Current Issue : July - September Volume : 2012 Issue Number : 3 Articles : 7 Articles
The major challenge for dental implants is achieving optimal esthetic appearance and a concept to fulfill this criterion is evaluated.\r\nThe key to an esthetically pleasing appearance lies in the properly manage the soft tissue profile around dental implants. A novel\r\nimplant restoration technique on the surface was proposed as a way to augment both soft- and hard-tissue profiles at potential\r\nimplant sites. Different levels of roughness can be attained by sandblasting and acid etching, and a tetracalcium phosphate was\r\nused to supply the ions. In particular, the early stage attaching and repopulating abilities of bone cell osteoblasts (MC3T3-E1),\r\nfibroblasts (NIH 3T3), and epithelial cells (XB-2) were evaluated. The results showed that XB-2 cell adhesive qualities of a smooth\r\nsurface were better than those of the roughened surfaces, the proliferative properties were reversed. The effects of roughness on\r\nthe characteristics of 3T3 cells were opposite to the result for XB-2 cells. E1 proliferative ability did not differ with any statistical\r\nsignificance. These results suggest that a rougher surface which provided calcium and phosphate ions have the ability to enhance\r\nthe proliferation of osteoblast and the inhibition of fibroblast growth that enhance implant success ratios....
Female mammals inactivate one of their two X-chromosomes to compensate for the difference in gene-dosage with males\r\nthat have just one X-chromosome. X-chromosome inactivation is initiated by the expression of the non-coding RNA Xist,\r\nwhich coats the X-chromosome in cis and triggers gene silencing. In early mouse development the paternal X-chromosome\r\nis initially inactivated in all cells of cleavage stage embryos (imprinted X-inactivation) followed by reactivation of the\r\ninactivated paternal X-chromosome exclusively in the epiblast precursors of blastocysts, resulting temporarily in the\r\npresence of two active X-chromosomes in this specific lineage. Shortly thereafter, epiblast cells randomly inactivate either\r\nthe maternal or the paternal X-chromosome. XCI is accompanied by the accumulation of histone 3 lysine 27 trimethylation\r\n(H3K27me3) marks on the condensed X-chromosome. It is still poorly understood how XCI is regulated during early human\r\ndevelopment. Here we have investigated lineage development and the distribution of H3K27me3 foci in human embryos\r\nderived from an in-vitro model for human implantation. In this system, embryos are co-cultured on decidualized\r\nendometrial stromal cells up to day 8, which allows the culture period to be extended for an additional two days. We\r\ndemonstrate that after the co-culture period, the inner cell masses have relatively high cell numbers and that the GATA4-\r\npositive hypoblast lineage and OCT4-positive epiblast cell lineage in these embryos have segregated. H3K27me3 foci were\r\nobserved in ,25% of the trophectoderm cells and in ,7.5% of the hypoblast cells, but not in epiblast cells. In contrast with\r\nday 8 embryos derived from the co-cultures, foci of H3K27me3 were not observed in embryos at day 5 of development\r\nderived from regular IVF-cultures. These findings indicate that the dynamics of H3K27me3 accumulation on the Xchromosome\r\nin human development is regulated in a lineage specific fashion....
The mammalian Msx homeobox genes, Msx1 and Msx2, encode transcription factors that control organogenesis and tissue\r\ninteractions during embryonic development. We observed overlapping expression of these factors in uterine epithelial and\r\nstromal compartments of pregnant mice prior to embryo implantation. Conditional ablation of both Msx1 and Msx2 in the\r\nuterus resulted in female infertility due to a failure in implantation. In these mutant mice (Msx1/2d/d), the uterine epithelium\r\nexhibited persistent proliferative activity and failed to attach to the embryos. Gene expression profiling of uterine\r\nepithelium and stroma of Msx1/2d/d mice revealed an elevated expression of several members of the Wnt gene family in the\r\npreimplantation uterus. Increased canonical Wnt signaling in the stromal cells activated b-catenin, stimulating the\r\nproduction of a subset of fibroblast growth factors (FGFs) in these cells. The secreted FGFs acted in a paracrine manner via\r\nthe FGF receptors in the epithelium to promote epithelial proliferation, thereby preventing differentiation of this tissue and\r\ncreating a non-receptive uterus refractory to implantation. Collectively, these findings delineate a unique signaling network,\r\ninvolving Msx1/2, Wnts, and FGFs, which operate in the uterus at the time of implantation to control the mesenchymalepithelial\r\ndialogue critical for successful establishment of pregnancy....
Objective. This study aimed to define CBCT as a technique for postimplantation in vivo examination of porous hydroxyapatite\r\nand aluminium-oxide orbital implant shape, volume and density changes. Methods and Materials. CBCT was used to evaluate\r\n30 enucleated patients treated with spherical polyglactin 910 wrapped hydroxyapatite and aluminum-oxide orbital implants. The\r\nmean duration of patient followup was 3.2 years or 1338 days with a range of 0.2 to 7.2 years or 79 to 2636 days in a population\r\nwith an average age of 40.8 years. Results. The resolution of currently clinically used CBCT equipment allowed detailed structural\r\nobservation of the orbital hydroxyapatite implants with some modifications. Volume and shape estimations were possible while\r\ndensity evaluation was more complicated compared to medical source computed tomography. The mean densities of the orbital\r\nimplants were followed and a consistent gradual decrease identified from the beginning of implantation which was better defined\r\nafter the applied correction procedure. Conclusion. CBCT with lower dosages of radiation exposure can be used to follow changes\r\nin implanted high-density porous structures. The density evaluation is possible with calibration modifications. Changes in orbital\r\nimplant densities identified in this study may correspond to healing and maturation of soft tissues surrounding and penetrating\r\nthe implants....
Miniaturization of active implantable medical devices is currently compromised by the available means for electrically\r\npowering them. Most common energy supply techniques for implants ââ?¬â?? batteries and inductive couplers ââ?¬â?? comprise bulky\r\nparts which, in most cases, are significantly larger than the circuitry they feed. Here, for overcoming such miniaturization\r\nbottleneck in the case of implants for electrical stimulation, it is proposed to make those implants act as rectifiers of high\r\nfrequency bursts supplied by remote electrodes. In this way, low frequency currents will be generated locally around the\r\nimplant and these low frequency currents will perform stimulation of excitable tissues whereas the high frequency currents\r\nwill cause only innocuous heating. The present study numerically demonstrates that low frequency currents capable of\r\nstimulation can be produced by a miniature device behaving as a diode when high frequency currents, neither capable of\r\nthermal damage nor of stimulation, flow through the tissue where the device is implanted. Moreover, experimental\r\nevidence is provided by an in vivo proof of concept model consisting of an anesthetized earthworm in which a commercial\r\ndiode was implanted. With currently available microelectronic techniques, very thin stimulation capsules (diameter\r\n,500 mm) deliverable by injection are easily conceivable....
The presence of insufficient bone volume remains a major clinical problem for dental implant placement to restore the oral\r\nfunction. Gene-transduced stem cells provide a promising approach for inducing bone regeneration and enhancing\r\nosseointegration in dental implants with tissue engineering technology. Our previous studies have demonstrated that the\r\nhypoxia-inducible factor-1? (HIF-1?) promotes osteogenesis in rat bone mesenchymal stem cells (BMSCs). In this study, the\r\nfunction of HIF-1? was validated for the first time in a preclinical large animal canine model in term of its ability to promote\r\nnew bone formation in defects around implants as well as the osseointegration between tissue-engineered bone and dental\r\nimplants. A lentiviral vector was constructed with the constitutively active form of HIF-1? (cHIF). The ectopic bone formation\r\nwas evaluated in nude mice. The therapeutic potential of HIF-1?-overexpressing canine BMSCs in bone repair was evaluated\r\nin mesi-implant defects of immediate post-extraction implants in the canine mandible. HIF-1? mediated canine BMSCs\r\nsignificantly promoted new bone formation both subcutaneously and in mesi-implant defects, including increased bone\r\nvolume, bone mineral density, trabecular thickness, and trabecular bone volume fraction. Furthermore, osseointegration\r\nwas significantly enhanced by HIF-1?-overexpressing canine BMSCs. This study provides an important experimental\r\nevidence in a preclinical large animal model concerning to the potential applications of HIF-1? in promoting new bone\r\nformation as well as the osseointegration of immediate implantation for oral function restoration....
The clinical success of osseointegrated dental implants depends on the strong attachment of the surrounding hard and soft\r\ntissues. Bacterial adhesion on implant surfaces can cause inflammatory reactions and may influence healing and long-term success\r\nof dental implants. Promising implant coatings should minimize bacterial adhesion, but allow epithelial and connective tissue\r\nattachment. Therefore, the present study has examined the bioactive effect of poly-(4-vinyl-N-hexylpyridiniumbromide) regarding\r\ntypical oral bacteria as well as cytotoxicitiy to human cells considering different methods of connecting polymers to silicatecontaining\r\nsurfaces. The results revealed that the application of putative antibacterial and biocompatible polymer in coating\r\nstrategies is affected by a variety of parameters. Published findings regarding reduced bacterial adhesion could not be verified\r\nusing oral pathogens whereas hexylated polymers seem problematic for strong adhesion of soft tissue. Concerning innovative\r\ncoatings for dental implants basic aspects (surface roughness, thickness, alkylation, combination with other polymers) have to be\r\nconsidered in further investigations....
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