Bone plate and bone plate assemblies including polyaxial fasteners

A system for fixation of bone, including a bone plate with an opening comprising threads made of a first material and a fastener with a head at least partially comprising a polymeric material that is softer than the first material. In some embodiments, when the fastener is inserted into the first opening, the threads of the first opening form threads in the polymeric material on the head of the fastener and secure the fastener in place at one of a plurality of possible angles within the first opening. The first opening additionally accepts a fastener with a substantially spherical head for compression of a fracture, or a fastener with a threaded head that engages with the threads of the threaded opening. In some embodiments the first opening includes a substantially frustoconical-shaped top portion. In other embodiments there may be a second opening that is either non-threaded or comprises a plurality of protruding fins.