A break-resistant composite comprising a plurality of fibers at least partially embedded in a polymer matrix forms a composite for making at least a portion of an endodonic instrument. At least a portion of the fibers are selected from a group consisting of partially twisted fibers and off-axis oriented fibers. The composite instrument can contain abrasive particulates to improve cutting and wear resistance for use in root canal procedures. The twisted fiber composite material allows for applied torque load response, improved flexibility within the root canal, and reduces or eliminates gross breakage of the instrument during use. The inventive composite can be molded or machined to make an endodnic instrument having certain desired diameters, tapers, helical recesses, and other design features.

A method of manufacturing a polishing substrate is disclosed. The method includes disposing into a mold a reaction mixture of dibasic acid and a hydroxylated polymer, and applying a pressure and a temperature to the reaction mixture that are sufficient to cause polymerization and substrate formation in the mold. The dibasic acid is preferably adipic acid. Before pressure and temperature are applied to the reaction mixture, the reaction mixture is capable of being fortified with a polishing agent and/or a filler for controlling modulus and/or the coefficient of expansion.

A clogging phenomenon in the surface layer of the contact face of a soft plastic-and-abrasive composite for polishing painted surfaces, which reduces the efficiency of the polishing work, is alleviated by mixing into the soft plastic backing material of the composite containing abrasive fine particles, non-abrasive globular particles preferably formed out of bubble material. The globular particles are rotatable in the surface layer of the contact face of the soft backing when the composite is in rubbing contact with the surface to be polished. Water or a surfactant may be interposed between the surface to be polished and the composite. The surface to be polished is rubbed with the composite to remove contaminating substances adhering to the surface to be polished.

An abrasive composite, a method for making the abrasive composite, and a polishing apparatus using the abrasive composite are disclosed. The abrasive composite includes a matrix and a plurality of nano-particles distributed therein. The nano-particles are made of at least nano carbon sphere particles and fullerene particles. A ratio by weight of the nano carbon sphere particles to the fullerene particles is advantageously in the range from about 1:2 to about 1:1. The fullerenes are preferably C.sub.60 fullerenes. The abrasive composite further includes an amount of diamond particles admixed in the matrix, for improving hardness of the abrasive composite so as to accelerate polishing rate. The abrasive composite is preferably in a form of pellets. The pellets have an average grain size in the range from about 10 nanometers to about 200 nanometers.

A dental tool that has a thin disc covered with an abrasive material. The disc has a flange portion and coupling device is formed adjacent to the flange portion for attaching the disc to a drive device. The drive device spins the disc to treat a dental surface. The thickness of the disc may decrease from a central portion of the disc toward a peripheral edge of the disc. The disc may be interspersed with an abrasive material integrated into the disc by an elastic bond.