Synthesis and characterization of N-isopropyl, N-methacryloxyethyl methacrylamide as a possible dental resin

In this study, N-isopropyl, N-methacryloxyethyl methacrylamide (NIMM) is proposed as a possible reactive diluent in place of triethylene glycol dimethacrylate (TEGDMA) for dental resin mixtures. Real-time infrared spectroscopy was used to monitor the double-bond conversion as a function of irradiation time, and mixtures of 50/50wt% bis-GMA/NIMM were found to reach final conversions (95%) that were 1.5 times greater than bis-GMA/TEGDMA (65%) under visible light irradiation. In addition, samples cured to these conversions were tested with dynamic mechanical analysis. The bis-GMA/NIMM mixture (100% converted) was found to have a higher glass transition temperature and modulus at body temperature than a comparable bis-GMA/TEGDMA mixture (60% converted). Finally, the water sorption and solubility of bis-GMA/NIMM were determined to be higher than the bisGMA/TEGDMA comparison, but the values were still within the range of the ISO 9000s standard. These results suggest that bis-GMA/NIMM mixtures are a viable alternative to conventional dental resins since a greater degree of monomer conversion is obtainable without sacrificing physical and mechanical properties.     

Synthesis and photopolymerization of N,N'-dimethyl,-N,N'-di(methacryloxy ethyl)-1,6-hexanediamine as a polymerizable amine coinitiator for dental restorations.

N,N'-dimethyl,-N,N'-di(methacryloxy ethyl)-1,6-hexanediamine (NDMH) was synthesized for the purpose of replacing both triethylene glycol dimethacrylate (TEGDMA) and the non-polymerizable amine which is added as a coinitiator in dental resin mixtures, 2,2-bis[4(2-hydroxy-3-methacryloxypropoxy)phenyl] propane (bis-GMA), camphorquinone (CQ) and ethyl-4-dimethylaminobenzoate (EDAB) were used as monomer, photoinitiator and coinitiator, respectively, in these model dental resin systems. Mixtures of bis-GMA/TEGDMA/CQ/EDAB and bis-GMA/TEGDMA/CQ/NDMH were found to reach final conversions of about 45%, slightly higher than his-GMA/NDMH/CQ (40%) under comparable visible light irradiation conditions. In addition, samples cured to these conversions were tested with dynamic mechanical analysis. The bis-GMA/TEGDMA/CQ/EDAB, his-GMA/TEGDMA/CQ/NDMH and bis-GMA/NDMH/CQ mixtures were found to have approximately the same glass transition temperature and modulus. Finally, the water sorption and solubility of bis-GMA/NDMH/CQ were higher than those of the bis-GMA/TEGDMA/CQ/EDAB, and bis-GMA/TEGDMA/CQ/NDMH. However, the values were still within the range of the ISO 9000's standards. These results suggest that NDMH is a viable alternative to conventional photocuring dental resins, serving both as a diluent and coinitiator, since there are no large differences in physical and mechanical properties when using NDMH to replace the amine coinitiator and TEGDMA diluent. The key advantage to this system is that the dimethacrylate NDMH can copolymerize with bis-GMA and TEGDMA, limiting the amount of extractable amine.     

Mechanical and antibacterial properties of benzothiazole-based dental resin materials

A synthesized benzothiazole containing mono-methacrylate monomer BTTMA was incorporated into Bis-GMA/TEGDMA dental resin system with a series of mass concentration from 5 to 30 wt.% as an antibacterial agent. The influence of BTTMA on physicochemical properties of dental resin system, such as double bond conversion (DC), volumetric shrinkage (VS), flexural strength (FS) and modulus (FM), water sorption (WS) and solubility (SL) were investigated. Direct contact testing and agar diffusion testing were used to evaluate the antibacterial activity of BTTMA containing dental resin. The results showed that BTTMA could endow dental resin with significant antibacterial activity when its concentration reached a certain amount (20 wt.%), and the antibacterial activity of BTTMA containing dental resin was mainly attributed to the immobilized BTTMA instead of the unreacted leachable BTTMA. BTTMA had no negative effect on physicochemical properties of dental resin, and even some BTTMA containing dental resins had advantages like higher DC, lower VS and WS when compared with control resin. Therefore, BTTMA could be considered as a suitable antibacterial agent in dental material, but much more researches concerned about biocompatibility should be done in future to prove whether it could be applied in clinic.     

Dynamic mechanical thermal analysis of dental polymers. II. Bis-phenol A-related resins

Dynamic mechanical analysis of bis-phenol A-related resins for dental usage provided loss tangent maxima at their transitions and an Arrhenius-type dependence of transition temperature and frequency. A constant maximum in the loss tangent curves, over the frequency range for the unfilled resins below their glass transition temperature, was thought to be caused by their high degree of unsaturation. The calculated activation energies showed the polycarbonate denture base resin required considerably greater energy for segmental motion than the other tested materials. In contrast, the ethylene imine-based temporary crown and bridge material exhibited the lowest activation energy.     

复合树脂充填材料修复牙体缺损的应用价值及临床评价

背景：各种复合树脂充填材料已成为牙体缺损修复治疗必不可少的重要材料,与合金修复材料并驾齐驱,但目前复合树脂的耐磨性能尚不够理想。 目的：就近年来研究应用的各种复合树脂充填材料的特点进行总结及对比,为牙体缺损的生物材料和组织工程修补手段提供理论基础。 方法：由第一作者于2010-12应用计算机检索PubMed数据库、万方数据库和维普数据库有关口腔复合树脂材料修复牙体缺损的文献。英文资料的检索时间为1999-01/2010-12,中文资料的检索时间为2000/2010-10;英文检索词为“composite resin,visible-light cured dental,detal adhesive materials,compatibility”,中文检索词为“复合树脂,口腔充填材料,固化性能,生物相容性,口腔修复,纳米材料”。排除较陈旧文献及重复研究。阅读标题和摘要进行筛选,共纳入28篇进行分析。 结果与结论：复合树脂是有机树脂基质经过表面处理的无机填料以及引发体系组合而成的牙体修复材料,作为牙色充填材料,具有可接受的物理机械性能,美观以及操作方便、易于修补等优点,在口腔修复领域使用越来越广泛。但复合树脂也存在聚合收缩、不耐磨、变色等缺点,尤其是其耐磨性能的不足,可导致修复物表面体积减小,以及修复体和边缘的破坏。随着纳米技术在生物医学领域的发展,复合树脂的纳米技术极大地丰富了口腔材料科学的研究领域,有望在牙齿修补领域带来更好的应用前景。     

Mechanical properties of four methylmethacrylate-based resins for provisional fixed restorations

The use of a provisional restoration is an important phase in the treatment of the dental prosthetic patient. A good provisional restoration should satisfy the following requirements: pulpal protection, positional stability, ease in cleaning, accurate margins, wear resistance, dimensional stability, and serve as a diagnostic aid in treatment assessment and esthetics. There is a tendency for discoloration, occlusal wear, and fracture that eventually leads to unnecessary repair. Heat-processed and reinforced methacrylate-based resins have been used to improve the mechanical and physical properties of provisional restorations. Among various improvements, the interpenetrating network crosslinked PMMA (IPN) has been shown to have superior mechanical properties if manufactured through a dough compression molding process at 130 degrees C. However, there have been no published data that relate with the use of this material for fixed provisional restorations.The objective of this study was to compare four methyl methacrylate-based resins for provisional crowns and bridges with varying processing cycles, including JET [self-cure], ACRALON [heat-cured], titanium dioxide filled PMMA [heat-cured], and IPN [heat-cured denture tooth resin]. Properties studied included transverse strength, toughness, rigidity, and hardness. From the results of this study the following conclusions can be made: the IPN group may have had a lower degree of conversion as demonstrated by decreased strength, toughness, and hardness data as compared with Acralon. Increasing the polymerization cycle of unmodified Acralon resin causes a significant increase in strength.     

Phthalonitrile Blends: Simple Way to Improve Physical Properties by Increasing Crosslinking Density

A method to improve the mechanical properties of phthalonitrile (PN) resins at lower postcure temperatures is achieved by blending a second‐generation oligomeric aromatic ether ketone‐based PN resin with 1,1,1‐tris‐[4‐(3,4‐dicyanophenoxy)phenyl]ethane in varying concentrations. Most of the mixtures exhibit a single softening temperature indicating that the two resins are miscibile in one another at the respective concentrations. After various blends are thermally cured to several postcure temperatures yielding crosslinked polymers, the polymers demonstrate superb mechanical properties and thermooxidative stability at lower overall postcure temperatures.     

A new resin matrix for dental composite having low volumetric shrinkage

The applications of dental restorative composite resins containing 2,2 bis [4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA), as a base resin, and triethylene glycol dimethacrylate (TEGDMA), as a diluent, are often limited in dentistry due to the relatively large amount of volumetric shrinkage that occurs during the curing reaction. In this study, various new resin matrices were examined for use as dental composites in order to reduce the amount of volumetric shrinkage that occurs in dental composites as a result of curing. Bis-GMA derivatives were synthesized by substituting methyl groups for hydrogen on the phenyl ring. The derivatives of TEGDMA with different chain lengths or reactive groups were also examined. The molecular structural changes in the TEGDMA derivatives were not effective in reducing the level of volumetric shrinkage. The resin matrix containing a Bis-GMA derivative and TEGDMA showed a reduced amount of volumetric shrinkage in proportion to the number of methyl groups on the phenyl rings. Polymerization with a mixture of Bis-GMA, its derivatives and a diluent is a promising strategy for obtaining a polymer with a low amount of volumetric shrinkage. A comparison of the volumetric shrinkage of dental composites containing Bis-GMA, TMBis-GMA (2,2-bis[3,5-dimethyl, 4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane)), and TEGDMA with that prepared from a Bis-GMA and TEGDMA mixture showed that the volumetric shrinkage reduction in the new resin was approximately 50%. Furthermore, the mechanical strength of the former was higher than that of the latter.     

The influence of postcuring on the fracture properties of photo-cured dimethacrylate based dental composite resin

The dependence of the fracture behavior of photocured dimethacrylate-based composite resins on the matrix crosslink density (varied by postcuring at various temperatures) was investigated. In general, the fracture toughness (KIc) was increased by postcuring as has been observed for epoxy-amine networks. The flexural and diametral tensile strength was also raised by postcuring. Calculation of the inherent flaw size (ao) from these properties produced conflicting dependencies on the state of cure. It is suggested that improved wear resistance and incisal edge strength of dental composite resin restoratives may be achieved by increased degree of cure.     

Development of highly reactive mono-(meth)acrylates as reactive diluents for dimethacrylate-based dental resin systems

Reactive diluents such as triethyleneglycol-dimethacrylate (TEGDMA) have been widely used with bisphenol-A-glycidyl-dimethacrylate (Bis-GMA) to achieve restorative resins with appropriate viscosity and higher conversion. However, additional water sorption and polymerization shrinkage were also introduced. The aim of this work is to investigate whether the cure and material properties can be improved in dental resins containing novel mono-(meth)acrylates as reactive diluents so that these Bis-GMA-based copolymers have reduced polymerization shrinkage but higher overall double bond conversion. Several ultra-high-reactivity mono-(meth)acrylates that contain secondary functionalities have been synthesized and investigated. The polymerization rate and double bond conversion were monitored using photo-FTIR. Polymerization shrinkage, dynamic mechanical analysis, and flexural strength were characterized. Compared with the Bis-GMA/TEGDMA control, the Bis-GMA/mono-methacrylate systems studied showed higher final conversions, faster curing rates, and decreased polymerization shrinkage. Our optimum system Bis-GMA/morpholine carbamate methacrylate achieved 86% final conversion (vs. 65%), a polymerization rate 3.5 times faster, and a 30% reduction in polymerization volumetric shrinkage. These results indicate that certain highly reactive, novel mono-(meth)acrylates possess very promising potential to replace TEGDMA as reactive diluents and can readily be applied to develop superior dental resins.     

Work of fracture of a composite resin: fracture-toughening mechanisms

The aim of this work was to investigate those mechanical parameters able to describe the fracture behavior of dental composite resins. A commercially available fine-particle micro-hybrid resin composite was used. Classical parameters as Young's modulus, strength distribution, and critical stress intensity factor were considered. Strength values were determined using the diametrical compression of discs test and for the critical stress intensity factor both unstable and controlled fracture tests were used. Controlled fracture tests allowed determining the work of fracture. Microstructure was studied by optical and field emission scanning electron microscopy. The obtained properties have been Young's modulus, 17.7 +/- 0.6 GPa; Weibull modulus, m = 14 (upper and lower limits for 90% confidence: 17 and 10); characteristic strength 51 MPa (upper and lower limits for 90% confidence: 53 and 49 MPa); critical stress intensity factor in mode I, K(IC) = 1.3 +/- 0.1 and work of fracture, gamma(wof) = 8-9 J/m(2). Pores and bubbles formed during the packing of the composite were identified as critical defects in the tested specimens. Crack deflection and branching have been identified as toughening mechanisms. Classical mechanical parameters (Young's modulus, hardness...) are not able to efficiently predict the major clinical failure mode of composite resins by fatigue. Work of fracture analysis, which is dependant on microstructural parameters such as particle size and shape, have to be included when testing mechanical properties of dental composite resins in future research studies.     

Combinatorial investigation of the structure-properties characterization of photopolymerized dimethacrylate networks

The effects of co-monomer composition and irradiation time in a model two-component dimethacrylate dental resin blend were evaluated using combinatorial methods to determine the degree of methacrylate conversion and resulting mechanical properties. 2-Dimensional gradient samples varying in monomer composition and light exposure time were fabricated. The conversion was measured using near infrared spectroscopy (NIR) and the mechanical properties (i.e., hardness and elastic modulus) were determined using nanoindentation via the continuous stiffness method. An excellent correlation was observed between the reaction conversion and mechanical properties for the cross-linked networks. The methacrylate conversion ranged from 40% to 85% and the mechanical properties increased over two orders of magnitude over this conversion range. The ultimate reaction conversion and mechanical properties depended on both the co-monomer composition and cure time.     

Synthesis of strongly basic anion exchange resins based on glycidyl methacrylate‐ethylene glycol dimethacrylate copolymer. Effect of amount and nature of diluent,and the degree of crosslinkage on the resins properties

A number of hydrophilic copolymers based on glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDM) were synthesized using the technique of suspension polymerization. A number of diluents such as dimethylpthalate (DMT), diethylpthalate (DET), dibutylpthalate (DBT) and bis‐2‐ethylhexylpthalate (diocylphthalate, DOT) were used. The resulting polymers were modified into strongly basic anion exchange resins using 50% aqueous trimethylamin hydrochloride solution. In this study, the effects of amount and nature of diluents on resin properties, i. e. porosity, density, mechanical properties and capacities, were investigated. The effect of amount of crosslinking agent, i.e. the amount of EGDM, was also studied. It was found that resin become porous as the number of methylene groups in diluents increases. The pore volume changes from 0.05 to 1.35 ml/g as the diluent change from DMT to DOT. The mechanical strength of the resin decreases on increasing the number of methylene groups in the diluent. However, the chloride capacity shows no significant change. By varying the amount of crosslinking agent (from 10 to 50%) the chloride capacity changes from 3.46 to 1.2 meq/g, respectively. The effect of crosslinking on porosity was also investigated. It was found that porosity of the resin increases on increasing the amount of EGDM. This is the first time that strongly basic anion exchange resin based on GMA‐co‐EGDM using different and varying amounts of diluents, as well as various degrees of crosslinkage, were synthesized and characterized. The important aspect of this study is that it provides a guideline for the synthesis of a resin with specific properties by selection of a diluent and varying its ratio with respect to the monomer.     

Effect of temperature and ageing on the mechanical properties of dental polymeric composite materials

Evaluation of the mechanical properties of some dental composite materials, Compact, Finesse and Prisma-Fil based on bisphenol glycidyl methacrylate resin was undertaken by applying compression, tension and hardness tests. The effects of temperature and ageing times on these properties were studied. There was a marked increase in the mechanical properties (compressive strength, diametral tensile strength, compressive elastic modulus and hardness) for all the investigated composites with increase of both temperature and time. This was explained in terms of the influence of temperature on the polymerization rate of the materials. The improvement in the mechanical properties of the samples, kept at 37 degrees C, was attributed to further and continued polymerization of the polymer content of their resin system. Such mechanical improvement was verified by the regression equation of linearity versus both temperature and time.     

Mechanical properties of BIS-GMA resin short glass fiber composites

The use of short glass fibers as a filler for dental restorations or cement resins have not been examined extensively. The mechanical properties and untreated glass fibers (5 microns dia x 25 microns) in Bis-phenol A glycidyl methacrylate (BIS-GMA) diluted with triethylene-glycol dimethacrylate (TEGDMA) resin were investigated for possible use as a restorative dental composite or bone cement. Compression, uniaxial tension and fracture toughness tests were conducted for each filler composite mixtures of 40, 50, 60 and 70%. Set time and maximum temperature of polymerization were determined. The results show that the elastic modulus, tensile strength and compressive strength are dependent on the percent of filler content. Elastic modulus and compressive yield (0.2%) strength of silane treated glass fibers filled composite increased from 2.26 to 4.59 GPa and 43.3 to 66.6 MPa, respectively, wtih increasing the filler content while the tensile strength decreased from 26.7 to 18.6 MPa. The elastic modulus of the untreated composite was less than that of the silane treated fiber composite. The tensile strength and compressive strengths were 20 to 50% lower than those of silane treated composites. The fracture toughness of the silane treated glass fiber additions were not significantly different from the untreated additions. The highest fracture toughness was obtained at 50% filler content with 1.65 MPa m.5. Set time increased from 3.5 to 7.7 minutes with increased filler content and peak temperature dropped from 68.3 to 34 degrees C. The results of this study indicate that the addition of silane coated glass fiber to BIS-GMA resin increased the elastic modulus, tensile and compressive strengths compared with non-treated fibers. The addition of either treated or non-treated fibers increased the set time of the material and decreased the maximum temperature.     

Reduced polymerization stress through non-bonded nanofiller particles

The stress that results from the placement of dental composite in a confined setting compromises the integrity of the marginal seal. Dental composites which include nanofiller particles that are not treated with a functional agent to couple them to the resin matrix can result in lower stress levels. Three types of nanofillers were evaluated having either a functional silane coating, a non-functional silane coating. or no coating. These were added at five different vol% levels to a photo-sensitized mixture of three dimethacrylate monomers alone or at three different vol% levels to the same resin filled with mini-filler particles to a clinically realistic level. The stress generated by these materials when cured in a confined setting was measured in a mechanical testing machine. The effect of monomer molecular weight on the stress levels was evaluated by preparing three resin formulations with varied co-monomer levels and filling them with bonded or non-bonded nanofillers. Reductions in polymerization stress of up to 31% were achieved among both the nanofilled resins and the mini-filled composite. The materials which contained a heightened level of diluent monomer produced significantly higher stress levels (ANOVA/Tukey's test, p < 0.05). Significant reductions in polymerization stress can be achieved through minor alterations in composite chemistry.     

Neue copolymerisate und polymergemische des vinylchlorids

Sterically ordered PVC is formed in the radical polymerization of vinyl chloride at sufficiently low temperatures. Its degree of branching, and probably also the number of 2,2-linkages and the molecular weight distribution differ from conventional PVC. Low temperature PVC can be processed at somewhat higher temperatures than ordinary PVC to give articles of higher heat deflection temperatures, higher tensile strength, but somewhat lower impact strength than ordinary PVC. The influence is shown which the processing parameters exert on the mechanical data of blends of PVC and low temperature PVC respectively with an ethylene/vinylacetate copolymer. Temperature and time of processing play a critical role in achieving of optimum properties. The properties of chlorinated low temperature PVC are compared with those of chlorinated PVC. The advantage of the higher heat deflection temperature and tensile strength of chlorinated PVC is lost in blends.     

Study of polymeric systems based on 2,2 bis-4(2-hydroxy-3-methacryloyl-oxypropoxy) phenyl propane.

2,2 bis-4(2-hydroxy-3-methacryloyloxypropoxy) phenyl propane is the basic monomer for a large number of proprietary dental composite filling materials. In this paper, studies have been made of its copolymers with various comonomers. 2,2 bis-4(2-hydroxy-3-methacryloyloxypropoxy) phenyl propane--tetrahydrofurfuryl methacrylate copolymers, at about the 95/5% v/v level, showed an enhanced modulus over that of the test material itself, to give a Young's modulus of -4.8 GPa. This reflected an enhanced activation energy of the glass transition temperature, indicating a very specific free volume effect of the diluent monomer. Further studies 2,2 bis-4(2-hydroxy-3-methacryloyloxypropoxy) phenyl propane-tetrahydrofurfuryl methacrylate room temperature polymerized copolymers showed that enhanced modulus could be achieved by including in the system small amounts of inhibitor; 0.3% v/v 2,6 di-tertiary butyl phenol elevated the Young's modulus of a benzoyl peroxide--NN-dihydroxy ethyl p-toluidine cured system from 3.1 to 3.6 GPa. Such resins may be useful in improved dental fissure sealants and composite filling materials.     

Adhesive layer properties as a determinant of dentin bond strength

The goal of this study is to evaluate the hypothesis that the properties of the resin adhesive might affect the microtensile bond strength (MTBS) of multibottle dental adhesive system. In order to alter the properties, the experimental resin adhesives containing 2,2-bis (4-2-hydroxy-3-methacryloyloxypropoxyphenyl)propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) at various ratios were prepared. Degree of conversion immediately after curing (DC-immed), degree of conversion at 48 h after curing (DC-48h) of a thin coat of the experimental adhesives, the flexural strength (FS) of the bulk specimens made of the experimental adhesives, pH, viscosity at shear rate of 1 S(-1), and the microtensile bond strength (MTBS) values of the adhesives to dentin were investigated. The maximum MTBS and FS values of the resin adhesives were observed when the ratio of Bis-GMA/TEGDMA was 60/40. However, pH and viscosity values increased with increasing Bis-GMA content in the adhesives. When Bis-GMA content was more than 60 wt %, the viscosity increased exponentially and restricted the DC and FS, and accordingly decreased the bond strength. The stronger the resin adhesives were, the higher the bond strength to dentin could be obtained.     

Characterization of Eumelanin as an Additive in High-Temperature Phthalonitrile-Based Resin Blends

Bio-manufactured eumelanin is investigated as a sustainable high-char carbon additive for use with moldable high temperature resins. Blends of Bisphenol A poly-ether-ether-ketone (PEEK)-based phthalonitrile (PN) with 0–30 wt% melanin are prepared and characterized for their compositional, thermal, and mechanical properties. Although the char yield increases from 10 to 30 wt% melanin loading, the presence of melanin decreases the thermal stability compared to PN resin alone. Despite this, the melanin-PN resins still maintain a very high char yield (>64%) up to 1000 °C under nitrogen. Rheology, thermal analysis, and mechanical measurements suggest off-gassing of the melanin and increased crosslinking between the melanin and PN, leading to a lower flexural strength resin with higher additive loadings. Spectroscopic studies suggest possible interaction between melanin and PN during co-curing, which ultimately can affect the processing and final properties of melanin-additive composite materials.