In this study, standard and prototype reinforced e-PIFE membranes were used to evaluate the pattern of bone regeneration in membrane protected defects in the mandibles of four dogs. Following a healing period of 2 and 4 months, control sites without membranes exhibited incomplete osseous healing with a persisting defect. Test sites with membranes demonstrated significantly better bone healing, although bone regeneration was not yet completed at 4 months. The histologic evaluation showed that bone regeneration, once activated, progresses in a programmed sequence through a series of maturation steps, which closely resemble the pattern of bone development and growth. Schlagwörter: bone defects, bone healing, guided bone regeneration, membranes