Anti-erosion effect of an experimental varnish on eroded dentin

Abstract This in vitro study evaluated the effect of an experimental varnish containing 20% nano-hydroxyapatite (nHAP) associated with 5% stannous chloride (SnCl2) against erosive-abrasive wear on bovine dentin. Samples of bovine cervical dentin were pre-eroded (0.3% citric acid, pH 2.6 for 10 minutes) and randomized into 4 groups (n=10): Control group - experimental varnish without active ingredient (CG); experimental varnish containing 20% nHAP (nHG); experimental varnish containing 5% SnCl2 (24.800 ppm Sn2+) (SnG); experimental varnish containing 20% nHAP associated with 5% SnCl2 (18.300 ppm Sn2+) (nHSnG). After applying the materials, the erosive-abrasive challenges were performed for five days. Erosive dentin loss and analysis of the pattern of dentinal obliteration were performed by 3D confocal laser microscopy. A one-way ANOVA/Bonferroni test was performed to analyze the data (α=0.05). The SnG and nHSnG experimental groups presented more effectiveness in preventing erosive wear when compared to the other groups (p<0.05). There was no statistically significant difference between the SnG and nHSnG groups (p = 0.731) in tooth structure dentin loss. Regarding the amount of open dentinal tubules, the highest amount of obstructed dentinal tubules was demonstrated in SnG and nHSnG (p < 0.05) when compared to the others. Between SnG and nHSnG there was no significant difference (p = 0.952) in the amount of closed dentinal tubules in the dentin. Experimental varnishes containing 5% SnCl2 associated or not with 20% nHAP showed to be a promising strategy in preventing erosive-abrasive wear of dentin. In addition, nHSnG was able to obliterate dentinal tubules.

Resumo Este estudo in vitro avaliou o efeito de um verniz experimental contendo 20% de nano-hidroxiapatita (nHAP) associado a 5% de cloreto estanoso (SnCl2) contra o desgaste erosivo-abrasivo da dentina bovina. As amostras de dentina cervical bovina foram pré-erodificadas (0,3% de ácido cítrico, pH 2,6 durante 10 minutos) e aleatorizadas em 4 grupos (n=10): Grupo controle - verniz experimental sem ingrediente ativo (GC); verniz experimental contendo 20% nHAP (GnH); verniz experimental contendo 5% SnCl2 (24.800 ppm Sn2+) (GSn); verniz experimental contendo 20% nHAP associado a 5% SnCl2 (18.300 ppm Sn2+) (GnHSn). Após a aplicação dos materiais, os desafios erosivo-abrasivos foram realizados durante cinco dias. Perda de dentina erosiva e análise do padrão de obliteração dentinária foram realizadas por microscopia laser confocal 3D. Foi realizado o teste ANOVA/Bonferroni unidireccional para analisar os dados (α=0,05). Os grupos experimentais GSn e GnHSn apresentaram maior eficácia na prevenção do desgaste erosivo quando comparados com os outros grupos (p<0,05). Não houve diferença estatisticamente significativa entre os grupos GSn e GnHSn (p = 0,731) na perda de dentina da estrutura dentária. Relativamente à quantidade de túbulos dentinários abertos, a maior quantidade de túbulos dentinários obstruídos foi demonstrada em GSn e GnHSn (p < 0,05) quando comparada com os outros grupos. Entre GSn e GnHSn, não houve diferença significativa (p = 0,952) na quantidade de túbulos dentinários fechados na dentina. Os vernizes experimentais contendo 5% de SnCl2 associados ou não a 20% de nHAP mostraram ser uma estratégia promissora na prevenção do desgaste erosivo-abrasivo da dentina. Além disso, o GnHSn conseguiu obliterar os túbulos dentinários.

Nano-hydroxyapatite/polyamide 66 composite filling combined with locking plate in the treatment of fibrous dysplasia of femoral bone / 中国组织工程研究

BACKGROUND: Nano-hydroxyapatite/polyamide 66 composite (n-HA/PA66) has good biocompatibility, osteoinduction, osteoconductivity and osteogenesis. It is widely used in clinical fracture healing, spinal fusion, and other bone repair. OBJECTIVE: To observe the effect of n-HA/PA66 filling combined with locking plate in the treatment of fibrous dysplasia of femoral bone. METHODS: From May 2015 to May 2018, 15 patients with fibrous dysplasia of bone were admitted to Xingtai People’s Hospital Affiliated to Hebei Medical University. There were 4 males and 11 females, aged 16-58 years. The lesions were all located in the femur. They were all treated with n-HA/PA66 filling combined with locking plate. The patients were followed up for 18-40 months. Imaging examination (X-ray and CT scan) was carried out to evaluate the bone healing. Musculoskeletal Tumor Society (MSTS) score and Harris score were used to assess the functional recovery of patients after operation. RESULTS AND CONCLUSION: (1) X-ray films showed that there was a clear boundary between the transplanted bone and the host bone immediately after the operation. At 3 months after the operation, the transplanted bone was replaced partly by crawling. At 6 months, new bone formation was obvious. At 9-12 months, new bone formed completely. The transplanted bone was basically catabolized. At 18 months, the new bone was completely integrated with the host bone. The boundary between the new bone and the host bone disappeared. New bone and host bone are connected by direct trabecula. (2) At the last follow-up, CT images showed that the local lesions were eliminated; no recurrence or metastasis occurred; and the grafts healed completely. The G/N ratio was 0.78±0.09. (3) At the last follow-up, 15 patients’ pain all disappeared, MSTS score was 28.1±0.7. Harris score was 94.3. Daily physical activity was restored. (4) n-HA/PA66 composite material has obvious osteogenic effect on the bone defect caused by the removal of fibrous dysplasia. Locking plate fixation can make patients move early and obtain good postoperative function.

Evaluation of color changes of white spot lesions treated with three different treatment approaches: an in-vitro study

ABSTRACT Objective: To qualitatively and quantitatively assess the color changes effect and the color stability of the resin infiltrant on white spot lesions (WSLs), in comparison with nano-hydroxyapatite (nano-HA) toothpaste and microabrasion. Methods: WSLs were artificially created on sixty human premolars enamel surfaces and randomly assigned to equal four groups (n = 15 each): nano-HA toothpaste, microabrasion (Opalusture), resin infiltrant (Icon) treatment, or artificial saliva (control group). The color change (ΔE) of each specimen was measured by dental spectrophotometer (Vita Easyshade) at different time points: baseline, after WSLs' creation, after application of treatments, one month, three and six months after treatments application. Results: The ΔE value did not differ significantly for the four groups at baseline measurement before treatment (p> 0.05). Icon resin infiltrant improved the color of WSLs significantly immediately after its application, giving the lowest ΔE value (3.00 ± 0.59), when compared to other treatments (p< 0.001). There were no significant changes in ΔE (p> 0.05) for all groups during the follow up intervals (one month, three and six months after treatments application). Conclusion: Resin infiltrant can improve the color of WSLs and restore the natural appearance of enamel better than nano-HA toothpaste and microabrasion.

RESUMO Objetivo: avaliar qualitativamente e quantitativamente os efeitos nas mudanças e estabilidade da cor de lesões de mancha branca (LMBs), após tratamento com infiltração de resina, em comparação aos tratamentos com pasta de dentes com nanopartículas de hidroxiapatita (Nano-HA) e com microabrasão. Métodos: As LMBs foram criadas artificialmente em 60 superfícies de esmalte dentário de pré-molares humanos e aleatoriamente divididas em quatro grupos (n=15, cada): pasta de dentes Nano-HA, microabrasão (Opalusture), tratamento com infiltração de resina (Icon) e saliva artificial (grupo controle). A mudança de cor (ΔE) de cada espécime foi aferida com um espectrofotômetro odontológico (Vita Easyshade) em diferentes tempos: início do estudo, após a criação das LMBs, após a aplicação dos tratamentos, um mês, três meses e seis meses após a aplicação dos tratamentos. Resultados: Os valores de ΔE não diferiram significativamente entre os quatro grupos ao início do estudo (p > 0,05). A infiltração com resina Icon melhorou significativamente a coloração das LMBs imediatamente após a sua aplicação, com o menor valor de ΔE (3,00 ± 0,59), quando comparada às outras modalidades de tratamento (p < 0,001). Não houve mudanças significativas nos valores de ΔE (p > 0,05) em qualquer um dos grupos durante os intervalos de acompanhamento (um mês, três meses e seis meses após a aplicação do tratamento). Conclusão: A infiltração de resina é capaz de melhorar a coloração das LMBs e restaurar a aparência natural do esmalte de forma superior à pasta de dentes com Nano-HA e à microabrasão.

In vitro biocompatibility of 3D printed polycaprolactone/nano-hydroxyapatite composite scaffold with bone marrow mesenchymal stem cells / 中国组织工程研究

BACKGROUND: Polycaprolactone/nano-hydroxyapatite composite is a new composite scaffold material prepared based on common bone tissue engineering materials using 3D printing technology. At present, little is reported on the in vitro biocompatibility of the composite material. OBJECTIVE: To investigate the cytocompatibility of 3D printed polycaprolactone/nano-hydroxyapatite composite scaffolds. METHODS: Polycaprolactone and polycaprolactone/nano-hydroxyapatite composite scaffolds were prepared by 3D printing technology to characterize the microstructure, porosity and mechanical properties of the two materials. Rat bone marrow mesenchymal stem cells were inoculated on the surface of the 3D-printed polycaprolactone and polycaprolactone/nano-hydroxyapatite composite scaffolds. Cell proliferation rate was detected by CCK-8 method. Cell growth on the scaffolds was observed by scanning electron microscopy and Live/Dead cell staining. RESULTS AND CONCLUSION: Two kinds of scaffolds had a three-dimensional network and interconnected structure. The fibers were arranged in a regular order and interlaced. There was no gap on the fiber surface, and the fiber spacing and diameter were relatively uniform. There was no significant difference in the porosity between two kinds of scaffolds (P > 0. 05). The elastic modulus of the composite scaffold was higher than that of the simple polycaprolactone scaffold (P < 0. 05). There was no significant difference in cell proliferation between two kinds of scaffolds after 1 day of culture. After 4 and 7 days of culture, cell proliferation on the composite scaffold was significantly faster than that on the simple polycaprolactone scaffold (P < 0. 05). Live/Dead cell staining showed that both polycaprolactone and polycaprolactone/nano-hydroxyapatite composite scaffolds had good cytocompatibility and high cell viability. A larger number of cells adhered to the polycaprolactone/nano-hydroxyapatite composite scaffolds. Scanning electron microscopy showed that cells grew well on two kinds of scaffolds and distributed on the surface and micropores of the scaffold. The secreted extracellular matrix appeared in filaments and surrounded the cells. These findings suggest that the polycaprolactone/nano-hydroxyapatite composite material prepared by 3D printing technology has abundant pores, exhibit good mechanical properties, and have good cytocompatibility and can be used as a scaffold material for tissue engineering.

Characterization of self-assembled bone-like nano-hydroxyapatite/collagen composites / 中国组织工程研究

BACKGROUND: The materials that are similar to natural bone and can be used for repair of bone defects or as tissue engineering material have become the focus of research. OBJECTIVE: To investigate the feasibility of self-assembly of nano-hydroxyapatite collagen composite. METHODS: Collagen was immersed in 0.25% glutaraldehyde solution for 0.5 (group A), 24 (group B) and 72 hours (group C) for cross-linking reaction. In the group D, collagen was immersed in carbodiimide for 4 hours. After cross-linking reaction, collagen in each group was immersed in nano-hydroxyapatite solution for 7 days to prepare bone-like composite materials. The mineral phase analysis, composition, and microstructure of composite materials and natural bone were analyzed. RESULTS AND CONCLUSION: X-ray diffraction analysis: The amorphous diffraction peaks of the composites were slightly higher than those of the natural bone. The amorphous change of the composite was not obvious. With the prolongation of glutaraldehyde cross-linking time, the peak value of the crystal of the composite tended to increase. The amorphous diffraction peaks of the composites crosslinked with carbodiimide were slightly lower than those crosslinked with glutaraldehyde. Fourier transform infrared spectroscopy analysis: The chemical composition of the composites was similar to that of the natural bone, which was composed of collagen and hydroxyapatite, in which PO43-was partly replaced by CO32-ion in hydroxyapatite. Different cross-linking methods had no obvious effects on inorganic phase change of the materials. Scanning electron microscopy: The effects of different collagen cross-linking methods on the morphology of the formed crystals were not significantly different. Collagen fibers intertwined. A large number of fine needle-like crystals deposited on them, clustered, and were uniformly distributed. The crystal was nano-scaled in size. These results suggest that bone-like composite can be self-assessmbled with nano-hydroxyapatite precursor and collagen.

Preparation and mechanical properties of zirconia-based nano-hydroxyapatite functionally graded material / 中国组织工程研究

BACKGROUND: Studies have shown that the nano-hydroxyapatite coating on the surface of zirconia has not only high strength and toughness, but also good biocompatibility. It is an ideal substitute for hard tissue. However, the coating is easy to fall off from the surface of zirconia, which is a fatal defect. OBJECTIVE: To prepare functionally graded bioceramics with pure zirconia as matrix, gradient layer in the middle and nano-hydroxyapatite on the surface by gradient composite technology and to screen the optimal mechanical properties and sintering temperature. METHODS: Using zirconia and nano hydroxyapatite powder as raw materials, ceramic specimens were prepared by the lamination method in powder metallurgy. According to the thickness of zirconia layer, three groups A (40 mm), B (30 mm) and C (20 mm) were designated. Each group was sub-divided into three subgroups 1 (3 layers), 2 (5 layers) and 3 (7 layers). Thus, there were 162 ceramic specimens in nine subgroups. The ceramic specimens were sintered at different temperatures (1 300,1 350,1 400,1 450,1500, and 1 550°C) and then processed into rectangular specimens for mechanical property testing. RESULTS AND CONCLUSION: The zirconia-based nano-hydroxyapatite functionally graded material can be formed by 10 MPa single side vertical pressure. With the increases in the number of gradient layers and sintering temperature, the mechanical properties of the functionally graded bioceremics in each group were enhanced. The functionally graded bioceramics had the optimal mechanical properties when sintering temperature was 1 550°C, the number of gradient layers was 7, and substrate thickness was 40 mm. The optimal mechanical property of the functionally graded bioceramics produced at above parameter was significantly superior to that produced at other eight sets of parameters (P<0.05). According to the optimal gradient design, the zirconia-based nano-hydroxyapatite functionally graded ceramic specimens prepared by high temperature sintering technique have stronger mechanical properties.

Micro-morphology and phase of zirconia-based nano-hydroxyapatite functional gradient biomaterials / 中国组织工程研究

BACKGROUND: The successfully prepared zirconia-based nano-hydroxyapatite functional gradient bioceramics has mechanical properties of strong interlayer bonding, high compressive and shear strength, but its biological properties are yet to be studied. OBJECTIVE: To detect the micro-morphology and phase of the zirconia-based nano-hydroxyapatite functional gradient bioceramics using scanning electron microscope and X-ray diffractometer. METHODS: Cylindrical zirconia-based nano-hydroxyapatite functional gradient bioceramics were longitudinally sectioned into thin-shaped specimens with turbine handpieces. The profile (intersections of layers) was polished with sandpaper. Its surface micro-morphology and layered structure were observed with a scanning electron microscope after spraying gold. The test piece was ground into a powder in an agate mortar and filtered with gauze. Ceramic powder was sieved with smaller particle size for phase analysis with X-ray diffractometer. RESULTS AND CONCLUSION: (1) Scanning electron microscopy showed that the gradient layers were tightly bound. The grain volume was basically uniform. There was a small amount of ZrO2 agglomeration. The closer to the surface layer, the higher the nHA content and the uniform small pores. (2) The X-ray diffractometer detected mainly the tetragonal phase ZrO2 and nHA diffraction peaks, and a small amount of β-TCP, α-TCP, CaZrO3 and a small amount of monoclinic phase ZrO2 crystal. (3) The research results indirectly indicate that the surface layer nHA is firmly bonded to the ZrO2 matrix layer under the transition of the gradient layer. ZrO2 based nHA functional gradient biomaterial is a ceramic material with excellent mechanical and biological properties.

Combination of magnesium ion with mineralized collagen intervenes osteogenic differentiation of mouse preosteoblasts / 中国组织工程研究

BACKGROUND: Preliminary study has shown that the composite materials composed of magnesium-based materials and mineralized collagen have a good supporting effect on repairing the critical defects, which can improve the mechanical strength of mineralized collagen and premature collapse during bone healing to some extent. However, magnesium-based metals degrade fast in chloride-containing solutions (including human body fluids or plasma), and the effects of releasing magnesium ions on the proliferation and differentiation of osteoblasts are unknown. OBJECTIVVE: To investigate the effects of magnesium ion combined with mineralized collagen on osteogenic differentiation of mouse preosteoblasts in vitro. METHODS: Mineralized collagen extracts were prepared from complete medium with magnesium ion concentration of 0, 5, 10, and 20 mmol/L. Mouse preosteoblasts were cultured with four mineralized collagen extracts, respectively, which were divided into mineralized collagen group, and 5, 10 and 20 mmol/L Mg2++mineralized collagen groups. The mouse preosteoblasts cultured in complete medium were used as control group. The cell morphology, proliferation, apoptosis, intracellular microfilament actin, and the activity of alkaline phosphatase and expression level of the osteogenic gene Runx2 after osteogenic differentiation were detected. RESULTS AND CONCLUSION: (1) After 24 hours of culture, the cells in the mineralized collagen group, and 5 and 10 mmol/L Mg2++ mineralized collagen groups adhered well, which showed no significant difference from the blank control group, and the elongated spindle cells with many synapses linked to the adjacent cells were observed. The cells in the 20 mmol/L Mg2++mineralized collagen group showed obvious pyknosis. (2) After 1, 3 and 5 days of culture, the cell viability in the 10 mmol/L Mg2++mineralized collagen group was significantly higher than that in the other four groups (P 0.05). The cell viability in the 20 mmol/L Mg2++mineralized collagen group was significantly lower than that in the mineralized collagen group (P < 0.05). (3) After 3 days of culture, DAPI staining showed that 20 mmol/L Mg2++mineralized collagen group had obvious nuclear disintegration, the other four groups had no obvious nuclear disintegration. (4) After 24 hours of culture, phalloidin staining showed that except the blank control and 20 mmol/L Mg2++mineralized collagen groups, the other three groups showed completely extended cell structure, and clear actin microfilaments, especially the 10 mmol/L Mg2++mineralized collagen group. (5) After 7 days of osteogenic differentiation, except for 20 mmol/L Mg2++mineralized collagen group, the activity of alkaline phosphatase and the expression level of Runx2 gene in the other three groups were significantly higher than those in the blank control group (P < 0.05), and those in the 10 mmol/L Mg2++mineralized collagen group was significantly higher than those in the 5 mmol/L Mg2++mineralized collagen and mineralized collagen groups (P < 0.05). (6) These results suggest that the combination of magnesium ion with mineralized collagen should be applied with appropriate concentration range of magnesium ion (≤ 10 mmol/L).

Bioactivity of the peptide P17-bone morphogenetic protein-2/nano-hydroxyapatite-mineralized collagen composite / 中国组织工程研究

BACKGROUND: A mineralized collagen composite, i.e. nano-hydroxyapatite/collagen (nHAC) has biomimetic three-dimensional structure and good bioactive properties. As a bone tissue engineering material, it is widely used in bone defect repair. A newly designed P17-bone morphogenetic protein-2 (P17-BMP2) has good biocompatibility and osteogenic capacity. Therefore, the composite scaffold material was prepared by combining the new P17-BMP-2 and nHAC, which might be used for the enhancement of osteogenic capacity in the treatment of bone defects. OBJECTIVE: To investigate the bioactivity of the P17-BMP-2/nHAC composite. METHODS: Rabbit bone marrow mesenchymal stem cells were seed on the P17-BMP-2/nHAC composite and nHAC. After 3 and 7 days of culture, the relative expression level of alkaline phosphatase was detected by RT-PCR. The subcutaneous implantation of P17-BMP-2/nHAC (experimental group) and nHAC (control group) into Sprague-Dawley rats was performed. Masson staining was performed for histological analysis at 12 and 35 days of implantation. P17-BMP-2/nHAC (experimental group) and nHAC (control group) were implanted into the white rabbit mandibular box-shaped bone defect, respectively. At 5 and 15 weeks, gross observation and X-ray were performed. The study was approved by the Medical Ethics Committee of China Medical University School & Hospital of Stomatology. RESULTS AND CONCLUSION: (1) The relative expression level of alkaline phosphatase in the P17-BMP-2/nHAC group was significantly higher than that in the nHAC group (P < 0.05). (2) The result of subcutaneous implantation showed that the acute inflammatory response initiated by the P17-BMP-2/nHAC or nHAC was not found. More activated fibroblasts growing into the implants could be found on the sections of P17-BMP-2/nHAC compared to that of nHAC at 35 days after implantation. (3) In the bone defect repair test, gross observation showed that both materials held good defect repair ability, the defect area began to reduce at 5 weeks after implantation, and the defect surface became flat at 15 weeks after implantation. X-ray examination showed that compared with the control group, the defect area was more significantly reduced in the experimental group. (4) These results indicate that P17-BMP-2/nHAC composite scaffold has higher bioactivity and a stronger ability to repair bone defect.

Caracterização físico-química e atividade biológica de um cimento dentário à base de quitosana, nanohidroxiapatita, nanopartículas de óxido de zinco para estimulação de células nervosas de Schwann (HS-SCH-2) / Physical-chemical characterization and biological activity of a dental cement based on chitosan, nano-hydroxyapatite, and zinc oxide nanoparticles for Schwann nervous cell stimulation (hs-sch-2)

Os cimentos dentários e ortopédicos são utilizados amplamente em diversas aplicações clínicas. Novos cimentos vêm sendo propostos visando à preservação ou regeneração tecidual. Contudo, pouco se conhece sobre o papel desses biomateriais na regeneração nervosa. As células mais comumente envolvidas na regeneração nervosa são as células de Schwann (SCs) sendo sua principal função o suporte aos axônios através da liberação de fatores de crescimento e isolamento axonal através da formação da bainha de mielina. Como estratégia da presente pesquisa, foi estudado um cimento à base da quitosana com adição de substâncias que podem atuar sinergicamente na resposta celular nervosa, tais como, as nanopartículas (NPs) de hidroxiapatita e o óxido de zinco, visto que têm propriedades bioativas e biocondutoras, além de promoverem a condução de prolongamento axonal. A doxiciclina (Dox) foi acrescida como antimicrobiano, potente inibidora de metaloproteinases (MMPs) e estimuladora da diferenciação celular no processo de regeneração tecidual. Assim, as propriedades físico-químicas e biológicas do cimento de nano-hidroxiapatita, quitosana, óxido de zinco e doxiciclina foram avaliadas, bem como a capacidade de promover um ambiente favorável para as células nervosas periféricas. Os cimentos foram caracterizados físico-químicamente mediante a determinação do pH, tempo de presa e solubilidade, lixiviação de íons cálcio, liberação controlada de doxiciclina, difração de Raios X, Termogravimetria (TG), espectroscopia Raman, molhabibidade, e testes de atividade biológica, para assim também serem avaliados em contato com células nervosas de Schwann (HS-Sch-2). O cimento apresentou pH neutro (7,0), tempo de presa de 5,7 ± 0,22 minutos, solubilidade menor que 3%, lixiviação de cálcio de 8,14 ± 0,71 mg L-1 após 14 dias, estabilidade térmica e a análise espectroscópica ratificou a presença e diferenciação das estruturas químicas dos componentes do cimento coerentemente com as imagens das análises microscópicas. Além disso, o cimento se mostrou hidrofílico, teve efeito hemolítico baixo (17%), obteve alta citocompabilidade celular em fibroblastos ATCC 3T3 (72%) e ação antimicrobiana. O cimento aumentou significativamente o crescimento das células de Schwann, 48,6% a mais do que o grupo controle (p≤0.05), e maior capacidade metabólica na análise mitótica quando em contato com este material (33%). Pode-se concluir que o cimento proposto à base de quitosana contendo hidroxiapatita e óxido de zinco nanoparticulados com adição de doxiciclina obteve efeito bioativo em células de Schwann promovendo, assim, o crescimento e a atividade mitótica celular, sendo então um biomaterial promissor para estudos de remielinização de nervos periféricos e regeneração nervosa in vivo.

Dental and orthopedic cements are used widely in several clinical applications. New cements have been proposed aimed the tissue preservation or regeneration. Nevertheless, nerve regeneration is not well known. The cells most commonly used in nerve regeneration are Schwann cells (SCs) which represent glial cells in the peripheral nervous system, their main function being supporting axons by releasing growth factors and axonal isolation through the formation of the myelin sheath. As a strategy of this research, chitosan-based cement was studied with the addition of substances that can act synergistically in the nervous cell response, such as the hydroxyapatite and zinc oxide nanoparticles (NPs), since they have bioactive and bioconductive properties; in addition to furthermore, they promote the conduction of axonal prolongation. Doxycycline (Dox) was added as an antimicrobial, a potent inhibitor of MMPs, a stimulator of cell differentiation in the tissue regeneration process. Thus, the physical-chemical and biological properties of nanohydroxyapatite, chitosan, zinc oxide and doxycycline cements were evaluated, as well as the ability to promote a favorable environment for peripheral nerve cells. Blocks of cements were characterized physically and chemically by determining pH, setting time and solubility, calcium ions leaching, controlled release of doxycycline, X-ray diffraction, Thermogravimetry (TG), Raman spectroscopy, wetness, and biological activity tests, so they can also be evaluated in contact with Schwann nerve cells (HS-Sch-2). The cement showed neutral pH (7.0), setting time of 5.7 ± 0.22 minutes, solubility less than 3%, calcium leaching of 8.14 ± 0.71 mg L-1 after 14 days, stability thermal and spectroscopic analysis confirmed the presence and differentiation of the chemical structures of the cement components coherently with the images of the microscopic analysis. In addition, the cement was shown to be hydrophilic, had a low hemolytic effect (17%), and obtained high cell cytocompatibility in ATCC 3T3 fibroblasts (72%) and antimicrobial action. The cement significantly increased the growth of Schwann cells, 48.6% more than the control group (p≤0.05), and greater metabolic capacity in the mitotic analysis when in contact with this material (33%). It can be concluded that the proposed chitosan-based cement containing hydroxyapatite and zinc oxide nanoparticulated with the addition of doxycycline has a bioactive effect in Schwann cells, thus promoting cell growth and mitotic activity, thus being a promising biomaterial for studies of remyelinization of peripheral nerves and nerve regeneration in vivo.

Effect of nano-hydroxyapatite containing desensitizers on dentin bonding performance of self-etch adhesive / 西安交通大学学报(医学版)

Objective: To evaluate the dentinal tubular occlusion of nano-hydroxyapatite (nHAp) containing desensitizers and their influence on the dentin bonding performance of self-etch adhesive. Methods: Mid-coronal dentin specimens were prepared from 48 intact human third molars. They were immersed in 10 g/L of citric acid for 20 s to simulate sensitive teeth, and randomly divided into four groups. The control group received no desensitizing treatment. Three experimental groups were treated with two commercial nHAp containing desensitizing toothpastes (Biorepair and Dontodent) and an experimental pure nHAp paste, respectively. The effect of desensitizers on dentinal tubular occlusion was observed by the field-emission scanning electron microscope (FESEM). Each group was further bonded with Futurabond NR. The micro-tensile bond strength was tested and failure mode distribution was analyzed. Moreover, resin infiltration of the adhesive was evaluated under confocal laser scanning microscopy (CLSM). Results: FESEM revealed that all the desensitizers noticeably occluded the dentinal tubules. After application for 7 days, the penetration depth of desensitizing particles was obviously increased and the extent of occlusion was completer. The micro-tensile bond strength test showed no significant differences in bonding strength among the three desensitization groups and control group (P>0.05). CLSM demonstrated the similar morphology of resin tags was produced in the desensitized groups and control group. Conclusion: Nano-hydroxyapatite containing desensitizers could occlude dentinal tubules effectively. Meanwhile, the application of these nHAp desensitizers has no adverse effect on resin infiltration and dentin bond strength of Futurabond NR self-etch adhesive

Efficacy of fluoride associated with nano-hydroxyapatite in reducing enamel demineralization adjacent to orthodontic brackets: in situ study

ABSTRACT Objective: To assess in situ the effect of fluoride associated with nano-hydroxyapatite for the prevention of demineralization of the enamel adjacent to orthodontic brackets. Material and Methods: Eight volunteers wore palatal devices prepared with 6 bovine enamel blocks (5x5x2 mm) with bonded brackets. The volunteers used the devices in two different moments of 14 days each. During the first 14 days, a product containing fluoride + nano-hydroxyapatite was applied twice (experimental group, GNH, n = 48), and for the other 14 days no prevention product was applied (control group, CG, n = 48). In both groups, along the experiment, the blocks were dripped with 20% sucrose eight times daily. After the experiment, all the specimens were sectioned and examined for lesion depth analysis (µm) under polarized light microscopy, and for enamel longitudinal microhardness (measured under the bracket, at 30 µm and at 130 µm from the margin), at seven different depths (10, 20, 30, 50, 70, 90, and 110 µm). Results: Under polarized light, group GNH presented significantly less demineralization depth ( X ¯= 15.01 µm, SD = 33.65) in relation to CG ( X ¯= 76.43 µm, SD = 83.75). Enamel longitudinal microhardness demonstrated significantly higher microhardness for group GNH when compared to CG. Conclusion: Fluoride + nano-hydroxyapatite can be an alternative preventive procedure for demineralization of the enamel adjacent to orthodontic brackets.

RESUMO Objetivo: avaliar in situ o efeito da nano-hidroxiapatita associada ao fluoreto na prevenção da desmineralização do esmalte adjacente aos braquetes ortodônticos. Material e Métodos: oito voluntários utilizaram aparelhos palatinos preparados com seis blocos de esmalte bovino (5 x 5 x 2 mm) com braquetes colados unidos por um fio de NiTi 0,016" preso por ligaduras elásticas. Os voluntários utilizaram os dispositivos em dois tempos distintos de 14 dias. Durante os primeiros 14 dias, um produto contendo flúor + nano-hidroxiapatita foi aplicado duas vezes (grupo experimental, GNH, n = 48), e nos outros 14 dias não foi aplicado qualquer produto de prevenção (grupo controle, GC, n = 48). Em ambos os grupos, ao longo do experimento, os blocos foram gotejados com sacarose a 20%, 8 vezes ao dia. Após o experimento, todos os espécimes foram seccionados e examinados para análise de profundidade de lesão (µm), sob microscopia de luz polarizada, e para microdureza longitudinal do esmalte do braquete (a 30µm e a 130µm da margem), a 7 profundidades diferentes (10, 20, 30, 50, 70, 90 e 110µm) Resultados: sob luz polarizada, o grupo GNH apresentou significativamente menor profundidade de desmineralização ( X ¯= 15,01µm, D.P. = 33,65) em relação ao GC ( X ¯= 76,43µm, D.P. = 83,75) A microdureza longitudinal do esmalte demonstrou valor significativamente maior para o grupo GNH, quando comparado ao GC. Conclusão: a nano-hidroxiapatita associada ao fluoreto pode ser um procedimento alternativo para a prevenção da desmineralização do esmalte adjacente aos braquetes ortodônticos.

Optical properties of polyvinyl alcohol membrane with n-HAp for bio-medical applications

Composite membrane as a flexible materials have found diverse applications in industrial and biomedical simultaneously, the recent studies have shown intrinsic improvement for membrane properties by inclusion of nanoparticles as a fillers with high portion ratio in inorganic polymers, the combination between two parts polymer and filler is as a result of collection the advantage of two component systems parts together. In this work, samples of polyvinyl alcohol (PVA)-nanoHaydroxyapatite (nHAp) composites were prepared by using casting method. The effects of addition of (nHAp) with different concentration on the optical properties of (PVA- nHAp) composite membrane have been studied by using wavelength range (220-820) nm. The absorption spectra, transmittance spectra, absorption coefficient, energy gap, refractive index, optical conductivity and extinction coefficient have been determined. The results show that the optical constants change with the increase of nHPA concentrations.

Effectiveness of nano-hydroxyapatite/polyamide-66 Cage in interbody fusion for degenerative lumbar scoliosis / 中国修复重建外科杂志

Objective: To explore the effectiveness of nano-hydroxyapatite/polyamide-66 (n-HA/PA66) Cage in interbody fusion for degenerative lumbar scoliosis. Methods: A retrospective analysis was designed and conducted for 43 patients, who underwent posterior decompression and n-HA/PA66 Cage interbody fusion with correction of deformity between January 2013 and June 2016. Eighteen cases were single-level fusion (single-level group) and 25 cases were double-level fusion (double-level group). There was no significant difference in gender, age, body mass index, direction of convex, degree of apical rotation, fusion level, the number of osteoporotic patients, pre-operative intervertebral height of fusion segments, coronal Cobb angle, visual analogue score (VAS), and modified Oswestry Disability Index (ODI) between 2 groups ( P>0.05). The operation time, intraoperative blood loss, postoperative drainage, hospital stay, and complications of the operation were recorded. Modified ODI, VAS score, and MacNab criteria were adopted to assess clinical outcomes. Radiographic indexes, including intervertebral height of fusion segments, coronal Cobb angle, disc insertion depth, and the bone graft fusion rate, were also evaluated. Results: There was no significant difference in operation time, intraoperative blood loss, postoperative drainage, and hospital stay between 2 groups ( P>0.05). All patients were followed up 18-62 months (mean, 30.9 months). Wound complications, postoperative delirium, and Cage retropulsion occurred in 4 cases (2 cases in single-level group, 2 cases in double-level group), 1 case of single-level group, and 1 case of double-level group, respectively. The intervertebral height of fusion segments after operation significantly improved compared with preoperative ones in both groups ( P0.05). The disc insertion depth showed no significant difference between different time points after operation in 2 groups ( P>0.05) and between 2 groups at each time point after operation ( P>0.05). Bony fusion was obtained in all patients at last follow-up. The VAS score and modified ODI after operation in both groups were superior to those before operation ( P0.05). According to the MacNab criteria, the excellent and good rates at last follow-up were 94.4% and 84.0% in single-level group and double-level group, respectively. Conclusion: The n-HA/PA66 Cage can effectively restore and maintain the disc height of fusion segment, normal sequence, and biomechanical stability of the spine, and gain favorable effectivenss for degenerative lumbar scoliosis. And double-level fusion is superior to single-level fusion in maintaining disc height of fusion segment.

A Comparison of the Effects of Silica and Hydroxyapatite Nanoparticles on Poly(ε-caprolactone)-Poly(ethylene glycol)-Poly(ε-caprolactone)/Chitosan Nanofibrous Scaffolds for Bone Tissue Engineering

BACKGROUND: The major challenge of tissue engineering is to develop constructions with suitable properties which would mimic the natural extracellular matrix to induce the proliferation and differentiation of cells. Poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, PCEC), chitosan (CS), nano-silica (n-SiO₂) and nano-hydroxyapatite (n-HA) are biomaterials successfully applied for the preparation of 3D structures appropriate for tissue engineering. METHODS: We evaluated the effect of n-HA and n-SiO₂ incorporated PCEC-CS nanofibers on physical properties and osteogenic differentiation of human dental pulp stem cells (hDPSCs). Fourier transform infrared spectroscopy, field emission scanning electron microscope, transmission electron microscope, thermogravimetric analysis, contact angle and mechanical test were applied to evaluate the physicochemical properties of nanofibers. Cell adhesion and proliferation of hDPSCs and their osteoblastic differentiation on nanofibers were assessed using MTT assay, DAPI staining, alizarin red S staining, and QRT-PCR assay. RESULTS: All the samples demonstrated bead-less morphologies with an average diameter in the range of 190–260 nm. The mechanical test studies showed that scaffolds incorporated with n-HA had a higher tensile strength than ones incorporated with n-SiO₂. While the hydrophilicity of n-SiO₂ incorporated PCEC-CS nanofibers was higher than that of samples enriched with n-HA. Cell adhesion and proliferation studies showed that n-HA incorporated nanofibers were slightly superior to n-SiO₂ incorporated ones. Alizarin red S staining and QRT-PCR analysis confirmed the osteogenic differentiation of hDPSCs on PCEC-CS nanofibers incorporated with n-HA and n-SiO₂. CONCLUSION: Compared to other groups, PCEC-CS nanofibers incorporated with 15 wt% n-HA were able to support more cell adhesion and differentiation, thus are better candidates for bone tissue engineering applications.

A preliminary study on the fabrication of silk fibroin/chitosan/nano-hydroxyapatite osteochondral scaffolds with a gradient pore size structure / 中华老年医学杂志

Objective To explore the feasibility and methods of preparing silk fibroin(SF)/ chitosan(CS)/nano hydroxyapatite(nHA)composite osteochondral scaffolds with a gradient pore size structure.Methods We prepared an SF solution,a CS solution and an nHA suspension,all with a 2％ concentration,and mixed them with equal proportions.The mixture was used to prepare SF/CS/nHA composite osteochondral scaffolds with a pore size gradient through a centrifugal freeze drying and chemical cross linking method.The porosity,hot water loss rate,water swelling rate and mechanical properties of the scaffold were measured,and the dissolution curve and stress strain curve were drawn.The internal structure and morphology of the scaffold were observed by scanning electron microscopy(SEM)and the sizes of pores in the scaffold were measured.Results The porosity of the scaffold was(91.30± 3.35)％;The five week hot water loss rate was(16.57± 3.18)％;And the water swelling rate was (3218.53 ± 84.37)％.Mechanical test results demonstrated a good compression performance of the scaffold.SEM showed that the internal pores of the scaffolds were honeycomb structured with communicating passages;The density of pores gradually increased with decreasing pore sizes from the top to the bottom(pore sizes at four different levels:(141.11± 11.85)μm,(119.94± 9.05)μm,(93.10 ± 14.98) μm,and (79.95 ± 8.65)μm,respectively,F =22.973,P =0.000).Scaffold cytotoxicity test results indicated no significant difference between A values of the extract group and of the negative control group at any time point(t24 h =0.520,P =0.610;t48 h =0.665,P =0.515;t72 h =0.439,P =0.666),and all RGR values were greater than 100％.Conclusions SF/CS/nHA composite osteochondral scaffolds with a gradient pore size structure can be prepared with a centrifugal-freeze drying and chemical cross-linking method.Scaffolds prepared this way have a three-dimensional structure,a gradient pore size structure,high porosity,strong water absorption,suitable degradation rates and good compressive resistance.Besides,the good cell compatibility and low cytotoxicity of the scaffolds satisfy the requirements for osteochondral tissue engineering materials.

Repair effect of nHA-Mg porous composite materials modified by PLGA on jaw bone defect of rabbits / 吉林大学学报(医学版)

Objective:To observe the repair effect of nano hydroxyapatite/magnesium(nHA-Mg)porous composite material modified by poly lactic acid/glycolic acid copolymer(PLGA) on the jaw bone defect of rabbits,and to elucidate the mechanisms preliminary.Methods:The mandibular defect models of 10 mm×5 mm×1 mm in the 18 rabbits were established.Nine rabbits were selected and implanted with nHA-Mg composite materials modified by PLGA in the left as experimental group and the right as blank control group;the other nine were implanted with nHA-Mg in the left as positive control group and the right as blank control group.The rabbits were sacrificed at 4, 8, 12 weeks (respectively 3 of experimental group and positive control group every time)and the mandibular defect areas were intercepted and observed by imaging and histological examination;the sizes of the newborn trabecula area and residual materials in experimental group and positive control group were compared.Results:Compared with positive control group and blank control group, the percentage of newborn trabecula area of the rabbits in experimental group was increased (P0.05).The imaging results showed that the new bone formation can be observed in experimental group and better than positive control group and blank control group.The paraffin section results indicated that there were visible vascular tissue and newborn trabecula,the osteoblasts gathered around the bone trabecula;a lot of pits were located in the bone trabecula, and the pits contained osteocytes in experimental group.As the prolongation of time,thickened newborn trabecula, dense arrangement and trend of converting to lamellar bone were observed in experimental group.The hard tissue section results showed that the remaining amount of materials in experimental group was more than that in positive control group.Conclusion:nHA-Mg porous composite materials modified by PLGA can effectively reduce the rate of degradation in the body, promote osteogenesis and guide the bone regeneration.

The osteointergration and osteoinduction of titanium implant with nHA/BG gradient coating in rabbits / 实用口腔医学杂志

Objective: To investigate the osteointegration and osteoinduction of nano hydroxyapatite/bioglass ( nHA/BG ) gradient nanofilm on the surface of titanium ( Ti) prepared by hypotherm sintering and plastic deformation. Methods:Hypotherm sintering was used to produce nHA/BG gradient coating followed by soaking in the simulated body fluid. Ti implants with gradient coatings were planted in femoral condyles at one side of 12 New Zealand rabbits and the untreated Ti implants were planted at the other side as the controls. 1, 3 and 6 months after implantation, the animals were sacrificed after X-ray examination and the tissues around the implants from the 3 month group were used for the preparation of hard tissue section and ground section. New bone formation was observed by tetracycline fluorescence staining. Von Gieson staining was used to observe the osteointegration at the interface between bone and im-plant. Results:The gradient coatings were porous and composed of irregular rod-like nano-HA crystals. Animal study showed well es-tablished osteointegration between the gradient coating and more novel bone was found around the implants with gradient coatings. Conclusion:Osteointegration and ostioinduction of Ti implant can be enhanced by nanostructured surface with gradient coatings of nHA/BG.

Enhancement of Osseointegration of Artificial Ligament by Nano-Hydroxyapatite and Bone Morphogenic Protein-2 into the Rabbit Femur

The MTT assay showed that the cell proliferation on hydroxyapatite (HAp) and HAp/bone morphogenic protein (BMP) coated group was better than the control and BMP coated groups at 5 days. And after 7 days of culture, the mRNA expression levels of type I collagen, osteonectin, osteopontin, bonesialoprotein, BMP-2, alkaline phosphatase (ALP) and Runx-2 in the HAp/BMP coated group were significantly higher than the other groups. Also, in this group showed the most significant induction of osteogenic gene expression compared to mesenchymal stem cells (MSCs) grown on the other groups. In addition, the cells in the HAp/BMP coated group delivered higher levels of ALP than the other three groups. Also, silk scaffolds were implanted as artificial ligaments in knees of rabbits, and they were harvested 1 and 3 months after implantation. On gross examination, HE staining showed that new bone tissue formation was more observed in the HAp/BMP coated group 3 weeks postoperatively. And masson staining showed that in the HAp/BMP coated group, the silk fibers were encircled by osteoblast, chondrocyte, and collagen. Furthermore, the analysis showed that the width of the graft-bone interface in the HAp and HAp/BMP coated group was narrower than that in the other two groups 3 weeks postoperatively. So, it is concluded that BMP incorporated HAp coated silk scaffold can be enhanced osseointegration and osteogenesis in bone tunnel. As a result, these experimental designs have been demonstrated to be effective in the acceleration of graft-to-bone healing by increasing new bone or fibrocartilage formation at the interface between graft and bone.

Comparative evaluation of shear bond strength of nano‑hydroxyapatite incorporated glass ionomer cement and conventional glass ionomer cement on dense synthetic hydroxyapatite disk: An in vitro study.

Aim: The aim was to evaluate and compare the shear bond strength of nano‑hydroxyapatite (Nano‑HAp) incorporated and conventional glass ionomer cement (GIC). Materials and Methods: Nano‑HAp GIC was prepared by replacing 8 wt% of GIC powder with nano‑HAp powder. Twenty‑six HAp disks were used as substrate for bonding and divided into two equal groups. Before bonding the HAp disk was prepared by silicon carbide (no. 2500) followed by 10% polyacrylic acid conditioning. The standardized samples were prepared using split teflon mold on customized bonding jig so as to adhere testing materials to pretreated HAp disk. These samples were stored in distilled water for 24 h at 37°C before bond strength testing. Results: The descriptive statistical analysis and independent samples t‑test were used. The nano‑HAp incorporated and conventional GIC had the mean shear bond strength of 3.28 ± 0.89 MPa and 5.25 ± 0.88 MPa, respectively. Nano‑HAp incorporated GIC had lower shear bond strength with very high level of significance (P < 0.001). The nano‑HAp incorporated GIC showed mainly mixed type of failure whereas conventional GIC showed mainly a cohesive failure. Conclusion: The lower shear bond strength of nano‑HAp incorporate GIC revealed that the addition of nano‑HAp interfered with the bonding ability of GIC to the substrate interface, but the mixed type of failure in nano‑HAp incorporated GIC suggests that it increases the strength of the matrix. However, the role of nano‑size particles on the micro‑size particles of GIC for the bonding mechanism and the ratio and proportions of nano‑HAp to the GIC needs further elucidation.