Resin Composite Materials Research Articles

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

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

Exfoliation of boron nitride nanosheets by liquid phase method based on deep eutectic solvents and their thermal management application

AbstractBoron nitride had emerged as an innovative thermally conductive filler, garnering increasing attention from researchers. However, there was a need to create new methods for efficiently producing functionalized boron nitride nanosheets with enhanced thermal conductivity and dispersion. In this study, a novel approach was introduced to utilize deep eutectic solvents as additives to facilitate the exfoliation of boron nitride nanosheets. This method offered significant advantages in terms of cost‐effectiveness (low additives level) and high yield (about 60%). Furthermore, the resulting epoxy resin composite material exhibited outstanding thermal conductivity and thermal management properties. The thermal conductivity of EP/d‐BNNS composites reached 1.02 W/mK at 20 wt% d‐BNNS loading. Additionally, the composite material demonstrated good thermal stability and low dielectric properties. This work demonstrated that this proposed approach represents an effective means for the scalable production of boron nitride nanosheets.Highlights The boron nitride nanosheets were obtained by deep eutectic solvents (DES) ball milling method. The exfoliated boron nitride exhibits superior dispersion stability. The thermal conductivity of EP composites is significantly improved.

Chromatic Adaption of Two Universal Composites: Spectrophotometric Analysis

Objective: The purpose of this study was to evaluate the chromatic adaptability and color stability of two different composite resins, Omnichroma and Estelite Bulk-Fill Flow, in Class V restorations at different times. Materials and methods: Standardized Class V cavities were prepared on the labial surface of 34 extracted intact and noncarious human permanent molars. The dental elements were randomly divided into two groups according to the resin composite material. Group 1 was restored with Omnichroma (Tokuyama Dental Corporation Inc., Tokyo, Japan) and Group 2 was restored with Estelite BulkFill Flow Universal (Tokuyama Dental Corporation Inc., Tokyo, Japan). Color properties were assessed using a spectrophotometer, SpectroShadeTM Micro (MHT Optic Research, Niederhasli, Switzerland), at baseline (T0), immediately after Class V restoration (T1), 24 h after restoration (T2) and after thermocycling (T3) (ISO/TS 11405, 2015 protocol). Color difference (ΔE) was analyzed with a Student’s t-test and a Wilcoxon–Mann–Whitney test to evaluate the differences, in terms of chromatic adaptability, between the two materials (inter-group analysis) while Kruskal–Wallis test e Two-way ANOVA statistical tests were used to evaluate the color stability of each material over time (intra-group analysis). Results: Regarding the inter-group analysis, there were no statistically significant differences between the two materials in all the comparisons: T0–T1 (p = 0.9025), T0–T2 (p = 0.2779), T0–T3 (p = 0.4694). Moreover, both groups showed an average ΔE > 2. In the intra-group analysis, no statistically significant differences were observed in either Group 1 (p = 0.954) or Group 2 (p = 0.8654). Conclusions: The in vitro color matching, assessed by spectrophotometry, of the two tested resin composites does not vary at different time intervals. Furthermore, even though both composites use different mechanisms to produce the color the human eye perceives, they show very similar chromatic adaptability.

Is It Possible for Single-shade Composites to Mimic the Color, Lightness, Chroma, and Hue of Other Single-shade Composites? An In Vitro Study.

This study aimed to assess color matching post-repair using the same or different single-shade composites of three distinct composite resin materials (Omnichroma-OM, ZenChroma-ZC, and Charisma Topaz One-CTO) following aging in coffee solution and distilled water. Evaluation focused on color change parameters (ΔE00, ΔL00, ΔC00, and ΔH00). Specimens were prepared in disk shape with a diameter of 8 mm and a height of 2 mm (n=180). Half of each composite group was immersed in distilled water, while the other half was immersed in coffee solution for 12 days each (n=90). After aging, cylindrical cavities with a diameter of 4 mm and a depth of 1 mm were prepared at the center of the specimens. The cavities were repaired with both themselves and other composite resins (n=10). Color measurements of the specimens were performed using VITA Easyshade 5 (VITA Zahnfabrik, Bad Säckingen, Germany) at the following time points: baseline (T0), after aging (12 days) (T1), immediately after repair (T2), one day after repair (T3), one week after repair (T4), and one month after repair (T5). Statistically significant differences were found in the mean ΔE00 measurements among the study groups at all time points for each of the three composite resins (p<0.05). Similarly, statistically significant differences were found in the mean ΔE00 measurements over time for each of the three composite resins in each study group (p<0.05). The baseline measurements of materials repaired with themselves in the distilled water groups and the final measurements of materials repaired with themselves in the coffee groups were found to be within acceptable ΔE00limits. At the end of the study, only CTO repaired with OM showed acceptable color matching with different composites in both coffee and distilled water groups. Acceptable color matching was achieved when using the same material for repair in specimens aged in distilled water and coffee. However, variations in matching were observed when different materials were used for repair, indicating the need for ongoing monitoring. Contributions of ΔL00, ΔC00, and ΔH00 values to color differences vary depending on the resins and repair process and change over time.

Evaluation of Color and Translucency Changes of PEEK Material Veneered with Single-Shade Composite Resins

Aim: The aim of this study was to evaluate the color and translucency changes of single-shade composites used in veneering polyetheretherketone (PEEK) material after aging. Materials and Methods: 3 single-shade composites with different chemical structures and 1 conventional composite resin were applied on the PEEK material with a thickness of 2 mm (N=40, n=10). L, a, and b color coordinates of each specimen were measured three times with a spectrophotometer on a black, gray, and white background from the center of the specimen, and the average of these measurements was recorded. The specimens were subjected to 5000 cycles of thermal aging at 5-55°C. After aging, color measurements were repeated. Color changes (ΔE00) and translucency parameters (ΔTP00) of composite resin specimens were determined before and after aging using CIEDE 2000 color formulas. The data obtained were analyzed by one-way analysis of variance and Tukey HSD test (p&lt;0.05). Results: As a result of the study, the color change of all composite resin materials was found to be below the clinically acceptable limit (ΔE = 1.8). The lowest color change was observed in the traditional composite group, and a statistically significant difference was found between the other groups (p&lt;0.05). The translucency change of single-shade composite materials was found to be statistically lower than that of conventional composite resin (p&lt;0.05). Conclusion: This study's results show that single-shade composite resins can be used as an optical alternative to traditional composites in direct veneering of the PEEK material.

Impact of refrigeration of different Resin composite restorative materials on the marginal adaptation in class II restorations

BackgroundThe pre-polymerization temperature of resin composite restorative materials could influence their adaptation to cavity details. As a current debate is existing about the refrigeration of resin composite restorative materials, this study was designed to assess the effect of refrigeration of 3 types of resin composite restorative materials with different matrix systems on their marginal adaptation in Class II restorations.MethodsForty-two sound maxillary molars, each with two separated Class II cavities, were used in this study. The teeth were assigned into 3 main groups (n = 14) according to the restorative /adhesive system used; an Ormocer-based composite (Admira Fusion/Futurabond M+, Voco GmbH, Cuxhaven, Germany), a methacrylate modified Ormocer-based (Ceram.X SphereTEC One/Prime&Bond Universal, Dentsply Sirona GmbH Konstanz, Germany), and a methacrylate-based (Tetric N-Ceram/Tetric N-Bond Universal, Ivoclar Vivadent AG, Schaan, Liechtenstein). Each group was then divided into 2 subgroups (n = 14) according to the gingival margin location; 1 mm above and 1 mm below the cemento-enamel junction (C.E.J). Each subgroup was further divided into 2 categories (n = 7) according to the storage temperature; stored at room temperature or stored in refrigerator at 4°- 5° C. Epoxy resin replicas were observed under scanning electron microscope (SEM) to examine the marginal gaps. A gab scoring system was used to assess the marginal adaptation of each restoration by giving scores on the basis of measurements of the maximum marginal gaps. The data obtained were statistically analyzed using the Chi-square test at a significance level of p < 0.05.ResultsNone of the tested groups exhibited 100% gap-free margins irrespective of margin location or storage temperature. For both storage temperatures, no statistically significant difference was observed among all tested groups either with margins located above or below C.E.J (p > 0.05). As well, there was no statistically significant difference when comparing both marginal locations for each material (p > 0.05). Regarding the effect of storage temperature, statistically significant difference was only observed between the room-temperature stored groups with margins located above C.E.J and their corresponding groups stored in refrigerator (p < 0.05).ConclusionThe refrigeration of resin composite restorative materials prior to the restorative procedures revealed a deleterious effect on marginal adaptation of the restorations with margins located in enamel regardless the type of material used.

Influence of different composite curing agents on the rapid curing characteristics and mechanical performance of epoxy resins

To address the need for rapid in situ plugging and repair of hydraulic machinery and chemical pipelines and to resolve the issue that a single curing agent cannot simultaneously achieve rapid curing and excellent mechanical properties in epoxy resin systems, this study explores the use of composite curing agents. In particular, effective formulations are designed for mixing fast and slow curing agents, studying their effects on the curing behavior, curing quality, and mechanical properties of epoxy resins and elucidating their influence mechanisms. The results indicate that three resin systems meet the requirements for rapid curing (curing time within 30 min): 4A6B/EP, 2A8B/EP, and 0A10B/EP. Among them, 4A6B/EP exhibits the best curing quality and mechanical properties. In particular, 4A6B/EP demonstrates the lowest values of curing shrinkage rate, internal curing stress, average pore size, porosity, and cumulative pore volume. Its low internal stress and low defects reduce the stress concentration, while more efficient deflection and branching of internal cracks enhance its deformation resistance. Consequently, 4A6B/EP shows the highest microhardness, fracture toughness, tensile strength, Young’s modulus, and elongation after fracture. Based on the comprehensive evaluation of rapid curing characteristics and mechanical properties, the 4A6B/EP system offers the best overall performance. Therefore, it is recommended as the preferred resin system for rapid plugging and repair of composite materials, providing a theoretical basis and technical support for boosting the application of epoxy resin composite materials in high-tech fields.

Influence of dental bleaching on the microhardness and flexural strength of resin composites

Purpose. This study aimed to examine the influence of dental bleaching systems (home bleaching system and two in-office bleaching systems) on the surface microhardness, and flexural strength of the two resin composite restorative materials (Beautifil II and OliREVO). Methods. For each test, a total of 48 samples were prepared with both types of composites. The samples of each type of composite were divided at random into four groups each of six samples, control group (C) was not bleached and kept in distilled water, other three groups (G1, G2, and G3) were bleached with 10% hydrogen peroxide (HP) home beaching, 35% and 40% HP in-office bleaching systems, respectively. To measure the composite resin's microhardness, a Vickers microhardness tester was used, while a universal testing machine was used to measure its flexural strength. Results. For statistical analysis, Duncan and ANOVA tests were used. A p-value ≤0.01 indicates statistically significant results. In-office bleaching systems (35% and 40% HP) significantly reduced microhardness and flexural strength of the used resin composites. Generally, the hardness and flexural strength of Beautifil II were better than OliREVO composite. Conclusion. Regarding the physical properties of composite resins, the microhardness and flexural strength may be compromised by bleaching treatments.

THE EFFECT OF DIFFERENT STAINING SOLUTIONS ON THE COLOR STABILITY OF PERMANENT INDIRECT COMPOSITE RESINS PRODUCED BY ADDITIVE AND SUBTRACTIVE TECHNIQUES

Objective: To investigate the effects of various beverages on the color stability of permanent composite resins produced by additive (AM) or subtractive manufacturing (SM) techniques comparatively. Materials and Methods: Six composite resin materials produced by SM (Vita Enamic-VE, Cerasmart-CE, Lava Ultimate-LU) and AM (Varseo Smile Crown plus-VSC, Saremco print Crowntech-SPC, Formlabs 3B Permanent Crown-FPC) techniques were selected and soaked in different solutions (artificial saliva, black tea, coffee) for different times (0, 1 and 7 days). L*, a*, b* values of the samples were recorded using a spectrophotometer. The color changes of the samples were determined using the CIELAB formula. In determining the color differences between the test materials, Kruskal-Wallis analysis was used when one-way analysis of variance wasn’t available. Results: Group VE was the least stained group on the 1st and 7th day of artificial saliva solution and the 7th day of coffee solution, while Group CE was the least stained group on the 1st day of coffee solution. In the tea solution, on the 1st and 7th days, there wasn’t difference in the materials' color change (p&amp;gt;0.05). Tea and coffee solutions caused statistically significantly more color change in all test materials than artificial saliva (except Group CE on the 7th day, Group VSC and FPC on the 1st day) (p&amp;lt;0.05). Conclusion: 3D permanent composite resins generally showed more staining than CAD/CAM milled composite resins. Tea and coffee staining solutions changed the color of the materials compared to artificial saliva. As the storage time increased, more color changes were observed.

Thermomechanical Properties of Ramie Fiber/Degradable Epoxy Resin Composites and Their Performance on Cylinder Inner Lining.

Type IV gas cylinders are widely used in the field of vehicles due to their advantages such as light weight, cleanliness, and low cost. Ramie fiber/degradable epoxy resin composites (RFRDE) provide new ideas for the material selection of Type IV gas cylinders due to their advantages of low carbon emissions, low environmental pollution, and renewable resource utilization. However, the poor interfacial bonding strength and moisture resistance between polyethylene plastics and RFRDE have limited their application areas. This study tested the mechanical properties of ramie fibers at different heat treatment temperatures, and studied the thermal mechanical properties of RFRDE through differential scanning calorimeter and curing kinetics methods. At 180 °C, the tensile strength of fiber bundles decreased by 34% compared to untreated fibers. As the highest curing temperature decreases, the tensile strength of RFRDE increases but the curing degree decreases. At the highest curing temperature of 100 °C, the tensile strength of RFRDE is 296 MPa. The effect of the corona discharge and flexible adhesive on the surface modification of polyethylene was analyzed using scanning electron microscopy. These results provide guidance for the development of natural fiber/degradable epoxy resin composite materials.

Long-term success of inlay and onlay procedures in dental repairs

Inlays and onlays are vital restorative techniques in dentistry, offering a conservative alternative to full crowns while preserving more of the natural tooth structure. These restorations, typically made from ceramic or composite resin materials, provide both aesthetic and functional benefits and are increasingly favored for their durability and longevity. In contrast to direct restorations, inlays and onlays are fabricated outside the mouth, allowing for greater precision and a more customized fit. The clinical success of these restorations largely depends on factors such as material choice, bonding technique, and patient-related variables like oral hygiene and habits. Ceramic materials are particularly noted for their resistance to wear and their ability to closely mimic the natural appearance of teeth, making them an attractive option for both patients and clinicians. Composite resins, while slightly less durable, offer a cost-effective alternative with satisfactory long-term results. Proper bonding techniques and high-quality materials are essential for ensuring the durability of inlays and onlays, with many restorations lasting over a decade. Patient-related factors also play a significant role in the success of inlays and onlays. Effective oral hygiene, regular dental check-ups, and the avoidance of habits like bruxism are essential for maintaining the integrity of these restorations over time. Despite the challenges and technical demands associated with their placement, inlays and onlays are highly successful when properly executed, offering patients a durable, aesthetically pleasing solution for dental repairs. The discussion of this review focuses on the critical elements that influence the long-term success of inlays and onlays, including material selection, clinical technique, and patient management, highlighting their effectiveness as a restorative option in modern dentistry.

Comparison of Water Sorption and Water Solubility Properties of Current Restorative Materials with Different Contents.

This study aimed to investigate and compare water sorption and solubility properties of current restorative materials with different contents. Alkasite, self-adhesive restorative material (Cention N, Ivoclar Vivadent AG, Schaan, Liechtenstein), bulk-fill glass hybrid restorative material (EQUIA Forte HT, GC Corp., Tokyo, Japan), nanohybrid universal composite material (OptiShade, Kerr Dental, United States), and bulk-fill composite material (Filtek One Bulk Fill Restorative, 3M ESPE, St. Paul, Minnesota, United States) were used. Samples (n = 6) were prepared (2 × 10 mm) according to the ISO 4049 standards. Water sorption and solubility values were calculated according to the ISO 4049 standards. One-way ANOVA, Tukey's post-hoc, Tamhane's T2 post-hoc, Pearson's correlation, and independent samples t-tests were used for statistical analysis (p < 0.05). Group EQUIA Forte HT significantly showed the highest water sorption values (57.278 ± 3.174), while Group Filtek One Bulk Fill Restorative exhibited the lowest (4.429 ± 0.174; p < 0.05). The water sorption values for Group Cention N were 5.000 ± 0.542. Group EQUIA Forte HT significantly had the lowest water solubility values (-99.799 ± 1.909), while Group Cention N (-2.966 ± 0.402) significantly exhibited the highest (p < 0.05). There was no significant correlation between water sorption and solubility values for each material (p > 0.05). The bulk-fill nano-filled composite resin material was successful in terms of water sorption while the bulk-fill glass hybrid restorative system in terms of water solubility. Alkasite can be recommended to be used as a base material due to its high solubility feature. Monomer, filler type, and amount had an impact on the water sorption and solubility properties of the tested materials.

BASE SURFACE TEMPERATURE OF BULK FILL RESIN COMPOSITE WITH DIFFERENT THICKNESS

Background: The material thickness is one factor that influences the polymerization of resin composites. Bulk fill resin composite is an efficient dental resin composite restoration material because it can be cured to a thickness of up to 4-5 mm. The thickness of the material can also affect the temperature rise, while maintaining the temperature is very important because a significant increase can damage the pulp. Purpose: This research aimed to analyze the base surface temperature of bulk fill resin composite with different thicknesses. Methods: Thirty bulk fill resin composite samples with a diameter of 5 mm were divided into three groups with different thicknesses, namely group I (3 mm), group II (4 mm), and group III (5 mm). Each group of samples was cured using an LED Light Curing Unit for 20 seconds, and carried out simultaneously with the measurement of the base surface temperature using a type-K digital thermocouple. Data analyzed using One Way ANOVA and LSD post hoc tests. Results: The mean and standard deviation of the base surface temperature of bulk fill resin composite in groups I, II, and III, respectively, is 37.56 ± 1.06oC, group II 36.89 ± 1.23oC, and group III 36.00 ± 1.2 oC. It showed significantly different between the groups (p&lt;0,05). Conclusion: The thicker the bulk fill resin composite, the lower the base surface temperature.

Investigation of Various Finishing/Polishing Procedures on Color Stability of Composite Resins

Objective: The objective of this study was to assess the impact of various finishing and polishing systems on the color stability of composite resins treated with coffee. Methods: Fifty samples of each of nanohybrid and supra-nanohybrid composite resin materials were prepared and each material was randomly divided into 5 groups (n=10): Group 1: Control group (mylar strip), Group 2: One Gloss (one step), Group 3: One Gloss + polishing paste, Group 4: Soflex disk (multistep), Group 5: Soflex disk + polishing paste. The samples were colored in coffee solution for 144 hours to simulate six months of coffee consumption after polishing. The color of the samples before-after staining was measured with a spectrophotometer and ∆E00 values were calculated. Results: Material, polishing type and the interaction of these two parameters had a statistical effect on the color change values (p&amp;lt; 0,001). The ∆E00 values of supra-nanohybrid composite resin were higher than nanohybrid. Both materials exhibited color change above the thresholds of clinical perceptibility (PT&amp;gt; 0,8) and acceptability (AT&amp;gt; 1,8). In terms of polishing types, the highest ∆E00 was found in the control group and the lowest in the disk group. The additionally applied polishing paste caused a non-significant decrease in the color change of the single-step polishing system (p&amp;lt; 0,05) and a statistically significant increase in the multi-steps polishing system (p&amp;gt; 0,05). Conclusion: Considering the limitations of the study, it can be concluded that the use of multi-steps discs is more advantageous in preventing discoloration of composite resins.

Research on new magnetic epoxy resin composite slurry materials and localization grouting diffusion mechanism

A significant number of steep cracks are frequently encountered in underground engineering, posing a threat to operation. The high-pressure grouting method is a commonly utilized repair technique. Nevertheless, conventional grout is prone to displacement due to its weight, making it challenging to ensure adequate filling of the cracks. Therefore, this study aims to develop a grouting material with targeted displacement and anchoring properties. Firstly, an optimal magnetic slurry composition was determined through an orthogonal test. Subsequently, XRD and SEM were used to analyze the impact of the magnetic field on the composition distribution, internal pore structure, and transient viscosity of the slurry. Afterwards, a model for localized grout diffusion under magnetic was established. The results show that the application of a magnetic field caused the slurry to compact due to magnetic forces, reducing its porosity. Moreover, the dynamic viscosity of the slurry increased exponentially with rising magnetic induction intensity. Notably, a 40.5% increase in the diffusion area was observed when the magnetic field intensity rose from 2500 to 4500 GS. The error between the measured and theoretical values of the magnetic slurry diffusion model was only 8.91%, indicating the model's accuracy in describing the slurry diffusion process under magnetic field influence.

To bond or not to bond: considerations for choosing the appropriate treatment for closing a midline diastema

In the realm of dental aesthetics, the decision between employing a resin composite material bonded to the dental hard tissues, or orthodontics to address a midline diastema and enhance smile aesthetics, can be complex and multifaceted. This article delves into the critical considerations and decision-making processes guiding dental practitioners through how to decide when orthodontic movement, while a more costly and complex treatment option, might provide optimum aesthetics. By exploring the aetiology of midline diastemas, and the pivotal role of the central incisor in smile aesthetics the author aims to equip clinicians with a comprehensive framework. CPD/Clinical Relevance: This article shows how to assess suitable treatment modalities for closing midline diastemas in adult patients.

Elastic Property Evaluation of Fiberglass and Epoxy Resin Composite Material Using Digital Image Correlation.

This study focused on evaluating the sensitivity and limitations of the simplified equipment used in the Digital Image Correlation (DIC) technique, comparing them with the analog extensometer, based on the mechanical property data of a composite made of fiberglass and epoxy resin. The objectives included establishing a methodology based on the literature, fabricating samples through manual lamination, conducting mechanical tests according to the ASTM D3039 and D3518 standards, comparing DIC with the analog extensometer of the testing machine, and contrasting the experimental results with classical laminate theory. Three composite plates with specific stacking sequences ([0]3, [90]4, and [±45]3) were fabricated, and samples were extracted for testing to determine tensile strength, modulus of elasticity, and other properties. DIC was used to capture deformation fields during testing. Comparisons between data obtained from the analog extensometer and DIC revealed differences of 11.1% for the longitudinal modulus of elasticity E1 and 5.6% for E2. Under low deformation conditions, DIC showed lower efficiency due to equipment limitations. Finally, a theoretical analysis based on classical laminate theory, conducted using a Python script, estimated the longitudinal modulus of elasticity Ex and the shear strength of the [±45]3 laminate, highlighting a relative difference of 31.2% between the theoretical value of 7136 MPa and the experimental value of 5208 MPa for Ex.

Hydraulic pressure resistance of the ceramic resin composite buoyancy materials based on cylindrical tube configuration

Due to high modulus, high strength and low water absorption of the 99.5% alumina ceramic, the tubular ceramic resin composite (TCRC) has been designed and fabricated, which can provide a potential option for the deep-sea buoyancy materials. The reliability and applicability of TCRC under hydrostatic pressure are systematically discussed by means of theory, experiment and simulation. Circumferential instability and strength failure are two possible failure modes of the TCRC through theoretical analysis. The study indicates that the load-bearing capacity of TCRC decreases with the increase of the number of vertical/horizontal tube arrays m, the ratio of the inner to outer radius r/Rc of the ceramic tube or the ratio of the length to the outer radius L/Rc of the ceramic tube. Conversely, the load-bearing capacity of TCRC increases with the increase in the modulus of matrix phase Er. In addition, TCRC with parameters of “r/R-0.93/0.91-3X3-L40-E3.18” has excellent performance through experimental verification. That is, the core density and hydrostatic strength of the TCRC are 0.67 g/cm3 and 150.6 MPa, respectively. Better stated, our designed buoyancy material can be applied in the deep-sea environment of 12000m, which is the deepest spot on the ocean floor ever explored. The excellent performance of TCRC verifies the feasibility of ceramic circular honeycomb configuration in the application of hydrostatic pressure environment. Meanwhile, the buoyancy materials used in different water depths can be designed by changing the L/Rc or r/Rc of the round tube in circular honeycomb.

Oil-Loaded Mesoporous Silica to Enhance the Lubrication of Polypropylene Resin Composite Materials

Polymer self-lubricating materials have advantages such as low friction coefficient, good wear resistance, and high work efficiency, giving them wide application potential in friction and wear. This work fabricated polymer-based self-lubricating materials by incorporating oil-loaded mesoporous silica nanoparticles (MSNs + YR1800) in the polypropylene resin (PP). The effects of different content of MSNs + YR1800 on the tribological and mechanical properties of the obtained self-lubricating composite materials were studied. The results indicate that the content of MSNs + YR1800 in composite materials significantly impacts their tribological properties. When the content of MSNs + YR1800 was 10 wt%, the coefficient of friction reduced to 0.09,which was 84.5% lower than for PP and 78.6% lower than for composite materials containing 5 wt% mesoporous silica nanoparticle (MSNs). Compared with pure PP, the wear rate decreases from 4.93 × 10−11 m3∙Nm−1 to 4.43 × 10−13 m3∙Nm−1, which is reduced by two orders of magnitude. The excellent tribological properties of composite materials are attributed to the high specific surface area, large pore volume, strong adsorption capacity, and high oil loading capacity of mesoporous silica nanoparticle as nanofillers. The MSNs + YR1800 release lubricants to form a lubricating oil film during the friction process under load conditions, preventing direct contact between the friction pair and the surface of the composite material. Compared with polymer-silica hybrid oil-loaded microcapsules, MSNs + YR1800 can effectively reduce lubricant leakage, prolong operation life, improve lubrication efficiency, and ensure the continuous and stable existence of lubricating oil films.

The 24 months clinical evaluation of class II bulk fill composite restorations

Background: Resin Composite materials are widely used in daily clinical dentistry because of their moderate cost compared with ceramics, easy placement, adequate esthetics, ability to bond with enamel and dentine, and physico-chemical properties. Bulkfill composite materials were introduced to reduce chairside time. These materials have properties such as optimal bond strength, decreased polymerization shrinkage, and reduced cuspal deflection. This in-vivo study compared the clinical performance of three different class II resin composite restorations. Methods: Seventy-one patients (41 females and 30 males) aged 20–43 years with at least three approximal caries were included in the present study. Two hundred twenty-three teeth with approximal caries were restored with two bulk-fill composites (Tetric-N Ceram Bulk fill [TEC], Filtek Bulk Fill [FB]) and a posterior resin composite (Gradia Direct Posterior [GDP]). Two experienced dentists clinically evaluated the restorations with a 5x magnification loupe using the modified United States Public Health Service (USPHS) criteria at baseline and at 24 months. Results: The chi-square test was performed for statistical analysis. The cumulative retention rate for all restorations at 24 months was 90.5%. Retention loss was observed for three TEC (6.1%), four FB (8.2), and seven GDP (14%) restorations. There was no statistically significant difference among the three resin composite restoration groups in color match, marginal adaptation, surface roughness, marginal discoloration, anatomical form, and secondary caries criteria (P&gt;0.05). Conclusion: Bulk-fill composite restorations in class II slot cavities have the same clinical results as traditional posterior composite restorations.