Abstract: A setting device uses a driving piston for propelling fastening members into a receiving material. High pressure gases within an expansion chamber propel the driving piston through a working cylinder against a fastening element. A vent valve connects the expansion chamber with the atmosphere exterior of the setting device and, normally, the valve is maintained in the open position. A control member, located in part on the outside of the setting device, moves the vent valve into the closed position when a fastening member is to be driven.

Abstract: A setting device includes a driving piston propelled by high pressure gases through a casing for driving fastening elements into a receiving material. A stop device located within the casing secures a stop element in a recess in the driving piston for holding the piston in the firing position. The stop device includes a first spring and a second spring each biasing the stop element into the recess. The first spring has a greater biasing force than the second spring. To release the driving piston from the firing position so that it can drive a fastening element into a receiving material, the propelling forces acting on the piston displace the stop element against the force of the springs and then the first spring biases the stop element against the second spring. After the stop element is displaced out of the recess only the second spring acts on the stop element so that movement of the driving piston relative to the stop element is effective without any appreciable holding action limiting such movement.

Abstract: Imidazoles in dissolved form act as an agent for retarding the gelation of the polymerization of aziridine compounds initiated with sulfonium salts. The composition is particularly useful in dentistry applications, such as in the preparation of impressions and provisional denture parts.

Abstract: Impression materials based on cross-linked aziridino-polyester compounds which tend to adhere to the surface to be reproduced, are made nonadhesive by the addition of 1-15% by weight of oleic acid ethanolamide with respect to the aziridino-polyether component, and may thereafter be more easily and smoothly released from the object to be reproduced.

Abstract: 1,2,6-Thiadiazine-3,5-dione-1,1-dioxides of the general formula ##STR1## wherein each R and R.sub.3 independently may be substituted or unsubstituted alkyl, alkenyl or substituted cycloalkyl are described. These compounds, as well as those wherein the R substituents additionally may be cycloalkyl or substituted or unsubstituted aryl, are useful as accelerators for the peroxidic polymerization of ethylenically unsaturated compounds, such as methacrylic acid compounds, and have particular utility in dental compositions.

Abstract: A fastening element setting device powered by an explosive gas mixture includes a housing forming a guide cylinder for a propulsion piston which drives the fastening element into a receiving material. The components of the gas mixture, one at a higher pressure than the other, are delivered through separate supply lines into an inlet duct and then to a combustion chamber. A control slide valve is located between the supply lines and the inlet duct and regulates flow, with the higher pressure component following the lower pressure component into the inlet duct and combustion chamber. A closure valve in the supply line of the lower pressure component blocks any inflow when the higher pressure component flows into the inlet duct.

Abstract: The invention relates to the use of agglomerates of silicic acid having an average agglomerate size of 0.5 to 50 .mu.m, containing primary particles of silicic acid having an average particle size of 1 to 100 nm and serving as filler in dental materials on the basis of ethylenically unsaturated polymerizable monomers. This reinforcing filler is practically colorless and can be blended in considerable quantity into the polymerizable monomer material especially mono-functional and di-functional as well as polyfunctional esters of the acrylic acid and the methacrylic acid and yields a satisfactorily processable plastically deformable paste. If necessary, the agglomerated silicic acid is used together with non-agglomerated micro-fine silicic acid of an average particle size of 1 to 100 nm.

Abstract: An explosive powder operated setting device uses the propellant gases from an ignited explosive powder charge for driving a piston which, in turn, propels a fastening element from the device into a receiving material. The device includes a housing, a barrel mounted in the housing with the piston displaceably mounted in the barrel. A tubular-shaped slide valve is rotatably mounted in the rear portion of the barrel behind the piston. The front end of the slide valve combines with the barrel in forming a space in which the propellant gases contact the piston and drive it through the barrel. The rear end of the slide valve forms a part of the combustion chamber within the device. At its front end, the slide valve is frusto-conically shaped and forms a seal with a correspondingly shaped surface in the barrel. An exhaust duct section extends through the barrel and is in communication with another exhaust duct section in the housing.

Abstract: A calcium aluminum fluorosilicate glass powder is disclosed which has average particle size of at least 0.5 microns, and is characterized in that the calcium in the surface of the powder's particles is depleted so that the quotient of the atomic ratio Si/Ca at the surface of the particles and the atomic ratio Si/Ca in the core region of the particles is at least 2.0, more preferably at least 3.0 and most preferably at least 4.0. The glass powder may be prepared by surface treating calcium aluminum fluorosilicate glass powder particles with an acid which forms calcium salts, washing the calcium salts off the treated particles and drying the washed particles.The glass powder has utility in self-hardening glass ionomer cements, such as dental or bone cements. Cements formed from the glass powder exhibit reduced periods of water sensitivity, while permitting sufficient time for processing.

Abstract: An improved opaque, photopolymerizable dental filling material is provided comprised of acrylic acid ester compounds containing mono and/or polyfunctional acrylic or methacrylic ester compounds, photoinitiators, pigments and possibly activators and silicon dioxide or silicate fillers, the improvement comprising the presence of finely divided calcium fluoride as a white pigment in a quantity of from 1-20 percent by weight. The presence of the calcium fluoride enables an opaque effect to be achieved without reducing the permeability of the filling material to polymerization radiation.

Abstract: A setting device arranged to use caseless propellent charges for driving fastening elements, such as bolts, nails and the like, into a hard receiving material includes a casing containing an axially slidable barrel forming a feed element at its rearward end. A counterpressure member is slidably movably supported within the casing and in combination with the end face of the feed element forms a combustion chamber for the caseless propellent charges. When the feed element is displaced rearwardly and forms a part of the combustion chamber, a ring located within the housing encircles its outside surface. The ring has a radially outer frusto-conical surface in contact with a complementary frusto-conical surface on the housing. When a caseless propellent charge is fired, propellent gases contact the ring and displace it along the frusto-conical surface on the casing causing it to be forced into sealing contact with the outside surface of the feed element.

Abstract: Dental glass ionomer cements are obtained by using as a mixing component for preparing the final cement mixture either a liquid mixing component comprising an aqueous solution of a certain maleic acid-acrylic acid-copolymer and optionally usual additives or a solid, powdery mixing component comprising a powder mixture of a glass ionomer cement powder and the maleic acid-acrylic acid-copolymer in solid form and optionally usual additives.

Abstract: Prosthetic dental appliances of stable color and good mechanical properties can be produced by photopolymerization of one-component preparations which are stable during the storage, on the basis of ethylenically unsaturated monomers as well as fillers and dyes when using bicyclo-[2.2.1]-heptane-dione-2,3 compounds, if necessary together with amines, as photoinitiators for achieving sufficient penetration of the polymerization and whose inherent yellow color after short primary irradiation with visible light is bleached out for fixation permanently by intensive postirradiation with visible light.

Abstract: A rack-rail assembly for a mining machine has a pair of relatively long rail sections longitudinally generally aligned with each other and having respective forked ends juxtaposed at a joint location. A relatively short link at this joint location has at each of the forked ends an outwardly projecting pin that engages in elongated holes of the forked ends so that limited relative longitudinal displacement between the rail sections and the link is possible. This link has at least two teeth and each of the rail sections has a plurality of teeth, so that when a mining machine travels along the rail assembly thus formed variations in tooth spacing at the joint location can be compensated for. A damping or spring member is provided between each of the rail sections and the link, normally urging them apart.

Abstract: A sleeve-like holding member is positioned within the housing of an explosive powder operated gun-like setting device for gripping the fastening element before it is propelled from the housing. The holding member has at least one axially extending slot so that it is radially expandable against its own inherent tension. When a plurality of slots are provided, they are spaced angularly apart and extend from one end toward but short of the other end of the holding member. Adjacent slots extend from different ends of the holding member.

Abstract: An improved photopolymerizable composition based on acrylic or methacrylic acid esters is disclosed. In addition to the mono- or polyfunctional acrylic or methacrylic acid ester compounds, an aliphatic, aromatic or mixed aliphatic-aromatic organic phosphite compound (in an amount of from about 0.1 to 20 percent by weight of the photopolymerizable ester compounds) and a monoketal of an aromatic 1,2-diketone compound (e.g., benzildimethylketal) are included as ultraviolet initiators to dramatically reduce the polymerization time of the composition without adversely affecting its stability.

Abstract: A novel process for the polymerization of aziridine compounds is disclosed. The polymerization process includes mixing an aziridine compound with a polymerization initiator having the formula: ##STR1## where R.sup.1 is an alkyl radical of 1 to 18 C atoms,R.sup.2 is an alkyl radical of 1 to 18 C atoms or a phenyl alkyl radical of 7 to 18 C atoms, wherein said alkyl radicals may contain an ester group and/or ether group, R.sup.3 and R.sup.4 are hydrogen, an alkyl radical of 1 to 18 C atoms, and/or an aryl radical which can be substituted with a chloro, nitro or alkoxy group, whereby the alkyl radicals of R.sup.3 and R.sup.4 together or in combination with B can form a cycloaliphatic or heterocyclic ring, B is an electron attracting radical, and A.sup..crclbar. is a non-nucleophilic anion.Polyimines are quickly formed at ambient temperature.

Abstract: In an explosive powder operated setting device or gun for driving fastening elements, such as bolts, studs and the like, into a hard receiving material, the amount of explosive gases used in the driving operation is regulated by a control member located in the setting gun. The control member is conically shaped and fits into a conically shaped surface in the bore in the gun. The conical member is rotatably mounted in the bore between the firing chamber and an exhaust duct for regulating the amount of explosive gases diverted to the duct instead of being used in the fastening element driving operation.

Abstract: In an explosive powder operated device using caseless powder charges for firing fastening elements into a hard receiving material, the firing chamber in the barrel of the device is defined in part by one end of a counterhammer. The one end includes a sealing ring having a frusto-conical sealing surface supported on a correspondingly shaped surface on an axially extending body part of the counterhammer. When a caseless charge is ignited in the firing chamber, the explosive gases generated act in direct surface contact on at least a portion of the sealing ring which faces into the firing channel.

Abstract: An improved dental composition having shortened hardening time and after hardening increased compressive strength and abrasion resistance, including a radical-inducing compound and a polymerizable acrylic or methacrylic acid ester or diester compound with at least 20 percent by weight of the polymerizable compound being the diacrylic or dimethacrylic acid ester of bishydroxymethyltricyclo [5.2.1.0.sup.2,6 ]-decane. Other monofunctional or difunctional acrylic or methacrylic acid esters as well as fillers, pigments and stabilizers can be included.