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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]

Abstract 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. Graphical Abstract 3-D printing commercial resin-filler slurries creates cost-efficient tooth prostheses with properties akin to conventional dental composites

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]

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]

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]

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]

The composite consisting of bis-GMA/UDMA/HEMA/TEGDMA monomer mixture forming apolymer matrix filled with silanized silica (45 wt%) was modified with CTAB or DODAB quaternary ammonium salts (0.5‒2.0 wt%). The hardness, flexural strength as well as diametrical tensile strength of the composite before and after modification were evaluated. The type and amount of salt affected the hardness, flexural strength, and shrinkage stress; however, they did not influence the diametral tensile strength of the tested composites.

Copyright of Polimery is the property of Industrial Chemistry Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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]

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]

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]

Although efforts have been put into the research in polymer-infiltrated ceramic network composites (PICNs), data are needed to understand the relationship between surface roughness and flexural strength. In this work, a novel dental restorative composite was fabricated via infiltrating mixtures of Bis-GMA/TEGDMA and UDMA/TEGDMA into partially sintered porous sodium aluminum silicate blocks and curing. Bars with different surface conditions were produced by sanding with abrasive and polishing. Flexural strength was measured using three-point-bending. Scanning electron microscopy (SEM) was employed to observe the microstructure of surface areas. One-way analysis of variance was applied for statistical calculations, with p < 0.05 being considered significant. Weibull plots were used to evaluate the reliability of flexural strength. The results demonstrated that the flexural strength of the resultant composites was affected by the scratch direction and the value of roughness. The flexural strength increased with decrease of surface roughness. A higher strength value was found for parallel types than for vertical types with nearly the same surface roughness. A large roughness value and a scratch direction perpendicular to tensile stress produced a low Weibull modulus. Of particular importance with this work is that these factors should be taken into consideration when using PICNs as dental restorative composites.

Objective: The purpose of this study was to investigate the effect of Silver nanoparticle immobilized Halloysite Nanotubes (HNT/Ag) fillers on physicochemical, mechanical, and biological properties of novel experimental dental resin composite in order to compare with the properties of corresponding composites containing conventional glass fillers. Methods: Dental resin (Bis-GMA/TEGDMA with ratio 70/30) composites were prepared by incorporation of varied mass fraction of HNT/Ag. Experimental composites were divided into six groups, one control group and five experimental groups containing mass fraction 1 to 10.0 wt. % of HNT/Ag. Mechanical properties of the dental composites were recorded. Degree of conversion and depth of cure of the dental resin composites were assessed. Antimicrobial properties were assessed using agar diffusion test and evaluation of cytotoxicity were performed on NIH-3T3 cell line. Results: The inclusion of mass fractions (1–5 wt. %) of the HNT/Ag in dental resins composites, significantly improved mechanical properties. While, addition of larger mass fractions (7.5 and 10 wt. %) of the HNT/Ag did not show further improvement in the mechanical properties of dental resins composites. Theses composites also demonstrated satisfactory depth of cure and degree of conversion. A significant antibacterial activity was observed on S. mutans. No significant cytotoxicity was found on NIH-3T3 cell lines. Conclusion: The incorporation of HNT/Ag in Bis-GMA/TEGDMA dental resins composites resulted in enhancement in mechanical as well as biological properties for dental applications. Clinical significance: HNT/Ag containing dental composite is proposed to be highly valuable in the development of restorative dental material for patients with high risk of dental caries.

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]

• CaAl and MgAl LDH dental composites were developed with varying LDH loading. • Fluoride absorption/release cycles were studied (five recharges) in DW and AS. • Water uptake, solubility, cation release, and mechanical properties were studied. • LDH-composites repeatedly absorbed/released fluoride maintaining a sustained release. • Physico-mechanical properties of composites were maintained with LDH-composites. This study aims to incorporate 2:1 MgAl and 2:1 CaAl layered double hydroxides (LDHs) in experimental dental-composites to render them fluoride rechargeable. The effect of LDH on fluoride absorption and release, and their physico-mechanical properties are investigated. 2:1 CaAl and 2:1 MgAl LDH-composite discs prepared with 0, 10 and 30 wt% LDH were charged with fluoride (48 h) and transferred to deionized water (DW)/artificial saliva (AS). Fluoride release/re-release was measured every 24 h (ion-selective electrodes) with DW/AS replaced daily, and samples re-charged (5 min) with fluoride every 2 days. Five absorption-release cycles were conducted over 10 days. CaAl and MgAl LDH rod-shaped specimens (dry and hydrated; 0, 10 and 30 wt%) were studied for flexural strength and modulus. CaAl and MgAl LDH-composite discs (0, 10, 30 and 45 wt% LDH) were prepared to study water uptake (over 7 weeks), water desorption (3 weeks), diffusion coefficients, solubility and cation release (ICP-OES). CaAl LDH and MgAl LDH-composites significantly increased the amount of fluoride released in both media (P < 0.05). In AS, the mean release after every recharge was greater for MgAl LDH-composites compared to CaAl LDH-composites (P < 0.05). After every recharge, the fluoride release was greater than the previous release cycle (P < 0.05) for all LDH-composites. Physico-mechanical properties of the LDH-composites demonstrated similar values to those reported in literature. The solubility and cation release showed a linear increase with LDH loading. LDH-composites repeatedly absorbed/released fluoride and maintained desired physico-mechanical properties. A sustained low-level fluoride release with LDH-composites could lead to a potential breakthrough in preventing early stage carious-lesions. [ABSTRACT FROM AUTHOR]

Water sorption, high volumetric shrinkage, polymerization stress, and potential estrogenic effects triggered by leached compounds are some of the major concerns related to BisGMA-TEGDMA co-monomer systems used in dental composites. These deficiencies call for the development of alternative organic matrices in order to maximize the clinical lifespan of resin composite dental restorations. This study proposes BisGMA-free systems based on the combination of UDMA and a newly synthesized diurethane dimethacrylate, and evaluates key mechanical and physical properties of the resulting materials. 2EMATE-BDI (2-hydroxy-1-ethyl methacrylate) was synthesized by the reaction between 2-hydroxy-1-ethyl methacrylate with a difunctional isocyanate (1.3-bis (1- isocyanato-1-methylethylbenzene) – BDI). The compound was copolymerized with UDMA (urethane dimethacrylate) at 40 and 60 wt%. UDMA copolymerizations with 40 and 60 wt% TEGDMA (triethylene glycol dimethacrylate) were tested as controls, as well as a formulation based in BisGMA (bisphenol A-glycidyl methacrylate)-TEGDMA 60:40% (BT). The organic matrices were made polymerizable by the addition of DMPA (2.2-dimethoxyphenoxy acetophenone) and DPI-PF6 (diphenyliodonium hexafluorophosphate) at 0.2 and 0.4 wt%, respectively. Formulations were tested as composite with the addition of 70 wt% inorganic content consisting of barium borosilicate glass (0.7 μm) and fumed silica mixed in 95 and 5 wt%, respectively. All photocuring procedures were carried out by a mercury arc lamp filtered to 320–500 nm at 800 mW/cm2. The experimental resin composites were tested for kinetics of polymerization and polymerization stress in real time. Flexural strength, elastic modulus, water sorption, and solubility were assessed according to ISO 4049. Biofilm formation was analyzed after 24 h by luciferase assay. Data were statistically analyzed by one-way ANOVA and Tukey's test (α ≤ 0.05). In general, the addition of 2EMATE-BDI into the formulations decreased the maximum rate of polymerization (RP MAX), the degree of conversion at RP MAX (DC at RP MAX), and the final degree of conversion (final DC). However, these reductions did not compromise mechanical properties, which were comparable to the BT controls, especially after 7-day water incubation. The incorporation of 60 wt% 2EMATE-BDI reduced water sorption of the composite. 2EMATE-BDI containing formulations showed reduction in polymerization stress of 30% and 50% in comparison to BT control and TEGDMA copolymerizations, respectively. Biofilm formation was similar among the tested groups. The use of the newly synthesized diurethane dimethacrylate as co-monomer in dental resin composite formulations seems to be a promising option to develop polymers with low-shrinkage and potentially decreased water degradation. [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]

Layered porous ceramic used for polymer-infiltrated-ceramic-network materials (PICNs) may be a promising candidate for dental restoration. The effect of sintering temperature of ceramic green bodies on mechanical and optical properties of PICNs is unclear. The purpose was to fabricate PICNs and evaluate their mechanical and optical properties. Polymer-infiltrated layered silicates for dental restorative materials were prepared via infiltrating polymerizable monomers into partially sintered porous silicates and thermo-curing. Bending samples for flexural strength and fracture toughness were fabricated (sample numbers of n = 15). Vickers hardness and elastic modulus were measured via nano-indentation (n = 10). One-way ANOVA and Weibull statistics were used for statistical analysis. Optical property was characterized by spectral reflectance. Brittleness index was used to characterize the machinability of the materials. Microstructures and phase structures were investigated using scanning electron microscopy (SEM) and X-ray diffractometer (XRD), respectively. Flexural strength of polymer-infiltrated layered silicates varied from 91.29 to 155.19 MPa, fracture toughness ranged from 1.186 to 1.782 MPa·m1/2, Vickers hardness ranged from 1.165 to 9.596 GPa, and elastic modulus ranged from 25.35 to 100.50 GPa. The formed glass phases at 1200 and 1300 °C showed influences on corresponding optical property, which could be observed from spectral reflectance. A kind of PICNs was fabricated by infiltrating polymerizable monomers into layered porous ceramic networks. Sintering temperature could have dramatic effects on the mechanical and optical properties of porous ceramics and PICNs. These kinds of materials possess similar properties to that of natural tooth and could be used for dental restoration. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the effect of bioactive glass 45S5 (BG) in experimental composites on flexural strength (FS), flexural modulus (FM), modulus of resilience (MR), and material reliability after artificial aging in water for 1, 7, and 30 days, and an additional accelerated aging for 3 days in a 75 vol% ethanol-water solution. Materials and methods: Five experimental light-curable composites were prepared with 0–40 wt% of BG and a total filler load of 70 wt%. The resinous matrix was Bis-GMA/TEGDMA in 60:40 by weight. Mechanical properties were evaluated using a three-point bending test (ISO/DIN 4049:1998) with n = 20. Weibull statistics were used to assess material reliability. Additionally, the degree of conversion (DC) was assessed 24 h post-cure using FT-Raman spectroscopy. Results: FS and FM decreased linearly as the amount of BG was increased. The ISO 4049 requirement for a minimum FS of 80 MPa was fulfilled in experimental composites with up to 20 wt% of BG. Degradation of FS and FM with artificial aging was more extensive in materials with higher BG amounts. MR decreased as a function of BG amount and artificial aging. Material reliability (Weibull modulus) was stable through aging for composites with up to 10 wt% of BG. DC was negatively influenced by the BG amount and ranged from 64 to 81%. Conclusion: Increasing the amount of unsilanized BG fillers from 0 to 40 wt% resulted in a progressive decline in mechanical properties and a more extensive degradation during artificial aging. Clinical relevance: Bioactive fillers diminished the mechanical properties in a dose-dependent manner. [ABSTRACT FROM AUTHOR]

Copyright of Polimery is the property of Industrial Chemistry Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objectives The aim of this study is to evaluate the packing properties of uniform silica particles and their mixture with secondary particles yielding maximally loaded dental composites. We intend to verify the difference between the idealized models (the close-packed structures and the random-packed structures) and the actual experimental results, in order to provide guidance for the preparation of dental composites. The influence of secondary particle size and the resin composition on the physical–mechanical properties and the rheological properties of the experimental dental composites was also investigated. Methods Silica particles (S-920, S-360, and S-195) with average diameters of 920, 360, and 195 nm were synthesized via the Stöber process. Their morphology and size distribution were determined by field-emission scanning electron microscopy and laser particle sizer. A series of silica fillers, S-920, S-920+195, S-920+360, and S-920+360+195, were then formulated with two Bis-GMA/TEGDMA resins (weight ratios of 70:30 and 50:50). For these experimental dental composites, their maximum filler loadings were assessed and compared to the theory. The mechanical properties, degree of conversion, depth of cure, and polymerization shrinkage of these composites were then evaluated. Their rheological behaviors were measured with a rheometer. Results Unimodal S-920 had the maximally filler loading of 70.80 wt% with the 5B5T resin, close to the theoretical estimation of the random loose packing (71.92 wt%). The maximum loading of the S-920+360+195 filled composite was 72.92 wt% for the same resin, compared to the theoretical estimation of 89.29 wt% obtained for the close-packed structures. These findings indicate that random loose packing matches more closely to the real packing state for the filler formulations used. When maximally loaded, the composite with S-920+360+195 produced the best mechanical properties and the lowest polymerization shrinkage. The degree of conversion and depth of cure were higher with secondary particles added, and the viscosity of all unpolymerized pastes exhibited shear thinning behavior. Significance Theoretical estimations of filler packing structures provide a useful guidance in the design of multimodal filler formulations and the preparation of dental composites with higher filler loading, improved physical–mechanical properties. [ABSTRACT FROM AUTHOR]

Objectives: This study reports the evaluation of changes in crosslink structure and mechanical properties of dental microhybrid composite reinforced with clays when compared to silica nanofillers, which are already extensively used for this application. Materials and methods: A standardized resin matrix with a glycerolate dimethacrylate, triethylene glycol dimetha- crylate, and urethane dimethacrylate copolymers associated with a camphorquinone photoinitiator system was blended with 75wt% filler content. As fillers, two organically modified clays (hydrophilic silica and organomodified silica) and a boron-aluminum-silicate glass with 4 mm were used to obtain nanohybrid nanocomposites. The samples were prepared by light curing and were evaluated by measuring flexural strength, elasticity modulus, hardness, tensile resistance, and crosslinking. Results: The mechanical test results indicated that the system with 2.5% clay was better dispersed in the system, while the highest concentrations caused agglomeration of these clays. On the other hand, the silicas showed gradual gain in properties. The increase in concentration of all nanofillers reduced the crosslinking ability of the systems. This behavior can be explained because the clay's presence makes the reaction medium more viscous or because the fillers act as points of light absorption and scattering. [ABSTRACT FROM AUTHOR]

Calcium phosphates (CaPs)-containing composites have already shown good properties from the point of view of dental restorative materials. The purpose of this study was to examine the crucial mechanical properties of twelve hydroxyapatite- or tricalcium phosphate-filled composites. The raw and surface-treated forms of both CaP fillers were applied. As a reference materials two experimental glass-containing composites and one commercial dental restorative composite were applied. Nano-hardness, elastic modulus, compressive, flexural and diametral tensile strength of all studied materials were determined. Application of statistical methods (one-way analysis of variance and cluster agglomerative analysis) allowed for assessing the similarities between examined materials according to the values of studied parameters. The obtained results show that in almost all cases the mechanical properties of experimental CaPs-composites are comparable or even better than mechanical properties of examined reference materials. [ABSTRACT FROM AUTHOR]

This study presents comparative investigation of adding nanohydroxyapatite (HA) (5-20 wt.%) and mineral trioxide aggregate (MTA) (5-20 wt.%) on the physical, mechanical and thermomechanical characterization of dental composite. The performances of both experimental composites were assessed through various physical, mechanical and thermomechanical tests such as void content test, microhardness test, compressive strength test, dynamic mechanical analysis and thermogravimetric analysis. The result of experiment indicated that the addition of 5 wt.% of HA increased the water sorption, hardness and compressive strength by 50.47%, 13.46% and 62.35%, respectively, whereas the addition of 5 wt.% of MTA increased the water sorption, hardness and compressive strength by 19.23%, 100% and 5.44%, respectively. Dynamic mechanical analysis results revealed that the addition of 5 wt.% HA increased the storage modulus by 10.21%, whereas the addition of 5 wt.% of MTA decreased the storage modulus by 11.79%. The filler HA proved to be better choice in term of thermal stability behavior as compare to MTA filler. [ABSTRACT FROM AUTHOR]

This study investigated the effect of preheating an elastomeric urethane monomer (Exothane-24) experimental resin composite on its physicochemical properties. Two resin matrices were formulated: (a) 50 wt% Bisphenol-glycidyl methacrylate (Bis-GMA) and 50 wt% triethylene glycol dimethacrylate (TEGDMA); and (b) 20 wt% Exothane-24, 40 wt% Bis-GMA and 40 wt% TEGDMA. A photoinitiator system (0.25 wt% camphorquinone and 0.50 wt% ethyl-4-dimethylamino benzoate) and 65 wt% of the inorganic filler (20 wt% 0.05 μm silica and 80 wt% 0.7 μm BaBSiO 2 glass) were added to both matrices. These formulations were then assigned to four groups: Exothane-24 (E); Exothane-24 plus preheating (EH); no Exothane-24 (NE); and no Exothane-24 plus preheating (NEH). NEH and EH were preheated at 69 °C. The dependent variables were as follows: film thickness (FT); polymerization shrinkage stress (PSS); gap width (GW); maximum rate of polymerization (Rp max); and degree of conversion (DC). Data were statistically analyzed by two-way ANOVA and Tukey's test (α = 0.05). Preheating reduced FT for both composites. PSS and GW were significantly lower for EH, when compared with E. The DC for EH and NEH and the Rp max for EH increased significantly. Preheating improved most of the physicochemical properties (FT, PSS, GW, and DC) of the experimental resin composite containing Exothane-24. [Display omitted] • Preheating improved physicochemical properties of experimental resin-based composites. • The polymerization stress is reduced with the association of elastomeric urethane monomer and preheating procedure. • Preheated composites containing Exothane-24 showed smaller gap widths. [ABSTRACT FROM AUTHOR]

Epoxy resin/ Thermoplastic polymethyl methacrylate (PMMA)/SiO2 dental composites were synthesized successfully at last after the following two steps: polymerization of MMA act as the initiator at this first process. Then the obtained PMMA was incorporated into epoxy resin and SiO2 to prepare the hybrid thermosets. The structural characteristics of epoxy resin/ PMMA/SiO2 composites were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). What is more, the mechanical properties and water solubility of the composites have also been tested. It is found that the stability has been improved after adding SiO2 nanoparticles. In addition, the mechanical properties of composites which were modified by silica indicated that the mechanical properties of materials could be improved after preprocessing of SiO2 nanoparticles in epoxy resin/PMMA composites. Interference of epoxy resin produced magnetic adsorption and chemical reaction with the existence of hydroxyls, ether bonds and epoxy groups. In conclusion, the improvement in surface properties was ascribed to the enrichment of epoxy resin moiety on the surface of the nanostructured thermosets. [ABSTRACT FROM AUTHOR]

The effect of hybrid silica/poly(methylmethacrylate) (PMMA) nanoparticles on the properties of composites for dental restoration was evaluated. Hybrid nanoparticles with silica as core and PMMA as shell were obtained by a seeded emulsion polymerization process. Fourier transform infrared spectrum of the hybrid nanoparticles shows an intense peak at 1730 cm- 1, corresponding to carbonyl groups (CO) of the ester. The thermal stability of the hybrid particles decreases with increasing amounts of PMMA and the residual mass at 700 °C corresponds to the silica content in the hybrid particles. Composites were obtained by dispersing nanoparticles (silica or hybrid), as fillers, in a resin-bis glycidyl dimethacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) (40%/60% (w/w)). The paste was then placed in a mold and polymerized under light irradiation. During the preparation of the composites, with the hybrid nanoparticles, the monomers swell the PMMA shell and after photo-curing, a semi-interpenetrating network (semi-IPN) is obtained around the silica core. The properties of the composites, obtained using the hybrid nanoparticles, depend on the filler content and the amount of PMMA in the semi-IPN matrix. For composites with similar inorganic filler contents, the composites with low amounts of PMMA shell had higher modulus than those in which silica was used as the filler. [ABSTRACT FROM AUTHOR]

This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (SphSi), whiskers (Wh), silicon-doped whiskers (WhSi), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and SphSi groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon- doping have a potential to be part of the filler content of dental composites. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 101B: 1469-1476, 2013. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study is to evaluate the effects of temperature on the mechanical and tribological properties of three commercial posterior direct filling resin based restorative composite materials, Synergy (Coltene/Whaledent, Altstätten, Switzerland), Surefil (Dentsply/Caulk, New York, USA) and Alert (Pentron Clinical, Wallingford, USA). The aim of this paper was to evaluate how temperature influences; the hardness, flexural modulus and strength, elastic modulus, and wear of the listed commercial restorative materials. Three commercial resin composites were tested at several temperatures. A closed control system was used to ensure constant test conditions that simulated the temperatures found in an oral environment. For each of the tests, the following mechanical and tribological properties were determined, microhardness (Vickers micro-indentation), elastic modulus (determined both by dynamical methods and by bending tests), flexural resistance and work of fracture parameter (bending tests), and wear (reciprocating tests). Following the tests, the evaluation of the mechanical and tribological properties of the resins suggests that their performance in an oral environment can be significantly affected by temperature, especially the wear resistance. Surefil is the resin least sensitive to temperature variation, while Synergy exhibited the best resistance to wear with respect to temperature variation. [Copyright &y& Elsevier]

Glass-ceramic filler particles containing various amounts of fluoroapatite-mullite crystalline phases were synthesised using SiO2-Al2O3-P2O5-CaF2-CaO system as the base glass formulation. Different additives were used to promote crystallisation in this system. Composite samples were prepared by incorporating the silane treated glass-ceramic particles into the Bis-GMA/TEGDMA (60:40 mass ratio) epoxy matrix. Structural and microstructural characterisations were conducted using Fourier transform infrared spectroscopy, X-ray diffractometry and scanning electron microscopy (SEM). The mechanical properties of the light cured samples were examined by measuring flexural and diametral tensile strength, as well as conducting Vickers microhardness test. Results obtained in this study showed strong dependence of the flexural strength on the composition of the filler particles. Diametral tensile strength and microhardness values demonstrated lesser sensitivity to the filler composition. Microstructural examination of the samples by SEM revealed particle pull-out, debonding and crack deflection as the major energy consuming mechanisms in the fracture process. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Study and evaluation of fracture toughness, flexural and dynamic mechanical properties, and crosslink density of ternary thiol–ene–methacrylate systems and comparison with corresponding conventional methacrylate system were considered in the present study. Methods: Urethane tetra allyl ether monomer (UTAE) was synthesized as ene monomer. Different formulations were prepared based on combination of UTAE, BisGMA/TEGDMA and a tetrathiol monomer (PETMP). The photocuring reaction was conducted under visible light using BD/CQ combination as photoinitiator system. Mechanical properties were evaluated via measuring flexural strength, flexural modulus and fracture toughness. Scanning electron microscopy (SEM) was utilized to study the morphology of the fractured specimen's cross section. Viscoelastic properties of the samples were also determined by dynamic mechanical thermal analysis (DMTA). The same study was performed on a conventional methacrylate system. The data were analyzed and compared by ANOVA and Tukey HSD tests (significance level=0.05). Results: The results showed improvement in fracture toughness of the specimens containing thiol–ene moieties. DMTA revealed a lower glass transition temperature and more homogenous structure for thiol–ene containing specimens in comparison to the system containing merely methacrylate monomer. The flexural modulus and flexural strength of the specimens with higher thiol–ene content were lower than the neat methacrylate system. The SEM micrographs of the fractured surface of specimens with higher methacrylate content were smooth and mirror-like (shiny) which represent brittle fracture. Significance: The thiol–ene–methacrylate system can be used as resin matrix of dental composites with enhanced fracture toughness in comparison to the methacrylate analogous. [Copyright &y& Elsevier]

The objective of this study is to synthesize antibacterial methacrylate and methacrylamide monomers and formulate antibacterial fluoride-releasing dental composites. Three antibacterial methacrylate or methacrylamide monomers containing long-chain quaternary ammonium fluoride, 1,2-methacrylamido- N, N, N-trimethyldodecan-1-aminium fluoride (monomer I), N-benzyl-11-(methacryloyloxy)- N, N-dimethylundecan-1-aminium fluoride (monomer II), and methacryloxyldecylpyridinium fluoride (monomer III) have been synthesized and analyzed by nuclear magnetic resonance (NMR) and mass spectrometry (MS). The cytotoxicity test and bactericidal test against Streptococcus mutans indicate that antibacterial monomer II is superior to monomers I and III. A series of dental composites containing 0-6% of antibacterial monomer II have been formulated and tested for degree of conversion (DC), flexure strength, water sorption, solubility, and inhibition of S. mutans biofilms. An antibacterial fluoride-releasing dental composite has also been formulated and tested for flexure strength and fluoride release. The dental composite containing 3% of monomer II has a significant effect against S. mutans biofilm formation without major adverse effects on its physical and mechanical properties. The new antibacterial monomers can be used together with the fluoride-releasing monomers containing a ternary zirconiun-fluoride chelate to formulate a new antibacterial fluoride-releasing dental composite. Such a new dental composite is expected to have higher anticaries efficacy and longer service life. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To fabricate and characterize dental composites reinforced with various amounts of zirconia–silica (ZS) or zirconia–yttria–silica (ZYS) ceramic nanofibers. Methods: Control composites (70wt% glass particle filler, no nanofibers) and experimental composites (2.5, 5.0, and 7.5wt% ZS or ZYS nanofibers replacing glass particle filler) were prepared by blending 29wt% dental resin monomers, 70wt% filler, and 1.0wt% initiator, and polymerized by either heat or dental curing light. Flexural strength (FS), flexural modulus (FM), energy at break (EAB), and fracture toughness (FT) were tested after the specimens were stored in 37°C deionized water for 24h, 3 months, or 6 months. Degree of conversion (DC) of monomers in composites was measured using Fourier transformed near-infrared (FT-NIR) spectroscopy. Fractured surfaces were observed by field-emission scanning electron microscope (FE-SEM). The data were analyzed using ANOVA with Tukey''s Honestly Significant Differences test used for post hoc analysis. Results: Reinforcement of dental composites with ZS or ZYS nanofibers (2.5% or 5.0%) can significantly increase the FS, FM and EAB of dental composites over the control. Further increase the content of ZS nanofiber (7.5%), however, decreases these properties (although they are still higher than those of the control). Addition of nanofibers did not decrease the long-term mechanical properties of these composites. All ZS reinforced composites (containing 2.5%, 5.0% and 7.5% ZS nanofibers) exhibit significantly higher fracture toughness than the control. The DC of the composites decreases with ZS nanofiber content. Significance: Incorporation of ceramic nanofibers in dental composites can significantly improve their mechanical properties and fracture toughness and thus may extend their service life. [Copyright &y& Elsevier]

Abstract: Objectives: The study evaluates properties of an experimental dental composite consisting of a porous thermally sintered nano-silica as filler. The properties are compared with those of an experimental composite containing micro fillers and a commercially available nano-composite, Filtek Supreme® Translucent. Different models are used to predict the elastic modulus and strength of the composites. Methods: Nano-silica with primary particles of 12nm was thermally sintered to form nanoporous filer particles. The experimental composites were prepared by incorporating 70wt.% of the fillers into a mixture of Bis-GMA and TEGDMA as matrix phase. Having added photoinitiator system the composites were inserted into the test molds and light-cured. The microfiller containing composites were also prepared using micron size glass fillers. Degree of conversion (DC%) of the composites was measured using FTIR spectroscopy. Diametral tensile strength (DTS), flexural strength, flexural modulus and fracture toughness were measured. SEM was utilized to study the cross section of the fractured specimens. The surface topography of the specimens was investigated using atomic force microscopy (AFM). The specific surface area of the sintered nano silica was measured using BET method. The data were analyzed and compared by ANOVA and Tukey HSD tests (significance level=0.05). Results: The results showed improvements in flexural modulus and fracture toughness of the composites containing sintered filler. AFM revealed a lower surface roughness for sintered silica containing composites. No significant difference was observed between DTS, DC%, and flexural strength of the sintered nanofiller composite and the Filtek Supreme®. The results also showed that the modulus of the composite with sintered filler was higher than the model prediction. Significance: The thermally sintered nano-porous silica fillers significantly enhanced the mechanical properties of dental composites introducing a new approach to develop materials with improved properties. [Copyright &y& Elsevier]

Abstract: Objectives: The aims of this study were to formulate a novel fluoride-releasing dental composite and to evaluate its mechanical properties, fluoride release and recharge capabilities, water sorption and solubility. Methods: A fluoride-releasing dimethacrylate monomer containing a ternary zirconium fluoride chelate was synthesized. Three experimental fluoride-releasing composites were fabricated with different monomer formulas (wt.%)—(1) Control A: 40 BisGMA/40 TEDMA/20 UEDMA; (2) Experimental: 20 F-releasing monomer/20 BisGMA/40 TEDMA/20 UEDMA; (3) Control B: the same formula as Control A except that it contained 10wt.% (of total monomer) tetrabutylammonium fluoride (TBAF), which had a fluoride content equivalent to Experimental. All three materials had the same filler content: 55wt.% silanized fluoroaluminosilicate particles (0.8μm) and 10wt.% silanized fumed silica (14nm). All materials contained 0.17wt.% camphorquinone (CQ) as a photoinitiator and 0.69wt.% ethyl-4-dimethylaminobenzoate (4EDMAB) as an accelerator. The materials were tested for fluoride release (for 184 days), fluoride recharge, compressive and flexure strength, water sorption and solubility. The data were analyzed using ANOVA and Tukey-HSD tests, and Kruskal–Wallis test. Results: The experimental composite had significantly higher fluoride release and fluoride recharge capabilities than both Control composites. It had significantly better physical and mechanical properties than Control B. Significance: The combined use of the fluoride-releasing dimethacrylate monomer and fluoride-releasing filler can provide sustained high fluoride release and recharge as well as acceptable mechanical and physical properties. Simply adding organic fluoride salt in the monomer yields composites with poor mechanical and physical properties. [Copyright &y& Elsevier]

Hybridized zirconium amorphous calcium phosphate (ACP)-filled methacrylate composites make good calcium and phosphate releasing materials for anti-demineralizing/remineralizing applications with low mechanical demands. The objective of this study was to assess the effect of the particle size of the filler on the mechanical properties of these composites. Photo-curable resins were formulated from ethoxylated bisphenol A dimethacrylate, triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate and methacryloxyethyl phthalate. Camphorquinone and ethyl 4-N,N-dimethylaminobenzoate were utilized as components of the photoinitiator system. After 2 h of mechanical milling in isopropanol, an approximate 64% reduction in the median particle diameter was observed (27.48 μm vs. 9.98 μm) for unmilled and milled wet ACP, respectively. Dry ACP showed a 43% reduction in particle size from pre- to post-milling. As well as dry composites, those that had been immersed in aqueous media were evaluated for their Young's Modulus, water sorption, biaxial tensile, three-point flexural and diametral tensile strength. Mechanical milling the filler increased the volume of fine particles in the composite specimens, resulting in a more homogeneous intra-composite distribution of ACP and a reduction in voids. Since less water diffused into the milled composites upon aqueous exposure, a marked improvement in biaxial flexure strength and a moderate improvement in flexural strength over composites with unmilled ACP was observed. This improvement in the mechanical stability of milled Zr-ACP composites may help extend their dental applicability. [ABSTRACT FROM AUTHOR]

Summary: Objectives: The purpose of this study was to investigate the effect of ceramic fillers (containing leucite crystals) and their porosity on the mechanical properties of a new experimental dental composite in order to compare with the properties of composites containing conventional glass fillers. Methods: In this study, experimental composites were prepared by mixing the silane-treated fillers with monomers. Experimental composites were divided into four groups according to their filler type, amount and porosity. The monomers were composed of 70% Bis-GMA and 30% TEGDMA by weight for all groups. Glass and leucite-containing-ceramic were prepared as different filler types. In order to make fillers porous, leucite-containing-ceramic fillers were treated with HF acid. Camphorquinone and DMAEMA were used as photo initiator system. Post-curing was done for all groups before mechanical testing. Degree of Conversion of composites was measured using FTIR spectroscopy. The diametral tensile strength (DTS), flexural strength and flexural modulus were measured and compared among the groups. Results: The results showed that the stronger and more porous filler has a positive effect on flexural strength. Porosity of filler increased flexural strength significantly. No significant difference was found in DTS tests among the groups. Flexural modulus was affected and increased by using ceramic fillers. The type of the filler affected the DC of the composite and DC increased by post-curing. Significance: Flexural strength is one of the most important properties of restorative dental materials. Higher flexural strength can be achieved by stronger and more porous fillers. Investigation into the effect of filler on dental material properties would be beneficial in the development of restorative dental material. [Copyright &y& Elsevier]

Summary: Objectives: The depth-sensing micro-indentation testing was recently introduced for the characterization of dental composites. One of the critical issues raised was the possible influence of surface finish on material properties. The aim of this study was to investigate the effects of surface finish on the indentation modulus and micro-hardness of resin-based dental composite materials. Methods: The materials used included minifill (Z100, 3M ESPE), microfill (A110, 3M ESPE) and poly-acid modified (F2000, 3M ESPE) composites. The specimens were polished successively using SiC grinding papers of different grit size and diamond suspensions to achieve varying surface roughness. The arithmetic mean of the roughness (R a) was measured using profilometry. In the depth-sensing micro-indentation test, specimens (n=7) were indented to 10N with Vickers indenter and the load-displacement (P–h) data was obtained using a universal testing system. The indentation modulus (E in) and hardness (H) were then computed using the developed analytical solutions. Data was analyzed using ANOVA/post-hoc Scheffe''s test at significance level 0.05. Results: The polished specimens had surface roughness ranging from 0.02 to 0.81μm. The roughness of F2000 was significantly higher than A110 and Z100. The E in and H for Z100 ranged from 14.02 to 14.83GPa and 1.18 to 1.27GPa, respectively. E in for F2000 and A110 ranged from 12.25 to 13.82GPa and 5.26 to 5.52GPa and hardness ranged from 0.89 to 0.98GPa and 0.52 to 0.55GPa, respectively. Significance: The indentation modulus and hardness of dental composite restoratives were independent of the surface finish provided indenter penetration is sufficiently deep (h max/R a>30). [Copyright &y& Elsevier]

Objectives. The purpose of this study was to analyze the behavior in water, related to mechanical properties, of experimental composites for dental restoration.Methods. The studied materials were composed of a visible-light-curing monomer mixture (Bis-GMA and TEGDMA or HEMA) and micrometric, nanometric or a mixture of both sizes hydroxyapatite particles as a reinforcing filler. Filler particles were modified with a coupling agent (citric, hydrosuccinic, acrylic or methacrylic acid or silane). The hydrolytic stability of the evaluated materials was studied through total elution and water-uptake tests. Percent net-mass variation was daily monitored and analyzed as a function of time. Mechanical performance was examined through flexural properties and Vickers hardness. Morphological surface changes were observed with scanning electron microscopy. ANOVA statistical analysis was performed (P<0.05).Results. In general, the use of HEMA instead of TEGDMA did not substantially worsen the composite quality. Dental composites containing only nanometric particles of hydroxyapatite as a filler are unsuitable for clinical performance. Midway-filled composite resins loaded with micro-HAP particles, coated with citric, acrylic or methacrylic acid displayed low percent elution and water-uptake values. Mechanical properties were similar or even superior to those measured for silane treated particles.Significance. More research is needed to further improve the interaction of nano-HAP particles with the polymeric matrix, either as a single filler or, preferentially, mixed with micro-HAP, that will allow to increase the total loading of reinforcing filler and, hence, to improve the mechanical properties. [Copyright &y& Elsevier]

The purpose of this research is to demonstrate the usefulness of the synthesized hyperbranched multi-methacrylates (H-MMAs) in dental applications. We synthesized three hyperbranched multi-methacrylate oligomers and evaluated them as modifiers for use in the dental resin system: bisphenol A glycidyl dimethacrylate (BisGMA)/tri(ethylene glycol) dimethacrylate (TEGDMA). Their photo-polymerization activities, viscosity, mechanical properties, such as compression, diametral tensile, and flexural strength, were evaluated. H-MMAs (10%) modified dental resins have lower polymerization shrinkage and about 15% increase in mechanical strength compared to the Bis-BisGMA control. For example, H30-MMA has compressive, diametral tensile, and flexural strength of 576, 47, and 85 MPa, compared with the BisGMA control having 497, 43, and 77 MPa. In addition, hyperbranched polymer modified resins have higher glass transition temperature (Tg) and lower thermal expansion coefficient (α) than the control. This research is significant both for increasing our knowledge about hyperbranched multi-functional polymers as well as leading to new dental resin systems with better performance. [ABSTRACT FROM AUTHOR]

The effects of the fluorinated triethyleneglycol dimethacrylate (F-TEGDMA) on the mechanical properties of composites made with this monomer, under both dry and aged conditions, was investigated. Photo-polymerizable formulations of 50/50, 30/70 and 10/90 mol:mol% F-TEGDMA/BisEMA (F5E5, F3E7 and F1E9), and 50/50 mol/mol% TEGDMA/BisEMA (T5E5) and TEGDMA/BisGMA (T5G5) were mixed with 76 wt% of silanated BaSiO2 filler to form the experimental composite formulations. The experimental T5E5 and T5G5 formulations and a commercial composite HXR (Herculite XR, Kerr), having a similar formulation to the T5G5 group, served as the controls. The compressive strength (CS), diametral tensile strength (DTS), flexural strength (FS) and abrasive wear rate (WR) were determined and compared. Scanning electron microscopy (SEM) techniques were used to evaluate the fracture surfaces. ANOVA and Tukey-Kramer tests were used to determine between group differences. The study shows that replacing TEGDMA with F-TEGDMA does not significantly alter the CS, FS and WR but increases DTS of the composite materials. Conditioning in a simulated oral fluid of 75% alcohol for a 3 month period did not significantly affect the DTS of the materials. However, the alcohol conditioning did significantly affect the FS of all materials except material F1E9. This experimental formulation retained its original FS. This work suggests that small amounts of the fluorinated diluent may help resist chemical degradation in composites resin formulations. [ABSTRACT FROM AUTHOR]