Search Results (357)

Evaluating the shear bond strength (SBS) of contemporary universal adhesive systems on different substrates is critical for understanding their clinical applicability. In this study, the SBS of universal adhesives was assessed on 144 human and bovine tooth specimens, comparing enamel and dentin across etch-and-rinse and self-etch protocols. Following single-step or two-step adhesive application and resin cementation, the specimens were subjected to 5000 thermocycles before being evaluated with a universal testing machine. Failure modes and surface morphology were additionally characterized using stereomicroscopy and scanning electron microscopy (SEM). Statistical analyses revealed that both tissue type (p = 0.043) and tooth type (p < 0.001) significantly influenced SBS, while the main effect of the adhesive protocol was not significant (p = 0.485). A significant interaction occurred between tissue type and adhesive protocol (p = 0.013); Post hoc analyses revealed that Group A enamel had significantly higher bond strength than both Group D enamel (p = 0.026) and Group A dentin (p = 0.001). Observed failures were predominantly adhesive or mixed, and SEM confirmed expected acid-induced surface roughness. Human teeth yielded higher bond strengths than bovine teeth, meaning absolute SBS values from bovine lab studies should be used with caution. Full article

Chlorhexidine (CHX) has been widely reported as an inhibitor of matrix metalloproteinases (MMPs), contributing to the preservation of dentin bond integrity, while chitosan (CS) has been proposed as a natural biomodifier with potential collagen-stabilizing and cross-linking effects on the dentin matrix. These properties make both agents relevant candidates for improving the durability of adhesive interfaces. This in vitro study evaluated the effect of CS- and CHX-containing cavity disinfectants on the microtensile bond strength (µTBS) of a two-step self-etch adhesive applied to superficial and deep dentin. Forty-eight sound human molars were randomly assigned to superficial and deep dentin groups, which were further subdivided according to surface treatment: control (no treatment), 2% CHX, and 2.5% CS. A two-step self-etch adhesive system (Clearfil SE Bond) and resin composite were applied according to the manufacturers’ instructions. After storage and thermocycling, beam-shaped specimens were prepared and subjected to µTBS testing. Data were analyzed using appropriate statistical methods, and significance was set at p < 0.05. CS pretreatment resulted in higher µTBS values compared with the control group in both superficial and deep dentin, with statistically significant differences observed (p < 0.05), while CHX-treated groups showed intermediate values, with no consistent statistically significant difference compared with CS. In general, superficial dentin exhibited higher bond strength values than deep dentin (p < 0.05). Within the limitations of this in vitro study, chitosan-containing cavity disinfectant was associated with significantly higher µTBS values compared with the untreated control in both superficial and deep dentin when used with a two-step self-etch adhesive. However, these findings should be interpreted with caution and should not be generalized beyond the specific materials and experimental conditions evaluated. Full article

Background: In the field of minimally invasive restorative dentistry, ultrathin (<0.5 mm thickness) ceramic occlusal veneers are increasing being used as alternatives to full-coverage crowns, particularly for mild occlusal wear and not deep caries. However, only limited research attention has been given to how marked reduction in the thickness of a veneer restoration affects its mechanical performance. The purpose of the present in vitro study was to compare the performance of restorations that comprised a 0.3 mm thick zirconia veneer to the case when a lithium disilicate veneer was used, under quasi-static compressive loading. Methods: Forty extracted human molars, without caries, cracks or fractures and with intact coronal structure, were randomly assigned to two groups: lithium disilicate occlusal veneers (n = 20) and zirconia occlusal veneers (n = 20). The teeth were embedded in acrylic resin up to the cementoenamel junction. Digital scans were used to record the original anatomy and guide restoration design. Standardized occlusal preparations were performed using a 0.3 mm reduction protocol and verified with silicone guides to support a biomimetic, tooth-preserving approach. After preparation, the teeth were rescanned, and restorations were designed and fabricated using CAD/CAM technology. Lithium disilicate restorations were milled from Ivoclar Porcelain System [IPS], esthetic maximized [e.max] computer-aided design [CAD] blocks, whereas zirconia restorations were milled from Prettau 3 zirconia discs. Restorations were adhesively cemented with dual-cure resin cement following material-specific surface treatment protocols. Fracture resistance was tested using a universal testing machine under compressive loading until failure. Results: The fracture loads with lithium disilicate and zirconia occlusal veneers were 481.45 ± 68.23 N and 720.93 ± 95.44 N, respectively. Fracture was catastrophic in lithium disilicate occlusal veneers whereas it was not so when zirconia veneer was used. Conclusion: Quasi-static compressive fracture load when a lithium disilicate veneer was used was significantly lower than when a zirconia veneer was used. Full article

The objective of this study was to evaluate the antioxidant and antibacterial profiles of Picea orientalis (Oriental spruce) resin extracts collected from three distinct geographical sites (Artvin, Borçka, and Çaykara) within the Eastern Black Sea region of Türkiye. Additionally, it aimed to assess the viability of these extracts as natural antibacterial agents against cariogenic pathogens and to determine their subsequent effect on dental bond strength performance. Quantitative phytochemical analysis of the ethanolic extracts included the determination of total phenolic content, coupled with individual phenolic profiling by HPLC-PDA. The antioxidant potential was assessed through DPPH and FRAP assays. Additionally, the antibacterial activity against a panel of oral and systemic pathogens was evaluated using agar well diffusion. Furthermore, to evaluate mechanical performance, composite bond strengths were tested on 180 dentin specimens using both self-etch and etch-and-rinse adhesive strategies, following cavity pre-treatment with a control, chlorhexidine, or the resin extracts. The results revealed that the resin from the Artvin region exhibited the highest phenolic content, characterized by an abundance of trans-cinnamic, caffeic, and ferulic acids, which correlated with their superior antioxidant capacity. Furthermore, while the extracts demonstrated potent inhibitory effects against Staphylococcus aureus, their antibacterial activity against Streptococcus mutans was found to be comparatively moderate. In bond strength evaluations, the non-aged control group exhibited the highest values (p = 0.000); however, no statistically significant difference was observed between the chlorhexidine and resin extract groups (p > 0.05). Consequently, the phenolic-rich P. orientalis resin represents a promising natural antibacterial alternative for dental applications. Full article

The aim of this in vitro study was to evaluate the internal adaptation and adhesion performance of a novel 3D-printed custom post system compared with three commercially available intra-canal post systems with different physical and surface characteristics. Twenty extracted human mandibular premolars were endodontically treated and divided into four groups according to the post system used: RelyX Fiber Post (3M ESPE), Splendor SAP Post (Angelus), everStick Post (GC), and custom 3D-printed posts fabricated from a permanent restoration resin. Following cementation with a self-adhesive resin cement, micro-computed tomography was used to assess cement thickness and gap formation in the apical, middle, and coronal regions, while push-out bond strength was evaluated using a universal testing machine. The 3D-printed custom posts exhibited the lowest mean cement thickness (39.27 ± 14.47 µm in the apical and 66.25 ± 47.98 µm in the coronal region), whereas the Splendor SAP group showed the highest values (reaching up to 219.76 ± 74.64 µm in the coronal region). In contrast, the highest push-out bond strength was observed in the RelyX Fiber Post (46.52 ± 26.00 MPa) and GC everStick (48.17 ± 4.64 MPa) groups in the coronal region, while the 3D-printed custom posts demonstrated the lowest overall bond strength values, dropping to 8.53 ± 3.56 MPa in the apical region. In all groups, bond strength significantly decreased from the coronal to the apical region. Within the limitations of this study, 3D-printed custom posts provided superior intra-canal adaptation but inferior adhesion performance compared with conventional post systems. Full article

Because superficial and deep dentin differ in their structural characteristics and bonding behavior, optimizing adhesive strategies for both substrates is clinically important. The aim of this in vitro study was to evaluate the effects of different application strategies of a universal adhesive system and single-shade resin composites on the micro-shear bond strength (μSBS) to superficial and deep dentin. A total of 240 extracted human third molars were prepared to obtain superficial or deep dentin specimens. A universal adhesive system (Gluma Bond Universal) was applied using etch-and-rinse (E&R), self-etch (SE), and selective dentin etch (SDE) strategies. Four commercially available single-shade resin composites (Omnichroma, Zenchroma, Charisma Diamond One, and Vittra APS Unique) were evaluated. After 24 h of water storage, μSBS was evaluated and failure modes were analyzed. Dentin depth, adhesive strategy, and composite type significantly affected μSBS values (p < 0.05). Superficial dentin exhibited significantly higher bond strength than deep dentin (p < 0.001). The effect of adhesive strategy depended on dentin depth; in deep dentin, SDE provided significantly higher bond strength than both E&R and SE applications (p < 0.001). Significant interactions were observed among dentin depth, adhesive strategy, and composite type (p < 0.05). The predominant mode of failure across most experimental groups was adhesive failure. Within the limitations of this in vitro study, dentin depth, adhesive strategy, and single-shade composite type significantly influenced dentin bond strength. Selective dentin etching was associated with increased bond strength in deep dentin under the experimental conditions of this study. Full article

Bioceramic sealers have gained widespread acceptance in contemporary endodontics due to their favorable biological properties, dimensional stability, and bioactivity. However, their strong adhesion to dentinal walls and penetration into dentinal tubules may complicate removal during endodontic retreatment procedures. Additionally, the obturation technique may influence both the retreatability of root canal filling materials and the bond strength of sealers and resins to radicular dentin. Methods: One hundred extracted human single-rooted teeth were instrumented using the WaveOne Gold system and obturated with a bioceramic sealer using two techniques: single-cone (Group A, n = 50) and warm vertical compaction (Group B, n = 50). After sealer setting, retreatment procedures were performed using ProTaper Universal Retreatment files combined with passive ultrasonic irrigation. Scanning electron microscopy was used to evaluate smear layer removal and dentinal tubule obstruction. Eighty specimens were subsequently re-obturated with a bioceramic sealer and divided into four subgroups according to the obturation technique used before and after retreatment. A push-out bond strength test was performed on coronal, middle, and apical root sections. Statistical analysis was conducted using SPSS software with a significance level set at p ≤ 0.05. Results: No statistically significant differences were observed between the groups regarding the working time required for root filling removal (p > 0.05). However, significant differences were found in push-out bond strength values among the experimental groups (p < 0.05). Specimens obturated using warm vertical compaction showed significantly higher bond strength compared with the single-cone technique. Scanning electron microscopy observations revealed less residual bioceramic sealer on dentinal walls in the warm vertical compaction group. Conclusions: Within the limitations of this in vitro study, the warm vertical compaction technique demonstrated superior bonding performance and resulted in less residual bioceramic sealer after retreatment compared with the single-cone technique. Full article

In recent years, hybrid materials have been widely applied in the cultural heritage conservation field, especially to preserve color pigments. Among these, one of the most problematic (in terms of conservation science) is the red pigment cinnabar/vermilion. The challenge of this work was to prepare a hybrid coating consisting of a fluorinated polymer (known to protect cinnabar/vermilion), further modified with an inorganic filler based on anatase TiO₂. The latter is suitable because it is functionalized with quenchers, the particles are well above the nanoscale (≥200 nm in diameter), and it was added to the polymer matrix in small quantities. These characteristics made it suitable as a hybrid coating for protecting natural cinnabar, as demonstrated by the results obtained through a multi-analytical approach, based on multispectral imaging, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), contact angle, spectrophotometry and mechanical tests, which were applied to evaluate the performances of the hybrid coating on laboratory specimens (after aging) and original samples. The experimental results provide insight into both the physicochemical decomposition mechanism of natural cinnabar under laboratory-simulated aging conditions and the benefits of the coating. In particular, the treatment did not induce electrochemical changes in the mercury, which remained in its oxidized state (+2) rather than being further reduced to elemental mercury (Hg⁰), the species responsible for the blackening of cinnabar/vermilion (also combined with meta-cinnabar). In the oxidized form (Hg²⁺), the protein binder was altered, yet the application of the hybrid coating did not cause further physicochemical changes (i.e., red shift) to the Hg²⁺/egg-based binder system. This was also reflected in the color properties, which underwent no significant alteration. Finally, the mechanical tests yielded satisfactory results, particularly regarding water vapor permeability and treatment efficiency (even eight months after the initial application, although studies on the same samples are still ongoing). The hybrid coating was ultimately applied to original samples collected at Poggio Spaccasasso (Tuscany, Italy), which could be representative of prehistoric artworks based on natural cinnabar and traces of prehistoric adhesives made from beeswax, natural oils, and plant resins. Full article

The long-term success of zirconia restorations depends on the durability of the resin–zirconia bond. This study evaluated the microshear bond strength (μSBS) of an MDP-containing universal adhesive, Scotchbond Universal Plus Adhesive, compared with its predecessor, Scotchbond Universal Adhesive, when bonded to three generations of CAD/CAM-fabricated zirconia ceramics. Sixty zirconia specimens were fabricated from 3Y-TZP (IPS e.max ZirCAD), 4Y-PSZ (IPS e.max ZirCAD MT), and gradient zirconia (IPS e.max ZirCAD Prime; 3Y-TZP/5Y-PSZ). Following polishing, sintering, and airborne-particle abrasion with 50 μm Al₂O₃ particles, specimens received either Scotchbond Universal Plus Adhesive or Scotchbond Universal Adhesive. Resin cement cylinders were bonded with a dual-cure resin cement and subjected to thermal cycling (20,000 cycles; 5–55 °C) prior to μSBS testing. Data were analyzed using one-way ANOVA, independent-samples t-tests, and Fisher’s exact test (α = 0.05). Significant differences in μSBS were observed among zirconia generations for both adhesive systems (p < 0.05). The highest bond strengths were recorded for 4Y-PSZ bonded with Scotchbond Universal Adhesive (15.36 ± 3.00 MPa) and Scotchbond Universal Plus Adhesive (14.67 ± 4.52 MPa), whereas the lowest values were obtained for 3Y-TZP (8.91 ± 3.53 MPa and 9.20 ± 3.52 MPa, respectively). No significant differences were detected between the two adhesive systems within any zirconia generation (p > 0.05). Failure mode analysis revealed predominantly adhesive and mixed failures, with no significant differences in the distribution of failure modes among groups (p > 0.05). In conclusion, zirconia generation significantly influenced bond strength, whereas Scotchbond Universal Plus Adhesive demonstrated bonding performance comparable to that of Scotchbond Universal Adhesive after thermocycling. Among the tested substrates, 4Y-PSZ exhibited the most favorable bonding performance. Full article

The development of bio-based adhesives has emerged as a viable strategy to reduce fossil-derived resin consumption in wood and wood-based panel applications. This review provides a polymer-focused assessment of adhesive systems derived from proteins, carbohydrates, lignin, and tannins, emphasizing molecular architecture, crosslinking chemistry, interfacial interactions, and structure–property relationships. Adhesive performance is primarily dictated by functional group density, crosslinking efficiency, and network topology. Protein-based adhesives rely on hydrogen bonding and covalent crosslinking with lignocellulosic substrates but require structural modification to improve hydrothermal stability. Carbohydrate-based systems, including starch and cellulose derivatives, offer reactive hydroxyl functionalities that enable oxidation, esterification, and etherification pathways for enhanced network formation. Lignin and tannins, characterized by phenolic and aromatic structures, facilitate condensation reactions and enable partial substitution of phenol in thermosetting resins, supporting low-formaldehyde or formaldehyde-free formulations. Hybrid polymer networks, particularly protein–carbohydrate and lignin-modified systems, demonstrate improved crosslink density, reduced hydrophilicity, and enhanced mechanical performance. Life cycle analyses indicate that increasing biogenic carbon content and minimizing fossil-based cross-linkers can lower global warming potential (GWP) and volatile organic compound (VOC) emissions. Overall, a structure–property–sustainability framework is proposed to guide molecular design and performance optimization of next-generation bio-based wood adhesives. Full article

Background/Objectives: High-viscosity glass hybrid restorative systems (GHRS) were developed to improve the mechanical limitations of conventional glass ionomer cements while preserving their bioactive properties. This scoping review aimed to map and synthesize the currently available evidence regarding the clinical performance of high-viscosity glass hybrid restorative systems in posterior teeth. Methods: A literature search was conducted in PubMed/MEDLINE, Web of Science and Google Scholar using MeSH terms and free-text keywords related to glass hybrid restorative systems and posterior restorations. After screening and eligibility assessment, 39 studies were included in the review. Results: The reviewed studies indicated that GHRS exhibited better wear resistance, higher fracture resistance, improved surface durability, and superior marginal integrity compared with conventional high-viscosity glass ionomer cements. Equia Forte HT (GC Corporation, Tokyo, Japan), combined with nano-filled resin coatings, was the most frequently investigated system and showed favorable short- and medium-term clinical performance in small-to-moderate posterior restorations. Discussion: Glass-hybrid restorative systems have demonstrated considerable potential in minimally invasive dentistry, atraumatic restorative treatment, and pediatric restorative applications, particularly in patients with increased caries susceptibility. Their sustained fluoride release, chemical adhesion to dental tissues, and improved moisture tolerance may contribute to favorable clinical outcomes in challenging operative conditions. Conclusions: Within the limitations of the available evidence, high-viscosity glass-hybrid restorative systems may represent a promising restorative option for selected posterior restorations. Nevertheless, the available evidence remains heterogeneous, and further high-quality long-term randomized controlled trials are required to confirm their clinical performance and indications. Full article

Biobased wood adhesives are essential to reducing the dependence of wood-based panels on petrochemical and formaldehyde-emitting resins. This review critically synthesizes recent progress in lignin-, tannin-, starch-, furan/HMF-, organic acid-, and soy protein-based adhesive systems, with emphasis on chemical reactivity, curing mechanisms, water resistance, processability, and industrial relevance. The discussion distinguishes laboratory performance from industrial feasibility by considering specific press time, solids content, viscosity, raw material variability, emissions, cost, life-cycle performance, and compatibility with particleboard, medium-density fibreboard, plywood, and related engineered wood products. Lignin and tannins are highlighted as the most chemically compatible phenolic platforms, starch and soy systems as abundant but moisture-sensitive binders requiring targeted crosslinking, HMF and furan derivatives as promising aldehyde-type formaldehyde-free crosslinkers, and citric acid systems as attractive polyester-forming binders with pressing-temperature limitations. The review concludes that near-term adoption will most likely proceed through hybrid and partially biobased systems, whereas fully biobased adhesives require faster curing, standardized feedstocks, pilot-scale validation, and transparent techno-economic and life-cycle assessment. Full article

Epoxy resins are widely used in advanced engineering applications, including coatings, adhesives, and electronics. Therefore, improving their flame resistance is important for enhancing fire safety and extending their range of applications. A series of flame retardants based on melamine phosphate derivatives, such as melamine phosphate (MP), melamine dibutyl phosphate, and melamine bis(2-ethylhexyl) phosphate, as well as a zinc borate-modified system (ZnB-MP) has been incorporated into commercially available epoxy resin (Epidian® 601). The blends were characterized using Fourier transform infrared spectroscopy (FTIR) to confirm their chemical structure. Thermal behaviour was investigated using differential scanning calorimetry and thermogravimetry coupled with FTIR gas analysis (TG-FTIR). The flammability performance of the epoxy blends was evaluated using pyrolysis combustion flow calorimetry, which allowed parameters such as heat release rate, total heat release, and heat release capacity to be determined. The incorporation of melamine phosphate-based flame retardants was found to significantly reduce the flammability of epoxy blends, leading to substantial decreases in heat release rate, total heat release, and heat release capacity. The most pronounced effect was observed in systems containing higher concentrations of MP and in cooperative ZnB-MP formulations. Full article

Self-adhering flowable composites (SAFCs) were developed to simplify restorative procedures by eliminating separate adhesive steps; however, their bonding performance, mechanical properties, and biological properties remain controversial. This study evaluated a newly developed SAFC (SA-100R) compared with three commercial SAFCs (Fusio Liquid Dentin, Constic, and Vertise Flow) and a conventional composite (Clearfil AP-X used with a two-step self-etch adhesive). Microtensile bond strength (μTBS) to dentin, failure modes, Knoop microhardness, resin–dentin interfacial morphology (SEM), elemental composition (EDX), and cytocompatibility (CCK-8, LIVE/DEAD staining) were assessed. The conventional composite system exhibited significantly higher µTBS than all SAFCs (p < 0.05). Among SAFCs, SA-100R showed the highest bond strength and no pre-testing failures. SEM revealed abundant resin tag formation only in the conventional system, while all SAFCs showed interfacial gaps, with SA-100R exhibiting the least pronounced gaps. SA-100R showed no significant cytotoxic effects across all tested concentrations. Within the limitations of this short-term in vitro investigation, SA-100R demonstrated improved bonding performance and favorable biocompatibility compared with existing SAFCs, suggesting its potential as a simplified restorative material. However, the conventional adhesive/composite system remains the reference standard for dentin bond strength, and long-term clinical performance remains to be established through further studies. Full article

Emerging sustainability demands and calls for lowering materials’ environmental impact have directed authors to examine a class of polymers characterised as covalent adaptable networks and referred to as vitrimers. In this study, composite plates were made using vitrimer resin as the matrix material and continuous unidirectional flax fibre fabrics as the reinforcement. A specific early-stage composite part production method is proposed to make the multi-ply flax/vitrimer composite plate. The development of natural fibre–reinforced vitrimer composites is of clear research interest as a promising approach towards sustainable and recyclable novel material systems. Specimens prepared with all the plies oriented 0° exhibited a 129.4 MPa tensile strength and a 12.4 GPa tensile modulus, indicating a 334% increase in tensile strength when compared to the average value of 29.8 MPa obtained for neat vitrimer specimens and a 1140% improvement in the tensile modulus compared to the 1.0 GPa reached for neat vitrimer. The specimens whose plies were oriented 90° are found to deliver a tensile strength of 12.2 MPa and a 1.3 GPa tensile modulus. Applying the classical composite material micromechanics equation to calculate the 0°-direction tensile modulus demonstrated a good agreement with the experimentally obtained value—a 9.6% difference was discovered. Proper fibre/matrix interfacial adhesion was detected when the flax/vitrimer specimens’ surfaces after fracture were examined under scanning electron microscope. The research findings on tensile mechanical properties reveal that the observed flax/vitrimer composites may be potential candidates for replacing typical synthetic fibre–reinforced materials rated for automotive applications and intended for in-plane loaded parts, particularly some inner-body vehicle elements. Full article