Incidence and Intensity of Pain Following Endodontic Treatment by Different Instrumentation Techniques in Teeth With Periapical Lesion.

AIM AND OBJECTIVES:  This study was carried out to compare the effectiveness of hand and rotary instrumentation techniques on postoperative pain in asymptomatic necrotic premolars with periapical lesions and instrumented by a modified step-back technique using a K file, crown down by continuous rotary motion technique using ProTaper Universal (Dentsply Mailefer, Ballaigues, Switzerland), and with the reciprocation technique using WaveOne (Dentsply Sirona, Charlotte, NC, USA). MATERIALS AND METHODS:  For this study, 66 premolars with single roots and canals were chosen. The procedure was completed in a single visit. Following access opening, the working length was initially determined using an apex locator and then confirmed after inserting K file #10 by radiograph. The canal was cleaned and shaped using a grouping system. After the master apical preparation, the canal was dried by paper point and obturated with gutta-percha and AH plus sealer, an epoxide-amine resin pulp canal sealer. In order to confirm the obturation, a radiograph was taken. After that, a permanent restoration material was used to seal the access cavity. Following that, patients to whom the visual analog scale (VAS) had already been explained were contacted by phone at six, 12, 24, and 48 hours. RESULTS:  In this study, compared to a stainless steel instrumentation technique, WaveOne instrumentation caused more noticeable pain. The results of the current study showed that, on average, postoperative pain scores decreased over the course of the 12 to 48-hour period, reaching a minimum or a maximum at 48 hours (p<0.01). CONCLUSION:  Postoperative pain was produced by all instrumentation methods used in the study. In comparison to ProTaper and WaveOne, instrumentation using the modified step-back technique with K files caused less pain, especially over the course of a 24-hour period.

Recent Advanced Diagnostic Aids in Orthodontics.

Everyone aspires to have a youthful appearance, complete with a beaming grin. By treating skeletal and dental malocclusions that interfere with facial aesthetics, orthodontics helps patients attain a beautiful face and a smile they will be proud of. The diagnosis of the underlying illness or condition serves as the basis for all medical, dental, and surgical operations. Dental professionals all across the world have reaped the benefits of a major scientific advance in recent years. Many measurements may now be seen and quantified more easily using computer-assisted cephalometry. The accuracy and high quality of all dental materials have been enhanced thanks to computer-aided design and computer-aided manufacture. There have been several developments in the realm of orthodontics. The growing use of technology in recent years has transformed every sector, including medicine and dentistry. From Angle's time to today's nanorobotic age, orthodontic ideas, biomaterials, and technology have evolved greatly. It has been extensively utilized for diagnosis, treatment planning, three-dimensional printing, appliance systems, digital storage, integration, and data retrieval. The technology used in orthodontics is always getting better, and this article aims to give an overview of the most recent changes.

Plasticity revisited.

Despite some recent setbacks, it remains clear that adult stem cells under appropriate experimental conditions can at some frequency exhibit a wider range of differentiation potentials than previously appreciated. This is underscored by the recent demonstration of the extensive differentiation potential of mesenchymal stem cells. In terms of mechanism, it remains unclear in many cases to what extent plasticity reflects in vitro adaptation, transdifferentiation/cell-type switching or the persistence in adult tissues of stem cells with extensive endogenous or bona fide developmental potentials. These issues will need to be resolved before the full therapeutic potential of adult-derived stem cells can be realised.

Molecular signatures of self-renewal, differentiation, and lineage choice in multipotential hemopoietic progenitor cells in vitro.

The molecular mechanisms governing self-renewal, differentiation, and lineage specification remain unknown. Transcriptional profiling is likely to provide insight into these processes but, as yet, has been confined to "static" molecular profiles of stem and progenitors cells. We now provide a comprehensive, statistically robust, and "dynamic" analysis of multipotent hemopoietic progenitor cells undergoing self-renewal in response to interleukin-3 (IL-3) and multilineage differentiation in response to lineage-affiliated cytokines. Cells undergoing IL-3-dependent proliferative self-renewal displayed striking complexity, including expression of genes associated with different lineage programs, suggesting a highly responsive compartment poised to rapidly execute intrinsically or extrinsically initiated cell fate decisions. A remarkable general feature of early differentiation was a resolution of complexity through the downregulation of gene expression. Although effector genes characteristic of mature cells were upregulated late, coincident with morphological changes, lineage-specific changes in gene expression were observed prior to this, identifying genes which may provide early harbingers of unilineage commitment. Of particular interest were genes that displayed differential behavior irrespective of the lineage elaborated, many of which were rapidly downregulated within 4 to 8 h after exposure to a differentiation cue. These are likely to include genes important in self-renewal, the maintenance of multipotentiality, or the negative regulation of differentiation per se.

Functional and molecular characterisation of mammary side population cells.

BACKGROUND: Breast cancer is thought to arise in mammary epithelial stem cells. However, the identity of these stem cells is unknown. METHODS: Studies in the haematopoetic and muscle systems show that stem cells have the ability to efflux the dye Hoechst 33342. Cells with this phenotype are referred to as the side population (SP). We have adapted the techniques from the haematopoetic and muscle systems to look for a mammary epithelial SP. RESULTS: Of mammary epithelial cells isolated from both the human and mouse mammary epithelia, 0.2-0.45% formed a distinct SP. The SP was relatively undifferentiated but grew as typical differentiated epithelial clones when cultured. Transplantation of murine SP cells at limiting dilution into cleared mammary fat pads generated epithelial ductal and lobuloalveolar structures. CONCLUSION: These data demonstrate the existence of an undifferentiated SP in human and murine mammary epithelium. Purified SP cells are a live single-cell population that retain the ability to differentiate in vitro and in vivo. Studies of haematopoetic cells have suggested that the SP phenotype constitutes a universal stem cell marker. This work therefore has implications for mammary stem cell biology.

Micropatterning of human embryonic stem cells dissects the mesoderm and endoderm lineages.

Human pluripotent cells such as human embryonic stem cells (hESC) are a great potential source of cells for cell-based therapies; however, directing their differentiation into the desired cell types with high purity remains a challenge. The stem cell microenvironment plays a vital role in directing hESC fate and we have previously shown that manipulation of colony size in a serum- and cytokine-free environment controls self-renewal and differentiation toward the extraembryonic endoderm lineage. Here we show that, in the presence of bone morphogenetic protein 2 and activin A, control of colony size using a microcontact printing technology is able to direct hESC fate to either the mesoderm or the endoderm lineage. Large, 1200-mum-diameter colonies give rise to mesoderm, while small 200-mum colonies give rise to definitive endoderm. This study links, for the first time, cellular organization to pluripotent cell differentiation along the mesoderm and endoderm lineages.

Reproducible, ultra high-throughput formation of multicellular organization from single cell suspension-derived human embryonic stem cell aggregates.

BACKGROUND: Human embryonic stem cells (hESC) should enable novel insights into early human development and provide a renewable source of cells for regenerative medicine. However, because the three-dimensional hESC aggregates [embryoid bodies (hEB)] typically employed to reveal hESC developmental potential are heterogeneous and exhibit disorganized differentiation, progress in hESC technology development has been hindered. METHODOLOGY/PRINCIPAL FINDINGS: Using a centrifugal forced-aggregation strategy in combination with a novel centrifugal-extraction approach as a foundation, we demonstrated that hESC input composition and inductive environment could be manipulated to form large numbers of well-defined aggregates exhibiting multi-lineage differentiation and substantially improved self-organization from single-cell suspensions. These aggregates exhibited coordinated bi-domain structures including contiguous regions of extraembryonic endoderm- and epiblast-like tissue. A silicon wafer-based microfabrication technology was used to generate surfaces that permit the production of hundreds to thousands of hEB per cm(2). CONCLUSIONS/SIGNIFICANCE: The mechanisms of early human embryogenesis are poorly understood. We report an ultra high throughput (UHTP) approach for generating spatially and temporally synchronised hEB. Aggregates generated in this manner exhibited aspects of peri-implantation tissue-level morphogenesis. These results should advance fundamental studies into early human developmental processes, enable high-throughput screening strategies to identify conditions that specify hESC-derived cells and tissues, and accelerate the pre-clinical evaluation of hESC-derived cells.

Determination of growth inhibitory action point of interferon gamma on WISH cells in cell cycle progression and the window of responsiveness of the cells to the interferon.

We had earlier shown that human foetal epithelial cells (WISH), growth-inhibited by interferon gamma (IFNgamma), were reversibly detained at a point prior to DNA synthesis. In the present study, we determined the window of action of IFNgamma in the G1 phase duration and the exact point of detention of WISH cells in cell cycle progression with respect to the known points of detention by the inhibitors of DNA replication initiation (aphidicolin and carbonyl diphosphonate) and of activation of replication protein A (6-dimethylaminopurine), of which RPA activation being the earlier event compared to DNA replication initiation in cell cycle progression. WISH cells, which were released from IFNgamma-induced arrest, permeabilised and exposed independently to these inhibitors show that IFNgamma detains WISH cells prior to initiation of DNA synthesis. Further, exposure of IFNalpha-synchronized (at G0/G1) or mimosine-synchronized (at G1/S) WISH cells to IFNgamma, which was added at different time points post-release from the synchronizing agent, showed that the cells were promptly responsive to the growth inhibitory action of IFNgamma only during the first 11h in G1 phase. Taken together, these results suggest that IFNgamma inhibits growth of WISH cells by detaining them at a point prior to initiation of DNA synthesis and that the IFN acts within the first 11h in G1 phase of the cell cycle.

Cellular differentiation hierarchies in normal and culture-adapted human embryonic stem cells.

Human embryonic stem cell (HESC) lines vary in their characteristics and behaviour not only because they are derived from genetically outbred populations, but also because they may undergo progressive adaptation upon long-term culture in vitro. Such adaptation may reflect selection of variants with altered propensity for survival and retention of an undifferentiated phenotype. Elucidating the mechanisms involved will be important for understanding normal self-renewal and commitment to differentiation and for validating the safety of HESC-based therapy. We have investigated this process of adaptation at the cellular and molecular levels through a comparison of early passage (normal) and late passage (adapted) sublines of a single HESC line, H7. To account for spontaneous differentiation that occurs in HESC cultures, we sorted cells for SSEA3, which marks undifferentiated HESC. We show that the gene expression programmes of the adapted cells partially reflected their aberrant karyotype, but also resulted from a failure in X-inactivation, emphasizing the importance in adaptation of karyotypically silent epigenetic changes. On the basis of growth potential, ability to re-initiate ES cultures and global transcription profiles, we propose a cellular differentiation hierarchy for maintenance cultures of HESC: normal SSEA3+ cells represent pluripotent stem cells. Normal SSEA3- cells have exited this compartment, but retain multilineage differentiation potential. However, adapted SSEA3+ and SSEA3- cells co-segregate within the stem cell territory, implying that adaptation reflects an alteration in the balance between self-renewal and differentiation. As this balance is also an essential feature of cancer, the mechanisms of culture adaptation may mirror those of oncogenesis and tumour progression.

Molecular complexities of stem cells.

Stem cells continue to attract considerable attention and provide hope for the development of new cell-based therapies for degenerative diseases. Unlocking the full therapeutic potential of stem cells requires an understanding of the mechanisms by which they are generated, self-renew, and differentiate. The application of post-genomic technologies is beginning to provide insight into the nature of the molecular ground state of different stem cell compartments. One emerging theme is the considerable molecular complexity in which many possible differentiation pathways are primed, providing one possible strategy for enabling the diverse responsiveness of stem cells. This new information should ultimately reveal any common molecular attributes of "stemness" and aid in rational approaches to the manipulation of stem cells for therapeutic benefit.