Formation of New Functionally Graded Biomaterial Composed of Ceramics or High-polymer with the Porous Structure on Gold Alloys

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During the past decade, clinicians and patients have grown increasingly interested in posterior composite resins. Much of this interest has resulted from a desire for esthetic restorations. The purpose of this study was to improve bonding between dental adhesive resins or ceramics with gold alloy by creating a porous structure on the alloy surface, which enhanced mechanical bonding.The internal oxidation particles of Cu oxides precipitated in a 14K gold alloy surface after high-temperature oxidation at 800ーC in air were removed by pickling with an acid solution to create a sponge-like structure on the alloy surface. A PMMA resin containing 4-META as an adhesive monomer and a self-cured resin without 4-META were used to examine the effects of mechanical and chemical factors on bond strength. A thiophosphate-type metal primer (M-Primer II) was used in combination with 4-META resin to strengthen the chemical bonding of 4-META resin to the porous alloy surface. The surfaces of the alloy specimen treated by oxidation, pickling, and bonding with 4-META resin were analyzed using an electron probe X-ray micro-analyzer. SEM observation showed many resin tags on the resin side of the bond structure after removal of the gold alloy matrix with aqua regia. The porous structure on alloy surface is effective to increase the mechanical bond strength with dental adhesive resin, resulting that the bond strength with the porous structure is twice more than without the porous structure. The technique can apply for formation of an esthetic restoration.The porous structure was immersed in a solution containing Ca^<2+> and PO_4^<-3>. Hydroxyapatite was precipitated in the porous structure. The technology creating porous structure on the gold alloy is useful for forming implant structure embedded in a jawbone. Further research is needed in application for clinical use with the porous structure technology.