BisGMA analogues as monomers and diluents for dental restorative composite materials.

Current commercially available dental composite materials have certain limitations for their use, including high monomer viscosity and high polymerization shrinkage, resulting in residual stresses and interfacial gaps. This study focused on the chemical modification of resin monomer bisphenol A-glycidyl methacrylate (bisGMA), so as to reduce the viscosity and polymerization shrinkage. In this design, the hydroxyl groups of bisGMA were transformed into ester groups with various alkyl chain length and branching. The modified monomers showed promising properties including reduced viscosity, reduced polymerization shrinkage, increased hydrophobicity, increased degree of double bond conversion, and improved mechanical properties of the resulting dental resin composites. The structure/property relationships of the new monomers were investigated, and optimal monomer structures were identified for dental composites with improved properties.

[Development of novel self-healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer].

OBJECTIVE: To develop novel self- healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer, and to measure its properties for further clinical application. METHODS: Microcapsules filled with healing monomer of triethylene glycol dimethacrylate were synthesized according to methods introduced in the previous research. Microcapsules were added into novel resin composite containing nano-antibacterial silica fillers grafted with long chain alkyl quaternary ammonium at mass fractions of 0, 2.5%, 5.0%, 7.5% or 10.0%. A commercial resin composite (Tetric N-Ceram) was used as control. Flexural test was used to measure resin composite flexural strength and elastic modulus. The single edge V-notched beam method was used to measure fracture toughness and self-healing efficiency. Scanning electron microscope (SEM) was used to examine the fractured surface of selected specimen for investigation of fracture mechanisms. RESULTS: The flexural strength and elastic modulus of the resin composite were (96.4 ± 14.3) MPa and (6.2 ± 1.1) GPa respectively after incorporation of microcapsules up to 7.5%, and no significant difference was found between the experimental group and the control group [(99.1 ± 11.9) MPa and (6.1 ± 1.1) GPa] (P>0.05). The self-healing efficiency of (66.8 ± 7.0)% and (79.3 ± 9.7)% were achieved for resin composite with microcapsule mass fractions at 7.5% and 10.0%. SEM image showed that irregular films covered the fractured surface. Conclusions This novel self-healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer exhibited a promising self- healing ability, which enabled itself well up for combating bulk fracture and secondary caries in clinical application.

Synthesis and characterization of new dimethacrylate monomer and its application in dental resin.

In this study, a dimethacrylate monomer, 1,4-Bis[2-(4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl)-2propyl]benzene (BMPPB) was synthesized to replace 2,2-bis[4-(2'-hydroxyl-3'-methacryloyloxy-propoxy)phenyl]propane (Bis-GMA) as one component of dental restorative materials. The structure of BMPPB and its intermediate product 1,4-bis[2-(4-(oxiranylmethoxy)phenyl)-2propyl]benzene (BOPPB) were confirmed by Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance spectroscopy ((1)H-NMR), and elemental analysis. In order to evaluate the possibility of replacing Bis-GMA with BMPPB in dental resin, double bond conversion (DC), polymerization shrinkage, contact angle, water sorption (WS) and solubility (SL), and flexural strength (FS) and modulus of BMPPB/tri(ethylene glycol)dimethacrylate (TEGDMA) (50/50 wt) resin system and Bis-GMA/BMPPB/TEGDMA (25/25/50 wt) resin system were studied. Commercially used Bis-GMA/TEGDMA (50/50 wt) dental resin system was used as reference. The results showed that BMPPB-contained copolymer had higher DC, higher WS and SL than the copolymer that only contained Bis-GMA (p<0.05). All of the copolymers had nearly the same contact angle (p>0.05). BMPPB/TEGDMA resin system had lower polymerization shrinkage, higher FS and modulus (p<0.05) than Bis-GMA/TEGDMA resin system. There was no significant difference on polymerization shrinkage, FS and modulus (p>0.05) between Bis-GMA/BMPPB/TEGDMA resin system and Bis-GMA/TEGDMA resin system. Before and after water immersion, both FS and modulus of every copolymer did not change significantly (p>0.05). Therefore, BMPPB had potential to be used to replace Bis-GMA as base resin in dental restorative materials, but many studies should be undertaken further.

Preparation and characterization of a BisGMA-resin dental restorative composites with glass, silica and titania fillers.

A photo-polymerizable Bisphenol-A diglycidylether methacrylate resin was characterized by Fourier transform infrared spectroscopy after its irradiation under different conditions to identify the best curing. Bonding-agent free composites with particles of ball-milled glass, silica and titania at loading of 10 and 50%wt were prepared, and their viscoelastic properties investigated by dynamic mechanical analysis, in experimental conditions close to the working environment in the mouth. All composites showed good stability at the considered conditions. The stiffest composite was the silica one, which was based on the smallest primary particles. The storage moduli close to room temperature (25°C) and mastication frequency (1 Hz) were extracted as reference bending moduli for the materials, and compared to static compressive moduli measured by nanoindentation performed by atomic force microscopy.Nanoindentation showed qualitative results in agreement with dynamic mechanical analysis as to the ranking of different materials, while resulting in approximately two-fold elastic modulus.

Investigation on synthesis and properties of isosorbide based bis-GMA analogue.

The aim of this work was to synthesize and investigate properties of a novel dimethacrylic monomer based on bioderived alicyclic diol--isosorbide. Its potential as a possible substitute of 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (BISGMA), widely used in dental restorative materials and suspected for toxicity was assessed. The novel monomer was obtained in a three-step synthesis. First, isosorbide was etherified by a Williamson nucleophilic substitution and subsequently oxidized to isosorbide diglycidyl ether (ISDGE). A triphenyl phosphine catalyzed addition of methacrylic acid to ISDGE resulted in 2,5-bis(2-hydroxy-3-methacryloyloxypropoxy)- 1,4:3,6-dianhydro-sorbitol (ISDGMA). The monomer obtained was photopolymerized using camphorquinone/2-(dimethylamino)ethyl methacrylate initiating system. Next, compositions with triethylene glycol dimethacrylate (TEGDMA) were prepared and polymerized. Double bond conversion, polymerization shrinkage and water sorption of resulting polymers were determined. Selected mechanical (flexular strength and modulus, Brinell hardness) and thermomechanical (DMA analysis) properties were also investigated. BISGMA based materials were prepared as reference for comparison of particular properties.

Fabrication and evaluation of Bis-GMA/TEGDMA resin with various amounts of silane-coated silica for orthodontic use.

The objective of this research was to fabricate a composite with an optimum filler level in a bisphenol-A-glycidyldimethacrylate (Bis-GMA) triethylene glycidal dimethacrylate (TEGDMA) resin for bonding of metallic orthodontic brackets to achieve the best handling characteristics with optimum bond strength and without compromising the mechanical properties of the adhesive. One-hundred and sixty extracted human premolars free of any detectable pathology or buccal surface alterations were collected and divided into four groups. In group 1 (control), the teeth were bonded with stainless steel brackets using Transbond XT. In groups 2, 3, and 4, the teeth were bonded with metal brackets using a Bis-GMA/TEGDMA resin with 80, 60, and 20 per cent by weight silane-coated silica of a spherical shape with a mean size of 0.01 µm. Shear bond strength (SBS) of the composites was determined and the adhesive remnant index (ARI) and enamel fracture post-debonding were assessed. According to one-way analysis of variance and Tukey's honestly significant difference (HSD) multiple comparison tests, the SBS of group 4 (10.54 MPa) was considerably less than that of groups 1 (26.1 MPa), 2 (25.5 MPa), and 3 (24.6 MPa). Chi-square analysis revealed that there was an insignificant difference in the incidence of enamel fracture between groups 1 and 2, while a significant difference was present between groups 1 and 2 and 3 and 4. An insignificant difference was also observed in the location of the adhesive failure between the four groups. While all the bonding adhesives tested can be safely used for bonding of brackets, 60 per cent filled Bis-GMA/TEGDMA was superior clinically due to its ease of handling and superior bond strength.

Brillouin study of photopolymerization process of two-monomer systems.

The results of Brillouin scattering investigations of two-component system: 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane/polyethylene glycol methacrylate (bis-GMA/PEGMM) containing 0, 30, 50, 70, 85 and 100 mol% of PEGMM are presented. For the first time the Brillouin spectroscopy was used to monitor the progress of the polymerization process. The polymerization was initiated by ultraviolet radiation (λ=365 nm), at temperature 20°C and 40°C. Some of the physical parameters characteristic for this system such as velocity V, adiabatic compressibility ß(ad) and attenuation coefficient α of the acoustic waves have been estimated from Brillouin spectra as a functions of the polymerization time. The obtained results have been discussed in terms of changes of the elastic properties of the two-component system occurring during polymerization process and their dependence on bis-GMA/PEGMM system composition.

Creatinine biomaterial thin films grown by laser techniques.

Creatinine thin films were synthesised by matrix assisted pulsed laser deposition (PLD) techniques for enzyme-based biosensor applications. An UV KrF* (lambda=248 nm, tau approximately 10 ns) excimer laser source was used for the irradiation of the targets at incident fluence values in the 0.3-0.5 J/cm2 range. For the matrix assisted PLD the targets consisted on a frozen composite obtained by dissolving the biomaterials in distilled water. The surface morphology, chemical composition and structure of the obtained biomaterial thin films were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, and electron dispersive X-ray spectroscopy as a function of the target preparation procedure and incident laser fluence.

Effects of molecular structure of the resins on the volumetric shrinkage and the mechanical strength of dental restorative composites.

To prepare a dental composite that has a low amount of curing shrinkage and excellent mechanical strength, various 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA) derivatives were synthesized via molecular structure design, and afterward, properties of their mixtures were explored. Bis-GMA derivatives, which were obtained by substituting methyl groups for hydrogen on the phenyl ring in the Bis-GMA, exhibited lower curing shrinkage than Bis-GMA, whereas their viscosities were higher than that of Bis-GMA. Other Bis-GMA derivatives, which contained a glycidyl methacrylate as a molecular end group exhibited reduced curing shrinkage and viscosity. Methoxy substitution for hydroxyl groups on the Bis-GMA derivatives was performed for the further reduction of the viscosity and curing shrinkage. Various resin mixtures, which had the same viscosity as the commercial one, were prepared, and their curing shrinkage was examined. A resin mixture containing 2,2-bis[3,5-dimethyl, 4-(2-methoxy-3-methacryloyloxy propoxy) phenyl] propane] (TMBis-M-GMA) as a base resin and 4-tert-butylphenoxy-2-methyoxypropyl methacrylate (t-BP-M-GMA) as a diluent exhibited the lowest curing shrinkage among them. The composite prepared from this resin mixture also exhibited the lowest curing shrinkage along with enhanced mechanical properties.

Synthesis and photopolymerization of low shrinkage methacrylate monomers containing bulky substituent groups.

OBJECTIVES: This study was conducted to determine whether novel photopolymerizable formulations based on dimethacrylate monomers with bulky substituent groups could provide low polymerization shrinkage without sacrifice to degree of conversion, and mechanical properties of the polymers. METHODS: Relatively high molecular weight dimethacrylate monomers were prepared from rigid bisphenol A core groups. Photopolymerization kinetics and shrinkage as well as flexural strength and glass transition temperatures were evaluated for various comonomer compositions. RESULTS: Copolymerization of the bulky monomers with TEGDMA show higher conversion but similar shrinkage compared with Bis-GMA/TEGDMA controls. The resulting polymers have suitable mechanical strength properties for potential dental restorative materials applications. When copolymerized with PEGDMA, the bulky monomers show lower shrinkage, comparable conversion, and more homogeneous polymeric network structures compared with Bis-EMA/PEGDMA systems. SIGNIFICANCE: The novel dimethacrylate monomers with reduced reactive group densities can decrease the polymerization shrinkage as anticipated, but there is no significant evidence that the bulky substituent groups have any additional effect on reducing shrinkage based on the physical interactions as polymer side chains. The bulky groups improve the double bond conversion and help maintain the mechanical properties of the resulting polymer, which would otherwise decrease rapidly due to the reduced crosslinking density. Further, it was found that bulky monomers help produce more homogeneous copolymer networks.

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.

Nueva matriz orgánica con menor contracción de polimerización / New organic matrix with less polymerization shrinkage

Se modificó la matriz orgánica de composites dentales a partir de la síntesis de nuevos monómeros. Estos fueron caracterizados por espectroscopía infrarroja y resonancia magnética nuclear y se determinó su densidad y viscosidad. Además, se evaluó la contracción de polimerización total alcanzada por dichos monómeros puros y por mezclas de éstos con cantidades crecientes de Bis-GMA. La caracterización espectroscópica de los monómeros sintetizados corroboró la introducción de las modificaciones propuestas. La viscosidad de estos compuestos fue significativamente menor que la del Bis-GMA. Matrices orgánicas con los monómeros derivados presentaron menor contracción que la de las mismas proporciones de Bis-GMA y TEGDMA. De lo anterior se concluye que: a) la acilación del Bis-GMA permite obtener nuevos monómeros de menor viscosidad, ya que se elimina la posibilidad de formar uniones hidrógeno intermoleculares. b) las matrices orgánicas donde se reemplaza el TEGDMA por los monómeros sintetizados, Ac-Bis-GMA y Bz-Bis-GMA, generan menor contracción de polimerización que las originales. Realizado dentro del proyecto O022 de la Universidad de Buenos Aires, Argentina (AU)

Effect of bifunctional comonomers on mechanical strength and water sorption of amorphous calcium phosphate- and silanized glass-filled Bis-GMA-based composites.

This study seeks to elucidate structure-property relationships in a series of unfilled dental copolymers and their composites. The copolymers/composites were derived from photo-activated binary monomer systems based on 2,2-bis[p-2'-hydroxy-3'-methacryloxypropoxy)phenyl] propane (Bis-GMA) and equimolar amounts of a bifunctional, surface-active comonomer, i.e., 2-hydroxyethyl methacrylate (HEMA), glycerol dimethacrylate (GDMA) or ethylene glycol methacrylate phosphate (PHEMA). Triethyleneglycol dimethacrylate, a widely used comonomer for Bis-GMA, was used as a control. Two types of fillers were investigated: (1) a hydrophilic, silica-modified amorphous calcium phosphate (Si-ACP) and (2) a more hydrophobic, silanized nanosized silica (n-SiO(2)). Both the unfilled copolymers and their composites were evaluated for biaxial flexure strength (BFS), both dry and wet after 30 days immersion in buffered saline, and for water sorption (WS) and their WS kinetic profiles. The Bis-GMA copolymers and composites derived from HEMA and GDMA had BFS and WS values, as well as WS kinetic profiles, similar to the controls. Copolymers and composites based on Bis-GMA/PHEMA had lower BFS and higher WS values. Si-ACP composites had significantly lower BFS values (that were further diminished on soaking) than their copolymers. WS increased as the level of this filler was increased except for Bis-GMA/PHEMA composites. With n-SiO(2) as the filler, a more moderate reduction in BFS occurred compared to the unfilled copolymers. By contrast to Si-ACP composites, the WS of all the n-SiO(2) composites decreased with increasing filler level. From this study it is evident that both the chemical structure of the polymer matrix and the type of filler system can have significant effects on the strength and water-related properties of dental composites.

[Hormone dysregulators. Pseudo-estrogens in dental composite resins and sealanta?]. / Hormoonontregelaars. Pseudo-oestrogenen in tandheelkundige composieten en sealants?

A number of polluting chemicals in the ecosystems must be characterized as hormone disruptors. Among others, male animals appear to become feminized by the action of the so-called pseudo-estrogens and under their influence mens' fertility is said to decrease. Composites and sealants based on Bis-GMA resin may contain bisphenol-A as an impurity and Bis-DMA, from which in saliva bisphenol-A will be formed by hydrolytic degradation. Therefore, in extreme circumstances a weak estrogenic effect is not impossible on the short-term. However, the amounts of these probably not very potent estrogenic compounds are small, thereby resulting in a tolerable risk on the short term. Long-term-effects and synergism with pseudo-estrogens from other sources prompt further studies in order to verify the safety of the Bis-GMA containing products.

Surface structural change of bioactive inorganic filler-resin composite cement in simulated body fluid: effect of resin.

Recently much attention has been paid to bioactive filler-resin composite cements because they can solidify in a few minutes to give high mechanical strengths and they can bond to living bone. In this study the dependence on resin of apatite-forming ability in simulated body fluid (SBF) was investigated for the composite cements of bioactive CaO-SiO2-P2O5-CaF2 glass with polymethyl methacrylate (PMMA) or bisphenol-a-glycidyl methacrylate/triethyleneglycol (Bis-GMA/TEGDMA) resin. The PMMA-containing composite cement did not show the apatite-forming ability in SBF because the reaction of the glass grains with SBF was inhibited due to the complete covering of the grains with PMMA. To the contrary, the Bis-GMA/TEGDMA-containing cement exhibited high apatite-forming ability in SBF; these monomers significantly dissolved from the composite surface into SBF, causing a direct exposure of the glass grains to SBF to convert into silica gel. It is assumed that thus formed silica gels, and the silicate ions that were dissolved and adsorbed onto the composite surface, induced the apatite nucleation between the spaces of the glass grains and on the composite surface, respectively. A continuous bone-like apatite layer was formed on the top surface of the glass-Bis-GMA/TEGDMA composite cement in a short period.

Synthesis of fluorinated Bis-GMA and its use with other fluorinated monomers to formulate hydrophobic composites.

Fluorinated Bis-GMA was synthesized and used with other commercially available fluorinated monomers and diluents to prepare hydrophobic composites. The composites were formulated as one-paste systems and were polymerized using blue light. Mechanical properties and water-related qualities were determined. Fluorination generally improved the hydrophobicity of the composites, but there was no clear-cut effect on mechanical properties.