Basic cell and tissue reactions in distraction osteogenesis of the rabbit mandible

The objective of our study was to test whether the magnitude and/or the frequency of discontinuous mechanical traction regulates the tissue response in distraction osteogenesis Rabbits mandibles (n=48) were osteotomized and distracted by applying various distraction rates. The newly formed tissue was examined histomorphometrically, ultrastructurally, microanalytically, and biochemically Mature bone formation was detected in samples exposed to physiological strain magnitude (0 - 2000 mu strains), whereas application of hyperphysiological strains (200,000 - 300,000 mu strains) resulted in the formation of fibrous tissue. Multiple strain applications (10 cycles/day versus 1 cycle/day) did not significantly alter the histomorphometrical indices or ultrastructural morphology, but increased the amount of newly formed tissue. TGF-beta serum levels changed during the regeneration process, indicating an important role of this protein in bone formation, while IGF-I concentrations remained relatively unaltered.