Fabrication of dental prosthetic appliances with slip casting

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The first stage: The purpose of this study was to examine slip casting of titanium powder as a method for manufacturing dental prosthetic appliances. Three Slips were prepared by mixing 71.59〜73.59% titanium powder, 26.03〜28.03% water and 0.38% sodium alginate by weight. Each slip with minimum viscosity was poured into the mold, adjusting pH of the slip with 3N-HCI solution. Green strength was examined 2.31〜3.82 Mpa. Relative green densities of the castings were 0.49. Sintering shrinkages were 16.7〜20.8% when sintering temperatures of 1100〜1300℃ were adopted with sintering times of 1〜3 hrs in argon. Relative densities of the materials were 0.86〜0.97. Tensile strengths of the sintered materials were 241.5〜259.5 Mpa. O, C and Na was observed in metallurgical structures of the materials.The second stage: The thermal expansions (%) were 12.4, 10.6, 8.0 at 1125℃ for three mold materials of (A) 45%AlィイD22ィエD2OィイD23ィエD2 - 45%BaCOィイD23ィエD2 - 10%Titavest ME, (B) 40%AlィイD22ィエD2OィイD23ィエD2 - 40%BaCOィイD23ィエD2 -20%Titavest ME and c 35%AlィイD22ィエD2OィイD23ィエD2 35%BaCOィイD23ィエD2-30%Titavest ME. Titavest ME is a commercial mold material for dental casting of titanium. Wax patterns of dental single crowns were invested using the three mold materials. The molds were heated to 1125℃ with burning of the patterns. The composition of a slip is 73.61% Ti powder, 26.01% water, 0.38% sodium alginate. The slip was poured into the molds with dental centrifugal casting machine. The slip-cast compacts were sintered at 1100℃ for 3 hrs in a vacuum of 1.5×10ィイD1-5ィエD1 torr together with the molds. The dimensional accuracy of sintered crowns was examined with the distance between the cervical margin of a sintered crown and the shoulder of an artificial abutment. The distances were 1,425 μ, 171 μ, 124 μ for the molds of (A), (B) and c. The accuracy decreased with increasing thermal expansions of the molds. Further the elimination of slip casting defects and higher vacuum for sintereing were needed.