Abstract: A method of destroying a brittle body by molding around an elastic tube or an elastic tube in which is inserted a plastic wire or a heat-fusible member for defining a charging hole where the member or tube is partly exposed at the surface of the brittle body, and, after pulling out the elastic tube or fusing the heat-fusible member, an expandable splitting agent capable of expanding by hydration is charged into the charging hole and subjected to hydration-expansion to destroy the brittle body. In another form, a water-impermeable film enclosing an expandable splitting agent capable of expanding by hydration therein is previously buried in a brittle body in a relation partly exposed at the surface of the brittle body, and, after aperturing the exposed end of the water-impermeable film, the expandable splitting agent is subjected to hydration-expansion to destroy the brittle body.

Abstract: Disclosed is a new urethane polyacrylate having at least one terminal isocyanato acrylic pendent radical. Preferably the molecular chain within the acrylate caps has been extended with a polyhydroxy compound just before final end capping with isocyanato acrylic. The isocyanato acrylic is preferably isocyanato ethyl methacrylate and the urethane is diisocyanate capped polyether and the polyether radical is oxyalkylene. The method for producing the urethane polyacrylate involves end capping a polyol with diisocyanate yielding a reaction product with two reactive equivalents of isocyanate and then capping less than all of the isocyanate with a hydroxyacrylate, after which the remaining isocyanate is reacted with polyol to provide chain extension. The chain extending polyol is then capped with a isocyanato acrylic.

Abstract: A polyarylenethioether primary melt formed article having a Hunter whiteness higher than 30% and a parallel light transmittance Tp higher than 60%, as measured for a sheet with a thickness of 0.3 mm, at the process for obtaining the article which comprises producing a polyarylenethioether according to the polymerization reaction comprising a dehalogenation/sulfidization reaction between an alkali metal sulfide and a dihaloaromatic compound in a polar organic solvent by carrying out the reaction with the addition of an effective amount of a halo-substituted organic compound to obtain a stabilized polyarylenethioether, and then subjecting the polyarylenethioether to melt extrusion. The melt formed article thus produced can be subjected to further melt processing to produce a secondary melt formed article or structure of polyarylenethioether.

Abstract: Control of speed and uniformity of the heating of the working zone of the preform in a glass drawing operation in which the softening heat is applied by forced convection (13), using a separate fluid heating zone to introduce temperature and velocity controlled fluid. The size of the working zone is further controlled by changing (18) the configuration of a movable exit sleeve. Uniformity and accuracy of temperature is enhanced by normalization (10) of the temperature of the preform close to a preselected value before the preform enters the furnace.A glass drawing apparatus embodies the preferred means to carry out the process, providing a two-chamber furnace having an air heating chamber (44) connected by air delivery channels (51) to a drawing chamber (43). The drawing chamber has preform inlet (41) and a drawn product outlet (56). Each of the latter preferably has an adjustable opening diameter. The inlet is provided with a pre-cooling collar (35).

Abstract: A dental impression composition is provided which has relatively lower water content for higher tensile and gel strengths, and an effective amount of dipopylene gylcol to offset the reduced amount of water and provide workability in the composition at storage tempering temperatures of as little as 130.degree. F.

Abstract: A novel process for providing a thermoplastic polymer having unique thermal characteristics including the step of cooling the polymer during extended mastication until the melt index of the polymer is substantially increased.

Abstract: Ethoxylated siloxane surfactants, and mixtures of such surfactants with curable silicone prepolymers. The mixtures are hydrophilic after cure, have semipermanent hydrophilicity, and are especially useful as dental impressions.

Abstract: Time-consuming steps of drying the unhardened and porous refractory dental model, hardening the dried model, and applying multiple coatings of a lacquer spray onto the hardened model are eliminated by spraying the unhardened and porous model with a non-viscous solution of specified cyanoacrylates to thereby produce a final model which yields a mold providing an improved alloy casting dental prosthesis.

Abstract: A dental prosthesis is formed by attaching an internally threaded sleeve to a post by means of heat-meltable material. A dimensionally stable, heat-meltable material is applied to the post and around the sleeve. The heat-meltable materials are melted and replaced by a permanent material. A screw is inserted into the sleeve prior to the melting step. The melting and replacing steps comprise steps in an investment-type casting procedure wherein a unit comprised of the post, the sleeve, the screw, and the heat-meltable materials is embedded in an investment material such that a head of the screw is embedded in the investment material to maintain the positional relationship of the sleeve relative to the post during the melting step. A release material is applied over a body defined by the permanent material.

Abstract: The invention relates to a method of manufacturing a cable. In the cable, the conductors are surrounded entirely or partly by synthetic resin supporting elements. In order to avoid shrinkage of the supporting elements, and hence extra loads on cable at high temperatures, the supporting elements are preshrunk before assembly of the cable. The elements are preshrunk by heating a temperature just below the softening temperature of the synthetic resin in question, maintaining them at this temperature, and then cooling them. During the heating process, the strength elements are mounted in such a way that their contraction will not put them into tension.

Abstract: A device and method for forming a removable die within a stone cast of a dental arch is presented. The die is attached to one end of a curved dowel pin which in turn slides into a curved channel in the base of the stone cast. The unique curved path of insertion and removal allow the die to be repositioned accurately and held securely with a single dowel.

Abstract: A method of making an optically clear custom tooth positioning and retaining appliance in a flask or mold device having mold members from an elastomeric or resilient thermoplastic material with the capability of having optically clear transparentness, after the appliance has been trimmed and/or buff polished subsequent to molding thereof which causes the appliance to have a frosty or translucent appearance, which method includes subjecting the exterior surfaces of the appliance to a source of concentrated heat to cause surface melting which produces transparentness, cooling the appliance before, during and after heating as needed to preserve its integrity, and optionally utilizing the mold members from the flask or reproductions thereof in the archways of the appliance during heating thereof.

Abstract: A dental fastening device is disclosed for fastening a wax substructure of a subsequently fabricated dental bridge adjacent to a first and second dental die during the fabrication and shaping of the wax coping or substructure. The substructure includes a pontic portion disposed between a first and a second abutment portion. The fastening device inhibits relative movement between the pontic and abutment portions during solidification and shrinkage of the substructure. The fastening device comprises a first elongate tie down member having a first and a second end. The first end of the first tie down member is anchored to the lingual face of a cast adjacent to the first die and the second end of the first tie down member is anchored to the buccal face of the cast adjacent to the first die. The first tie down member extends from the lingual face of the cast over the occlusal surface of the first abutment portion and around the buccal face of the cast.

Abstract: Method and apparatus for forming tooth positioners. The apparatus includes a pair of aligned model mounts which are relatively movable toward each other, a holding member between the mounts having a cavity for a positioner blank, a heating element embedded in the holding member, and a sandwiching pressure applicator. Preferred embodiments include a carrier member with which the holding member is removably engageable. The method includes heating the holding member by applying heat internally to it and applying sandwiching pressure to the blank, preferably concurrently.

Abstract: A denture with a metallic microstructure and with low shrinkage and porosity is produced by metallurgical sintering by providing a multimodal size distribution of coarse and fine fractions of metal powder, optionally also with glass or ceramic powder, converting this powder mixture with water into a slip, modelling the denture with this, and sintering the slip at a temperature which exceeds the solidus temperature of at least one component of the powder mixture.

Abstract: A plastic optical fiber comprising a core of a copolymer of an aryl methacrylate and an alkyl methacrylate and a cladding of a copolymer of vinylidene fluoride and a fluoroolefin provided on the core, the copolymer of the cladding having a melting point of at least 120.degree. C. and a fluoroolefin content of at least 3 mol %.

Abstract: Curable silicon prepolymers are made hydrophilic after cure by mixing the prepolymer with ethoxylated nonionic surface active agent or cationic or amphoteric fluorochemical surface active agent. The cured silicones have semipermanent hydrophilicity and are especially useful as dental impressions.

Abstract: A novel process for providing a thermoplastic polymer having novel thermal characteristics including the critical step of masticating the polymer, either continuously or discontinuously, until the melt index of the polymer is substantially increased.

Abstract: A mold for preparing a plug suitable for making a dental shade sample having a layer of porcelain material having a known thickness; the mold comprises: a base with a cylinder extending upwardly therefrom; a planar platform surface at the upper end of the cylinder, the cylinder being threaded in a region below the platform surface; and a hollow annular housing defining an internal cylindrical surface sized and cooperatively threaded to engage the cylinder threads. Rotation of the housing relative to the cylinder moves the housing vertically and continuously varies the known depth of the cavity between the housing and the platform surface. By proper positioning of the housing and cylinder a known desired cavity depth is obtained and filled with porcelain-forming material to mold a first shade layer. The housing is rotated to increase the cavity depth by known desired increments for subsequent layers.

Abstract: Disclosed herein are an improved method and apparatus for continuously embossing a repeating pattern of precise detail, in particular, cube-corner type reflector elements, on one surface of a single sheet or on one surface of a laminate of transparent thermoplastic materials, to form retroreflective sheeting. A continuous embossing tool in the form of a flexible thin metal belt or cylinder has on its outer surface an embossing pattern which is the reverse of the precision optical pattern to be formed. The embossing tool is continously moved at a predetermined speed along a closed course through a heating station where the temperature of a portion of the embossing tool is raised to be above the glass transition temperature of the sheeting or laminate and a cooling station where the heated portion of the embossing tool is cooled while in a relatively planar condition to be below that glass transition temperature.

Abstract: A die material particularly suitable for the making of castings or the like, comprises 50 to 80 parts of magnesium oxide, 10-40 parts of alumina, 2 to 6 parts of monohydrated ammonium phosphate, and 1 to 4 parts of dihydrated ammonium phosphate. The dry blend thus formed, when mixed with a chilled liquid binder containing a collodial silica sol of about 40 weight percent solids content in the ratio of one portion of the liquid binder and from 2 to 5 portions of the dry blend, forms a ceramic slurry which can be readily set in hot water within 4 to 10 minutes. The set ceramic casting is then dry heated to about 250.degree. F. for one to two hours. Molten metal is then applied on the casting for forming a metal jacket to use in dental prostheses.

Abstract: A method of producing a light transmitting article of synthetic resin by polymerizing incompletely a monomer Ma which forms a network polymer Pa having a refractive index Na, thereby forming a self-supporting body material, and subsequently diffusing a monomer Mb, which forms a polymer Pb having a refractive index Nb different from the refractive index Na, into said body material and simultaneously polymerizing said monomer Mb, wherein said method comprises steps of drawing out continuously a body material from a molding means in which said body material has been formed and is ready for the diffusion of the monomer Mb, and passing said body material through a diffusion means and a heating means one after the other, diffusing the monomer Mb into said body material by the aid of said diffusion means and then heating said body material by the aid of said heating means so that the distribution of said monomer Mb is fixed in said body material.

Abstract: An elongate trim strip comprising an elongate moulding, said moulding having a flat surface for receiving adhesive or otherwise attaching the strip to the body of a vehicle, a longitudinal channel formed in said moulding, a decorative surface in said channel and a weather-resistant and impact-resistant plastic overlay having radiused edges which provides a lens effect to the decorative surface beneath. Also a trim strip consisting essentially of an elongate decorative foil member having an upper surface and a lower surface and sharply defined peripheral edges, said upper surface having thereon a weather-resistant and impact-resistant overlay having radiused edges and providing a lens effect to said foil member, said overlay being formed by overcoating said upper surface of said foil member with a fluent clear plastic material which flows to said sharply defined peripheral edges and forms a positive meniscus and curing said plastic material.

Abstract: A method of making a dental prosthesis includes providing an upper or a lower impression of the oral cavity of a patient; and filling such impression with a castable mixture comprising (1) a ceramic composition containing a major proportion of magnesia and a significant minor proportion of alumina and (2) an aqueous composition containing silica as the essential ingredient, the ratio of the aqueous silica composition to the ceramic composition being such as to render the latter flowable. The mixture is then permitted to harden in the impression, and the resulting hardened model is removed from the impression. Thereafter, a liquefied metal composition is spray-coated on to a selected portion of the model to form a metallic prosthetic base, which is separated from the selected portion of the model and provided with a porcelain coating on its exterior surface.

Abstract: A porous implantable oral prosthesis which can be used to replicate and replace any hard tissue portion of the mouth such as bone and teeth is described. The prosthesis comprises sintered polymeric particles coated with a hydrophilic material. The polymeric particles vary in size so as to provide an area of relatively coarse porosity where the prosthesis is intended to interface with bone tissue and relatively fine porosity where it is intended to interface with soft tissue. A process for producing such prosthesis by filling a mold with appropriate molding compounds comprised of polymeric particles and a hydrophilic monomer, sintering the particles and polymerizing the monomer by dielectric heating, removing the sintered material from the cooled mold, and placing the prosthesis in a hot liquid to remove residues is described. An entire tooth, including a nonporous crown may be produced.

Abstract: Disclosed herein are a method and apparatus for continuously embossing a repeating pattern of precise detail, in particular, cube-corner type reflector elements, on one surface of a sheet of transparent thermoplastic material to form retroreflective sheeting. A continuous embossing tool in the form of a flexible thin metal belt or cylinder has on its outer surface an embossing pattern which is the reverse of the pattern to be formed. The embossing tool is continuously moved at a predetermined speed along a closed course through a heating station where the temperature of a portion of the embossing tool is raised to be above the glass transition temperature of the sheeting and a cooling station where the heated portion of the embossing tool is cooled to be below that glass transition temperature.

Abstract: Cylindrical embossing tools are constructed from one or more masters formed by accurately scribing the face of a substrate along three axes in the face to produce a pattern of tetrahedrons. The plurality of masters, or replicated copies made from a single master, are assembled in a fixture and seamless copies are made by electrodeposition of nickel using various shielding and grinding methods to provide replicated copies of uniform thickness. The replicated copies are assembled and used to form larger electroforms until a generally cylindrical embossing tool of the correct width and circumference is created. Novel processes and apparatus are provided for removing the electroformed cylindrical tool from its mother cylinder.

Abstract: A new method for producing retro-reflecting assemblies of the type comprising a transparent globule having an essentially part-spherical upper portion uncoated for light impingement, and a lower portion associated to a monolayer of focusing and reflective microspheres, the method comprising forming said globule by subjecting a sheet thermoplastic material to heat and pressure in the bite of counter-rotating forming rollers to provide an essentially planar intermediate product having oppositely located bulges at either faces thereof, the globules being obtained by subdividing said product in parts each comprising a pair of opposite bulges. The invention comprises improved assemblies comprising each an asymmetrical globule having the monolayer of microspheres associated to its essentially bottom face and to its peripheral toroidal side face of a radius of curvature smaller than that of its upper bulging portion exposed for light impingement.

Abstract: Tooth positioner comprising several integral tooth engaging portions formed of materials having different hardness, the harder portions of which assist in anchoring the tooth positioner in its proper position in the patient's mouth.Further, a method of making such tooth positioners by enclosing dental counterpart of the mold to form a first portion of the positioner, placing at least one other material into the mold in interfacing relation to the first portion to form a second portion of the tooth positioner, and curing the several materials into an integral body before extracting the positioner from the mold.

Abstract: Photopolymerizable composition, especially for dental purposes, which contains as photopolymerizable olefin compounds especially acrylic and/or methacrylic compounds as well as a ketone and an amine as activating substances. The amine has the general formula ##STR1## wherein the symbols have the following meanings: X represents cyan or halogen,R represents the group X--CH.sub.2 --CH.sub.2 -, an alkyl group of 1 to 6 carbon atoms, or a hydroxyl group of 2 to 6 carbon atoms, an acrylic, methacrylic or vinyl group, andR.sub.1 represents a substituted or unsubstituted phenyl, benzyl or styryl radical, orR and R.sub.1 together form an alkylene group of 4 to 5 carbon atoms, the amine being able to be present also in polymeric form if in the monomer R represents an acrylic, methacrylic or vinyl group and/or R.sub.1 represents the styryl radical.

Abstract: An acrylic laminated diffuser panel having a high light-diffusing property is provided, which comprises a laminate of an acrylic resin film having a high light-diffusing property and an acrylic resin plate, wherein the acrylic resin film is integrated with the acrylic resin plate. The acrylic laminated diffuser panel is prepared by laminating the acrylic resin film on the molding surface of at least one of a pair of casting mold parts, casting an acrylic monomer or its partially polymerized product into a space between said pair of casting mold parts, and then, polymerizing the acrylic monomer or the partially polymerized product.

Abstract: In order to produce a preform or parison from which an optical fiber can be drawn, a vitrifiable substance such as silicon chloride and a doping agent such as germanium chloride, for example, are fed in liquid form and at room temperature to a spray nozzle together with water or steam for continuous deposition on a relatively rotating and axially reciprocating inner or outer surface of a cylindrical support until that surface is covered with a heavy layer of as yet unvitrified hydrated silica admixed with the doping agent in proportions designed to provide a selected refractive-index profile. The resulting preform, after degassing and separation from the support if necessary, is freed from occluded water molecules by exposure to a flow of hot dehydrating gas which may contain anhydrous compounds and is thereafter collapsed into a solid rod and completely vitrified at high temperatures.

Abstract: A flat uniform thickness or flat sheet of thermoplastic material is heated to deformable, nonresilient, nonliquid condition, shaped over a built-up study model of the jaw ridge of a patient requiring a dental prosthesis and cooled to substantially rigid condition to form a custom dental impression tray.

Abstract: The invention relates to a process for producing reciprocal adhesion at the interface between two contacting layers of condensation crosslinking and addition crosslinking polysiloxanes, aluminum hydroxide being added to one or both polysiloxane layers prior to crosslinking, so that a firmly adhering joint is obtained.

Abstract: A method of producing a composite of organic resin and inorganic porous particles, preferably for use as a dental restoration material, which comprises impregnating porous inorganic particles with an at least partially hardenable resin material, compressing or otherwise applying pressure in such a way that the particles contact each other and the pressure in the resin is equalized by viscous flow of excess resin through the pores of the inorganic particles, bonding together by hardening of at least a portion of the hardenable resin material, thereby forming a resin structure including a contiguous inorganic phase.

Abstract: Methods for performing operations on a die or dental model including the filling in or "basing up" of voids, deep areas and undercuts; the indexing and investment soldering of dental crowns from a die model; and aid in the fabrication of porcelain jacket crowns and the like; the invention particularly contemplates the use of a cyanoacrylate compound to effect said methods. According to the present methods, a high viscosity cyanoacrylate base material, typically the methyl or ethyl ester of the cyanoacrylate is deposited on the die model in the areas which are to be based up, blocked out or the like, an activator or accelerator compound such as an aromatic amine or the like being then sprayed, preferably in an atomized mist form, onto the deposited base material.

Abstract: The bonding of smooth dental porcelain using glass-ionomer cement has hitherto been difficult. The present invention incorporates particles of an ion-leachable glass, particularly a calcium fluoroaluminosilicate glass, in the dental porcelain and improves the bonding properties.

Abstract: A transition device (10) is provided to facilitate the forming of a lightguide ribbon cable unit (22) from a plurality of individual insulated light conductors (24). The light conductors (24), which each include a light-conductive glass fiber (12) surrounded by an inner layer (14) of insulation and an outer layer (16) of insulation, are mounted into converging channels (44) of the transition device (10), such that portions of the glass fibers which have been stripped of insulation extend from an exit end (50) of the device arranged in a parallel side-by-side array between two strips of pressure-sensitive adhesive tapes (18 and 20) to form the ribbon cable unit (22). The assembled transition device (10), ribbon cable unit (22) and light conductors (24) produce an optical fiber assembly (93).

Abstract: A method of making a thermoplastic dental impression tray which can be heated, placed into the patient's mouth where it can be intimately molded to approximate the patient's tissues and characterized in that the tray will maintain its molded structure to a high degree of accuracy. Methyl methacrylate monomer liquid and polymer powder are mixed together and the mixture is allowed to reach a doughy state. The mixture is placed into a mold conforming to the desired structure of the tray. The mold is then heated for a sufficient time under pressure to polymerize the monomer to provide a tray characterized in that when heated to above 135.degree. F. it wil become soft enough so that it can be placed into the patient's mouth for intimate molding therein and which will become so hard when cooled in the mouth that it will exhibit a recovery rate of less than 2% after removal from the mouth so that the precision of the impression is accurately maintained.

Abstract: There are disclosed an apparatus to perform a method for continuously embossing synthetic plastic sheet material with precisely formed embossments in patterns repeating along the length thereof. The apparatus includes a movable polished belt upon which the sheet material is carried, and a series of molds are placed on the sheet material. As the sheet material and molds are advanced in steps through the apparatus, presses clamp the molds and belt against opposite surfaces of the sheet material and raise the temperature of the assembly to embossing temperature for the resin to cause the resin to flow into the mold cavities, and volatiles at the interface are dissolved in the resin. After the embossing step, the clamping pressure is released and this permits limited shrinkage of the mold and sheet material.

Abstract: A method and apparatus for substantially instantaneous liquid molding of an article utilizing a radiation curable liquid composition and a forming mold transparent to the through passage of radiation so that radiation curing of the liquid composition is effected during the molding thereof.

Abstract: A method of producing a uniform synthetic coating on a working cast for dental applications which comprises:(A) applying to or introducing in said working cast a first catalyst component which, when initiated by a second catalyst component, effects polymerization of a polymerizable composition;(B) thereafter applying to said working cast said second catalyst component and a polymerizable composition which, when polymerized, forms a resin; and(C) thereafter effecting polymerization of said polymerizable composition to form a film.

Abstract: Dental prosthetic devices, such as artificial teeth, crowns, bridges and replacements for parts of teeth are provided comprising hardened resin dental materials containing at least one polymer and a finely divided inorganic filler, said filler being present in an amount of about 10 to 90% based on the weight of the material and having a particle size within the range of 10 to 400 millimicrons, said materials having an extremely high compressive strength, clear opalescence and a very smooth homogeneous surface.

Abstract: Method and apparatus for manufacturing laminant veneers for application to the teeth of a dental patient. The method involves heat and fluid pressure induced forming of a dental laminant veneer to cause the veneer to assume the configuration of a standard mold or a model mold of a dental patient's teeth. The apparatus includes a heat chamber and means to move the dental veneers and mold and the heat chamber into interrelation to cause heat softening of the veneers. A flexible membrane is pressure induced by vacuum or positive pressure and causes the softened veneers to assume the configuration of the mold.

Abstract: Disclosed is a dental arrangement and method for restoring broken teeth which require a crown and a retention post for securing the crown in a post hole formed in the tooth. The post hole is dimensioned to receive a first sleeve, which in turn is dimensioned to receive the retention post. By using the sleeve for confirming a desirable post hole size, and for centering the retention post during the making of the impression, a sufficient margin of error is built into the space between the post hole and the retention post to allow the placement of cement. A wax sealed second sleeve, with a short post therein, is used in making a die of the tooth.

Abstract: A novel method for embedding a button into a dental cast by forming a cavity and pouring a cold setting material such as a plastic into which a screw is inserted while the poured button is in the fluid form before final setting. The screw has a notch in at least one thread so that the molding material forms an interlock or detent in the notch, which is sheared upon removal of the screw.

Abstract: A method for producing in a single casting operation a dental model including a unitary tooth die which incorporates an integral mounting pin. The pin and die form a part of, and are removable from the dental model. Prior to casting the die, a bayonet shaped mounting pin is held in position by a permanent divider which, in turn, is supported in a negative impression of a denture. The die and base are then cast simultaneously, eliminating the need for the more commonly used double casting procedure.

Abstract: Method for making a tooth positioning and retaining appliance with air holes. The apparatus includes a mold with a cavity having models of the upper and lower teeth arranged so that when an appliance is molded thereby the appliance will have upper and lower archways for receiving upper and lower arches of a person, tooth sockets in the archways arranged in ideal relationship and preselected positions to urge the teeth received thereby into the preselected positions of the sockets. The mold additionally includes air hole or airway forming means extending across the models of the teeth in the mold and being insertable into the mold prior to the molding operation and thereafter removable from the mold with the molded appliance. The air hole forming means is easily separable from the appliance to ultimately define the air holes between the archways and between the labial and lingual sides of the appliance. The method of making the air holes concerns the handling of the mold and the air hole forming means.

Abstract: A dental probe having a stylus which is connected through a rod to a three position transducer which produces three signals indicating the position of the probe at any point to which the probe is applied. The transducers are mounted on an index tray which is adapted to be fastened to the jaw of the patient. Thus the patient's jaw becomes the origin against which all measurements are made. A handle is connected to the probe in such a fashion that the dentist has three rotational degrees of freedom of movement without affecting the position of the end of the stylus. Contact between the tip of the stylus and the patient's tissue completes a circuit to turn on the recording mechanism which receives the transducers' outputs.

Abstract: A process for forming a removable dental cast embedded with a plastic, threaded, cast ejector button, and apparatus for fabricating a plurality of cast ejector buttons comprised of a mold device including an upper plate containing a plurality of mold cavities, and a base plate incorporating coil spring means for resiliently maintaining the upper plate in a predetermined spaced-apart and open relation thereto and a plurality of rigid support elements attached, at their bottom ends, in vertically-upright relation on the base plate and slidably engaged, at their upper ends, in a bottom opening in each upper plate-mold cavity and extending in overlapping relation into the respective cavity. The upper ends of each rigid support element are threaded so that, when the mold cavities are poured with and filled by a suitable material, in the plastic flow form that is allowed to set for a specified period, a separate and internally threaded plastic cast ejector button is formed in each cavity.