In our study, PRF membranes were additionally to collagen membranes used to cover the CAD-CAM mesh. The aim of this clinical approach was to improve and accelerate wound healing. The results with the low exposure rates and the sufficient augmentation heights indicated that these PRF membranes are a promising technique. However, due to low case number in the control group without a PRF membrane, definitive conclusions are not possible. The positive effects of PRF regarding wound healing may be explained by the contents of the PRF clot. These clots contain stem cells, fibrin, platelets, and leucocytes [26, 27]. Furthermore, PRF membranes have a sustained release of high quantities of the growth factors TGFbeta-1, PDGF-AB, and VEGF and coagulation matricellular glycoprotein (thrombospondin-1, TSP-1) during 7 days [27]. Therefore, PRF is a biodegradable scaffold that promotes the development of microvascularization and epithelial cell migration to its surface [28, 29]. There are several clinical studies and systematic reviews that show the promising potential of PRF for bone and soft tissue regeneration [28, 30, 31]. Torres et al. examined the effect of platelet-rich plasma in preventing mesh exposure by using it to cover conventional meshes [32]. In this study, 43 alveolar bone augmentations with the mesh technique using anorganic bovine bone as graft material were performed. In half of the patients, the meshes were covered with platelet-rich plasma, whereas in the other half, the meshes were not. The results showed that mesh exposure was significantly less in the platelet-rich plasma group as well as that bone augmentation was higher in the platelet-rich plasma group than in the control group. In conclusion, these results promote the use of PRP/PRF in augmentation procedures.

Besides the use of membranes, the application of a sufficient incision technique is crucial to avoid dehiscences. In our study, augmentations performed with a modified poncho incision had lower exposure rates than augmentations performed with a mid-crestal incision. All the dehiscences appeared in the area of the suture. Therefore, positioning the margin of the wound in the vestibulum and in distance to the mesh seems to reduce the risk for an exposure of the TM as the margin of a wound represents the most important nutritional structure for survival and the basis for reliable wound healing [33, 34]. In addition, exposure rate in the maxilla was significantly higher than in the mandible. This could be explained with the higher augmentations in the maxilla in our study. In our study, both craniofacial and iliac crest bones were used for augmentation procedures. This may influence later bone resorption and long-term stability. However, a recent influence of the used material on augmentation success was not seen.