All on 4 Versus All on 6 implant concepts for rehabilitation of edentulous maxilla. Short term randomized clinical and radiographic study

Purpose: The aim of the present study was to evaluate clinical and radiological outcomes of “All on 4” Versus “All on 6” implant concepts for rehabilitation of edentulous maxilla.
Materials and methods: 10 patients with complete maxillary edentulism and distal extension mandibular ridges who had resorption in the posterior aspects of the maxillary ridge were randomly assigned into 2 groups: Group 1 included 5 patients who received All on four maxillary prosthesis, and group 2 included 5 patients who received All on six maxillary prosthesis. Four (group 1) or six (group 2) implants were inserted between the maxillary sinuses and immediately loaded by provisional acrylic dentures. Definite screw retained porcelain fused to metal fixed prosthesis were inserted after 6 months. Plaque index, gingival index, probing depth, implant stability, and peri-implant bone loss were measured for both groups at base line (after insertion), 6 months and 12 months after insertion.
Results: The survival rate was 85% and 100% for group 1 and group 2 respectively. Plaque and gingival scores significantly increased with time in group 1 only. At 6 and 12 months, group 1 showed significant higher plaque and gingival scores than group 2. Pocket depth and implant stability increased significantly with time in both groups. Group 1 showed significant higher pocket depth and reduced implant stability than group 2 at all observations. Bone resorption significantly increased after 12 months compared to 6 months in both groups. Group 1 recorded significant higher bone loss than group 2 after 6 and 12 months of prosthesis delivery.
Conclusion: Within the limitations of this study, it could be concluded that All on 6 implant concept is recommended for restoration of atrophied maxilla compared to All on 4 implant concept as it was associated with improved clinical and radiographic parameters after one year.