Abstract: A measuring center stores three-dimensional coordinate information of an intra-oral shape measured by impression taking as a digital signal. The measuring center sends the obtained measured data to a design center using communication apparatus. The design center reproduces the intra-oral shape on a graphic display device based on the received measuring data as a three-dimensional graphic, designs a shape of a dental prosthesis and stores it as a digital signal. The processing center transmits the received design data to a milling processor as a processing command and subjects a block material to milling processing to prepare a dental prosthesis.

Abstract: To prepare a dental prosthesis that has a shape exactly the same as in the form at the time of sound state, with superior intra-oral fitness precision, a process for preparing a dental prosthesis utilizing a CAD/CAM system includes subjecting three-dimensional coordinate information of an intra-oral shape measured by impression taking or by photographing within an oral cavity of a patient, to three-dimensional graphic display on a graphic display device and designing a dental prosthesis on the three-dimensional graphic, wherein three-dimensional coordinate information of a previously preserved intra-oral shape of a patient at the time of sound state is subjected to graphic display simultaneously on the graphic display device; the dental prosthesis of an objective tooth is designed so as to have a shape same as the shape at the time of sound state; the obtained design data of the dental prosthesis is transmitted to a milling processor as a processing command; and a block material is subjected to milling proces

Abstract: To prepare a dental prosthesis that has a shape exactly the same as in the form at the time of sound state, with superior intra-oral fitness precision, a process for preparing a dental prosthesis utilizing a CAD/CAM system includes subjecting three-dimensional coordinate information of an intra-oral shape measured by impression taking or by photographing within an oral cavity of a patient, to three-dimensional graphic display on a graphic display device and designing a dental prosthesis on the three-dimensional graphic, wherein three-dimensional coordinate information of a previously preserved intra-oral shape of a patient at the time of sound state is subjected to graphic display simultaneously on the graphic display device; the dental prosthesis of an objective tooth is designed so as to have a shape same as the shape at the time of sound state; the obtained design data of the dental prosthesis is transmitted to a milling processor as a processing command; and a block material is subjected to milling proces

Abstract: To overcome the difficulty in designing a dental prosthesis, which is the most fatal problem of the conventional art process for preparing a dental prosthesis of high precision and superior intra-oral fitness by a CAD/CAM system, a measuring center stores three-dimensional coordinate information of an intra-oral shape measured by impression taking or by photographing within an oral cavity of a patient, as a digital signal and sends the obtained measure data to a design center using communication means; the design center reproduces the intra-oral shape on a graphic display device based on the received measuring data by means of a three-dimensional graphic, designs a shape of a dental prosthesis and stores it as a digital signal, and then sends the obtained design data of the dental prosthesis to a processing center using communication means; and the processing center transmits the received design data to a milling process or as a processing command and subjects a block material to milling processing to prepare

Abstract: A dental gypsum bonded investment composition comprising 100 parts by weight of a mixture comprising (a) .alpha.-hemihydrate gypsum as a binder and (b) quartz and/or cristobalite as a refractory material, and optionally, (c) one or more aggregates selected from the group consisting of metallic oxides, metallic carbides, and metallic nitrides, which can substitute a part of the refractory material, having from 0.01 to 1.0 part by weight of a poly-tetrafluoroethylene resin and optionally, from 0.001 to 0.05 part by weight of one or more anionic surfactants selected from the group consisting of alkylbenzenesulfonates and alkylsulfates mixed therewith, is disclosed. The dental gypsum bonded investment composition of the invention keeps the fine particles to have a stable performance without being removed by the pneumatic transportation at the time of production, has superior heat resistance, and can be used for casting of alloys having a high melting point such as casting alloys for metalceramic restorations.

Abstract: A method for casting dental metals with a casting apparatus including a hermetically sealed casting chamber in which an arc electrode is located above, a crucible made of an electrically conductive material is positioned below the arc electrode, and a mold provided with a closed vent is disposed below the crucible, the method including by positioning a dental metal ingot on the crucible, evacuating the casting chamber to vacuum, feeding a small amount of an inert gas at such a pressure as to induce arc discharge all over the upper surface of the ingot, thereby melting the ingot placed on the crucible by arc discharge from the arc electrode, pouring the thus obtained molten metal into a mold through its inlet, and immediately feeding an additional amount of the inert gas into the casting chamber to increase its internal pressure to a level suitable for casting. Also the additional amount of the inert gas is rapidly fed into the casting chamber through a gas tank in the vicinity of the casting chamber.

Abstract: A method for casting dental metals with a casting apparatus including a melting chamber in which there are located an arc electrode above and a crucible formed of an electrically conductive material positioned below the arc electrode, and a mold chamber divided from the melting chamber by a partition wall having a through-hole at a position below the crucible and housing a mold box receiving a mold provided with an extending open vent positioned below the through-hole, the melting chamber communicating hermetically with the mold chamber through the mold, which is characterized by positioning a dental metal ingot on the crucible, vacuumizing the melting and mold chambers, feeding a small amount of an inert gas into the melting chamber at such a pressure as to induce arc discharge all over the upper surface of the ingot, thereby melting the ingot placed on the crucible by arc discharge from the arc electrode, pouring the thus obtained molten metal into the mold through its inlet, and immediately feeding an addi