جستجوی مقالات مرتبط با کلیدواژه "biomineralization" در نشریات گروه "پزشکی"

Statement of the Problem: 

Dentin bonding with etch-and-rinse adhesives involves demineralizing the 5-8µm of the surface dentin to create micro space for resin infiltration. The presence of continuous fluid movement in dentin tubules and positive pulpal pressure prevents complete water replacement by resin monomers. This results in areas of demineralized dentin, which contain collagen fibers without resin infiltration. The exposed collage fibers are subjected to enzymatic degradation leading to less durable hybrid layer.

The aim of this study was to evaluate the remineralizing effect of the nanoparticles on the resin dentin bonding interface.

The three experimental remineralizing nanoparticles were characterized for their morphology, size, and composition. A total of 48 extracted non-carious human third molar teeth were sectioned at 2 mm below the cemento enamel junction. Class I cavity was prepared and the tooth samples were placed in an intra pulpal pressure simulation device. After etching of the prepared cavity, the samples were randomly divided into four groups (n=10) as follows: (1) control group(c) (n=10) (2) Nano-hydroxyapatite (nHAP) (n=10) (3) Chitosan-nanohydroxyapatite (Chi-nHAP) (n=10) (4) Mesoporous silica-hydrox-yapatite (MS-nHAP) (n=10). After 30 days remineralization period, the samples were evaluated for micro tensile bond strength, hybrid layer morphology, and mineral composition of the hybrid layer. The results were analyzed statistically by one-way ANOVA and Tukey's multiple post hoc tests.

Scanning electron microscopic observation of nanoparticles revealed irregular particle shapes with calcium phosphate ratio of 1.60. The zeta analyzer showed a mean diameter of 161.0 nm, 323.0nm, 185.0nm for nHAP, Chi-nHAP, and MS-nHAP respectively. Post hoc Bonferroni test revealed significantly higher bond strength for nHAP, Chi-nHAP, and MS-nHAP when compared to control group. MS-nHAP resulted in the uniform deposition of apatite crystal on the surface without any evidence of dentinal tubules openings and had higher mineral to matrix ratio compared to other groups.

MS-nHAP nanoparticles can be considered as a reliable source of calcium and phosphate for biomimetic remineralization of hybrid layer. Application of nanoparticle remineralization precursors before application of dentin bonding agents results in remeralization of exposed collagen fibers thereby improving the clinical longevity of hybrid layer.

Hydroxyapatite (HA) has many applications in medicine, dentistry, diagnosis, drug delivery systems, sewage treatment, bone remodeling, concentrating bacteria, covering implants, and antibacterial activity. Despite the numerous current applications of calcium phosphate compounds, particularly HA, their producing methods are being investigated to find the best processes. Several chemical and biological methods are used in calcium phosphate compounds synthesis. Researches have shown that compared to micrometer models, nanostructured HA has higher mechanical features and better biocompatibility in the human body. These properties optimize when nanometer components of HA are in similar size and shape with the least agglomerations. Biomineralization by microorganisms, which is a bacterial route, is a recent HA synthesis method. This paper is a review on the biosynthesis of HA emphasizing microbial methods. In this method, some bacteria and mold could be used in the nanometer production of HA. This type of bacterium commonly has a high amount of alkaline phosphatase enzymes. Desirable similarity to natural HA in the human body is the noticeable features of bacterial HA. Uniformity in the shape and size of synthesized particles that have the same crystallization is of other merits. Producing bacterial HA is easily reachable, one-step, inexpensive, harmless, and with high purity, and contrary to chemical synthesis, does not need heat treatment and precise pH adjustment.

Statement of the Problem:

 The stimulation of odontogenic activity is considered an essential property for biomaterials used in vital pulp therapy.

The present study aimed to evaluate the effect of the incorporation of zeolite containing silver-zinc nanoparticles (Ze-Ag-Zn) into Angelous mineral trioxide aggregate (AMTA) on the odontogenic activity of human dental pulp stem cells (HDPSCs).

In this in vitro study, HDPSCs were treated with 2% wt of synthesized Ze-Ag-Zn particles+AMTA, AMTA and Ze-Ag-Zn disks. The negative control cells did not receive any treatment. Then, cell viability was measured using the MTT assay after 7 and 14 days of the treatment course. The alkaline phosphatase (ALP) activity and calcium ion level were also measured in the supernatant culture media using auto-analyzer kits. The obtained data were analyzed using one-way ANOVA and Student t-test where appropriate. The level of the statistical significance was set at p < 0.05.

The results indicated that HDPSCs treated with AMTA and AMTA+ Ze-Ag-Zn particles did not show any significant cell death compared with the control cells after 14 days of the treatment course while the ALP activity and calcium ion levels were significantly (p < 0.05) elevated. Also, the addition of AMTA particles to the cell culture media resulted in increased ALP activity and calcium ion level compared with HDPSCs treated with AMTA + Ze-Ag-Zn particles on day 7 of the treatment course (p < 0.05).

It seems that the incorporation of Ze-Ag-Zn particles into AMTA did not have any significant positive effect on the biomineralization properties of AMTA.

This research focused on the detection of nanobacteria in kidney stones of 30 Iranian patients without adding fetal bovine serum (FBS) to the culture media.
Nanobacteria were isolated from a nephro-ureterolithiasis extract of the urinary tract and kidney of patients and were cultured in the laboratory. The growth of nanobacteria was monitored using a spectrophotometer, and with inverted microscopy technique, their crystallization was analyzed after two days. The images from atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) indicated the morphology and demonstrated the size of the cultured nanobacteria which is between 60 and 160 nm. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to study the chemical composition, surface functional groups and crystal structure of the igloo-like nanobacteria shell. FTIR spectra in the region of 1000 to 1200 cm-1 and the XRD peaks provided evidence that the main components of the nanobacteria shell were apatite-based compounds.
Nanobacteria infected all the 27 patients with apatite kidney stone, and none of the three patients who had uric acid kidney stone were infected as confirmed by the cultivation of the stones samples. The results showed that nanobacteria might play a fundamental role in the formation of apatite-based kidney stones.
The biomineralization ability of nanobacteria may lead to calcification of the soft tissues, which in turn may result in other diseases. It is also suggested that nanobacteria may be a factor in calcification-related diseases and disorders with poorly characterized etiologies. This research with its different approaches, clarified significant doubts that nanobacteria act as contaminant, warranting continued investigation of its role in other diseases.