The PRGF system (Plasma Rich in Growth Factors) according to Anitua also utilizes the positive effect of growth factors and proteins on the wound healing of hard and soft tissue. There is no need for bovine thrombine, only accelerated by CaCl2.
In this process the autogenous blood is also centrifuged, however, in contrast to the conventional centrifugation method, four fractions are obtained instead of three (BTI centrifuge, Biotechnology Institute, Miňao, Spain). Besides the three known plasma fractions, this process produces autogenous fibrin as a fourth phase.10 Acting as a membrane, this fibrin after cross-linking with its excellent elastic and blood-clotting properties, serves as wound coverage and supports haemostasis during the first few hours after surgical intervention, and later on as lining for the soft tissue. Fibrin protects the wound underneath the mucosal flap and reduces the risk of sutural dehiscence. By employing the PRGF technique it thus seems possible to also promote wound healing long-term by applying growth factors and fibrin to the surgical site.
The combination of PRGF with autogenous bone transplants can have a positive effect on the trabecular bone structure and on bone regeneration, and apparently accelerate the formation of mature bone substance.11 The joint use of the PRGF technique together with xenogenic bone grafting materials demonstrates advantages in handling and the application of the mixture, as well as apparently leading to an improvement and acceleration of osteoconductive effects during the healing period.12
If bone is lost for reasons of trauma, infection or resorption processes following tooth loss, the provision of a sufficiently dimensioned implant site can usually only be achieved by surgical intervention in conjunction with augmentative procedures.13
Autogenous, allogeneic or xenogenic materials can be used for the surgical regeneration of bone defects. Autogenous bone is still considered as the gold standard for replenishing defects and bone regeneration; however, it is subject to limitations due to the relatively low availability of donor bone. The additional surgical stress for the patient when a second surcigal site for harvesting sufficient amount of bone becomes necessary and possibly related postoperative complications are disadvantageous as well. Bone grafting can lead to a so-called “donor-site morbidity” which presents as postoperative hematomas, secondary bleeding, infections and impaired wound healing. These limitations led to the search for alternatives to autogenous bone.
Today, a number of xenogenic products are available. These may be of bovine origin, the bones of cattle often being the source product. According to the manufacturers of bovine products the risk of prion transfer is excluded by proper professional removal of organic material during processing. Despite the good clinical results with these materials it is also evident that resorption or remodeling processes could not be observed in the grafts, even after longer periods in-situ.14 Thus, the grafted particles are only surrounded by new bone, like foreign matter, but not replaced by autogenous bone.
Also of xenogenic origin, but derived from plants, is the bone regeneration material FRIOS Algipore, which is obtained from the calcium carbonate structure of the red algae Corallina officinalis and Amphiroa ephedra. This so-called phycogenic hydroxylapatite consists of a honeycomb-like structure with high microporosity and a pronounced network of pores. The basic structure of Algipore is reminiscent of the Havers and Volkmann channels in natural bone.15 This spatially interlinked structure facilitates the formation of vessels from the surrounding bone and promotes osteoconduction. Algipore differs from grafts of bovine origin by its specific surface structure coupled with its osteoconductive properties. Compared with Algipore, these hardly provide porosity, or only at a superficial level. It is this porosity which appears causal for the good osteoconductive properties of Algipore and its sufficient resorption by local bone.14
Clinical long-term results for sinus floor elevations have demonstrated that the joint use of platelet-rich plasma with phycogenic hydroxyapatites in combination with implant placement into the lateral maxilla, already resulted in very good bone regeneration of the implant site after six months and led to high survival rates of the implants which are comparable and in some cases superior to the results achieved with pure autogenous derived bone grafts.16
Fig. 1: An overview of the initial X-ray findings: tooth 16 is missing and is to be
replaced by an implant. Owing to the location of the maxillary sinus, the bone
volume available is limited and a sinus floor elevation indicated. Using a mixture
of osteoconductive bone forming material (FRIOS Algipore, DENTSPLY Friadent) and
PRGF, the bone cavity is stabilized first and supports the formation of new bone
in the elevated sinus. Implant placement can be carried out simultaneously with
the maxillary sinus graft as the primary stability of the selected XiVE S plus
implant (DENTSPLY Friadent) is ensured.
Fig. 2: PRGF was obtained from the patient’s centrifuged whole blood. The
third phase contains the highest portion of components essential for improved bone
and wound healing. Algipore is mixed with PRGF. Hereby, the good handling
was demonstrated as a result of the plastic properties of this mixture (after
20 min. the cross-linking of the fibrine is terminated). Even when small disruptions
of the Schneiderian Membrane occurs, FRIOS Algipore remains in place due to the
fact that it sticks within the blood clood.
Fig. 3: Situation following sinus floor elevation and preparation of the implant site: the mixture of Algipore plus PRGF is applied to the bone via the previously
prepared lateral window.