Purpose: To evaluate the influence of mandibular dentition on the performance of maxillary implants prior to definitive prosthesis attachment in maxillae that have been reconstructed with autogenous bone grafts. Materials and Methods: A retrospective review of 90 consecutive patients, 31 men and 59 women, with a mean age of 57.4 years, was conducted. All patients underwent treatment planning to receive endosseous implants in the edentulous maxilla in conjunction with autogenous bone grafting. During the time from implant and/or bone graft placement until placement of the definitive restorations in the maxillae, the mandibular dentitions were recorded and categorized into 6 groups based upon the presence and distribution of teeth. Results: Of 643 implants placed, 118 (18.4%) were lost between implant placement and definitive prosthesis placement. The type of mandibular dentition was significantly associated with implant failure during this time interval (P .001). In particular, the patients with implants opposing unilateral occlusal support showed the highest rate of implant failure (43.8%, or 28 of 64 implants). Implants that opposed a mandibular implant-supported fixed prosthesis demonstrated an implant failure rate of 14.3% (10 of 70), and in patients with a removable mandibular denture, the implant failure rate was 6.2% (4 of 65 implants failed). The overall mean patient follow-up was 64.2 months. At 60 months, the cumulative implant failure rate based on the Kaplan-Meier method was 20.2%. Discussion: Unfavorable concentration of forces on the maxilla may contribute to increased risk of implant failure. Conclusion: Effort should be made to create a favorable occlusion in the mandible, with attention being paid to broad distribution of occlusal contacts. Keywords: atrophy, autogenous bone graft, dental occlusion, dentition, endosseous dental implantation, mandible, maxilla