Chemical properties of 1,3-bis(3-methacryloxypropyl)-1,1,3,3-tetramethyldisiloxane-methyl methacrylate copolymer.

This study evaluated the chemical properties such as water sorption, water solubility and solvent resistance of a new resin material consisting of 1,3-bis(3-methacryloxypropyl)-1,1,3,3-tetramethyldisiloxane (BMPMS) and methyl methacrylate (MMA). Water sorption was evaluated by immersing the specimens in water at 37±1°C for 1 week, water solubility was evaluated by keeping the specimens in a desiccator under dry conditions at 37±1°C until the weight became constant, and solvent resistance was evaluated by immersing the specimens in acetone for 1 week and measuring the dissolved weight of acetone volatilized from those liquids. The water sorption and solvent resistance of the new resin were improved with increasing amount of BMPMS, whereas the water solubility remained the same value and did not depend on the amount of BMPMS.

Cytotoxic effects of acrylic acid, methacrylic acid, their corresponding saturated carboxylic acids, HEMA, and hydroquinone on fibroblasts derived from human pulp.

The purpose of this study was to evaluate the cytotoxicity of acrylic and methacrylic acid (AA and MA), propanoic acid and isobutylic acid (PRA and IBA) which were the corresponding saturated carboxylic acids, 2-hydroxylethyl methacrylate and acrylate (HEMA and HEA), and hydroquinone (HQ). The growth of the fibroblast when exposed to AA decreased with increase of the acid, and was less than when exposed to MA. The growth when exposed to their corresponding saturated acids, PRA and IBA, showed a similar tendency to AA and MA. The growth of fibroblasts exposed to 5 mmol/L HEMA after 4 days and 3 mmol/L HEMA after 6 days was significantly different compared with that without HEMA. The growth in 1, 3, and 5 mmol/L of HEA after 2 days was markedly decreased compared with that without HEA, and the cells were probably lifeless. The growth when exposed to HQ was extremely lower than their acids.

Cytotoxic effects of polybasic acids, poly(alkenoic acid)s, and the monomers with various functional groups on human pulp fibroblasts.

This study evaluated the cytotoxicity of various polybasic acids, poly(alkenoic acid)s, and the monomers with various acidic functional groups such as carboxyl, phosphoryl, and sulfo group. The cell growth of fibroblasts cultivated in medium containing polybasic acids and polymers up to the concentration to 5 mmol/L was not significantly different compared with that of control without their acids. On the other hand, the cell growth fibroblasts cultivated in medium containing 1 mmol/L of the monomers with acryloyloxy and phosphoryl or carboxyl group decreased remarkably compared with that of the control and the cells were probably lifeless. Those exposed to the monomers with a ether bond and a carboxyl group or a amide bond and a sulfo group was not significantly different compared with that of control.

Study on antibacterial dental resin using tri-n-butyl(4-vinylbenzyl)phosphonium chloride.

The antibacterial properties of a polymeric phosphonium salt were studied to determine its suitability as an additive to develop an antibacterial dental resin. The phosphonium salt monomer studied was tri-n-butyl(4-vinylbenzyl)phosphonium chloride (VP), and acrylic acid (AC) and methacryloyloxyethyl trimethyl ammonium chloride (MA) were used as controls. The antibacterial activity of these monomers and their corresponding polymers (PVP, PAC, and PMA) against Streptococcus mutans (S. mutans) was examined. When incubating S. mutans in a medium containing 10 µmol/mL for 24 hours, the antibacterial activity of PVP against S. mutans was high, while the antibacterial activity of PMA and VP was lower. AC, PAC and PMA exhibited the lowest antibacterial activity. The mechanical properties of the copolymers of methyl methacrylate, 2-hydroxyethyl methacrylate, and VP decreased as VP content increased, and were lower than those of poly(methyl methacrylate).

Characteristics of novel di-α-fluoroacrylate derivatives with polyfluoroalkyl aromatic backbone as a binder resin of direct filling materials.

To realize good mechanical properties and water resistance of a dental resin, novel di-α-fluoroacrylates with polyfluoroalkyl aromatic backbone were studied. The monomers were 2,2-bis(4-α-fluoroacryloxy phenyl)propane, 2,2-bis(4-α-fluoroacryloxy phenyl) hexafluoropropane, and 1,3-bis(2-α-fluoroacryloxy-2-hexafluoropropyl)benzene. The copolymers of the monomers and methyl methacrylate (MMA) were excellent in hardness, Izod impact strength, abrasion resistance, and water resistance, and showed similar values of compressive, diametral tensile, tensile, and bending strength compared with copolymers prepared from the corresponding dimethacrylate derivatives and MMA.

Study on ceramic coating on the enamel surface using a carbon dioxide laser.

The aims of this study were to evaluate a new restorative method using a carbon dioxide laser (CO(2)-laser) and to evaluate the acid resistance of teeth. Experimental calcium phosphate glass (CPG) powder and two low melting point ceramics (Finesse and zirconium silicate) were fused to enamel surfaces using a CO(2)-laser at an irradiation intensity of 1.0 watt for 30 seconds with a beam size of 0.49 mm at the focal point. The treated teeth were observed with a scanning electron microscope, and the acid resistance of the treated enamel surfaces was evaluated. The CPG fused successfully to the enamel surface, and the treated enamel surface showed high acid resistance compared with the low melting point ceramics and the non-irradiated surfaces. This system may lead to the development of new restorative methods that do not require the use of bonding agents.

Characteristics of acrylic acid-modified temperature-responsive polymers and application as cement liquid.

To reduce the adverse effects of water on the mechanical properties and bonding durability of glass ionomer cements, experimental cements which used a temperature-responsive polymer as the cement liquid were prepared and evaluated in this study. Temperature-responsive copolymers were synthesized using radical polymerization with varying molar ratios of N-isopropylacrylamide (NIPAM) and acrylic acid (AA). It was found that copolymer synthesis with varying ratios of NIPAM and AA was able to modify the lower critical solution temperature to range between 27 and 42°C. Bond strength of the cement prepared from AA/NIPAM copolymer containing 53 mol% AA was better than that prepared from polyacrylic acid (PAA) - the conventional cement liquid. However, compressive strength of the experimental cement was slightly lower than that of PAA cement.

Synthesis of dimethacryloxy ethyl-1,1,6,6-tetrahydro-perfluorohexamethylene-1,6-dicarbamate as dental base monomers and the mechanical properties of the copolymers of the monomer and methyl methacrylate.

To recognize good mechanical properties and water-resistance of a dental resin, dimethacryloxyethyl-1,1,6,6-tetrahydro-perfluoro-hexamethylene-1,6-dicarbamate (FDMHD) was newly synthesized. FDMHD initially was a white powder with m.p. 98.5-99.5°C. The copolymers of FDMHD and methyl methacrylate (MMA), FDMHD/MMA copolymers, were prepared to estimate the basic properties for dental resin materials. The compressive strength of FDMHD/MMA copolymers was almost the same compared with those of the copolymers of Bis-GMA or dimethacryloxyethyl-hexamethylene-1,6-carbamate (DMHD) and MMA. The bending, tensile, diametral tensile, impact strength and toughness of FDMHD/MMA copolymers containing 10.4 mol% FDMHD were higher than those of Bis-GMA/MMA copolymer, and the water sorption of FDMHD/MMA copolymers was lower than those of DMHD/MMA copolymers.

Synthesis of collagen-like sequential polypeptides containing O-phospho-L-hydroxyproline and preparation of electrospun composite fibers for possible dental application.

A synthetic route is described for collagen-like polypeptides constructed from O-phospho-L-hydroxyproline [Hyp(PO(3)H(2))] residues. Using the synthetic polypeptides and a natural protein, gelatin, fine fibers and their network structures (ESNWs) were prepared via electrospinning. The composite ESNWs can induce the mineralization of calcium phosphate. The phosphoryl groups of the Hyp(PO(3)H(2)) residues affect both the crystalline phase and amount of the calcium phosphate, depending on the chemical structure in the repeating sequence. The composite ESNWs can be developed as a biocompatible replacement of the extracellular matrix of hard tissues, and thus can be applied as dental materials for restoration of dental cavities or as a sealant for pits and fissures.

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.

Effect of aluminoborate whiskers on mechanical properties of polycarboxylate cements.

The mechanical properties of polycarboxylate cements containing 20 mass% of four kinds of aluminoborate whiskers with different fiber lengths and diameters were evaluated. Bending strength of the cements increased with increase in fiber length, whereby the strength of the cement with the longest fiber was about two times greater than that of whisker-free cement. The diametral tensile strengths of the four fiber-reinforced cements were also about two times greater than that of whisker-free cement, but which was not dependent on fiber length. Compressive strength was the same or slightly higher than that of whisker-free cement. SEM observation of fractured specimen after diametral compression test showed high affinity between the cement matrix and the whisker.

Basic study on the application of novel functional monomers to a denture base resin.

To improve the mechanical properties and to reduce the water sorption amount of denture base resins, the polymerization characteristics of three novel fluoro-substituted monomers (MAF-TBN, MAF-MAE, MAF-TBN) and three styrene-type monomers (PTBS, PEES, PACS) were studied, as well as the copolymerization of these monomers with MMA. Subsequently, the mechanical properties and water sorption of the copolymers prepared from these monomers and MMA were evaluated. The polymerization reactivity of the monomers by BPO was lower than MMA, except for PACS. However, the copolymerization reactivity of the monomers with MMA was good, except for MAF-TBN. The copolymer of MAF-MAE and MMA in three fluoro-substituted monomers and PACS and MMA in three styrene-type monomers showed similar mechanical properties and extremely low water sorption compared with those of PMMA.

Three-body-wear resistance of the experimental composites containing filler treated with hydrophobic silane coupling agents.

This paper evaluated the wear resistance of resin composite materials with fillers which were modified with a novel hydrophobic silane coupling agent. The novel silane coupling agent containing hydrophobic phenyl group 3-(3-methoxy-4-methacryloyloxyphenyl)propyltrimethoxysilane (p-MBS) was synthesized. The experimental light-cure hybrid composites containing 85wt% of filler modified with this silane were formulated. Twelve specimens were prepared for the three-body-wear test with the ACTA machine and the collected data were analyzed statistically using a one-way ANOVA and Tukey's multiple comparison test as the post hoc test. The wear of the composites containing fillers treated with p-MBS was significantly lower compared with the composite materials containing fillers pretreated with 3-methacryloyloxypropyltrimethoxysilane or the commercially composites (AP-X and ELS extra low shrinkage) after a wear test for 200,000 cycles (p<0.05). It is suggested that the resin composites containing fillers modified with the novel hydrophobic silane has high wear resistant, because of the coupling layers treated with this silane had an excellent affinity with the base resin and formed a highly hydrophobic layer on the filler surface.

Basic study of a new soft resin applied with bisfunctional siloxane oligomer.

To make a base polymer of a new soft resin material, a copolymer of 1,3-Bis(methacryloxypropyl)tetramethyl disiloxane (BMPMS) and methyl methacrylate monomer (MMA) was investigated. It was found that the compressive strength, bending strength and bending modulus value of the copolymer decreased with increase in BMPMS concentration. While, transverse deflection increased with increase in BMPMS concentration. As for the 50% inhibitory concentration value, it was about 0.8 mM for BMPMS.

Synthesis of new silane coupling agents with a trimellitic anhydride group and application as primers for ceramics and alloys.

With a view to improving the bond strength of resin to dental ceramics and alloys, new silane coupling agents, namely 4-trichlorosilylpropyl- and 4-trimethoxysilylpropyl-trimellitic anhydride (4-CSTA and 4-MSTA, respectively), were synthesized. In addition, silane mixtures of 4-CSTA with 3-methacryloyloxypropyltrimethoxysilane (3-MPS) and 4-MSTA with 3-MPS were used as primers for adhesion of poly (methyl methacrylate) to glass, silver-palladium-gold alloy (Ag-Pd alloy), and cobalt-chromium alloy (Co-Cr alloy). The tensile bond strengths of resin to glass using 4-CSTA+3-MPS and 4-MSTA+3-MPS were 28.5 +/- 5.3 and 23.9 +/- 8.1 MPa respectively. With the metal alloys, the strengths were 14.8 +/- 5.3 MPa for Ag-Pd alloy and 24.7 +/- 7.2 MPa for Co-Cr alloy. In the light of these results obtained, it seemed that the mixture of 4-MSTA and 3-MPS was an effective primer for both metals and ceramics.