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This study aims to enhance dental resins' mechanical and thermal properties by reinforcing them with Al-doped ZnO/SiO2 nano-glass ceramic. The synthesis of the nano-glass ceramic involved the addition of Al-doped ZnO nano-powders to a diluted aqueous solution of liquid glass (25 mL) in ethanol (50 mL) at room temperature. The synthesized samples were characterized using TEM, EDS, FE-SEM, and XRD techniques. Various concentrations of the nano-glass ceramic (2, 5, 8, 10, and 15 wt.%) were then integrated with Bis-GMA and TEGDMA. The mechanical properties, including flexural strength (FS), compressive strength (CS), diameter tensile strength (DTS), and flexural modulus (FM), were evaluated. Thermal stability was assessed through TGA analysis, which indicated polymer degradation occurring between 300 and 450 °C. An increase in filler content correlated with enhanced thermal stability. The optimal mechanical properties were observed at a 7.5 wt.% filler content, showing significant improvements in FS (124.652 MPa), FM (9.87GPa), DTS (33.87 MPa), and CS (178.47 MPa). [ABSTRACT FROM AUTHOR]

Aims: The focus of this review is to assess the mechanical characteristics of using nanoparticles (NPs) in dental composites (DCs) to enhance strength and toughness. Materials and Methods: The review protocol was registered on PROSPERO with registration ID: CRD42024573647. A systematic search for relevant articles published between 2018 and July 2024 was conducted across electronic databases including Scopus, PubMed, WoS, and EBSCOhost. Studies meeting pre-defined eligibility criteria were included and assessed for methodological quality. Data on the mechanical properties of NPs on DCs were extracted from included studies. Metaanalysis was performed to assess the mechanical flexure strength associated with NPs in DCs. Results: A range of NPs including silicon dioxide, zirconium dioxide, titanium dioxide, graphene oxide, core-shell chlorhexidine/amorphous calcium phosphate, zincdoped mesoporous silica NPs, silver NPs, farnesol-loaded halloysite nanotube, calcium hydrogen phosphate dihydrate, niobium pentoxide, and chitosan were examined for incorporation into DCs. The use of organic and inorganic NPs has shown a significant boost in the mechanical characteristics of DCs. The forest plot demonstrated a significant increase in mechanical characteristics in DCs infused with NPs. Conclusion: It can be concluded that incorporating NPs in restorative dentistry holds promise for enhancing their mechanical properties and increasing strength and toughness. [ABSTRACT FROM AUTHOR]

Dental caries is the most widespread form of disease, affecting over 90% of the global population. Amalgam fillings, which have been in use for nearly two centuries, will face an European Union ban by 2025. Although photocomposite fillings are a suitable alternative, health concerns persist because of potential substance release into the oral cavity. This study aimed to evaluate the release of photoinitiator substances and monomers from dental materials into various solvents at different temperatures over 30 days. Cylindrical specimens of the composite resins were submerged in different extraction solutions and incubated at 37 and 50°C. The findings demonstrated that both the extraction solvent and extraction temperature significantly influenced the quantity of leachables (p < 0.05). Furthermore, most leachables were released within the initial days, although some monomers continued to elute for over 30 days. The estimated daily intake was calculated for the worst‐case scenario, confirming the biocompatibility of the composite fillings. The weight loss of dental materials ranged up to 3.5% after 30 days, regardless of the extraction conditions and dental material (p > 0.05). In conclusion, this study contributes to filling several research gaps in the field by addressing the biocompatibility of various dental materials through quantitative and qualitative analyses supported by statistical evaluation. [ABSTRACT FROM AUTHOR]

This article explores the properties of composite materials employed in dental fillings. A traditional nano-hybrid composite containing nanofiller particles exceeding 82% by weight served as a benchmark. The remaining samples were fabricated from ormocer resin, maintaining an identical nanofiller content of 84%. In all specimens, the nanoparticles were dispersed randomly within the matrix. This study presents findings from investigations into surface geometry, hardness, wettability, and tribological behavior. The microscopic observations revealed that ormocer-based samples exhibited greater surface roughness than those composed of the traditional composite. Hardness testing indicated that both ceramic addition and sample preparation significantly influenced mechanical properties. Ceramic-enhanced samples demonstrated superior hardness, surpassing the reference composite by 30% and 43%, respectively. Contact angle measurements revealed hydrophilic characteristics in the classic composite, contrasting with the hydrophobic nature of ceramic-containing samples. Tribological evaluations revealed the superiority of the classic composite in terms of friction coefficients and volumetric wear compared to ormocer-based materials. [ABSTRACT FROM AUTHOR]

A 3-D printing method to produce dental prostheses of complex shapes from a commercial, photocurable resin-ceramic slurry is developed and optimized. The microstructure, mechanical properties and wear behavior of the resulting material are evaluated and compared with a conventional/control sample and other ceramic-polymer dental composites. Commercial resin-ceramic dental slurries can be successfully extruded and appropriately photocured in a low cost 3-D printing system to produce cost-efficient complex dental parts that could be used in indirect restorations. The printing process does not appreciably introduce defects in the material and the 3-D printed composites exhibit mechanical properties (hardness, elastic modulus) and wear resistance comparable to the control material and analogous, conventional dental composites. The main wear mechanisms under sliding contact against a hard antagonist are plastic deformation at the asperity level and ceramic particle pull-out due to filler/matrix interfacial weakness. [ABSTRACT FROM AUTHOR]

Background: This study looks at the clinical applications of nanotechnology in dentistry, with an emphasis on implantology, preventive care, orthodontics, restorative dentistry, and endodontics. Methods: Following PRISMA criteria and registered in PROSPERO (ID: CRD 564245), a PubMed, Scopus, and Web of Science search was conducted for studies from January 2014 to April 2024. The criteria were English-language research on nanotechnology in dental coatings, with a focus on clinical trials and observational studies. The electronic database search yielded 8881 publications. Following the screening process, 17 records were selected for qualitative analysis. Results: Nanotechnology has revolutionized dentistry. In orthodontics, nanoparticles improve antibacterial characteristics, durability, and biocompatibility, lowering bacterial colonization and plaque. In preventative care, Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) combined with stannous fluoride (SnF2) and nano-sized sodium trimetaphosphate (TMPnano) substantially remineralizes enamel. Nanostructured surfaces in dental implants, particularly those containing calcium, improve osseointegration and stability. Nanoparticles in restorative dentistry improve composite and adhesive strength, aesthetics, and longevity. Conclusions: Nanotechnology improves dental materials and equipment, resulting in better treatment outcomes and increased patient comfort. Its integration provides more effective treatments, which improves dental care and patient outcomes. More research is needed to overcome present problems and expand nanotechnology's medicinal applications. [ABSTRACT FROM AUTHOR]

In clinical applications, resin‐based dental composites primarily face challenges with fractures and secondary caries. To overcome these issues, the physical characteristics of dental composites, especially mechanical properties, need to be improved. Hydroxyapatite (HA), present in the structure of the teeth, is preferred due to its biological properties, and zirconia (ZrO2) nanoparticles are known to enhance the mechanical properties of this type of composites. The aim of this study is to develop resin‐based dental composites containing HA and ZrO2 nanoparticles. The study also aims to explore the synergistic effect of these two nanoparticles on the physical properties of the developed composites. Composites with nine different compositions were prepared by mixing the components with the help of a mortar mill. The flexural and compressive strength, polymerization shrinkage, depth of cure and water sorption, and solubility properties of the prepared composites have been investigated. All composites have been found to meet the requirements of ISO 4049 standard. Among them, composite containing 5 wt. % HA and 1 wt. % ZrO2 (H5Z1) has exhibited the highest flexural strength with an increase of 58% compared to the control sample, and composite containing 3 wt. % HA and 2 wt. % ZrO2 (H3Z2) has exhibited the highest compressive strength with an increase of 22% compared to the control sample. Other physical properties of the composites have been found to be in an acceptable level. Highlights: Dental composites with HA and ZrO2 fillers were developed by a mortar mill.Synergistic effect of HA and ZrO2 nanoparticles was investigated.Mechanical properties of dental composites were significantly improved.Physical properties of dental composites were found to be at acceptable levels.Depth of cure decreases with increasing HA and ZrO2 loading. [ABSTRACT FROM AUTHOR]

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In recent years, hydroxyapatite, as a ceramic material, has been a subject of growing interest due to its optimal biological properties, which are useful especially in medical and dental applications. It has been increasingly used in dentistry as a filler in composites. Nevertheless, research has shown a deterioration of their mechanical properties. The aim of this study was to investigate the influence of the content of hydroxyapatite together with fluorine and silver on the mechanical properties of a hybrid composite used in conservative dentistry. The authors compared specimens of commercial hybrid composite with specimens of experimental hybrid composite containing 2 wt% and 5 wt% of hydroxyapatite powder with fluorine and silver. The composite specimens were subjected to hardness and impact strength measurements, as well as bending, compression, and tribological wear tests. The research results indicate that the mechanical properties of composites are influenced by the type and amount of filler used. Composite containing 2 wt% of hydroxyapatite powder along with calcium fluoride and silver provided acceptable results. [ABSTRACT FROM AUTHOR]

This study evaluates the wear resistance of dental paste-like bulk-fill composites compared to conventional paste-like composite resins using an intraoral scanner and 3-D analyzing software. Six different dental composite materials, including five bulk-fill composites and one conventional composite, were tested alongside natural human enamel as a control group. A computer-controlled chewing simulator for wear testing. A one-way ANOVA test was used to identify any significant differences between the means of the tested dental composite materials α=0.05. The results showed variability among bulk-fill composites, with some demonstrating wear resistance similar to conventional composites (p<0.05). Human enamel displayed the lowest wear values, but some bulk-fill composites matched this resistance(p>0.05). Significant variability was observed among bulk-fill composites but the results were comparable to those of conventional composites. The enamel control group demonstrated the lowest wear values, with some bulk-fill composites showing similar wear resistance. This study provides valuable information about the wear resistance of contemporary bulk-fill composite materials, commonly used in current clinical practice, contributing to enhancing clinical procedures. [ABSTRACT FROM AUTHOR]

Dental caries and dental restorations possess a long history and over the years, many materials and methods have been invented. In recent decades, modern techniques and materials have brought complexity to this issue, which has created the necessity to investigate more and more to achieve durability, consistency, proper mechanical properties, efficiency, beauty, good colour, and reduced costs and time. Combined with the recent advances in the medical field, mechanical engineering plays a significant role in this topic. This work aims at studying the elasto-static response of a human molar tooth as a case study, respecting the integral property of the tooth and different composite materials of the dental restoration. The structural integrity of the case study will be assessed through advanced numerical modelling resorting to meshless methods within the stress analysis on the molar tooth under different loading conditions. In this regard, bruxism is considered as being one of the most important cases that cause damage and fracture in a human tooth. The obtained meshless methods results are compared to the finite element method (FEM) solution. The advantages and disadvantages of the analysed materials are identified, which could be used by the producers of the studied materials to improve their quality. On the other hand, a computational framework, as the one presented here, would assist the clinical practice and treatment decision (in accordance with each patient's characteristics). [ABSTRACT FROM AUTHOR]

The surface characteristics of the restorative material are essential to its longevity. Since resin composites are polymeric-based materials, they could be degraded when exposed to oral conditions and chemical treatment. Certain chemical solutions, such as fluoride varnish, have the potential to deteriorate the resin composite's surface properties such as gloss and hardness. The current study aimed to assess and compare the surface gloss and hardness of different types of dental resin composites (nanohybrid, ormocer, bulk-fill flowable direct composites, and indirect CAD/CAM resin composite blocks (BreCAM.HIPC)) after a single application of Bifluorid 10 varnish. A total of 80 disc-shaped resin composite specimens were evenly distributed in four groups of 20 specimens. These were divided into two equal subgroups of specimens with topical fluoride (TF) application (n = 10) and without TF application (n = 10). The specimens were examined for surface gloss and hardness. Independent sample t-test was used to investigate statistically the effect of TF on the gloss as well as the hardness of each material. One-way ANOVA and post hoc tests were used to assess the difference in gloss and hardness among the materials without and with TF application. The significance level was adjusted to p ≤ 0.05. The results of gloss showed that the TF application led to a significant reduction in gloss values of all tested composites. The gloss among the various materials was significantly different. The TF had no significant effect on the hardness of nanohybrid, bulk-fill flowable, and BreCAM.HIPC composites (p = 0.8, 0.6, and 0.3, respectively). On the other hand, the hardness of ormocer was significantly reduced after TF application. Comparing the different resin composite materials, the hardness significantly differed. This study concluded that surface gloss and hardness seem to be impacted by the type and composition of the resin composites and vary depending on fluoride application. [ABSTRACT FROM AUTHOR]

Silicon carbide fibers have superior flexural properties and chemical stability compared to glass fibers. We investigated the flexural strength and modulus of an experimental, short silicon carbide fiber-reinforced resin. Short silicon carbide fibers with lengths of ~0.5, 1, 2, and 3 mm were prepared and silanized. Urethane dimethacrylate and triethylene glycol dimethacrylate were mixed at a 70:30 wt% ratio and used as the matrix resins. Each length of short silicon carbide fibers and the matrix resin were combined using a mixing machine and then used for specimen preparation. The three-point bending test conditions were in accordance with ISO 4049:2009. The fracture surfaces of the specimens after the three-point bending test were observed using secondary electron images. The data were statistically analyzed with a one-way analysis of variance and Tukey's HSD test (α = 0.05). The flexural strength and modulus of the specimens containing 2 mm or 3 mm silicon carbide fibers were significantly higher than the other specimens. The river pattern was observed more clearly in specimens containing shorter silicon carbide fibers, although this pattern was observed in all specimens. [ABSTRACT FROM AUTHOR]

Introduction: Wet oral environment may have deleterious effects on performance of the composites due to influences of water sorption and solubility. The study evaluated the hydrolytic degradation caused because of water sorption and solubility of silorane and methacrylate-based dental composites. Methods: Ten disc samples (2 mm × 10 mm) were prepared. Samples were analyzed for water solubility and sorption according to ISO 4049:2000 regulations and tested for mass gain or loss following immersion in water or in artificial saliva at 1 day, 15 days, and 30 days period. Student's 't' test, repeated measures analysis of variance (ANOVA), and Tukey's post-hoc tests determined statistical significance of the experimental results with global significance set at P = 0.05. Results: Considerable sorption and solubility was observed with time in both materials on immersion. Silorane composites showed lower water sorption and solubility than methacrylate-based composite (MBC). Artificial saliva demonstrated higher sorption and solubility compared to distilled water. Conclusion: Silorane composites display enhanced hydrolytic stability even after a month of immersion in contrast to conventional methacrylate-based composites (MBCs), making it a better alternative to MBC resins clinically. [ABSTRACT FROM AUTHOR]

After a brief review of current restorative materials and classifications, this article discusses the latest developments in polymer-based direct filling materials, with emphasis on products and studies available in the last 10 years. This will include the more recent bulk-fill composites and self-adhesive materials, for which clinical evidence of success, albeit somewhat limited, is already available. The article will also introduce the latest cutting edge research topics on new materials for composite restorations, and an outlook for the future of how those may help improve the service-life of dental composite restorations. [ABSTRACT FROM AUTHOR]

Different kinds of interactions between the restorative material and mineralized dental tissues result in secondary caries around dental composites. Of these, the mechanical interactions have to be carefully investigated. Due to the elastic mismatch between dental tissues and the composite restoration, complex stresses and strains develop at their interface. This complex mechanical environment disturbs the demineralization-remineralization equilibrium of dental hard tissues. The fluid flow both over and within enamel and dentin, associated with their complex ultrastructure and mechanical behavior, is a key factor. It is known that external mechanical loading can indirectly promote the dissolution of enamel and dentin through a pumping action of cariogenic fluids in and out of microgaps at the interface between mineralized tissues and composite. Mechanical loading can also directly influence the physicochemical behavior of dental hard tissues by inducing complex strain and stress fields on the crystal scale. It is important to consider both the direct and indirect paths by which mechanical loading can influence the apatite dissolution kinetics. Therefore, a systematic approach should be used to investigate the mechanism of secondary caries formation considering the tooth-composite interface as a unique complex in which each element has an influence on the other. [ABSTRACT FROM AUTHOR]

The durability of dental materials, when used in the mouth, is determined by their mechanical qualities. Composite resins are frequently used in dental restorations. Flexural tests and Vickers micro‐hardness tests on selected dental composite materials were performed in a universal testing machine (ASTM D790‐10 standard) and Vickers micro‐hardness tester (ASTM E384‐11e1standard). In this study, four different dental composite material samples are employed. The samples are dipped in a chewing tobacco solution for a few days before being removed and put through the tests. Also in this work, four different machine learning models were tested to see how well they could analyze the mechanical characteristics of dental composite materials when submerged in a chewing tobacco solution. For predicting the mechanical properties of dental composite specimens, four distinct machine‐learning models (extreme gradient boosting (XGBoost), adaptive boosting (AdaBoost), random forest, and k‐nearest neighbors (KNN) have been selected. AdaBoost machine learning model yields a coefficient of regression value of 0.9903 in predicting the flexural strength, whereas the XGBoost model gives a coefficient of regression value of 0.9890 in predicting the Vickers hardness distinctly better than the other models. [ABSTRACT FROM AUTHOR]

A new eugenyl dimethacrylated monomer (symbolled BisMEP) has recently been synthesized. It showed promising viscosity and polymerizability as resin for dental composite. As a new monomer, BisMEP must be assessed further; thus, various physical, chemical, and mechanical properties have to be investigated. In this work, the aim was to investigate the potential use of BisMEP in place of the BisGMA matrix of resin-based composites (RBCs), totally or partially. Therefore, a list of model composites (CEa0, CEa25, CEa50, and CEa100) were prepared, which made up of 66 wt% synthesized silica fillers and 34 wt% organic matrices (BisGMA and TEGDMA; 1:1 wt/wt), while the novel BisMEP monomer has replaced the BisGMA content as 0.0, 25, 50, and 100 wt%, respectively. The RBCs were analyzed for their degree of conversion (DC)-based depth of cure at 1 and 2 mm thickness (DC1 and DC2), Vickers hardness (HV), water uptake (WSP), and water solubility (WSL) properties. Data were statistically analyzed using IBM SPSS v21, and the significance level was taken as p < 0.05. The results revealed no significant differences (p > 0.05) in the DC at 1 and 2 mm depth for the same composite. No significant differences in the DC between CEa0, CEa25, and CEa50; however, the difference becomes substantial (p < 0.05) with CEa100, suggesting possible incorporation of BisMEP at low dosage. Furthermore, DC1 for CEa0–CEa50 and DC2 for CEa0–CEa25 were found to be above the proposed minimum limit DC of 55%. Statistical analysis of the HV data showed no significant difference between CEa0, CEa25, and CEa50, while the difference became statistically significant after totally replacing BisGMA with BisMEP (CEa100). Notably, no significant differences in the WSP of various composites were detected. Likewise, WSL tests revealed no significant differences between such composites. These results suggest the possible usage of BisMEP in a mixture with BisGMA with no significant adverse effect on the DC, HV, WSP, and degradation (WSL). [ABSTRACT FROM AUTHOR]

The potential of glass ceramics as applicable materials in various fields including fillers for dental restorations is our guide to present a new procedure for improvements of the mechanical properties of dental composites. This work aims to use Zn2SiO4 and SiO2–ZnO nano-materials as fillers to improve the mechanical properties of Bis-GMA/TEGDMA mixed dental resins. Zn2SiO4 and SiO2–ZnO samples were prepared and characterized by using XRD, FE-SEM, EDX, and FT-IR techniques. The XRD pattern of the SiO2–ZnO sample shows that ZnO crystallized in a hexagonal phase, while the SiO2 phase was amorphous. Similarly, the Zn2SiO4 sample crystallized in a rhombohedral crystal system. The prepared samples were used as fillers for the improvement of the mechanical properties of Bis-GMA/TEGDMA mixed dental resins. Five samples of dental composites composed of Bis-GMA/TEGDMA mixed resins were filled with 2, 5, 8, 10, and 15 wt% of SiO2–ZnO, and similarly, five samples were filled with Zn2SiO4 samples (2, 5, 8, 10, and 15 wt%). All of the 10 samples (A1–A10) were characterized by using different techniques including FT-IR, FE-SEM, EDX, and TGA analyses. According to the TGA analysis, all samples were thermally stable up to 200 °C, and the thermal stability increased with the filler percent. Next, the mechanical properties of the samples including the flexural strength (FS), flexural modulus (FM), diameter tensile strength (DTS), and compressive strength (CS) were investigated. The obtained results revealed that the samples filled with 8 wt% of SiO2–ZnO and 10 wt% of Zn2SiO4 had higher FS values of 123.4 and 136.6 MPa, respectively. Moreover, 8 wt% of both fillers displayed higher values of the FM, DTS, and CS parameters. These values were 8.6 GPa, 34.2 MPa, and 183.8 MPa for SiO2–ZnO and 11.3 GPa, 41.2 MPa, and 190.5 MPa for the Zn2SiO4 filler. Inexpensive silica-based materials enhance polymeric mechanics. Silica–metal oxide nanocomposites improve dental composite properties effectively. [ABSTRACT FROM AUTHOR]

Dental composites, through their structural diversity, represent the biomaterials frequently used in dental reconstructive therapy. The aim of our study was to observe the influence of different beverage environment conditions on seven types of obturation dental materials with different compositions. Our research focused on the surface modification analysis of the materials after the immersion in the different beverages; in this regard, we used the EDAX technique correlated with the energy-dispersive X-ray fluorescence (XRF). The pH of the drinks and that of the simulated saliva solution were determined by the titrimetric method, a sodium hydroxide solution 0.1 mol/dm3 was prepared and used for the titration. An amount of 5 mL of each analyzed solution was added to 15 mL of distilled water to obtain a dilution, to which 3 drops of phenolphthalein (as a color indicator—Phenolphthalein, 3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone, C20H14O4 Mw: 318.32, purchased from Merck) were added for each analysis. For each solution, the experiment was repeated three times in order to obtain accurate results. The results of our study materialized into a real plea for modifying the patients' behavior in terms of diet and preferences for acidic drinks, so that their quality-of-life valence can be improved by keeping the composite materials in a long-term unalterable state on the one hand; on the other hand, systemic damage can be prevented as well. [ABSTRACT FROM AUTHOR]

There is currently a lack of scientific reports on the use of composites based on UDMA resin containing HAp in conservative dentistry. The aim of this study was therefore to determine the effect of hydroxyapatite content on the properties of a hybrid composite used in conservative dentistry. This paper compares a commercial hybrid composite with experimental composites treated with 2% by weight (b/w), 5% b/w, and 8% b/w hydroxyapatite. The composites were subjected to bending strength, compression, and diametrical compression tests, as well as those for impact strength, hardness, and tribological wear. The obtained results were subjected to statistical analysis. Increased hydroxyapatite was found to weaken the mechanical properties; however, 2% b/w and 5% b/w hydroxyapatite powder was found to achieve acceptable results. The statistical analysis showed no significant differences. HAp is an effective treatment for composites when applied at a low concentration. Further research is needed to identify an appropriate size of HAp particles that can be introduced into a composite to adequately activate the surface and modification its composition. [ABSTRACT FROM AUTHOR]

The main objective of the present study was to evaluate the effect of the morphology of titanium dioxide nanofillers on the flexural strength and shear bond strength of the dental composite. Spherical and rhombic-shaped nano titanium dioxide fillers were synthesized via solvothermal method and were characterized. Subsequently, these fillers were incorporated into a flowable composite (Filtek™ Z350 XT Flowable Restorative) at 0.5 wt.% and 1.5 wt.% and the prepared specimens were stored in water for 24 h. The specimens were then evaluated for flexural strength using a universal testing machine. Similarly, the shear bond strength of modified composites to the tooth was evaluated and bond failures were analyzed using stereomicroscope magnification. Incorporation of nanofillers significantly enhanced the flexural strength of flowable composite (p = 0.009) with a significant increase at 0.5wt.% of spherical (p = 0.015) and rhomboidal-shaped fillers (p = 0.010). However, no statistically significant difference in flexural strength was observed among the different shapes of nanofillers. The results of our study did not show a significant effect on the shear bond strength of the composites. Thus the reinforcing ability of titanium dioxide nanofillers on dental composite was confirmed in this study, although the effect of using nanofillers with different morphology was not significant. [ABSTRACT FROM AUTHOR]

Composites with Nano fillers reinforced by polymer structures are gaining popularity in the field of prosthodontic. Composite materials are being developed to meet the needs of patients, such as heat cure acrylic resins, that used so much in the field of prosthodontic. To evaluate the flexure strength of heat-cure acrylic resin reinforcement with Nano aluminum oxide (Al2O3) after polishing with various abrasive materials. A total of seventy rectangular specimens of heat cure acrylic resin with dimensions (65 mm length x 10 mm diameter x 3 mm thickness) Samples were separated into main seven groups classifications based on the addition of Nano Al2O3 and surface's polishing with different abrasive materials. Each group have (10) specimens. The highest mean value of flexure strength was obtained in group (B) (87, while the lowest value was obtained in group (F) (56.9). It concluded that the flexure strength was decreased in groups (F and G) of heat-cured resin polished with diamond, while it was increased in groups (B and C) polished with pumice, followed by the control group(A), and then by groups (D and E) that polished with colloidal. [ABSTRACT FROM AUTHOR]

Resin composite mimics tooth tissues both in structure and properties, and thus, they can withstand high biting force and the harsh environmental conditions of the mouth. Various inorganic nano- and micro-fillers are commonly used to enhance these composites' properties. In this study, we adopted a novel approach by using pre-polymerized bisphenol A-glycidyl methacrylate (BisGMA) ground particles (XL-BisGMA) as fillers in a BisGMA/triethylene glycol dimethacrylate (TEGDMA) resin system in combination with SiO2 nanoparticles. The BisGMA/TEGDMA/SiO2 mixture was filled with various concentrations of XL-BisGMA (0, 2.5, 5, and 10 wt.%). The XL-BisGMA added composites were evaluated for viscosity, degree of conversion (DC), microhardness, and thermal properties. The results demonstrated that the addition of a lower concentration of XL-BisGMA particles (2.5 wt.%) significantly reduced (p ≤ 0.05) the complex viscosity from 374.6 (Pa·s) to 170.84. (Pa·s). Similarly, DC was also increased significantly (p ≤ 0.05) by the addition of 2.5 wt.% XL-BisGMA, with the pristine composite showing a DC of (62.19 ± 3.2%) increased to (69.10 ± 3.4%). Moreover, the decomposition temperature has been increased from 410 °C for the pristine composite (BT-SB0) to 450 °C for the composite with 10 wt.% of XL-BisGMA (BT-SB10). The microhardness has also been significantly reduced (p ≤ 0.05) from 47.44 HV for the pristine composite (BT-SB0) to 29.91 HV for the composite with 2.5 wt.% of XL-BisGMA (BT-SB2.5). These results suggest that a XL-BisGMA could be used to a certain percentage as a promising filler in combination with inorganic fillers to enhance the DC and flow properties of the corresponding resin-based dental composites. [ABSTRACT FROM AUTHOR]

Performance of dental materials is influenced by the abrasion and wear qualities of the materials in contact. Despite major advancements in dental materials over the previous few decades, restorative materials, particularly composite resins, continue to wear out. Wear resistance is directly influenced by several composite resin composition and structure characteristics. The focus of this research is to explore the tribological properties of two commercially available dental composite materials using ANSYS software (Tetric N-Ceram and Z350 Dentin Shade). In the experiment, a simple tribo-system that complies with American Society for Testing and Materials (ASTM) G99 is utilised, consisting of a cylinder-shaped pin that can be deformed, rotating around a disc under wet conditions. A comparison of Z350 dentin shade and Tetric n Ceram simulations for the same load and simulation time revealed that the former material had greater wear resistance. Simulation results showed that as the stress on the pin increases, wear for both materials increases, which is supported by experiment data from the pin-on-disc tribometer setup. [ABSTRACT FROM AUTHOR]

The innovation of nanocellulose as reinforcement filler in composites has been a topic of interest in the development of new biomaterials. The objective of this study was to investigate the mechanical properties of a nanohybrid dental composite made of rice husk silica and loaded with different percentages of kenaf nanocellulose. Kenaf cellulose nanocrystals (CNC) were isolated and characterized using a transmission electron microscope (TEM) (Libra 120, Carl Zeiss, Germany). The experimental composite was fabricated with fiber loadings of 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 6 wt% silane-treated kenaf CNC, and subjected to a flexural and compressive strength test (n = 7) using an Instron Universal Testing Machine (Shimadzu, Kyoto, Japan), followed by a scanning electron microscopic assessment of the flexural specimen's fracture surface using a scanning electron microscope (SEM) (FEI Quanta FEG 450, Hillsborough, OR, USA). Commercial composites Filtek Z350XT (3M ESPE, St. Paul, MN, USA), Neofil (Kerr Corporation, Orange, CA, USA) and Ever-X Posterior (GC Corporation, Tokyo, Japan) were used as a comparison. The average diameter of kenaf CNC under TEM was 6 nm. For flexural and compressive strength tests, one-way ANOVA showed a statistically significant difference (p < 0.05) between all groups. Compared to the control group (0 wt%), the incorporation of kenaf CNC (1 wt%) into rice husk silica nanohybrid dental composite showed a slight improvement in mechanical properties and modes of reinforcement, which was reflected in SEM images of the fracture surface. The optimum dental composite reinforcement made of rice husk was 1 wt% kenaf CNC. Excessive fiber loading results in a decline in mechanical properties. CNC derived from natural sources may be a viable alternative as a reinforcement co-filler at low concentrations. [ABSTRACT FROM AUTHOR]

Although salivary liquid can degrade constituents in resin‐based dental composites in short‐term incubations, there is a knowledge gap on how longer‐term aging impacts their bulk strength. We address this through extended aging studies with resin‐based dental composites in different environments. Two commercial composites (FIL and AEL) were aged aseptically at 37°C in air (A, control), artificial saliva (AS), and esterase enzyme amended AS (EAS). Diametral and pushout strength were measured after periods of 120–180 days. At 120 days, the diametral strength of composites aged in air was 69.9 ± 11.0 and 57.7 ± 3.31 MPa in FIL and AEL, respectively. These were significantly greater compared to composites aged in AS (32.1 ± 7.01 and 46.2 ± 9.38 MPa in FIL and AEL, respectively) or EAS (36.7 ± 8.49 and 43.5 ± 5.51 MPa in FIL and AEL, respectively). In contrast, pushout strength for both composites were smaller in A compared to those aged in AS and EAS, results attributed to AS absorption and polymer expansion. No significant change in either diametral or pushout strength occurred after 120 days. There was no significant difference between aging in AS and EAS, suggesting that esterase did not significantly decrease the bulk material strength to a greater extent than AS under the test conditions. Aqueous diffusivities for the composites ranged from 8.4 to 11 × 10−13 m2/s, with associated porosities ranging from 0.06% to 0.10%. These results indicate that saturation of a typical dental composite occurs over a time frame of 4–5 months, longer than typical aging studies. Together, the results demonstrate the importance of aging time on composite strength. [ABSTRACT FROM AUTHOR]

The aim of this work was to assess the limiting rate of eugenol (Eg) and eugenyl-glycidyl methacrylate (EgGMA) at which the ideal degree of conversion (DC) of resin composites is achieved. For this, two series of experimental composites, containing, besides reinforcing silica and a photo-initiator system, either EgGMA or Eg molecules at 0–6.8 wt% per resin matrix, principally consisting of urethane dimethacrylate (50 wt% per composite), were prepared and denoted as UGx and UEx, where x refers to the EgGMA or Eg wt% in the composite, respectively. Disc-shaped specimens (5 × 1 mm) were fabricated, photocured for 60 s, and analyzed for their Fourier transform infrared spectra before and after curing. The results revealed concentration-dependent DC, increased from 56.70% (control; UG0 = UE0) to 63.87% and 65.06% for UG3.4 and UE0.4, respectively, then dramatically decreased with the concentration increase. The insufficiency in DC due to EgGMA and Eg incorporation, i.e., DC below the suggested clinical limit (>55%), was observed beyond UG3.4 and UE0.8. The mechanism behind such inhibition is still not fully determined; however, radicals generated by Eg may drive its free radical polymerization inhibitory activity, while the steric hindrance and reactivity of EgGMA express its traced effect at high percentages. Therefore, while Eg is a severe inhibitor for radical polymerization, EgGMA is safer and can be used to benefit resin-based composites when used at a low percentage per resin. [ABSTRACT FROM AUTHOR]

Among the newest trends in dental composites is the use of graphene oxide (GO) nanoparticles to assure better cohesion of the composite and superior properties. Our research used GO to enhance several hydroxyapatite (HA) nanofiller distribution and cohesion in three experimental composites CC, GS, GZ exposed to coffee and red wine staining environments. The presence of silane A-174 on the filler surface was evidenced by FT-IR spectroscopy. Experimental composites were characterized through color stability after 30 days of staining in red wine and coffee, sorption and solubility in distilled water and artificial saliva. Surface properties were measured by optical profilometry and scanning electron microscopy, respectively, and antibacterial properties wer e assessed against Staphylococcus aureus and Escherichia coli. A colour stability test revealed the best results for GS, followed by GZ, with less stability for CC. Topographical and morphological aspects revealed a synergism between GZ sample nanofiller components that conducted to the lower surface roughness, with less in the GS sample. However, surface roughness variation due to the stain was affected less than colour stability at the macroscopic level. Antibacterial testing revealed good effect against Staphylococcus aureus and a moderate effect against Escherichia coli. [ABSTRACT FROM AUTHOR]

Due to the questionable durability of dental restorations, there is a need to increase the lifetime of composite restoration. The present study used diethylene glycol monomethacrylate/4,4′-methylenebis(cyclohexyl isocyanate) (DEGMMA/CHMDI), diethylene glycol monomethacrylate/isophorone diisocyanate (DEGMMA/IPDI) monomers, and bis(2,6-diisopropylphenyl)carbodiimide (CHINOX SA-1) as modifiers of a polymer matrix (40 wt% urethane dimethacrylate (UDMA), 40 wt% bisphenol A ethoxylateddimethacrylate (bis-EMA), and 20 wt% triethyleneglycol dimethacrylate (TEGDMA)). Flexural strength (FS), diametral tensile strength (DTS), hardness (HV), sorption, and solubility were determined. To assess hydrolytic stability, the materials were tested before and after two aging methods (I-7500 cycles, 5 °C and 55 °C, water and 7 days, 60 °C, 0.1 M NaOH; II-5 days, 55 °C, water and 7 days, 60 °C, 0.1 M NaOH). The aging protocol resulted in no noticeable change (median values were the same as or higher than the control value) or a decrease in the DTS value from 4 to 28%, and a decrease in the FS value by 2 to 14%. The hardness values after aging were more than 60% lower than those of the controls. The used additives did not improve the initial (control) properties of the composite material. The addition of CHINOX SA-1 improved the hydrolytic stability of composites based on UDMA/bis-EMA/TEGDMA monomers, which could potentially extend the service life of the modified material. Extended studies are needed to confirm the possible use of CHINOX SA-1 as an antihydrolysis agent in dental composites. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate leachable components (monomers) in high and low viscosity dental bulk-fill resin composites and conventional resin composite materials after polymerization. Six bulk-fill and six conventional dental resin composite materials were used in this study. The samples of each material (three sets of triplicates) were cured for 20 s with irradiance of 1200 mW/cm2 with a LED curing unit and immersed in a 75% ethanol solution at 37 °C. The eluates from each triplicate set were analyzed after 24 h, 7 days or 28 days using liquid chromatography coupled with triple quadrupole tandem mass spectrometry (LC-MS/MS). Detectable amounts of 2-Hydroxyethyl methacrylate (HEMA) were found in both Gradia materials and the amount observed across different time points was statistically different (p ˂ 0.05), with the amount in solution increasing for Gradia and decreasing for Gradia Direct flo. Bisphenol A diglycidildimethacrylate (BIS GMA) was found in Filtek and Tetric materials. Triethylene glycol dimethacrylate (TEGDMA) was detected in all materials. On the other hand, there were no statistically significant differences in the amounts of TEGDMA detected across different time points in either of the tested materials. Monomers HEMA, TEGDMA, 4-dimethylaminobenzoic acid ethyl ester (DMA BEE) and BIS GMA in bulk-fill and conventional composites (high and low viscosity) can be eluted after polymerization. The good selection of composite material and proper handling, the following of the manufacturer's instructions for polymerization and the use of finishing and polishing procedures may reduce the elution of the unpolymerized monomers> responsible for the possible allergic and genotoxic potential of dental resin composites. [ABSTRACT FROM AUTHOR]

(1) Background: The aim of the study was to determine the effect of modification with sintered hydroxyapatite (HAp) on selected mechanical and tribological properties of a flow-type composite. (2) Methods: Samples in the shapes of cuboidal beams (n = 120) and cylinders (n = 120) with the proper dimensions were prepared from a standard flow-type composite and others with the addition of 2% wt., 5% wt., and 8% wt. sintered hydroxyapatite. The bending strength, compression strength, diametral compression strength, impact resistance, hardness, and tribological properties were compared. (3) Results: In all cases, it was established that an increase in the amount of HAp caused a reduction in the bending, compression, and diametral compression strength. Increasing the amount of added HAp also reduced the impact strength, hardness, and wear resistance. However, the differences were statistically insignificant. (4) Conclusions: The addition of hydroxyapatite to a flow-type composite material worsened its mechanical and tribological properties; however, the obtained values were acceptable with 2% wt. and 5% wt. HAp. [ABSTRACT FROM AUTHOR]

Poly(methyl methacrylate) (PMMA)/nanobarium titanate (NBT) composite has potential application in denture base materials. The denture base materials should be stable in the wet environment and exhibit good mechanical properties. This study aimed to evaluate the effectiveness of titanate coupling agent (TCA) on NBT behavior after soaking in the simulated body fluid (SBF) and to determine the effect of SBF exposure on fracture toughness of the PMMA nanocomposites. Silanated (Si-NBT), titanated (Ti-NBT), and pure NBT (Un-NBT) at 5% concentration (by mass) were incorporated in the PMMA matrix. NBT was sonicated in MMA prior to mixing with PMMA. SBF absorption, solubility, and leaching were measured, and fracture toughness of the PMMA nanocomposites was evaluated after soaking. The results showed that Titanated samples displayed lower SBF absorption capability and solubility values than the silanated ones. Moreover, the leachability of filler elements (Ba and Ti) was substantially reduced by titanation (54% and 61%, respectively), whereas the Si-NBT/PMMA revealed values of 12.3% and 7% respectively. Significant differences in fracture toughness were observed among the tested samples after 6 weeks of aging in SBF (p < 0.05). Although no notable changes in the KIC of pure PMMA and Un-NBT/PMMA samples were detected, KIC was improved by 20% after titanation. In addition, the fracture toughness of the titanated samples was higher than that of the silanated ones by 26%. In conclusion, TCA exhibited better stability in moisture than silane. Degradation resistance to moisture obtained with titanated NBT could lead to the promotion of clinical longevity of the composites. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the knowledge, attitude, and practice regarding the use of composites for orthodontic purposes among dental students. The questionnaire was designed to evaluate knowledge, attitude, and awareness. Google Forms was used for the distribution of questions. This is a questionnaire survey based on knowledge, attitude, and awareness regarding the use of composites for orthodontic purposes among dental students; 86% of them had awareness regarding the use of composites for orthodontic purposes, wherein the remaining 14% were not aware. Considering the limitations of the study groups, we can conclude that the knowledge, attitude, and awareness regarding the use of composites for orthodontic purposes among dental students were good. However, there is still a lack of knowledge in few perspectives which can be overcome with continuous dental education programs and lectures [ABSTRACT FROM AUTHOR]

This study aimed to determine the effect of the testing method configuration on the bi-axial flexural strength (BFS) of three resin-based dental composites (RDCs). A total of 180 disc-shaped samples (12 mm diameter x 1 mm thickness) for each RDC were fabricated using split back nylon mould. The BFS was determined for specimens made in three commercial RDCs; microhybrid (MH), nanofilled paste (NFP) and nanofilled flowable (NFF) using the ring-on-ring (RoR; n = 90 for each RDC specimens) and ball-on-ring (BoR; n = 90 for each RDC specimens) configurations at a cross-head speed of 1 mm/min. RDC specimens of MH and NFP tested in the BoR configuration showed higher mean BFS values compared to those tested in the RoR configuration. (p < 0.001). The effect of test configuration on BFS values was insignificant for the specimens belonging to the NFF group (p = 0.207). Moreover, the Weibull modulus of NFF in the RoR configuration was statistically lower compared to those for NFF in the BoR configuration as the 95% confidence interval of Weibull modulus did not overlap. The specimen support and testing configuration significantly impacted the BFS value of the RDCs. The Weibull statistics appeared to be inappropriate for all kinds of RDCs. [ABSTRACT FROM AUTHOR]

In this present study, the preference selection index method (PSI) was applied to identify the best formulation among ceramic fillers such as glass ionomer cement (GIC), nanosilica and nanoalumina nanofiller in the dental composites. The comparative assessment of the effect of nanofillers (nanoalumina and nanosilica fillers) and glass ionomer cement has been evaluated. Dental composites with 0, 10, and 20 wt% of nanoalumina, nanosilica and glass ionomer cement were fabricated. These composites were analyzed for physico‐mechanical and wear properties. The PSI multi‐criteria decision making technique was used to rank the composites with various filler content. The performance defining attributes for the comparative assessment were set as void content, hardness, compressive strength, flexural strength, diametral tensile strength, and wear properties against load and speed. The PSI of dental composite reinforced with 20 wt% nanosilica (DCSi‐20) was maximum (0.896) followed by dental composite reinforced with 20 wt% glass ionomer (DCGi‐20) (0.889) and hence DCSi‐20 demonstrated as most preferred dental composite material followed by DCGi‐20. DC‐0 showed the least preference dental composite materials on the basis of desirable physical, mechanical, and wear properties. Finally, it can be concluded that despite of more void content and low flexural strength, overall performance of glass ionomer is comparable with nanosilica and more significant with respect to nanoalumina. [ABSTRACT FROM AUTHOR]

Commercial bisphenol A‐glycol methacrylate (BisGMA)/triethyleneglycol‐dimethacrylate (TEGDMA) have been widely used as dental restorative material; however, the poor mechanical and anti‐wear properties greatly limited their applied range. In this study, iron‐containing hydroxyapatite (FeHA) nanoparticles that mimic the chemical composition and microstructure of natural bamboo rat incisor enamel were synthesized and used as reinforcement in BisGMA/TEGDMA resins. The as‐prepared polycrystalline FeHA have a rod like morphology with uniformly dispersed iron. The effects of nanoparticle–resin weight ratios on the mechanical properties, tribological properties, and bioactivity of FeHA‐BisGMA/TEGDMA resins were investigated. In vitro bioactivity of the studied resin composites in artificial saliva showed that a dense and continuous apatite layer was formed on the surface of the resin composite. Findings revealed that doping a suitable content of FeHA nanoparticle, especially at 0.75 wt% FeHA, would significantly improve the tribological and mechanical properties as well as bioactivity of the dental resin composites. [ABSTRACT FROM AUTHOR]

Bisphenol A-glycidyl methacrylate (bis-GMA) and urethane dimethacrylate (UDMA) are usually combined with low-viscosity monomers to obtain more desirable viscosity, handling characteristics and general properties. The present study determined the flexural strength (FS), flexural modulus (FM), diametral tensile strength (DTS), and hardness (HV) of five matrices and composites based on these resins. The polymerization shrinkage stress (PSS) was also studied for the composites. The polymer matrices were formed using bis-GMA and UDMA. TEGDMA, HEMA and HDDMA acted as co-monomers. The composites had 45 wt.% of filler content. The highest FS and FM were obtained from the UDMA/bis-GMA/TEGDMA/HEMA matrix and the composite (matrix + filler). The best DTS values were obtained from the UDMA/bis-GMA/HEMA matrix and the composite. One of the lowest values of FS, FM, and DTS was obtained from the UDMA/bis-GMA/HDDMA matrix and the composite. All the composites demonstrated similar hardness values. The lowest polymerization shrinkage stress was observed for the UDMA/bis-GMA/TEGDMA/HEMA composite, and the highest PSS was observed for the UDMA/bis-GMA/TEGDMA/HDDMA composite. The addition of HEMA had a positive effect on the properties of the tested materials, which may be related to the improved mobility of the bis-GMA and UDMA monomers. [ABSTRACT FROM AUTHOR]

Aim: The purpose of this study was to evaluate the mechanical properties of an experimental self-healing dental composite model (SHDC) composed of SiO2 nanoparticles with varying percentages of triethylene glycol dimethacrylate (TEGDMA) monomer and N,N-dihydroxyethyl-p-toluidine (DHEPT) amine microcapsules. Materials and methods: Microcapsules were prepared by in-situ polymerisation of PUF shells, as explained in our previous work. The model SHDC included bisphenol A glycidyl dimethacrylate (Bis-GMA:TEGDMA) (1:1), 1 wt% phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO), 0.5 wt% benzoyl peroxide (BPO) catalyst, 20 wt% silanised silica dioxide (SiO2) (15 nm) and (0, 2.5, 5, 7.5, 10 wt%) of microcapsules (120 ± 45 μm). Light transmission, hardness, degree of conversion (DC), flexural strength and elastic modulus of the SHDC model were measured. Results: The degree of conversion of the SHDC ranged from 73 to 76% 24 h after polymerisation. Hardness measurements ranged from 22 to 26 VHN (p > 0.05); however, the flexural strength was adversely affected from 80 to 55 MPa with increasing microcapsules of up to 10 wt% in the composites (p < 0.05). Conclusion: Only flexural strength decreased drastically ~30% with increasing microcapsules (>10 wt%) in the composites. All other measured properties were not significantly affected. Accordingly, we recommend a stronger composite material that could be created by increasing the filler content distribution in order to achieve a hybrid self-healing composite with enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

Objective: The aim of the study was to evaluate the influence of filler content, degradation media and time on the mechanical properties of different dental composites after in vitro aging. Materials and Methods: Specimens (1 mm3) of three commercially available composites (GrandioSO®, Arabesk Top®, Arabesk Flow®) with respect to their filler content were stored in artificial aging media: artificial saliva, ethanol (60%), lactic acid (pH 5) and citric acid (pH 5). Parameters (Vickers microhardness, compressive strength, elastic modulus, water sorption and solubility) were determined in their initial state (control group, n = 3 for microhardness, n = 5 for the other parameters) and after 14, 30, 90 and 180 days (n = 3 for microhardness, n = 5 for the other parameters for each composite group, time point and media). Specimens were also characterized with dynamic-mechanical-thermal analysis (compression tests, F = ± 7 N; f = 0.5 Hz, 1 Hz and 3.3 Hz; t = 0–170 °C). Results: Incorporation of fillers with more than 80 w% leads to significantly better mechanical properties under static and dynamic compression tests and a better water sorption behavior, even after chemical degradation. The influence of degradation media and time is of subordinate importance for chemical degradation. Conclusion: Although the investigated composites have a similar matrix, they showed different degradation behavior. Since dentine and enamel occur only in small layer thickness, a test specimen geometry with very small dimensions is recommended for direct comparison. Moreover, the use of compression tests to determine the mechanical parameters for the development of structure-compatible and functionally adapted composites makes sense as an additional standard. Clinical relevance Preferential use of highly filled composites for occlusal fillings is recommended. [ABSTRACT FROM AUTHOR]

We compare the clinical-technological and physicomechanical properties of hybrid domestic and foreign composites obtained by light polymerization. The specific features of the fracture of materials under the action of local loads applied by the Hertz indentation test with the use of acoustic emission (AE) are investigated. The polymers are ranked according to the degree of water absorption and the value of fracture load. By using the energy criterion for identification of the types of fracture by AE signals, the fraction of brittle fracture is estimated for each material. According to the results of complex analysis of the research data, we make recommendations concerning the proper choice of the composites that can be efficiently used in the dental practice. [ABSTRACT FROM AUTHOR]

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Introduction: The durability and longevity of composite restoration are much dependent on the accurate delivery of the energy required to polymerise the material. This study aimed to investigate the extent to which undergraduate dental students acquire and retain light‐curing skills following hands‐on training. Materials and Methods: Hands‐on training comprises faculty tutoring for critical aspects of the light‐curing procedure, such as distance and angulation of the light‐curing tip. Assessments of the students' ability to deliver a specified radiant exposure to class III and I simulated RBCs using a dental simulator (MARC‐PS®) at three different time points after the training. Data were analysed using repeated measure ANOVA. Results: Immediately after the training, students' performance on curing was improved (p <.05). Overall, the radiant exposure increased after training, but the students lost some of the benefits with time. For curing in the anterior section (anterior sensor‐class III), the mean radiant exposure values increased by approximately 20% after the training. After 2 years, the values were 15% greater than baseline values. For curing in the posterior section (posterior sensor‐class I), the mean radiant exposure values increased by approximately 150% after the training. A significant decrease (p <.05) was observed; however, the radiant exposure values were still 82% greater than the baseline after 2 years. Conclusion: A hands‐on training dedicated to light‐curing procedures facilitated acquisition and retention up to a 2‐year follow‐up of skill on how light cure composite inside the mouth. The training was more relevant for curing in posterior areas, where orientation can significantly impact light‐curing. A hands‐on training where the radiant exposure can be measure gave objective measurement metrics to guide the curing performance. This approach is an effective means of teaching practical skills to dental students. [ABSTRACT FROM AUTHOR]

Introduction. Secondary caries is the most important reason for replacement and removal of restorative materials containing composite resins, because caries causes infectious complications and many bacteria, including Streptococcus mutans and lactobacilli, which have been isolated from cariogenic plaques, once known that composites based on resins favour the growth of Streptococcus. Therefore, the use of composite resins with antimicrobial properties for the prevention of secondary decay will be very useful; to this end, we synthesized 4-amino-2H-chromen-2-one as a new antibacterial compound, used it in dental composites, and investigated its physical-mechanical properties. Materials and methods. In this experimental study, 4-amino-2H-chromen-2-one was synthesized by the reaction between 4-hydroxy coumarin and ammonium acetate and the antibacterial activity of flowable dental composites containing 0-5 wt% 4-amino-2H-chromen-2-one, as well as their mechanical and physical properties, influencing flowable dental composites, were investigated. Statistical analysis was performed using one-way ANOVA test (P < 0.001). Results and discussion. The direct contact test demonstrates that, by increasing the 4-amino-2H-chromen-2-one content, bacterial growth is significantly diminished (p<0.001). Average flexural strength results show that, with increasing 4-amino-2H-chromen-2-one until 2% in the composite, no significant difference was observed in flexural strength (p>0.001), while the mean of compressive strength results shows no significant difference between 0-4% groups (p>0.001). Conclusions. Incorporation of 4-amino-2Hchromen-2-one into flowable resin composites in 2% wt can reduce the activity of Streptococcus mutans. [ABSTRACT FROM AUTHOR]

Poly methyl methacrylate (PMMA) is the dominant acrylic that is widely used to produce partial and complete dentures. Denture fractures are caused by fatigue owing to repetitive masticatory, flexural and impact loads produced by dropping. The mechanical properties of dentures have been developed by reinforcing with various agents like rubbers, fillers and fibers. Progressively, novel dental materials reinforcement tactics have been developed following the advancement in Nano dentistry. Nonetheless, the issue pertaining to the superior mechanical properties of the PMMA still exists albeit it's biocompatible and aesthetic properties. In recent years, the nanostructure materials have received much attention due to their high surface area to volume ratio that boosts interaction and delivers new biological, physical, and chemical characteristics. Many studies have evaluated the usage of nanotubes and nanofiber in dental composites, however, the data estimating the reinforcement issue of nanotubes and nanofibers in PMMA have been scarce. This article is aimed to review the progress related to the development of mechanical properties of denture base materials in addition to the latest advances and prospective developments for PMMA acrylic resins reinforcement. Poly methyl methacrylate PMMA composites, strengthening of dentures, Nano-fillers surface treatment, biomedical Nano additives for mechanical improvement, Nano-fillers of PMMA, biomedical ceramic Nano-fillers, biomedical metallic materials as Nano-fillers, hybrid reinforcement of PMMA, biocompatibility of polymeric PMMA composite, biomaterial for dental applications. [ABSTRACT FROM AUTHOR]

The purpose of this in vitro study is to evaluate the effect of the incorporation of silanized and non-silanized silica nanoparticles (~ 160 nm) in mechanical properties and surface roughness of self-cured acrylic resins. Five groups of samples were produced (with six specimens each), following the ISO 20795-1:2013 specifications. In the control group (Ctrl), no particles were added in the resin composition. Non-silanized silica nanoparticles were added either into the polymer (0.7 wt%, group G1) or into the monomer (0.27 wt%, G2). Two equivalent groups were formed for composite resins with silanized nanoparticles (groups G3 with 0.7 wt% incorporated into the polymer and G4 with 0.27 wt% added into the monomer). Data were submitted to Shapiro-Wilk (α = 0.05) and ANOVA/Tukey (α = 0.05). Nanoparticle-loaded resins showed similar microhardness as the control and a reduced flexural strength (20–27%) which was neither dependent on the amount of filler added nor in the method of nanoparticle incorporation. Surface silanization caused no major improvement in the mechanical behavior of the nanoresins but appears to improve dispersibility, as indicated by a smaller surface roughness. [ABSTRACT FROM AUTHOR]

The purpose of this review was to identify the various factors involved in polymerization shrinkage of dental composites and to discuss possible strategies of overcoming this drawback. The final setting reaction of dental composite material is followed by polymerization shrinkage of the material which leads to shrinkage stress and strain. This shrinkage stress and strain could result in debonding of the material, cuspal flexure, fracture of the tooth, microleakage and poor mechanical properties. PubMed and Google scholar databases were used to search through the past 30 years of literature using selected search criteria "Dental composite*[TW] AND (shrinkage*[TW] OR stress*[TW] OR strain*[TW])" to identify articles/book chapters discussing polymerization shrinkage and possible solutions. In total, articles/book chapters met the criteria for inclusion in the literature review. There were multiple factors that were identified to have an impact on polymerization shrinkage and consequently shrinkage stress and strain, which included the composition and viscosity of the material, modulus of elasticity acquired by the material, rate of polymerization, configuration factor and degree of conversion. On the other hand, the methods which could help minimize shrinkage involved alteration to the material including change in particle size, incorporation of inhibitors, and addition of silorane as well as use of various clinical techniques. It can be concluded that various strategies have been implemented to overcome the shrinkage stress and strain related to dental composites, however, further research is required to help in the development of the material. In addition, improvement in the placement techniques of the material needs further exploration to reduce this complication. [ABSTRACT FROM AUTHOR]

The aim of this study was an in-situ synthesis of hydroxyapatite (HA) on cellulose fibers to be used as a new reinforcing agent for dental restorations. The microwave irradiation method was used for synthesis and the materials were characterized with analytical techniques. The prepared dental resin composites were mechanically tested by a universal testing machine and electrodynamic fatigue testing system. FTIR, XRD, SEM/EDS analysis confirmed the successful synthesis of HA on cellulose fibers. The Alamar blue biocompatibility assay showed more than 90% cell viability for the prepared cellulose/HA. The mechanical properties of resin composites improved with cellulose content from 30 wt.% to 50 wt.% in the polymer matrix. Substantially, increasing the cellulose/HA content from 40% to 50% improved the mechanical properties. The results suggested that HA could be successfully synthesized on cellulose fibers using microwave irradiation and contributed to improving the mechanical properties of dental resin composites. [ABSTRACT FROM AUTHOR]

Bonding of resin composite fillings, for example following root‐canal treatment, is a challenge because remaining gaps grow and lead to failure. Here, phase‐contrast‐enhanced micro‐computed tomography (PCE‐CT) is used to explore methods of non‐destructive quantification of the problem, so that countermeasures can be devised. Five human central incisors with damaged crowns were root‐filled followed by restoration with a dental post. Thereafter, the crowns were rebuilt with a resin composite that was bonded conventionally to the tooth with a dental adhesive system (Futurabond U). Each sample was imaged by PCE‐CT in a synchrotron facility (ID19, European Synchrotron Radiation Facility) with a pixel size of 650 nm. The reconstructed datasets from each sample were segmented and analysed in a semi‐automated manner using ImageJ. PCE‐CT at sub‐micrometre resolution provided images with an impressive increased contrast and detail when compared with laboratory micro‐computed tomography. The interface between the dental adhesive and the tooth was often strongly disrupted by the presence of large debonded gaps (on average 34% ± 15% on all surfaces). The thickness of the gaps spanned 2 µm to 16 µm. There was a large variability in the distribution of gaps within the bonding area in each sample, with some regions around the canal exhibiting up to 100% discontinuity. Although only several micrometres thick, the extensive wide gaps may serve as gateways to biofilm leakage, leading to failure of the restorations. They can also act as stress‐raising 'cracks' that are likely to expand over time in response to cyclic mechanical loading as a consequence of mastication. The observations here show how PCE‐CT can be used as a non‐destructive quantitative tool for understanding and improving the performance of clinically used bonded dental restorations. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to explore the effect of Chlorhexidine-loaded Halloysite nanotubes (HNT/CHX) fillers (diverse mass fractions from 1 to 10 wt.%) on physicochemical, morphological and biological properties of newly developed experimental dental resin composite, in order to compare with the properties of composites composed of conventional glass fillers. Methods: The dental resin composites were prepared by incorporating various proportions of HNT/CHX. Six different groups of specimens: control group and five groups composed of varied mass fractions of HNT/CHX (e.g., 1.0, 2.5, 5.0, 7.5 and 10 wt.%) as fillers in each group were fabricated. Mechanical properties of the composites were monitored, using UTM. The degree of conversion of dental resin composites and their depth of cure were also evaluated. Antimicrobial properties of dental composites were studied in vitro by applying agar diffusion test on strain Streptococcus mutans and cytotoxicity were studied using NIH-3T3 cell line. Results: The incorporation of varied mass fractions (1.0 to 5.0 wt.%) of HNT/CHX in dental resins composites enhanced mechanical properties considerably with significant antibacterial activity. The slight decrease in curing depth and degree of conversion values of composites indicates its durability. No cytotoxicity was noticed on NIH-3T3 cell lines. Significance: Consistent distribution of HNT/CHX as a filler into dental composites could substantially improve not only mechanical properties but also biological properties of dental composites. [ABSTRACT FROM AUTHOR]