Abstract: In a setting gun using explosive force for driving fastening elements into a receiving material, an elastic damping device is provided to absorb the residual kinetic energy of a driving piston. The damping device consists of a plurality of serially arranged pairs of rings extending between a muzzle tube and a stop ring mounted in the forward end of a barrel. Each pair of rings consists of a radially inner ring and a radially outer ring each having a frusto-conical surface in contact with the other. The frusto-conical surfaces converge in the firing direction of the setting gun. In one embodiment, each pair of rings has the same axial length, however, in another embodiment the axial length of the rings increases in the firing direction of the setting gun so that the mass of the pairs of rings increases in the firing direction.

Abstract: An improved process for the photopolymerization of compositions including photopolymerizable acrylic or methacrylic acid esters and an initiator (e.g., a benzoin compound) is disclosed. The addition of 0.1 to 20 weight percent (based on the amount of polymerizable material) of an organic phosphite substantially reduces the polymerization time of the resulting composition.

Abstract: An improvement in the redox polymerization of unsaturated compounds, e.g., acrylic or methacrylic acids or their ester derivatives, using novel accelerators is disclosed. The polymerization is performed utilizing as the accelerator N,N-bis-hydroxyalkyl-3,5-di-t-butyl anilines having the structural formula ##STR1## wherein R.sub.1 and R.sub.2 are the same or different and are H or a lower alkyl group having 1 to 4 carbon atoms. The resulting polymers are highly resistant to discoloration.

Abstract: Novel bromine-containing compounds of the formula ##STR1## in which R is an alkylidene radical having 1 to 6 carbon atoms, a cycloalkylidene radical or a SO.sub.2 radical, R' is an alkylene radical having 2 to 6 carbon atoms or a cycloalkylene radical and Y is an acyl radical of a carboxylic acid having 2 to 6 carbon atoms and optionally bearing an aromatic substituent, and x is 1 or 2 and y is 0, 1 or 2, which are particularly useful for the preparation of dental replacement parts and dental models when mixed with a substance that catalyzes the polymerization of the compounds.

Abstract: Compositions, which may be mixed with water to prepare a dental silicate cement, consist essentially of a silicate glass powder and a solid polymeric material selected of polymers of unsaturated .alpha.,.beta.-dicarboxylic acids.

Abstract: Superior artificial teeth, dentures, other dental replacement parts and dental prosthetic articles and devices, which exhibit high abrasion resistance, stability to moisture and which do not undergo volume changes, are obtained by polymerization of a compound of the formula ##STR1## in which R is H or -CH.sub.3, X is an alkylidene or the -SO.sub.2 -group, Y is an oxyalkylene group having between 2 and 5 carbon atoms, or an alkylidene group having between 1 and 5 carbon atoms. In some instances, the polymerization is carried out in the presence of a filler.

Abstract: In an explosive charge setting gun used for driving fastening elements into a hard target material, caseless charges are positioned in a magazine duct and are separated by spacers. A movable element in the gun picks up a caseless charge from the magazine and moves it into position to be fired. The movable member includes an ejector which displaces the spacer following the charge, from the magazine. The movable element can be a slidable barrel or a separate slide member. The ejector can be formed as recesses or cams on the movable element. The spacers are shaped so that they are not picked up by the movable element when a charge is moved into the firing position.

Abstract: In an explosive charge driven setting gun having an axially displaceable barrel and using caseless propellant charges for driving fastening elements into a hard receiving material, the firing chamber in the gun is movable between a charge loading position, a firing position and an ejecting position. The firing chamber can be formed in the barrel so that it is movable with the barrel, or it can be positioned in a separate member rotatable about an axis parallel to the axis of the barrel. An ejecting member is associated with the barrel and is displaceable through the firing chamber when it is in the ejecting position for clearing the chamber of any unfired charges or of the residue of fired charges.

Abstract: In an explosive charge driven setting gun for inserting fastening elements into a hard receiving material, caseless charges are positioned in an opening in a holding member prior to being inserted into the firing chamber. A feed member in the gun displaces the charges from the holding member opening into the firing chamber and a plunger located on the opposite side of the firing chamber from the feed member is movable through the chamber for clearing an unfired charge or any residue of a fired charge. The holding member can be a magazine or a separate slide movably mounted in the gun housing. Preferably, the opening in the holding member, the feed member, the plunger and the firing chamber all have the same cross sectional shape viewed transversely of the firing direction of the gun.

Abstract: Dental cements are prepared by mixing a silicate powder with an aqueous solution of polymers of unsaturated alpha, beta-dicarboxylic acids.