Implant Site Preparation Application of Injectable Platelet-Rich Fibrin for Vertical and Horizontal Bone Regeneration: A Clinical Report

A vertical alveolar bone defect in partially edentulous patients can present a major challenge for guided bone regeneration (GBR) in terms of anatomical limitations and technical difficulties. The presence of posterior anatomical structures, such as maxillary sinus and mandibular inferior alveolar nerve, potentially limit the bone quantity available for proper implant placement. A large interarch space further complicates prosthetic coronal length and form and thus presents possible poor crown-implant ratio for appropriate esthetics and function.^1,2  There have been numerous GBR techniques to reconstruct vertical alveolar ridge deficiencies, either simultaneously with implant placement or before implant placement. Various GBR techniques include a titanium reinforced nonresorbable barrier membrane in conjunction with placement of titanium dental implants,³  an extraoral mandibular distractor,⁴  and onlay bone block grafts.⁵  Although GBR if successful can reproduce an augmentation of osseous macro- and microstructures that are similar to native bone, promising long-term survival of dental implants,⁶  there is a high rate of complications in GBR procedures.^7,8  One of the major complications that often leads to failure of the entire GBR graft is early membrane dehiscence and infection.⁹  To overcome this problem, the tenting screw technique with collagen membrane enhanced with leukocyte- and platelet-rich fibrin (L-PRF) was introduced.^10,11  Platelet-rich fibrin (PRF) is an autologous platelet concentrate with leukocytes and growth factors entrapped in a fibrin matrix.¹²  Intrinsic growth factors in PRF, in particular platelet-derived growth factor (PDGF), transforming growth factor β1 (TGF-β1), and vascular endothelial growth factor (VEGF), are known to stimulate cell migration, differentiation, and proliferation.^12–15  Success of any bone augmentation procedure depends on the initial stability of bone graft. Until the new bone is formed, the grafted area should be stabilized. Additionally, the bone graft materials should be easy to handle and able to maintain appropriate ridge contour during membrane and flap manipulation and during the period of initial healing.¹⁶  i-PRF can transform from a liquid stage to a solid stage. In the liquid flowable stage, i-PRF can be combined with the particulate bone grafting material. After complete clotting, this combination can be easily manipulated and applied to the surgical site to form appropriate ridge contour. This clinical report presented a clinical application of GBR using i-PRF in combination with particulate bone graft and L-PRF.

A 55-year-old Asian woman presented with a chief complaint of “I need implants to replace my lower back teeth. Also, my tooth next to the space is very mobile and sometimes painful.” The patient lost her mandibular right molars and second premolar because of periodontal disease. The mandibular right first premolar also had a history of periodontal treatment. The patient was in good general health, with no contraindications for bone augmentation and dental implant therapy. She was currently wearing a mandibular interim acrylic partial denture to support her occlusion and to maintain the positions of her remaining teeth. The clinical examination showed that the mandibular right first premolar tooth had a deep distal pocket of approximately 11 mm with a third-degree tooth mobility. The interarch space in the mandibular posterior area appeared too large to be restored because of vertical alveolar ridge resorption (Figure 1a). CBCT scans showed severe vertical and horizontal bone defects. In addition, there was only ∼2–3 mm of crestal bone remained above the inferior alveolar canal (Figure 1b and c). A diagnosis of localized severe periodontitis of the mandibular right first premolar tooth was made. The tooth was therefore deemed unrestorable. Before the surgical treatment, risks and benefits of different treatment options were discussed. The patient elected to extract the mandibular first premolar and to have ridge augmentation followed by a delayed implant placement procedure. The tooth was extracted. Crestal and distal vertical incisions were made. A full-thickness flap was performed to visualize the remaining bone defect and to explore the distance between the graft site and the mental foramen. A small round bur was used to make vascular channel perforation into the lateral alveolar ridge wall. Six titanium tenting screws, 8–10 mm in length, were placed on buccal and lingual sites of the defect, 3 screws for each site. The screws were inserted at least 3 mm into bone for adequate stability. Periosteal releasing was performed on buccal and lingual flaps to allow expansion of the flap and ease the flap closure without too much tension. The i-PRF preparation adopted from Thanasrisuebwong et al¹⁵  was used. Briefly, peripheral blood was collected and immediately centrifuged at 700 rpm for 3 minutes (PC-02 Centrifuge, Process Ltd, Nice, France) at room temperature. After centrifugation, red i-PRF, referring to the plasma from both the upper yellow zone and the buffy coat, was harvested.¹⁵  The red i-PRF was combined with the particulate of Bio-Oss (Geistlich Pharma) and MinerOss (Bio-Horizons) at a 1:1 ratio by volume, and “sticky bone” was formed. The sticky bone was cut into small blocks and adapted and shaped to an ideal alveolar ridge morphology (Figure 2a–d). A combination of collagen membrane and L-PRF was used to prevent soft tissue migration into the grafting site. A resorbable collagen membrane (RCM6, ACE Surgical Supply) was placed first onto the grafted materials. Then L-PRF, prepared by centrifuging the peripheral blood at 2700 rpm for 12 minutes, was placed on top of the collagen membrane. A primary closure was achieved with minimal tension in the flap (Figure 3a–d). The patient was advised not to wear her interim prosthesis after the surgery. Chlorhexidine mouth rinse (twice a day for 2 weeks) and amoxicillin (500 mg 4 times a day for 7 days) were prescribed. The patient was also advised to use acetaminophen or ibuprofen as needed for pain. No narcotics were prescribed. In addition, a soft diet and cold temperature food were prescribed for 48 hours after the surgery. The patient was scheduled for postoperative evaluations at 2 weeks and 2 months after the surgery. Eight months after surgery, CBCT images were taken to evaluate the result of bone augmentation. The result showed a remarkable achievement of vertical and horizontal bone augmentation appropriate for implant placement (Figure 4). A comparison of before and after the ridge augmentation is shown in Figure 4a–c. Figure 4d demonstrates the measurement of pre- and postoperative CBCT scans. More than 10 mm of grafted bone gain was observed. The interarch space was improved into an appropriate prosthetic space after bone augmentation (Figure 5a). Nine months after bone augmentation surgery, the implant placement surgery was performed. Two endosseous implants (4.1 × 10 mm and 4.8 × 10 mm, Straumann Bone Level Tapered, Straumann Group) were placed. A midcrestal incision was made, and a full-thickness flap procedure was performed. The GBR procedure resulted in good bone quality and quantity of the grafted site. Approximately 5–11 mm of vertical and horizontal bone gain was observed based on the height of the tenting screws (Figure 5b and c). The grafted bone was harvested using a trephine bur for histologic examination during the implant osteotomy site preparation (Figure 6a and b). The histology showed a new normal physiologic bone formation around the implant site (Figure 6c and d) and at the osteotomy site (Figure 7a and b). The implants were placed, and resonance frequency analysis (RFA) using Osstell (Osstell) was performed. The newly placed implants demonstrated a high value of the implant stability quotient (ISQ) (Figure 7c and d). The implants were allowed to heal and osseointegrate. A second-stage surgery was performed, and the definitive impressions were made 3 months after implant placement. Four months after implant placement, a definitive fixed partial denture was inserted. An appropriate crown height and width were obtained through bone augmentation (Figure 8a and b). Periapical radiographs were obtained at the surgery visit (Figure 8c) and at the prosthetic insertion visit (Figure 8d). A follow-up periapical radiograph were also obtained at 24 months after the insertion of the definitive restoration (Figure 8e) to evaluate the regenerated bone. The bone level around the implants at the follow-up visit was similar to the bone levels at the time of implant placement surgery and at the prosthetic insertion visit.

This clinical report is perhaps one of the first to demonstrate GBR of the large vertical and horizontal bone defect with a combination of sticky bone,^17,18  xenograft and allograft particulate bone, and i-PRF with L-PRF and collagen membrane. The key to success in this patient might attribute to multiple factors, most importantly the physical and biological properties of particulate bone using i-PRF, the tenting screw technique, and the L-PRF/collagen membrane barrier. First, the combination of i-PRF and particulate bone graft or sticky bone is easy to handle, especially when it is used in a large defect as in this case. Without sticky bone, it can be difficult to contour the graft and maintain the shape of the graft during flap closure and throughout initial healing.^17,18  Second, the red i-PRF has been shown to have both valuable cells and growth factors. Growth factors such as PDGF, VEGF, and TGF-β1 are shown at a high level compared with yellow i-PRF.¹⁵  These may have enhanced angiogenesis, cell migration, proliferation and differentiation, which are beneficial to bone regeneration process. Third, to treat a non–space-maintaining defect, the tenting screw can help support the membrane and flap and therefore function as a framework and prevent the graft collapsing.¹¹  The quality of soft tissue, especially keratinized mucosa, in the posterior mandibular area was often poor compared with the others area in the oral cavity. Placement of the collagen membrane together with L-PRF in this area can enhance bone regeneration procedure through improving tissue integration and vascularization. This can reduce the rate of wound dehiscence, a major issue in GBR procedures. The PRF provides a 3-dimensional scaffolding structure that is conducive to osteogenesis through a thin and flexible fibrin network that enhances cell migration and cytokine attraction.¹⁹  The fibronectin-rich PRF has shown to improve osteoblastic adhesion to the extracellular matrix.^20,21  Furthermore, while the bone regeneration occurs, the fibrin matrix of PRF is gradually and continually expressing the cytokines through the PRF remodeling process.²²  This process has shown to improve cell proliferation during osteogenesis.^23,24 

This clinical report proposed a hypothesis that a GBR protocol with particulate bone integrated with i-PRF together with L-PRF and collagen membrane can successfully restore large vertical and horizontal bone defects. This combination may provide an optimal environment for bone regeneration, enhance neovascularization, and promote cell behavior for bone regeneration. This protocol should be used with caution in selected cases. A longitudinal study with a larger sample size is needed to confirm whether this protocol can be applied to the general population.

Abbreviations

L-PRF:

leukocyte- and platelet-rich fibrin

PDGF:

platelet-derived growth factor

PRF:

platelet-rich fibrin

TGF-β1:

transforming growth factor β1

VEGF:

vascular endothelial growth factor

The authors thank Dr Ting-Ling Chang, Dr Peter K. Moy, and Dr Joan Pi-Anfruns for kind support of this work.

The authors declare no conflicts of interest.