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.

Physicomechanical Properties of Resin-Based Pit and Fissure Sealants Reinforced with Rice Husk Derived Nano Silica and Nanohydroxyapatite

@#Resin-based pit fissure sealants (RBS) are used to prevent occlusal caries in children. The success of RBS in preventing dental caries is largely influenced by its retention on the tooth surface, which is also affected by its physicomechanical properties. The physicomechanical properties of RBS can be enhanced through the addition of fillers. With the advent of nanofillers, the physicomechanical properties were improved without altering RBS flowability. The present study developed an RBS with a 70 wt% resin matrix and 30 wt% nanofillers. The resin matrix consisted of urethane dimethacrylate (55 wt%), triethylene glycol dimethacrylate (45 wt%), camphoroquinone (0.3 wt%), and 2-(dimethylamino) ethyl methacrylate (0.7 wt%). Silane-treated rice husk-derived nanosilica (20 wt%) and nanohydroxyapatite (10 wt%) were added as fillers. Clinpro, Fissurit FX, and an unfilled sealant were controls. All RBS were tested for surface roughness, Vickers hardness, flexural strength, and flowability. Statistical analysis with oneway ANOVA revealed significant differences between groups in surface roughness, hardness, flowability (p < 0.001), flexural strength, and flexural modulus (p < 0.05). Experimental sealants had higher flexural strength (78 MPa) and flow distance (29.05+1.16 mm) than commercial controls.However, the surface roughness of experimental sealants (0.25+0.08 μm) was higher than Clinpro (0.087+0.027 μm) but lesser than Fissurit FX (0.35+0.19 μm). The Vickers hardness of experimental sealants (23+1.63 VHN) was less than Fissurit FX (28.80+1.69 VHN) but higher than Clinpro (21.74+1.68 VHN). This novel RBS had physicomechanical properties comparable to commercial sealants. The use of nanosilica from rice husk makes this pit and fissure sealer sustainable and environmentally friendly in dentistry.

An In Vitro Evaluation of the Remineralizing Efficacy of Two concentrations of Silica Doped Nanohydroxyapatite on Bleached Enamel

@#Introduction: Vital bleaching of teeth is associated with mineral loss and surface roughness leading to hypersensitivity. Aesthetic restorations are recommended after one week. Search is on for a suitable remineralizing material, which helps in instant adhesive bonding. Hence objective of the study is to evaluate the remineralizing efficacy of two concentrations of Silica doped Nanohydroxyapatite on bleached enamel. Methods: Enamel surfaces of 30 extracted human central incisors were divided into Part A: Unbleached enamel, Part B: Bleached enamel, Part C: Remineralized enamel. The samples were randomly divided into, Group 1: MI Paste Plus (Recaldent, USA), Group 2 and 3 for application of Dentin bonding agents (Tetric- n-bond, Ivoclar, Vivadent) mixed 0.2% and 0.8% Silica doped Nanohydroxyapatite (Sigma Aldrich, Bangalore, India). Post bleaching remineralizing agents were applied on part C. Surface roughness was evaluated with contact stylus profilometer and mineral content was evaluated with Energy dispersive X-Ray spectroscopy for three parts. Data were analysed using ANOVA and Post Hoc Tukey test with p ≤ 0.05. Results: Surface roughness values (Ra) were increased, and mineral loss (Ca:P) was observed after bleaching. After application of remineralizing agents, surface roughness was decreased with no significant value (p > 0.05) and a significant increase in mineral content of all three groups with a p < 0.05 was observed. Conclusion: Application of dentin bonding agent mixed with Silica doped Nanohydroxyapatite decreased surface roughness and improved remineralization of bleached enamel.

Evaluation of desensitizing efficacy of nanohydroxyapatite on the treatment of dentine hypersensitivity following ultrasonic scaling: a randomized controlled trial / Avaliação da eficácia dessensibilizante da nanoidroxiapatita no tratamento da hipersensibilidade dentinária após raspagem ultrassônica: um ensaio clínico randomizado

Objective: This randomized controlled trial aimed to compare nanohydroxyapatite with fluoride on managing post ultrasonic scaling Dentine hypersensitivity (DH). Material and Methods: Thirty patients (aged 20-50 years) with post ultrasonic-scaling DH were included in this study. The sample was randomly divided into three equal groups of 60 teeth each: the first group received nanohydroxyapatite material, the second group received fluoride material and the third group received sterile water as a placebo (controls). The materials were applied once for each patient. All patients were instructed to rate the level of pain before treatment, and after 1 hour, 24 hours, 2 weeks and 1 month on the numerical rating scale (NRS). The Kruskal-Wallis test, Mann-Whitney tests, linear regression analysis were used for the statistical analysis. Significance level was set at 0.05. Results: Both nanohydroxyapatite and fluoride were successful in reducing pain associated with DH when compared with the placebo in subsequent follow-ups (p < 0.05). However, one-hour and one-day post application, nanohydroxyapatite could reduce hypersensitivity pain moreeffectively than fluoride (p < 0.05). Conclusion: Nanohydroxyapatite material was found to besignificantly more effective in reducing the DH that followed ultrasonic scaling one-hour and one-day post application as compared to fluoride and sterile water. Both fluoride and nanohydroxyapatite had similar effect on DH after two-weeks and one-month after application. (AU)

Objetivo: Este ensaio clínico randomizado teve como objetivo comparar a nano-hidroxiapatita com o flúor no manejo da hipersensibilidade dentinária (HD) pós-raspagem ultrassônica. Material e Métodos: Trinta pacientes (com idades entre 20-50 anos) com HD pós-raspagem ultrassônica foram incluídos neste estudo. A amostra foi dividida aleatoriamente em três grupos iguais com 60 dentes cada: o primeiro grupo recebeu material de nano-hidroxiapatita, o segundo grupo recebeu material de flúor e o terceiro grupo recebeu água esterilizada como placebo (controle). Os materiais foram aplicados uma vez para cada paciente. Todos os pacientes foram instruídos a avaliar o nível de dor antes do tratamento, e após 1 hora, 24 horas, 2 semanas e 1 mês na escala de avaliação numérica (NRS). Os testes de Kruskal-Wallis, Mann-Whitney e análise de regressão linear foram usados para a análise estatística. O nível de significância foi estabelecido em 0,05. Resultados: Tanto a nano- hidroxiapatita quanto o flúor foram bem-sucedidos na redução da dor associada à HD quando comparados ao placebo em acompanhamentos subsequentes (p <0,05). No entanto, 1 hora e 1 dia após a aplicação, a nano-hidroxiapatita pode reduzir a dor de hipersensibilidade de forma mais eficaz do que o flúor (p <0,05). Conclusão: O material da nano-hidroxiapatita foi significativamente mais eficaz na redução da HD que se seguiu à raspagem ultrassônica, 1 hora e 1 dia após a aplicação, em comparação com o flúor e a água estéril. Tanto o flúor, quanto a nano-hidroxiapatita apresentou efeito semelhante na HD após 2 semanas e 1 mês após a aplicação (AU)

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.

Effect of nanohydroxyapatite on surface mineralization in acid-etched dentinal tubules and adsorption of lead ions / 南方医科大学学报

OBJECTIVE@#To study the effect of nanohydroxyapatite (nHA) for promoting surface mineralization of demineralized dentin discs and adsorption of lead ions in simulated sewage water.@*METHODS@#Sixty dentin disks were prepared from freshly extracted teeth with intact crown (including 30 premolars and 30 molars) and treated with 10% citric acid for 2 min to simulate dentinal tubules with dentin hypersensitivity. The etched dentin discs were brushed with distilled water, 0.2 g HA or 0.2 g nHA for 2 min twice a day for 7 consecutive days, after which scanning electron microscopy (SEM) was performed and calcium and phosphorus contents in the dentin discs were detected using EDS. Lead ion adsorption capacities of HA and nHA were tested by mixing 1 mL serial concentrations of HA and nHA suspensions with 50 mL lead ion solutions (1.0 mg/L). After 24 h, the residual lead ion concentration in the supernatant was measured using ICP to calculate lead ion adsorption rate and adsorption capacity of the materials.@*RESULTS@#SEM showed a smooth surface and empty dentin tubules in the acid- etched dentin dics. The dentin dics treated with HA were covered with masses of particles that loosely attached to the surface, and the diameter of the dentin tubules was reduced. In nHA group, the dentin discs showed a fine and homogeneous surface clogging with a tight attachment, and the dentin tubule diameter was obviously reduced. Daily brushing with HA and nHA, especially the latter, significantly increased calcium and phosphorus contents on the surface of the dentin dics ( < 0.000). In lead ion adsorption experiment, the lead ion adsorption rate of HA decreased as its concentration increased with the highest adsorption rate of 83.01%; the adsorption rate of nHA increased with its concentration until the adsorption equilibrium was reached, and its highest adsorption rate was 98.79%. A good liner relationship was found between the adsorption ability and concentration of HA.@*CONCLUSIONS@#Compared with HA, nHA has a better capacity for surface mineralization of acid-etched dentin discs and also a better ability of lead ion adsorption.

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.

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.

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.

Clinical and Radiographic evaluation of mixture of Zinc Oxide powder and Nanohydroxyapatite as an obturating material in primary molars / Avaliação clínica e radiográfica da associação do pó de óxido de zinco com nanohidroxiapatita como um material obturador utilizado em primeiros molares

Pulpectomy is the treatment alternative in rescuing the pulpally involved carious primary teeth. Various obturating materials are being used to conserve an infected deciduous dentition. The present study documents the use of a novel obturating material in primary molars due to the disadvantages associated with of the currently used materials. Objective: To evaluate clinically and radiographically the success rate of the mixture of zinc oxide powder and nanohydroxyapatite with saline as an obturating material in primary molars and also to compare its efficiency with Endoflas. Material and Methods: Thirty pulpectomy indicated primary molars were randomly divided into two equal groups; Group I (mixture of zinc oxide powder and nanohydroxyapatite with saline) and Group II (Endoflas FS). The teeth were evaluated using various clinical and radiographic criteria at 3, 6 and 9-month intervals. The obtained results were statistically analyzed (P <0.05). Results: The overall present study findings revealed 100% clinical success in both the groups. Whereas radiographically, success reported was 66% for Group I and 100% for Group II at the end of 9 months followup. The difference in the radiographic success rate between the two groups was statistically significant (P <0.05). Conclusion: Endoflas FS had demonstrated high success rate both clinically and radiographically when compared to the novel combination of a mixture of zinc oxide powder and nanohydroxyapatite with saline as obturating material. (AU)

Pulpectomia é uma alternativa de tratamento que visa resgatar polpas envolvidas em processos cariosos de dentes decíduos. Vários materiais obturadores estão sendo usados para conservar a dentição decídua infectada. O presente estudo relata o uso de um novo material obturador em molares decíduos devido às desvantagens dos materiais atualmente utilizados. Objectivo: Avaliar clínica e radiograficamente a taxa de sucesso da mistura de pó de óxido de zinco e nanoidroxiapatita como material obturador em molares decíduos e também comparar sua eficiência com Endoflash. Material e Métodos: Trinta molares decíduos que foram indicados para pulpectomias foram divididos aleatoriamente em dois grupos iguais; Grupo I (mistura de pó de óxido de zinco e nanoidroxiapatita) e Grupo II (Endoflash). Os dentes foram avaliados utilizando vários critérios clínicos e radiográficos em intervalos de 3, 6 e 9 meses. Os resultados obtidos foram analisados estatisticamente (P <0,05). Resultados: Os achados gerais do presente estudo revelaram sucesso clínico de 100% em ambos os grupos. Enquanto que radiograficamente, o sucesso relatado foi de 66% para o Grupo I e 100% para o Grupo II ao final de 9 meses de acompanhamento. A diferença na taxa de sucesso radiográfico entre os dois grupos foi estatisticamente significante (P <0,05). Conclusão: O Endoflas demonstrou alta taxa de sucesso tanto clínica como radiograficamente quando comparado à nova combinação de pó de óxido de zinco e nanoidroxiapatita como material obturador (AU)

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.

Remineralization effect of nanohydroxyapatite on adjacent glazed surfaces / 口腔疾病防治

Objective@#To investigate the effect of a nanohydroxyapatite suspension with a 10% mass fraction on enamel demineralization after adjacent enamel removal and to provide a reference for the clinical use of nanohydroxyapatite to prevent enamel demineralization after adjacent enamel removal. @*Methods @#Forty fresh extracted premolars were incised from the coronal surface of the crown after glazing and polishing with sand strips. Each tooth was made into two specimens. Eighty teeth were randomly divided into four groups: a blank group, a dolofluoride group, a dental mousse group and a 10% nanohydroxyapatite group. After 30 days of pH cycling in vitro, a microhardness tester was used to detect the enamel surface elements before and after deglazing treatment. Scanning electron microscopy (SEM) and X-ray energy dispersive spectrometry (EDS) were used to analyze the enamel surface elements. @*Results@#After the experiment, the microhardness values of the adjacent glazed specimens of the four groups were (128.18 ± 6.89) kg/mm2 in the blank group, (216.75 ±9.87) kg/mm2 in the dolefluoride group, (198.88 ± 4.76) kg/mm2 in the dental care group and (218.44 ± 7.88) kg/mm2 in the 10% nanohydroxyapatite group, which were significantly different (F=189.14, P＜ 0.001). The LSD-t test showed that there was no significant difference between the dolefluoride group and the 10% nanohydroxyapatite group (P＜ 0.05), but the differences between the other groups were statistically significant (P > 0.05). There were significant differences in the Ca/P ratio among the blank group (1.39 ± 0.08), the dolefluoride group (1.70 ± 0.11), the dental care group (1.54 ± 0.12) and the 10% nanohydroxyapatite group (1.71 ± 0.14) (F=10.539, P＜ 0.001). There was no significant difference between the dolefluoride group and the nanohydroxyapatite group after the experiment (P > 0.05), but there were significant differences among the other groups (P＜ 0.05).@*Conclusion @#Dolerofluoride, dental protector and 10% nanohydroxyapatite can promote remineralization of enamel after enamel removal. The remineralization induced by 10% nanohydroxyapatite is similar to that induced by dolerofluoride.

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.

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.

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.

Antibacterial effects and tensile bonding strength of orthodontic adhesive containing nanohydroxyapatite / 口腔疾病防治

Objective @# To evaluate the tensile bonding strength (TBS) and antibacterial properties when an orthodontic adhesive was added with nanohydroxyapatite (nHAp). @*Methods@#Light cure orthodontic adhesive (Grengloo) was blended with 2% TiO2 containing nHAp nanoparticles by 0%、10%、20%、30% (w/w), while the control was not blended with nHAp. Brackets were bonded to extracted premolars by these new adhesives. TBS of 5groups were determined, and the adhesive remnant index (ARI) scores were assessed. Composite discs specimen were prepared, incubated with bacterial suspension for 48 h, and tested for antibacterial properties. @*Results @#No significant difference was found in ARI. The colony unit counts and lactate productionof the groups containing 2%TiO2 were significantly reduced. The colony unit counts and lactate production were without relationship with nHAp. The tensile bonding strength drastically decreased when containing more than 10% nHAp. @* Conclusin@#nHAp might not enhance the antibacterial effects of Grengloo.

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.