Methacrylate-based Composites Research Articles

Investigating filler morphology and mechanical properties of new low-shrinkage resin composite types

Three types of low-shrinkage composites are today commercially available: Ormocers, cationic ring-opening curing systems and highly filled methacrylate-based materials, which cure via free-radical polymerization mechanisms. The aim of this study was to characterize the inorganic fraction of materials belonging to each type and to compare their mechanical properties. Two Ormocers (Admira and an experimental Ormocer V35694), one ring-opening composite (Filtek Silorane) and five methacrylate-based composites [Filtek Supreme XT, Tetric EvoCeram, Grandio, Synergy D6 (Coltène-Whaledent, Langenau, Germany) and an experimental material, V34930] were tested. Inorganic fillers were quantified by thermogravimetric analysis and morphologically characterized by scanning electron microscopy. Dynamic modulus was determined by an impulse excitation technique, static elastic moduli and flexural strength by a three-point bending method. The results were analyzed using ANOVA tests (P < 0.05) and linear correlations. Grandio, V34930 and V35694 exhibited significantly higher filler mass fractions. Both dynamic and static moduli of Grandio and V34930 were significantly higher than the other materials (P < 0.05), although no significant difference in flexural strength was observed between material type (P > 0.05). From the present findings, it was suggested that V35694 and Filtek Silorane exhibit comparable properties to conventional methacrylate-based composites, although clinically the cavity type and location must guide material choice. Under high occlusal load, the use of Grandio and V34930 might be favoured. For small cavities, alternative technologies could be preferred as the need for mechanical resistance is lower and the potential for stress generation is greater.

Polymerization shrinkage kinetics of silorane-based composites

Dental composites have improved significantly in physical properties over the past few decades. However, polymerization shrinkage and stress is still the major drawback of composites, limiting its use to selected cases. Much effort has been made to make low shrinking composites to overcome this issue and silorane-based composites have recently been introduced into the market. The aim of this study was to measure the volumetric polymerization shrinkage kinetics of a silorane-based composite and compare it with conventional methacrylate-based composites in order to evaluate its effectiveness in reducing polymerization shrinkage. Five commercial methacrylate-based (Beautifil, Z100, Z250, Z350 and Gradia X) and a silorane-based (P90) composites were investigated. The volumetric change of the composites during light polymerization was detected continuously as buoyancy change in distilled water by means of Archemedes' principle, using a newly made volume shrinkage measurement instrument. The null hypothesis was that there were no differences in polymerization shrinkage, peak polymerization shrinkage rate and peak shrinkage time between the silorane-based composite and methacrylate-based composites. The results were as follows: 1. The shrinkage of silorane-based (P90) composites was the lowest (1.48%), and that of Beautifil composite was the highest (2.80%). There were also significant differences between brands among the methacrylate-based composites. 2. Peak polymerization shrinkage rate was the lowest in P90 (0.13%/s) and the highest in Z100 (0.34%/s). 3. The time to reach peak shrinkage rate of the silorane-based composite (P90) was longer (6.7 s) than those of the methacrylate-based composites (2.4-3.1 s). 4. Peak shrinkage rate showed a strong positive correlation with the product of polymerization shrinkage and the inverse of peak shrinkage time (R = 0.95).

Microleakage evaluation of silorane based composite versus methacrylate based composite

Aim:Our study aimed to analyze the microleakage of silorane-based composite in comparison to two homologous methacrylate-based composites.Materials and Methods:Standardized class I cavities (4 × 2.5 × 3 mm) were prepared on extracted human premolars and randomly assigned into three groups (N = 15) as follows: Group A, Filtek P90 (silorane) with its dedicated adhesive system (P90 system adhesive); Group B, Adper SE Plus with Filtek Z250; Group C, Peak SE with Amelogen Plus. The teeth were subjected to thermocycling regime (200×, 5–55°C) and dye penetration of tooth sections were evaluated following 30 minute immersion in 2% Methylene Blue dye. Statistical analysis was performed with Kruskal-Wallis and Mann-Whitney U test at 95% significance level.Results:Silorane exhibited significantly decreased microleakage compared with any other resin based composite (RBC). The cavities restored with Amelogen Plus displayed nonsignificantly higher microleakage than with Filtek Z250.Conclusion:Although all of the restorative systems had microleakage, silorane technology showed less microleakage comparable to clinically successful methacrylate-based composite. This will improve the clinical performance and extend the composite durability.

A new method to measure the linear polymerization shrinkage of composites using a particle tracking method with computer vision

Since the introduction of restorative dental composites, their physical properties have been significantly improved. However, polymerization shrinkage is still a major drawback. Many efforts have been made to develop a low shrinking composite, and silorane-based composites have recently been introduced into the market. In addition, many different methods have been developed to measure the polymerization shrinkage. In this study, we developed a new method to measure the linear polymerization shrinkage of composites without direct contact to a specimen using a particle tracking method with computer vision. The shrinkage kinetics of a commercial silorane-based composite (P90) and two conventional methacrylate-based composites (Z250 and Z350) were investigated and compared. The results were as follows: 1. The linear shrinkage of composites was 0.33-1.41%. Shrinkage was lowest for the silorane-based (P90) composite, and highest for the flowable Z350 composite. 2. The new instrument was able to measure the true linear shrinkage of composites in real time without sensitivity to the specimen preparation and geometry. [J Kor Acad Cons Dent 35(3):180-187, 2010]

Does a low-shrinking composite induce less stress at the adhesive interface?

Objectives Polymerization shrinkage of a composite in a high configuration-factor (C-factor) cavity leads to polymerization shrinkage stress. In the prevention of high polymerization shrinkage stress, a low-shrinking silorane composite (Filtek Silorane, FS, 3M ESPE) was recently marketed. Therefore, we investigated the effect of C-factor (flat surface vs. class-I cavity) and different composite application protocols on the bonding effectiveness of a low-shrinking composite to human dentin. Methods A low-shrinking silorane-based composite (FS) and a conventional methacrylate-based composite (Filtek Z100, 3 M-ESPE) were bonded to standardized occlusal class-I cavities (4 mm × 4 mm × 2.5 mm) and to flat mid-coronal dentin surfaces using the two-step self-etch adhesive ‘Silorane System Adhesive’ (3 M-ESPE). Eight experimental groups were formed, according to the following treatment protocols: Z100 ‘flat’(1), Z100 ‘cavity’(2), FS ‘flat’(3), FS ‘flat/bulk-filled’(4), FS ‘cavity/bulk-filled’(5), FS ‘cavity/layered-filled’(6), FS ‘cavity/flowable cured’(7) and FS ‘cavity/flowable uncured’(8). For each group, at least 5 teeth were used. After 1 week of water storage, the teeth were sectioned to 1 mm × 1 mm (non-trimmed) sticks to measure the micro-tensile bond strength (μTBS). Results No statistical difference in μTBS was recorded between Z100 ‘flat’(1) and FS ‘flat’(3). Bonding to class-I cavity dentin lowered the μTBS in all groups, but this was only statistically significant for FS ‘cavity/bulk-filled’(5) and FS ‘cavity/flowable uncured’(8). Significance Using the two-step self-etch Silorane System Adhesive, the conventional composite Filtek Z100 and the low-shrinking composite Filtek Silorane bonded equally well to dentin. Bulk-filling with Filtek Silorane (FS ‘flat/bulk-filled’(4)) significantly decreased the μTBS, suggesting that factors other than polymerization shrinkage influenced the μTBS.

Oxygen inhibition and incremental layer bond strengths of resin composites

Objectives When dentists light cure resin composite restorations in increments or after contouring the surface layer to shape with a hand instrument the surface layer is exposed to air during polymerization. The presence of an oxygen inhibited resin surface layer may impact on clinical performance. Conflicting data has been produced in vitro regarding this topic. Methods To shed further light on this subject the current investigation assessed the thickness of the oxygen inhibited layer (OIL) and subsequent interfacial bond strength at various times post-cure of an “initial increment” for a range of experimental and commercial resin composites. The latter included conventional methacrylate-based composites and a novel low shrink Silorane resin chemistry product. Results A decrease in composite viscosity brought about by an increase in diluent monomer content in the matrix for the experimental composite formulations led to increase in OIL thickness. The OIL surface layer thickness for the commercial methacrylate-based RBC specimens cured in air were 19.2 ± 6.3 and 13.8 ± 5.3 μm, respectively and 9.0 ± 6.6 μm for Silorane. No test material exhibited a measurable OIL thickness polymerized in the nitrogen atmosphere. Significance From the current findings it may be concluded that incremental bond strength is not wholly reliant on surface inhibition since no differences in bond strength following immediate placement were observed between air and nitrogen atmosphere for any experimental or commercial material. For large restorations requiring multiple increments which are placed on fresh material, the bond strength between successive layers of Silorane should be no different to conventional methacrylate materials. Repair and bonding to aged Silorane restorations may be more problematic as inferior incremental bond strengths ensued when addition was delayed.

Are silorane compatible with methacrylate-based composites?

Are silorane compatible with methacrylate-based composites?

Macro, micro and nanomechanical investigations on silorane- and methacrylate-based composites

Macro, micro and nanomechanical investigations on silorane- and methacrylate-based composites

Macro-, micro- and nano-mechanical investigations on silorane and methacrylate-based composites

Objectives Cationic ring-opening monomers with a reduced shrinkage stress – silorane – are being used as matrix resins for recently introduced dental composites. Since shrinkage and mechanical properties are generally opposite properties, our study aimed to analyze the mechanical behavior of the silorane-based composite in comparison to six homologous clinical successful methacrylate-based composites. Methods Mechanical properties were determined at macro- (strength and modulus of elasticity), micro- (hardness, modulus of elasticity and creep) and nano-scale (nano-dynamic-mechanical parameters: complex, storage, loss modulus and tan δ) after storing the materials for 24 h in distilled water as well as after aging (thermocycling and storing for 4 weeks in water, saliva or alcohol). Results The strongest influence on the mechanical properties at macroscopic scale was exerted by the storage media although the influence of the material was also significant. At micro- and nano-scale, the material itself influenced the mechanical properties stronger than the storage. By comparing the four storage conditions, a multivariate analysis revealed a significant decrease in all measured mechanical properties by storing for 4 weeks in water, saliva or alcohol, when compared to the 24 h storage. The strongest effect was exerted through the alcohol storage, whereas the effect of storing for 4 weeks in water or saliva was comparable. The nano-composites were more degraded by a 4-week storage in water and saliva than the micro-hydrids, whereas the effect of storing in alcohol was material depended. The tested silorane-based composite revealed good mechanical properties. The material was very stable in all applied solvents and more reliable by storing in alcohol solutions than the measured methacrylate-based composites. Significance From the point of view of the mechanical properties measured at macro-, micro- and nano-scale, the silorane-based composite was comparable to clinically successful methacrylate-based composite materials, encouraging the clinical use of the new composite material.

Effects of food-simulating liquids on the mechanical properties of a silorane-based dental composite

The purpose of this study was to investigate the effects of food-simulating liquids (FSL) on the hardness and flexural strength (FS) of a new silorane-based composite and to compare it with methacrylate-based composites (MBCs). Four restorative materials (Filtek Silorane, P60, Z250, and Supreme XT) were used. Specimens for the FS and hardness measurements were fabricated in customized molds. Immediately after polymerization, the materials were stored in the following dietary simulating solvents at 37 degrees C for 1 week: distilled water, 0.02 N citric acid, heptane, and 75% aqueous ethanol solution. After conditioning, the FS and hardness values were measured. Data were subjected to ANOVA/Scheffé's test at a significance level of 0.05. The hardness and FS of Filtek Silorane were not significantly affected by FSL (p>0.05). Conversely, the hardness of MBCs significantly decreased after conditioning in water and ethanol (p<0.05). Similarly, the FS values of MBCs were significantly affected after conditioning in ethanol.

Effects of plasma treatment on the shear bond strength between fiber-reinforced composite posts and resin composite for core build-up

The aim of this study was to evaluate the effects of plasma treatment on adhesion between fiber-reinforced posts and a composite core material. Two types of posts, methacrylate-based (FRC Postec) and epoxy resin-based (DT Light-Post), were treated with oxygen plasma (O(2)), argon plasma (Ar), nitrogen plasma (N(2)), or helium mixed with nitrogen plasma (He+N(2)) using a radio-frequency generator before bonding to a methacrylate-based composite. Pull-out tests were performed using a universal testing machine. Surface roughness of each group was evaluated using a profilometer. On tensile-shear bond strength, statistical analysis revealed that the type of post, type of plasma treatment, and their interaction significantly influenced the results (p<0.05). Tukey's test revealed significant differences in tensile-shear bond strength between the control and other plasma treatment groups (p<0.05). On surface roughness, Tukey's test revealed significant differences between the control group and the Ar group (p<0.05) with DT Light Post. Plasma treatment appeared to increase the tensile-shear bond strength between post and composite.

New Matrix Polymers for Photo-activated Resin Composites using Di-.ALPHA.-fluoroacrylic Acid Derivatives

A novel matrix resin for photo-activated resin composites was developed using alpha-fluoroacrylic acid derivatives. To render resin composites with improved mechanical properties, silica fillers were also used. It was found that the newly developed fluorine-substituted monomer was polymerized quite easily not only by free radical chemical initiators, but also by photoirradiation using free radical photoinitiator system. In particular, the photopolymerization rate of the novel monomer was more than two times faster than that of corresponding methacrylate-based monomer. Composite based on the newly developed matrix resin had higher micro-Vickers hardness and compressive strength values than the methacrylate-based composite, and that it contained only trace residual monomers compared with the methacrylate-based material. The high polymerization conversion of the fluorine-substituted monomer could be attributed to the polar effect or the small steric hindrance of fluorine at the alpha-position.

Evaluation of Shear Bond Strength of Fiber-reinforced Composite and Methacrylate-based Composite to Pure Tricalcium-based Cement

ABSTRACT Aim Fracture of restorative composite is reported as a common reason for replacement. Due to failures of this kind, it is still controversial whether restorative composites should be used in large, high-stress-bearing applications, such as in direct posterior restorations. The high brittleness of current composites hinders their use in large stress-bearing areas. Thus, recently short fiber-reinforced composite was introduced as dental restorative composite resin. The aim of the article is to evaluate shear bond strength of fiber-reinforced composite (everX Posterior) and methacrylate-based composite (FILTEK Z250) to pure tricalcium silicate-based cement (biodentine). Materials and methods Acrylic blocks (n = 30) with 2 mm high and 5 mm diameter central holes were prepared. The samples were taken and filled with biodentine and were divided into two groups containing 15 in each group. Group I: Fiber-reinforced composite. Group II: Methacrylate-based composite, which are layered over biodentine. The specimens are transferred to the universal testing machine and subjected to shear bond strength analysis at a cross-head speed of 1.0 mm/minute. Results The bond strength values were significantly higher in case of fiber-reinforced composite when compared with methacrylate-based composite. Conclusion Within the limitations of the study, it was concluded that the fiber-reinforced composite with biodentine had highest bond strength when compared with methacrylate-based composite. Clinical significance Fiber-reinforced composite has excellent fatigue resistance because the embedded fibers are bonded to the polymer matrix and allow the stresses to be distributed effectively throughout the restoration. They are most suitable for applications in which the direction of highest stress is predictable. They are used in cavities with three or more surfaces missing and also in large-sized cavities. They are extensively used in cavities where inlays and onlays are prescribed. How to cite this article Reddy RA, Basavanna RS. Evaluation of Shear Bond Strength of Fiber-reinforced Composite and Methacrylate-based Composite to Pure Tricalcium-based Cement. CODS J Dent 2016;8(1):25-27.

Polymerization of photocurable commercial dental methacrylate-based composites

Due to their excellent aesthetics, photopolymers have been extensively used in several dentistry applications. However, several problems are reported, e.g. low mechanical and abrasion resistance, shrinkage during polymerization, etc. Properties of the final restorations are intrinsically related to the polymerization stage, which can be conveniently studied by photocalorimetry. In the present work the polymerization reaction and the filler content of different photocurable commercial dental methacrylate-based composites were studied by means of photocalorimetry and thermogravimetry, respectively. The results show that the values of curing rate, the heat of polymerization and the filler content vary significantly from one composite to another.

The Noise in Measurements of Degree of Conversion of (Meth)Acrylates by FTIR-ATR

Noise frequently appears on FTIR-ATR spectra of a cured (meth)acrylic material during determination of its double bond conversion. The goals of this work were to investigate the source of the noise and to find an effective way to reduce it. Two methacrylate-based dental composites, one unfilled methacrylate resin blend, and one acrylate resin system were used as the materials to be tested. Uncured and visible light cured specimens were mounted on an FTIR-ATR and their IR spectra were taken. The characteristics of the spectra were analyzed along with those of other solids and liquids. It was found that the origin of the noise is IR absorption bands of water adsorbed on the surface of the solid specimens. Among several remedies, digital subtraction of the water absorption baseline is demonstrated to be a flexible, easy-to-implement, and time-saving method to reduce or even eliminate the noise of the sample spectrum. Noise reduction improves the quality of FTIR-ATR spectra and makes the measurement of double bond conversion more accurate.

Silorane-based Dental Composite: Behavior and Abilities

The purpose of this study was to examine the characteristics of an innovative composite material for dental restorations based on silorane--a monomer with a new chemical composition, and thereby compare the examined characteristics against those of well-known methacrylate-based composites. Degree of conversion at 2-mm and 6-mm depths as well as hardness, modulus of elasticity, and creep resistance through the middle of 6-mm high samples were measured. It was observed that up to 20 minutes after curing, curing time--and not irradiance--played the determinant role for a high degree of cure. No differences were registered between the two categories of material in terms of hardness. However, modulus of elasticity of the silorane-based material was slightly lower and the creep resistance higher than a methacrylate composite (Tetric EvoCeram). In conclusion, siloranes exhibited good mechanical properties comparable to those of clinically successful methacrylate-based composite materials.

Low shrinkage light curable nanocomposite for dental restorative material

The aim of this study was to develop a low shrinkage visible light curable nanocomposite dental restorative material without sacrificing the other properties of conventional materials. This nanocomposite was developed by using an epoxy resin 3,4-epoxycyclohexylmethyl-(3,4-epoxy)cyclohexane carboxylate (ERL4221) matrix with 55% wt of 70-100 nm nanosilica fillers through ring-opening polymerization. GPS (gamma-glycidoxypropyl trimethoxysilane) was used to modify the surfaces of silica nanoparticles. The nanocomposite was shown to exhibit low polymerization shrinkage strain, which is only a quarter of currently used methacrylate-based composites. It also exhibited a low thermal expansion coefficient of 49.8 microm/m degrees C which is comparable to that of the methacrylate based composites (51.2 microm/m degrees C). The strong interfacial interactions between the resin and fillers at nanoscales were demonstrated by an observed high strength and high thermal stability of the nanocomposite. A microhardness of 62 KHN and a tensile strength of 47 MPa were reached. A high degree of conversion ( approximately 70%) can be obtained after less than 60 s of irradiation upon the nanocomposite. A transmission electron microscope (TEM) study of the nanocomposite showed no aggregation of fillers. Comparable results to the methacrylate based composites were obtained from the one day MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) cytotoxicity test. The developed epoxy resin based nanocomposite demonstrated low shrinkage and high strength and is suitable for dental restorative material applications.

Field amplified stacking injection--capillary electrophoresis for quantitative analysis of released methacrylic acid from dental composites.

Field-amplified stacking injection-capillary electrophoresis (FASI-CE) applied for the first time to the study of dental materials is demonstrated in this report. CE was used to separate methacrylic acid from the other degraded components. Due to the background electrolyte being weakly basic and methacrylic acid being negatively charged, in-capillary enrichment of the analyte was achieved by FASI. A detection limit of less than 50 ppb was obtained with good reproducibility (relative standard deviation < 3%). The method was applied to the analysis of four commercially available dental composites. Results showed that FASI-CE was effective in monitoring the fabrication process and product quality of restorative materials fabricated from methacrylate-based composites by analyzing the amount of methacrylic acid released from the residual methacrylate monomers.

Principal component analysis and cluster analysis for the characterization of dental composites.

Various experimental dental materials were characterized using chemometric methods. The main aim of the study was to ascertain which composite materials present the best properties for use in restorative dentistry. Bisphenol-alpha-glycidyl methacrylate-based composites containing hydroxyapatite as a filler and a coupling agent were prepared using a photocuring polymerization procedure. Several chemical and mechanical properties of experimental composites were measured and the corresponding data were further studied using principal component analysis and cluster analysis. Results from the characterization allowed the most appropriate materials to be selected. Various composites presented acceptable general properties suggesting their suitability as substitutes for commercial materials in dentistry.

5527130 Environmentally safe underground piping system: Webb Michael C, Chester Springs, PA, United States assigned to Environ Products Inc

Polymerization shrinkage of a composite in a high configuration-factor (C-factor) cavity leads to polymerization shrinkage stress. In the prevention of high polymerization shrinkage stress, a low-shrinking silorane composite (Filtek Silorane, FS, 3M ESPE) was recently marketed. Therefore, we investigated the effect of C-factor (flat surface vs. class-I cavity) and different composite application protocols on the bonding effectiveness of a low-shrinking composite to human dentin.A low-shrinking silorane-based composite (FS) and a conventional methacrylate-based composite (Filtek Z100, 3 M-ESPE) were bonded to standardized occlusal class-I cavities (4 mm × 4 mm × 2.5 mm) and to flat mid-coronal dentin surfaces using the two-step self-etch adhesive ‘Silorane System Adhesive’ (3 M-ESPE). Eight experimental groups were formed, according to the following treatment protocols: Z100 ‘flat’(1), Z100 ‘cavity’(2), FS ‘flat’(3), FS ‘flat/bulk-filled’(4), FS ‘cavity/bulk-filled’(5), FS ‘cavity/layered-filled’(6), FS ‘cavity/flowable cured’(7) and FS ‘cavity/flowable uncured’(8). For each group, at least 5 teeth were used. After 1 week of water storage, the teeth were sectioned to 1 mm × 1 mm (non-trimmed) sticks to measure the micro-tensile bond strength (μTBS).No statistical difference in μTBS was recorded between Z100 ‘flat’(1) and FS ‘flat’(3). Bonding to class-I cavity dentin lowered the μTBS in all groups, but this was only statistically significant for FS ‘cavity/bulk-filled’(5) and FS ‘cavity/flowable uncured’(8).Using the two-step self-etch Silorane System Adhesive, the conventional composite Filtek Z100 and the low-shrinking composite Filtek Silorane bonded equally well to dentin. Bulk-filling with Filtek Silorane (FS ‘flat/bulk-filled’(4)) significantly decreased the μTBS, suggesting that factors other than polymerization shrinkage influenced the μTBS.