Advances in guided bone regeneration membranes: a comprehensive review of materials and techniques

Guided tissue/bone regeneration (GTR/GBR) is a widely used technique in dentistry to facilitate the regeneration of damaged bone and tissue, which involves guiding materials that eventually degrade, allowing newly created tissue to take its place. This comprehensive review the evolution of biomaterials for guided bone regeneration that showcases a progressive shift from non-resorbable to highly biocompatible and bioactive materials, allowing for more effective and predictable bone regeneration. The evolution of biomaterials for guided bone regeneration GTR/GBR has marked a significant progression in regenerative dentistry and maxillofacial surgery. Biomaterials used in GBR have evolved over time to enhance biocompatibility, bioactivity, and efficacy in promoting bone growth and integration. This review also probes into several promising fabrication techniques like electrospinning and latest 3D printing fabrication techniques, which have shown potential in enhancing tissue and bone regeneration processes. Further, the challenges and future direction of GTR/GBR are explored and discussed.

Fabrication of a Nanoscale Magnesium/Copper Metal-Organic Framework on Zn-Based Guided Bone Generation Membranes for Enhancing Osteogenesis, Angiogenesis, and Bacteriostasis Properties

Recently, zinc (Zn) and its alloys have demonstrated great potential as guided bone regeneration (GBR) membranes to treat the problems of insufficient alveolar bone volume and long-term osseointegration instability during dental implantology. However, bone regeneration is a complex process consisting of osteogenesis, angiogenesis, and antibacterial function. For now, the in vivo osteogenic performance and antibacterial activity of pure Zn are inadequate, and thus fabricating a platform to endow Zn membranes with multifunctions may be essential to address these issues. In this study, various bimetallic magnesium/copper metal-organic framework (Mg/Cu-MOF) coatings were fabricated and immobilized on pure Zn. The results indicated that the degradation rate and water stability of Mg/Cu-MOF coatings could be regulated by controlling the feeding ratio of Cu2+. As the coating and Zn substrate degraded, an alkaline microenvironment enriched with Zn2+, Mg2+, and Cu2+ was generated. It significantly improved calcium phosphate deposition, differentiation of osteoblasts, and vascularization of endothelial cells in the extracts. Among them, Mg/Cu1 showed the best comprehensive performance. The superior antibacterial activity of Mg/Cu1 was demonstrated in vitro and in vivo, which indicated significantly enhanced bacteriostatic activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli as compared to that of the bare sample. Bimetallic Mg/Cu-MOF coating could properly coordinate the multifunction on a Zn membrane and could be a promising platform for promoting its bone regeneration, which could pave the way for Zn-based materials to be used as barrier membranes in oral clinical trials.

Bone regeneration with hydroxyapatite particles loaded in photo-cross-linkable hydrogel: An experimental study

This study explores the use of in situ cross-linked hyaluronic acid methacryloyl (HAMA) and hydroxyapatite particles (HAP) for bone defect repair. Human periodontal ligament stem cells (PDLSCs) were isolated and co-cultured with the HAMA-HAP composite. Osteogenic differentiation was evaluated using Alizarin Red staining, alkaline phosphatase activity quantification, and polymerase chain reaction (PCR). A cranial defect was induced in Sprague-Dawley rats. This defect was then filled with the HAMA-HAP composite and cross-linked using UV light exposure. Bone formation was assessed through radiographic and histological analyses. The HAMA-HAP composite was found to promote cell viability similarly to pure HAP. It also enhanced gene expression of ALP, OPN, and Runx2, and increased ALP activity and mineralized nodule formation in vitro. Micro-CT scans showed defect restoration in the HAMA-HAP and HAP groups compared to the control group. The HAMA-HAP group exhibited higher Tb.N, Tb.Sp, Tb.Th, and BV/TV. Masson staining showed the HAMA-HAP composite restored the defect site, with new bone formation thicker than in the HAP group. The HAMA-HAP composite showed excellent biocompatibility and promoted osteogenic differentiation of PDLSCs. It effectively repaired cranial defects, indicating its potential for clinical use in bone defect repair.

Decellularized periosteum promotes guided bone regeneration via manipulation of macrophage polarization

Periosteum has shown potential as an effective barrier membrane for guided bone regeneration (GBR). However, if recognized as a "foreign body," insertion of a barrier membrane in GBR treatment will inevitably alter the local immune microenvironment and subsequently influence bone regeneration. The aim of this investigation was to fabricate decellularized periosteum (DP) and investigate its immunomodulatory properties in GBR. DP was successfully fabricated from periosteum from the mini-pig cranium. In vitro experiments indicated that the DP scaffold modulated macrophage polarization toward a pro-regenerative M2 phenotype, which in turn facilitated migration and osteogenic differentiation of bone marrow-derived mesenchymal stem cells. A rat GBR model with a cranial critical-size defect was established, and our in vivo experiment confirmed the beneficial effects of DP on the local immune microenvironment and bone regeneration. Collectively, the findings of this study indicate that the prepared DP possesses immunomodulatory properties and represents a promising barrier membrane for GBR procedures.

A Prospective Study of the Assessment of the Efficacy of a Biodegradable Poly(l-lactic acid/ε-caprolactone) Membrane for Guided Bone Regeneration

Biodegradable guided bone regeneration (GBR) membranes consist primarily of collagen and aliphatic polyesters. This study assessed the comparative efficacy of a poly(l-lactic-caprolactone) [P(LA/CL)] membrane versus that of a collagen membrane in GBR. Patients requiring GBR simultaneously or before dental implant placement in edentulous regions were randomly assigned to one of two membranes. Within each membrane, they were subdivided into 3 groups: dental implants were placed simultaneously with GBR in groups A and B, and 180 days post-GBR in group C. The augmented bone width was measured at 1, 3, and 6 mm from the implant's neck (groups A and B) or the reference line (group C), utilizing cone-beam computed tomography images, immediately and 150 days post-surgery. A histological study was performed to evaluate bone formation in group C. No adverse events were observed. In the collagen group, the absorbed ratios of the augmented bone were 40.9 ± 36.7%, 29.4 ± 30.1%, and 11.1 ± 22.0% at 1, 3, and 6 mm, respectively; the ratio at 6 mm was significantly lower than that at 1 mm (p = 0.0442). In the P(LA/CL) group, those were 26.2 ± 27.3%, 17.1 ± 19.7%, and 13.3 ± 16.4% at 1, 3, and 6 mm, respectively, with no significant difference at each point. No significant inter-membrane differences were observed. The bone augmentation potential of the P(LA/CL) membrane matched that of the collagen membrane. P(LA/CL) could be used as a safe and effective membrane in GBR.

Occlusive and Proliferative Properties of Different Collagen Membranes-An In Vitro Study

Different collagen barrier membranes come in various sources and crosslinking that may affect barrier function and tissue integration. This study investigated barrier function and tissue integration of the three different collagen membranes (Jason^®: porcine pericardium, GENOSS: bovine tendon, and BioMend^® Extend: cross-linked bovine tendon) with human gingival fibroblasts. The barrier function and tissue integration properties were determined under confocal microscopy. Morphological characteristics were observed using scanning electron microscopy. Our results showed that all collagen membranes allowed a small number of cells to migrate, and the difference in barrier function ability was not significant. The cross-linked characteristics did not improve barrier ability. The native collagen membrane surfaces allowed evenly scattered proliferation of HGF, while the cross-linked collagen membrane induced patchy proliferation. Statistically significant differences in cell proliferation were found between Jason and BioMend Extend membranes (p = 0.04). Scanning electron microscope showed a compact membrane surface at the top, while the bottom surfaces displayed interwoven collagen fibers, which were denser in the crosslinked collagen membranes. Within the limitations of this study, collagen membranes of different origins and physical properties can adequately prevent the invasion of unwanted cells. Native collagen membranes may provide a better surface for gingival cell attachment and proliferation.

The Use of Lactide Polymers in Bone Tissue Regeneration in Dentistry-A Systematic Review

(1) Background: Different compositions of biodegradable materials are being investigated to successfully replace non-resorbable ones in bone tissue regeneration in dental surgery. The systematic review tried to address the question, "Can biodegradable polymers act as a replacement for conventional materials in dental surgery procedures?" (2) Methods: An electronic search of the PubMed and Scopus databases was conducted in October 2022. The following keywords were used: (lactide polymers) and (hydroxyapatite or fluorapatite) and (dentistry) and (regeneration). Initially, 59 studies were found. Forty-one studies met the inclusion criteria and were included in the review. (3) Results: These usually improved the properties and induced osteogenesis, tissue mineralisation and bone regeneration by inducing osteoblast proliferation. Five studies showed higher induction of osteogenesis in the case of biomaterials, UV-HAp/PLLA, ALBO-OS, bioresorbable raw particulate hydroxyapatite/poly-L-lactide and PLGA/Hap, compared to conventional materials such as titanium. Four studies confirmed improvement in tissue mineralisation with the usage of biomaterials: hydroxyapatite/polylactic acid (HA/PLA) loaded with dog's dental pulp stem cells (DPSCs), Coll/HAp/PLCL, PDLLA/VACNT-O:nHAp, incorporation of hydroxyapatite and simvastatin. Three studies showed an acceleration in proliferation of osteoblasts for the use of biomaterials with additional factors such as collagen and UV light. (4) Conclusions: Lactide polymers present higher osteointegration and cell proliferation rate than the materials compared. They are superior to non-biodegradable materials in terms of the biocompability, bone remodelling and healing time tests. Moreover, because there is no need of reoperation, as the material automatically degrades, the chance of scars and skin sclerosis is lower. However, more studies involving greater numbers of biomaterial types and mixes need to be performed in order to find a perfect biodegradable material.

Single-Walled Carbon Nanotube Membranes Accelerate Active Osteogenesis in Bone Defects: Potential of Guided Bone Regeneration Membranes

Carbon nanotubes (CNTs) are potentially important biomaterials because of their chemical, physical, and biological properties. Our research indicates that CNTs exhibit high compatibility with bone tissue. The guided bone regeneration (GBR) technique is commonly applied to reconstruct alveolar bone and treat peri-implant bone defects. In GBR, bone defects are covered with a barrier membrane to prevent the entry of nonosteogenic cells such as epithelial cells and fibroblasts. The barrier membrane also maintains a space for new bone formation. However, the mechanical and biological properties of materials previously used in clinical practice sometimes delayed bone regeneration. In this study, we developed a CNT-based membrane for GBR exhibiting high strength to provide a space for bone formation and provide cellular shielding to induce osteogenesis. The CNT membrane was made via the dispersion of single-walled CNTs (SWCNTs) in hyaluronic acid solution followed by filtration. The CNT membrane assumed a nanostructure surface due to the bundled SWCNTs and exhibited high strength and hydrophilicity after oxidation. In addition, the membrane promoted the proliferation of osteoblasts but not nonosteogenic cells. CNT membranes were used to cover experimental bone defects made in rat calvaria. At 8 weeks after surgery, more extensive bone formation was observed in membrane-covered defects compared with bone defects not covered with membrane. Almost no diffusion of CNTs was observed around the membrane. These results indicate that the CNT membrane has adequate strength, stability, and surface characteristics for osteoblasts, and its shielding properties promote bone formation. Demonstration of the safety and osteogenic potential of the CNT membranes through further animal studies should facilitate their clinical application in GBR.

Horizontal Augmentation of Chronic Mandibular Defects by the Guided Bone Regeneration Approach: A Randomized Study in Dogs

Various biomaterial combinations have been studied focusing on their ability to stabilize blood clots and maintain space under soft tissue to support new bone formation. A popular combination is Deproteinized Bovine Bone Mineral (DBBM) placed with a native collagen membrane (NCM) tacked to native bone. In this study, we compared the outcome of this treatment option to those achieved with three different graft/membrane combinations with respect to total newly occupied area and the mineralized compound inside. After bi-lateral extraction of two mandibular premolars in five adult beagles L-shaped alveolar defects were created. A total of 20 defects healed for 6 weeks resulting in chronic type bone defects. At baseline, four options were randomly allocated to five defects each: a. DBBM + NCM with a four-pin fixation across the ridge; b. DBBM + RCLC (ribose cross-linked collagen membrane); c. DBBM + NPPM (native porcine pericardium membrane); and d. Ca-sulfate (CS) + RCLC membrane. Membranes in b/c/d were not fixed; complete tensionless wound closure was achieved by CAF. Termination after 3 months and sampling followed, and non-decalcified processing and toluidine blue staining were applied. Microscopic images obtained at standardized magnification were histomorphometrically assessed by ImageJ software (NIH). An ANOVA post hoc test was applied; histomorphometric data are presented in this paper as medians and interquartile ranges (IRs). All sites healed uneventfully, all sites were sampled and block separation followed before Technovit embedding. Two central sections per block for each group were included. Two of five specimen were lost due to processing error and were excluded from group b. New bone area was significantly greater for option b. compared to a. (p = 0.001), c. (p = 0.002), and d. (p = 0.046). Residual non-bone graft area was significantly less for option d. compared to a. (p = 0.026) or c. (p = 0.021). We conclude that collagen membranes with a prolonged resorption/barrier profile combined with bone substitutes featuring different degradation profiles sufficiently support new bone formation. Tacking strategy/membrane fixation appears redundant when using these biomaterials.

Biocompatibility Analyses of HF-Passivated Magnesium Screws for Guided Bone Regeneration (GBR)

Background: Magnesium (Mg) is one of the most promising materials for human use in surgery due to material characteristics such as its elastic modulus as well as its resorbable and regenerative properties. In this study, HF-coated and uncoated novel bioresorbable magnesium fixation screws for maxillofacial and dental surgical applications were investigated in vitro and in vivo to evaluate the biocompatibility of the HF coating. Methods: Mg alloy screws that had either undergone a surface treatment with hydrofluoric-acid (HF) or left untreated were investigated. In vitro investigation included XTT, BrdU and LDH in accordance with the DIN ISO 10993-5/-12. In vivo, the screws were implanted into the tibia of rabbits. After 3 and 6 weeks, degradation, local tissue reactions and bony integration were analyzed histopathologically and histomorphometrically. Additionally, SEM/EDX analysis and synchrotron phase-contrast microtomography (µCT) measurements were conducted. The in vitro analyses revealed that the Mg screws are cytocompatible, with improved results when the surface had been passivated with HF. In vivo, the HF-treated Mg screws implanted showed a reduction in gas formation, slower biodegradation and a better bony integration in comparison to the untreated Mg screws. Histopathologically, the HF-passivated screws induced a layer of macrophages as part of its biodegradation process, whereas the untreated screws caused a slight fibrous tissue reaction. SEM/EDX analysis showed that both screws formed a similar layer of calcium phosphates on their surfaces and were surrounded by bone. Furthermore, the µCT revealed the presence of a metallic core of the screws, a faster absorbing corrosion front and a slow absorbing region of corroded magnesium. Conclusions: Overall, the HF-passivated Mg fixation screws showed significantly better biocompatibility in vitro and in vivo compared to the untreated screws.

Novel Histomorphometrical Approach to Evaluate the Integration Pattern and Functionality of Barrier Membranes

GBR (guided bone regeneration) is a standard procedure for building up bony defects in the jaw. In this procedure, resorbable membranes made of bovine and porcine collagen are increasingly being used, which, in addition to many possible advantages, could have the potential disadvantage of a shorter barrier functionality, especially when augmenting large-volume defects. Thus, it is of importance to evaluate the integration behavior and especially the standing time of barrier membranes using specialized methods to predict its respective biocompatibility. This study is intended to establish a new histomorphometrical analysis method to quantify the integration rate of collagen-based barrier membranes. Three commercially available barrier membranes, i.e., non-crosslinked membranes (BioGide^® and Jason^® membrane), a ribose-crosslinked membrane (Ossix^® Plus), and a newly developed collagen–hyaluronic acid-based (Coll-HA) barrier membrane were implanted in the subcutaneous tissue of 48 6–8-week-old Wistar rats. The explants, after three timepoints (10, 30, and 60 days), were processed and prepared into histological sections for histopathological (host tissue response) and histomorphometrical (cellular invasion) analyses. 10 days after implantation, fragmentation was not evident in any of the study groups. The sections of the Coll-HA, Jason^® and BioGide^® membranes showed a similar mild inflammatory reaction within the surrounding tissue and an initial superficial cell immigration. Only in the Ossix^® Plus group very little inflammation and no cell invasion was detected. While the results of the three commercially available membranes remained intact in the further course of the study, only fragments of the Coll-HA membrane were found 30 and 60 days after implantation. Histomorphometrically, it can be described that although initially (at 10 days post-implantation) similar results were found in all study groups, after 30 days post-implantation the cellular penetration depth of the hyaluronic acid-collagen membrane was significantly increased with time (**** p < 0.0001). Similarly, the percentage of cellular invasion per membrane thickness was also significantly higher in the Coll-HA group at all timepoints, compared to the other membranes (**** p < 0.0001). Altogether, these results show that the histomorphometrical analysis of the cellular migration can act as an indicator of integration and duration of barrier functionality. Via this approach, it was possible to semi-quantify the different levels of cellular penetration of GBR membranes that were only qualitatively analyzed through histopathological approaches before. Additionally, the results of the histopathological and histomorphometrical analyses revealed that hyaluronic acid addition to collagen does not lead to a prolonged standing time, but an increased integration of a collagen-based biomaterial. Therefore, it can only partially be used in the dental field for indications that require fast resorbed membranes and a fast cell or tissue influx such as periodontal regeneration processes.

The influence of initial defect morphology of alveolar ridge on volumetric change of grafted bone following guided bone regeneration in the anterior maxilla region: an exploratory retrospective study

Background

This study aimed to explore the influence of initial ridge defect morphology on the outcome of guided bone regeneration (GBR) in the anterior maxilla region.

Methods

Cone beam computed tomography (CBCT) examinations of patients who participated in a previous randomized controlled trial were used to assess linear and volumetric changes of bone grafts (LCB and VCB) from immediately (T0) to 6 months (T1) after surgery. The three-dimensional (3D) surface rendering of the initial defect was reconstructed, and morphological variables were defined in mesial-distal, buccal-lingual, and coronal-apical directions. The Spearman correlation, logistic regression model, and receiver operating characteristic (ROC) analyses were used to assess the possible association between initial defect morphological variables and VCB.

Results

A total of 62 eligible patients were included in this study. The median value of LCB was less than 20% at different levels, while the corresponding value of VCB was 52.0%. The Spearman correlation analysis showed that the standard deviation of buccal-lingual distance (BL_SD) was negatively associated with VCB (r=-0.315, P=0.013), whereas the ratio of maximum coronal-apical/mesial-distal distance (R_mCA/mMD) was positively related to VCB (r=0.607, P<0.001). The multivariate regression analysis revealed that the prognosis effect of BLSD (OR: 0.220, 95% CI: 0.074 to 0.655, P=0.0047) and R_mCA/mMD (OR: 7.045, 95% CI: 2.361 to 21.024, P=0.0017) remained significant. ROC curve analysis showed that R_mCA/mMD could be used to correctly classify VCB in 78.9% patients and BLSD in 71.0% of patients, as classified by the median of VCB. The discrimination value of BLSD and R_mCA/mMD revealed the areas under curve (AUC) of 0.71 (95% CI: 0.545 to 0.883) and 0.74 (95% CI: 0.573 to 0.913), respectively.

Conclusions

Within the limitations of this study, the present data confirmed the effect of initial ridge morphology on the GBR outcome in the anterior maxilla region. Specifically, a defect morphology with more BLSD and/or lower R_mCA/mMD may significantly decrease the resorption amount of grafted bone.

Implantation of an Injectable Bone Substitute Material Enables Integration Following the Principles of Guided Bone Regeneration

BACKGROUND/AIM

The present study investigates the in vivo tissue reaction and the integration behavior of an injectable bone substitute material (IBS) composed of a water-based gel combined with nano hydroxyapatite particles and biphasic calcium phosphate granules. The results of the IBS were compared to biphasic bone substitute granules (BBSM) of the same chemical composition.

MATERIALS AND METHODS

The subcutaneous implantation model in 40 female 5-week-old CD-1 mice up to 60 days after implantation was used for conduction of the in vivo experiments. Moreover, established histological, histopathological and histomorphometrical methods were applied.

RESULTS

The results showed that the IBS was gradually invaded by cells and complex tissue elements. Thus, the implant bed could be distinguished in two areas, i.e. an outer and inner region. While the outer region started to interact with the peri-implant tissue by evoking multinucleated giant cells and at earlier time points by undergoing a continuous high vascularization, the inner part was free of peri-implant cells for at least 30 days, starting to undergo a similar tissue reaction at a later time point. The bone substitute granules allowed for a fast tissue influx between the interspaces of the granules starting at day 10. While the vessel density did not differ in both groups up to the end of the study, the amount of vascularization was significantly higher over the entire observation period in the BBSM group. Moreover, the amount of biomaterial-associated multinucleated giant cells (BMGCs) was significantly higher in the IBS group in the period of between 15 to 30 days after implantation, while comparable BMGC numbers were found in both groups towards the end of the study.

CONCLUSION

IBS can build a barrier-like structure that is able to control the soft tissue influx into the central regions of the implantation bed, which could not be observed in other bone substitute granules of the same chemical composition. This directed integration behavior is assumed to be in accordance with the concept of Guided Bone Regeneration (GBR). Furthermore, BMGCs can significantly influence the process of angiogenesis within an implant bed of a biomaterial but not the maturity of blood vessels.

Allogeneic cortical struts and bone granules for challenging alveolar reconstructions: An innovative approach toward an established technique

OBJECTIVE

The shell technique is a well-established procedure for GBR with which extensive osseous defects can be predictably restored by using cortical bone struts harvested from various intraoral aspects. Recent publications have demonstrated comparable results for autologous and allogeneic bone grafts, whereas the evidence on allogeneic cortical struts remains limited.

CLINICAL CONSIDERATIONS

In this case series, we demonstrate the regeneration of five complex alveolar bone defects in four patients with subsequent insertion of fixed dental implants. In all cases, cortical struts made from human donor bone were applied in combination with allogeneic bone granules and collagen membranes.

CONCLUSIONS

Similar to autologous cortical shells, the allogeneic struts functioned by creating an immobile container with which the osseous defects in all patients could be successfully restored, enabling placement of dental implants in accordance with the treatment plan. Even when the containers were solely filled with allogeneic granules, vascularized healthy tissue was present at re-entry, demonstrating the vast potential of these materials for applications in dentistry.

CLINICAL SIGNIFICANCE

Especially when it comes to regeneration of complex alveolar bone defects, autologous bone grafts are often outlined as the only treatment modality. Here we show that innovative biomaterials like allogeneic bone grafts hold the potential to mimic the functions of autologous bone transplants and provide excellent clinical results without the requirement of a second surgical side for bone harvesting and no risk of donor-site morbidity.

Evaluation of Biocompatibility of Different Membrane Surfaces Using Unrestricted Somatic Stem Cells

BACKGROUND/AIM

Results of Guided Bone Regeneration (GBR) primarily depend on the membrane used. The aim of this study was to compare biocompatibility of different absorbable and non-absorbable membranes by using unrestricted somatic stem cells (USSCs) as an indicator for biocompatibility.

MATERIALS AND METHODS

Five absorbable membranes (Bio-Gide®, RESODONT®, GENTA-FOIL resorb®, BioMend® and BioMend® Extend™) and one non-absorbable alternative (GORE-TEX®) were colonized with USSCs. After 24 h, 3 days and 7 days, cell proliferation, cell viability, and cytotoxicity were assessed. Moreover, cell morphology was evaluated by electron microscopy.

RESULTS

Significantly higher cell proliferation and cell viability rates were observed in Bio-Gide® and RESODONT® membranes. Cell toxicity was highest on GENTA-FOIL resorb® membranes. The electron microscopical assessment showed a better cell attachment on porous surfaced membranes.

CONCLUSION

This study shows that USSCs can be used for assessments of biocompatibility, and that absorbable membranes with collagenous composition and porous structure tend to positively impact biocompatibility and enhance cell proliferation.

Prolonged Biodegradation and Improved Mechanical Stability of Collagen via Vapor-Phase Ti Stitching for Long-Term Tissue Regeneration

Collagen, one of the most popular biomedical materials, exhibits rapid biodegradation accompanied by a notable decrease of mechanical stability in the human body. This is a key challenge for its use in large-sized tissue regeneration, which takes a long time. In order to resolve this problem, we introduced vapor-phase titanium (Ti) derivatives into the interchain regions in collagen via TiO₂ atomic layer deposition (ALD), which has been widely used for thin-film deposition. The introduced Ti simultaneously enhanced both the tensile strength (∼384.45 MPa) and Young's modulus (∼1.56 GPa) by approximately 29 and 26% compared to the pristine commercial collagen membrane. In vitro tests demonstrated that approximately 31% of Ti-infiltrated collagen is retained after 4 weeks, whereas the pristine commercial collagen rapidly degrades by up to 90% within 1 week. The in vivo biodegradation rate was greatly improved and inversely proportional to the number of TiO₂ ALD cycles. Moreover, bone mineralization, which is observed during the late stage of bone healing, appeared only in the Ti-infiltrated collagen. We believe that our simple vapor-phase treatment method could be widely used with xenograft materials, which typically require adequate biodegradation rates and stable mechanical properties.

A Novel Bilayer Polycaprolactone Membrane for Guided Bone Regeneration: Combining Electrospinning and Emulsion Templating

Guided bone regeneration is a common dental implant treatment where a barrier membrane (BM) is used between epithelial tissue and bone or bone graft to prevent the invasion of the fast-proliferating epithelial cells into the defect site to be able to preserve a space for infiltration of slower-growing bone cells into the periodontal defect site. In this study, a bilayer polycaprolactone (PCL) BM was developed by combining electrospinning and emulsion templating techniques. First, a 250 µm thick polymerised high internal phase emulsion (polyHIPE) made of photocurable PCL was manufactured and treated with air plasma, which was shown to enhance the cellular infiltration. Then, four solvent compositions were investigated to find the best composition for electrospinning a nanofibrous PCL barrier layer on PCL polyHIPE. The biocompatibility and the barrier properties of the electrospun layer were demonstrated over four weeks in vitro by histological staining. Following in vitro assessment of cell viability and cell migration, cell infiltration and the potential of PCL polyHIPE for supporting blood vessel ingrowth were further investigated using an ex-ovo chick chorioallantoic membrane assay. Our results demonstrated that the nanofibrous PCL electrospun layer was capable of limiting cell infiltration for at least four weeks, while PCL polyHIPE supported cell infiltration, calcium and mineral deposition of bone cells, and blood vessel ingrowth through pores.

Bilateral maxillary augmentation using CAD/CAM manufactured allogenic bone blocks for restoration of congenitally missing teeth: A case report

OBJECTIVE

Various biomaterials have been successfully applied in alveolar bone regeneration, however, the reconstruction of extensive osseous defects remains challenging and is often unfeasible with granular grafting materials. Several studies have outlined allogenic bone blocks as valid alternative to autologous block grafting.

CLINICAL CONSIDERATIONS

In this report, we demonstrate the regeneration of two large osseous defects in the maxilla with allogenic bone blocks made from human donor bone. The bone blocks were customized using the CAD/CAM technology in order to enable the insertion of four dental implants.

CONCLUSIONS

Both blocks perfectly matched the defect geometry, showed limited resorption, led to the formation of sufficient amounts of mineralized bone in both horizontal and vertical dimensions and enabled the installation of implants according to the treatment plan. The implementation of innovative technologies for individualization of allogenic bone blocks simplifies the restoration of complex and extensive osseous defects and poses great benefits for both practitioners and patients.

CLINICAL SIGNIFICANCE

The here presented procedure demonstrates the successful regeneration of two extensive osseous defects in a patient suffering from hypodontia using two CAD/CAM manufactured allogenic bone blocks, rendering the procedure far less invasive as compared to guided bone regeneration carried out with autologous transplants. Furthermore, to the best of our knowledge, this is the first case report that radiographically demonstrates the new formation of a cortical bone layer following block grafting with solely cancellous bone blocks.

The Efficacy of Electron Beam Irradiated Bacterial Cellulose Membranes as Compared with Collagen Membranes on Guided Bone Regeneration in Peri-Implant Bone Defects

Bacterial cellulose (BC) is a natural polysaccharide produced by some bacteria, and consists of a linear polymer linked by β-(1,4) glycosidic bonds. BC has been developed as a material for tissue regeneration purposes. This study was conducted to evaluate the efficacy of resorbable electron beam irradiated BC membranes (EI-BCMs) for guided bone regeneration (GBR). The electron beam irradiation (EI) was introduced to control the biodegradability of BC for dental applications. EI-BCMs had higher porosity than collagen membranes (CMs), and had similar wet tensile strengths to CMs. NIH3T3 cell adhesion and proliferation on EI-BCMs were not significantly different from those on CMs (p > 0.05). Micro-computed tomography (μCT) and histometric analysis in peri-implant dehiscence defects of beagle dogs showed that EI-BCMs were non-significantly different from CMs in terms of new bone area (NBA; %), remaining bone substitute volume (RBA; %) and bone-to-implant contact (BIC; %) (p > 0.05). These results suggest resorbable EI-BCMs can be used as an alternative biomaterial for bone tissue regeneration.

Effects of 3D-Printed Polycaprolactone/β-Tricalcium Phosphate Membranes on Guided Bone Regeneration

This study was conducted to compare 3D-printed polycaprolactone (PCL) and polycaprolactone/β-tricalcium phosphate (PCL/β-TCP) membranes with a conventional commercial collagen membrane in terms of their abilities to facilitate guided bone regeneration (GBR). Fabricated membranes were tested for dry and wet mechanical properties. Fibroblasts and preosteoblasts were seeded into the membranes and rates and patterns of proliferation were analyzed using a kit-8 assay and by scanning electron microscopy. Osteogenic differentiation was verified by alizarin red S and alkaline phosphatase (ALP) staining. An in vivo experiment was performed using an alveolar bone defect beagle model, in which defects in three dogs were covered with different membranes. CT and histological analyses at eight weeks after surgery revealed that 3D-printed PCL/β-TCP membranes were more effective than 3D-printed PCL, and substantially better than conventional collagen membranes in terms of biocompatibility and bone regeneration and, thus, at facilitating GBR.

A novel silk fibroin nanofibrous membrane for guided bone regeneration: a study in rat calvarial defects

A novel membrane for guided bone regeneration (GBR), constituting silk fibroin (SF) nanofiber from native silk nanofibril solution, was prepared by electrospinning process. Another barrier membrane, a collagen-type membrane (Bio-Gide®), was used as a comparative sample. Twelve healthy male Sprague-Dawley rats were used in this study. Bilateral round defects were created in the calvarial bone. The bone regenerative efficacy was evaluated in rat calvarial defects. Animals were killed at 4 and 12 weeks. Bone regeneration was analyzed using micro-computed tomography and histological analysis. The SF nanofibrous membrane showed superior results with regard to mechanical tensile properties. At 4 weeks, the bone volume and collagen I positive areas in the SF group were greater than in the Bio-Gide group. At 12 weeks, the defect had completely healed with new bone in both the groups. In conclusion, the SF nanofibrous membranes showed satisfactory mechanical stability, good biocompatibility, slow degradability, and improved new bone regeneration without any adverse inflammatory reactions. Considering the low cost and low risk of disease transmission, the SF nanofibrous membrane is a potential candidate for GBR therapy compared with the widely used collagen membranes.

Porcine Dermis-Derived Collagen Membranes Induce Implantation Bed Vascularization Via Multinucleated Giant Cells: A Physiological Reaction?

In this study, the tissue reactions to 2 new porcine dermis-derived collagen membranes of different thickness were analyzed. The thicker material (Mucoderm) contained sporadically preexisting vessel skeletons and fatty islands. The thinner membrane (Collprotect) had a bilayered structure (porous and occlusive side) without any preexisting structures. These materials were implanted subcutaneously in mice to analyze the tissue reactions and potential transmembranous vascularization. Histological and histomorphometrical methodologies were performed at 4 time points (3, 10, 15, and 30 days). Both materials permitted stepwise connective tissue ingrowth into their central regions. In the Mucoderm matrix, newly built microvessels were found within the preexisting vessel and fatty island skeletons after 30 days. This vascularization was independent of the inflammation-related vascularization on both material surfaces. The Collprotect membrane underwent material disintegration by connective tissue strands in combination with vessels and multinucleated giant cells. The histomorphometric analyses revealed that the thickness of Mucoderm did not decrease significantly, while an initial significant decrease of membrane thickness in the case of Collprotect was found at day 15. The present results demonstrate that the 2 analyzed collagen membranes underwent a multinucleated giant cell-associated vascularization. Neither of the materials underwent transmembraneous vascularization. The microvessels were found within the preexisting vessel and fatty island skeletons. Additional long-term studies and clinical studies are necessary to determine how the observed foreign body giant cells affect tissue regeneration.

Biomaterials in maxillofacial surgery: membranes and grafts

Today, significant differences in the use of biomaterials (membranes and grafts) of animal or synthetic origin have yet to be reported. Nevertheless, some evidences suggest that synthetic materials have a lower risk of disease transmission. This review aims to assess the available informations on regenerative bone technique using reasorbable membranes and bone grafts. In particular, biocompatibility, immunological response, tissue reaction, reabsorption time and histological features of materials daily use in dentistry and in maxillofacial surgery were emphasized.