Abstract: A method contemplated by the present invention for producing semi-finished prosthetic dental preforms essentially comprises the steps of repulverizing a dental porcelain mixture including a suitable binder by spray drying such dental porcelain molding the repulverized dental porcelain mixture in a die member having a cavity with a form generally complementary to that desired for the molded product, removing the molded product from the mold; and applying an outer coating of a suitable second dental porcelain to selected exterior surfaces of the molded product. The binder for the ceramic material comprises 10.5% to 8.5% ethylene vinyl acetate resin, 5.3% to 3.9% mineral seal oil and about 2.2% to 1.6% stearic acid.

Abstract: A tristimulus colorimeter employs a multiplexed dual slope integrator digital voltmeter wherein unknown and reference light beams are compared by sequentially applying unknown and reference electrical signals representative of the two respective light beams to the non-inverting and inverting inputs, respectively, of the integrator amplifier. Moreover, a compensating circuit provides for compensation of the colorimeter output signals with respect to reflectance error encountered in the optics portion of the colorimeter with such compensation being provided as a function of the light intensity from the colorimeter light source.

Abstract: A process is disclosed for producing chrome alloys in a form suitable for casting dental appliances. A chrome dental alloy which is inherently capable of being processed, prior to casting the appliance, to wrought form by hot working is first fused to form a melt in a heating means (e.g., an electron beam hearth) which substantially excludes the presence of or substantially removes tramp elements (e.g., carbon, oxygen and nitrogen). The melt is then cast into an ingot which is subsequently hot-worked to form a shaped piece (e.g. bar, strip, rod or wire). The shaped piece is next cut into small weight pieces of predetermined size convenient for handling by dental laboratories and the pieces are coated with water glass (e.g., sodium silicate) so as to protect the pieces from contamination with tramp elements during the heating period preparatory to melting and casting into dental appliances.

Abstract: A tristimulus colorimeter employs a multiplexed dual slope integrator digital voltmeter wherein unknown and reference light beams are compared by sequentially applying unknown and reference electrical signals representative of the two respective light beams to the non-inverting and inverting inputs, respectively, of the integrator amplifier. Moreover, a compensating circuit provides for compensation of the colorimeter output signals with respect to reflectance error encountered in the optics portion of the colorimeter.

Abstract: A comparison type colorimeter concentrates unknown and reference light beams onto the same surface area portion of a single photosensor and additionally filters the unknown and reference light beams by the same color filters and, preferably, portions thereof. Moreover, an enclosed light source produces light for the colorimeter to eliminate shift in illumination due to dust accumulation on the lamp and/or reflector of the light source.

Abstract: Method of using a tristimulus colorimeter including a modified dual slope integrator digital voltmeter which measures the red, blue and green light reflected from a sample and displays the same in digital form as optical density units. The colorimeter includes a light conducting probe with a diffusing member and a movable collar for blocking ambient light, and a rotating color filter wheel is synchronized with the voltmeter for effecting a continuous update of the data displayed thereby. Moreover, a color averaging method provides for prediction of the ultimate color of a mixture of two differently colored porcelains or the like especially used in the construction of artificial teeth or the like.

Abstract: An automatic zeroing circuit normalizes a detector-measuring apparatus to eliminate relatively steady-state DC errors that may develop in response to the temperature or other variable parameter dependency of leakage currents in a transducer, such as dark currents in a photosensitive transistor. Therefore, the outputs from such apparatus are generally insensitive to such variables and errors.

Abstract: A single adjustable control is commonly connected with each of a plurality of feedback channels, which are selectively coupled in an amplifier circuit to provide the latter with different basic gains, to adjust the respective basic gains of the amplifier circuit by corresponding fractional or proportional amounts of respective ranges of permissible gain chain for each channel, thereby simultaneously to correct or to calibrate each channel for different amounts of drift of the like.

Abstract: A relatively viscous light transmissive liquid material, such as glycerine or the like, applied to the solid end portion of a light conducting member enhances the optical coupling with a sample or object having an irregular and/or glossy surface to be optically examined. Moreover, the light probe system has a test end with a tip for substantial abutment with a test area or test point of a sample. The tip provides point or primary illumination of the test point and a further source of general or secondary illumination is provided the sample annularly about the probe tip and test point so that upon illumination of the sample ambient lighting effects are simulated.

Abstract: A tristimulus colorimeter including a modified dual slope integrator digital voltmeter measures the red, blue and green light reflected from a sample and displays the same in digital form as optical density units. The colorimeter includes a light conducting probe with a diffusing member and a movable collar for blocking ambient light, and a rotating color filter wheel is synchronized with the voltmeter for effecting a continuous update of the data displayed thereby. Moreover, a color averaging method provides for prediction of the ultimate color of a mixture of two differently colored porcelains or the like especially used in the construction of artificial teeth or the like.