This investigation was concerned with the resorption of the posterior mandibular residual ridge in patients wearing mandibular overdentures supported by either parallel-sided bars (rigid joint) or oval straight bars (resilient joint) on two activated implants. Rotational tomographs were taken shortly after implant placement and up to 8 years later. Using proportional measurement, the area of residual ridge was measured in bilateral posterior areas. Patients rehabilitated with implant-stabilized mandibular overdentures demonstrated posterior mandibular residual ridge resorption at low rates, which were not significantly influenced by the design of the prefabricated bar. Keywords: bone resorption, dental implants, mandible, overdentures, residual ridge