Evaluation Of Bond Characteristics Between Porcelain And Titanium Fabricated By Laser Rapid Forming

Laser rapid forming (LRF) technology has been introduced into fabrication of metal prosthesis, which can fabricate without molds rapidly. Compared to LRF technology, there are many problems for precision investment casting such as complicated procedure, casting defects, and for numerical control milling which can not fabricate complicated shape restoration. LRF technology has shown out high potential in fabrication of metal prosthesis. The object of this experimental study is to probe the feasibility of fusing porcelain to titanium fabricated by LRF and the effect of surface treatment to bond characteristics, in order to make the foundation for the LRF application in dentistry in the future.Method:1. Titanium specimens were fabricated using commercial titanium powder and laser rapid forming system. The coefficient of thermal expansion (CTE) of LRF Ti was evaluated. The bond strength was analyzed with three-point-bonding test according to ISO9693 standard.2. The surface roughness (Ra), contact angles and bond strength of titanium/porcelain were evaluated after using the different size of Al2O3 (50|m, 120|m, 250|m) to rough the titanium surface.3. The surface roughness (Ra), contact angles and bond strength of titanium/porcelain were evaluated after using the different solutions (5%HF, 35%HNO3, 50%NaOH) to modify the titanium surface.4. The surface roughness (Ra), contact angles, crystal phase and bond strength of titanium/porcelain were evaluated after using the different preoxidation temperatures (700℃, 750℃, 800℃, 850℃) to modify the titanium surface.5. The titanium specimens were treated using electro-spark deposition (ESD) technology. The effect of different parameters of ESD on the bond characteristics of LRF Ti by changing electrode material, reaction media, voltage and mode were investigated. In the end, the optimized parameters of ESD were selected according to the titanium/porcelain bonding strength.Results:1. The result of CTE test showed that the Ti-22 porcelain had an ideal thermal compatibility with LRF Ti. The difference between porcelain and LRF Ti was 0.86(?)10 -6(?)℃-1. The bond strength of porcelain and LRF Ti was above the lower limit value in the ISO9693 Standard (25MPa)2. When using the larger size of Al2O3, the value of Ra and contact angle increased. The bond strength of LRF Ti and porcelain was higher after using 50|m Al 2O3 sandblasting than using 120|m and 250|m Al 2O3 sandblasting under the same pressure.3. The value of Ra was increased after treated with 5% HF, which was not significantly changed after treated with the other solutions. The value of contact angle was significantly decreased after treated with 50% NaOH. Bond strength between porcelain and LRF Ti can be increased by use of a 50% NaOH caustic bath prior to porcelain firing.4. The roughness was decreased and the contact angle was not significantly changed after preoxidation. With increasing temperature, the diffraction peaks ofα-Ti were weakened, and that of rutile TiO2 were enhanced. When titanium subjected to preoxidation treatment at 800(?)C, the bond strength was higher when compared to treatment at 700(?)C, 750(?)C and 850(?)C.5. The bond strength was significantly increased after treated by ESD at Si electrode, air media, 70V/60V/50V/40V voltage and gradient treatment mode (36.11(?)2.43MPa) . The crystal phase of deposition layer was mainly composed of Si, TiSi2 and Ti5Si3.Conclusion:1. The bond strength of porcelain and LRF Ti was above the lower limit value in the ISO9693 Standard (25MPa). The bond strength (32.38(?)2.43MPa) after treated with 50|m Al 2O3 sandblasting, 50%NaOH and 800(?)C preoxidation was significantly higher than that of the untreated group (25.91(?)1.02MPa).2. The bond strength of porcelain and LRF Ti can be increased after treated by ESD technology. The ESD coating as an interlayer between porcelain and titanium showed out favorable application prospects.