Papers by Keyword: Nanohydroxyapatite (HA)

Abstract: A novel porous composite scaffold of nano-HA/poly (lactic-co-glycolic) (PLGA) was fabricated by solvent casting/particulate leaching method. Chondrocytes were isolated from the knee articular joints of a rabbit, and then seeded in the scaffolds. The cell-loaded scaffolds were cultured in vitro for 5 days before implantation. Full-thickness articular cartilage defects were created in rabbits, and filled with and without the cell-loaded nano-HA/PLGA scaffolds. The implants were harvested after in vivo incubation of 2 and 5 weeks. Cartilaginous tissues were observed at defects repaired with the cell-loaded scaffolds, while only fibrous tissues were found for the control groups. The repaired tissues were evaluated histologically by hematoxylin and eosin staining. Results revealed that nano-HA/PLGA composite scaffolds facilitated adheration of cells in vitro, and the nano-HA particles could prevented the scaffolds from collapsing and promoted the formation of cartilaginous tissue in vivo.

Abstract: Hydroxyapatite has high affinity rate with organic substance in an oral cavity, therefore lately nano-sized hydroxyapatite is extensively researched to increase affinity to tooth and remineralization. The objective of this research is indirectly to investigate the effect of nanohydroxyapatite on remineralization using valuation about whiteness and bacterial contamination of the bovine tooth. We have designed in vitro test for this purpose. The bovine teeth are sliced into human teeth size then the baseline whiteness of total 60 teeth is measured and assigned into 3 groups by cross-matching according to the whiteness. These samples were embedded into resin mold and underwent mechanical brushing during fixed schedule. The whiteness and bacterial contamination of teeth are measured and compared among 3 groups. Each dentifrice used in the experiment is composed of B.S.I group (30% Calcium Carbonate, precipitated-CaCo3) with abrasion rate of 100, Test Ⅰgroup (15% Sodium Metaphosphate, insoluble-NaPo3), Test Ⅱ group (15% Nano-hydroxyapate-Ca10(PO4)6(OH)2. After 20,000 strokes of mechanical brushing with each group sample teeth whiteness is measured for 2nd time and then the sample teeth were submerged into the same solution with oral bacteria for 10 days. The teeth whiteness is measured again for 3rd time and the bacteria from the surface of teeth are cultivated on agar badge for 3 days. We have compared with average of whiteness before and after test in group and each other 3 group. The whiteness of teeth was maintained in test group II, however in other group the whiteness achieved through brushing was lost. Also, Group II had the smallest area of bacterial colony on agar badge (p<0.01). It is concluded that the dentifrice including the nano-hydroxyapatite is replaced with the organic substance in enamel resulting the increase in whiteness and the resistance to bacterial colonization, which leads to the increase the enamel remineralization in teeth and result to decrease in caries susceptibility.

Abstract: The aim of this study is to describe the remineralization effect of the nano-HA toothpaste on artificial caries. The artificial dental caries is made using sour solution. The demineralized teeth specimen is put into five kinds of toothpaste solution respectively for 5 days and 10 days, which are: solution of containing needle like nano-HA, solution of containing spherical nano-HA, solution of general HA, fluorine sodium solution and physiological saline. The hardness of specimen is measured and the surface morphology is characterized by SEM. The remineralized test indicates that the nano-HA toothpaste can enhance the hardness of artificial caries and improve the remineralization of artificial caries. The SEM analysis shows that the cavities and defects of enamel surface are decreased and many mineral salts are sedimentated, which indicate that the nano-HA could promote remineralization for the demineralized enamel.

Abstract: The purpose of this study is to examine the inhibitory effects of nano-HA on the caries-inducing properties of a four-organism bacterial consortium in vitro. A series of in vitro anticarious experiments have been carried out by using a continuous culture system. Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, Lactobacillus rhamnosus have been chosen as the experimental bacteria. After 48 hours, the dental plaque surface structure is observed with the scan electron microscope and the bacterial colonization was evaluated on dental plaque. The results show that Spherical nano-HA and mixed nano-HA are proved to be effective in anticarious experiments, and especially spherical nano-HA is more striking. It is able to damage the formation of biofilms (dental plaque), postpone or end the process of acid generation of bacteria metabolism. After 7 days, the demineralization of the enamel has been detected by using TEM. The spherical nano-HA might have a remineralization to early caries to prevent and decrease caries.

Abstract: Nano-sized zinc-substituted hydroxyapatite (nano-ZnHA) has stimulatory effect on bone formation and inhibitory effect on osteoclastic bone resorption in vivo. Nano-ZnHA with serial zinc fractions (0, 2, 5, 10 mol%) were synthesized by an improved precipitation method based on dialysis process. Transmission electron microscopy observation indicated that the increase of Zn fraction led to smaller crystallite. X-ray diffraction of the products revealed that some typical characteristic peaks of HA displayed when the Zn fraction was below 10%. Fourier transform infrared spectroscopy showed that the bending peaks of the group-OH in HA became wider with the increase of Zn fraction and it disappeared at 10 mol%. The current work demonstrated that zinc could substitute for calcium into hydroxyapatite in the limited range of composition by using dialysis process.

Abstract: The aim of this in vitro study was to evaluate the tooth whitening effect of toothpaste containing nano-sized hydroxyapatite (HA). There were 3 types of dentifrices, which had a different level of abrasive components. For group 1, a newly developed toothpaste containing Nano-sized hydroxyapatite (Nano-HA) was used. Commercially available toothpastes were used in groups 2 and 3. Group 2 used toothpastes containing silica and multi phosphate. Group 3 used toothpastes containing abrasives with silica and micro-sized HA. In order to simulate 6-months of tooth brushing, the tooth specimens in all 3 groups were placed on a V8 Cross Brushing Machine (Sabri Co. U.S.A.) and brushed 10,000 times with the toothpaste slurries. The tooth specimens were then soaked in artificial saliva for 24 hours to create conditions similar to those encountered in vivo. The whitening efficacy was assessed before and after tooth brushing using the VITA shade scores of Shadeeye-EX NCC Dental Chroma meter (Shofu Co. Japan). All toothpastes produced significant differences in the mean shade change in the teeth before and after tooth brushing (p<0.05). However, there were no significant differences in the change in the shade between each group (p>0.05). Although the new Nano-HA toothpaste did not have superior whitening effects to the commercially available whitening toothpastes, they had a similar whitening efficacy to commercially available whitening toothpastes. These effects might come from the physical properties of Nano HA, which increase the surface dimension more than the Micro-sized HA and have the potential of remineralization.

Abstract: Good interfacial interaction is crucial for preparation of inorganic-organic materials at a nanometer level. Poly(α-methacrylic acid) (PMAA) was grafted on the PLA surfaces via photooxidization and subsequent UV induced polymerization in an attempt to synthesize nano-hydroxyapatite/poly(lactide) (n-HA/PLA) composites. Grafting of PMAA on the PLA surface was confirmed using FTIR analysis and the size distribution measurement of the grafted-PLA (g-PLA) particles. n-HA/g-PLA composites were in situ synthesized via dropwise addition of Ca2+- and g-PLA containing solution to PO4 3-- solution. The prepared composites were characterized by FTIR, XRD，SEM and TEM means. Analytical results indicated that the g-PLA acts as a template to manipulate the nucleation and growth of n-HA crystals and thereby to control the morphology, size and anisotropy of n-HA crystals and their distribution over the organic phase. Chemical linkages and/or interfacial interactions between the n-HA and the g-PLA in the n-HA/g-PLA composite were further discussed.

Abstract: In this paper, three different scale HA/PDLLA porous scaffolds, nano-HA/PDLLA, micro-HA/PDLLA and pure PDLLA were successfully fabricated using solvent casting/particulate leaching method. Chondrocytes adhesion and proliferation on these scaffolds were investigated. In detail, the cells attachment rate and proliferation on nano-HA/PDLLA, micro-HA/PDLLA and pure PDLLA were quantitatively evaluated by cytometry. The interaction between the scaffolds and chondrocytes were observed by optical microscope with HE staining and FE-SEM. The results exhibited that nano-HA/PDLLA scaffold has a modified cell adhesion property, and cells on the nano-scaffold grow much better both in biological and morphological characteristics than on the micro-HA/PDLLA and pure PDLLA scaffolds. This work suggested that nano-HA/PDLLA composite scaffold can significantly improved cell adhesion and proliferation tendency with the existing of nano-effects，and could be used as a potential scaffold material for bone defect repair.