[Implanting the edentulous jaws with "All-on-4" immediate reconstruction: a preliminary clinical observation].

Objective: To evaluate the treatment outcome of the "All-on-4" immediate loading protocol via survival rate of the implants,survival rate of the prosthesis,marginal bone, postoperative complications and patient satisfaction.

Methods: In our study, 40 patients with 49 edentulous jaws (31 mandibles and 18 maxillae) were enrolled. Each jaw was restored by the shortened dental arch prosthesis supported by only 4 implants according to the All-on-4 protocol (All-on-4, Nobel Biocare AB, Goteborg, Sweden). For all the patients enrolled in the study, the loading was applied within 12 hours of surgery. The provisional prosthesis could be replaced by the final restorations within 6 to 12 months. In the present study, the survival rate of the both implants and restorations were calculated and analyzed. The radiographic evaluation of marginal bone level changes was measured. The values of the marginal bone level changes of the angled and axial implants were analyzed by the statistic software.

Results: In the present study, totally 196 implants were inserted, of which 13 implants failed during the whole following up periods, with 11 implants of the maxillae and 2 of the mandibles. The survival rate of the prosthesis was 95.9% (47/49). The implant survival rate of the maxillae was 85.5% (65/76)while that for the mandibles was 98.3%(118/120). The implant survival rate of the angled implants was 91.8% (90/98), while that for the straight implants was 95.0% (93/98). No significant difference in marginal bone loss was found between angled and axial implants in the 12-month evaluation according to the Wilcoxon rank sum test (P>0.05). During the follow-up period,mechanical complications as fracture of the provisional prostheses, loose of the retain screw, or crack of the artificial teeth were found in 20 prostheses.

Conclusion: The present preliminary data of the short term observation suggest that the "All-on-4" immediate loading protocol is a viable treatment modality for the edentulous jaws. However, long term clinical random controlled trials with large samples are still needed to confirm the validity of the technique.