = mega Pascal; SEM = standard error of mean.
Table
Table 3. Comparative t-tests of flexural strength (Fs) values within and between the tested materials.
Table 3. Comparative t-tests of flexural strength (Fs) values within and between the tested materials.
Paired Samples t-Test for Comparing Flexural Strength after and before Aging
Paired Differences95% Confidence Interval of the Difference
GroupMeanSDSEMLowerUppertDfp
F *uF−64.7643.6919.54−119.01−10.50−3.3140.03
aF
PuP−7.1323.0310.335.7221.47−0.6940.53
aP
Independent Sample T-Test for Comparing the Flexural Strength Between the Two Materials
95% Confidence Interval of the Difference
GroupMeanSDSEMMean DifferenceSEMLowerUppertDfp
Unaged (u) *uF1014.01107.3948.03672.6150.09557.11788.1213.438<0.001
uP341.431.8114.23
Aged (a) *aF949.25123.0355.02614.9855.24487.59742.3811.138<0.001
aP334.2711.154.99
Difference (a-u) *aF-uF−64.7643.719.54−57.6322.09−108.57−6.69−2.6180.03
aP-uP−7.1323.0310.3
* Indicates a statistically significant difference (p < 0.05). Key: Fs = flexural strength; F = fiber-reinforced composite; P = poly-ether-ether-ketone; uF = unaged fiber-reinforced composite; uP = unaged poly-ether-ether-ketone; aF = aged fiber-reinforced composite; aP = aged poly-ether-ether-ketone; MPa = mega Pascal; SEM = standard error of mean; SD = standard deviation.
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Yeslam, H.E. Flexural Behavior of Biocompatible High-Performance Polymer Composites for CAD/CAM Dentistry. J. Compos. Sci. 2023, 7, 270. https://doi.org/10.3390/jcs7070270

AMA Style

Yeslam HE. Flexural Behavior of Biocompatible High-Performance Polymer Composites for CAD/CAM Dentistry. Journal of Composites Science. 2023; 7(7):270. https://doi.org/10.3390/jcs7070270

Chicago/Turabian Style

Yeslam, Hanin E. 2023. "Flexural Behavior of Biocompatible High-Performance Polymer Composites for CAD/CAM Dentistry" Journal of Composites Science 7, no. 7: 270. https://doi.org/10.3390/jcs7070270

APA Style

Yeslam, H. E. (2023). Flexural Behavior of Biocompatible High-Performance Polymer Composites for CAD/CAM Dentistry. Journal of Composites Science, 7(7), 270. https://doi.org/10.3390/jcs7070270

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