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OBJECTIVE To analyze the wear rate of computer-aided design and computer-aided manufacturing (CAD/CAM) composites, polyetheretherketones and glass ceramics. MATERIAL AND METHODS Our study groups were prepared from two different resin-based composites (Brillant Crios, Cerasmart), a glass ceramic (IPS Emax CAD) and reinforced polyetheretherketone (BioHPP) material (n = 10). Premolar teeth were used as antagonists. The specimens, which were subjected to two body wear tests (240,000 cycles, 1.2 Hz, 50N) in the chewing simulator, were scanned with a 3D laser scanner both before and after the wear test. Volume loss and wear depth were determined by means of the obtained images software program. The wear pattern was examined by scanning electron microscopy. Kruskal Wallis test served for analyzing. RESULTS The least volume loss and wear depth were seen in the polyetheretherketone material (0.06 ± 0.04 mm3 , 0.02 ± 0.01 mm), while the maximum volume loss was seen in the groups containing resin-based composite. (p = 0.05). The volume loss value in glass ceramics is between CAD/CAM composites and polyetheretherketone. CONCLUSION The behavior of polyetheretherketone against enamel was different from glass ceramics and composite materials in terms of the amount of wear. CLINICAL SIGNIFICANCE Polyetheretheketone can be considered as an alternative to other chairside materials in terms of wear resistance.

We propose the equation of glass transition of resin basing on experimental investigations of influence of the composition of the epoxy diane resin based composite on the glass transition temperature. It is observed experimentally by the Differential Scanning Calorimetry that the glass transition temperature of non-modified ED-20 resin increases with the hardener L-20 mass fraction. The addition of organosilicon filler PDMS-5 increases little the glass transition temperature from 80 to 85 °C. The addition of nanodispersed pyrogenic silica HDK filler significantly increases the glass transition temperature up to 116 °C. A theory describing the three athermal plateaus in the dependence of the glass transition temperature on the hardener mass fraction is formulated. The equation of glass transition sufficiently fitting the measured points of the glass transition temperature is found. The formulated equation can be useful to prediction the glass transition temperatures of polymer composites based on epoxy resins.

Background/purpose It is not clear whether the ground surface of resin-based composite (RBC) polymerized requires the application of an adhesive with/without a silane to improve bond strength. This study investigated the bond strength of RBC repaired within 24 h via the application of adhesive with/without a silane. Materials and methods Seventy RBC blocks were prepared and assigned to either 0 or 24 h repair stage. Each stage was divided into seven groups: a control group with no surface roughening or applied adhesive, a surface-roughened group with no applied adhesive, two surface-roughened groups treated with a G-aenial Bond adhesive and a BeautiBond Multi adhesive, two surface-roughened groups treated with the previously-mentioned adhesives as well as silane coupling agents, and one group treated with a Single Bond Universal silane-containing adhesive. Microtensile bond strength (μTBS) measurements were performed after the repaired RBC blocks of each group (n = 5) had been immersed in a 37 °C water bath for 24 h. The failure mode of each sample was determined, and the data were analyzed via one-way analysis of variance and Dunnett's test (p = 0.05). Results Regardless of the repair stage, the μTBS values of the adhesive-only and silane-adhesive groups did not differ significantly from those of the control group (p > 0.05). Only the no-adhesive groups exhibited a significantly time-dependent increase in adhesive failure rate. Conclusion Our results suggest that the application of adhesives either with or without silane can significantly increase the bond strength of repairs to RBCs polymerized within 24 h.

Purpose: This study examined the effect of different distances and curing times on the microhardness (VHN) of nanofilled resin-based composite (RBC) restorations polymerized with high-intensity LED LCUs. Materials and methods: Seventy-five RBC specimens (2 mm thickness and 5 mm diameter) were fabricated from Tetric-N-Ceram (Ivoclar Vivadent). Each of the 25 specimens was polymerized by means of one of three types of high-intensity LED LCUs: (B) Blue-Phase-G2 (polywave LED, Ivoclar Vivadent), (E) Elipar S10 TM (single-peak, 3 M ESPE), and (P) Planmica Lumion (single-peak, Mectron) at three different distances (0 mm, 2 mm, and 4 mm) at 20 sec, 40 s, and 60 sec. A microhardness tester (NOVA, Innovatest, The Netherlands) was used to measure the VHN from the top and bottom surfaces. Data for VHN were analyzed using mixed ANOVA, followed by post hoc analyses with p-values

Objectives Publications on stamp techniques for placing resin-based composite (RBC) restorations consist mainly of case studies. Furthermore, comparative studies are rare and no longer relevant to the materials tested today. Thus, two general techniques were investigated in this study. Materials and methods Standardized occlusion class I cavities were prepared in twenty-eight extracted caries-free wisdom teeth with unimpaired occlusal surfaces and restored with the RBC material Grandio®. Light curing of the final layer was performed either after removal of the stamp isolated with PTFE tape or by leaving a stamp made of transparent polysiloxane in place. CEREC scans of the RBC restorations placed (follow-up) were superimposed on scans of the unimpaired occlusal surface (baseline) and quantitatively analyzed with the software OraCheck with regard to volume change and gain or loss of layer thickness in six sectional planes. Results Assessing the excess material, there was no difference (p = 0.31) between the silicone technique (0.26 mm ± 0.02) and the PTFE technique (0.22 mm ± 0.02 mm). Nevertheless, the loss of tooth substance was significantly greater (p < 0.001) with the silicone technique (−0.29 mm ± 0.02 mm) than with the PTFE technique (−0.15 mm ± 0.02 mm). Conclusions With the PTFE stamp technique, less healthy tooth structure was removed during the finishing procedure and the stamp was more dimensionally stable. Clinical relevance The study shows the advantages and disadvantages of the investigated stamp techniques and helps the practitioner to choose an appropriate technique.

Objective: The objective of our research is to study the tribological behaviour of two types of commercially available resin-based composite materials. Material and method: An original experimental model for tribological studies of dental materials in standard test conditions was applied. Two types of resin-based composite materials indicated for the treatment of dental caries in the distal area were used: a micro-hybrid resin-based composite material (Gradia Direct posterior); packable resin-based composite material (Filtek P60). Metal alloy (Duceralloy C) was used for positive control. Total 18 test samples (n=9 for each material) were subject to: micro scratch resistance test in 1N, 5N, 9N mode; friction resistance "Ball-on-Flat" test at 120,000/240,000 cycles loaded on 50N. Results: When the maximum load was applied, Gradia Direct posterior had higher values of scratch depths (40, 23 µm) than Filtek P60 (25,13 µm). The micro-hybrid composite exhibited less wear resistance that decreased with increasing time and friction cycles (13 µm after 30 min/120,000 cycles; 18 µm ether 60 min/240,000 cycles). The examined surfaces of the test specimens were visualized by optical microscopy after micro scratch and friction test and by 3D profilometry of all tested samples after 240,000 wear cycles. Conclusion: Results in this field might clarify the mechanisms of wear and provide additional information on the expected changes in the studied materials in clinical practice.

Fiber-reinforced resin-based composite stiffened panels are put in the hygrothermal box at 70°C and 85% RH until moisture absorption reaches balance. Then, the compression experiments on the common stiffened panels and the stiffened panels after moisture absorption are conducted to get buckling and failure loads. Test results are compared to analyze the effect of damage on the carrying capacity of the structure. The buckling load does not significantly change, but the failure load of the panels after moisture absorption is reduced by 10.2% as compared to the common panels. The failure modes are mainly composed of debonding and fracture of the stiffener, the skin cleavage and deformation of the specimen. The experimental results will offer some valuable guidelines to engineering applications of the structure.

Objective The study aimed to investigate factors contributing to heat development during light curing of a flowable bulk-fill resin-based composite (SDRTM, Lot # 602000876, Dentsply Sirona, Konstanz, Germany) (RBC). Materials and Methods Temperatures were measured with calibrated thermocouples. A multi-wave light-emitting diode (LED) light curing unit (LCU) was used (Ivoclar Vivadent, Schaan, Lichtenstein). In all experiments, the RBC was first cured (cured) for 30 s and, after 5 min of recovery time, received a second LCU irradiation (post-cured) for 30 s. The exothermic reaction was measured by calculating the Δ temperature between cured and post-cured RBC. In a cylinder-shaped polymer mold, temperature was recorded inside of RBC during curing (part 1) and light transmission through RBC during curing was investigated (part 2). Pulpal temperatures were assessed in an extracted third molar during light curing (part 3). Data were statistically analyzed using one-way ANOVA (α=0.05). Results Increased thickness of RBC led to decreased pulp chamber temperatures. Inside RBC, there was a large variation in heat development between the cured and post-cured groups (p

The aim of this study was to investigate the influence of various specimen storage conditions on the properties (surface hardness, biaxial flexural strength (BFS), water sorption and solubility) of...

The aim of this article was to compare the biomechanical properties of commercial composites containing different photoinitiators: Filtek Ultimate (3M ESPE) containing camphorquinone (CQ), Estelite Σ Quick (Tokuyama Dental) with CQ in RAP Technology®, Tetric EvoCeram Bleach BLXL (Ivoclar Vivadent AG) with CQ and Lucirin TPO, and Tetric Evoceram Powerfill IVB (Ivoclar Vivadent AG) with CQ and Ivocerin TPO. All samples were cured with a polywave Valo Lamp (Ultradent Products Inc.) with 1450 mW/cm2. The microhardness, hardness by Vicker’s method, diametral tensile strength, flexural strength and contraction stress with photoelastic analysis were tested. The highest hardness and microhardness were observed for Filtek Ultimate (93.82 ± 17.44 HV), but other composites also displayed sufficient values (from 52 ± 3.92 to 58,82 ± 7.33 HV). Filtek Ultimate not only demonstrated the highest DTS (48.03 ± 5.97 MPa) and FS (87.32 ± 19.03 MPa) but also the highest contraction stress (13.7 ± 0.4 MPa) during polymerization. The TetricEvoCeram Powerfill has optimal microhardness (54.27 ± 4.1 HV), DTS (32.5 ± 5.29 MPa) and FS (79.3 ± 14.37 MPa) and the lowest contraction stress (7.4 ± 1 MPa) during photopolymerization. To summarize, Filtek Ultimate demonstrated the highest microhardness, FS and DTS values, however, composites with additional photoinitiators such as Lucirin TPO and Ivocerin have the lowest polymerization shrinkage. These composites also have higher FS and DTS and microhardness than material containing CQ in Rap Technology.

Context: The effect of bleaching on tooth coloured restorative materials remains controversial, in terms of colour and tooth restoration interfaces. Few studies investigated affirming the action of different light sources used as an adjunct to in-office bleaching and its effect on recently introduced resin based composite restorations. This study focuses on the behaviour of nano hybrid composite exposed to Diode laser and LED bleaching techniques. Aims: The purpose of this in vitro study is to compare and evaluate the effect of Diode Laser and LED activated bleaching on colour and micro leakage of nano hybrid composites in Class V cavities.Methods and Material: Standardized Class V cavities were prepared on fifty freshly extracted human first maxillary premolar teeth, and restored with nano hybrid composite (Tetric N-Ceram). The samples were randomly divided into three groups and bleaching agent used is 40% Opalescence Boost (Ultradent) in all the three groups. Group 1 was activated with Diode laser (Picasso), Group 2 was activated with a blue hybrid LED (Bluephase) and Group 3 did not receive any light activation. Group 4- control group (unbleached restoration n=5). Restoration colour was measured before bleaching and after bleaching using VITA Compact Easy shade spectrophotometer and CIELAB values of ΔE, Δa*, Δb* and ΔL* were obtained. The same samples with the control group were subsequently immersed in dye solution of 2% Methylene blue and subsequently dye extraction technique was used to evaluate the micro leakage using spectrophotometer.Statistical analysis used: The results were subjected to ANOVA, Tukey and HSD tests (p3.3) in all the three groups. One-way ANOVA indicated no statistical difference in colour difference (p

Resin-based composites (RBCs) are commonly used in dental restorations. It is known that RBCs undergo volumetric shrinkage during photo-polymerization leading to a detrimental increased stress state at the RBC-tooth interface and potentially early restoration failure. The objectives of this in vitro study were: (1) to ascertain whether shrinkage strain could be measured using in-fibre Bragg grating (FBG) technology, without confounding effects of temperature; and (2) to ascertain whether FBGs can detect alteration in shrinkage strain with introduction of a surface condition change at the RBC-cavity analog interface.Aluminum cavity analogs with simulated cavity dimensions 3.5 mm height x 2 mm width x 8 mm length and 2 mm wall thickness were secured in a 3D printed experimental jig. Two FBGs were used in the RBC space, one that was covered with a polyimide tube and that measured only temperature, and another that was affected by both mechanical strain and temperature. Experiments to determine if the two FBG system could be used to compensate for thermal artefacts were contrived to verify that a tube-covered and bare FBG measure the same temperature effect (n = 5). In situ photo-polymerization experiments, which consisted of using controlled amounts of SureFil SDR Flow + RBC, were performed to study RBC shrinkage behavior. As-machined (n = 10) and micro-etched (n = 11) cavity analogs were used. Significant differences in FBG measurements, which could indicate the ability of FBGs to detect alterations in strain across surface preparations, were determined using one tail t-tests at 95% confidence. Finally, additional temperature experiments were conducted 5 h after initial light exposure using the same light irradiation regiment to investigate temperature effects within a cured RBC system (n = 3).For temperature measurement, the tubing-covered and bare FBGs measured temperature changes with time-lag of 3.7 ± 1.4 s (tubing-covered FBG relative to bare). For measurements in cured RBC, the bare FBG and tubing-covered FBG measured different strains, with the bare FBG measuring larger apparent strains because this FBG is affected by thermal volumetric expansion of the RBC and a temperature increase of the FBG itself. The tubing covered FBG, that is isolated from volumetric expansion effects, measured relatively less. The interpretation of these results is that thermally-compensated strain measures (in-situ) could require simultaneous use of two FBGs (one strain isolated). In situ measurements of the photo-polymerization procedure for as-machined analogs at two time-points, 500 and 1000 s, were determined to be -485.43 ± 131.06 μstrain and -524.96 ± 134.78 μstrain, respectively. For air-abraded surfaces measures were significantly lower at (p 0.001) -211.36 ± 12.38 μstrain and -228.07 ± 49.08 μstrain, respectively.To measure shrinkage strain and compensate for associated thermal effects from photo-polymerization, systems employing two FBGs, one of them isolated from thermal volumetric expansion, may be required. The presented approach proved capable of detecting significant alteration in strain across two surface preparations.

Purpose The purpose of this paper is to investigate the effect of reciprocating and unidirectional sliding motions on friction and wear of phenolic resin-based composite. Design/methodology/approach The phenolic resin-based composite was fabricated by hot press molding, and then the tribological properties were tested on a CSM tribometer with two types of friction motion modes – reciprocating friction and unidirectional friction. Findings The results showed that the composite exhibited low friction coefficient in unidirectional test. However, the wear factor recorded under unidirectional sliding condition was 12-16 times higher than the reciprocating friction results. The SEM and optical microscopy test results showed that changing the relative motion mode resulted in different topography of transfer film, which is responsible for the different friction and wear characteristics of the composite under reciprocating and unidirectional friction conditions. Originality/value Effect of different friction modes, reciprocating friction and unidirectional friction, on friction characteristics of the composite is sought. Different topography of transfer film formed under reciprocating and unidirectional friction conditions contributed to the different friction characteristics.

Resin based composite is the most accepted material for the restoration of decayed tooth. To improve the composite material in physical, clinical, as well as to facilitate manipulation technique various modifications have been done in its structure. Polymerization shrinkage stress, being its major drawback which affects the core of the filling and its bonding with tooth structure. This polymerization shrinkage would lead to numerous clinical consequences such as poor marginal adaptation, resulting into microleakage, development of secondary caries and subsequent pulpal inflammation. Another drawback being reduction in degree of conversion which affects the physical properties and increases the monomer proportion, which could lead to post operative sensitivity and early failure of composite filling. Bulk fill composite is recently introduced as an advancement in resin based restoration which claims to overcome the drawback of conventional composite. Therefore the review of this literature could be a helpful for dentists to use these new promising restorative materials with long term clinical outcome. Keywords: Bulk fill composite, Depth of cure, Degree of conversion, Surface hardness.

In this study, the silanized coal fly ash (CFA) and silanized nano-/micro-glass fiber (nGF) were simultaneously embedded in vinyl ester resin for improvement in both mechanical properties and mode I interlaminar fracture toughness of carbon fiber-based composite material. The used CFA particles have thermal power plant origin and were grinded with the help of ball mill to obtain the uniform size. The methacryloxy groups were attached to surface of both ground CFA and pristine nGF via silanization process. The homologous mixtures of S-nGF and S-CFA in vinyl ester resin were obtained with the help of high-speed mechanical stirrer and ultrasonic technique. The sheet molding compound method and hot curing process were applied to fabricate the carbon fiber-filled vinyl ester resin-based composite. Many techniques such as FTIR, EDS, rheological testing, mode I interlaminar fracture toughness, tensile strength and SEM were used to investigate the characteristics of silanized additives, the uncured matrices as well as the carbon fiber-based composite materials. The incorporation of both 0.1 wt% S-nGF and 1 wt% S-CFA into VE resin helps to improve the tensile strength, tensile modulus and the mode I interlaminar fracture toughness (GIC) of carbon fiber-based composites (CFRP) by 61.39%, 39.83% and 48.61%, respectively, when compared with pristine composite material. The fracture toughness surface of modified VE was tougher and rougher as a result of higher fracture toughness, while the pristine VE exhibited the smooth surface.

This case report presents a new approach for shock-absorbing carbon-fiber composite frameworks for full-arch implant-supported fixed dental prostheses supporting resin-based and lithium disilicate ceramic crowns. It describes the characteristics of the materials used, the procedures for implementing the framework, and the requirements to achieve the best mechanical and clinical properties. The result is a full-arch prosthesis with masticatory load shock-absorption capacities, chemical bonding between materials, good esthetics, and wear similar to natural enamel. A 24-month follow-up full-arch bimaxillary implant-supported rehabilitation, performed with computer-guided surgery, is described.

E-glass fiber mat reinforced Unsaturated Polyester Resin (UPR)-based composites were fabricated by conventional hand lay-up technique. The fiber content was varied from 5 to 50% by weight. Mechanical properties (tensile and bending) of the fabricated composites were investigated. The tensile strength (TS) of the 5% and 50% fiber reinforced composites was 32 MPa and 72 MPa, respectively. Similarly, tensile modulus, bending strength and bending modulus of the composites were increased by the increase of fiber loading. Interfacial properties of the composites were investigated by scanning electron microscopy (SEM) and the results revealed that the interfacial bond between fiber and matrix was excellent. Keywords: Unsaturated Polyester Resin, Mechanical Properties, E-glass Fibers, Composites, Polymer.

The objective of this study was to measure temperature changes in the pulp chamber induced by polymerization of resin-based dental restoratives following a simulated procedure of direct pulp capping. Class I cavities with a microperforation at the pulp horn were prepared in extracted human molar teeth. The complete procedure of direct pulp capping and cavity restoration was performed with the root part of extracted teeth fixed in a water bath at 37 °C. Mineral trioxide aggregate, bioactive dentin substitute or calcium-hydroxide paste were used as pulp capping materials. Cavities were restored with a light-cured or chemically-cured resin-modified glass ionomer, universal adhesive and a bulk-fill composite, cured with a high-intensity LED unit. Pulp capping materials caused a slight temperature decrease. Lower temperature increase was recorded during light-curing of the glass ionomer liner after direct capping with mineral trioxide aggregate and calcium-hydroxide than that recorded for the bioactive dentin substitute. Adhesive light-curing increased temperature in all groups with higher mean temperatures in groups with chemically-cured as compared to those for the light-cured glass ionomer liner. Direct pulp capping with mineral trioxide aggregate or calcium-hydroxide followed by the light-cured resin-modified glass ionomer liner and a bonded bulk-fill composite restoration induced temperature changes below the potentially adverse threshold of 42.5°C. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172007]

Nojoud Alshehri, Mohammed Bin-Shuwaish Restorative Dental Sciences Department, College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi ArabiaCorrespondence: Nojoud AlshehriCollege of Dentistry, King Saud University, Kingdom of Saudi ArabiaTel +966 11 489 4865Email alshehri.nojoud@gmail.comPurpose: To evaluate the effect of amalgam contamination, different surface treatments, and adhesive protocols on dentin shear bond strength (SBS) to bulk-fill composite resin material.Materials and Methods: Eighty teeth were fixed in molds, and the dentin was exposed and then polished. Sixty teeth were restored by amalgam and thermocycled to 10,000 cycles (5°C and 55°C, 30-second dwell time). The rest were restored with composite materials without amalgam predecessor. The samples were divided into G1 (with dentin pretreatment with 2% chlorhexidine gluconate), G2 (0.5 mm of dentin was removed), G3 (no surface modification), and G4 (samples were restored with bulk-fill composite). The bonded specimens were subdivided based on the adhesive protocol of the universal adhesive system used into etch-and-rinse and self-etch groups. Acid etching was done using 32% phosphoric acid. Composite resin was used for build-up using mold and glass. Specimens were cured and left for 24 h in distilled water at room temperature for polymerization reaction, underwent thermocycling for 5000 cycles, and were subjected to knife-edge shear bond testing. Descriptive statistics, independent t-tests, and one-way analysis of variance followed by pairwise comparisons were used to analyze the results.Results: The highest mean SBS values were found in the control group where acid etching was used (24.46± 2.24 MPa), followed by self-etching in the same group (21.92± 2.54 MPa). Lower SBS values were associated with the amalgam-contaminated group. The lowest values were found in the dentin refreshment group when the self-etching mode was used (13.59± 1.73 MPa). Chlorhexidine treatment improved the mean SBS value compared with the no treatment or dentin refreshment groups for both adhesive protocols.Conclusion: Amalgam contamination may affect SBS values. Acid etching improved SBS for non-contaminated dentin. Chlorhexidine improved SBS for amalgam-contaminated dentin as a surface treatment but had no significant effect.Keywords: chlorhexidine, dentin refreshment, resin-based composite, universal adhesive system

INTRODUCTION: One of the main causes of composite replacement is its discoloration after prolonged exposure to the oral environment. In an effort to fulfill the patient esthetic desire, harmonize composite material have been introduced with limited studies regarding its esthetic properties and color stability.OBJECTIVES: To study the effect of coffee on the color stability of two nanohybrid composites with different monomers.MATERIALS AND METHODS: The resin composites tested were Venus diamond and Harmonize. A custom made disk-shaped mold (4mm thickness x 8 mm diameter) used to prepare 12 composite specimens. They were divided into 2 groups (n=6) according to the resin based composite that was used as follow: Group A restored with Urethane dimethacrylate based composite (Venus diamond, Heraeus Kulzer) and Group B restored with Bisphenol A diglycidil dimethacrylate based composite (Harmonize, Kerr). The specimens were finished using (Multi fluted tungsten carbide finishing bur for fifteen seconds) followed by polishing using (HiLuster, Kerr) polishing system. After that, the specimens were immersed in coffee solution for 7 days. Color difference ΔE was calculated before and after immersion of specimens for 48 hours and after 7 days using spectrophotometer (VITA easy shade).RESULTS: Mann Whitney U test showed significant difference in ΔE among composite restorative materials (p < 0.05). Venus diamond composite resin was found to be more stain-resistant than Harmonize composite resin after both 48 hours and 7 days.CONCLUSION: Different monomer compositions, immersion time and solution may have direct effect on the color stability of nanohybrid restorative materials.

In recent years, there has been a growing need for natural fibre reinforced composite materials especially materials with good mechanical properties in order to substitute glass fibre based composite products to showcase a better engineering class for structural applications. Here the properties of jute fabric reinforced composite has been compared and analysed with e-glass fibre matte reinforced composite. The mercerized jute and e- glass fibre mats are treated with isophthalic resin. Charcoal powder has been used as a filler material constituting two percentage of the whole weight of entire composite. Isophthalic polyester resins offer substantially higher strength, better flexibility and chemical resistance. The properties of the jute composite and e-glass composite are determined by a series of tests such as Tensile, Flexural, Impact, Scanning Electron Microscopy (SEM) and Rate of Burning tests. The newly obtained composites provide a better usage for applications that require a much better physical strength and mechanical properties.

Objective: To compare the elastic modulus, flexural strength, and hardness of an experimental resin based composite (RBC) with and without containing silver nanoparticles (AgNPs) and bioactive glass (BAG) with a commercially available RBC. Methods: This study was conducted, during the period August 2016-May 2018, at the Department of Dental Materials, Peshawar Dental College, Peshawar (Pakistan) and Department of Chemistry, University of Montreal, Canada. Test specimens made in the commercial RBC acted as Group-1 (G1). An experimental RBC containing 70 wt % filler content was synthesized. It was first used as such to prepare test specimens to act as the experimental control group (G2). This RBC was then modified by adding various amounts of BAG (5%, 10% and 15%) and a fixed amount of 0.009% AgNPs to use the so modified RBCs for preparing the test specimens to belong to three groups (G3, G4 & G5). The AgNPs had been synthesized in situ by reduction of salt during photo-polymerization. Flexural strength (FS), elastic modulus (EM) and Vickers hardness were determined using universal testing machine and hardness tester respectively. Data were analyzed using one-way ANOVA and Tukey post-hoc test. Results: Except for G3 restorations showing significantly lower mean FS value, the FS for those in the other groups were not significantly different (p>0.05). Elastic modulus of the experimental RBC restorations was though higher than those of the others but the difference was statistically insignificant (p>0.05). Reduced Vickers hardness values were documented for the restorations in the G4 and G5 compared to those in the G3 but again the difference was insignificant (p>0.05). Flexural strength and hardness values of the test specimens in the experimental RBCs were significantly lower than those made in the commercial hybrid RBC (p

Objective This study evaluates critical material properties resulting from ultra-fast (3 s) photo-polymerization at high radiant emittance of a pre-production, novel bulk-fill resin-based composite (RBC) modified for reversible addition-fragmentation chain transfer (RAFT) polymerization. Methods The output characteristics of the associated light curing unit (LCU) were measured on a laboratory-grade spectrometer. Real-time Fourier Transform Infrared Spectroscopy (FTIR) and mechanical investigations (depth-sensing indentation with a linear and spatial distribution of the measured properties, and three-point bend tests) were performed using, as reference material, an established bulk-fill RBC of comparable chemical composition. Micro-mechanical properties were mapped to quantify material tolerance to sub-optimal curing conditions (exposure distance of 5 mm and an angulation of the LCU of 20° and 30°) vs. ideal curing conditions (exposure distance of 0 mm and no angulation), with 3 s polymerization. Weibull statistics, one- and multiple-way analysis of variance (ANOVA) and the Tukey honestly significant difference (HSD) post hoc-test (α = 0.05) were used for data comparison. Results The change in cure mechanism to RAFT polymerisation gave slightly faster initial polymerisation kinetics, but DC measured 300 s post irradiation was similar, irrespective of material, curing depth or polymerisation condition. Slightly better polymerisation, in layers thicker than 4-mm, was identified in the RAFT polymerised RBC. However, slightly lower flexural modulus and hardness, up to 1.5-mm subsurface, were related to the ca. one wt.% lower inorganic filler content. Significance RAFT polymerisation induced comparable properties to a RBC cured via free radical polymerisation of comparable chemical composition. The RAFT polymerised RBC with high irradiance for 3 s was equivalent to 10 s of moderate irradiance. However, the clinical tolerance for 3 s irradiance should be limited to an exposure distance of 5-mm and angulation of the LCU should be avoided. If this is not possible, an additional 3 s polymerisation is recommended.

CAD/CAM-generated resin-based composite crowns have been proposed as an inexpensive alternative to conventional crowns. However, concerns have been raised about crown loosening in clinical use. Therefore, the present in vitro study aimed to evaluate the influence of thermal and mechanical cycling (TC and MC) on retentive strength of CAD/CAM resin-based crowns in relation to microscale expansion and contraction caused by fatigue. Eighty standardized dies were produced using a resin-based composite material. Crowns were milled from resin-based composite (n = 40) and glass-ceramic blocks (n = 40; control) using a dental CAD/CAM system. The crowns bonded to the dies were subjected to TC (temperature: 5 and 55 °C, cycles: 50,000) and MC (load: 200 N, cycles: 1.2 million). After fatigue treatment, retentive strength of the crowns was evaluated by a crown pull-off test at a crosshead speed of 1 mm/min. Coefficient of thermal expansion (CTE) and modulus of elasticity (E-modulus) of each material were also analyzed to estimate the microscale expansion and contraction during TC and MC. TC and MC significantly reduced the retentive strength of the CAD/CAM resin-based crowns whereas that of the CAD/CAM ceramic crowns was only affected by TC. In addition, the resin-based crowns showed a higher number of crown loosening during TC than the ceramic crowns. Analyses of CTE and E-modulus indicated that the resin-based crowns would be more deformed during TC and MC than the ceramic crowns. The present study demonstrated that the resistance of crowns to microscale expansion and contraction caused by thermal and mechanical fatigue would play an important role in maintaining retentive strength.

Due to its light weight and high strength, carbon fiber reinforcement resin based composite (CFRC) has been widely used in aerospace, military, and many other industries. As the manufacturing technology develops, the geometry of CFRC components has seen significant changes, such as closed surface from the traditional open surface, or quite sophisticated topologies from simple shapes. As a result, fabrication of CFRC is confronted with challenging issues related to the design of fiber placement trajectory for optimal performance. In this paper, a trajectory generating algorithm is proposed based on the centroid curve of a quasi-rotational structure, where the centroid curve is the connection of centroids of the cross-sections of the structure. After the centroid curve of the component is achieved, the cross-section profiles perpendicular to the centroid curve can be determined. An efficient number of profiles are identified to avoid any overlap among neighboring profiles along the centroid curve. In this manner, the essential data for ultimate trajectory design are eventually obtained that can precisely reflect placement angles. The present work will effectively enhance the accuracy of trajectory of fiber placement and promote the mechanical property of CFRC components.

The aim of the present laboratory study was to mechanically characterize the interface between two dental resin-based composite (RBC) increments, and to investigate if elevated temperatures have an influence on the quality of the interface mimicking clinical filling procedure. Four RBCs (CLEARFIL MAJESTY™ Posterior, Kuraray (CMP)/Filtek™ Supreme XTE, 3M (FSX)/Grandio®SO, VOCO (GSO)/VisCalor® bulk, VOCO (VCB)) were tested with a fracture toughness test using Chevron notched beams (KI,CNB) at 23, 37 and 54 °C. KI,CNB specimens (3 × 4x25mm) with a V-shaped notch at the incremental interface were loaded until failure in a 4-point bending set-up. Failure modes were characterized using light microscopy, microstructural interface was analyzed using SEM. Statistical analysis was performed using Kolmogorov-Smirnoff test, two-way ANOVA and Tukey Post-Hoc test (p = 0.05). Mean KI,CNB ranged between 0.73 ±0.14 MPam0.5 (VCB, 23 °C) and 1.11 ± 0.11 MPam0.5 (FSX, 23 °C). The tested conventional highly filled RBCs presented fracture toughness at the incremental interface comparable to the cohesive strength of the bulk materials. VCB showed reduced interfacial fracture toughness at 23 and 37 °C, but performed well at elevated temperature of 54 °C.

Objectives To evaluate the effect of using a bulk-fill flowable base material on fracture strength and fracture patterns of root-filled maxillary premolars with MOD preparations restored with laminate restorations. Methods Fifty extracted maxillary premolars were selected for the study. Standardized MOD cavities with endodontic treatment were prepared for all teeth, except for intact control. The teeth were divided randomly into five groups (n = 10); (Group 1) sound teeth, (Group 2) unrestored teeth; (Group 3) MOD cavities with Vitrebond base and resin-based composite (Ceram. X One Universal); (Group 4) MOD cavities with 2 mm GIC base (Fuji IX GP) and resin-based composite (Ceram. X One Universal) open laminate, (Group 5) MOD cavities were restored with 4 mm of bulk-fill flowable base material (SDR) and resin-based composite (Ceram. X One Universal). All teeth were thermocycled and subjected to a 45° ramped oblique load in a universal testing machine. Fracture load and fracture patterns were recorded. Data were analyzed using one-way ANOVA and Dunnett’s T3 test. Results Restoration in general increased the fracture strength compared to unrestored teeth. The fracture strength of group 5 (bulk-fill) was significantly higher than the fracture strength of the GIC laminate groups and not significantly different from the intact teeth (355 ± 112N, P = 0.118). The type of failure was unfavorable for most of the groups, with the majority being mixed failures. Conclusions The use of a bulk-fill flowable base material significantly increased the fracture strength of extracted root-filled teeth with MOD cavities; however it did not improve fracture patterns to more favorable ones. Clinical significance Investigating restorative techniques that may improve the longevity of root-filled premolar teeth restored with direct resin restorations.

The jute fabrics reinforced unsaturated polyester resin (jute/UPR)-based composites were prepared successfully by the hand-lay-up technique. The percentage of jute fabrics was kept constant at 40% fiber (by weight). The disaccharide percentage was also kept constant at 2% (by weight), but at this percentage the mechanical properties were lower than the untreated composites. Gamma radiation dose was varied at 0, 2.5, 5 and 7.5 kGy for jute/UPR-based composites. At 5.0 kGy gamma dose highest TS, TM and Eb were obtained. The jute/UPR-based composites were treated under 30°C, 50°C and −18°C for the measurement of mechanical properties. At low temperature (−18°C), the highest mechanical properties were observed. The water uptake properties were measured for disaccharide-treated and disaccharide-untreated composites up to 10 days, but no water was absorbed by the composites. The soil degradation test was carried out under 12 inch soil containing at least 25% water, but no significant decrease was observ...

Objective: The study aimed to evaluate the potential of a commercial fiber reinforced resin composite (FRC) to be cured adequately also in increments larger than 2-mm. Material and methods: One FRC (EverX Posterior, GC) was investigated by assessing in real-time the degree of conversion (DC) and polymerisation kinetic at increasing depths (100-μm, 2-mm 4-mm and 6-mm). In addition, a battery of mechanical properties - flexural strength, flexural modulus, Vickers hardness, indentation modulus, creep – and the characteristics of the used curing light were determined. Results: One-way ANOVA revealed no significant difference in DC measured 300 s post-irradiation in a depth of 100-μm and 2-mm (p = 0.281). Similarly, no significant difference was identified between DC measured at 2-mm and 4-mm (p = 0.724), while the DC measured at 6-mm depth was significantly lowest (p0.95) by a double exponential sum function, distinguishing between the gel and the glass phase of the polymerization process. It allowed identifying a slower start of polymerization in depth, associated with a lower maximal rate of C-C double bond conversion. The mechanical properties amounted (128.30±8.38) MPa (flexural strength), (8.38±0.87) GPa (flexural modulus), (92.00±15.86) N/mm² (Vickers hardness), (17.82±1.82) GPa (indentation modulus) and (3.35±0.84) % for creep. Conclusions: While DC recorded in 2-mm and 4-mm depths were statistically similar, there is evidence that the quality of curing in a depth of 4-mm is lower compared to the top of the specimen. The mechanical properties were within the range of high viscosity bulk-fill resin-composites.

This study evaluated the effect of different adhesive protocols on the shear bond strength (SBS) of bulk-fill resin composite repaired with bulk-fill or conventional composite. Cylindrical bulk-fill resin composite specimens were prepared and allocated into groups according to the bonding strategy: no treatment, Silane+Scotch Bond Multipurpose (S+SBMP), Tetric N Bond Universal, and Single Bond Universal. Following bonding strategy, bulk-fill or conventional composite buildups were performed. After 24 h of storage in distilled water at 37°C, shear force was applied to the interface using a universal testing machine. The data were analyzed by two-way ANOVA and Tukey test (α=0.05). SBS was influenced by the bonding strategy and the composite used (p

Objectives: To measure temperature effects on stickiness and packability of representative resin-based composites and the effect of pre-heating time on pre-cure properties of Viscalor, including extrusion force. Methods: Five resin-based composites (RBC) and an additional RBC, Viscalor, used with a Caps Warmer (VOCO, Germany) were studied. The extrusion force (N) and extruded mass (g) were measured from Viscalor compules heated in T3 mode for 30 s (T3-30 s) and 3 min (T3-3 min). For stickiness and packability measurements, RBCs were packed into a brass cylindrical cavity controlled at 22 and 37 °C. A flat-ended probe was lowered into the RBC pastes at constant speed. Stickiness: Fmax (N) and Ws (N mm), and packability: Fp (N), were measured. Viscalor was LED photo-cured at 1200 mW/cm2 for 40 s. The degrees of conversion at 5 min and 24 h post cure (DC5min and DC24h) of Viscalor (no heat, T3-30 s and T3-3 min) were measured by ATR-FTIR. Data were analysed by one-way ANOVA, independent t-test and Tukey post-hoc tests (p < 0.05). Results: The maximum temperature of the Caps Warmer, in T3 mode, reached 68 °C in 20 min. Viscalor temperatures of 34.5 °C and 60.6 °C were recorded after 30 s and 3 min pre-heating, respectively. Pre-heating significantly reduced extrusion force and increased extruded mass, especially after 3 min. RBCs varied in Fmax, Ws and Fp (p < 0.05). Temperature also affected Fmax (p = 0.000), Ws (p = 0.002) and Fp (p = 0.000). Pre-heating Viscalor for either 30 s or 3 min did not increase the post-cure DC at either 5 min or 24 h, relative to no pre-heating (p > 0.05). Significance: The composites varied to an extent in stickiness and packability but the overall magnitudes remained within a clinically acceptable range. Pre-heating was beneficial in placement of Viscalor and caused no adverse effects through premature polymerization.

The purpose of this study is to analyze various surface grafting modifications of fiberglass-reinforced resin based composite piles. In addition, the effects of surface modifications of fiberglass-reinforced resin piles in terms of biosafety and mechanical strength were studied. According to different surface treatment methods, the fiberglass was divided into five groups (A-E): a blank control group, a KH570 processing group, a KH570 processing+Bis-GMA grafting 1 h group, a KH570 processing+Bis-GMA grafting 3 h group and a KH570 processing+Bis-GMA grafting 7 h group. All surface-treated materials were characterized using scanning electron microscope, thermogravimetric analyses and Fourier transform infrared spectrum and mechanical testing using a universal mechanical tester. The biosafety was evaluated by cell viability experiments and repeated oral toxicity tests and Ames tests. The Bis-GMA grafting modification further enhanced the mechanical properties of resin piles. By increasing the grafting time, the grafting effect and mechanical properties were further enhanced. The surfaces grafted for 7 h (Group E) remarkably improved the mechanical properties (flexural strength ~696.24 MPa; flexural load ~185.67N). The graft modifications improved the mechanical properties of fiber pile resin-based materials. The prolonged grafting time further improved the mechanical properties corresponding to enhanced grafting and the formation of a stable interface between fibers and the resin matrix. The surface-modified dental resin-based fiber did not show any signs of toxicity, cytotoxicity or mutagenicity, suggesting the potential biological safety of these materials in the clinical practice.

BACKGROUND Biodentine® is a bioactive calcium silicate-based material, with better strength parameters, an easier application method and a shorter setting time than mineral trioxide aggregate (MTA). The bond strength between Biodentine and the composite material is essential for the durability of the layered restoration. OBJECTIVES The objective of this study was to evaluate the bond strength of Biodentine to a resin-based composite at various acid etching times and with different adhesive strategies. MATERIAL AND METHODS In the 1st part of the experiment, the specimens were divided into 2 groups: the adhesive was applied in the total-etch (TE) and self-etch (SE) techniques. In the TE group, 37% orthophosphoric acid was applied after 30 s (TE 30) and 240 s (TE 240). In the SE group, the SE system was applied for 30 s (SE 30) and 240 s (SE 240). In the 2nd part, the SE systems Clearfil® SE Bond and Clearfil S3 Bond Plus were evaluated (the CSE and CS3 groups, respectively). In each group, the adhesive system was applied in 1 (the CSE 1 and CS3 1 subgroups) or 2 layers (the CSE 2 and CS3 2 subgroups). The specimens were subjected to a shear bond strength (SBS) test in a universal testing machine. RESULTS Shear bond strength was higher after a prolonged etching procedure in the TE (TE 30: 2.51 MPa, TE 240: 9.39 MPa) and SE techniques (SE 30: 5.92 MPa, SE 240: 7.89 MPa). A statistically significant influence was detected in relation to 30 s of surface preparation time for Clearfil S3 Bond Plus (p < 0.001). Greater bond strength was revealed after the application of 1 layer of the Clearfil S3 Bond Plus single-bottle system (CS3 1: 6.42 MPa). CONCLUSIONS The SBS of Biodentine to the composite depends on both the etching time and the mode of application of the adhesive systems. Higher bond strength was obtained for the SE adhesive in a shorter application time.

Objective The aim of this study was to investigate the influence of artificial aging on the mechanical properties and fracture patterns of novel CAD/CAM resin-based composite blocks (RCB). Methods Flexural strength and modulus of RCBs from seven manufacturers (Voco, Grandio Blocs, GB; Ivoclar Vivadent, Tetric®CAD, TC; DMG, Luxacam Composite, LC; Shofu Block HC, SF; 3M, Lava™ Ultimate, LU; GC, Cerasmart®, CS; Coltene, BRILLIANT Crios, CB) were assessed in a three-point-bending test after an aging process consisting of three sequential steps (14 days storage in artificial saliva, 10,000 thermo-cycles in distilled water between 5/55 °C, 48 h storage in ethanol 75%). Fracture origins were determined in a fractographic examination using reflected light stereomicroscopy combined with transillumination and scanning electron microscopy. Effects of aging were statistically analysed using one-way ANOVA with Tukey's HSD post hoc test (α = 0.05) and Weibull statistics. Correlations regarding filler amount were analysed using linear regression analysis. Results The strongest influence on the flexural modulus and strength was exerted based on the parameter material (p Fractography revealed four different fracture patterns with fracture origins from the corner, edge or sub-surface and a smooth fracture surface with non-identifiable fracture origin. Specimens with smooth fracture surface showed the significantly lowest flexural strength (p Conclusions Storage in artificial saliva mainly reduced the mechanical properties significantly while additional thermal aging mostly maintained the results. Aging in ethanol mostly maintained the results for flexural modulus but led to an increase in flexural strength values to the level of the unaged specimens. Fractographic analysis revealed a significant accumulation of sub-surface fracture origins after storage in ethanol arising from inherent flaws.

Due to the influence of the wall thickness, uneven heat transfer, and heat generation inside the resin during the molding of the composite material, the uneven temperature field distribution of the composite material is caused. This paper uses ABAQUS to perform finite element simulation on the temperature field of the forming process and obtains the distribution of the internal temperature field of the composite material. On the premise of obtaining the temperature field, through thermo-solid coupling simulation experiment, the influence of various factors on the entire curing process is compared. Based on the use of finite element simulation software, several comparative tests were carried out, and the residual stress problems in the curing process were verified by calling the stress and strain values of representative points. This article focuses on the analysis of temperature and energy data in heat transfer and 15 sets of stress-strain data under coupling action. On the premise of giving the reasons for each data, the accuracy and practicality of the data are analyzed.

The mechanical properties of dental resin-based composites (RBCs) are highly dependent on filler characteristics (size, content, geometry, composition). Most current commercial materials are marketed as "nanohybrids" (i.e. filler size1μm). In the present study, filler characteristics of a selection of RBCs were described, aiming at identifying correlations with physico-mechanical properties and testing the relevance of the current classification.Micron/sub-micron particles (or500nm) were isolated from 17 commercial RBCs and analyzed by laser diffractrometry and/or electron microscopy. Filler and silane content were evaluated by thermogravimetric analysis and a sedimentation technique. The flexural modulus (EAverage size for micron-sized fillers was almost always higher than 1μm. Ranges for mechanical properties were: 3.7EMechanical properties and filler characteristics significantly vary among modern RBCs and the current classification does not accurately illustrate either. Further, the chemical stability of RBCs differed, highlighting differences in resin and silane composition. Since E

Objective The aim of this study was to evaluate changes of color and fluorescence of resin based composite exposed to beer. Materials and Methods 84 samples (13 mm in diameter and 1.5 mm thick) of microhybrid composite Gradia DirectTM extra bleach white were immersed in 5 different beers (dark and light) or distilled water. Color and fluorescence were measured prior and after 1-, 7-, and 14-day immersion by Spectrophotometer Thermo Evolution 600 and Fluorolog-3-221 spectrofluorometer. Results Resin based composites changed color after immersion in beers of different types. Beers with higher optical absorption induced greater color changes. The fluorescence intensity of composites was decreased after immersion in beer, but the shape of fluorescence spectra was not changed. 14-day immersion in Bernard dark beer caused the greatest changes in optical properties of composite: ΔE*=9.0 and 57.6% reduced fluorescence. Conclusion Dark and light beers changed optical properties of resin based composite. The color change come exclusively from the change of chroma. Clinical Significance To fully meet esthetic criteria when using dental materials in restoration it is crucial to match optical properties of teeth and dental restoration at the moment of placement, but also to keep the match over the time. Considering that staining in beer causes changes in color and fluorescence of composites and that discoloration is a frequent reason for replacement of composite restorations, the data and conclusions on discoloration of dental restorations caused by beer consumption should aid dental professionals when reaching for high esthetics of modern dentistry.(J Esthet Restor Dent, 2016)

Resin-based composite molar crowns made by computer-aided design/computer-aided manufacturing (CAD/CAM) systems have been proposed as an inexpensive alternative to metal-ceramic or all-ceramic crowns. However, there is a lack of scientific information regarding fatigue resistance. This study aimed to analyze the fatigue behavior of CAD/CAM resin-based composite compared with lithium disilicate glass-ceramic. One-hundred and sixty bar-shaped specimens were fabricated using resin-based composite blocks [Lava Ultimate (LU); 3M/ESPE] and lithium disilicate glass-ceramic [IPS e.max press (EMP); Ivoclar/Vivadent]. The specimens were divided into four groups: no treatment (NT); thermal cycling (TC); mechanical cycling (MC); and thermal cycling followed by mechanical cycling (TCMC). Thermal cycling was performed by alternate immersion in water baths of 5°C and 55°C for 5 × 10(4) cycles. Mechanical cycling was performed in a three-point bending test, with a maximum load of 40 N, for 1.2 × 10(6) cycles. In addition, LU and EMP molar crowns were fabricated and subjected to fatigue treatments followed by load-to-failure testing. The flexural strength of LU was not severely reduced by the fatigue treatments. The fatigue treatments did not significantly affect the fracture resistance of LU molar crowns. The results demonstrate the potential of clinical application of CAD/CAM-generated resin-based composite molar crowns in terms of fatigue resistance.

Objective To determine the nanohardness and elastic moduli of two bulk-fill resin based composites (RBCs) at increasing depths from the surface and increasing distances laterally from the center after light curing. Methods Two bulk-fill dental RBCs: Tetric EvoCeram Bulk Fill (TECBF) and Filtek Bulk Fill Flowable (FBFF) were light cured in a metal mold with a 6 mm diameter and a 10 mm long semi-circular notch. The RBCs were photo-polymerized for 10 s using a light emitting diode (LED) Bluephase Style curing light, with the original light probe that lacked the homogenizer. This light has two blue light and one violet light LED emitters. By changing the probe orientation over the mold, the light output from only two LEDs reached the RBC. Measurements were made using: (i) the light from one violet and one blue LED, and (ii) the light from the two blue LEDs. Five specimens of each RBC were made using each LED orientation (total 20 specimens). Specimens were then stored in the dark at 37 °C for 24 h. Fifty indents were made using an Agilent G200 nanoindentor down to 4 mm from the surface and 2.5 mm right and left of the centerline. The results were analyzed (alpha = 0.05) using multiple paired-sample t-tests, ANOVA, Bonferroni post-hoc tests, and Pearson correlations. Results The elastic modulus and nanohardness varied according to the depth and the distance from the centerline. For TECBF, no significant difference was found between the spatial variations in the elastic modulus or hardness values when violet-blue or blue-blue LEDs were used. For FBFF, the elastic modulus and nanohardness on the side exposed to the violet emitter were significantly less than the side exposed to the blue emitter. A strong correlation between nanohardness and elastic modulus was found in all groups (r2 = 0.9512–0.9712). Significance Resin polymerization was not uniform throughout the RBC. The nanohardness and elastic modulus across two RBC materials were found to decline differently according to the orientation of the violet and blue light LED emitters within the curing light.

In some industrial application, thermal property of resin plays an important role as same as strength. Many attempts have been made to enhance the thermal conductivity of resin matrix composite. In this paper, the copper fibers were introduced to the polyimide-based composite. The experimental results showed that the thermal conductivity of polyimide-based composite with 15% Cu fibers was as high as 8.62W/mK which is more than three times that with Cu powders. The PI-Cu composites with copper fiber had a much lower wear loss than that with copper powder. The forming of three-dimensional network by Cu fibers makes it possible that the heat can conduct by electrons in the resin-based composite with Cu fibers.

The most essential and costly component of polymer electrolyte membrane fuel cells is the bipolar plate. The production of suitable composite bipolar plates for polymer electrolyte membrane fuel cell with good mechanical properties and high electrical conductivity is scientifically and technically very challenging. This paper reports the development of composite bipolar plates using exfoliated graphite, carbon black, and graphite powder in resole-typed phenol formaldehyde. The exfoliated graphite with maximum exfoliated volume of 570 ± 10 mL g−1 used in this study was prepared by microwave irradiation of chemically intercalated natural flake graphite in a few minutes. The composite plates were prepared by varying exfoliated graphite content from 10 to 35 wt.% in phenolic resin along with fixed weight percentage of carbon black (5 wt.%) and graphite powder (3 wt.%) by compression molding. The composite plates with filler weight percentage of 35/5/3/exfoliated graphite/carbon black/graphite powder offer in-plane and trough-plane electrical conductivities of 374.42 and 97.32 S cm−1, bulk density 1.58 g cm−3, compressive strength 70.43 MPa, flexural strength 61.82 MPa, storage modulus 10.25 GPa, microhardness 73.23 HV and water absorption 0.22%. Further, I–V characteristics notify that exfoliated graphite/carbon black/graphite powder/resin composite bipolar plates in unit fuel cell shows better cell performance compared exfoliated graphite/resin composite bipolar plates. The composite plates own desired mechanical properties with low bulk density, high electrical conductivity, and good thermal stability as per the U.S. department of energy targets at low filler concentration and can be used as bipolar plates for proton exchange membrane fuel cells.

Objective Bioactive glass (BAG) is known to possess antimicrobial and remineralizing properties; however, the use of BAG as a filler for resin based composite restorations to slow recurrent caries has not been studied. Accordingly, the objective of this study was to investigate the effect of adding 15 wt% BAG to a resin composite on bacterial biofilms penetrating into marginal gaps of simulated tooth fillings in vitro during cyclic mechanical loading. Methods Human molars were machined into approximately 3 mm thick disks of dentin and 1.5–2 mm deep composite restorations were placed. A narrow 15–20 micrometer wide dentin-composite gap was allowed to form along half of the margin by not applying dental adhesive to that region. Two different 72 wt% filled composites were used, one with 15 wt% BAG filler (15BAG) and the balance silanated strontium glass and one filled with aerosol silica and silanated strontium glass without BAG (0BAG—control). Samples of both groups had Streptococcus mutans biofilms grown on the surface and were tested inside a bioreactor for two weeks while subjected to periods of cyclic mechanical loading. After post-test biofilm viability was confirmed, each specimen was fixed in glutaraldehyde, gram positive stained, mounted in resin and cross-sectioned to reveal the gap profile. Depth of biofilm penetration for 0BAG and 15BAG was quantified as the fraction of gap depth. The data were compared using a Student's t -test. Results The average depth of bacterial penetration into the marginal gap for the 15BAG samples was significantly smaller (∼61%) in comparison to 0BAG, where 100% penetration was observed for all samples with the biofilm penetrating underneath of the restoration in some cases. Significance BAG containing resin dental composites reduce biofilm penetration into marginal gaps of simulated tooth restorations. This suggests BAG containing composites may have the potential to slow the development and propagation of secondary tooth decay at restoration margins.

Dental bulk-fill restorations with resin-composites (RBC) are increasing in popularity, but doubts concerning insufficient curing in depth still disconcert clinicians. An alternative might be offered by modern dual-cured RBCs, which additionally provide bioactive properties. This study assessed the impact of additional light-curing on polymerization kinetics, the degree of conversion (DC) and mechanical properties of a novel, dual-cured RBC with alkaline fillers. Since the bioactivity of a material often implies a release of compounds, the mechanical stability in simulated clinical environments was also evaluated. Polymerization kinetics and DC were assessed at 2- and 4-mm specimen depths in real-time up to one hour (

This study aimed to investigate the effects of hydrothermal aging, thermal cycling, and water storage on the mechanical properties of a machinable resin-based composite containing nano-zirconia fillers.A machinable resin-based composite containing nano-zirconia fillers (Lava Ultimate, LU) and a resin-based composite with a similar resin matrix-to-filler ratio but without zirconia fillers (Tetric N-Ceram, TNC) were prepared into bars and assigned into four groups based on the type of aging treatment (hydrothermal aging, thermal cycling, water storage, or no aging). The phase transformations of the zirconia fillers in LU after aging were evaluated by X-ray diffraction. The flexural strength, Weibull modulus, flexural modulus, and Vickers hardness of each group were investigated. The fracture surface morphologies of both resin-based composites before and after aging were observed by a scanning electron microscopy (SEM).Only Tetragonal zirconia was detected in the LU samples. Both before and after aging, the flexural strength, flexural modulus, and Vickers hardness values of LU were significantly higher than those of TNC (p 0.05) with the exception of the flexural modulus of LU, which showed no difference with that of TNC after water storage (p = 0.68). Hydrothermal aging, thermal cycling, and water storage had no significant effects on the surface Vickers hardnesses of LU or TNC (p 0.05). Hydrothermal aging significantly improved the flexural strength of LU (p = 0.00). Thermal cycling (p = 0.00) and water storage (p = 0.00) significantly decreased the flexural strength of LU. The flexural strength of TNC was not decreased by hydrothermal aging (p = 0.82) or water storage (p = 0.36), while it was decreased by thermal cycling (p = 0.00). The hydrothermal aging group of LU exhibited the highest Weibull modulus.The machinable resin-based composite containing nano-zirconia fillers provides superior flexural strength, flexural modulus, and Vickers hardness compared to the direct-filling resin-based composite with a similar resin matrix-to-filler ratio, although it fails to provide better aging resistance.

Aim: The objective of the present study was to evaluate the microshear bond strength (µSBS) of resin composite to Biodentine, which is a bioactive dentin substitute after aging periods using different adhesive systems.Material and Methods: One hundred and eighty cylindrical shaped blocks with a cavity of 5-mm in diameter and 2-mm in depth were fabricated from a self-cured acrylic. The Biodentine was mixed and loaded into the cavities. The prepared specimens were divided into 3 groups in accordance with aging periods (12-min; 24-h; 1-week). After the aging, each group was allocated to 6 subgroups: subgroup 1, no adhesive (control); subgroup 2, two-step etch-and-rinse adhesive; subgroup 3, two-step self-etch adhesive; subgroup 4, one-step self-etch adhesive; subgroup 5, universal adhesive in self-etch mode; subgroup 6, universal adhesive in etch-and-rinse mode. After adhesive application, resin composite cylinder was applied over Biodentine surface to assess µSBS. The µSBS was evaluated using a µSBS tester and failure modes were at 30× magnification. Statistical analyses were performed using two-way ANOVA and Tukey tests.Results: Biodentine shows lower µSBS at the 12-min. There were no considerable differences between 24-h and 1-week aging periods. Universal adhesive exhibited the highest bond strength values.Conclusion: Twenty-four hour waiting for the final restoration after the Biodentine placement could be useful to obtain better bond strength. In addition, highest µSBS values were detected for the universal adhesive irrespective to the application mode.

Aim The objective was to compare the marginal leakage (silver nitrate uptake) of nanohybrid resin-based composite (RBC) and two bulk-fill flowable RBCs with specific clinical protocols. Methods Four experimental groups of RBC were investigated including conventional composite Filtek™ Supreme in 2 mm increment (FS2), Filtek™ Supreme in 4 mm increment (FS4), Filtek™ Supreme Flowable (BFF), and SureFil® SDR® flow (SDR). Class II box preparation (4 × 4 × 3 mm) in extracted intact human molars was carried out and restored using the experimental groups, all according to the manufacturers’ recommendations except FS4. Samples were aged by thermocycling (2,000 cycles). Microleakage was calculated by measuring dye penetration in sectioned teeth using a stereomicroscope. Level of significance was set at P