GB911549A - Construction of artificial dentures - Google Patents

Abstract

911,549. Dental flasks. SMITH, C. C. May 19, 1959, No. 16901/59. Class 87(2) A dental flask 18 comprises two sections 16 and 28, the lower 16 of which contains a lower mould section 14 and a positive cast 12 of the user's mouth while the upper 28 contains an upper mould section 26 of porous material in which the teeth 24 are embedded. The cast 12, mould section 26 and the opposed peripheral edges of the flask sections are preferably coated with an alginate separating medium to facilitate removal of the completed denture and then section 26 is packed with a polymeric, e.g. acrylic resin, denture base material 38, after which the flask and mould sections are assembled and compressed between the pressure head 62 and base platen 46 of a press. A second flask 72 may also be compressed at the same time, being placed between the head 62 and the flask 18. The material 38 distributes evenly over the cast 12 and flashes outwardly between the edges of the mould sections 14, 26 and the flask sections 16, 28. The latter are provided with opposed annular grooves 40, 42 to receive the flask, this not only presenting a positive seal but also holding the material 38 in place against radial inward slippage that would otherwise occur during shrinkage as a result of polymerisation. A manifold 74 interposed between the flasks 18, 72 has a central port 78 surrounding the opening 36 in the cover 30 of flask section 28. Water is forced into the flasks 18, 72 through the inlet 122 and maintained under pressure while the material 38 is heated by elements within the pressure head 62 and platen 46. The water penetrates the porous mould section 26 and presses the material 38 tightly against the cast 12 during its polymerisation, thus preventing shrinkage and consequent pulling away from the pattern 12 with a consequent misfit. Where only a partial denture is to be made, the cast 12 and section 14 must be made impermeable to the flow of water, this not being necessary where the material 38 forms a complete seal as in the embodiment described above. Cooling should be carried out slowly after the polymerisation is completed, for example by means of passages in the manifold 74, through which a coolant is passed. The mould section 26 and the completed denture are removed from the flask section 28, and the mould section 14 and cast 12 from the flask section 16, by means of a frustoconical knockout tool 34 attached to the pressure head 62 as shown in Figs. 10, 11, the flask sections being supported on pins 124 upstanding from the platen 46.