Controlled-release of bone morphogenetic protein-2 from a microsphere coating applied to acid-etched Ti6AL4V implants increases biological bone growth in vivo

Assessment of the Impact of Bone Quality and Abutment Configuration on the Fatigue Performance of Dental Implant Systems Using Finite Element Analysis (FEA)

BACKGROUND AND OBJECTIVES

The aim of this study was to evaluate the influence of abutment angulation, types, and bone quality on fatigue performance in dental implant systems.

MATERIALS AND METHODS

Three-dimensional models of maxillary 3-unit fixed implant-supported prostheses were analyzed. Abutments with different angles and types were used. Healthy bone (Hb) and resorbed bone (Rb) were used. Conducted on implants, a force of 150 N was applied obliquely, directed from the palatal to the buccal aspect, at a specific angle of 30 degrees. The stress distribution and fatigue performance were then evaluated considering the types of bone used and the angles of the three different abutments. The simulation aspect of the research was carried out utilizing Abaqus 2020 software.

RESULTS

In all models, fatigue strengths in healthy bone were higher than in resorbed bone. Maximum stress levels were seen in models with angled implants. In almost all models with resorbed bone, fatigue performances were slightly lower.

CONCLUSIONS

Increasing the abutment angle has been shown to increase stress levels and decrease fatigue performance in the adjacent bone and along the implant-abutment interface. In general, implants applied to healthy bone were found to have a higher success rate. It has also been suggested that multiunit abutments have beneficial effects on stress distribution and fatigue performance compared to resin cemented abutments. The type or angle of abutment and the quality of the bone can lead to biomechanical changes that affect the force distribution within the bone structure surrounding the implant. Clinicians can influence the biomechanical environment of the implant site by varying the abutment angle and type to suit the condition of bone health, potentially affecting the long-term success of implant treatment.

Local delivery and controlled release of miR-34a loaded in hydroxyapatite/mesoporous organosilica nanoparticles composite-coated implant wire to accelerate bone fracture healing

Immediate mechanical stability is a prerequisite for fracture healing. In addition to bringing immediate mechanical stability in fracture site, implants with bioactive coating can release active substance to accelerate bone-fracture healing. However, limited drug-loading capacity of established coatings weakens their biological functions, which urges the engineering of more effective coating biomaterials for accelerating fracture healing. Herein, mesoporous organosilica nanoparticles (MONs), as miR-34a delivers, are loaded onto hydroxyapatite (HA)-coated Kirschner wire to engineer a HA/MONs@miR-34a composite coating. The composite coating can effectively deliver miR-34a into osteoclasts, generate gene dose-dependent inhibiting effect on differentiation and resorptive activity of osteoclasts by regulating multiple downstream gene expression at the early stage of fracture healing, which additionally exhibits decent bone regeneration potentials as evidenced in rat tibial fracture model. In particular, differentially expressed genes regulated by miR-34a are identified using RNA-seq followed by bioinformatics analysis. Functional enrichment analysis reveals that genes with altered expression mainly distribute in mainly distribute in DNA replication and cell cycle, which are associated with the development of osteoclasts. This work not only demonstrates the high clinical translation potential of HA/MONs@miR-34a to accelerate fracture healing, but also reveals the underlying molecular mechanism of regulating physiological functions of osteoclasts based on analysis of singlecell RNA sequencing.

Sintered porous Ti6Al4V scaffolds incorporated with recombinant human bone morphogenetic protein-2 microspheres and thermosensitive hydrogels can enhance bone regeneration

A well-controlled powder sintering technique was used to fabricate porous Ti6Al4V scaffold. The thermosensitive chitosan thioglycolic acid (CS-TA) hydrogel was used as a carrier to inject recombinant human bone morphogenetic protein-2 (rhBMP-2) microspheres into pores of the Ti6Al4V scaffold at 37 °C, and then the porous Ti6Al4V/rhBMP-2 loaded hydrogel composite was obtained. The bare Ti6Al4V scaffold was used as the control. The characteristics and mechanical properties of the scaffold, rheological properties of the hydrogels and the rhBMP-2 loaded hydrogel, the release of the rhBMP-2 loaded hydrogel, and the biological properties of the two types of samples were evaluated by in vitro and in vivo tests. Results indicated that the sintered porous Ti6Al4V had high porosity, large pore size with good mechanical properties. The hydrogel and rhBMP-2 loaded hydrogel showed thermosensity. The rhBMP-2 loaded hydrogel showed a stable and extended release profile without too high burst release of rhBMP-2. Both groups showed good biocompatibility and osteogenic ability. However, according to the results of cell tests and implantation, the group with rhBMP-2 loaded hydrogel had significantly higher cell proliferation rate, faster bone growth speed, and more bone ingrowth at every time point. Therefore, the sintered porous Ti6Al4V scaffolds incorporated with rhBMP-2 microspheres and CS-TA hydrogel was effective in enhancing the bone regeneration, and prospects a good candidate for application in orthopedics.

Recent coating developments for combination devices in orthopedic and dental applications: A literature review

Orthopedic and dental implants have been used successfully for decades to replace or repair missing or damaged bones, joints, and teeth, thereby restoring patient function subsequent to disease or injury. However, although device success rates are generally high, patient outcomes are sometimes compromised due to device-related problems such as insufficient integration, local tissue inflammation, and infection. Many different types of surface coatings have been developed to address these shortcomings, including those that incorporate therapeutic agents to provide localized delivery to the surgical site. While these coatings hold enormous potential for improving device function, the list of requirements that an ideal combination coating must fulfill is extensive, and no single coating system today simultaneously addresses all of the criteria. Some of the primary challenges related to current coatings are non-optimal release kinetics, which most often are too rapid, the potential for inducing antibiotic resistance in target organisms, high susceptibility to mechanical abrasion and delamination, toxicity, difficult and expensive regulatory approval pathways, and high manufacturing costs. This review provides a survey of the most recent developments in the field, i.e., those published in the last 2-3years, with a particular focus on technologies that have potential for overcoming the most significant challenges facing therapeutically-loaded coatings. It is concluded that the ideal coating remains an unrealized target, but that advances in the field and emerging technologies are bringing it closer to reality. The significant amount of research currently being conducted in the field provides a level of optimism that many functional combination coatings will ultimately transition into clinical practice, significantly improving patient outcomes.

SLM produced porous titanium implant improvements for enhanced vascularization and osteoblast seeding

To improve well-known titanium implants, pores can be used for increasing bone formation and close bone-implant interface. Selective Laser Melting (SLM) enables the production of any geometry and was used for implant production with 250-µm pore size. The used pore size supports vessel ingrowth, as bone formation is strongly dependent on fast vascularization. Additionally, proangiogenic factors promote implant vascularization. To functionalize the titanium with proangiogenic factors, polycaprolactone (PCL) coating can be used. The following proangiogenic factors were examined: vascular endothelial growth factor (VEGF), high mobility group box 1 (HMGB1) and chemokine (C-X-C motif) ligand 12 (CXCL12). As different surfaces lead to different cell reactions, titanium and PCL coating were compared. The growing into the porous titanium structure of primary osteoblasts was examined by cross sections. Primary osteoblasts seeded on the different surfaces were compared using Live Cell Imaging (LCI). Cross sections showed cells had proliferated, but not migrated after seven days. Although the cell count was lower on titanium PCL implants in LCI, the cell count and cell spreading area development showed promising results for titanium PCL implants. HMGB1 showed the highest migration capacity for stimulating the endothelial cell line. Future perspective would be the incorporation of HMGB1 into PCL polymer for the realization of a slow factor release.

Antigen-extracted xenogeneic cancellous bone graft with recombinant human bone morphogenetic protein-2 enhances bone regeneration in repair of mandibular defect in rabbits

The effects of a large-piece of xenogeneic bone that was separated from healthy pigs as a scaffold for the repair of a mandibular defect was investigated, and the applicability of antigen-extracted xenogeneic cancellous bone (AXCB) soaked with recombinant human bone morphogenetic protein-2 (rhBMP-2) in bone defect repair was assessed. Mandibular defects were created in 48 New Zealand rabbits, and the animals were randomly divided into four groups, in which the mandibular defects were grafted with AXCB, AXCB soaked with rhBMP-2, and autograft bone, or left blank. An equal number of animals from each group were classified into three time points (4, 8, and 12 weeks) after surgery for gross pathological observation, hematoxylin and eosin (H and E) staining, radiographic examination, and bone density measurement. H and E staining revealed that the area percentage of bone regeneration in the group of the AXCB/rhBMP-2 graft was 27.72 ± 4.68, 53.90 ± 21.92, and 77.35 ± 9.83 at 4 weeks, 8 weeks, and 12 weeks, respectively. These results were better than those of the autogenous bone graft, suggesting that the group of the AXCB/rhBMP-2 graft achieved a good osteogenic effect. With regard to the AXCB graft without rhBMP-2, the area percentage of bone regeneration was only 14.03 ± 5.02, 28.49 ± 11.35, and 53.90 ± 21.92. Therefore, the osteogenic effect of the AXCB/rhBMP-2 graft was demonstrated to have the best effect. In the group of the AXCB/rhBMP-2 graft, the area percentage of bone regeneration increased, and the implanted materials were gradually degraded and replaced by autogenous bone regeneration over time. We conclude that the AXCB graft soaked with rhBMP-2 showed good osteogenic effect in the repair of bone defects and good biocompatibility. AXCB serves as a good carrier of rhBMP-2, which promotes bone formation.

Bone morphogenetic proteins: a powerful osteoinductive compound with non-negligible side effects and limitations

Healing and regeneration of large bone defects leading to non-unions is a great concern in orthopedic surgery. Since auto- and allografts have limitations, bone tissue engineering and regenerative medicine (TERM) has attempted to solve this issue. In TERM, healing promotive factors are necessary to regulate the several important events during healing. An ideal treatment strategy should provide osteoconduction, osteoinduction, osteogenesis, and osteointegration of the graft or biomaterials within the healing bone. Since many materials have osteoconductive properties, only a few biomaterials have osteoinductive properties which are important for osteogenesis and osteointegration. Bone morphogenetic proteins (BMPs) are potent inductors of the osteogenic and angiogenic activities during bone repair. The BMPs can regulate the production and activity of some growth factors which are necessary for the osteogenesis. Since the introduction of BMP, it has added a valuable tool to the surgeon's possibilities and is most commonly used in bone defects. Despite significant evidences suggesting their potential benefit on bone healing, there are some evidences showing their side effects such as ectopic bone formation, osteolysis and problems related to cost effectiveness. Bone tissue engineering may create a local environment, using the delivery systems, which enables BMPs to carry out their activities and to lower cost and complication rate associated with BMPs. This review represented the most important concepts and evidences regarding the role of BMPs on bone healing and regeneration from basic to clinical application. The major advantages and disadvantages of such biologic compounds together with the BMPs substitutes are also discussed.