The use of bioactive factors to enhance bone regeneration: A narrative review

Pioneering nanomedicine in orthopedic treatment care: a review of current research and practices

A developing use of nanotechnology in medicine involves using nanoparticles to administer drugs, genes, biologicals, or other materials to targeted cell types, such as cancer cells. In healthcare, nanotechnology has brought about revolutionary changes in the treatment of various medical and surgical conditions, including in orthopedic. Its clinical applications in surgery range from developing surgical instruments and suture materials to enhancing imaging techniques, targeted drug delivery, visualization methods, and wound healing procedures. Notably, nanotechnology plays a significant role in preventing, diagnosing, and treating orthopedic disorders, which is crucial for patients' functional rehabilitation. The integration of nanotechnology improves standards of patient care, fuels research endeavors, facilitates clinical trials, and eventually improves the patient's quality of life. Looking ahead, nanotechnology holds promise for achieving sustained success in numerous surgical disciplines, including orthopedic surgery, in the years to come. This review aims to focus on the application of nanotechnology in orthopedic surgery, highlighting the recent development and future perspective to bridge the bridge for clinical translation.

APCs in sinus floor augmentation

After tooth loss in the posterior area of the maxilla, sinus floor elevation is often required to compensate the vertical bone loss due to sinus pneumatization. This narrative review reports on the potential benefits of autologous platelet concentrates (APCs) during this procedure. As for transcrestal approach, APCs have been used as "sole" substitute/graft. However, because of the low number of clinical trials available with PRGF, and even none for PRP, no definitive conclusions can be made regarding their efficacy. The number of studies on the use of L-PRF were outnumbered indicating good feasibility for vertical bone gain, with a high implant survival rate and a low degree of complications. PRP and PRGF have not been studied as a "single/sole" substitute for a one-stage lateral window approach, probably because of the weak physical characteristics of the membranes. L-PRF alone appears to be a predictable grafting material for lateral maxillary sinus grafting and a reduced RBH should not be considered as a risk factor. Compared to a "standard" bone substitute L-PRF shows slightly less vertical bone gain (consider enough membrane application and use of bony window as new sinus floor roof over the implant apices), enhanced early resorption (first 6 months after application), but a similar stable bone gain afterward. For a two-stage lateral window approach, APCs "alone" cannot be recommended, due to their weak withstand to the sinus pneumatization forces. APCs combined with bone substitutes seem to accelerate bone formation, without any additional benefits on the long-term new bone gain. The use of L-PRF membranes for the treatment of perforations appears to be an effective treatment option, but further clinical studies are needed to confirm this. Even though the abovementioned statements are based on large numbers of studies, additional RCTs comparing APCs with different types of grafting procedures for sinus elevation are needed.

The use of mesenchymal stromal cell secretome to enhance guided bone regeneration in comparison with leukocyte and platelet-rich fibrin

OBJECTIVES

Secretomes of mesenchymal stromal cells (MSC) represent a novel strategy for growth-factor delivery for tissue regeneration. The objective of this study was to compare the efficacy of adjunctive use of conditioned media of bone-marrow MSC (MSC-CM) with collagen barrier membranes vs. adjunctive use of conditioned media of leukocyte- and platelet-rich fibrin (PRF-CM), a current growth-factor therapy, for guided bone regeneration (GBR).

METHODS

MSC-CM and PRF-CM prepared from healthy human donors were subjected to proteomic analysis using mass spectrometry and multiplex immunoassay. Collagen membranes functionalized with MSC-CM or PRF-CM were applied on critical-size rat calvaria defects and new bone formation was assessed via three-dimensional (3D) micro-CT analysis of total defect volume (2 and 4 weeks) and 2D histomorphometric analysis of central defect regions (4 weeks).

RESULTS

While both MSC-CM and PRF-CM revealed several bone-related proteins, differentially expressed proteins, especially extracellular matrix components, were increased in MSC-CM. In rat calvaria defects, micro-CT revealed greater total bone coverage in the MSC-CM group after 2 and 4 weeks. Histologically, both groups showed a combination of regular new bone and 'hybrid' new bone, which was formed within the membrane compartment and characterized by incorporation of mineralized collagen fibers. Histomorphometry in central defect sections revealed greater hybrid bone area in the MSC-CM group, while the total new bone area was similar between groups.

CONCLUSION

Based on the in vitro and in vivo investigations herein, functionalization of membranes with MSC-CM represents a promising strategy to enhance GBR.

Bioactive Scaffolds as a Promising Alternative for Enhancing Critical-Size Bone Defect Regeneration in the Craniomaxillofacial Region

Reconstruction of critical-size bone defects (CSDs) in the craniomaxillofacial (CMF) region remains challenging. Scaffold-based bone-engineered constructs have been proposed as an alternative to the classical treatments made with autografts and allografts. Scaffolds, a key component of engineered constructs, have been traditionally viewed as biologically passive temporary replacements of deficient bone lacking intrinsic cues to promote osteogenesis. Nowadays, scaffolds are functionalized, giving rise to bioactive scaffolds promoting bone regeneration more effectively than conventional counterparts. This review focuses on the three approaches most used to bioactivate scaffolds: (1) conferring microarchitectural designs or surface nanotopography; (2) loading bioactive molecules; and (3) seeding stem cells on scaffolds, providing relevant examples of in vivo (preclinical and clinical) studies where these methods are employed to enhance CSDs healing in the CMF region. From these, adding bioactive molecules (specifically bone morphogenetic proteins or BMPs) to scaffolds has been the most explored to bioactivate scaffolds. Nevertheless, the downsides of grafting BMP-loaded scaffolds in patients have limited its successful translation into clinics. Despite these drawbacks, scaffolds containing safer, cheaper, and more effective bioactive molecules, combined with stem cells and topographical cues, remain a promising alternative for clinical use to treat CSDs in the CMF complex replacing autografts and allografts.

Alveolar ridge reconstruction with a digitally customized bone block allograft

BACKGROUND

Reduced alveolar ridge volume is an often consequence after tooth loss, compromising implant placement and prosthetic rehabilitation. The digital customization of bone block allografts (BBA) is an alternative that incorporates advantages such as intimate contact with the recipient bed, increasing graft stability and reduced surgical time. In addition, enamel matrix derivate (EMD) has attracted interest for its effect on osteogenic gene expression and cell adhesion; few studies have focused on the benefits of bone regeneration with EMD. The aim of this case report is to present the reconstruction of a severely atrophic alveolar ridge defect with a digitally customized bone block allograft (CBBA) in combination with EMD as an adjuvant for bone regeneration and soft tissue healing.

METHODS

Initially, the digital planning and manufacture of the BBA was performed based on an initial cone beam computed tomography (CBCT) scan. EMD was applied to the recipient site and to the CBBA before graft fixation. After 6 months, bone biopsies were obtained on re-entry surgery for prosthetically guided implant placement.

RESULTS

Clinically, bone block showed good integration with the adjacent tissue and no signs of rejection or necrosis were found. On the histological evaluation, new bone was observed in intimate contact with the allograft and showed viable osteocytes and osteoblasts along its entire length. Residual allograft particles were observed to be highly osteoconductive.

CONCLUSION

According to the clinical and histological results presented, the digital customization of the BBA allows an ideal graft fit to the recipient bed with excellent results in bone regeneration.

Regeneration of injured articular cartilage using the recombinant human amelogenin protein

Aims

Cartilage injuries rarely heal spontaneously and often require surgical intervention, leading to the formation of biomechanically inferior fibrous tissue. This study aimed to evaluate the possible effect of amelogenin on the healing process of a large osteochondral injury (OCI) in a rat model.

Methods

A reproducible large OCI was created in the right leg femoral trochlea of 93 rats. The OCIs were treated with 0.1, 0.5, 1.0, 2.5, or 5.0 μg/μl recombinant human amelogenin protein (rHAM+) dissolved in propylene glycol alginate (PGA) carrier, or with PGA carrier alone. The degree of healing was evaluated 12 weeks after treatment by morphometric analysis and histological evaluation. Cell recruitment to the site of injury as well as the origin of the migrating cells were assessed four days after treatment with 0.5 μg/μl rHAM+ using immunohistochemistry and immunofluorescence.

Results

A total of 12 weeks after treatment, 0.5 μg/μl rHAM+ brought about significant repair of the subchondral bone and cartilage. Increased expression of proteoglycan and type II collagen and decreased expression of type I collagen were revealed at the surface of the defect, and an elevated level of type X collagen at the newly developed tide mark region. Conversely, the control group showed osteoarthritic alterations. Recruitment of cells expressing the mesenchymal stem cell (MSC) markers CD105 and STRO-1, from adjacent bone marrow toward the OCI, was noted four days after treatment.

Conclusion

We found that 0.5 μg/μl rHAM+ induced in vivo healing of injured articular cartilage and subchondral bone in a rat model, preventing the destructive post-traumatic osteoarthritic changes seen in control OCIs, through paracrine recruitment of cells a few days after treatment.

Simultaneous or staged lateral ridge augmentation: A clinical guideline on the decision-making process

Lateral ridge augmentation is a standard surgical procedure that can be performed prior to (staged) or simultaneously with implant placement. The decision between a simultaneous or staged approach involves considering multiple variables. This paper proposed a decision-making process that serves as a guideline for choosing the best treatment choice based on the available evidence and the author's clinical experience.

Efficacy of biomaterials for lateral bone augmentation performed with guided bone regeneration. A network meta-analysis

Bone regeneration is often required concomitant with implant placement to treat a bone fenestration, a dehiscence, and for contouring. This systematic review assessed the impact of different biomaterials employed for guided bone regeneration (GBR) simultaneous to implant placement on the stability of radiographic peri-implant bone levels at ≥12 months of follow-up (focused question 1), as well as on bone defect dimension (width/height) changes at re-assessment after ≥4 months (focused question 2). Only randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that compared different biomaterials for GBR were considered. A Bayesian network meta-analysis (NMA) was performed using a random-effects model. A ranking probability between treatments was obtained, as well as an estimation of the surface under the cumulative ranking value (SUCRA). Overall, whenever the biological principle of GBR was followed, regeneration occurred in a predictable way, irrespective of the type of biomaterial used. A lower efficacy of GBR treatments was suggested for initially large defects, despite the trend did not reach statistical significance. Regardless of the biomaterial employed, a certain resorption of the augmented bone was observed overtime. While GBR was shown to be a safe and predictable treatment, several complications (including exposure, infection, and soft tissue dehiscence) were reported, which tend to be higher when using cross-linked collagen membranes.

Clinical and radiographic assessment of cross-linked hyaluronic acid addition in demineralized bovine bone based alveolar ridge preservation: A human randomized split-mouth pilot study

PURPOSE

To investigate clinically and radiographically at 4 months post-operatively the outcomes of mixing demineralized bovine bone material (DBBM) with cross-linked hyaluronic acid in alveolar ridge preservation.

MATERIAL AND METHODS

Seven patients presenting bilateral hopeless teeth (14 teeth) were enrolled in the study, the test site contained demineralized bovine bone material (DBBM) mixed with cross-linked hyaluronic acid (xHyA) while the control site contained only DBBM. 4 months post-operatively prior to implant placement a Cone beam computed tomography (CBCT) scan was recorded and compared to the initial scan to assess the volumetric and linear bone resorption that occurred in both sites. Clinically, sites that needed further bone grafting at the implant placement stage were recorded. Differences in volumetric and linear bone resorption between both groups were assessed using Wilcoxon signed rank test. McNemar test was also used to evaluate difference in bone grafting need between both groups.

RESULTS

All sites healed uneventfully, volumetric and linear resorption differences between the baseline and 4 months post-operatively were obtained for each site. The mean volumetric and linear bone resorption were respectively 36.56 ± 1.69%, 1.42 ± 0.16 mm in the controls sites and 26.96 ± 1.83%; 0.73 ± 0.052 mm in the tests sites. The values were significantly higher among controls sites (P=0.018). No significant differences were observed in the need for bone grafting between both groups.

CONCLUSION

Cross-linked hyaluronic acid (xHyA) appears to limit the post-extractional alveolar bone resorption when mixed with DBBM.

Proteomic Analysis of Mesenchymal Stromal Cells Secretome in Comparison to Leukocyte- and Platelet-Rich Fibrin

Secretomes of mesenchymal stromal cells (MSCs) are emerging as a novel growth factor (GF)-based strategy for periodontal and bone regeneration. The objective of this study was to compare the secretome of human bone marrow MSC (BMSC) to that of leukocyte- and platelet-rich fibrin (L-PRF), an established GF-based therapy, in the context of wound healing and regeneration. Conditioned media from human BMSCs (BMSC-CM) and L-PRF (LPRF-CM) were subjected to quantitative proteomic analysis using liquid chromatography with tandem mass spectrometry. Global profiles, gene ontology (GO) categories, differentially expressed proteins (DEPs), and gene set enrichment (GSEA) were identified using bioinformatic methods. Concentrations of selected proteins were determined using a multiplex immunoassay. Among the proteins identified in BMSC-CM (2157 proteins) and LPRF-CM (1420 proteins), 1283 proteins were common. GO analysis revealed similarities between the groups in terms of biological processes (cellular organization, protein metabolism) and molecular functions (cellular/protein-binding). Notably, more DEPs were identified in BMSC-CM (n = 550) compared to LPRF-CM (n = 118); these included several key GF, cytokines, and extracellular matrix (ECM) proteins involved in wound healing. GSEA revealed enrichment of ECM (especially bone ECM)-related processes in BMSC-CM and immune-related processes in LPRF-CM. Similar trends for intergroup differences in protein detection were observed in the multiplex analysis. Thus, the secretome of BMSC is enriched for proteins/processes relevant for periodontal and bone regeneration. The in vivo efficacy of this therapy should be evaluated in future studies.

Allogenic Stem Cells Carried by Porous Silicon Scaffolds for Active Bone Regeneration In Vivo

To date, bone regeneration techniques use many biomaterials for bone grafting with limited efficiencies. For this purpose, tissue engineering combining biomaterials and stem cells is an important avenue of development to improve bone regeneration. Among potentially usable non-toxic and bioresorbable scaffolds, porous silicon (pSi) is an interesting biomaterial for bone engineering. The possibility of modifying its surface can allow a better cellular adhesion as well as a control of its rate of resorption. Moreover, release of silicic acid upon resorption of its nanostructure has been previously proved to enhance stem cell osteodifferentiation by inducing calcium phosphate formation. In the present study, we used a rat tail model to experiment bone tissue engineering with a critical size defect. Two groups with five rats per group of male Wistar rats were used. In each rat, four vertebrae were used for biomaterial implantation. Randomized bone defects were filled with pSi particles alone or pSi particles carrying dental pulp stem cells (DPSC). Regeneration was evaluated in comparison to empty defect and defects filled with xenogenic bone substitute (Bio-Oss^®). Fluorescence microscopy and SEM evaluations showed adhesion of DPSCs on pSi particles with cells exhibiting distribution throughout the biomaterial. Histological analyzes revealed the formation of a collagen network when the defects were filled with pSi, unlike the positive control using Bio-Oss^®. Overall bone formation was objectivated with µCT analysis and showed a higher bone mineral density with pSi particles combining DPSC. Immunohistochemical assays confirmed the increased expression of bone markers (osteocalcin) when pSi particles carried DPSC. Surprisingly, no grafted cells remained in the regenerated area after one month of healing, even though the grafting of DPSC clearly increased bone regeneration for both bone marker expression and overall bone formation objectivated with µCT. In conclusion, our results show that the association of pSi with DPSCs in vivo leads to greater bone formation, compared to a pSi graft without DPSCs. Our results highlight the paracrine role of grafted stem cells by recruitment and stimulation of endogenous cells.

Complications and treatment errors in peri-implant hard tissue management

Bone augmentation procedures aim to regenerate the deficient alveolar ridge to properly place dental implants that are completely surrounded by bone. However, these are invasive and technically demanding surgeries that are not free of either complications or treatment errors. Careful patient selection and preparation is a mandatory process to reduce the rate of complications in bone regeneration procedures, irrespective of the technique used. It is important to assess the cost benefit of the intervention and to evaluate the potential impact on the patient's quality of life, especially in the elderly and medically compromised patients. Most common postoperative complications are wound dehiscences, which may be reduced, at least partially, by proper knowledge of the surgical technique and the craniofacial anatomy. Other complications that may appear are postoperative infections or nerve injuries. The aim of this narrative review is to summarize the best available scientific evidence on the incidence of complications, as well as the ideal strategies for their prevention and management. Depending on the severity of the complication, treatment approaches may vary and can include drug prescription or even surgical re-entries to remove exposed barrier membranes or contaminated bone grafts. Adequate prevention and proper management of complications associated with bone augmentation interventions are a requirement for clinicians carrying out these demanding procedures. A series of cases illustrating proper management of complications in different clinical scenarios is presented.

Clinical and patient-reported outcomes of tissue engineering strategies for periodontal and peri-implant reconstruction

Scientific advancements in biomaterials, cellular therapies, and growth factors have brought new therapeutic options for periodontal and peri-implant reconstructive procedures. These tissue engineering strategies involve the enrichment of scaffolds with living cells or signaling molecules and aim at mimicking the cascades of wound healing events and the clinical outcomes of conventional autogenous grafts, without the need for donor tissue. Several tissue engineering strategies have been explored over the years for a variety of clinical scenarios, including periodontal regeneration, treatment of gingival recessions/mucogingival conditions, alveolar ridge preservation, bone augmentation procedures, sinus floor elevation, and peri-implant bone regeneration therapies. The goal of this article was to review the tissue engineering strategies that have been performed for periodontal and peri-implant reconstruction and implant site development, and to evaluate their safety, invasiveness, efficacy, and patient-reported outcomes. A detailed systematic search was conducted to identify eligible randomized controlled trials reporting the outcomes of tissue engineering strategies utilized for the aforementioned indications. A total of 128 trials were ultimately included in this review for a detailed qualitative analysis. Commonly performed tissue engineering strategies involved scaffolds enriched with mesenchymal or somatic cells (cell-based tissue engineering strategies), or more often scaffolds loaded with signaling molecules/growth factors (signaling molecule-based tissue engineering strategies). These approaches were found to be safe when utilized for periodontal and peri-implant reconstruction therapies and implant site development. Tissue engineering strategies demonstrated either similar or superior clinical outcomes than conventional approaches for the treatment of infrabony and furcation defects, alveolar ridge preservation, and sinus floor augmentation. Tissue engineering strategies can promote higher root coverage, keratinized tissue width, and gingival thickness gain than scaffolds alone can, and they can often obtain similar mean root coverage compared with autogenous grafts. There is some evidence suggesting that tissue engineering strategies can have a positive effect on patient morbidity, their preference, esthetics, and quality of life when utilized for the treatment of mucogingival deformities. Similarly, tissue engineering strategies can reduce the invasiveness and complications of autogenous graft-based staged bone augmentation. More studies incorporating patient-reported outcomes are needed to understand the cost-benefits of tissue engineering strategies compared with traditional treatments.

The efficacy of bone reconstructive therapies in the management of peri-implantitis. A systematic review and meta-analysis

AIM

To evaluate the efficacy of bone reconstructive procedures for the reduction of probing pocket depth (PPD), bleeding on probing (BOP), and suppuration in peri-implantitis-related bone defects at ≥12-month follow-up.

MATERIALS AND METHODS

Three databases were searched for randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that compared bone reconstructive therapies to access flap surgery (AFS) (Focused Question-FQ 1), and RCTs, CCTs, and prospective case series that assessed the efficacy of reconstructive therapies (FQ 2). Meta-analysis was performed for FQ1 when more than three studies were identified, while for FQ2 a network was drawn based on RCTs with common treatment arms.

RESULTS

Seven RCTs were identified for FQ1 while five RCTs and six prospective case series for FQ2. There was no significant difference in PPD change between AFS and reconstructive surgery (-0.387; p = .325) at 12 months. Furthermore, no clear differences in terms of PPD and BOP changes resulted from the different reconstructive therapies included in the network. Only a small percentage of treated cases with any modality achieved peri-implantitis resolution, as defined by different composite outcomes.

CONCLUSIONS

Reconstructive surgery does not offer significant improvements in peri-implant clinical parameters as compared to AFS at 12 months. It was not possible to establish a hierarchy of efficacy among the different biomaterials employed for reconstructive surgery.

Bench-to-bedside: Feasibility of nano-engineered and drug-delivery biomaterials for bone-anchored implants and periodontal applications

Nanotechnology and drug-release biomaterials have been thoroughly explored in the last few years aiming to develop specialized clinical treatments. However, it is rare to find biomaterials associated with drug delivery properties in the current dental market for application in oral bone- and periodontal-related procedures. The gap between basic scientific evidence and translation to a commercial product remains wide. Several challenges have been reported regarding the clinical translation of biomaterials with drug-delivery systems (BDDS) and nanofeatures. Therefore, processes for BDDS development, application in preclinical models, drug delivery doses, sterilization processes, storage protocols and approval requirements were explored in this review, associated with tentative solutions for these issues. The diversity of techniques and compounds/molecules applied to develop BDDS demands a case-by-case approach to manufacturing and validating a commercial biomaterial. Promising outcomes such as accelerated tissue healing and higher antibacterial response have been shown through basic and preclinical studies using BDDS and nano-engineered biomaterials; however, the adequate process for sterilization, storage, cost-effectiveness and possible cytotoxic effects remains unclear for multifunctional biomaterials incorporated with different chemical compounds; then BDDSs are rarely translated into products. The future benefits of BDDS and nano-engineered biomaterials have been reported suggesting personalized clinical treatment and a promising reduction in the use of systemic antibiotics. Finally, the launch of these specialized biomaterials with solid data and controlled traceability onto the market will generate strong specificity for healthcare treatments.

Testosterone Enanthate: An In Vitro Study of the Effects Triggered in MG-63 Cells

The aim of this study was to investigate the effects of the androgenic hormone testosterone enanthate (TE) on human MG-63 cells. MG-63 were cultured for 24 h in the presence of TE at increasing concentrations to assess its lethal dose. Therefore, the suitable concentration for a prolonged use of TE in vitro was assessed by viability assay over 9 days. Finally, MG-63 were exposed to TE for 14 days and assayed for differentiation by qPCR and Alizarin Red S staining. TE in the amount of 100 µM resulted as the maximum dose tolerated by MG-63 cells after 24 h. However, a prolonged exposure in culture TE in the amount of 100 µM showed a cytostatic effect on cell proliferation. On the contrary, TE 10 µM was tolerated by the cells and did not boost cell proliferation, but did enhance new bone formation, as revealed by COL1A1, ALPL, BGLAP, and IBSP gene expression after 3, 7, and 14 days, and calcium deposition by Alizarin Red S staining after 14 days. Based on the current study, 10 µM is the critical dose of TE that should be used in vitro to support bone differentiation of MG-63 cells.

Novel nanocomposite scaffold based on gelatin/PLGA-PEG-PLGA hydrogels embedded with TGF-β1 for chondrogenic differentiation of human dental pulp stem cells in vitro

In the current study, a novel nanocomposite hydrogel scaffold comprising of natural-based gelatin and synthetic-based (poly D, L (lactide-co-glycolide) -b- poly (ethylene glycol)-b- poly D, L (lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymer was developed and loaded with transforming growth factor- β1 (TGF-β1). Synthesized scaffolds' chemical structure was examined by ¹H NMR and ATR-FTIR. Scanning electron microscopy (SEM) confirmed particle size and morphology of the prepared nanoparticles as well as the scaffolds. The morphology analysis revealed a porous interconnected structure throughout the scaffold with a pore size dimension of about 202.05 µm. The swelling behavior, in vitro degradation, mechanical properties, density, and porosity were also evaluated. Phalloidin/DAPI staining was utilized for confirming the extended cytoskeleton of the chondrocytes. Alcian blue staining was conducted to determine cartilaginous matrix sulfated glycosaminoglycan (sGAG) synthesis. Eventually, over a period of 21 days, a real-time RT-PCR analysis was applied to measure the mRNA expression of chondrogenic marker genes, type-II collagen, SOX 9, and aggrecan, in hDPSCs cultured for up to 21 days to study the influence of gelatin/PLGA-PEG-PLGA-TGF-β1 hydrogels on hDPSCs. The findings of the cell-encapsulating hydrogels analysis suggested that the adhesion, viability, and chondrogenic differentiation of hDPSCs improved by gelatin/PLGA-PEG-PLGA-TGF-β1 nanocomposite hydrogels. These data supported the conclusion that gelatin/PLGA-PEG-PLGA-TGF-β1 nanocomposite hydrogels render the features that allow thein vitrofunctionality of encapsulated hDPSCs and hence can contribute the basis for new effective strategies for the treatment of cartilage injuries.

Recombinant factors for periodontal intrabony defects: A systematic review and network meta-analysis of preclinical studies

The use of bioactive agents combined with osteoconductive scaffolds for the regeneration of periodontal intrabony defects has been the subject of intensive research in the past 20 years. Most studies reported that such agents, used in different concentrations, doses and combined with various scaffolds, might promote periodontal tissue regeneration, but evidence for the most effective combination of such agents is lacking. The objective of this study 13 was to rank the different combinations of recombinant human-derived growth and differentiation factors with/without scaffold biomaterial in the treatment of periodontal intrabony defects, through network meta-analysis of pre-clinical studies. The systematic review and network meta-analysis protocol was registered on the PROSPERO Systematic Review database with reference number: CRD42021213673. Relevant published articles were obtained after searching five electronic databases. A specific search strategy was followed by using keywords related to intrabony defects, regenerative materials, scaffolds and recombinant factors, and animal studies. All pre-clinical studies used for periodontal regeneration were included. The primary outcomes were: regeneration of junctional epithelium (mm), new cementum, connective tissue attachment, percentage of new bone formation (%), bone area (mm² ), bone volume density (g/cm³ ) and bone height (mm) data was extracted. The analysis was carried out using network meta-analysis methods, that is illustrating network plots, contribution plots, predictive and confidence interval plot, surface under the cumulative ranking (SUCRA), multidimensional scale ranking and net funnel plots using STATA IC statistical software. An SYRCLE's tool for assessing risk of bias was used for reporting risk of bias among individual studies. A total of N = 24 for qualitative and N = 21 studies for quantitative analysis published till 2020 were included. The cumulative total number of animals included in the control and test groups were N = 162 and N = 339, respectively. The duration of the study was between 3 and 102 weeks rhBMP-2 ranked higher in SUCRA as the agent associated with the best performance for bone volume density. rhGDF-5/TCP ranked best in the bone area (mm2), rhPDGF-BB/Equine ranked best in bone height (mm), rhBMP-2 ranked best in the percentage of new bone fill, rhBMP-2/ACS ranked best in new cementum formation, and rhGDF-5/b- TCP/PLGA ranked best in connective tissue attachment and junctional epithelium. There were no adverse effects identified in the literature that could affect the different outcomes for regeneration in intrabony defects. Various recombinant factors are effective in promoting the regeneration of both soft and hard tissue supporting structures of the periodontium. However, when considering different outcomes, different agents, associated or not with biomaterials, ranked best. Keeping into account the limited transferability of results from animal studies to the clinical setting, the choice of the most appropriate formulation of bioactive agents may depend on clinical needs and purpose.

Differences in platelet-rich plasma composition influence bone healing

AIM

Platelet-rich plasma (PRP) is an autologous blood-derived material that has been used to enhance bone regeneration. Clinical studies, however, reported inconsistent outcomes. This study aimed to assess the effect of changes in leucocyte and PRP (L-PRP) composition on bone defect healing.

MATERIALS AND METHODS

L-PRPs were prepared using different centrifugation methods and their regenerative potential was assessed in an in-vivo rat model. Bilateral critical-size tibial bone defects were created and filled with single-spin L-PRP, double-spin L-PRP, or filtered L-PRP. Empty defects and defects treated with collagen scaffolds served as controls. Rats were euthanized after 2 weeks, and their tibias were collected and analysed using micro-CT and histology.

RESULTS

Double-spin L-PRP contained higher concentrations of platelets than single-spin L-PRP and filtered L-PRP. Filtration of single-spin L-PRP resulted in lower concentrations of minerals and metabolites. In vivo, double-spin L-PRP improved bone healing by significantly reducing the size of bone defects (1.08 ± 0.2 mm³ ) compared to single-spin L-PRP (1.42 ± 0.27 mm³ ) or filtered L-PRP (1.38 ± 0.28 mm³ ). There were fewer mast cells, lymphocytes, and macrophages in defects treated with double-spin L-PRP than in those treated with single-spin or filtered L-PRP.

CONCLUSION

The preparation method of L-PRP affects their composition and potential to regenerate bone.

The use of rhBMP2 for augmentation of established horizontal/vertical defects may require additional use of rhVEGF to achieve significant bone regeneration: An in vivo experimental study

AIM

To test the hypothesis that the use of rhBMP2 in established defects requires additional growth factors such as rhVEGF to accomplish effective bone repair.

MATERIALS AND METHODS

Horizontal/vertical defects of 2 cm length and 1 cm height were created bilaterally in the alveolar crest of the maxillae of 18 minipigs together with the extraction of all premolar teeth and one molar tooth on both sides. After 3 months of healing, defects were augmented with 0.5 g particulate PDLLA/CaCO3 composite loaded with 400 µg rhBMP2/50 µg rhVEGF165 on one side and 800 µg rhBMP2 on the other in 12 test animals, whereas defects in six control animals were sham operated and left unfilled on one side and augmented with blank carriers on the other. After 4 and 13 weeks, the animals were evaluated each for area of new bone formation (mm²) and bone density (area %).

RESULTS

Augmentations with carriers loaded with 800 g µrhBMP2 failed to induce significantly more bone than in the augmentations with unloaded carrier after 4 and 13 weeks (p = .1000, p = .381). Augmentations with carriers loaded with 400 µg rhBMP2 and 50 µg erhVEGF165 resulted in significantly increased bone formation after 13 weeks (p = .024) compared to blank carriers. Soft tissue in augmentations with combined rhBMP2/rhVEGF165 loading exhibited numerous microvessels compared to soft tissue in augmentations with rhBMP2.

CONCLUSIONS

It is concluded that effective bone regeneration in augmentations of established alveolar ridge defects may require the application of rhVEGF additionally to rhBMP2.

The Role of Growth Factors in Bioactive Coatings

With increasing obesity and an ageing population, health complications are also on the rise, such as the need to replace a joint with an artificial one. In both humans and animals, the integration of the implant is crucial, and bioactive coatings play an important role in bone tissue engineering. Since bone tissue engineering is about designing an implant that maximally mimics natural bone and is accepted by the tissue, the search for optimal materials and therapeutic agents and their concentrations is increasing. The incorporation of growth factors (GFs) in a bioactive coating represents a novel approach in bone tissue engineering, in which osteoinduction is enhanced in order to create the optimal conditions for the bone healing process, which crucially affects implant fixation. For the application of GFs in coatings and their implementation in clinical practice, factors such as the choice of one or more GFs, their concentration, the coating material, the method of incorporation, and the implant material must be considered to achieve the desired controlled release. Therefore, the avoidance of revision surgery also depends on the success of the design of the most appropriate bioactive coating. This overview considers the integration of the most common GFs that have been investigated in in vitro and in vivo studies, as well as in human clinical trials, with the aim of applying them in bioactive coatings. An overview of the main therapeutic agents that can stimulate cells to express the GFs necessary for bone tissue development is also provided. The main objective is to present the advantages and disadvantages of the GFs that have shown promise for inclusion in bioactive coatings according to the results of numerous studies.

Combination of bone substitutes and vectors in periodontology and implantology: A systematic review

The aim of the systematic review was to analyze the use of combination of bone substitutes and vectors in periodontology and implantology among animals models and humans. Electronic databases were searched, and additional hand search was performed. The research strategy was achieved according to the PRISMA guidelines. The including criteria were: combination of bone substitutes and vectors, in vivo studies, a precise number of specimens, histological and radiographic analysis, written in English. The risk of bias was evaluated for individual studies. Thirty-two articles were selected and investigated in this systematic review. The results do not show a superiority of the use of composite biomaterial in comparison with simple biomaterial but suggest the efficacity of their utilization as a carrier of bioactive agents. Future studies need to identify the suitable association of bone substitutes and vectors and explore interest in their use such as the support of growth factors.

A tissue-engineered biocomplex for periodontal reconstruction. A proof-of-principle randomized clinical study

AIM

To assess the safety/efficacy of a tissue-engineered biocomplex in periodontal reconstruction.

METHODS

Twenty-seven intrabony defects were block-randomized across three treatment groups: Group-A (N_A  = 9) received autologous clinical-grade alveolar bone marrow mesenchymal stem cells (a-BMMSCs), seeded into collagen scaffolds, enriched with autologous fibrin/platelet lysate (aFPL). In Group-B (N_B  = 10), the collagen scaffold/aFPL devoid of a-BMMSCs filled the osseous defect. Group-C (N_C  = 8) received Minimal Access Flap surgery retaining the soft tissue wall of defects identically with Groups-A/-B. Subjects were clinically/radiographically assessed before anaesthesia (baseline) and repeatedly over 12 months.

RESULTS

Quality controls were satisfied before biocomplex transplantation. There were no adverse healing events. All approaches led to significant clinical improvements (p < .001) with no inter-group differences. At 12 months, the estimated marginal means for all groups were as follows: 3.0 (95% CI: 1.9-4.1) mm for attachment gain; 3.7 (2.7-4.8) mm for probing pocket depth reduction; 0.7 (0.2-1.3) mm increase in recession. An overall greater mean reduction in the radiographic Cemento-Enamel Junction to Bottom Defect (CEJ-BD) distance was found for Groups-A/-C over Group-B (p < .023).

CONCLUSION

Radiographic evidence of bone fill was less pronounced in Group-B, although clinical improvements were similar across groups. All approaches aimed to trigger the innate healing potential of tissues. Cell-based therapy is justified for periodontal reconstruction and remains promising in selected cases.

Evaluating the efficacy of recombinant human bone morphogenic protein-2 in the treatment of alveolar clefts with autologous bone grafting using computer-aided engineering techniques

Recent studies have indicated the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) to be a viable adjunctive to alveolar cleft reconstruction owing to its osteoinductive capacity. This study aimed to evaluate the efficacy of rhBMP-2 in the treatment of alveolar cleft with autologous bone grafts by precise volumetric analysis. Twenty-six patients (aged 8-14) with unilateral alveolar clefts were enrolled in this comparative study. Patients were divided into two groups: the iliac crest bone graft (ICBG) was placed at the side of the cleft in the control group (ICBG group), and rhBMP-2 was mixed with the ICBG in the rhBMP-2 group (BMP group). Helical computed tomographic images were obtained preoperatively and 12 months postoperatively. The datasets were reconstructed as three-dimensional (3D) images using Mimics software and processed using Geomagic Wrap. The newly formed bone of the alveolar cleft was segmented by identifying the differences between preoperative and postoperative 3D images. In the ICBG group, the volume of newly formed bone ranged from 0.25 to 0.88 cm³, and the mean (SD) bone formation percentage was 42.01% (15.57%). In the BMP group, the volume of newly formed bone ranged from 0.34 to 1.09 cm³, and the bone formation mean (SD) percentage was 55.79% (11.84%). There was a statistically significant difference between the two groups in terms of the postoperative percentage of bone formation (p = 0.022). Thus, rhBMP-2 combined with an autologous bone graft is a promising technique to improve the results of secondary alveolar bone grafting.

Red and Yellow Injectable Platelet-Rich Fibrin Demonstrated Differential Effects on Periodontal Ligament Stem Cell Proliferation, Migration, and Osteogenic Differentiation

The biological benefits of using two fractions derived from injectable platelet-rich fibrin (i-PRF) in bone regeneration remain unclear. Thus, the current study examined two fractionation protocols producing yellow i-PRF and red i-PRF on periodontal ligament stem cells (PDLSCs). The i-PRF samples from five donors were harvested from two different levels, with and without a buffy coat layer, to obtain red and yellow i-PRF, respectively. The PDLSCs were isolated and characterized before their experimental use. The culture medium in each assay was loaded with 20% of the conditioned medium containing the factors released from the red and yellow i-PRF. Cell proliferation and cell migration were determined with an MTT and trans-well assay, respectively. Osteogenic differentiation was investigated using alkaline phosphatase and Alizarin red staining. The efficiency of both i-PRFs was statistically compared. We found that the factors released from the red i-PRF had a greater effect on cell proliferation and cell migration. Moreover, the factors released from the yellow i-PRF stimulated PDLSC osteogenic differentiation earlier compared with the red i-PRF. These data suggest that the red i-PRF might be suitable for using in bone regeneration because it induced the mobilization and growth of bone regenerative cells without inducing premature mineralization.

Histological comparison of DBBM and platelet rich fibrin for guided bone regeneration in a rabbit model

Purpose

To histologically evaluate the use of bovine derived deproteinized xenograft (DBBM), leukocyte and platelet rich fibrin (L-PRF) and the combination of both in Guided Bone Regeneration (GBR) performed in non-critical size defects in rabbit.

Methods

A prospective experimental study was performed. Four bone defects in the tibiae of 12 rabbits were made and each of them was filled with DBBM, L-PRF, a combination of DBBM + L-PRF or was left to heal as control site. All defects were covered with a collagen membrane. Rabbits were randomly distributed in three groups and euthanatized at 3, 6 or 9 weeks. Samples were obtained and histologically analyzed to determine vital bone, connective tissue and remaining graft particles percentage. Analysis of variance, Kruskal Wallis and non-paired t-test where used to evaluate the significance of the results.

Results

At 3 weeks of healing, DBBM showed significantly more vital bone percentage than L-PRF (p = 0,05) and DBBM + L-PRF showed significantly less connective tissue than control (p < 0,05). All other groups showed no statistical difference between them. At 6 weeks of healing, DBBM showed significantly more vital bone percentage than L-PRF (p < 0,05), DBBM + L-PRF (p < 0,05) and control (p < 0,05) and there wasn't any other significant difference regarding to connective tissue or remaining particle percentage between groups. At t 9 weeks healing period, there weren't any significant differences between groups.

Conclusions

DBBM seems to enhance vital bone formation at early healing stages. The use of L-PRF alone or combined with DBBM, didn't show any histological improvement regarding to vital bone formation. The use of DBBM, alone or in conjunction with L-PRF showed a trend to reduce connective tissue percentage. The use of L-PRF combined with DBBM didn't affect the remaining particle percentage.

Management of the extraction socket and timing of implant placement: Consensus report and clinical recommendations of group 3 of the XV European Workshop in Periodontology

BACKGROUND

The transition from a tooth requiring extraction to its replacement (with a dental implant) requires a series of clinical decisions related to timing, approach, materials, cost-effectiveness and the assessment of potential harm and patient preference. This workshop focused on the formulation of evidence-based consensus statements and clinical recommendations.

METHODS

Four systematic reviews covering the areas of alveolar ridge preservation/bone grafting, immediate early and delayed implant placement and alveolar bone augmentation at the time of implant placement in a healed ridge formed the basis of the deliberations. The level of evidence supporting each consensus statement and its strength was described using a modification of the GRADE tool.

RESULTS

The evidence base for each of the relevant topics was assessed and summarized in 23 consensus statements and 12 specific clinical recommendations. The group emphasized that the evidence base mostly relates to single tooth extraction/replacement; hence, external validity/applicability to multiple extractions requires careful consideration. The group identified six considerations that should assist clinicians in clinical decision-making: presence of infection, inability to achieve primary stability in the restoratively driven position, presence of a damaged alveolus, periodontal phenotype, aesthetic demands and systemic conditions.

CONCLUSIONS

A substantial and expanding evidence base is available to assist clinicians with clinical decision-making related to the transition from a tooth requiring extraction to its replacement with a dental implant. More high-quality research is needed for the development of evidence-based clinical guidelines.

Biomaterials and regenerative technologies used in bone regeneration in the craniomaxillofacial region: Consensus report of group 2 of the 15th European Workshop on Periodontology on Bone Regeneration

BACKGROUND AND AIMS

To review the regenerative technologies used in bone regeneration: bone grafts, barrier membranes, bioactive factors and cell therapies.

MATERIAL AND METHODS

Four background review publications served to elaborate this consensus report.

RESULTS AND CONCLUSIONS

Biomaterials used as bone grafts must meet specific requirements: biocompatibility, porosity, osteoconductivity, osteoinductivity, surface properties, biodegradability, mechanical properties, angiogenicity, handling and manufacturing processes. Currently used biomaterials have demonstrated advantages and limitations based on the fulfilment of these requirements. Similarly, membranes for guided bone regeneration (GBR) must fulfil specific properties and potential biological mechanisms to improve their clinical applicability. Pre-clinical and clinical studies have evaluated the added effect of bone morphogenetic proteins (mainly BMP-2) and autologous platelet concentrates (APCs) when used as bioactive agents to enhance bone regeneration. Three main approaches using cell therapies to enhance bone regeneration have been evaluated: (a) "minimally manipulated" whole tissue fractions; (b) ex vivo expanded "uncommitted" stem/progenitor cells; and (c) ex vivo expanded "committed" bone-/periosteum-derived cells. Based on the evidence from clinical trials, transplantation of cells, most commonly whole bone marrow aspirates (BMA) or bone marrow aspirate concentrations (BMAC), in combination with biomaterial scaffolds has demonstrated an additional effect in sinus augmentation and horizontal ridge augmentation, and comparable bone regeneration to autogenous bone in alveolar cleft repair.

Molecular and Cellular Aspects of Socket Healing in the Absence and Presence of Graft Materials and Autologous Platelet Concentrates: a Focused Review

OBJECTIVES

The present manuscript aims to critically detail the physiologic process of socket healing, in the absence or presence of grafting materials or platelet concentrates, addressing the associated molecular and cellular events that culminate in the restoration of the lost tissue architecture and functionality.

MATERIAL AND METHODS

An electronic search in the National Library of Medicine database MEDLINE through its online site PubMed and Web of Science from inception until May 2019 was conducted to identify articles concerning physiologic process of socket healing, in the absence or presence of grafting materials or platelet concentrates. The search was restricted to English language articles without time restriction. Additionally, a hand search was carried out in oral surgery, periodontology and dental implants related journals.

RESULTS

In total, 122 literature sources were obtained and reviewed. The detailed biological events, at the molecular and cellular level, that occur in the alveolus after tooth extraction and socket healing process modulated by grafting materials or autologous platelet concentrates were presented as two entities.

CONCLUSIONS

Tooth extraction initiates a convoluted set of orderly biological events in the alveolus, aiming wound closure and socket healing. The healing process comprises a wide range of events, regulated by the interplay of cytokines, chemokines and growth factors that determine cellular recruitment, proliferation and differentiation in the healing milieu, in a space- and time-dependent choreographic interplay. Additionally, the healing process may further be modulated by the implantation of grafting materials or autologous platelet concentrates within the tooth socket, aiming to enhance the regenerative outcome.