Seven-Year Follow-up of Full-Arch Prostheses Supported by Four Implants: A Prospective Study

Purpose: To evaluate biologic and prosthetic outcomes of implant-supported mandibular full-arch fixed prostheses treated with the All-on-4 treatment concept after 7 years. Materials and Methods: Patients were selected to receive full-arch fixed immediate prostheses supported by four implants up to 72 hours after surgery. The following biologic aspects were evaluated: Plaque Index (PI) and Bleeding Index (BI), implant stability by resonance frequency, and marginal bone loss (MBL) measured with the aid of periapical radiographs. The prosthetic complications evaluated were related to screw loosening, framework or acrylic teeth fractures, or fractures of implants. The means of implant stability and MBL were subjected to analysis of variance and the Tukey test (P .05). For PI and BI, the Friedmann test was used (P .05). Results: Sixteen patients (12 women and 4 men; mean age: 59.1 years) received 64 implants, and in all patients, two implants were positioned axially at the incisor region and two distally tilted implants at the region of the second premolars or molars. Patients were evaluated immediately after surgery and at 1, 2, and 7 years. Fifteen patients attended the recall after 2 years; one patient could not attend the scheduled follow-up visit and was excluded from the sample. In the 7-year evaluation, the sample size decreased to 12 patients; one could not attend because of a severe disease, and two were deceased. The cumulative implant survival rate was 100%. There was a significant (P .0162) decrease in PI at the 1- and 7-year evaluations (71.87% and 47.92%, respectively), while the BI was the same at 1 and 7 years (43.75%). There was no statistical difference in MBL (P = .12) and implant stability (P = .48) between axial and tilted implants (P = .48). The survival rate of prostheses was 100%. The following technical complications were observed: tooth fracture occurred in one patient (6.25%); loosening of prosthetic screws and abutments were observed in three patients (18.75%); after 5 years, three patients (18.75%) had changed the denture acrylic teeth because of the replacement of the removable total maxillary prostheses with fixed implant prostheses. Conclusion: For the 12 patients who attended the recall after 7 years, implant loss was not found, the implant stability was high, MBL was low, and prosthetic complications were easily solved. Thus, it can be concluded that rehabilitation with implant-supported mandibular full-arch fixed prostheses with four implants has proved to be a treatment with a high survival rate. Keywords: bone loss, dental implant, immediate loading, mandible, tilted implant