Comparison of dynamic mechanical properties of dentin between deciduous and permanent teeth.

Purpose: Even though differences between deciduous and permanent dentin have been widely studied, their dynamic mechanical behavior has never been compared. The objective of the present study was to quantify the differences between deciduous and permanent dentin under cyclic mechanical loading, which is similar to masticatory stress.Materials and Methods: Deciduous and permanent teeth, respectively from children (9 ~ 12 years old) and young people (18 ~ 25 years old), were wet-sectioned perpendicular to the longitudinal axis and the central specimens of coronal dentin were evaluated by nanoscopic dynamic mechanical analysis (nanoDMA).Results: The average storage, loss, and complex moduli, as well as the hardness of deciduous dentin were significantly (p < 0.05) lower than those of permanent dentin. Moreover, the tan δ value of permanent dentin was significantly (p < 0.05) lower than that of deciduous dentin across the loading frequency range, indicating that viscoelastic behavior and loss of elastic energy were significantly reduced in the stiffer permanent dentin. All the nanoDMA responses showed a significant influence of the dynamic loading frequency (p < 0.05): Both deciduous and permanent dentin showed reduced viscoelasticty with increased loading frequencies.Conclusions: Compared with deciduous dentin, permanent dentin exhibits higher stiffness with reduced energy loss during deformation, and therefore superior mechanical characteristics for the mastication process.

Clinical efficacy of mineralized collagen (MC) versus anorganic bovine bone (Bio-Oss) for immediate implant placement in esthetic area: a single-center retrospective study.

BACKGROUND: The purpose of this retrospective study was to evaluate the clinical efficacy of mineralized collagen (MC) versus anorganic bovine bone (Bio-Oss) for immediate implant placement in esthetic area. METHODS: Medical records of Department of Oral and Maxillofacial Surgery of Shandong Provincial Hospital were screened for patients who had been treated with immediate implant implantation in the esthetic area using either MC (Allgens®, Beijing Allgens Medical Science and Technology Co., Ltd., China) or Bio-Oss (Bio-Oss®, Geistlich Biomaterials, Wolhusen, Switzerland), between January 2018 and December 2019. All patients fulfilling the in-/exclusion criteria and following followed for a minimum period of 1 year after surgery were enrolled into the presented study. Implant survival rate, radiographic, esthetic and patient satisfactory evaluations were performed. RESULTS: Altogether, 70 patients were included in the study; a total of 80 implants were inserted. All implants had good initial stability. The survival rate of implants was 100% at 1-year follow-up. The differences in horizontal and vertical bone loss between the MC group (0.72 ± 0.26 mm, 1.62 ± 0.84 mm) and the Bio-Oss group (0.70 ± 0.52 mm, 1.57 ± 0.88 mm) were no significant difference statistically no significant 6 months after permanent restoration. Similar results occurred at 12 months after permanent restoration functional loaded. Clinical acceptability defined by pink esthetic score (PES) ≥ 6 (6.07 ± 1.62 vs. 6.13 ± 1.41) was not significantly different between groups. Patient satisfaction estimated by visual analog scale (VAS) was similar (8.56 ± 1.12 vs. 8.27 ± 1.44), and the difference was no significant difference between the two groups. CONCLUSIONS: The biomimetic MC showed a similar behaviour as Bio-Oss not only in its dimensional tissues changes but also in clinical acceptability and patient satisfaction. Within the limitations of this study, these cases show that MC could be considered as an alternative bone graft in IIP.

Comparison of rabbit rib defect regeneration with and without graft.

Rib segment, as one of the most widely used autologous boneresources for bone repair, is commonly isolated with an empty left in the defect. Although defective rib repair is thought to be unnecessary traditionally, it's of vital importance actually to promote rib regeneration for patients with better postoperative recovery and higher life quality. Comparative investigations on rabbit rib bone regeneration with and without graft were reported in this article. A segmental defect was performed on the 8th rib of 4-month-old male New Zealand rabbits. The mineralized collagen bone graft (MC) was implanted into the defect and evaluated for up to 12 weeks. The rib bone repair was investigated by using X-ray at 4, 8 and 12 weeks and histological examinations at 12 weeks after surgery, which showed a higher bone remodeling activity in the groups with MC implantation in comparison with blank control group, especially at the early stage of remodeling.

Fabrication of Antimicrobial Peptide-Loaded PLGA/Chitosan Composite Microspheres for Long-Acting Bacterial Resistance.

An antimicrobial decapeptide, KSL-W (KKVVFWVKFK-CONH2), which could maintain stable antimicrobial activity in saliva, has therefore been widely used to inhibit biofilm formation on teeth and prevent the growth of oral microorganisms for related infectious diseases treatment. In order to control the release of KSL-W for long-term bacterial resistance, KSL-W-loaded PLGA/chitosan composite microspheres (KSL/PLGA/CS MSs) were prepared by electrospraying and combined crosslinking-emulsion methods. Different formulations of microspheres were characterized as to surface morphology, size distribution, encapsulation efficiency, in vitro drug release, and antimicrobial activity. Antibacterial experiment demonstrated the prolonged antimicrobial and inhibitory effects of KSL/PLGA/CS MSs on oral bacteria. Moreover, the cell proliferation assay proved that the released KSL-W antibacterial dosage had no cytotoxicity to the growth of osteoblast MC3T3-E1. Thus, our study suggested that the KSL-W-loaded PLGA/CS composite microspheres may have potentially therapeutic applications as an effective drug delivery system in the treatment of oral infectious diseases such as periodontitis and periodontitis, and also within bone graft substitutes for alveolar bone augmentation.

Rib Composite Flap With Intercostal Nerve and Internal Thoracic Vessels for Mandibular Reconstruction.

PURPOSE: The purpose of this study was to present the outcome and discuss the feasibility of rib composite flap with intercostal nerve and internal thoracic vessels for reconstructing mandibular defect. METHODS: Rib composite flaps have been used in 82 patients for reconstructing benign tumor-caused large mandibular defects: 66 of the 82 patients were reconstructed using rib composite flap with intercostal nerve and internal thoracic vessels, whereas the other 16 patients were reconstructed using rib composite flap with internal thoracic vessels, without intercostal nerve. After operation, clinical observation, imageological examination, and sensory detection were used to evaluate the effect of reconstruction. RESULTS: All rib composite flaps with intercostal nerve and internal thoracic vessels were successfully harvested and transplanted. Both immediate and long-term examination showed good appearance reconstruction. All followed-up patients conveyed good satisfaction degree with function and appearance reconstruction. Postoperative panoramic x-ray examination showed new bone formation between the transplanted rib and mandibular stump. Good recoveries of mandibular nerve sensory were observed when followed up after reconstruction surgery. CONCLUSIONS: Rib composite flap with intercostal nerve and internal thoracic vessels could be a promising method for reconstruction of mandibular defects.

[Preparation and Property Investigation of Vancomycin Loaded Calcium Sulfate Hemihydrate/Silk Fibroin Microsphere Artificial Bone Composites with Different Concentration].

With silk fibroin and vancomycin(VCM)as carrier and drug model,respectively,we prepared silk fibroin microspheres(SFM)with different concentration using the water-in-oil emulsion solvent diffusion method.We further developed VCM loaded calcium sulfate hemihydrates(CSH)/SFM artificial bone composites.In this study,surface morphology of the materials was observed using scanning electron microscope(SEM).Structure of the materials was studied with Fourier transform infrared spectroscopy(FTIR).Antibacterial activity of the materials was validated with the inhibition zone test.Drug release property of materials was evaluated using ultraviolet/visible spectrophotometry.Mechanical property of the materials was tested using computer-controlled electronic universal testing machine.The results showed that silk fibroin concentration had no significant effect on molecular conformation and antibacterial property of the SFM.The average diameter of SFM increased and the release rate decreased gradually as the silk fibroin concentration increased.The release rate decreased and the compressive fracture work increased as the silk fibroin concentration increased when adding SFM to CSH.This composite had partly corrected the disadvantages of CSH including the high brittleness and initial burst release.The research would have a good application foreground in the clinical treatment of infectious bone defect.

Engineered pre-dentin with well-aligned hierarchical mineralized collagen fibril bundles promote bio-root regeneration.

Stem cell-mediated bio-root regeneration is an alternative tooth replacement strategy; however, physiologically functional bio-root regeneration with distinctive dentin structure remains challenging. In this study, the distinct arrangements of collagen fibril bundles were identified that account for hierarchical structural differences between dentin, cementum, and alveolar bone. Thus, an "engineered pre-dentin" was fabricated, which was a dentin hierarchical structure mimicking collagen (MC) scaffold, with well-aligned hierarchical mineralized collagen fibril bundles. The results revealed that it has a stronger effect on promoting biological root regeneration in nude mice and miniature pigs with dental pulp stem cell (DPSC) and periodontal ligament stem cell (PDLSC) sheets compared to hydroxyapatite tricalcium phosphate (HA/TCP). The success rate in the MC group was also higher than that in the HA/TCP group (67% and 33%, respectively). In conclusion, the hierarchical dentin-mimicking scaffold can enhance the regeneration of bio-roots, which provides a promising strategy for tooth regeneration.

[The expression level of MMP-2 and collagen of hydroxyapatite modified titanium for keratoprosthesis in the corneal stroma of rabbits].

OBJECTIVE: To investigate the expression level of metalloproteinases-2(MMP-2) and Collagen in a hydroxyapatite surfaced-modified of three Pan type titanium keratoprosthesis after that implanted into the corneal stroma of rabbits, further evaluate its biological compatibility. METHODS: Experimental study. Twenty-four New Zealand white rabbits, 2.0-2.5 kg, were respectively divided into three groups. Surgery was performed in right eye of all animals. skirt of HA-Ti and Ti were respectively inserted into the corneal stroma of rabbit of experimental group A and group B; only a sack was made without implantation in control group C . Cornea edema and corneal neovascularization were observed at scheduled times after operation; animals were sacrificed 2, 4 and 16 weeks after operation and their cornea was removed and examined under light microscopy; the surface of skirt was observed under scanning electron microscope. RESULTS: During the study period, all skirts were stable without infected, dissolved and excluded. Different degree of cornea edema and neovascularization was revealed after surgery. MMP-2 were absent in the normal corneal matrix. The expression level of MMP-2 in group A was higher than group C at all time points (F = 6.083, P < 0.05), and was increased than group B at 4th (F = 47.074, P < 0.01), and was increased than group C at 16th weeks too (F = 6.079, P < 0.05) . Corneal organization has a large green 4 weeks type III collagen and yellow red type I collagen, 16 weeks corneal mainly for bright red when within the collagen type I, still have a small amount of collagen type III. CONCLUSIONS: Rabbit cornea implanted HA-Ti skirts cause MMP-2 activation, continuous high expression didn't cause the cornea to dissolve; Collagen -III turned into collagen-I gradually in the extracellular matrix around the skirts. Hydroxyapatite modified titanium for Keratoprosthesis promoted the corneal neovascularization and improve the interfacial bio integration of skirt and host cornea.

Transdifferentiation of human adipose-derived stem cells into urothelial cells: potential for urinary tract tissue engineering.

Autologous urothelial cells (UCs) provide a cell source for urinary tissue engineering because they can be used safely due to their lack of immunogenicity. However, these cells cannot be harvested under the following circumstances: malignancy, infection and organ loss, etc. Human adipose-derived stem cells (HADSCs) possess the traits of high differentiation potential and ease of isolation, representing a promising resource for tissue engineering and regenerative medicine. Nevertheless, HADSCs have been poorly investigated in urology and the optimal approaches to induce HADSCs into urothelium are still under investigation. In this study, we hypothesized that the change of microenvironment by a conditioned medium was essential for the transdifferentiation of HADSCs into UCs. We then used a conditioned medium derived from urothelium to alternate the microenvironment of HADSCs. After 14 days of culture in a conditioned medium, about 25-50% HADSCs changed their morphology into polygonal epithelium-like shapes. In addition, these cells expressed up-regulating of urothelial lineage-specific markers (uroplakin 2and cytokeratin-18) and down-regulating of mesenchymal marker (vimentin) in RNA and protein level, respectively, which confirmed that HADSCs were induced into urothelial lineage cells. We also measured the growth factors in the conditioned medium in order to analyze the molecular mechanisms regulating transdifferentiation. We observed that the expression levels of PDGF-BB and VEGF were significantly higher than those of the control group after 14 days induction, suggesting they were abundantly secreted into the medium during the culturing period. In conclusion, HADSCs showed in vitro the upregulation of markers for differentiation towards urothelial cells by culturing in an urothelial-conditioned medium, which provides an alternative cell source for potential use in urinary tract tissue engineering.

Autologous urothelial cells transplantation onto a prefabricated capsular stent for tissue engineered ureteral reconstruction.

In this study, we have fabricated an artificial ureter by transplantation of in vitro-expanded urothelial cells onto an in vivo-prefabricated capsular stent using tissue engineering methods. Spiral poly (L-lactic acid) (PLLA) stents were transplanted into the subcutaneous of Wistar rats for a period of 1, 2 or 3 weeks to induce the formation of connective tissue capsules on their surfaces. The capsular PLLA stents were then decellularized and further recellularized with bladder epithelial cells to fabricate artificial ureters. The results showed that the entrapped cells in all capsules remained continuously proliferation and lined up in continuous layers. In addition, the urothelial cells on the capsular stents with an embedding period of 2 or 3 weeks showed higher proliferative viability compared with the cells on the stents with an embedding time of 1 week (P < 0.05). The results of the study indicated that the prefabricated capsular stents could serve as alternative cell carriers for tissue engineered ureters, especially with embedding time from 2 to 3 weeks.

[Promoting of angiogenesis and osteogenesis in radial critical bone defect regions of rabbits with nano-hydroxyapatite/collagen/PLA scaffolds plus endothelial progenitor cells].

OBJECTIVE: To explore the roles of nano-hydroxyapatite/collagen/PLA (nHAC/PLA) plus endothelial progenitor cells (EPCs) in repairing segmental bone defects of rabbit radius and enhancing angiogenesis and new bone formation. METHODS: EPCs isolated from New Zealand white rabbit bone marrow were cultured, identified and seeded into nHAC/PLA scaffolds. And the growth of EPCs in scaffolds was observed under scanning electron microscopy (SEM). Thirty-six were randomly divided into 3 groups to establish segmental bone defect models in radii. Two groups were implanted with EPCs/scaffolds constructs (group A, n = 16) and scaffolds alone (group B, n = 16) respectively. The remaining four rabbits were used as negative control (group C) and nothing was implanted. Animals were sacrificed at different timepoints and radii harvested to undergo radiological examination, histological examination and microvessle density test. RESULTS: These cells isolated from bone marrow were confirmed as EPCs. SEM showed that EPCs attached to the nHAC/PLA scaffolds, grew and proliferated well. Animal experiments revealed that radiological scores (5w: 2.25 ± 0.50 vs 1.00 ± 0.00; 10w: 2.75 ± 0.50 vs 1.75 ± 0.50; 15w: 4.25 ± 0.50 vs 3.0 ± 0.0; each P < 0.05), percentage of new bone formation area in bone defect regions (5w: 29.0% ± 3.5% vs 8.1% ± 0.8%; 10w: 63.4% ± 5.5% vs 16.6% ± 1.3%; 15w: 96.0% ± 4.3% vs 34.0% ± 6.6%; each P < 0.05) and microvessel density (2w: 13.5 ± 0.9 vs 4.3 ± 1.0; 5w:9.8 ± 0.7 vs 4.8 ± 0.3; 10w: 7.0 ± 0.4 vs 4.5 ± 0.4; each P < 0.05) in group A were significantly higher than those in group B. No new bone formation occurred in group C. CONCLUSION: The composite structure of EPCs-nHAC/PLA can enhance angiogenesis and new bone formation in segmental bone defects in rabbit radii. It may become a potential candidate of promoting revascularization of tissue engineering bone and repairing large bone defects.

[Expression of matrix metalloproteinases and inhibitor on the cornea tissue in rabbit after implantation of modified titanium skirt for keratoprosthesis].

OBJECTIVES: To investigate the expression of matrix metalloproteinase-2 (MMP-2) and Tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) in rabbit corneas implanted with modified titanium skirt of keratoprosthesis in order to explore the potential roles. METHODS: A total of 20 New Zealand white rabbits with corneal alkali burn in right eye rabbit corneas were divided into three groups. There were 6 animals in each group. Skirt of hydroxyapatite/Sandblast-Titanium and Sandblast-Titanium were inserted into the corneal stroma of rabbits in group A and group B. The group C did not insert skirt as surgical control.2 rabbits were as normal control D group. A total of 20 New Zealand white rabbits were divided into four groups with the same way. The expression of MMP-2 and TIMP-2 was determined by immunohistochemistry at 1 month, 3 months. The expression of MMP-2 and TIMP-2 mRNA level was determined by real time-polymerase chain reaction, and its protein level was determined by western blot. The optical cylinder was implanted to rabbit corneas, which were implanted with modified titanium skirt after 3 months. RESULTS: There was one case of corneal dissolution being found in group F. MMP-2 and TIMP-2 immunoreactivities were expressed in the normal corneas, predominantly in the corneal epithelium. After injury, immunoreactivities of both MMP-2 and TIMP-2 were increased notably in the healing corneal epithelium, infiltrating inflammatory cells, stromal fibroblasts and in growing vascular endothelial cells. The expression of MMP-2 was lower in group A and E than that in group B and F after 1 month and 3 months (t = 12.05, 2.93, 12.006, 3.781, P < 0.05). The Western blot revealed no significant differences of MMP-2 mRNA between group 3 months and 2 weeks (t = 2.104, P > 0.05); MMP-2 immunoreactivities were absent or lowly expressed predominantly in the corneal epithelium of normal corneas. The expression of MMP-2, TIMP-2 mRNA level was parallel that of protein level. CONCLUSIONS: The expression of MMP-2 was lower in the corneal tissue sections of HA/SB-Ti skirt inserted eyes than that in the tissue sections of SB-Ti skirt inserted eyes. The studies of MMP-2, TIMP-2 can provide a new way to prevent the incidence of corneal dissolving after surgery for keratoprosthesis.

LBL assembly of Ag@Ti3C2TXand chitosan on PLLA substrate to enhance antibacterial and biocompatibility.

Poly L-lactic acid (PLLA) is a non-toxic, biocompatible degradable polymer material with excellent mechanical properties after moulding. However, it faces challenges in the use of biomedical materials because of its intolerance to bacteria. Here, we use an easy-to-operate method to prepare a composite multilayer membrane: PLLA membrane was used as substrates to assemble positively charged chitosan and negatively charged Ag@MXene on the surface using the layer-by-layer (LBL) method. The assembly process was detected by fluorescein isothiocyanate-labelled chitosan and the thickness of the coating multilayer was also detected as 210.0 ± 12.1 nm for P-M membrane and 460.5 ± 26.5 nm for P-Ag@M membrane. The surface self-assembled multilayers exhibited 91.27% and 96.11% growth inhibition ratio againstEscherichia coliandStaphylococcus aureusstrains under 808 nm near-infrared laser radiation with a synergistic photothermal antibacterial effect. Furthermore, best biocompatibility of P-M and P-Ag@M membranes compare to PLLA membrane motivated us to further explore its application in biomedical materials.

Introduction to biodegradable polylactic acid ureteral stent application for treatment of ureteral war injury.

OBJECTIVE: • To study the operability and effectiveness of a biodegradable ureteral stent for clinical treatment of ureteral war injury using a canine model. MATERIALS AND METHODS: • A device was designed and employed to generate firearm fragment wounds in unilateral ureters (on randomly chosen sides) of nine beagles (Group A). The wounded ureters were then debrided and sutured. • Intravenous pyelography (IVP) and radioactive renography were performed 40, 80 and 120 days postoperatively. In Group B, firearm fragment wounds were made to the bilateral ureters in nine beagles. A polylactic acid stent was placed unilaterally (on a randomly chosen side) whereas the ureter on the other side was debrided and sutured without stenting. • Both IVP and radioactive renography were performed 40, 80 and 120 days postoperatively. The operability and effectiveness of the biodegradable ureteral stent were studied thereafter. RESULTS: • In Group A, hydronephrosis and hydroureter occurred and worsened postoperatively on the wounded sides in all nine beagles. The ratio of the renal partial concentration indices (RPCI) between the kidneys (unwounded side : wounded side) increased. • The ratio of the kidney washout half-time between the kidneys (unwounded side : wounded side) decreased. In Group B, neither hydronephrosis nor hydroureter was found postoperatively in the stented ureters but both occurred in the unstented ureters in all nine beagles. • The ratio of RPCI between kidneys (stented side : unstented side) increased whereas the kidney washout half-time ratio between the stented and unstented sides decreased. Differences were significant. CONCLUSION: • In Group A, the new canine model for firearm fragment wounds was tested and proved to be operable and effective. In Group B, hydronephrosis and hydroureter were effectively prevented in ureters by biodegradable stent placement compared with the non-stented ureters where hydronephrosis and hydroureter occurred. The renal concentration capacity was effectively protected and the half-time of kidney washout was shortened.

The clinical results of treating Kummell's disease with mineralized collagen modified polymethyl methacrylate.

To investigate the clinical results of treating Kummell's Disease by using mineralized collagen modified polymethyl methacrylate bone cement, 23 cases (23 vertebras) who sustained Kummell's Disease treated with mineralized collagen modified polymethyl methacrylate bone cement from July 2017 to February 2019 were reviewed retrospectively. The visual analogue scale, vertebral body height, Cobb angle, CT values pre-operation and post-operation as well as incidence of complications were observed. All the patients were successfully followed up with an average period of 11.3 months (ranging from 6 to 12 months). The patients could ambulate on the second day after the operation. The visual analogue scale scores significantly decreased from two days after the operation to the last follow-up compared with that before the operation (p < 0.05); the average vertebral height and local Cobb angle had significant recovery (p < 0.05); the CT value of the treated vertebra significantly increased compared with that before the operation (p < 0.05). Bone cement leakage occurred in one case, anterior edge leakage occurred in one case, and no clinical symptoms caused by bone cement leakage occurred. No re-fracture of the treated vertebral body or adjacent vertebral bodies were observed in the follow-ups. With good osteogenic activity and degradable absorption characteristics, mineralized collagen was compounded with the existing polymethyl methacrylate bone cement to reduce its strength in the vertebral body and enhance biocompatibility, the incidence of adjacent vertebral fractures and re-fractures within the injured vertebrae is significantly reduced, and good clinical results are obtained, which is worthy of popularization.

Modified poly(methyl methacrylate) bone cement in the treatment of Kümmell disease.

Kümmell disease (KD) causes serious vertebral body collapse in patients. However, only a few case reports have been conducted and the number of patients with KD investigated was limited. Additionally, the frequently used poly(methyl methacrylate) (PMMA) bone cement for KD is limited by excessive modulus and poor biocompatibility. Herein, we aimed to modify PMMA bone cement with mineralized collagen (MC), and compare the clinical effects, image performance and finite element analysis between the modified bone cement and PMMA bone cement for the treatment of phase I and II KD. Thirty-nine KD patients treated with PMMA bone cement and 40 KD patients treated with MC-modified PMMA bone cement from June 2015 to March 2017 were retrospectively analyzed. The surgical procedure, intraoperative blood loss, hospital stay and complications were compared between different groups. Visual analog scale, Oswestry disability index, anterior vertebral height, posterior vertebral height, computed tomography value, adjacent vertebral re-fracture, Cobb angle and wedge-shaped correction angle were evaluated. Additionally, the representative sample was selected for finite element analysis. We found that the MC-modified PMMA bone cement could achieve the same effect as that of PMMA bone cement and was associated with better vertebral height restoration in the long term.

Inflammation and immunity gene expression profiling of macrophages on mineralized collagen.

Mineralized collagen (MC) is a biomaterial that is commonly used in the treatment of bone defects. However, the inflammatory response after biomaterial implantation is a recurrent problem that requires urgent attention. Our previous studies on MC-macrophage interactions were descriptive but we did not perform an in-depth analysis on a genetic level to investigate the underlying mechanisms. In this study, we cultured RAW264.7 cells on MC or collagen and examined the proliferation of the macrophages by Cell Counting Kit-8 assay. We sequenced the RNA of the cultured cells to discover differential gene expression patterns and found that a total of 1183 genes were differentially expressed between the MC- and collagen-cultured groups, of which 396 genes were upregulated and 787 were downregulated. Gene ontology analysis revealed that biological processes in MC-cultured cells, such as inflammation and innate immunity, were downregulated; whereas nucleosome assembly, megakaryocyte differentiation, and chromatin assembly were upregulated. We identified several pathways associated with immunity that were significantly enriched using the Kyoto Encyclopedia of Genes and Genomes. Furthermore, we validated the differentially expressed genes from RNA sequencing by quantitative real-time polymerase chain reaction. This study provides insight into the macrophage phenotype based on the microenvironment, which is the foundation for the clinical application of MC-based interventions.

Corrigendum to: Enhancement of BMP-2 and VEGF Carried by Mineralized Collagen for Mandibular Bone Regeneration.

[This corrects the article DOI: 10.1093/rb/rbaa022.].

Preparation recombination human-like collagen/fibroin scaffold and promoting the cell compatibility with osteoblasts.

On this basis, a novel recombinant human-like collagen (RHLC)/silk fibroin scaffold material with high porosity and controllable aperture was prepared. The compatibility of osteoblasts (OB) with the blends was tested in vitro. The morphology, adhesion and growth of scaffold cells were observed by scanning electron microscope and laser confocal microscope. Extensive measurements, including 3-[4, 5-dimethylthiazole-2-acyl]-2, 5-diphenyl tetrabrominate assays, intracellular total protein content, and alkaline phosphatase activity assays were performed after 7 days of culture. Survival and protein content increased in RHLC/fibroin stents. LSCM and SEM results confirmed that the cells grew better in the mixed scaffolds than in the pure silk scaffolds, and showed that the cells were easy to adhere and diffuse in the RHLC/silk scaffolds. RHLC/silk fibroin scaffolds are promising biomaterials for bone tissue engineering.

The mechanical anisotropy on a longitudinal section of human enamel studied by nanoindentation.

Nanoindentation has been widely used for probing the mechanical properties of tooth, especially for characterizing its complex hierarchical structures. Previous studies have confirmed the anisotropic mechanical behaviors caused by the alternated orientations of enamel rods and the alignment of fibril-like hydroxyapatite crystals, but the longitudinal section of enamel, which was composed of parallel-arranged rods, was regarded as a homogeneous continuum as always. In this study, nanoindentation combined with SEM was carried out with the indenter rotating on the longitudinal section of enamel to evaluate the relativity between the nano-mechanical properties and the orientation of indentation impressions. It has been shown that the enamel presented different elastic modulus and hardness with different angles of indenter on its longitudinal section, and its anisotropy was also confirmed by the remarkable asymmetric morphologies of impressions. We observed that the parallel arrangement of crystal fibrils and enamel rods might trigger the expansion of the micro-cracks in preferred orientation, and result in scalene triangle indentation impressions, altering contact areas as well as inconsistent mechanical behaviors. Consequently, it is considered that the longitudinal sections of enamel should be modeled as anisotropic.