Soichiro Kinuta

Mechanical properties of new self-adhesive resin-based cement

PURPOSE The aim of this study was to compare the bonding strength, flexural strength, elastic modulus, water absorption and the expansion after water storage of new self-adhesive resin cements to commercially available dental cements. METHODS Two types (hand-mix and auto-mix) of new self-adhesive resin cements (SAC-H and SAC-A, Kuraray Medical), one conventional resin cement (Panavia F2.0), three self-adhesive resin cements (Relyx Unicem, Maxcem and G-Cem), and two resin-modified glass-ionomer cements (Fuji Luting S and Vitremer) were used. Shear bond strengths, flexural strengths and elastic moduli (ISO 4049), water absorption (ISO 4049), and the expansion rate after water storage were investigated. RESULTS Both SAC-H and SAC-A provided adhesion to enamel and dentin, and had the same bond strength to gold alloy and zirconia as conventional resin cements. SAC-H and SAC-A had greater flexural strengths (86.4-93.5MPa) than commercial self-adhesive resin cements or glass-ionomer cements. The elastic moduli of self-adhesive and glass-ionomer cements were 5.2-7.4GPa and 2.3-3.4GPa, respectively. The water absorption of SAC-H and SAC-A (26.3-27.7microg/mm(3)) were significantly lower than commercial self-adhesive resin cements. SAC-H and SAC-A showed significantly lower expansion rates (0.17-0.26%) than commercial self-adhesive cements and glass-ionomer cements after 4 weeks water storage. CONCLUSIONS It is suggested that the new self-adhesive resin cements exhibited a favorable bonding capability and mechanical properties.

Tensile bond strength between tooth-colored porcelain and sandblasted zirconia framework

PURPOSE The purpose of this study was to examine the bond strength between tooth-colored porcelain and sandblasted zirconia framework. METHODS The surfaces of zirconia specimens that had been cut into a size suitable for a bending test were sandblasted at three different pressures (0.2, 0.4 and 0.6MPa). The surface roughness of each specimen was measured and then a 3-point bending test was performed. After that, other zirconia specimens simulating a crown framework were fabricated and their surfaces were sandblasted. Three types of tooth-colored porcelain were fired onto the surface of those zirconia specimens, and the tensile bond strength between the two substances was examined. RESULTS When the sandblasting pressure was increased, the surface roughness of zirconia specimens tended to become, but the flexural strength remained unchanged. The specimens simulating a zirconia framework had a higher strength of bond when sandblasted at 0.4 or 0.6MPa than when blasted at 0.2MPa. The zirconia specimens sandblasted at a pressure of 0.4MPa had a bond strength to tooth-colored porcelain of 37.7-49.5MPa. CONCLUSION When sandblasted at a pressure of 0.4MPa, the zirconia specimens developed a strong bond with the tooth-colored porcelain, regardless of the type of porcelain.