The present invention is directed to a dental instrument, and specifically toanimproved composition for endodontic instruments useful for filling rootcanals. In anembodiment, the invention provides use of a carrier composition for filling atooth rootcanal for molding a chemically cross-linked carrier body of an endodonticobturator,wherein the carrier composition comprises cis 1-4, polyisoprene. In anotherembodiment, the invention provides a carrier composition for filling a toothroot canal,comprising a thermoset material, the thermoset material being cis 1-4,polyisoprene；a radiopacifier； a curing agent； and a filler.
