[Quantitative monomolecular coverage of barium glass by the silane coupling agent gamma-methacryloxypropyltrimethoxysilane].

OBJECTIVE: To study the monomolecular coverage of the silane coupling agent gamma-methacryloxypropyltrimethoxysilane (gamma-MPS) on the barium glass filler surface. METHODS: Kubelka-Munk (K-M) function values of the isolated OH-groups on the barium glass filler surface, which were based on the change of gamma-MPS concentrations, were measured using the quantitative analysis of the diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. When all of the isolated OH-groups on the filler surface disappeared (where the K-M function values was zero), the monomolecular coverage of the gamma-MPS molecules on the filler surface was indicated by the linear regression analysis. RESULTS: The relationship tallied with negative linear correlation between the K-M function values of the isolated OH-groups on the barium glass surface and the concentrations of gamma-MPS. Each gamma-MPS molecule occupied 0.21 nm(2) when the monomolecular coverage was formed on the barium glass surface. CONCLUSIONS: The result of this study indicated the optimal amount of silane coupling agent on silanated barium glass filler during the production of resin composite.

[Effect of particle size distribution of dental poly (methyl methacrylate) beads on the microstructure of denture].

OBJECTIVES: To investigate the effect of particle size distribution (PSD) of dental poly (methyl methacrylate) (PMMA) beads on the microstructure of denture. METHODS: It was compared and analyzed that the porosity of three groups of spherical specimens which were made of PMMA beads with different PSD at proper polymer/monomer ratios. And the final microstructure of each group was investigated using Digital High Definition Microscope. RESULTS: With proper polymer/monomer ratio increasing, the occurrence of porosity tended to decrease. The final microstructure of denture varied with PSD of PMMA beads. CONCLUSION: By means of optimizing PSD of beads, the microstructure of denture could be improved, and the occurrence of porosity could be reduced.

[Rheological properties of photo-polymerized composite resin reinforced with retentive filler].

OBJECTIVE: To determine the rheological properties of the photo-polymerized composite resin reinforced with retentive filler (RF) and its rheological difference with normal filler (NF) composite resin. METHODS: Rheological properties of the composite resins, such as viscosity, shear stress and creep compliance, were measured with dynamic stress rheometer at room temperature (25 degrees C). RESULTS: The viscosity of the composite resin reinforced with RF is higher than that of NF composite resin (P < 0.01); at the beginning, the viscosity of the former has little change with the rising of shear stress and the latter decreases, then the viscosities of the two composite resins increase with the rising of shear stress as soon as over 203.18 Pa of shear stress; the creep compliance of the composite resin reinforced with RF is significant smaller than that of NF composite resin (P < 0.01). CONCLUSIONS: The rheological properties of the two composite resins have significant difference, so they have different clinical using properties.

The directionality of share adhesive strength between composite resin and dental hard tissue.

OBJECTIVE: To inspect the directionality of adhesive strength between composite resins and dental hard tissues. METHODS: Two kinds of composite resins were bonded with their luting kits to the enamel and dentin surfaces of bovine teeth separately. The dead load shear and impact shear testing were performed from both of root apex direction and cutting edge direction. RESULTS: The shear adhesive strength between the enamel and two kinds of composite resins was on the same behavior, that the shear adhesive strength of root apex direction was greater than that of cutting edge direction. In the dead load shear testing, the former was about two to three times of the latter (P < 0.05). In the impact shear testing, the former was about three to four times of the latter (P < 0.001). The effect of the direction of acting force was small on the shear adhesive strength between the dentin and two kinds of composite resins. In the both dead load shear testing and impact shear testing, there was no statistically significant difference between the datum of two directional loadings (P > 0.05, P > 0.5). CONCLUSION: The shear adhesive strength between the composite resins and enamel of bovine teeth is related to the acting direction of the shear force.