Study On Substitution Of Opaque Porcelain By Micro-Arc Oxidation On Ti-Based Porcelain Crown Surface

The oxidation film formed by micro-arc oxidation (MAO) was coating on pure titanium as the opaque porcelain in the structure of porcelain titanium restoration. It is important that it can reduce the amount of tooth when preparing tooth for full crown. The technique was used to enhance the adhesion of porcelain with titanium, and simplify the process of porcelain.MAO process was performed on TA2 allay surface to form a ceramic coating in electrolyte of K2ZrF6 and H3PO4 using impulse power supply. Surface morphology, section morphology, phase composition of oxide film had been systematically investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The shearing strength and bending strength of oxide film have been investigated by means of shearing test and three-point bending test.The results showed that the Cu and Mg element were incorporated into the oxide film during micro-arc oxidation process. The concentrations of Cu and Mg increased with the extension of oxidation time. The colors of the oxide film were changed with different concentrations of Cu and Mg in it. The color of film was gray after 5 minutes oxidation. It was low brown after 10 minutes oxidation. It was grown after 30 minutes oxidation. The aperture in the surface of ceramic coating was growing with the increasing of the density of solution. Adding Cu and Mg in the solution can not only change the color of oxidation film, boost more rutile in the coating were exchanged from anatase and formed new phase (Zr2P2O7,KZr2(PO4)3).The number of micro aperture was growing sharply with increased oxidation time. The diameter of aperture added, the surface became more roughly, and non-crystalline phase changed into crystalline phase with the time passing by. If the current density was increased, the roughness of surface was increase. The micro-crack was found with higher density of current.The shearing strength of oxidation film with TA2 was declined with the oxidation time increase. The shearing strength was 19.97MPa after 10 minutes oxidation. The shearing strength was 14.36MPa after 30 minutes reaction. The shearing strength of oxidation film with TA2 was increased with the density of current increased. When the density is 5A/dm2, the shearing strength was 18.35MPa. The shearing strength was 19.97MPa with 8A/dm2. The shearing strength was 22.84MPa with density of 11A/dm2.The bending strength of oxidation film was decreased with oxidation time increased. The bending strength was 36.9MPa after 5 minutes oxidation. The bending strength was 35.8MPa after 20 minutes oxidation. Bending strength was 35.4MPa after 30 minutes oxidation. Bending strength of oxidation film was higher enough to perform as opaque porcelain. The underline of bending strength is 25MPa.In different electrolyte, the change of bending strength with oxidation time was different. The bending strength of ceramic film was increased slightly in electrolyte of K2ZrF6 and H3PO4. The strength was about 37.4MPa. The bending strength was decreased with the time passing by, if the coating was formed in the electrolyte adding Cu and Mg. The tendency is different with different density of electrolyte. The decreased trend was more slowly in the electrolyte with 3:1 of Cu and Mg than in the electrolyte with 2:1 of Cu and Mg. The oxidation film was ruptured in the coating, but the bending strength was higher than 25MPa. The ceramic film can meet the request about bending strength.