Five-Year Results of a Randomized Controlled Trial Comparing Patients Rehabilitated with Immediately Loaded Maxillary Cross-Arch Fixed Dental Prosthesis Supported by Four or Six Implants Placed Using Guided Surgery

Purpose: To compare the 5-year clinical and radiological outcomes of patients rehabilitated with four or six implants placed using guided surgery and immediate function concept. Materials and Methods: Forty patients randomly received four (All-on-4) or six (All-on-6) immediately loaded implants, placed using guided surgery, to support a cross-arch fixed dental prosthesis. Outcome measures were survival rates of implants and prostheses, complications, peri-implant marginal bone loss, and periodontal parameters. Results: No drop-out occurred. Seven implants failed at the 5-year follow-up examination: six in the All-on-6 group (5%) and one in the All-on-4 group (1.25%), with no statistically significant differences (p =.246). No prosthetic failure occurred. Both group experienced some technical and biologic complications with no statistically significant differences between groups (p =.501). All-on-4 treatment concept demonstrated a trend of more complications during the entire follow-up period. A trend of more implant failure was experienced for the All-on-6 treatment concept. Marginal bone loss (MBL) from baseline to the 5-year follow-up was not statistically different between All-on-4 (1.71 ± 0.42 mm) and All-on-6 (1.51 ± 0.36 mm) groups (p =.12). For periodontal parameters, there were no differences between groups (p >.05). Conclusion: Both approaches may represent a predictable treatment option for the rehabilitation of complete edentulous patients in the medium term. Longer randomized controlled studies are needed to confirm these results.