Investigation of double bond conversion,mechanical properties,and antibacterial activity of dental resins with different alkyl chain length quaternary ammonium methacrylate monomers (QAM)

In order to endow dental resin with antibacterial activity, a series of antibacterial quaternary ammonium methacrylate monomers (QAM) with different substituted alkyl chain length (from 10 to 18) were incorporated into commonly used 2,2-bis[4-(2′-hydroxy-3′-methacryloyloxy-propoxy)-phenyl]propane (Bis-GMA)/triethyleneglycol dimethacrylate (TEGDMA) (50?wt/50?wt) dental resin as immobilized antibacterial agents. Double bond conversion (DC), flexural strength (FS) and modulus (FM), and young and mature biofilms inhibition effectiveness of prepared dental resins were studied and Bis-GMA/TEGDMA without QAM was used as reference. Results showed that there was no significant difference on DC, FS, and FM between copolymer with and without 5?wt% QAM. Substituted alkyl chain length of QAM had no influence on DC, FS, and FM of copolymer, but had influence on antibacterial activity of copolymer. Antibacterial activity of copolymer increased with increasing of substituted alkyl chain length of QAM, and the sequence followed as 5%C10?<?5%C11≈5%C12?<?5%C16≈5%C18. Copolymers containing C18 and C16 had the best inhibition effectiveness on both young biofilm and mature biofilm, copolymers containing C12 and C11 only had inhibition effectiveness on young biofilm and copolymer containing C10 had none inhibition effectiveness on neither young biofilm nor mature biofilm.     

Synthesis,Characterization and Photopolymerization of a New Dimethacrylate Monomer Based on (α-Methyl-benzylidene)bisphenol Used as Root Canal Sealer

Methacrylate resin-based sealers have attracted wide attention because of their easy handling, superior aesthetic qualities, good mechanical properties and excellent adhesive ability with dentin. 2,2-Bis[4-(2′-hydroxy-3′-methacryloyloxypropoxy)-phenyl]-propane (Bis-GMA) is the main component of the newly developed commercial root canal sealer 'Epiphany', which is one of the methacrylate resin-based sealers. In order to further reduce the polymerization volume shrinkage of Bis-GMA, 4,4′-(α-methylbenzylidene)-bis(2′-hydroxy-3′-methacryloyloxy-propoxy)benzene (4,4′-AMBHMB) with higher molecular weight and larger molecular volume was synthesized to replace Bis-GMA as one of the components of the root canal sealer used in this study. The structure of monomer 4,4′-AMBHMB was confirmed by FT-IR, ¹H-NMR, mass spectrum and elemental analysis. The photopolymerization behavior of mixture of 4,4′-AMBHMB and triethylene glycol dimethacrylate (TEGDMA) was investigated by FT-IR. Degree of double bond conversion, volume shrinkage, water sorption and solubility, diffusion coefficient value, flexure strength and glass transition temperature of 4,4′-AMBHMB/TEGDMA system with a mass ratio of 50:50 were measured. A 50:50 Bis-GMA/TEGDMA formulation was used as reference. The results illustrated that 4,4′-AMBHMB/TEGDMA system had the same double bond conversion and water sorption with Bis-GMA/TEGDMA system. Polymerization shrinkage, water solubility and diffusion coefficient of 4,4′-AMBHMB/TEGDMA system were lower than that of the Bis-GMA/TEGDMA system, whereas the flexural strength and glass-transition temperature of 4,4′-AMBHMB/TEGDMA system were higher than that of the Bis-GMA/TEGDMA system.     

Preparation of low shrinkage stress Bis-GMA free dental resin composites with a synthesized urethane dimethacrylate monomer

A new urethane dimethacrylate TMA was synthesized through a typical urethane reaction. TMA was used to replace 1,6-bis(methacryloxy-2-ethoxycarbonyl- amino)-2,4,4- trimethylhexane (UDMA) in UDMA based composite partially or totally to prepare TMA containing composites. Critical properties of TMA containing composites were investigated. 2,2-bis[4(2-hydroxy-3-methacryloy- propyloy)phenyl]propane (Bis-GMA) based and UDMA based composites were used as references. FT-IR and ¹H-NMR confirmed the structure of TMA. All of experimental dental resin composites had the similar double bond conversion (p?>?0.05). With a certain amount of TMA, TMA containing composites could have lower volumetric shrinkage (p?<?0.05) and shrinkage stress (p?<?0.05) than control groups. Water sorption, solubility, flexural strength and modulus of TMA containing composites were not worse than those of control groups. All of TMA containing composites and UDMA based composite had the same fracture toughness (p?>?0.05), which was higher than that of Bis-GMA based composite (p?<?0.05). TMA has potential as Bis-GMA substitute to prepare Bis-GMA free dental resin composites with low shrinkage stress.     

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.     

Synthesis of poly(alkenoic acid) with L-leucine residue and methacrylate photopolymerizable groups useful in formulating dental restorative materials

To develop resin-modified glass ionomer materials, we synthesized methacrylate-functionalized acrylic copolymer (PAlk-LeuM) derived from acrylic acid, itaconic acid and N-acryloyl-L-leucine using (N-methacryloyloxyethylcarbamoyl-N′-4-hydroxybutyl) urea as the modifying agent. The spectroscopic (proton/carbon nuclear magnetic resonance, Fourier transform infrared spectroscopy) characteristics, and the gel permeation chromatography/Brookfield viscosity measurements were analysed and compared with those of the non-modified copolymer (PAlk-Leu). The photocurable copolymer (PAlk-LeuM, ~14?mol% methacrylate groups) and its precursor (PAlk-Leu) were incorporated in dental ionomer compositions besides diglycidyl methacrylate of bisphenol A (Bis-GMA) or an analogue of Bis-GMA (Bis-GMA-1), triethylene glycol dimethacrylate and 2-hydroxyethyl methacrylate. The kinetic data obtained by photo-differential scanning calorimetry showed that both the degree of conversion (60.50–75.62%) and the polymerization rate (0.07–0.14?s^?1) depend mainly on the amount of copolymer (40–50 wt.%), and conversions over 70% were attained in the formulations with 40 wt.% PAlk-LeuM. To formulate light-curable cements, each organic composition was mixed with filler (90 wt.% fluoroaluminosilicate/10 wt.% hydroxyapatite) into a 2.7:1 ratio (powder/liquid ratio). The light-cured specimens exhibited flexural strength (FS), compressive strength (CS) and diametral tensile strength (DTS) varying between 28.08 and 64.79?MPa (FS), 103.68–147.13?MPa (CS) and 16.89–31.87?MPa (DTS). The best values for FS, CS and DTS were found for the materials with the lowest amount of PAlk-LeuM. Other properties such as the surface hardness, water sorption/water solubility, surface morphology and fluorescence caused by adding the fluorescein monomer were also evaluated.     

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.     

Evaluation of New Tri-methacrylates as a Reactive Diluent in Root Canal Sealant

In this work, a novel tri-methacrylate oligomer, GPTEMA, with three long-branched chain structures was synthesized through the reaction of glycerol propoxylate triglycidyl ether (GPTE) and methacrylic acid. The structure of GPTEMA was confirmed by FT-IR, ¹H-NMR, gel-permeation chromatography (GPC) and element analysis. The GPTEMA was used to partially or completely replace TEGDMA as reactive diluent and applied in a root canal sealant system containing Bis-GMA. The effects of GPTEMA on the polymerization behavior of Bis-GMA/TEGDMA/GPTEMA co-polymer and properties of its polymerizing product were investigated. Polymerization shrinkage, double bond conversion, glass transition temperature, flexural strength, flexural modulus, water sorption and diffusion coefficient of the Bis-GMA/TEGDMA/GPTEMA co-polymer were measured. The results illustrated that the Bis-GMA/TEGDMA/GPTEMA co-polymer attained lower polymerization shrinkage and higher double bond conversion. However, its T _g, flexural strength and flexural modulus decreased with increasing content of GPTEMA, water sorption and diffusion coefficient increased with increasing content of GPTEMA.     

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.     

Study of water sorption,solubility and modulus of elasticity of light-cured dimethacrylate-based dental resins

Polydimethacrylate resins were prepared by photopolymerization of Bis-GMA, TEGDMA, UDMA or Bis-EMA (4) monomer, initiated by camphoroquinone/N,N-dimethylaminoethyl methacrylate system. The study of physical properties of these resins showed that TEGDMA seems to create the most dense polymer network, which however is the most flexible (0.74GPa), absorbs the highest amount of water (6.33 wt%) and releases the lowest amount of unreacted monomer (2.41 microg/mm(3)). UDMA and Bis-EMA (4) create more rigid networks, which absorb lower water and release higher unreacted monomer than TEGDMA. Bis-EMA (4) absorbs the lowest water amount (1.79 wt%) and releases the highest amount of unreacted monomer (14.21 microg/mm(3)). Bis-GMA leads to the formation of the most rigid network (1.43 GPa), which absorbs lower water than the resin made by TEGDMA but higher than the resin made by UDMA and Bis-EMA (4). Copolymers of Bis-GMA with the other monomers were also prepared, using various monomer combinations and molar ratios. Copolymers Bis-GMA/TEGDMA (50/50 and 70/30 wt%) showed significantly higher values for Young's modulus (1.83 and 1.78 GPa) than those predicted by the linear dependence of the values on the copolymer composition. Gradual replacement of TEGDMA with UDMA or/and Bis-EMA (4) in copolymerization with Bis-GMA resulted in more flexible resins with lower water sorption and higher solubility values, depending on the TEGDMA content.     

HPLC analysis of eluted monomers from two composite resins cured with LED and halogen curing lights

This study investigated the leaching of monomers (Bis-GMA and TEGDMA) from nano-hybrid (Filtek Supreme) and flowable (Filtek Flow) dental composite resins cured with LED or conventional halogen curing lights, and immersed in saliva or water for 24 h. Nine disc specimens were made for each experimental group. After the polymerization process, the specimens were immersed in either water or saliva and incubated at 37 degrees C for 24 h. Eluted Bis-GMA and TEGDMA monomers were detected using high performance liquid chromatography (HPLC). The data were analyzed using three-way ANOVA (p = 0.05) and the independent samples t test. TEGDMA (53.15-1 microg/L) was leached from the resins at a higher level than Bis-GMA (28-0.5 microg/L) (p < 0.01), regardless of the affecting factors: composite type, solvent (media) and type of curing light. In general, Filtek Flow resin released more TEGDMA than Filtek Supreme (p < 0.05), but the Supreme resin released more Bis-GMA than TEGDMA (p < 0.05). Halogen light induced greater monomer elution than LED light immersion in water. Saliva released more TEGDMA than water (p < 0.05). We conclude that (1) total leached TEGDMA was higher than total Bis-GMA, (2) saliva and halogen light (lower intensity than LED) leached more monomers from the resins, and (3) the flowable composite resin leached more TEGDMA than the nano-hybrid.     

Shrinkage strain-rates of dental resin-monomer and composite systems

The purpose of this study was to investigate the shrinkage strain rate of different monomers, which are commonly used in dental composites and the effect of monomer functionality and molecular mass on the rate. Bis-GMA, TEGDMA, UDMA, MMA, HEMA, HPMA and different ratios of Bis-GMA/TEGDMA were mixed with Camphorquinone and Dimethyl aminoethyle methacrylate as initiator system. The shrinkage strain of the samples photopolymerised at Ca. 550 mW/cm2 and 23 degrees C was measured using the bonded-disk technique of Watts and Cash (Meas. Sci. Technol. 2 (1991) 788-794), and initial shrinkage-strain rates were obtained by numerical differentiation. Shrinkage-strain rates rose rapidly to a maximum, and then fell rapidly upon vitrification. Strain and initial strain rate were dependent upon monomer functionality, molecular mass and viscosity. Strain rates were correlated with Bis-GMA in Bis-GMA/TEGDMA mixtures up to 75-80 w/w%, due to the higher molecular mass of Bis-GMA affecting termination reactions, and then decreased due to its higher viscosity affecting propagation reactions. Monofunctional monomers exhibited lower rates. UDMA, a difunctional monomer of medium viscosity, showed the highest shrinkage strain rate (P < 0.05). Shrinkage strain rate, related to polymerization rate, is an important factor affecting the biomechanics and marginal integrity of composites cured in dental cavities. This study shows how this is related to monomer molecular structure and viscosity. The results are significant for the production, optimization and clinical application of dental composite restoratives.     

Low viscosity dimethacrylate comonomer compositions [Bis-GMA and CH3Bis-GMA] for novel dental composites; analysis of the network by stray-field MRI,solid-state NMR and DSC & FTIR

The effect of dilution of 2,2-bis (4-(2-hydroxy-3-methacryloxyprop-1-oxy) phenyl) propane (Bis-GMA) with 2,2-bis(4-(2-methacryloxyprop-1-oxy)phenyl) propane (CH3Bis-GMA) on extent of polymerization (Ep) was investigated by FTIR and NMR. The results correlate well with Ep values of the system and its flexibility probed by Tg (obtained by DSC). Spatially resolved photopolymerization kinetics and polymerization shrinkage (PS, i.e. volumetric polymerization contraction) was also studied by stray-field imaging (STRAFI-MRI). PS was obtained in the presence of oxygen from the atmosphere as the total volumetric contraction. All the results were compared with those obtained for the Bis-GMA/TEGDMA (triethylene glycol dimethacrylate) system. Use of Bis-GMA mixed with hydrophobic low viscosity CH3Bis-GMA comonomer, as a substitute for the commonly used TEGDMA, resulted in improving significantly properties such as PS, water sorption and Ep, thereby reducing the unreacted double bond concentration.     

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.     

Dental restorative composites containing 2,2-bis-[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane derivatives and spiro orthocarbonates

Various dental restorative composite resins containing 2,2-bis-[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA) derivatives and spiro orthocarbonates (SOCs) were explored for minimizing the volumetric shrinkage that generally occurs during polymerization. Previous reports suggested mixing Bis-GMA with its derivative TMBis-GMA (2,2-bis[3,5-dimethyl-4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) to obtain a dental composite with low volumetric shrinkage. It was hypothesized that spiro orthocarbonates would expand volumetrically during polymerization, because of their sophisticated ring-opening reactions; therefore several of them were added to the mixture of Bis-GMA and TMBis-GMA to bring about further reductions in volumetric shrinkage. It was indeed possible to reduce the extent of volumetric shrinkage of dental composites containing SOCs, and to do so without compromising these resins' mechanical properties.     

Effects of long-term sub-lethal concentrations of dental monomers on THP-1 human monocytes

Studies have shown that monomers from dental resins are acutely cytotoxic, but little is known of their long-term effects at sub-lethal concentrations. The current study determined the long-term effects of sub-lethal concentrations of TEGDMA (triethyleneglycol dimethacrylate) and Bis-GMA (bisphenol-glycidylinethacrylate), two common dental monomers, on the in vitro cellular proliferation, succinic dehydrogenase activity, and total cellular protein production of monocytes. Human THP-1 monocytes were exposed to concentrations of 100, 200, and 400 micromol l(-1) of TEGDMA or 1, 5, and 25 micromol l(-1) Bis-GMA for 5 weeks. Controls received only vehicle solutions of ethanol. Each week cellular proliferation (hemocytometer), succinic dehydrogenase (SDH) activity (MTT) and total cellular protein (bicinchoninic acid) were assessed. The results were compared with ANOVA and Tukey intervals (alpha = 0.05). TEDGMA had no proliferative or cellular protein effects, but increased SDH activity 20-60% in week 1 (p < 0.05). SDH activity then decreased 40% in week 2, followed by a gradual increase of 30-40% over week 3-5 (p < 0.05). Bis-GMA reduced proliferation by 40-60% from 1-5 weeks exposure (p < 0.05). However, SDH activity and total protein per cell were not affected. There was some indication of increased SDH activity after 5 weeks (20-30%, p < 0.05). Sub-lethal concentrations of TEGDMA and Bis-GMA have significant long-term effects on monocytes at low-dose 5-week exposures in vitro. Each monomer acted differently.     

Effects of long-term sub-lethal concentrations of dental monomers on THP-1 human monocytes

Studies have shown that monomers from dental resins are acutely cytotoxic, but little is known of their long-term effects at sub-lethal concentrations. The current study determined the long-term effects of sub-lethal concentrations of TEGDMA (triethyleneglycol dimethacrylate) and Bis-GMA (bisphenol-glycidylmethacrylate), two common dental monomers, on the in vitro cellular proliferation, succinic dehydrogenase activity, and total cellular protein production of monocytes. Human THP-1 monocytes were exposed to concentrations of 100, 200, and 400 μmol l^-1 of TEGDMA or 1, 5, and 25 μmol l^-1 Bis-GMA for 5 weeks. Controls received only vehicle solutions of ethanol. Each week cellular proliferation (hemocytometer), succinic dehydrogenase (SDH) activity (MTT) and total cellular protein (bicinchoninic acid) were assessed. The results were compared with ANOVA and Tukey intervals (α =0.05). TEDGMA had no proliferative or cellular protein effects, but increased SDH activity 20-60% in week 1 (p < 0.05). SDH activity then decreased 40% in week 2, followed by a gradual increase of 30-40% over week 3-5 (p < 0.05). Bis-GMA reduced proliferation by 40-60% from 1-5 weeks exposure (p < 0.05). However, SDH activity and total protein per cell were not affected. There was some indication of increased SDH activity after 5 weeks (20-30%, p < 0.05). Sub-lethal concentrations of TEGDMA and Bis-GMA have significant long-term effects on monocytes at low-dose 5-week exposures in vitro. Each monomer acted differently.     

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.     

Bis-GMA／（SiO2-ZrO2）纳米复合树脂的制备与性能研究

目的：通过添加纳米无机填料对树脂基质进行增强增韧改性,来满足修复性牙科材料的要求,解决树脂基质耐磨性较差、强度低的问题,制备出合适的临床牙科修复材料。方法：采用原位分散法,双酚A-甲基丙烯酸缩水甘油酯（Bis-GMA）和双甲基丙烯酸二缩三乙二醇酯（TEGDMA）共同作为树脂基质,混合加入经过硅烷偶联剂（KH-570）表面处理的纳米氧化硅（SiO2）和二氧化锆（ZrO2）制备新型复合树脂,同时使用高速搅拌和超声分散等制备工艺来改善纳米填料分散体系,运用X射线衍射（XRD）、扫描电子显微镜（SEM）等实验手段对Bis—GMA纳米复合树脂材料进行性能测试及结构表征。结果：使用高速搅拌和超声分散技术可使经过表面处理的纳米SiO2和ZrO2均匀分散在树脂基质中,达到了纳米级原生粒子分散效果,发挥了不同无机填料间的相互作用,能够有效的提高复合树脂材料的机械性能。结论：该方法制备出的高性能Bis—GMA／nano（SiO2-ZrO2）复合树脂牙科材料,能充分满足临床牙科修复学需要。     

Dental composites based on hybrid and surface-modified amorphous calcium phosphates

The objectives of this study were to prepare hybrid and surface-modified amorphous calcium phosphates (ACPs) as fillers for mineral-releasing dental composites, and determine whether the mechanical strength of the composites could be improved without decreasing their remineralization potential. ACP was hybridized with tetraethoxysilane or zirconyl chloride and surface-treated with 3-methacryloxypropoxytrimethoxy silane (MPTMS) or zirconyl dimethacrylate (ZrDMA). Composites fabricated with unmodified ACP (u-ACP), hybrid or surface-modified ACP filler and photo-activated Bis-GMA, TEGDMA and 2-hydroxyethyl methacrylate (HEMA) (BTH resin), Bis-GMA, TEGDMA, HEMA and MPTMS (BTHS resin) or Bis-GMA, TEGDMA, HEMA and ZrDMA (BTHZ resin) were tested for their remineralizing potential and biaxial flexure strength (BFS). Ion releases from all composites were significantly above the minimum necessary for reprecipitation of apatite. The BFS of unfilled polymers was not adversely affected by immersion in saline solutions. The BFS of BTH and BTHS composites deteriorated upon soaking. However, BTHZ composites were practically unaffected by exposure to saline solutions. Filler hybridization resulted in a modest, but significant, improvement in the BFS (up to 24%) of BTHZ composites. Heterogeneous distribution of the ACP on disk surfaces was detected by the FTIR microspectroscopy analyses. This might have been caused by uncontrolled aggregation of ACP particles that appeared to hinder interfacial filler/resin interactions and diminish the mechanical strength of composites.     

Polycarboxylated microfillers incorporated into light-curable resin-based dental adhesives evoke remineralization at the mineral-depleted dentin

This study aimed at evaluating the remineralizing properties of three experimental light-curable resin-based dental adhesives containing tailored polycarboxylated microfillers. A co-monomers blend was firstly formulated and then mixed with each of the following microfillers: polycarboxylated bioactive glass (PBAG), polycarboxylated calcium silicates (PCS), and polycarboxylated calcium silicates-doped brushite (PDP). The three experimental and a filler-free control resins were applied onto 10% orthophosphoric acid treated dentin discs and light cured. The specimens were soaked in artificial saliva (AS) for 3, 7, and 14?days. Dentin mineral variation was monitored using attenuated total reflection-Fourier transform infrared (ATR-FTIR) and Raman spectroscopy. Confocal laser scanning microscopy (CLSM) was employed to observe the ultra-morphology/nanoleakage along the resin–dentin interface. The bonding ability and the durability of the resin–dentin bonds were investigated through microtensile bond strength (μTBS) test. ATR-FTIR and Raman showed a significant increase of the mineral matrix area ratio and phosphate peak intensity in specimens treated with the experimental resins within 14?days (p?p?>?0.05). Dentin treated using PBAG or PCS exhibited higher level of remineralization than the specimens in PDP group. CLSM showed reduction in nanoleakage, although the remineralization of the hybrid layer induced a significant drop in the μTBS after 3-month storage (p?相似文献