This study investigates the effects of enamel shapes and bracket configurations on the shear bond strength of a resin-modified glass ionomer cement. The shear bond strength was measured for the cement with which orthodontic brackets having curved and plane base surfaces were glued onto polished bovine, polished human and non-polished human enamels. The results showed no significant difference between human and bovine enamels and polished and non-polished ones. The shear bond strength of the cement between a plane bracket and bovine incisor reached more than doubled that between a non-polished human premolar and a curved bracket. This implies that the shape of the bracket-cement-enamel adhesion system, and the enamel shape especially, plays an important role in determining the shear bond strength of the orthodontic adhesives.

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In order to evaluate the mechanical properties of high elastic polyaddition-type silicone impression materials, the components and mechanical properties of hardening objects (i.e., hardness, compression set, and dynamic viscoelasticity) were investigated. The main components of these materials did not differ from previously tested materials of the same type. They showed a lower hardness and an equal or larger compression set than previous materials. In a dynamic test, they showed a smaller storage modulus and a larger loss tangent than previous materials. The softness of a hardening object is thought to be related to the combination of filler and prepolymer. The present findings indicate that the softness of the materials tested would allow them to be easily removed from the mouth or from a gypsum cast in a clinical setting. When stressed, they may have a greater permanent deformation than previous materials.

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The aim of the present research was to develop a new dental titanium alloy with good castability and biocompatibility. Since Zr is known to have good biocompatibility and form a continuous solid solution with Ti, we selected Zr as an additive element. Also, Sn is expected to have the stabilizing effect of the alpha-phase. Based on this information, we prepared ternary Ti-Zr-Sn alloys with different compositions. Castability, porosity, tensile strength, and crystal structure of the experimental Ti-Zr-Sn alloys were examined. The results showed that the Ti-Zr-Sn alloys possess excellent castability and tensile strength exceeding twice that of pure Ti. This evidence suggests that Ti-Zr-Sn alloys can be used as dental casting alloys.

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To improve the water resistance of the polysiloxane at the silica-resin interface, 3-methacryloyloxypropyltrimethoxysilane (3-MPS), 3-methacryloyloxypropyltriisocyanatosilane (3-MPI), 3-methacryloyloxypropyltrichlorosilane (3-MPC) and silane coupling agents containing a hydrophobic phenyl group such as 3-(4-methacryloyloxyphenyl) propyltrimethoxysilane (p-MBS), 3-(4-methacryloyloxyphenyl) propyltriisocyanatosilane (p-MBI) and 3-(4-methacryloyloxyphenyl) propyltrichlorosilane (p-MBC) were used. The tensile bond strength of the resin cement and the contact angles of a monomer mixture (50%Bis-GMA, 50%TEGDMA) to the ceramic teeth modified with each silane were measured. The tensile bond strength of the resin cement to the ceramic teeth modified with 3-MPC and p-MBC after thermal stress showed no significant decrease compared with a sample kept at room temperature for 1 day. The contact angles of the monomer to the ceramic teeth modified with 3-MPI, 3-MPC, p-MBS, p-MBI or p-MBC were significantly lower compared with 3-MPS. It was suggested that silane coupling agents with chloro groups as hydrolyzable groups had high water resistance ability at the silica-resin interface.

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Physical properties of the LTV silicone rubber denture relining material: SS-Silicone and its tensile shear bond strength to denture base resin after thermal cycling (TC) for 10000 cycles were investigated. SS-Silicone is an LTV type silicone-rubber and uses a mixture of silicone paste and dough resin as a binding material layer. Physical properties investigated were shore hardness: 60.5 at TC-0 and 64.7 after TC-10000, tensile strength: 7.30MPa at TC-0 and 6.98MPa after TC-10000 and tear strength: 39.86kN/m at TC-0 and 39.21kN/m after TC-10000. Tensile shear bond strength to heat-cured resin was 1.30MPa at TC-0 and 1.13MPa after TC-10000. The physical and adhesive properties of SS- Silicone were stable, even after thermal cycling.

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