The Application of Three-Dimensional Printing Model and Platelet-Rich Fibrin Technology in Guided Tissue Regeneration Surgery for Severe Bone Defects

Guided tissue regeneration (GTR), combined with bone substitutes, is a valid treatment option to restore a tooth's supporting apparatus¹  or provide optimal bone support for osseointegrated dental implants. However, for non-contained bone defects, such as one-wall intrabony defects or horizontal bone resorption, healing could be quite limited following this surgical technique.²  Regeneration occurs when systemic and local conditions are favorable; in periodontal treatments, the key elements are space provisions for blood clots, wound stability, and site protection for primary intention healing.³  Creating space and maintaining blood clots with these non-contained bone defects remain challenges for clinicians during the regenerative surgery.

In recent years, bone tissue engineering has tried to promote local favorable conditions by utilizing bone scaffold, growth factors or cells, and this shows great application prospects.⁴  With excellent osteoconductivity, biocompatibility, and bioactivity, three-dimensional scaffolds could be manufactured to promote cell adhesion, proliferation, and vascularization.⁵  The shape of the scaffolds can be designed to precisely match the defect, create a steady repair space, and maintain the blood clot. To further facilitate regeneration, growth factor is added, such as recombinant human bone morphogenetic protein (rhBMP-2)⁵  or recombinant human platelet-derived growth factor-BB (rhPDGF-BB).⁶  Nevertheless, bone tissue regeneration with exogenous materials still needs to be well studied for clinical safety and effectiveness, with added high costs taken into consideration.

In 2006, platelet-rich fibrin (PRF)⁷  was developed from the patient's own blood, which contains a mass of platelets, leucocytes, and growth factors. The use of PRF as a scaffold for the regeneration of both soft and hard tissues has been applied in the clinical field for more than a decade, largely in implant dentistry and periodontal surgery.^8–11  By adjusting centrifugal force, Choukroun's group further modified PRF to advanced platelet-rich fibrin (A-PRF) and injectable platelet-rich fibrin (I-PRF), with more leukocyte infiltration and better osteoinductive ability.^12–15  A simple and similar design of a steady scaffold that can match the alveolar bone defect is made during surgery by integrating grafts A-PRF and I-PRF. Furthermore, for precise awareness of the three-dimensional (3D) osseous volume of the bony defect before surgery, the 3D printing technology has been applied to periodontal bone repair.

The 3D printer was already a commonly accepted diagnostic tool^16–19  but rarely transferred to an operative model in periodontal surgery. In this case, a novel bone construction that was a blend of A-PRF/I-PRF and bone grafts was prefabricated on a 3D printed replica. This patient-specific component can be precisely matched to anticipated bone defects during the operation.

A 36-year-old male patient entered the clinic with the eager desire to preserve his upper right front teeth. Previous dental history revealed that those teeth had increasing mobility over the past year, although the patient had scaling and root planing performed 7 months ago without a systemic periodontal evaluation and therapy. He was generally in good health and had no history of medication or prior hospitalization. Intraoral examination revealed a localized suppuration with Grade 3 mobility detected at tooth No. 7, probing pocket depths ranging from 8–10 mm (Table). Other problems included loss of teeth No. 19, 20, and 30, the presence of a poorly fitting fixed bridge on teeth No. 22–27 with swollen gingiva, suppuration, and Grade 3 mobility of the upper molars (Figure 1). A radiographic examination showed generalized moderate-to-severe horizontal bone loss in both arches. The maxillary right lateral incisor showed a maximal resorption and a pronounced alveolar resorption into the apical area of the root (Figure 2a). Generalized gingival recession and dental calculus were also observed. Based on the thorough clinical and radiographic examinations, a diagnosis of periodontal disease ADA Type IV was made.

To conserve the upper right lateral incisor, initial therapy including oral hygiene instructions, full-mouth supra and subgingival scaling, root planing, fixation of the upper anterior teeth, and replacement of the fixed bridge on teeth No. 22–27 were performed. Furthermore, periodontal surgery was planned to maximally regenerate tooth No. 7. Information about the planned treatment, potential risks, and complications were explained to the patient, and consent was obtained.

Six weeks after initial periodontal treatment, the patient's cone-beam computerized tomography (CBCT) data were acquired and transferred to professional software (Mimics 10.1, Materialise, Leuven, Belgium) to perform a 3D reconstruction of the right anterior maxilla (Figure 3b and c). After post-printing accuracy verification, PolyJet Matrix (Objet Connex350, Stratasys, Eden Prairie, Minn) was used to print the prototype model with Objet Bio-Compatible material (MED610, GROWit, Lake Forest, Calif). The model vividly showed the bony defect around tooth No. 7 (Figure 3a).

Whole blood (30 mL) was drawn from the patient's antecubital vein into 3 sterile plain glass-based vacuum tubes (10 mL/tube) with no anticoagulant. A-PRF (1500 rpm, 14 min) and I-PRF (700 rpm, 3 min) were acquired by centrifugation according to the Choukroun protocol¹¹  (Duo Centrifuge, Nice, France). A-PRF (Figure 4b), jelly-like in consistency, was easily separated from the red corpuscle base. Fibrin clots were then squeezed to obtain A-PRF membranes. One sample was subsequently cut into small pieces and mixed with Bio-Oss artificial bone (Geistlich Biomaterials, Wolhusen, Switzerland) and then packed onto the 3D replica, forming the ideal shape to fill the bone defect; heart-shaped in labial view and fan-shaped in palatal view (Figure 4h and i). After moistening with I-PRF (Figure 4c), the mixture was easily molded and transferred to the patient (Figure 4h through j). The other A-PRF membrane was used later.

The surgery was performed under a standard sterilization protocol and proper asepsis. After local infiltration anesthesia using 4% articaine with 1:100 000 adrenaline, a sulcular incision was made from teeth No. 6–9, a full-thickness flap was reflected and further mobilized to ensure that the primary wound could be closed using tension-free suturing. The defect was thoroughly debrided using Gracey's curettes and irrigated with sterile saline. The alveolar bone review revealed a huge bone defect—the same as in the 3D printed model (Figure 3a)—with a considerable loss of bone around tooth No. 7, especially in the labial and palatal sites where there was bone resorption to the root apex (Figure 3d and e). The surgeon positioned the fabricated bone at the planned site without any changes. The A-PRF membrane was then placed over the fabrication, covering the adjacent bone borders (Figure 4f and g). Finally, the Bio-Gide collagen membrane (Geistlich), which had been cut into the suitable shape using a 3D replica, was positioned to cover the entire defect (Figure 4f, g, and l). The flap was coronally positioned before being tightly sutured (Figure 4n). A periodontal dressing and postoperative instructions about oral hygiene were provided to avoid further trauma to the surgical site.

Reviews were scheduled after 1, 3, 6, 12, and 15 months. No postoperative pain or immoderate swelling was reported, and the patient was satisfied. Periodontal examination after 3 months revealed a reduction in the probing pocket depth and a normal soft tissue contour. The probing pocket depth was reduced to a normal range (Table). Radiographs at 6, 12, and 15 months showed the bone regeneration at the treatment site (Figure 2b through d). Comparing the pre- and postoperative CTs (Figure 3b and c; Figure 5a and b, respectively), 3D bone fill was advanced, with the measured bone volume being 69.93 mm³ (Figure 5c and d).

Insufficient alveolar ridge dimensions due to bone resorption remain a significant challenge to maxillofacial reconstruction. According to the literature, different bone augmentation procedures are available depending on the location, the extension, and the nature of the lesion. Traditionally, appositional bone blocks—including onlay bone grafting, grafting to maxillary sinuses and the floor of the nose, guided bone regeneration, and ridge splitting osteotomies—are predictable and suitable procedures.²⁰  When growth factors are added, it accelerates bone regeneration and could influence several biological function procedures involved in enhancing cell activity, host defense mechanisms, osteoneogenesis, and angiogenesis, as well as in vivo.¹²  Studies have illustrated the osteogenic effectiveness of rhBMP-2 as support of distraction osteogenesis and a treatment of bisphosphonates-related osteonecrosis of the jaw.^21,22  The addition of rhBMP-2 on nonhuman primates mandibles showed rapid increase in hard and soft tissue healing between the bone fragment divided by the distraction osteogenesis. However, these results indicated a need for studies on human model to confirm. Further, successful healing of bisphosphonates-related osteonecrosis of the jaw needs further investigation to suggest more predictable therapeutic option for bone reconstruction, avoiding relapse.

PRF not only contains a three-dimension fibrin scaffold but also delivers a mass of key growth factors such as platelet-derived growth factors, vascular endothelial growth factors, and bone morphogenetic proteins.¹⁰  Remarkably, PRF has now been utilized in over 20 different clinical procedures, including treatment of extraction sockets, periodontal defects, gingival recessions, palatal wound closure, and more.²³  The release time of PRF enables a significant sustained period of at least 1 week and up to 28 days, which is ideal for tissue formation. A-PRF, the advanced PRF contains a larger platelet concentration, BMP-2/7, and leucocyte cytokines, which significantly enhance their antibacterial and osteoinductive actions.^9,10  Specifically, the use of I-PRF could accelerate solidification of A-PRF, which shortens the period A-PRF requires to form a more permanent shape. In this current case, bone grafts and gelatinous A-PRF were blended, combining with liquid I-PRF to achieve a relatively plastic shape conforming to the alveolar bone defect, increasing the possibility of a steady space for bone regeneration. A-PRF could increase the bonding among Bio-Oss bone granules, and the moldability of the bone graft material is enhanced. Moreover, liquid I-PRF could further consolidate the bonding. Gelatinous A-PRF and liquid I-PRF were applied to the bone/tooth interface to improve osseointegration, while A-PRF membranes were positioned under the flaps to guarantee their immediate closure and minimize risk of infection. As a result, significant 3D bone regeneration and clear new attachment gains were observed and have remained stable for more than 1 year. Moreover, vertical regenerated bone was observed around the root surface (Figure 5), which was completely naked before the surgery (Figure 3).

This technique may also be utilized in alveolar ridge augmentation or tooth extraction site preservation to provide adequate bone support of dental implants. Mixing bone graft materials with pieces of A-PRF and its infiltration with I-PRF not only makes it easier to mold, generate optimal bone reconstruction shape (especially for increasing the vertical and horizontal dimension of alveolar ridge deficiencies at implant site) but also reduces the required graft material volume and improves its manipulative qualities.²⁴  According to Del Corso,²⁵  the strategy of combining PRF with bone graft material is a form of in vivo natural tissue regeneration that avoids the disadvantages of many other graft materials that can fail by completely degrading many years following implantation. The combination also supports revascularization and regeneration of bone and soft tissues.²⁶ 

Other authors demonstrated significant advantages in the preservation of postextraction alveolar ridge dimensions with the use of PRF.^27–29  Hauser et al²⁷  found that PRF reduced dimensional changes prior to implant placement when compared to natural socket healing. Simon et al²⁸  also verified enhanced bone healing after placement of PRF matrix in extraction sockets. Kotsakis et al²⁹  employed PRF to provide a better-healed recipient site for accelerated, early implant placement. In addition, PRF was used successfully for sinus lift procedure and gingival recessions.³⁰  With its inherent quality to defend against an infectious environment in the oral cavity and enhanced neovascularization, PRF is able to be exposed after surgery without infection risk.³¹  Thus, adding this technique to routine implant procedure is beneficial for decreasing postoperative discomfort, as well as reducing the most common symptoms such as pain and swelling.³²  With these advantages, A-PRF and I-PRF have already been regularly utilized in bone management after extracting teeth with severe periodontitis. Better wound closure and faster recovery of the soft tissues were observed. Therefore, it is suggested that this technique may be a good option for management of dimensional changes of the alveolar ridge before implantation and even further used around immediate implant placement to pack gaps or harvest enough additional soft tissue around implant site.

Nowadays, many attempts have been made to use the 3D printing technique in bone repair and maxillofacial reconstruction. Tamimi³³  achieved osseointegration of dental implants in bone with 3D-printed synthetic onlays. Konopnicki¹⁹  used a 3D-printed β-TCP and PCL scaffolds seeded with pBMPCs and implanted early into porcine mandibular defects. In the treatment for periodontal bone defect, Rasperini¹⁸  first reported a human case of 3D-printed bioresorbable polymer scaffold based on the preclinical periodontal mimic scaffolds³⁴ ; however, the approach was unsuccessful in the long term. As the author discussed, the selection of biomaterial and effective release of PDGF-BB need further study.

In addition, a directly 3D-printed scaffold might have a long way before clinical application. Thus, in this current study, we proposed a more feasible way to print a jaw model to reveal the defection outside and build a personalized repair “scaffold” on the model with bone grafts and A-PRF/I-PRF. Moreover, the printed replica provided surgeons an opportunity for hands-on surgical rehearsal and reconstruction prior to the real surgery. In this way, surgeons became more familiar with the approach and predicted problems before the complicated surgery. The model released the surgeons from the restriction of a small oral cavity; they could design and even “operate” on the precise model, which is also beneficial in the dental implant surgical setting. With the 3D printing model, the surgeon can measure the bone defect directly and cut a specific membrane fitting the diverse morphology of the defect, greatly lowering the procedural complexity and raising the broader application of regenerative periodontal surgery and alveolar ridge augmentation in implant surgery.

However, no controls were included in this limited case report, and long-term outcome of the procedure is unknown. For further analysis, controlled studies are needed to evaluate the extent of benefit derived when A-PRF/I-PRF is used. Continued followup will be necessary to investigate long-term stability of the newly regenerated bone around the natural tooth. For a more clinical application, this original method can be used to obtain an ideal alveolar ridge contour to enhance both peri-implant aesthetic and function. It might be more meaningful to print a grafting material or a membrane for high cost of 3D print, but the autologous use combined with 3D-printing presents itself is a promising intermediate step for tissue regeneration. As autologous preparation remains the safest and most economical choice for both patients and clinicians, it is expected that this method will be considered conventional in the near future. Moreover, it can be further improved and more effective, which might even eliminate the use of membranes. To generate an accurate personalized reconstruction, 3D printing technologies for use in periodontal surgery and A-PRF/I-PRF fabrication should be investigated further, ensuring that future designs of periodontal regeneration surgeries consider both hard and soft tissue defects using a desirable, controlled morphology.

Abbreviations

3D

three dimensional

A-PRF

advanced platelet-rich fibrin

CBCT

cone-beam computerized tomography

GTR

Gguided tissue regeneration

I-PRF

injectable platelet-rich fibrin

PRF

platelet-rich fibrin

rhBMP-2

recombinant human bone morphogenetic protein

rhPDGF-BB

recombinant human platelet-derived growth factor-BB

The authors would like to thank Prof Professor Xu Mingen (Center Laboratory of Biomanufacture and Tissue Engineering, Hang Zhou Dianzi University) and his group for their excellent assistance and providing free materials to be used in the study.

Funding came from Science and Technology Project of Zhejiang Province, China (2017C33141) and National Science Foundation of Zhejiang Province, China (LY16H140002). The authors report no conflicts of interest.