To gain more insight into the treatment strategies for edentulous patients with atrophic ridges, three groups of patients were evaluated: group 1, patients with atrophy of the mandible who needed preprosthetic surgery but who only received new dentures because surgery was contraindicated; group 2, patients in the same oral condition as those in group 1 who were treated with vestibuloplasty and lowering of the floor of the mouth before fabrication of new dentures; group 3, the control group of patients without residual ridge-related problems who were treated with new complete dentures. The differences between the three groups were evaluated 6.5 years after treatment. The results showed that the surface areas of the patients in group 2 were approximately 180% greater in the vestibular region and were 126% greater in the sublingual region, compared with the other groups. The stability of the mandibular dentures as well as the retention were better in group 2 than were those in group 1. Group 2 patients scored comparably or higher than the normal ridge group (group 3). The resistance against dislodgment of the denture was low in all three groups.