The dynamics of morphological changes and morphometric characteristics of mandibular defects and the surrounding bone and soft tissues in the course of regeneration were investigated in 52 rats after the infliction of a perforated defect in the mandible and its repair by the implantation of polyurethane and titanium plates and screws. It was shown that a connective tissue capsule formed around the implants within 7-14 days after their introduction; it thereafter matured and persisted as long as 90 days. The fibrous capsule surrounding polyurethane screws, unlike that around titanium screws, contained foci of nonspecific granulematous inflammation induced by the foreign bodies (polyurethane particles). However, the inflammation had only insignificant influence on the maturation of the capsule and the formation of bone regenerates around the defect. The mean area of the newly-formed bone tissue adjacent to the polyurethane plates was greater than that around titanium plates. The mean area of bone regenerates around polyurethane screws in the early and intermediate time intervals after their implantation was similar to or larger than that around titanium screws.