PMMA-grafted nanoclay as novel filler for dental adhesives

ObjectiveThe aim of this study was to investigate the benefits of incorporation of poly(methyl methacrylate)-grafted-nanoclay on the bond strength of an experimental one-bottle dentin bonding system. The effect of the modification on the stability of the nanoparticle dispersion in the dilute adhesive was also studied.Materials and methodsPoly(methyl methacrylate) was grafted onto the pristine Na-MMT nanoclay (Cloisite^® Na⁺) through the free radical polymerization of methyl methacrylate in an aqueous media in the presence of ammonium persulfate as initiator. A reactive surfactant (AMPS) was also used in the reaction recipe to provide active sites on the surface of the nanoclay. The grafting polymerization reaction was carried out at 70 °C. The PMMA-g-nanoclay was then coagulated in methanol and filtered. The resulting PMMA-g-nanoclay was characterized using FTIR, TGA, X-ray diffraction (XRD) and particle size distribution analysis. The modified nanoclay was added to an experimental dentin bonding system as filler and the morphology of the nanoclay layers in the adhesive matrix was studied using TEM and XRD. Shear bond strength of the adhesives containing different filler contents was tested on the caries-free extracted human premolar teeth. The mode of failure was studied by scanning electron microscopy. The stability of the nanoclay dispersion in the dilute adhesive was also studied using a separation analyzer. The results were then statistically analyzed and compared.ResultsThe grafting of poly(methylmethacrylate) onto the nanoclay was confirmed and the results revealed a partially exfoliated structure for the PMMA-g-nanoclay. Incorporation of the modified nanoclay provided a dentin bonding system with higher shear bond strength. The dispersion stability of the modified nanoparticles in the dilute adhesive was also increased more than 40 times in comparison with the pristine nanoclay.SignificanceThe grafting modification provided nanoclay particles with higher dispersion stability than pristine Na-MMT nanoclay in a dilute dentin bonding system. Incorporation of the modified nanoclay into the bonding system provided higher shear bond strength. The finding would be beneficial in producing nano-filler containing adhesive systems.     

Immunological Basis of Neurological Diseases

Clinical neurology has been traditionally considered as an academic speciality in which the specialist regurgitates his/her knowledge of neurology without being able to do much for the patient. This attitude is no longer acceptable. Surge of information and discoveries in neurosciences within the last two decades translated into therapeutic interventions which is literally life saving in some occasions. Neuroimmunology, without a doubt, has been in the forefront of such discoveries. Just a few decades ago immunology of the nervous system was of little interest because brain was thought to be an immunologically “privileged” organ i.e. inaccessible to cellular and humeral immunity. Today, however, clinical neurologists deal with neurological problem with immunological basis on a daily basis. This article tries to review such diseases and their current therapeutic strategy proceeded by an introduction to CNS immunity. Multiple sclerosis, as one of the most common CNS disease with immunological basis, has been given more attention because of the growing number of affected people in Iran.     

A randomized controlled trial on the efficacy,safety, and pharmacokinetics of metformin in severe traumatic brain injury

Journal of Neurology - Traumatic brain injury (TBI) is a leading cause of morbidity and mortality worldwide. Metformin is reported to have pleiotropic neuroprotective effects through...     

Regional atrophy of transcallosal prefrontal connections in cognitively normal APOE ϵ4 carriers

Purpose

To investigate the possible effect of the APOE ?4 allele on age‐related regional volume loss within the corpus callosum (CC) in healthy ?4 allele carriers compared with noncarriers.

Materials and Methods

A total of 211 subjects, ages 27 to 83 years, 51 ?4 carriers and 160 noncarriers underwent T1‐weighted MRI scan. All subjects had normal MRI scan and performed within normal range on a neuropsychological battery of tests. CC was segmented into seven functionally relevant regions using a previously published probabilistic map of the CC connectivity. We measured the volumes of the CC and its subregions. We used a regression model (with volumes as dependent and age as independent variables) and compared the slopes between carriers and noncarriers using an analysis of covariance model. We also carried out voxel‐based‐morphometry analysis to investigate the possible effect of the APOE ?4 gene on the gray matter.

Results

We found that the volume of the CC and all subregions decreased with increasing age in both groups. The slope was steeper in the APOE ?4 carriers compared withthe noncarriers particularly in the prefrontal region (P = 0.02). No gray matter differences were observed between the two groups.

Conclusion

APOE ?4 polymorphism is associated with accelerated age‐related volume loss in the prefrontal callosal tracts without gray matter loss. This result suggests the role of APOE ?4 in the brain aging by primarily affecting white matter structures particularly in the frontal lobe. J. Magn. Reson. Imaging 2009;29:1021–1026. © 2009 Wiley‐Liss, Inc.

     

In vitro maturation,apoptotic gene expression and incidence of numerical chromosomal abnormalities following cryotop vitrification of sheep cumulus-oocyte complexes

Purpose  

The purpose of this study was to evaluate the effects of cryotop vitrification of sheep cumulus-oocyte complexes (COCs) on oocyte maturation, apoptotic gene expression and incidence of chromosomal abnormalities.     

Breast tumor targeting with (99m)Tc-HYNIC-PR81 complex as a new biologic radiopharmaceutical

Human epithelial mucin, MUC1, is commonly overexpressed in adenocarcinoma that includes more than 80% of breast cancers. The PR81 is a murine anti-MUC1 monoclonal antibody (MAb) that was prepared against the human breast cancer. We developed an indirect method for labeling of this antibody with (99m)Tc in order to use the new preparation in immunoscintigraphy studies of BALB/c mice bearing breast tumors. The (99m)Tc-PR81 complex was prepared using the HYNIC as a chelator and tricine as a coligand. The labeling efficiency determined by instant thin-layer chromatography (ITLC) was 89.2%+/-4.7%, and radiocolloides measured by cellulose nitrate electrophoresis were 3.4%+/-0.9%. The in vitro stability of labeled product was determined at room temperature by ITLC and in human serum by gel filtration chromatography - 88.3%+/-4.6% and 79.8%+/-5.7% over 24 h, respectively. The integrity of labeled MAb was checked by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis, and no significant fragmentation was seen. The results of cell binding studies showed that both labeled and unlabeled PR81 were able to compete for binding to MCF 7 cells. Biodistribution studies performed in female BALB/c mice with breast tumor xenografts at 4, 16 and 24 h after the (99m)Tc-HYNIC-PR81 injection demonstrated a specific localization of the compound at the site of tumors and minimum accumulation in non target organs. The tumor imaging was performed in BALB/c mice with breast xenograft tumors at 4, 8, 12, 16, 20, 24, 28, 32 and 36 h after the complex injection. The tumors were visualized with high sensitivity after 8 h. The findings showed that the new radiopharmaceutical is a promising candidate for radioimmunoscintigraphy of the human breast cancer.