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 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.

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.

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.