Significant Difference In Compressive Strength Research Articles

Addition of nisin to high-viscosity glass-ionomer cement: a comparative in vitro study on antibacterial and physical properties.

Nisin is a lantibiotic effective against Gram-positive microorganisms such as Streptococcus mutans. The study aimed to determine the effect of the addition of nisin to high-viscosity glass-ionomer cement (HVGIC) on its antibacterial activity, setting time, surface microhardness, and compressive strength. 1 and 3% w/w nisin were added to HVGIC before mixing. Unmodified HVGIC was the control. Agar disc diffusion, direct contact test, and scanning electron microscopy (SEM) analysis were used to evaluate antibacterial activity against S. mutans. Setting time, surface microhardness, and compressive strength were measured using Gilmore needle apparatus, digital microhardness tester, and universal testing machine, respectively. Statistical analysis included Student's t test, one-way ANOVA with Tamhane's post hoc test, and repeated-measures ANOVA. As evidenced by the agar disc diffusion (p < 0.001), direct contact tests (p = 0.025), and SEM analysis of the S. mutans cell count and cell surface area (p = 0.049 and 0.003), 3% nisin had the strongest antibacterial activity. There was a dose-dependent increase in setting time (p = 0.005) and surface microhardness (p = 0.006), with no significant difference in compressive strength compared to control. The addition of 3% nisin to HVGIC enhances the antibacterial action against S. mutans and surface microhardness without adversely affecting setting time and compressive strength.

Study on NaOH improving the surface morphology of three-dimensional printed poly- L- lactic acid mesh scaffolds

To explore the effect of NaOH on the surface morphology of three-dimensional (3D) printed poly- L-lactic acid (PLLA) mesh scaffolds. The 3D printed PLLA mesh scaffolds were prepared by fused deposition molding technology, then the scaffold surfaces were etched with the NaOH solution. The concentrations of NaOH solution were 0.01, 0.1, 0.5, 1.0, and 3.0 mol/L, and the treatment time was 1, 3, 6, 9, and 12 hours, respectively. There were a total of 25 concentration and time combinations. After treatment, the microstructure, energy spectrum, roughness, hydrophilicity, compressive strength, as well as cell adhesion and proliferation of the scaffolds were observed. The untreated scaffolds were used as a normal control. 3D printed PLLA mesh scaffolds were successfully prepared by using fused deposition molding technology. After NaOH etching treatment, a rough or micro porous structure was constructed on the surface of the scaffold, and with the increase of NaOH concentration and treatment time, the size and density of the pores increased. The characterization of the scaffolds by energy dispersive spectroscopy showed that the crystal contains two elements, Na and O. The surface roughness of NaOH treated scaffolds significantly increased ( P<0.05) and the contact angle significantly decreased ( P<0.05) compared to untreated scaffolds. There was no significant difference in compressive strength between the untreated scaffolds and treated scaffolds under conditions of 0.1 mol/L/12 h and 1.0 mol/L/3 h ( P>0.05), while the compression strength of the other treated scaffolds were significantly lower than that of the untreated scaffolds ( P<0.05). After co-culturing the cells with the scaffold, NaOH treatment resulted in an increase in the number of cells on the surface of the scaffold and the spreading area of individual cells, and more synapses extending from adherent cells. NaOH treatment is beneficial for increasing the surface hydrophilicity and cell adhesion of 3D printed PLLA mesh scaffolds.

Miswak-Infused Glass Ionomer Cement: A Comparative In Vitro Analysis of Antibacterial Efficacy and Compressive Strength.

Glass ionomer cement (GIC) restorations are commonly used in primary dentition, due to their aesthetic appeal, self-adhesive nature, and biocompatibility. However, the material's limited antibacterial activity and inadequate mechanical strength highlight the necessity for modifying the material. The study aims to evaluate and compare the antimicrobial potency and compressive strength of GIC-incorporated Miswak extract with that of conventional GIC. After obtaining the Miswak extract, a modified GICwas formulated by combining the extract with the conventional GIC powder and liquid components, in three different ratios (Powder: Extract and Liquid), Group I (2:1:1), Group II (3:1:2), Group III (3:2:1), and the Group IV as control, which consist of unmodified/conventional GIC. To evaluate and compare the antibacterial efficacy of the modified and unmodified GIC, standard strains of Streptococcus mutans and Lactobacillus were utilized. For each group, the minimal inhibitory concentration (MIC) assay was tested. For the evaluation of compressive strength, cylindrical moulds were utilized in compliance with ISO 9917-1:2007 standards and tested using the universal testing machine (Instron, ElectroPuls®, Bangalore, IND). The highest force exerted at the point of specimen fracture was recorded to calculate the compressive strength values in MPa. The data obtained were analyzed using the StatisticalPackage for the Social Sciences (IBMSPSSStatisticsforWindows,IBMCorp., Version 24.0, Armonk,NY)software. The statistical analysis was conducted utilizing repeated measures of analysis of variance (ANOVA) to calculate the mean MICvalues and compressive strength, with pairwise comparisons assessed using Tukey's post hoc test. The results provedthat the antimicrobial properties of Miswak containing GIC performed better against S. mutans and Lactobacillus with a statistically significant difference when compared with group IV (p<0.05), it has been found that an increase in the concentration of extract increased the antimicrobial potency. Significant results were obtained in compressive strength where GroupII (41.49±3.6) and Group III (15.23±4.96) proved to be weaker than the control (62.69±2.58), while Group I showed no differences from the control group (p>0.05). It can be concluded that Group I was found to be better in terms of both antimicrobial properties and compressive strength, where no significant difference in compressive strength was identified when comparing Group I with Group IV. Thus, the overall study depicts that a lesser concentration of extract can be the best option in terms of good antimicrobial properties without altering its strength. Hence, the Miswak containing GIC could be a promising restorative material; further studies should include considering intraoral variables such as masticatory stress, moisture levels and in-vivo tests of this combination.

Evaluation of the Yttrium Oxide Effect on Some Mechanical Properties of (Type III) Dental Stone

For many years, gypsum compounds have been used in dentistry. They're used to make casts for various dental laboratory operations. Gypsum products have important characteristics such as "quality, abrasion resistance, compressive strength, hardness, linear setting expansion during setting, and detail replication". Additionally, the use of additives such as gum arabic, ferric oxide, calcium oxide, and calcium carbonate has greatly improved the compressive strength of gypsum products. The purpose of this study was to investigate the effects of yttrium oxide (Y2O3) addition on the hardness and compressive strength of dental stones. Thirty dental stone specimens of (type III) were prepared and separated into (3) groups: group (A) control group, no additives, group (B) 3% Y2O3, and group (C) 5% Y2O3. The control and experimental groups' mechanical parameters (surface hardness and compressive strength) were measured, and a Shore D hardness tester was used to indent the specimens. An electronic universal testing apparatus with computer control was used to conduct the compressive strength test. The Tukey-HSD test found no difference in surface hardness between the control and experimental groups, a non-significant difference in compressive strength between the control group and dental stone +3% Y2O3, and a significant difference in compressive strength between the control group and dental stone +5% Y2O3. Between dental stones with 3% and 5% Y2O3, there was a substantial difference in compressive strength. The addition of yttrium oxide at weight ratios of 3% and 5% to dental stone did not affect the surface hardness. The addition of 5% yttrium oxide decreased the compressive strengths.

Comparative analysis of self-cure and dual cure-dental composites on their physico-mechanical behaviour.

Clinical practitioners may have become familiar with the rapid transformation of dental composites. However, they may not scientifically understand the factors influencing the mechanical and physical properties. Scientific knowledge of filler-resin interaction can significantly improve clinical understanding of resin composites. Several independent studies have examined the mechanical and physico-mechanical properties of dental resin composites; however, no comprehensive study has examined the influence of fillers and resin materials on the physico-mechanical properties of both self-cure and dual-cure composites. This study performed investigations on the physico-mechanical behaviour of four commercially available dual-cure dental composites (Bioactive, Fill Up!, Surefil One, Cention N) and two commercially available self-cure dental composites (Stela Capsule and Stela Automix). Test specimens for flexural and compressive strength, microhardness, fracture toughness, and hydrolytic behaviour were prepared and tested as per respective standards. The data sets were statistically analysed using one-way ANOVA and Tukey's post-hoc comparison. There was a substantial variation in flexural strength and modulus values in this study, ranging from 32.0 to 113.4 MPa and 2.36 to 12.07 GPa, respectively. Similarly, there were significant differences in compressive strength between the materials in this study, ranging from 119.3 to 223.5 MPa. The highest fracture toughness value was found to be 1.41 MPa.m0.5, while the lowest value was 0.43 MPa.m0.5. Variations in surface microhardness were significant (24.11-68.0 N/mm2), which correlated with the filler content. Water sorption and solubility demonstrated high variations among materials, with Surefil One exceeding ISO 4049 thresholds significantly. A linear correlation can be established between surface microhardness (HV) and flexural and compressive moduli, as well as filler content (wt.%). However, both flexural and compressive strengths are impacted by the resin's constituent monomers and the resin-filler matrix's cross-linking capability. Additionally, factors such as filler size, shape, and the cross-linking ability of the resin-filler matrix play a crucial role in fracture toughness and the propagation of cracks within the restoration. Also, resin monomers and filler particle size affect the hydrolytic degradation characteristics of composites, which can also affect their mechanical properties. © 2023 Australian Dental Association.

Production and Characterization of Andong Bamboo (Gigantochloa pseudoarundinacea (Steudel) Widjaja) Pellets from Various Stem Parts

Bamboo is an abundant biomaterial having important potential as a resource for bioenergy development. In this study, the potential of andong (Gigantochloa pseudoarundinacea (Steudel) Widjaja) bamboo for pellet production was evaluated. Some properties of bamboo pellets as density, moisture content, moisture adsorption, compressive strength, and heating value were analysed. The results indicated that bamboo is highly prospective to be explored for fuel pellets commercially. All characteristics of pellet made of bamboo fulfilled the requisites of the commercial pellets. The heating value of the pellets achieved the minimum standard for commercial pellets along with SNI 8675:2018 (&gt;17,5 MJ/kg). The effects of culm parts on the moisture content, density, moisture adsorption were not significant. There were significant differences in compressive strength and heating value between bamboo pellets produced from different culm parts. This research showed potential of andong bamboo pellet for bioenergy resource. Keywords: Andong (Gigantochloa pseudoarundinacea), Biopellet, Mechanical Properties, Physical Properties

Effects of a mineralization-promoting peptide on the physical and chemical properties of mineral trioxide aggregate

Mineral trioxide aggregate (MTA) has been used widely in dentistry due to its sealing ability and biocompatibility. Delayed setting time is one of the major limitations of MTA. Various additives have been studied to further improve the properties of MTA with varied degrees of success. In this study, we have investigated the effect of a calcium phosphate mineralization promoting-peptide (MPP3) on the physical and chemical properties of MTA in comparison with Na2HPO4. Based on the reported effects of MPP3 on calcium-phosphate mineralization reaction, our hypothesis was that MPP3 may also show beneficial effects on the calcium-silicate mineralization system of MTA. Na2HPO4 was used for comparison since its setting accelerant effect on MTA has been well documented. The cements were prepared by mixing with distilled water, 0.40 mM MPP3 solution, 15% Na2HPO4 solution, and a combination of MPP3 and Na2HPO4 solution. Initial and final setting times were measured via Vicat needle. Microhardness values were measured via Vickers indenter at 1,3,7, and 28 days after hydration. Compressive strength after setting was measured via universal testing machine. Morphological and compositional analyses were performed via FESEM imaging, XRD and Raman spectroscopy. The microhardness data was evaluated via repeated-measures ANOVA. Setting time and compressive strength data were evasluated via one-way ANOVA. Initial setting time was reduced to ∼3 min in the Na2HPO4 containing groups but remained at ∼5 min in the control and MPP3 groups. Final setting times were significantly reduced in all groups compared to the control group. The reduction in the final setting times in the Na2HPO4 containing groups were significantly higher compared to the MPP3 group. Microhardness was significantly higher in the MPP3 group at all time points. No statistically significant difference in compressive strength was observed among the groups. FESEM analysis showed presence of ettringite crystals in the MPP3 group, and NaBiO3 crystals in the Na2HPO4 containing groups. XRD analysis showed a broadening of peaks at 2θ = 32° in the Na2HPO4 containing groups, possibly due to presence of NaBiO3. Raman spectroscopy showed statistically higher ettringite content in the MPP3 containing groups. Our findings indicate that MPP3 is a beneficial additive to eliminate some of the drawbacks associated with MTA with no detrimental effects on mechanical properties and without resulting in phases that potentially cause discoloration, such as NaBiO3. We propose that the reduced final setting time and increased microhardness by MPP3 may be associated with the increased ettringite content. Future studies, where wider range of MPP3 concentrations are studied may help elucidate and optimize the beneficial effects of MPP3 observed in this study.

Physicochemical Properties and Inductive Effect of Calcium Strontium Silicate on the Differentiation of Human Dental Pulp Stem Cells for Vital Pulp Therapies: An In Vitro Study.

The development of biomaterials that exhibit profound bioactivity and stimulate stem cell differentiation is imperative for the success and prognosis of vital pulp therapies. The objectives were to (1) synthesize calcium strontium silicate (CSR) ceramic through the sol–gel process (2) investigate its physicochemical properties, bioactivity, cytocompatibility, and its stimulatory effect on the differentiation of human dental pulp stem cells (HDPSC). Calcium silicate (CS) and calcium strontium silicate (CSR) were synthesized by the sol–gel method and characterized by x-ray diffraction (XRD). Setting time, compressive strength, and pH were measured. The in vitro apatite formation was evaluated by SEM-EDX and FTIR. The NIH/3T3 cell viability was assessed using an MTT assay. The differentiation of HDPSC was evaluated using alkaline phosphatase activity (ALP), and Alizarin red staining (ARS). Ion release of Ca, Sr, and Si was measured using inductive coupled plasma optical emission spectroscopy (ICP-OES). XRD showed the synthesis of (CaSrSiO4). The initial and final setting times were significantly shorter in CSR (5 ± 0.75 min, 29 ± 1.9 min) than in CS (8 ± 0.77 min, 31 ± 1.39 min), respectively (p < 0.05). No significant difference in compressive strength was found between CS and CSR (p > 0.05). CSR demonstrated higher apatite formation and cell viability than CS. The ALP activity was significantly higher in CSR 1.16 ± 0.12 than CS 0.92 ± 0.15 after 14 d of culture (p < 0.05). ARS showed higher mineralization in CSR than CS after 14 and 21 d culture times. CSR revealed enhanced differentiation of HDPSC, physicochemical properties, and bioactivity compared to CS.

The Sarmatian Carbonate Tempestites from Kaliakra Cape (NE Bulgaria) – a Real Risk to Its Stability

This study presents the results of 227 tested specimens of the Sarmatian age taken from the rock complexes that build Kaliakra Cape: these are carbonate tempestites, as well as the limestones from the Karvuna Formation lying above them. Sedimentological and geotechnical tests have been performed. The micropetrographic analysis of the carbonate tempestites is also presented, including slightly consolidated conglomerates and hard limestones between them. It was found that the matrix of conglomerates is composed mainly of micritic peloids. Their size is about and below 0.2 mm. No cement is found, which is why the porosity is significant. Peloidal limestone has low values of bulk density -- an average value of 1.95 g/cm3. There is a significant difference in compressive strength and velocity of seismic waves obtained in both directions -- crosswise and parallel to the layering. Studies of collapses in the caves in the area show that they occur in friable peloidal limestones, and the disturbances follow the formation. This is also confirmed by the laboratory tests of samples showing lower strength indicators, namely in the direction of the layering. The data thus obtained provide valuable information on the geotechnical parameters of the main varieties in which the rock deformations are developed, which can be used in the analysis of slope stability.

An Investigation of Partial Replacement of Fine Aggregate with Recycled Plastic Supported by Silica Fume and Its Effect on Compressive Strength and Weight

Concrete is one of the main construction materials used in the building industry where it is projected that the revenue of manufacture of ready-mix concrete will amount to approximately 37.5 million dollars by 2022 in the local sector. In addition, plastic waste is another important contributor to the waste pollution since locally only 7% of such waste is recycled. This study is based on the partial replacement of aggregate by means of recycled polycarbonate plastic bottles while attaining the required structural compressive strength. Dolomite, which is an imported aggregate, and silica fume, which is a cementitious material, were used to attain a more appropriate concrete mixture.A total of six concrete mixtures were designed for the purpose of the research by varying the proportion of polycarbonate and fine aggregate. A uni-axial compressive strength test was performed after 7 and 28 days from the cube casting where a maximum of 63.2N/mm2 was attained with a control mixture made of dolomite as the coarse aggregate. Results also showed that the compressive strength decreased with the addition of plastic as a partial replacement of fine aggregate.Statistical analysis by means of an independent sample T-test showed that no significant difference in compressive strength was present between the silica fume mixture and the 5% fine aggregate replacement mixture. The results also showed that compared with the control mixture, the silica fume mixture was significantly weaker at 7 days, but no significant difference resulted at 28 days. Considering the results attained, one may easily note that there was a significant relationship between the percentage of plastic and the compressive strength. A regression analysis was used to observe such a relationship. Moreover, the result showed that a replacement percentage of 48% results in a suitable compressive strength of 10.19N/mm2, where such concrete can be utilised for non-structural purposes.From the results obtained, it was also observed that the final mass of the concrete blocks decreased as the plastic percentage increased. In relation, by maintaining a constant volume between all the samples, the hardened density of the samples also decreased with the increase in plastic percentage.

Mechanical properties of resin composites containing bioactive glass and experimental nano zinc-silica complex

Aim: Secondary caries is an important problem in dental composite restoration, and nanoparticles are commonly added to the structures of resin composites to improve their antimicrobial properties. The aim of this study is to evaluate the mechanical properties of composite materials containing bioactive glass (BAG) and an experimental nano zinc-silica (NZS) complex.&#x0D; Methodology: An experimental resin composite containing 70 wt% filler was produced and used as a control sample. This experimental resin composite was then modified by adding different amounts of BAG (10%), NZS (10%), and both BAG and NZS (10% + 10%). NZS was synthesized in situ by milling zinc and silica to nanoscale level. Compressive strength and flexural strength were investigated using a universal testing machine. Data were analyzed using one-way ANOVA and the Tukey post-hoc test.&#x0D; Results: There were no statistically significant differences in compressive strength caused by the filler amount, but statistically significant changes were found in flexural strength. Although the addition of antimicrobial agents to resin composites reduces their physical properties, this is not a clinically unacceptable limit.&#x0D; Conclusion: NZS exhibits better mechanical properties than does BAG, but both materials can be used safely in restorative materials.&#x0D; &#x0D; How to cite this article: Tunçdemir MT, Demirel MG. Mechanical properties of resin composites containing bioactive glass and experimental nano zinc-silica complex. Int Dent Res 2021;11(Suppl.1):137-42. https://doi.org/10.5577/intdentres.2021.vol11.suppl1.21&#x0D; &#x0D; Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.&#x0D;

Inverse 3D Printing with Variations of the Strand Width of the Resulting Scaffolds for Bone Replacement.

The objective of this study was to vary the wall thicknesses and pore sizes of inversely printed 3D molded bodies. Wall thicknesses were varied from 1500 to 2000 to 2500 µm. The pores had sizes of 500, 750 and 1000 µm. The sacrificial structures were fabricated from polylactide (PLA) using fused deposition modeling (FDM). To obtain the final bioceramic scaffolds, a water-based slurry was filled into the PLA molds. The PLA sacrificial molds were burned out at approximately 450 °C for 4 h. Subsequently, the samples were sintered at 1250 °C for at least 4 h. The scaffolds were mechanically characterized (native and after incubation in simulated body fluid (SBF) for 28 days). In addition, the biocompatibility was assessed by live/dead staining. The scaffolds with a strand spacing of 500 µm showed the highest compressive strength; there was no significant difference in compressive strength regardless of pore size. The specimens with 1000 µm pore size showed a significant dependence on strand width. Thus, the specimens (1000 µm pores) with 2500 µm wall thickness showed the highest compressive strength of 5.97 + 0.89 MPa. While the 1000(1500) showed a value of 2.90 + 0.67 MPa and the 1000(2000) of 3.49 + 1.16 MPa. As expected for beta-Tricalciumphosphate (β-TCP), very good biocompatibility was observed with increasing cell numbers over the experimental period.

On the production of novel zirconia-reinforced bioactive glass porous structures for bone repair

The objective of this study was to develop a replica method for producing zirconia-reinforced bioactive glass (ZRBG) porous structures for bone repair. Four different types of porous structures were produced: zirconia (G1), 58S BG-coated zirconia (G2), zirconia-reinforced BG (G3) and 58S BG-coated zirconia-reinforced BG (G4). A complete characterization of the specimens was performed via SEM-EDS, Archimedes method, 3D X-ray micro-tomography, micro-indentation, compressive strength tests and SBF immersion tests. G3 and G4 specimens presented a BG matrix (~ 33% glassy phase) with dispersed zirconia particles. The porosity of the specimens ranged from 86% up to 93%. BG58S-zirconia groups G3 and G4) exhibited lower YM (38.76 ± 11.20 GPa and 43.49 ± 2.16 GPa) than that of G1 monolithic zirconia specimens (94.39 ± 12.62 GPa), which were more compatible to that of the bone. No significant difference in compressive strength between BG58S-zirconia (G3: 0.41 ± 0.20 MPa; G4: 0.45 ± 0.11 MPa) and zirconia (G1: 0.32 ± 0.11 MPa) was detected observed (p > 0.05). In vitro SBF tests showed a potential bioactivity for ZRBG porous structures.

Mix design challenges of porous concrete pavements modified with mineral admixtures

Pervious concrete has been gaining importance in pavement constructions and low volume road applications. It has applications in parking lots, footpaths and can be used with other materials to prevent erosion. The main problem of porous concrete pavement is its strength. This mainly depends on its pore structure, cement matrix, aggregate gradation, cement content, admixtures and water/cement ratio. The research aims at determining the compressive strength and permeability of pervious concrete with W/C of 0.34.Variations in aggregate sizes is considered and admixtures like fly ash, micro silica, nano silica and superplasticizer are used. The test results show significant difference in compressive strength with variations in admixtures addition. The results were in good agreement in the case of mixtures with W/C of 0.34 and 3% nano silica with respect to compress ive strengths and permeability.

Effect of Porosity on Compressive Strength of Resin Modified Glass Ionomer Luting Cements

Introduction: The purpose of this study was to decide on the relation between types of mixing and the porosity of diameter (1-100) µm and compressive strength of RMGIC. Methods: Fifteen specimens 6mm height and 4mm in diameter were prepared for each type of luting cement and were stored in distilled water at 37° C for 24 hours. The compressive strength was determined. The fractured surfaces of 10 randomly selected specimens of each cement type were analyzed using SEM at 250 times magnification, and five photomicrographs were taken at five random places. All the photomicrographs were analyzed using image analyzer software to determine the amount and size of porosity present. Results: There was no significant difference in compressive strength between different mixing methods, but it had a significant impact by increasing the percentage of porosity of diameter (1-100) µm in diameter of RMGIC. There was no linear relationship between compressive strength and porosity (1-100) µm in diameter for both types of luting cements (P&gt;0.05). Conclusion: No significant differences in compressive strength were found using different mixing methods. The size and number of porosity in the specimens of encapsulated cements were greater than those of hand-mixed cements. The porosity (1-100) µm in diameter and the compressive strength bore no linear relationship to each other.

Optimum intensity of compaction in drained state consolidation of clay beams

Unavailability of aggregates, in plains of Pakistan, has compelled to find alternative economical materials of building construction. Efforts are being made to introduce Reinforced Baked Clay (RBC) panels of beams as a substitute for Reinforced Cement Concrete (RCC) to build low cost houses. However, shrinkage and reduced compressive strength of baked clay beams is an obstacle. This paper presents optimum compactive pressure to be applied to clay beams during casting to reduce shrinkage and to achieve maximum possible compressive strength. For this purpose, clay beams were cast and compacted at 0 to 7 MPa in drained state. Shrinkage of beams and compressive strength of cubes was determined. The results show that (i) shrinkage of clay beams reduced from 8 to 1.25 % at compactive pressure of 2 MPa, and 6 MPa, respectively, and (ii) the compressive strength of both the unbaked and baked clay increased by increasing compactive pressure on clay beams during casting. However, there was no significant difference in compressive strength of clay beams when compressed at pressure from 6 to 7 MPa. The compressive strength of baked clay obtained at optimum compactive pressure of 6 MPa was 35 MPa, which is about 1.7 times higher than that of M20 grade concrete.

On the Relation of Amorphous Calcium Carbonate and the Macromechanical Properties of Sea Urchin Spines

Amorphous calcium carbonate (ACC) plays a crucial role in the formation of biogenic carbonates. It is widely accepted that ACC and organic macromolecules alter the fracture properties of Echinoderm calcite from the well‐defined cleavage planes of the raw material to conchoidal. However, the influence of ACC on the outstanding macromechanical properties of Echinoderm calcite is unknown. To address this question, full‐grown spines of the slate pencil urchin are shortly heated to 250 °C. Differential scanning calorimetry indicates that all ACC is crystallized at this temperature. Heated spines are compared with an untreated control group and no significant differences in compressive strength, bending strength, damage tolerance, and Young's modulus are detected. This highlights the weak influence of ≈6 wt% ACC on the macromechanical properties of Echinoderm calcite, which are likely established by its intricate and damage tolerant microstructure. When heating Echinoderm calcite, organics decompose, Mg calcite transforms, water is lost, and cracks and micropores form. All these processes are analyzed to exclude their influence on the mechanical properties, and it is imperative to consider them all. Only this way meaningful results can be achieved as these processes are temperature and dwelling time dependent and may even occur below 250 °C.

Collagen and bone morphogenetic protein-2 functionalized hydroxyapatite scaffolds induce osteogenic differentiation in human adipose-derived stem cells.

Surface modification is one important way to fabricate successful biocompatible materials in bone tissue engineering. Hydroxyapatite (HAp) materials have received considerable attention as suitable bioceramics for manufacturing osseous implants because of their similarity to bone mineral in terms of chemical composition. In this study, the surface of porous HAp scaffold was modified by collagen treatment and bone morphogenetic protein-2 (BMP-2) conjugation. The surface modification did not affect the HAp scaffold's bulk properties. No significant difference in compressive strength was found among different scaffolds, with HAp, collagen modified HAp, and collagen-BMP-2-functionalized HAp having compressive strengths of 45.8 ± 3.12, 51.2 ± 4.09, and 50.7 ± 3.98 MPa, respectively. In vitro studies were performed to compare adhesion and osteogenic differentiation between human adipose-derived stem cells (hADSCs) with modified surfaces and those unmodified HAp surfaces. Collagen or BMP-2 alone was insufficient and that both collagen and BMP-2 are necessary to get the desired results. The findings suggest the possibility of using three-dimensional HAp scaffold treated with gold-standard collagen coating and highly researched BMP-2 growth factor as a platform to deliver hADSCs. Results of this study could be used to develop treatment strategy for regenerating completely transected models using more synergistic approaches.

Mechanical Properties of High Viscosity Glass Ionomer and Glass Hybrid Restorative Materials.

Objectivesto determine the mechanical properties of hybrid and high-viscosity glass ionomer cements. Compressive strength and hardness of three glass ionomer cements (GIC) were measured: Ketac ™ Universal Aplicap ™, EQUIA Fil® and EQUIA FORTE Fil®, and the SEM sample analysis were performed.Materials and MethodsThe samples for measuring the compressive strength were prepared using silicone molds with standard dimensions of 6 mm x 4 mm and stored in deionized water for five days, while the samples for hardness measurement were prepared using Teflon molds with a cylindrical opening in the middle, dimensions 2 mm in height and 5 mm in width. For each material, one sample was made (n = 1) and stored in deionized water at 37ºC for 25 days. A representative sample of each material was analyzed using SEM. For the comparison of obtained values, the ANOVA test was used, while Tukey test was used for the multiple comparison.ResultsThere were no significant differences between the compressive strength of the three tested materials (p <0.05). The hardness values were: 157 HV0,2 for Ketac ™ Universal Aplicap ™, 47 HV0,2 for EQUIA Fil® and 39 HV0,2 for EQUIA FORTE Fil®, respectively, and were significantly different, implying that Ketac ™ Universal Aplicap ™ has much higher hardness values than the other materials tested. SEM sample analysis revealed similar fracture modes of the tested materials.ConclusionIt was concluded that there were no statistically significant differences in compressive strength and fracture modes between the tested materials, while Ketac ™ Universal Aplicap ™ hardness results were significantly higher than the ones measured for EQUIA Fil® and EQUIA FORTE Fil®.

Chemical and biological properties of new sealant-use cement materials

ObjectivesThe aim of this study was to investigate the chemical and biological properties of newly developed bioactive cements, modified such that they are largely composed of calcium, phosphate and fluoride. We investigated whether newly developed bioactive cements have the potential to further protect surrounding hard tissue and enhance remineralization of demineralized tissue by additional ion release. MethodsWe developed four types of novel GIC based on Fuji VII, modified with phosphate and fluoride and calcium. Compressive strength tests were performed following JIS T6607 methods. Ion release of calcium, phosphate and fluoride after 24 h storage were determined using atomic absorption spectroscopy, colorimetry and an ion-specific electrode. Fluoride releases and recharge were measured at 1, 3, 6, 12, 24 and 168 h. Viability was determined by colony-forming units. Inhibitions of biofilm formation and cell proliferation activity were measured. ResultsThe GIC groups showed no significant differences in compressive strength after 1 and 7 days. The rates of fluoride ion release from newly developed GICs were significantly greater than those of Fuji VII, Fuji III and BS. All materials except TM can be recharged with fluoride ions. Compared with the control group, which did not release fluoride ions, all materials showed significantly stronger antibacterial effects. The newly developed GICs and BS showed less biofilm formation than Fuji VII and Fuji III. SignificanceThree of four newly developed GICs modified with calcium, phosphate and fluoride ions were found to be superior to other sealant materials.