BackgroundPrevious studies have shown that adequate thickness or initial augmentation of soft tissue has a positive effect on the stability of peri-implant bone. This randomized, controlled trial aimed to evaluate the influence of augmenting soft tissue with platelet-rich fibrin (PRF) on crestal bone and soft tissue around implants.MethodsAfter randomization, 31 fully threaded titanium implants were inserted in 31 patients (16 men and 15 women) in the lower mandible using a split-flap technique. In the test group (10 patients), mucosa was treated with a PRF membrane. In the control group (21 patients), implantation was realized without soft tissue augmentation. Tissue thickness was measured at point of implant insertion (baseline) and at time of reentry after 3 months. Standardized digital radiographs were obtained for evaluation at time of implant placement, reentry after 3 months and at a 6-month follow-up. Data was analyzed by an independent examiner.ResultsAfter 6 months, all 31 implants were osteointegrated. Soft tissue augmentation with PRF led to a significant tissue loss. In the test group, the crestal tissue thickness dropped from 2.20 mm ± 0.48 SD at baseline to 0.9 mm ± 1.02 SD at reentry, whereas crestal mucosa in the control group showed higher stability (2.64 mm ± 0.48 SD at baseline to 2.62 mm ± 0.61 SD at reentry). For ethical reasons, the test group was terminated after 10 cases, and the remaining cases were finished within the control group. In the test group, radiographic evaluation showed a mean bone loss of 0.77 mm ± 0.42 SD/0.57 mm ± 0.44 SD (defect depth/defect width) on the mesial side and 0.82 mm ± 0.42 SD/0.62 mm ± 0.36 SD (defect depth/defect width) on the distal side. In the control group, a mean bone loss of 0.72 mm ± 0.61 SD/0.51 mm ± 0.48 mm (defect depth/defect width) on the mesial and 0.82 mm ± 0.77 SD/ 0.57 mm ± 0.58 SD (defect depth /defect width) on the distal side was measured.ConclusionsWithin the limits of this study and the early determination of the test group, this study concludes that soft tissue augmentation with PRF performed with a split-flap technique cannot be recommended for thickening thin mucosa. Further studies focusing on different techniques and longer follow-ups are needed to evaluate whether PRF is suitable for soft tissue thickening.