Resin-based Materials Research Articles

Tribological Properties and Wear Mechanism of Phenolic Resin Incorporated Rare Earth Oxides

Different proportions of rare earth oxides, specifically cerium oxide and yttrium oxide, were incorporated into phenolic resin-based friction materials to mitigate the thermal degradation of resin-based friction materials. The effects of these additives on the mechanical properties and tribological performance of resin-based friction materials were thoroughly investigated, and the microstructure and phase composition were characterized via field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The addition of rare earth oxides favorably improved the density, hardness, compression strength, and shear strength of the composites, with rare earth yttrium oxide dominating the hardness of the composites and cerium oxide dominating the compression strength of the composites, but changes in the ratio of the two had a small effect on their density, shear strength, and impact strength. Among them, the highest density, hardness, compressive strength, and shear strength of the modified sample could reach 2.310 g/cm3, 118 HRL, 187.5 MPa, and 43.5 MPa, respectively, and their properties were improved by 7.7%, 14.6%, 19%, and 51%, respectively, compared with the unmodified sample Y0. The incorporation of rare earth oxides was not conducive to the improvement of the fade friction coefficient and recovery friction coefficient of the composites, but was beneficial to the stabilization of the recovery friction coefficient of the composites and the reduction in their average wear rate, with the yttrium oxide-dominated matched samples focusing on high-temperature stability, and cerium oxide-dominated matched samples focusing on the antioxidant reduction property. The homogeneous dispersion and synergistic enhancement effect of the rare earth oxides in the matrix materials enhanced the structural integrity and densification of the matrix materials and improved the interfacial strength and surface wear resistance of the composites. The worn surface of the unmodified sample Y0 was mainly abrasive and thermal fatigue wear, the worn surface of the yttrium oxide-dominated matched samples Y1 and Y2 was mainly abrasive wear, and the worn surface of the cerium oxide-dominated matched samples Y3 and Y4 was mainly adhesive and thermal fatigue wear.

Preparation of polymer hollow microsphere filled epoxy resin-based syntactic foam material and its performance analysis

To explore sound-absorbing and flame-retardant materials that meet the requirements for double-shielded and double-insulated Faraday cages, polymethyl methacrylate (PMMA) microspheres were incorporated into epoxy resin-based syntactic foam materials for testing and analysis. The addition of PMMA microspheres was found to enhance the electrical, mechanical, sound-absorbing, and flame-retardant properties of the syntactic foam, providing a potential reference for applications in high-voltage hall shielding and sound absorption. Syntactic foams with four concentrations of PMMA microspheres (0%, 0.5%, 1%, and 2%) were prepared. High-voltage breakdown testing, impedance tube testing for sound absorption coefficient, cone calorimetry for flame-retardant performance, and tensile and bending tests were conducted. Results showed that as the concentration of PMMA microspheres increased, improvements were observed in the tensile, bending, flame-retardant, and sound absorption properties of the syntactic foams, while breakdown strength decreased. These findings provide valuable insights into the application of syntactic foam materials in double-insulation, double-shielded Faraday cages.

The preparation of porous carbon from bio-based phthalonitrile resins by a non-template method: Curing, carbonization and its basic properties

Resin-based porous carbon materials are considered to be an important direction for CO2 adsorption and supercapacitors due to their controllable chemical structure, large specific surface area, and stable physicochemical properties. But at present, the main source of resin-based porous carbon materials is petroleum-based polymer materials, which is incongruous with the tenets of green chemistry. Here, a bio-based phthalonitrile precursor containing s-triazine ring structure (TDPH) was synthesized from vanillin, then a nitrogen/oxygen co-doped hierarchical porous carbon with excellent properties, was prepared using TDPH via a two-step process, with urea/zinc chloride as hardener and potassium hydroxide as activator, respectively. The carbon material prepared under optimal conditions can achieve a maximum CO2 adsorption capacity of 6.81 mmol g−1 at 273 K due to its high specific surface area (1607 m2 g−1) and high N/O content (7.06 wt%/14.74 wt%). It is worth noting that the CO2 adsorption capacity at 298 K can still reach 96.3 % of the initial adsorption after 7 cycles. In addition, the electrochemical properties of the resultant porous carbon were tested under a 1 M H2SO4 three-electrode system, and the highest specific capacitance at a current density of 0.1 A g−1 was 473 F g−1 and the specific capacitance retention can still reach 87 % after 65,000 cycles. This work broadens the source of resin-based porous carbon materials and paves a new way for the functionalization of bio-based resins.

Influence of thermal-cycling or staining medium on the surface properties and color stability of conventional, milled, and 3D-printed base materials

The study of denture base resin fabricated by digital technology with surface properties or color stability remains limited. In this study, thermal cycling and staining media (distilled water, artificial saliva, green tea, and Coca-Cola) immersion were used to simulate the intraoral environment to assess the surface properties and color stability of CAD/CAM (milled) and 3D-printed base resin materials, the conventionally polymerized base served as the control group. After thermal cycling, all groups showed increased surface roughness, contact angle (i.e. hydrophilicity) and color difference (∆E), the 3D-printed group had the most significant increase among the 3 groups (P<0.001). While there were no significant difference (or the difference is very small) between the conventional and milled groups. After 7 and 30 days of immersion in four staining media, the ∆E values remained highest in the 3D-printed group (∆E ≥ 3.34) (P<0.001), exceeding the clinically acceptable threshold (∆E = 2.7) at 30 days. Additionally, all groups showed significantly higher ∆E values after 30 days compared to 7 days (P<0.05). The 3D-printed group exhibited a rougher surface, poorer hydrophilicity, and reduced color stability compared to the conventional or milled groups, indicating that further improvements are needed before clinical application.

Fluorescence and color adjustment potentials of paste-type and flowable resin composites in cervical restorations.

Comparatively assess the fluorescence and color adjustment potentials of paste-type and flowable resin composites performed in cervical restorations. Five paste-type resin composites and 5 highly-filled flowable composites were investigated (n=5 for each). Class V cavities on 50 extracted A2 shade human central incisors were restored. Cross-polarization (CP) and fluorescence illumination (FI) images were recorded for each restoration. L*a*b* values were analyzed using the Photoshop software and color adjustment (ΔECP) and fluorescence adjustment (ΔEFI) levels were quantitatively assessed. Kruskal Wallis Test, Independent Samples t Test, One Way Anova-Welch test, and Pearson Correlation were used for the statistical analyses. The deemed significance was set at p<.050. Paste-type composites presented significantly lower ΔEFI and ΔECP values than the flowable composites (p=.006 and p<.001 respectively). ΔEFI and ΔECP values were positively correlated (r=0.584; p<.001). Paste-type Gaenial A'chord presented the lowest ΔEFI value [7.67 (5.35 - 10.99)b], while Estelite Asteria presented significantly the highest [19.94 (17.08 - 22.17)c]. Charisma Diamond One Flow presented the highest ΔECP value [3.25 (3.13 - 3.39)a] and Gaenial A'chord presented the lowest [0.79 (0.48 - 0.87)e] which was the only imperceptible score (<0.8). The only clinically acceptable color adjustment was found for Geanial Universal Injectable [1.06 (0.73 - 1.62)e] among the flowable composites. ΔEFI and b* values were positively correlated (r=0.493; p<.001). Color adjustment level and fluorescence adjustment level were considered coherent for particular composite brands. At the same time, both were better for the paste-type composites than the flowable composites on A2 base shade class V restorations. Fluorescence adjustment potential as well as the color adjustment potential varied among different composite brands regarding paste-type and flowable composites. Understanding both the color and fluorescence adjustment potentials of paste-type and flowable resin-based composite materials is clinically vital to achieve the high-end esthetics.

Remineralisation of mineral-deficient dentine induced by experimental ion-releasing materials in combination with a biomimetic dual-analogue primer

ObjectivesEvaluate the remineralisation ability of experimental resin-based materials containing Fluoride-Doped Calcium Phosphate (FDCP), applied in mineral-deficient dentine in combination with a biomimetic dual-analogue primer. MethodsArtificial dentine carious lesions were created in occlusal cavities of human molars. An experimental resin-based adhesive and flowable composite, containing FDCP (10wt% and 20wt%, respectively), were applied (±) with a biomimetic primer containing polyacrylic acid and sodium tripolyphosphate. A glass-ionomer cement and a conventional adhesive/composite were used as comparative materials. All specimens were submitted to chewing simulation in artificial saliva (AS). Subsequently, these were cut into slabs and submitted to Knoop microhardness testing and Raman spectroscopy (AS: 0, 15, 30 and 60 days). Further specimens were analysed through confocal scanning microscopy (AS: 0, 60 days). Total demineralised dentine and disc-shape materials were analysed through FTIR, SEM and EDX (Ca/P ratio) after prolonged contact in AS. Data were statistically analysed (two-way ANOVA and multiple comparison Bonferroni; α=0.05). ResultsOnly the experimental FDCP materials induced a significant increase in microhardness after storage in AS, especially in those specimens pre-treated with the biomimetic primer, except at 50 µm underneath the interface. Raman and CLSM analysis corroborated such results. The ability of the experimental FDCP resin-based materials to induce apatite-like deposition was demonstrated through SEM-EDX and FTIR. ConclusionsResin-based materials containing FDCP can mineralise the mineral-deficient dentine, especially when combined with a biomimetic dual-analogue primer. Clinical SignificanceSuch Innovative ion-releasing restorative systems applied after selective caries removal might promote remineralisation of fully and partially demineralised dentine and increase the durability of dental restorations.

Rapid formation of high-performance lunar regolith composite via combined mold pressing and thermocuring processing with low content of resin-based additives

Establishing lunar bases is pivotal for furthering lunar research and propelling deep space exploration. Lunar regolith based in-site construction is identified as the most feasible method for lunar structures. In addition, the reliance on Earth-Moon transportation, the energy required for lunar regolith manufacturing and the quality of the fabricated products are key factors in choosing a suitable forming method. This study proposes a novel way for in-site lunar regolith construction by utilizing a small amount of resin-based binding material and a combined processing method of molding and thermosetting. A specific thermosetting resin is developed to achieve fully solidification of the mixed material at lunar daytime temperatures of approximately 120 °C, addressing the high energy consumption associated with the sintering process. Mold pressing is used to provide the rapid pre-forming of mixed materials and greatly reduce the proportion of additives. The binder additions ranging from 5 wt% to 1 wt% were investigated. It was found that the formed part with a binder proportion of 2 wt% could achieve a compressive strength exceeding 26 MPa and the low thermal conductivity of about 0.371 W/(m·K). The proposed method has advantages of high in-situ utilization rate, low-energy consumption and rapid formation rate, enabling efficient forming of high performance lunar regolith structure and providing feasibility for future lunar construction projects.

Evaluation of Flexural Strength and Vickers Micro Hardness of Three Different Denture Base Resin Materials

ABSTRACT Objectives: To evaluate the Vickers hardness and flexural strength of computer-aided design/computer-aided manufacture (CAD/CAM) milled, 3D-printed, and traditional heat-polymerized denture base resins used in computer-aided design and manufacture. Materials and Methods: A total of 60 samples were fabricated from CAD/CAM milled resin (PMMA dental material-Ruthinium disc, Badia Polesine (Rovigo) Italy), CAD/CAM 3D-printed resin (NextDent Denture 3D+, Soesterberg, The Netherlands) and conventional heat-polymerized (HP) denture base resin (DBR) (Triplex hot Ivoclar-Vivadent, Liechtenstein). Based on the three different denture base resin materials (n = 10/material) (30/flexural strength and 30/microhardness), the samples were split into six groups. The 3-point bending test was used to assess flexural strength, while Vickers microhardness test was used to assess surface hardness. The acquired data was statistically assessed. Results: CAD/CAM milled resins showed appreciably greater values for both the flexural strength and surface hardness, followed by conventional HP denture base resin and CAD/CAM 3D-printed resin. Pairwise comparison for Flexural Strength and Vickers microhardness revealed significant differences between groups. Conclusion: CAD/CAM milled resins had the highest surface hardness and flexural strength compared to Conventional HP denture base resin and CAD/CAM 3D-printed resin.

Comprehensive properties analysis of epoxy composites synergistically toughened with liquid nitrile rubber and polyethersulfone

In this paper, epoxy resin (EP) composites with different phase structures were prepared by introducing hydroxyl-terminated liquid nitrile rubber (HTBN) and hydroxyl-terminated polyethersulfone (PES) individually or simultaneously into the resin matrix. The results revealed that the rational distribution of phase structure of rigid PES and flexible HTBN can effectively contributed to the enhancement in their mechanical and electrical insulation strengths. The synergistic effect of the two reinforcing fillers granted the optimized ternary composite a tougher structural network, leading to significant improvements of 73.13 % and 18.98 % in mechanical impact strength and electrical breakdown strength, respectively, compared to the pristine EP. Furthermore, compared to HTBN, PES exhibited inhibited HTBN dielectric interfacial polarization and EP molecular chain segment relaxation, resulting in decreased dielectric constant and loss in the composites. This study provide insights into the dielectric properties and design strategies for the development of resin-based dielectric materials, ensuring their broader applicability.

Does the application of polywave light-curing units influence physico-mechanical properties of resin-based materials? A meta-analysis of In vitro studies

The objective of this study was to systematically review the existing literature and to assess the effect of the use of polywave light-curing units on the properties of resin-based materials. A thorough search was conducted across five electronic databases: PubMed (MedLine), ISI Web of Science, SciELO, Scopus, and EMBASE. Inclusion criteria comprised in-vitro studies that compared the effects of polywave light-emitting diode (LED) curing units with monowave LED curing units on resin-based material properties. Two reviewers evaluated the methodological quality of the included studies, considering parameters from previous systematic reviews. Meta-analyses were conducted using Review Manager version 5.3.5 (The Cochrane Collaboration, Copenhagen, Denmark). Overall, when the TPO photoinitiator was employed, the use of a polywave light-curing unit demonstrated statistically significant higher values solely for the degree of conversion (p&lt;0.001) and hardness (p&lt;0.01). No statistically significant differences were observed between monowave and polywave light curing units in the other evaluated properties. Based on the findings of this review, the use of polywave light-curing can be useful for polymerizing materials that contain photoinitiators other than camphorquinone in their composition.

The effect of whitening toothpastes on the surface properties and color stability of different ceramic materials

ObjectivesThis study aimed to evaluate the effect of whitening toothpastes on the surface roughness and colour change of CAD-CAM materials.Materials and methodsA total of 96 samples (2 × 10 × 12 mm3) were prepared from Cerasmart (CS) and Celtra Duo blocks. Celtra Duo samples were divided into two groups. One group was fired with glaze paste (CDG) and the other was not treated (CD). All groups were then divided into 4 subgroups (n = 8). The groups were brushed with conventional (Colgate™ Max Fresh), silica (Opalescence™), charcoal (Curaprox™ Black in White) and blue covarine (Signal™ White Now) toothpastes for 30,000 brushing cycles. The initial and final surface roughness values were measured with contact profilometer and a dental spectrophotometer used for obtaining colour values. One sample from each brushed group was analyzed using a scanning electron microscope. Data was analyzed with Kruskal-Wallis and Mann-Whitney tests (p = 0.05).ResultsThe surface roughness of CS samples brushed with Opalescence™ and Curaprox™ was significantly higher than CD and CDG. Surface roughness change values of CS samples brushed with Curaprox™ were significantly higher than the CD and CDG. Curaprox™ brushed samples showed significant difference in colour change values for all materials.ConclusionsBrushing increases the surface roughness of CAD-CAM ceramic materials. The roughness of resin-based materials is higher than zirconia-reinforced lithium silicates. Silica-contained toothpastes may cause discoloration of nanoceramic and zirconia-reinforced glass ceramic restorations.Clinical relevanceIt should be clinically considered that whitening toothpastes may cause roughness in ceramic materials and change the desired color.

A comparative study of polishing systems on optical properties and surface roughness of additively manufactured and conventional resin based composites

This study aimed to compare polishing systems on color stability, surface roughness, and gloss of additively manufactured permanent and conventional resin composites. Totally 250 disc specimens (6 mm*2 mm) were prepared from resin-based materials [G-ænial Posterior (GP), Clearfil Majesty Esthetic (CME), SonicFill-2 (SF), Tescera (Tes), and Crowntec (CT)]. Following baseline color (ΔE00), gloss (GU), and surface roughness (Ra) measurements, the specimens were randomly divided into 5 groups (n = 10/group) according to polishing systems: Control (mylar strips); OneGloss; OneGloss + Platina Hi-Gloss; OptiDisc; and OptiDisc + Platina Hi-Gloss. Specimens were immersed in coffee for 144 h following polishing. ΔE00, GU, and Ra measurements were repeated. Atomic force microscopy images were taken in all groups. Spearman’s rho correlation coefficient, Robust ANOVA, and Bonferroni correction were used for statistical analysis. Significance level was taken as p < 0.050. Significant differences in ΔE00 values were found among resin-based materials, polishing systems, and their interactions (p < 0.001,p < 0.01, and p = 0.001). Regardless of polishing system, the lowest ΔE00 values were observed in CT, while lowest gloss (GU) values were found in Tes. The lowest surface roughness (Ra) values were detected at OptiDisc group (p < 0.001). A single type of polishing system may not be sufficient to achieve optimal results in resin-based materials.

Bond strength of resin-based restorative materials to fast-setting calcium silicate cement using different resin adhesive systems.

This study assessed the bond strength of resin-based restorative materials to fast-setting calcium silicate cement (Aarhus Uinversity, Denmark) when treated with each of two one-bottle universal adhesive systems. The cement surface (N=256) was treated with a self-priming adhesive and a self-etch phosphate monomer-containing adhesive with and without etching of the cement surface. Specimens then received either resin composite or compomer restorative materials (n=32). The bond strength was measured after 1 day and 1500 thermocycles (n=16). The failure type was visually inspected. The cement-adhesive-restorative material interface was visualized using scanning electron microscopy (SEM). The data were analyzed using multiple linear regression. Restorative material type, resin adhesive system, and thermocycling had a statistically significant effect on the bond strength. Compomer restorative material and self-etch universal adhesive system demonstrated statistically significantly higher bond strength values to fast-setting calcium silicate cement, predominantly exhibiting cement cohesive failure. Etching the cement surface enhanced the bond strength of the self-priming universal adhesive. Thermocycling significantly reduced the bond strength. SEM showed self-etch universal adhesive seemingly diffused over the etched cement surface compared to other groups. Self-etch phosphate monomer-containing universal adhesive and compomer resulted in the highest bond strength to fast-setting calcium silicate cement.

Beyond Traditional Fillings: Why Bulk-Fill Composites Are Changing the Game

This review examines the impact of bulk-fill composites in restorative dentistry, highlighting their advantages over traditional resin-based materials. Conventional composites often require multiple incremental placements, increasing technique sensitivity and the risk of restoration failure. Bulk-fill composites allow for placement in single layers of 4-6mm, reducing chairside time and procedural complexity. The review discusses innovations in formulation, including enhanced translucency and modifications in photoinitiators that support effective polymerization. Key properties such as microhardness, degree of conversion, depth of cure, and polymerization shrinkage are evaluated, showing that high-viscosity bulk fills can achieve hardness comparable to conventional composites. Various commercially available products are assessed for their clinical performance. The review ultimately emphasizes the growing acceptance of bulk-fill composites as reliable alternatives, advocating for continued research to enhance clinician confidence in their application and effectiveness in deep cavity restorations. Keywords: Bulk fill composites, posterior composites, incremental composite placement, tooth colored restoratives, polymerisation shrinkage, degree of conversion, depth of cure

Fatigue life prediction of CFRP flat-fold-flat adhesive joints

Taking the flat-fold-flat (FJF) adhesive joints of carbon fiber reinforced bismaleimide resin-based composite materials as the object, the regularized fatigue life model and residual stiffness model of the one-way plate and the cohesive model parameters of the adhesive layer were fitted experimentally, and based on this, the fatigue life of the adhesive joint was predicted by ABAQUS software. The results show that under specific maximum load conditions, the predicted cracking life of the adhesive layer at the end of the lap joint and the final fatigue life are not greater than the error values of the test results 3% , which has a relatively good calculation accuracy. The cracking life of the adhesive layer at the end of the lap joint is approximately equal to the final fatigue life of the adhesive joint, indicating that the cracking of the adhesive layer at the end of the lap joint accounts for the main part of the total life of the adhesive joint, and the crack propagation life of the adhesive layer can be ignored.

Effect of laser irradiation during in-office tooth bleaching on surface properties of resin-based restorative materials.

This study evaluated the changes in surface properties of three resin-based restorative materials after two laser-assisted, in-office tooth bleaching protocols using erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) or diode (980nm) lasers. A nanohybrid composite (Enamel Plus HRi), a Bis-GMA-free composite (Enamel Plus HRi Bio Function), and a resin-matrix CAD-CAM ceramic (Shofu Block HC) were tested. Forty specimens for each material were prepared and divided into four groups (n=10/group). The control specimens did not undergo any bleaching treatment, whereas group 2 received bleaching with 40% hydrogen peroxide (H2O2), while groups 3 and 4 underwent the same bleaching procedure with the use of diode (980nm) or Er,Cr:YSGG lasers, respectively. Surface microhardness and roughness measurements were conducted using a Vickers tester and an optical profilometer. Microhardness was lower in bleached specimens, with the nanohybrid composite exhibiting the largest difference from the no bleaching group. For the Bis-GMA-free composite the microhardness difference between no bleaching and laser-assisted bleaching were smaller than seen for the conventional bleaching technique. Surface roughness was higher in bleached specimens, with nanohybrid composite showing the largest differences from the control specimens. The examined laser-assisted tooth bleaching protocols were found not to impact surface microhardness and roughness of the tested resin-based specimens and they are deemed suitable for clinical use.

Research progress on blood compatibility of hemoperfusion adsorbent materials.

This comprehensive review examines the latest developments in improving the blood compatibility of hemoperfusion adsorbents. By leveraging advanced coating and modification techniques, including albumin-collodion, cellulose, hydrogel, and heparin coatings, notable enhancements in blood compatibility have been achieved across diverse adsorbent types, such as carbon-based, resin-based, and polysaccharide-based materials. Despite promising laboratory results, the intricate manufacturing processes and elevated costs present significant challenges for broad clinical application. Therefore, future endeavors should focus on cost-benefit analysis, large-scale production strategies, in-depth exploration of blood-material interactions, and innovative technologies to propel the development of safer and more effective blood purification therapies.

Evaluation of Radiopacity of Calcium Silicate-Based and Resin-Based Materials Using Direct Digital Radiography Along With an Aluminium Step Wedge.

Background Radiopacity is a critical property for root canal sealers as it allows for the assessment of the material's placement and quality within the root canal system on radiographic images. The study aimed to evaluate the radiopacity of calcium silicate-based and resin-based materials using direct digital radiography, employing an aluminium step wedge according toAmerican National Standards Institute/International Organization for Standardization (ANSI/ISO) standard protocols for testing the radiopacity of root canal sealers. This study seeks to determine the effectiveness of these materials in meeting the required standards for clinical use. Methodology The materials tested were AH Plus, Apexit Plus, Biodentine and MTA Fillapex in circular disc form and radiographed alongsidethe aluminium step wedge using direct digital radiography to determine the radiopacity using grey-pixel values. All the materials, viz., AH Plus, Apexit Plus, Biodentine and MTA Fillapex were found satisfactorily radiopaque and met the minimum radiopacity standard, that is, minimum 3mm of aluminium recommended by ANSI/American Dental Association (ADA) Specification No. 57. Results AH Plus exhibited the highest radiopacity with values of 222.54 mm Al Eq (isodensity) and 220.88 mm Al Eq (densitometric), significantly surpassing Apexit Plus, Fillapexand Biodentine (p < 0.001). Apexit Plus and Fillapex showed no significant difference between them (p = 0.238), but both were significantly higher than Biodentine (p < 0.001). Biodentine had the lowest radiopacity among all the sealers tested. Conclusion All the tested materials met the ANSI/ADA minimum radiopacity standard, demonstrating their suitability for clinical use. The materials varied in their levels of radiopacity, demonstrating that they are adequately visible on radiographic images for effective assessment in root canal treatments.

In Vitro Bond Strength of Dentin Treated with Sodium Hypochlorite: Effects of Antioxidant Solutions.

This systematic review aims to evaluate whether the application of antioxidant solutions can enhance the bond strength of resin-based materials to sodium hypochlorite (NaOCl)-treated dentin. This study follows the PICOT strategy: population (sodium hypochlorite-treated dentin), intervention (application of antioxidants), control (distilled water), outcome (bond strength), and type of studies (in vitro studies). The systematic review and meta-analysis were conducted following PRISMA guidelines. Electronic databases were searched for in vitro studies evaluating the effects of antioxidants on bond strength to sodium hypochlorite-treated dentin. Two independent reviewers screened articles, extracted data, and assessed risk of bias. Meta-analyses were performed using a random-effects model to compare standardized mean differences in bond strength between antioxidant pretreatment and control groups. Inclusion criteria consisted of in vitro studies that examined the bond strength of resin-based materials to NaOCl-treated dentin with antioxidant application, while exclusion criteria included studies with incomplete data, those not using a control group, or those that did not directly measure bond strength. From 3041 initial records, 29 studies were included in the qualitative analysis and 25 in the meta-analysis. Ascorbic acid, sodium ascorbate, grape seed extract, green tea, and rosmarinic acid significantly improved bond strength to sodium hypochlorite-treated dentin (p < 0.05). The effectiveness of grape seed extract varied with adhesive system type. Hesperidin, p-toluene sulfonic acid, and sodium thiosulfate did not significantly improve bond strength. Most studies had a high risk of bias. This suggests that the conclusions drawn from these studies should be interpreted with caution, and further research with more robust methodologies may be needed to confirm the findings. In conclusion, this systematic review implies that certain antioxidants can improve bond strength to sodium hypochlorite-treated dentin, with efficacy depending on the specific agent and adhesive system used. Further standardized studies are needed to optimize protocols and confirm these findings.

Effect of Treated Fiber Reinforcement on the Flexural Strength of Heat-Cured Denture Base Resin Materials

Effect of Treated Fiber Reinforcement on the Flexural Strength of Heat-Cured Denture Base Resin Materials