Guided bone regeneration in the anterior maxilla after tooth extraction and implant removal with sticky bone and L-PRF membrane in two surgical approaches

The main requirement for the insertion of dental implants is a good bone and gum condition and guided bone regeneration (GBR) combines grafts and membranes to increase such parameters in tissue deficiencies and thus achieve treatment success. This clinical case reports the oral rehabilitation of the anterosuperior area by the association of bone graft, autologous membrane and implantodontic therapy. Female patient, 45 years old, normosystemic, reported aesthetic complaint and implant mobility in the maxilla. Upon clinical and radiographic examination, an implant was diagnosed in the region of tooth 11 with unfavorable esthetics, mobility, inadequate prosthesis and bone loss, and tooth 22 with suppuration, fracture line and periapical radiolucency. The treatment consisted of removal of the implant and tooth 22, with immediate GBR using filling with Bio-Oss® and liquid leukocyteand platelet-rich fibrin (L-PRF) and coating with L-PRF membrane. After 7 months, the second GBR was performed with the installation of 2 dental implants. After 6 months, healers were placed and 20 days after the adaptation of the provisional implant-supported single prostheses. There was a good gain in thickness and mucogingival limit, bone dimensions in height and thickness, and the case continues to be followed up until the final prosthesis is completed. This case suggests that sticky bone and L-PRF membrane can contribute to multiple GBR in the anterior maxillary region, favoring bone gain and osseointegration.


Introduction
The harmony of the smile in the anterior region of the edentulous maxilla or with an indication for dental extraction challenges the dentist, who seeks the integrity of the support structures for the satisfactory placement of osseointegrated implants and dental prostheses on the implants (Souza et al., 2015). Gingival and bone contours are essential for good esthetics, using surgical techniques for bone and/or gingival filling and implant placement which include: greater vertical apical positioning, distance ≥ 3 mm to another implant or adjacent tooth, adaptation to 2 mm of the cement-enamel junction of the adjacent tooth and fixation in bone dimension to ensure the primary stability of the implant (Tomm & Mezzomo, 2017;Souza et al., 2015).
The maintenance of the alveolar ridge in height and thickness is limited, as the local blood supply decreases with tooth and periodontal loss and there is more accelerated bone atrophy, especially of the thin buccal wall (Ponte, Araújo, Araújo & Castro-Silva, 2019). Some unsatisfactory results in the medium and long term with implants in the esthetic zone may be related to patients with a high smile line, due to the darkening of the gingival margin after rehabilitation, as well as the verticalization of the incisors with aging, whereas the implants seem to become more protrusive (Sobral, 2020).
Whether for technical or physiological reasons, the failure of a dental implant, which needs to be removed or is lost, is another complication that must be diagnosed in time to avoid continuous alveolar bone loss and great aesthetic damage, with a relationship between early failures and overheating, contamination, surgical trauma, low bone quantity or quality, lack of primary stability and indication of incorrect immediate loading, while late failures would result from periimplantitis, occlusal trauma and overload (Levin, 2008). The implant site can be a predictor of its survival, as verified by Fouda (2020) in the systematic review of international thematic studies, with an average of 6.2% of failures in the anterior region of the maxilla greater than 2.5% found in the anterior region of the mandible, related to low maxillary bone density. In a Brazilian sample of 166 patients, there were higher failure rates of grafts and implants in the anterior region of the maxilla (2.4% and 2.6%, respectively) and in patients older than 40 years (Salmen et al., 2017).
Natural ceramic bone grafts and collagen barrier membranes, both of animal or xenogeneic origin, are the most used dental materials for the purpose of Guided Bone Regeneration (GBR) Araújo et al., 2020;Liu & Kerns, 2014). In oral surgery, this technique contributes to the treatment of small to moderate bone defects resulting from periodontal or endodontic disease, filling the socket after extraction, lifting the maxillary sinus or rehabilitation of bone atrophy before implants and even large bone defects caused by trauma, anodontia, congenital deformities, pathologies and infections involving the maxillofacial complex .
Over the last four decades in Brazil, multidisciplinary and translational research has sought to develop and characterize different biomaterials for clinical use . In this country, there is high professional satisfaction and its cost is considered moderate, despite the low participation of the patient in choosing the product and the imported origin is greater than national, with greater application in private practice and without associated inflammatory or infectious complications . Despite the large multifactorial demand for orofacial bone loss, the use of biomaterials for GBR in public health is still incipient, given the chronic underfunding in the care network for this type of therapy in Brazil (Castro- Silva, Lima & Granjeiro, 2014).
Leukocyte-and platelet-rich fibrin (L-PRF) is an autologous matrix obtained by immediate centrifugation of blood collected from the patient in the dentist's office, according to the Resolution of the Federal Council of Dentistry n. 158/2015, exhibiting a high concentration of growth factors and defense cells that provide angiogenic, osteogenic and antibacterial effects, reducing surgical sequelae of pain and infection (Castro-Silva, 2018;Takamori, Teixeira, Menezes, Carias & Borojevic, 2018). The absence of ethical conflicts, non-immunogenicity, high plasticity for different host beds, low morbidity and practicality of obtaining it can make the treatment with PRF very attractive (Ponte et al., 2019). The multiplicity of PRF preparation protocols and clinical uses, such as barrier membrane for dental socket, filling buffer or gel for association with bone graft fragments (sticky bone) contributes to the heterogeneous results reported in the literature regarding the regeneration of soft and hard tissue in isolated form or associated with biomaterials (Castro- Silva, 2018).
The aim of this study was to report a clinical case of oral rehabilitation of the anterior maxillary region by the use of guided bone regeneration, by the association of mixed bone graft and autologous membrane, combined with implantodontic and prosthetic therapy.

Methodology
The study followed a clinical case report typology. According to Pereira, Shitsuka, Parreira and Shitsika (2018), a case report consists of a description and analysis, as detailed as possible, of a condition that presents some particularity that makes it special and contributes to scientific knowledge. It is an empirical investigation of a contemporary phenomenon within its real-life context, with a tendency to try to clarify decisions; why they were taken, how they were implemented and what were the results (Yin, 2015). This case report was carried out in accordance with the international requirements of the CARE guide for clinical reporting (Riley et al., 2017).
There was obedience to the bioethical principles of non-maleficence, beneficence, autonomy, justice and equity

Case Report
Female patient, 45 years old, normosystemic, reported an aesthetic complaint in the anterior maxillary region. Upon clinical and radiographic examination, a single implant-supported dental prosthesis was diagnosed in the region of tooth #11 with aesthetic and functional inadequacy, unfavorable dimensions and position with regard to mobility, as well as altered limits of the gingival mucosa. In tooth #22, gingival inflammation, suppuration and periapical bone resorption were verified, Research, Society andDevelopment, v. 10, n. 11, e112101119456, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i11.19456 4 resulting from a trace of root fracture of the tooth already endodontically treated and with indirect coronary restoration supported by an intraradicular retainer. The proposed surgical treatment under local anesthesia consisted of removing the implant and the tooth #22, with immediate GBR using a mixed graft (sticky bone) composed of Bio-Oss® and leukocyte-and platelet-rich fibrin (L-PRF) and L-PRF membranes, being the autologous blood compounds collected by venipuncture in liquid form in the dental office. (Figure 1). Source: Authors (2021).
The L-PRF membranes were obtained after the centrifugation process for 10 minutes at 1500 rpm while the liquid fibrin was obtained after 3 minutes at 2700 rpm (Ponte, 2020).
The immediate postoperative period of 1 week showed no significant morbidity, without any areas of contamination, unusual inflammation, wound dehiscence or loss of graft material. After 7 months, the alveolar ridge maintained its dimensional stability in the grafted regions. In the second surgical approach, 2 implants were placed together with another GBR of mixed graft or sticky bone, as in the first surgical approach (Figure 2). Six months after the implants, healing caps were placed for tissue conditioning, which remained for 20 days until the complementary dental preparation of tooth #21 and #12, endodontically treated in parallel to the proposed GBR, to allow for the adaptation of the provisional unitary dentures. There was a good gain in thickness, limit and contour of the gingival mucosa, as well as improvement in bone dimensions in terms of height and thickness, and the case continues to be monitored until the final prosthesis is completed. (Figure 3).

Discussion
Although autogenous grafts are still considered the gold standard for bone regeneration, Bio-Oss® represents the second option for vertical bone augmentation in Dentistry, due to its promising clinical results with minimal risk of infection or immune response and slower resorption of than alloplastic ceramics such as beta-tricalcium phosphate, giving greater predictability to bone remodeling and implant placement and lesser postoperative morbidity (Shamsoddin, Houshmand & Golabgiran, 2019).
Bio-Oss® xenograft provides good surgical bed filling, biocompatibility and osteoconduction, while reducing operative time and surgical morbidity (Hass Junior et al., 2016). Meloni et al. (2018) demonstrated that the use of Bio-Oss® can be quite versatile, being able to be combined with other filling materials, such as particulate autologous bone and covered by a resorbable collagen membrane for GBR in horizontal bone defects. Canellas et al. (2021) conducted a systematic review and network meta-analysis to compare different grafts used in the preservation of the dental socket in height and width after extraction and observed in 31 clinical studies distributed worldwide that there was less variation in results with the use of Bio-Oss® or Bio-Oss Collagen® than with other therapeutic modalities including PRF, reinforcing that the aforementioned xenografts would be more predictable bone substitute biomaterials for this application.
Despite stimulating cell proliferation, differentiation, mineralization and gene expression related to osteogenesis, L-PRF alone may be limited to the maintenance of the alveolar ridge during GBR, according to preclinical studies and short-term randomized clinical trials to date (Liu et al., 2019;Ponte et al., 2019). The addition of mineralized and rigid materials, such as Bio-Oss®, could favor the osteoconductive effect in a balanced way with the rate of resorption of the filling material (Castro- Silva, 2018). Csönge, Bozsik, Tóth-Bagi, Gyuris and Kónya (2021) discussed the issue of multiplicity of preparations and an optimal graft-PRF ratio, which could contribute to heterogeneous results, testing the use of sticky bone by associating lyophilized human cortical bone matrix with L-PRF and suggesting a proportion of 0.125g/1ml of plasma (or 1g/8ml) due to its greater strength or binding capacity.
L-PRF therapy could be negatively affected by the patient's systemic conditions, including: older age, pre-existing conditions (such as thrombocytopenia, hemorrhagic disease, and diabetes), nutritional deficiency, environmental or ethnic differences, autoimmunity, and genetic susceptibility (Liu et al., 2019). A Brazilian study found that, in healthy young adult patients between 20 and 40 years old who underwent different forms of GBR after maxillary premolar extraction and before the dental implants, the use of L-PRF without or with association with Boneceramic®, an alloplastic graft compound by hydroxyapatite and beta-TCP, exhibited greater bone gain than biphasic ceramic alone through histomorphometric analysis, exceeding expectations in the GBR purpose (Ponte, 2020). The growing clinical evidence with L-PRF may indicate the gradual technical-scientific evolution of biomaterials for GBR in Dentistry (Castro- . In fresh dental sockets, Mattos et al. (2016) grafted hydroxyapatite with collagen and L-PRF membrane in the region of tooth #24 with buccal bone wall presenting dehiscence and installed a dental implant, promoting satisfactory osseointegration and rehabilitation in the aesthetic area in 18 months. Silva et al. (2020) after remotion of the teeth #21, #22 and #23 used i-PRF to bind synthetic hydroxyapatite and covered the sticky bone with L-PRF membrane, generating an excellent postoperative period and after 6 months, satisfactory bone thickness for implants. Huang, Tan and Kuang (2020) investigated the effect of Bio-Oss® granules with or without PRF in 106 patients with anterior unit tooth loss and alveolar defects and observed that, 12 months after implants and simultaneous GBR, in the group with PRF the thickness of the buccal bone wall and around of implants was higher, the rates of gingival bleeding, probing depth and attachment loss were lower, and the height of bone graft and osteogenesis were greater than xenograft alone.
The use of GBR in two approaches to severe bone loss is reported, as noted by Massuda et al. (2020) who treated severe maxillary resorption in esthetic area between teeth #12 and #22 with homologous block corticomedullary graft and after 7 months installed implants together with a complementary graft of inorganic bovine bone associated with liquid-phase L-PRF and L-PRF membrane, obtaining good final results with the stabilization of a metal-ceramic fixed prosthesis. Interestingly, the protocol used for two GBR using a sticky bone and L-PRF membrane is still unexplored in the literature, which makes this clinical case unprecedented.
According to Ponte et al. (2019), the L-PRF barrier membrane could represent an unmanufactured and customized dental office alternative for osteopromotion in GBR. In the current Brazilian market, commercial osteopromoting membranes have imported origin and natural origin, with bovine collagen more prevalent than porcine, equine and synthetic sources (titanium, polytetrafluoroethylene, alumina, polypropylene and polylactic and polyglycolic acid), with great heterogeneity of formats and rates of resorption, from 4 to 63 weeks . Thus, biocompatibility, bioreabsorption and bioactivity of the PRF membrane are favorable in the interaction with the biological environment , such as GBR collagen membranes, not negatively affecting tissue healing or generating waste products (Quesada, Brenner & Feltraco, 2011).
In addition to the good aesthetic-functional relationship of single implants in the anterior region of the maxilla, for a clinical case to be successful, it must also provide good comfort and hygiene conditions (Souza et al., 2015). The patient's satisfaction with appearance and chewing can, finally, affirm that the proposed surgical-prosthetic treatment was effective and successful, as observed by other authors in the use of L-PRF during GBR (Ponte, 2020;Moraes Júnior & Carvalho, 2020;Mattos et al., 2016). Regarding the efficiency of the technique, the total treatment time with GBR using sticky bone, L-PRF membrane and implants, from surgery to the prosthetic phase, converges with that found in the literature, with an average duration of one and a half years in the region maxillary anterior (Massuda et al., 2020;Moraes Júnior & Carvalho, 2020).

Conclusion
This case report suggests that sticky bone and L-PRF membrane synergistically contributes to multiple GBR in the anterior maxillary region, both in fresh dental socket and in implantodontic retreatment, favoring bone gain and osseointegration.
Possible limitations of this study are the limited follow-up of the patient, who continues her routine dental monitoring, and the absence of other serial cases. However, the positive results achieved encourage the achievement of similar surgical protocols with sticky bone and L-PRF membrane for GBR in the anterior maxilla region.