Base Composite Material Research Articles

Influence of increment thickness on dentin bond strength and light transmission of composite base materials.

Bulk-fill resin composites (BFCs) are gaining popularity in restorative dentistry due to the reduced chair time and ease of application. This study aimed to evaluate the influence of increment thickness on dentin bond strength and light transmission of different BFCs and a new discontinuous fiber-reinforced composite. One hundred eighty extracted sound human molars were prepared for a shear bond strength (SBS) test. The teeth were divided into four groups (n=45) according to the resin composite used: regular particulate filler resin composite: (1) G-ænial Anterior [GA] (control); bulk-fill resin composites: (2) Tetric EvoCeram Bulk Fill [TEBF] and (3) SDR; and discontinuous fiber-reinforced composite: (4) everX Posterior [EXP]. Each group was subdivided according to increment thickness (2, 4, and 6mm). The irradiance power through the material of all groups/subgroups was quantified (MARC® Resin Calibrator; BlueLight Analytics Inc.). Data were analyzed using two-way ANOVA followed by Tukey's post hoc test. SBS and light irradiance decreased as the increment's height increased (p<0.05), regardless of the type of resin composite used. EXP presented the highest SBS in 2- and 4-mm-thick increments when compared to other composites, although the differences were not statistically significant (p>0.05). Light irradiance mean values arranged in descending order were (p<0.05) EXP, SDR, TEBF, and GA. As increment thickness increased, the light transmission decreased for all tested resin composites. Discontinuous fiber-reinforced composite showed the highest value of curing light transmission, which was also seen in improved bonding strength to the underlying dentin surface. Discontinuous fiber-reinforced composite can be applied safely in bulks of 4-mm increments same as other bulk-fill composites, although, in 2-mm thickness, the investigated composites showed better performance.

Thermoelectric Behavior of Conducting Polymers Hybridized with Inorganic Nanoparticles

We introduce a simple and facile method for fabrication of a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/germanium nanoparticle (Ge NP) composite film with enhanced thermoelectric conversion efficiency. The Ge NP were prepared by mechanical grinding and mixed with solution-phase PEDOT:PSS. The film processability of the composite was excellent and the overall process did not involve complicated synthetic procedures. The thermoelectric power factor of the composite film was optimized to 31.20 μW m−1 K−2 by controlling the composition. The composite film had an exceptionally low thermal conductivity of 0.417 W m−1 K−1 and the thermoelectric figure of merit (ZT) was maximized at 0.0223 at room temperature. The mechanism for the improvement of the thermoelectric conversion efficiency was investigated by introducing energy models based on interfacial scattering of charge carriers and phonons. We expect that this robust method could lead to a facile route for design of organic–inorganic composite-based thermoelectric materials.

Effect of nightguard vital bleaching gel on the color stability of provisional restorative materials.

To assess the hypothesis that there was no difference in effect of 10% and 15% tooth bleaching agents on color stability of materials used for provisional fixed dental prosthesis. Fifteen samples from two materials used for provisional fixed dental prosthesis: methacrylate-based and composite-based materials and 15 preformed polycarbonate crowns soaked in bleaching gel or distilled water. Spectrophotometer recorded color of specimens at baseline, after 3, 7, and 14 days. Data were statistically analyzed using two-factor ANOVA test to compare the color stability of tested materials. Methyl-based provisional material exhibited statistically higher color change when exposed to 10% and 15% bleaching gel (delta EFNx01: 9.0 and 11.1, respectively) as compared to distilled water (delta EFNx01: 2.9). Delta EFNx01 of composite-based material specimens exposed to distilled water was statistically higher (6.3) than specimens exposed to 10% and 15% bleaching gel (1.5 and 1.1, respectively). Polycarbonate crowns showed a statistically lower color change when exposed to 15% (0.9) than to 10% bleaching gel (5.1) or distilled water (5.5). Composite-based provisional material showed highest color stability when exposed to vital tooth bleaching gel, whereas methacrylate-based material was the least color stable. Polycarbonate crowns were more color stable when exposed to 15% bleaching gel as opposed to 10% bleaching gel.

PERBANDINGAN KEBOCORAN MIKRO PADA RESTORASI RESIN KOMPOSIT MIKROFILLER DENGAN RESIN-MODIFIED GLASS IONOMER CEMENT (RMGIC) PADA KAVITAS KLAS V GIGI ANTERIOR

Microleakage defined as the clinically undetectable passage of bacteria, fluids, molecules or ions between a cavity wall and the restorative material. Microleakage tends to occur in Class V cavities. It is caused by marginal adaptation which is more difficult in class V cavities. Microfiller composite resin is developed and indicated for areas that not require a large pressure. As the development of dental materials, it has been developed a composite resin base material that is known as resin-modified glass ionomer cement. This material has purposed to reduce the limitation of conventional glass ionomer cement and take the advantage of the composite resin material.&#x0D; The aim of this study was to evaluate microleakage difference of microfiler composite resin restoration with resin-modified glass ionomer cement restorations in class V anterior teeth cavities. The methode of this study used experimental laboratory through in vitro process . Thirty two class V cavities were prepared on labial surfaces of extracted human anterior teeth. Samples were divided into two groups. Group I included sixteen samples that have had restorated with microfiller composite. Group II included sixteen samples that have had restorated with resin-modified glass ionomer cement. The samples were immersed into aquabides solution for 24 hours. After that, the samples were immersed into 1% methylene blue solution for 24 hours. All samples sectioned longitudinally and analyzed for microleakage as dye penetration using a stereomicroscope.&#x0D; Student t-test were used for statistical analysis. The resulting data showed no significantly difference between two groups.&#x0D; Key Word : Microleakage, microfiller composite resin, resin-modified glass ionomer cement (RMGIC), class V cavities.

Определение времени вымывания из пласта изолирующего тампонажного материала на композитной основе

Определение времени вымывания из пласта изолирующего тампонажного материала на композитной основе

The effect of short fiber composite base on microleakage and load-bearing capacity of posterior restorations

Objectives: To determine the marginal microleakage of Class II restorations made with different composite base materials and the static load-bearing capacity of direct composite onlay restorations.Methods: Class II cavities were prepared in 40 extracted molars. They were divided into five groups (n = 8/group) depending on composite base material used (everX Posterior, SDR, Tetric EvoFlow). After Class II restorations were completed, specimens were sectioned mid-sagitally. For each group, sectioned restorations were immersed in dye. Specimens were viewed under a stereo-microscope and the percentage of cavity leakage was calculated. Ten groups of onlay restorations were fabricated (n = 8/group); groups were made with composite base materials (everX Posterior, SDR, Tetric EvoFlow, Gradia Direct LoFlo) and covered by 1 mm layer of conventional (Tetric N-Ceram) or bulk fill (Tetric EvoCeram Bulk Fill) composites. Groups made only from conventional, bulk fill and short fiber composites were used as control. Specimens were statically loaded until fracture. Data were analyzed using ANOVA (p = 0.05).Results: Microleakage of restorations made of plain conventional composite or short fiber composite base material showed statistically (p < 0.05) lower values compared to other groups. ANOVA revealed that onlay restorations made from short fiber-reinforced composite (FRC) as base or plain restoration had statistically significant higher load-bearing capacity (1593 N) (p < 0.05) than other restorations.Conclusion: Restorations combining base of short FRC and surface layer of conventional composite displayed promising performance related to microleakage and load-bearing capacity.

In vitro study of fracture strength of provisional crown materials.

PURPOSEThe purpose of this report was to evaluate the effect of the fabrication method and material type on the fracture strength of provisional crowns.MATERIALS AND METHODSA master model with one crown (maxillary left second premolar) was manufactured from Cr-Co alloy. The master model was scanned, and the data set was transferred to a CAD/CAM unit (Yenamak D50, Yenadent Ltd, Istanbul, Turkey) for the Cercon Base group. For the other groups, temporary crowns were produced by direct fabrication methods (Imident, Temdent, Structur Premium, Takilon, Systemp c&b II, and Acrytemp). The specimens were subjected to water storage at 37℃ for 24 hours, and then they were thermocycled (TC, 5000×, 5-55℃) (n=10). The maximum force at fracture (Fmax) was measured in a universal test machine at 1 mm/min. Data was analyzed by non-parametric statistics (α=.05).RESULTSFmax values varied between 711.09-1392.1 N. In the PMMA groups, Takilon showed the lowest values (711.09 N), and Cercon Base showed the highest values (959.59 N). In the composite groups, Structur Premium showed the highest values (1392.1 N), and Acrytemp showed the lowest values (910.05 N). The composite groups showed significantly higher values than the PMMA groups (P=.01).CONCLUSIONComposite-based materials showed significantly higher fracture strengths than PMMA-based materials. The CAD-CAM technique offers more advantages than the direct technique.

The influence of different restorative materials on secondary caries development in situ

ObjectivesThe effect of direct restorative materials on caries lesion formation was investigated with an 8-week in situ study with split-mouth design, testing the hypothesis that no difference in mineral loss next to a restoration would be found between different composite-based-materials and amalgam. MethodsSix groups (n=18) of restored dentine samples were prepared using amalgam, a microhybrid, a nanohybrid and a silorane composite. The composites were adhesively bonded with systems with or without an antibacterial monomer (Clearfil-SE-Protect, Clearfil-SE-bond, respectively), except for the silorane group (Silorane-System-Adhesive). Non-restored dentine samples were used as control (primary caries). Samples were inserted into slots, in lower prosthesis especially made for the experiment. Subjects were instructed to dip the lower prosthesis in a sucrose solution 4 times per day. At baseline and 8 weeks, samples were radiographed extra-orally and the integrated mineral loss was calculated. Data were statistically analyzed using multiple linear regression with a multilevel model (p=0.05). ResultsNine subjects were selected, and only outer lesions were observed. The hypothesis was partially rejected, as the microhybrid composite bonded with the antibacterial system and the nanohybrid composite presented statistically significant lower mineral loss compared to amalgam. Also, no significant differences were seen for these groups compared to control. ConclusionWithin the limits of this study, the restorative material may influence outer lesion progression. Amalgam was not found to be related to lower secondary caries progression in dentine compared to composite-based materials after 8 weeks in situ. Clinical SignificanceAlthough patient factors play a major role in caries progression, the restorative material may affect outer secondary lesion progression.

Effect of Traverse Speed on the Microstructure and Mechanical Properties in Friction Stir Welded Dissimilar Barrier Butt Joints of AA2024 to AA6061/SiC/55p Composite

Dissimilar barrier butt joints of AA2024 to AA6061/SiC/55p composite were fabricated by friction stir welding. Effect of the traverse speed on interface bonding, joint microstructure and tensile properties was investigated. Results revealed that, all joints possessed a tensile strength stronger than 80% that of the composite base materials, and the highest strength value was 178MPa. Macro interface can be readily identified in the weld zone between AA2024 and AA6061/SiC/55p composite, of which the area decreased and then increased as the traverse speed increased. The size and shape of SiC particles in the interface zone varied a lot due to different stirring effect and forward impact of the pin in different traverse speeds. Increasingly impairment of the composite base material near the interface was also detected with the traverse speed increasing.

The effects of in vitro fluoride mouth rinse on the antibacterial properties of orthodontic cements

To investigate the ability of orthodontic cements to regain their antibacterial effect after aging for 1 month, followed by 2 weeks of fluoride 'recharging' through daily fluoride rinse. Four orthodontic cements were tested: composite resin-based materials (Transbond XT and Transbond Plus), a conventional glass ionomer cement (CX Plus) and dual-cured resin-reinforced glass ionomer cement (Fuji ORTHO LC) by direct contact test. After polymerization and a 30-day aging process, the samples were rinsed daily with 0.05% NaF solution for 14 days. Twenty-four hours after the last fluoride rinse, Streptococcus mutans cells (approximately 1 x 10(6) ) were placed on the surface of each sample for 1 h at 37°C to establish direct contact. Bacterial growth was monitored for 24 h by temperature-controlled spectrophotometry. Similar experiments were conducted after aging for 48 h and 72 h after the last fluoride rinse. One-way anova, two-way anova, and Tukey's multiple comparison test were applied to the data. Twenty-four hours after the last fluoride rinse, the resin-modified glass ionomer and the glass ionomer showed potent antibacterial properties, whereas the composite-based material Transbond XT encouraged bacterial growth. After 72 h, only Fuji Ortho LC maintained its bacteriostatic properties while all the other tested materials showed no antibacterial activity. Fourteen days daily fluoride rinse temporarily revives the antibacterial properties of the resin-modified glass ionomer cement and glass-ionomer-based cement.

Bulk-fill-composites. Modern application technique of direct composites for posterior teeth

Direct composite restorations in the posterior dentition have become an indispensable element of modern dentistry. The performance of these restoration, even in the masticatory load-bearing posterior region, has been conclusively proven in many clinical studies. This procedure is usually carreid out in an elaborate layering technique. This time-consuming procedure requires an economically sensible fee, corresponding to the effort involved. Aside from the possibilies that highly aesthetic composites offer in the application of polychromatic multiple-layer techniques, there is also a great market demand for the most simple and quick and therefore economical composite-based materials for posterior teeth. These products are offered in the category of bulk-fill composite.

Microleakage of glass-ionomer, flowable composite, biodentine and fiber-reinforced base materials

Microleakage of glass-ionomer, flowable composite, biodentine and fiber-reinforced base materials

Cuspal deflection of directly or indirectly restored teeth

Objective: The aim of this study was to evaluatethe cuspal deflection of teeth restored directlyand indirectly. Material and Methods: Fortysound maxillary premolar teeth were restoredwith composite and different base materials. Widemesial-occlusal-distal cavity preparations wereperformed, with isthmus width of one third of thedistance between the cuspal tips, 3 mm occlusaland a 5 mm interproximal preparation height. Theteeth were divided into 4 groups (n = 10), accordingto the restoration type: G1) GIC-DCR (1 mm glassionomer cement base and direct restoration usingnanoparticulate composite); G2) FL-DCR (1 mm baseof flowable composite resin and direct restorationusing nanoparticulate composite); G3) GIC-ICR(1 mm glass ionomer cement base and indirectrestoration using nanoparticulate composite GICbase); G4) FL-ICR (1 mm base of flowable compositeresin and indirect restoration using nanoparticulatecomposite). The specimens were submitted tocompressive load of 50 N on the buccal and lingualcusps, in a universal testing machine. The lingualcusp microstrain (??) measurements were executedby strain gauges. Results: The Kruskal-Wallis (5%)test was used and showed there were no significantdifferences among the microstrain values for the fourstudy groups (G1 = 1250; G2 = 1075; G3 = 1279;G4 = 937). Conclusion: It could be concluded thatthe restorative techniques and the bases employeddid not show any influences in cuspal deflection.KeywordsBase materials; Cuspal defection; Composite resin; Direct restoration; Indirect restoration.

Stable extreme damping in viscoelastic two-phase composites with non-positive-definite phases close to the loss of stability

By investigating the effective response of linear viscoelastic composites, we demonstrate that stiff systems can exhibit stable extreme increases in overall damping if one of the composite phases loses positive-definiteness of its elasticities. While non-positive-definite elastic moduli (often referred to as negative stiffness) are thermodynamically unstable in unconstrained homogeneous solids, the geometric constraints among constituents in a composite can provide sufficient stabilization. Allowing for negative-stiffness phases in principle expands the range of attainable composite properties and promises extremely high composite stiffness and damping (significantly beyond those of the composite base materials) if the composite is appropriately tuned. This, however, raises questions of stability. In particular, the resulting high damping in stiff composites so far has only been shown to be stable in simple structural and elementary spring-dashpot systems, and therefore has remained a key open question for general composite materials. Studying successively the examples of a spring-dashpot model, a two-phase solid, and a general particle–matrix composite, we demonstrate that a non-positive-definite phase may indeed result in stable extreme damping, which is in line with recent experimental findings.

Tensile bond strength of PMMA- and composite-based CAD/CAM materials to luting cements after different conditioning methods

This study investigated whether the adhesion of novel generation of polymeric CAD/CAM resins to luting cements would improve after use of different conditioning methods, and to evaluate the failure types after debonding. Two CAD/CAM resins (PMMA- and composite-based) were obtained (N=600, n=15 per test group). The specimens were conditioned as follows: MH: Monobond Plus/Heliobond, VL: Visio.link, AM: Ambarino P60, VP: VP connect, CG: no conditioning as control group, and luted with conventional (Variolink II) or self-adhesive luting cement (Clearfil SA Cement). Two types of storage were performed: after 24h water storage (37°C) and additional 5000 thermal cycles (5°C/55°C). Tensile bond strength (TBS) was measured and data were analysed using 4/1-way ANOVA (Scheffé test), independent two-sample t-test and Chi2 test (alpha=0.05). For both CAD/CAM resins, no or lower bonding was observed for the non-conditioned or AM groups, regardless of the luting cement. The conditioning with MH, VL and VP showed significant increase of TBS. In general, bonding on exp. CAD/CAM composite presented significant higher values compared to PMMA-based artBloc Temp. Variolink II showed higher TBS in combination with artBloc Temp. After conditioning with MH and VL predominantly cohesive failures in the luting cement were observed. All other groups showed adhesive failure. Aging level did not affect the TBS. The bonding properties of the CAD/CAM resin materials are dependent of the targeted selection of the conditioning method and luting cement. Composite-based materials showed higher bonding properties to luting cements than PMMA-based.

Effect of different adhesives combined with two resin composite cements on shear bond strength to polymeric CAD/CAM materials

This study tested the impact of different adhesives and resin composite cements on shear bond strength (SBS) to polymethyl methacrylate (PMMA)- and composite-based CAD/CAM materials. SBS specimens were fabricated and divided into five main groups (n=30/group) subject to conditioning: 1. Monobond Plus/Heliobond (MH), 2. Visio.link (VL), 3. Ambarino P60 (AM), 4. exp. VP connect (VP), and 5. no conditioning-control group (CG). All cemented specimens using a. Clearfil SA Cement and b. Variolink II were stored in distilled water for 24 h at 37 °C. Additionally, one half of the specimens were thermocycled for 5,000 cycles (5 °C/55 °C, dwell time 20 s). SBS was measured; data were analyzed using descriptive statistics, four- and one-way ANOVA, unpaired two-sample t-test and Chi(2)-test. CAD/CAM materials without additional adhesives showed no bond to resin composite cements. Highest SBS showed VL with Variolink II on composite-based material, before and after thermocycling.

Field-responsive smart composite particle suspension: materials and rheology

Both electrorheological (ER) and magnetorheological (MR) fluids are known to be smart materials which can be rapidly and reversibly transformed from a fluid-like to a solid-like state within milliseconds by showing dramatic and tunable changes in their rheological properties under external electrical or magnetic field strength, respectively. Here, among various smart composite particles studied, recently developed core-shell structured polystyrene/graphene oxide composite based ER material as well as the dual-step functionally coated carbonyl iron composite based MR material are briefly reviewed along with their rheological characteristics under external fields.

Application of modified polypropylene (crude) fibers concrete to strengthen the support structures in deep mine roadway

The an thors developed a new composite cement base material by mixing the high tenacity polypropylene (coarse) fiber in plain cement base for the cement-layer-spray technology. By studying the key parameters of the fiber dosage, the spray layer thickness, and the fiber reinforced concrete injection time, etc. It is found that the ideal volume ratio of polypropylene (crude) fiber is 0.8% (V/V), and the secondary lining fiber concrete spraying should start when the shrinkage rate is lower than 0.5 mm/d, and the optimal thickness of shotcrete is 120 mm. The supporting effects and the economic benefits were studied using a real project practice, and the result obtained can be a good reference for practical applications of this new supporting material in the future.

Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials

ObjectivesTo assess the cuspal deflection and cervical microleakage of standardised Class II cavities incrementally filled with a dimethacrylate RBC or bulk-fill flowable RBC bases. MethodsTwenty-four sound upper premolar teeth with Class II cavities were allocated to three groups (n=8). Restoration of the teeth involved the placement of an RBC (GrandioSO) in eight oblique increments (Group A) or Groups B and C were restored to within 2mm of the palatal cusp in a single increment with bulk-fill flowable RBC bases (SDR and x-tra base) before the two occlusal cavity increments were placed with GrandioSO. Buccal and palatal cusp deflections were recorded postirradiation using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in 0.2% basic fuchsin dye for 24h, sectioned and examined for cervical microleakage. ResultsThe mean total cuspal deflection for the oblique incremental restoration technique was 11.26 (2.56)μm (Group A) and 4.63 (1.19)μm (Group B) and 4.73 (0.99)μm (Group C) for the bulk-fill flowable RBC bases. A significant increase in the mean total cuspal deflection for the incrementally filled GrandioSO compared with the SDR (P=0.007) and x-tra base (P=0.005) restored teeth was evident. No significant difference in the cervical microleakage scores was recorded between groups AC (P>0.05). ConclusionsThe bulk-fill flowable RBC bases significantly reduced cuspal deflection compared with a conventional RBC restored in an oblique incremental filling technique with no associated change in cervical microleakage recorded.

Optimization of Multilayer Shields Made of Composite Nanostructured Materials

In this paper, we propose a multilayer nanostructured composite for broadband shielding applications. Layers disposal, electrical parameters, and thicknesses are optimized through a winning particle optimization algorithm to achieve the minimization of the transmitted waves. The structures are simulated by including the forward/backward scattering matrix formalism in the optimization code. The adopted algorithm is the recently introduced winning particle optimization. Manufacturing of the composites is grounded on the optimization procedure. Thanks to the macroscopic absorption features of such nanostructured layers, very thin and lightweight composites can be produced. Several weight percentages of multiwall carbon nanotubes are considered in composite base material manufacturing, also including 6wt% and 15wt% in order to enhance the electromagnetic shielding performance. Prototypes are tested in the microwave region, showing the reliability of the optimization procedure.