*2.1.2 Natural biomaterials natural include xenogeneic bone, natural coral, and allogenic bone*

Xenogeneic bone (xenograft) is most commonly derived from pigs or cows. Inorganic bovine bone retains a bone spatial structure, giving it osteoconductive properties. These products are presented in a lyophilized form [9, 10]. Natural coral is composed of 99% calcium carbonate. After thermal treatment, it retains a porous structure that gives it osteoinductive properties [9, 10]. Allogeneic bone substitutes are produced from femoral head bone taken from fresh human cadavers. Compared to autogenous bone, they have the advantage of not requiring bone harvesting from the patient (as autogenous bone harvesting carries an increased risk of postoperative morbidity). There are two types of allografts depending on the treatment applied to the harvested bone: lyophilized allograft called Freeze-Dried Bone Allograft (FDBA) and demineralized lyophilized allograft called Demineralized Freeze-Dried Bone Allograft (DFDBA) or Demineralized Bone Matrix (DBM). To obtain FDBA, the harvested bone undergoes a series of treatments [11]: elimination of residual muscular and fibrous tissues, size reduction to obtain particles of 5 mm, first decontamination, microbial treatment with antibacterial, antifungal and antimycotic solutions, freezing in liquid nitrogen at −80°C, dehydration by lyophilization, second size reduction of particles, packaging in a sterile container, and finally sterilization with gamma rays to reduce the risk of contamination. FDBA will mainly serve as a matrix for bone regeneration: osteoconduction.

For the DFDBA, the treatment sequence is similar but with an additional demineralization phase in a bath of hydrochloric acid following the second reduction in particle size. The DFDBA has osteoconductive properties, meaning it serves as a scaffold for the colonization of the recipient site by various types of cells and growth factors, and some authors have shown that it has osteoinductive properties, meaning it may allow for new bone formation. This is due to the presence of Bone Morphogenetic Proteins (BMPs) within the bone matrix [12, 13]. As the bone is resorbed, growth factors including BMPs, which belong to the TGF β superfamily and were first isolated in the 1960s by American orthopedic surgeon Marshal Urist, are released. BMPs, especially isoforms 2, 3, 4, and 7, play a crucial role in bone healing by stimulating the differentiation of mesenchymal stem cells into bone cells [13].

The ability of DFDBA to be osteoconductive and osteoinductive is influenced by various factors such as the age of the donor (better between 41 and 50 years for men and 51 and 60 years for women), the particle size which should be between 500 and 710 μm to ensure optimal effects, the residual calcium content (optimal osteoinduction occurs when the percentage of residual calcium is 2%) [14], as well as the methods of preparation, sterilization, and preservation [15]. It has been shown that there is a large variation in the amounts of extracted proteins within different lots of DFDBA, and the authors have hypothesized that some proteins may be degraded within certain lots of DFDBA or present in too small quantities within the bone matrix to be detectable by their method [13].

*Particulate Allografts (DFDBA) Combined with Platelet Concentrate: An Effective… DOI: http://dx.doi.org/10.5772/intechopen.112929*

#### *2.1.3 Autologous platelet concentrates as surgical adjuvants*

The use of autologous platelet concentrates (PRP and PRF) in oral and implant surgery aims to accelerate and improve the healing process, particularly in surgical procedures for bone regeneration [16]. Platelet Rich Plasma (PRP), introduced by Marx et al. in 1998, is obtained through two successive centrifugations in tubes containing citrate dextrose A anticoagulant (to prevent platelet activation and degranulation). The platelet concentrate is instantaneously gelled by the addition of bovine thrombin, recombinant human thrombin, or recombinant human tissue factor, which triggers platelet activation and fibrin polymerization [17].

Authors have developed a simplified protocol to obtain an autologous platelet concentrate without the use of anticoagulants or thrombin, called Platelet-Rich-Fibrin (PRF) [18]. Venous blood collected without anticoagulant is immediately centrifuged for 10 to 12 minutes at 2700–3000 rpm. The authors obtain three successive layers from the bottom to the surface of the tube: red blood cells, a PRF clot rich in platelets, and on the surface, acellular plasma rich in fibrin (**Figure 3**).

The natural mechanism of coagulation is triggered when blood comes into contact with the glass tube surface, leading to the formation of a fibrin clot rich in platelets and white blood cells without any biochemical modifications, without the addition of anticoagulant, thrombin, or calcium chloride. PRF can be used in the form of a gel or membrane.

After centrifugation, the portion rich in platelets can be mixed with the biomaterial (**Figure 4**), while the portion rich in fibrin can be transformed into a membrane by applying pressure between two compresses (**Figure 5**).

#### **Figure 3.**

*Blood tubes collected from the patient without the addition of anticoagulant are placed in a centrifuge and spun at 3000 rpm for 10 minutes. This results in a material consisting of a portion rich in fibrin (in yellow), a portion rich in erythrocytes (in red), and a PRF clot rich in platelets located between them.*

#### **Figure 4.**

*300–500 μm particulate demineralized bone matrix (DFDBA). The platelet-rich portion is located at the boundary between the fibrin-rich and red blood cell-rich portions. It can be cut and mixed with DFDBA.*

#### **Figure 5.**

*The fibrin-rich portion can be manually pressed between two compresses to obtain autologous fibrin membranes.*

PRF has the advantage over PRP of being entirely autologous, and it has been shown to release platelet growth factors over a period of at least 1 week [19], unlike PRP, which releases them within an hour of preparation [20]. Due to its ease of obtention, purely autologous nature, and the fact that the coagulation cascade occurs physiologically without the addition of bovine thrombin, PRF tends to replace PRP currently.

Platelet concentrates contain fibrinogen, cell adhesion molecules (fibrin, fibronectin, and vitronectin) that play a role in cell migration and osteoconduction, as well as growth factors such as PDGF (Platelet-Derived Growth Factor), TGF-β, EGF (Epithelial Growth Factor), IGF (Insulin-like Growth Factor), and VEGF (Vascular Endothelial Growth Factor) [19]. In oral implant surgery, platelet concentrates are used as adjuvants to bone reconstruction procedures. The aim of their use is to accelerate and improve the healing process, particularly in terms of bone graft integration and regeneration [21].

They are used in various clinical applications, such as maxillary sinus augmentation, alveolar ridge augmentation, mandibular reconstruction, treatment of periodontal pockets, post-extraction alveolar bone filling, and dental implant osseointegration [22–25]. Studies have shown the beneficial effects of platelet concentrates, such as improved soft tissue healing [26, 27]. However, the improvement of bone regeneration through platelet concentrate administration is still controversial [28, 29]. The lack of standardization in platelet concentrate obtention protocols may explain the lack of concordance in various studies, and the kinetics of growth factor delivery is still poorly understood, with large variations observed among patients and even within the same patient depending on the time of day of the blood collection (circadian variations in platelet concentration exist) [18, 19]. Furthermore, the contradictory results reported in the literature regarding the benefits of using platelet coagulation factors can be partly explained by the fact that these results come from clinical studies for some and animal studies for others, and it is difficult to extrapolate results obtained from one species to another [30, 31].

On the other hand, the minimum platelet concentration required to obtain a blood clot meeting the criteria for PRF is not well defined by the authors. However, they agree that clinical benefits can be obtained for a platelet concentration of 1 million/μL of plasma (4 to 7 times the baseline level) [32].

*Particulate Allografts (DFDBA) Combined with Platelet Concentrate: An Effective… DOI: http://dx.doi.org/10.5772/intechopen.112929*

#### *2.1.4 Use of a combination of allograft and platelet concentrates*

The benefits associated with the use of a combination of biomaterials, such as allograft and platelet concentrates, are currently still controversial. One study [33] compared the use of a bone allograft alone with a bone allograft combined with platelet-rich fibrin (PRF) for maxillary sinus augmentation in 9 patients. According to the authors, the combination of allograft and PRF allows for faster bone maturity, which enables dental implant placement at 4 months postoperatively compared to 8 months for the control group.

The clinical benefits of platelet concentrates combined with demineralized freezedried bone allograft (DFDBA) in bone regeneration have been demonstrated in the treatment of periodontal pockets [34, 35], but have not yet been evaluated in oral surgery in a large cohort of patients.

#### **2.2 Surgical techniques**

#### *2.2.1 Principles of post-extraction alveolar ridge preservation*

Post-extraction alveolar ridge preservation techniques are based on the principle of guided bone regeneration. The principle involves placing a membrane between the soft tissues and the alveolar bone contours. This membrane prevents the passage and proliferation of epithelial cells and connective tissue into the alveolus, thus ensuring a space that can be colonized by osteoprogenitor cells. This prevents the growth and invagination of soft tissues into the extraction site during healing, thus allowing for adequate bone preservation. In addition to its role in maintaining space, the membrane stabilizes, protects, and ensures the containment of the blood clot and, optionally, the graft material that has been inserted into the alveolus. The biomaterial placed in the dental alveolus under the membrane immediately after extraction will constitute a structure whose architecture will guide and support colonization by osteoprogenitor cells and, thereby, bone regeneration. The Alveolar Ridge preservation Technique Using DFDBA and Platelet Concentrates The Implantology Clinic at Erasme Hospital routinely uses a combination of DFDBA bone bank and PRF platelet concentrates in the form of gel and membrane during post-extraction alveolar ridge preservation procedures. At the start of surgery, 6 to 8 tubes of 10 ml blood without anticoagulants are collected from the patient. Centrifugation at 3000 rpm for 10 minutes or 2800 rpm for 12 minutes is performed according to a protocol described in a previous study [18]. The platelet-rich portion (which is at the boundary between the yellow fibrin-rich part and the red erythrocyte-rich part) is collected and mixed with particulate allograft (DFDBA) with a particle size of 300 to 500 μm. The fibrin-rich portion is manually pressed between two compresses to obtain autologous fibrin membranes. Atraumatic extractions are performed, and immediately thereafter, the alveolar ridge is filled with the DFDBA-platelet concentrate mixture. Closure of the alveolus is ensured by the fibrin membrane, and resorbable sutures (Vicryl® 3/0) are performed (**Figure 6**).

Immediately after atraumatic extraction, the alveolar ridge is augmented using a mixture of DFDBA and platelet concentrates. The alveolar ridge is closed using a fibrin membrane and absorbable sutures (Vicryl® 3/0). During the post-operative period, 600 mg of ibuprofen three times a day and 500 mg of paracetamol are prescribed for pain relief. All patients receive 1 g of amoxicillin twice a day for 4 days or 300 mg of clindamycin three times a day if allergic to penicillin, for 4 days. This technique provides good results in terms of preserving post-extractional bone volume [36].

#### **Figure 6.**

*Post-extractional alveolar ridge augmentation technique as practiced in the Implantology Clinic of Erasme Hospital.*

#### **Figure 7.**

*Procedure for maxillary sinus grafting as performed at the implantology clinic of Erasme Hospital. A bone flap is made with piezoelectric surgery on the antero-external wall of the right maxillary sinus, followed by horizontal tipping while lifting the Schneider membrane of the sinus. Autologous fibrin membranes are placed on the internal, anterior, and posterior walls of the cavity, and then a mixture of DFDBA and autologous platelet concentrates is placed in the cavity. Autologous fibrin membranes are then applied outside the graft, and the mucoperiosteal flap is sutured in place.*
