Abstract. Although the central role of ameloblasts in synthesis and resorption of enamel matrix proteins during amelogenesis is well documented, the Ca
Previous reports have shown the expression of several mechanosensitive ionic channels on the plasma membrane in odontoblasts, which are the cells responsible for dentin formation. The membrane characteristics of odontoblasts imply that they could play critical roles in the mechano-transduction of fluid displacement within dentinal tubules into the electrical cell signals, to carry dentin sensation to the central nervous system. However, the direct ionic mechanism underlying such a dentin nociceptive function remains unclear. In the present study, we investigated the expression of the transient receptor potential vanilloid subfamily member 1 (TRPV1) channel--which essentially contributes to the detection of pain sensation--in rat odontoblasts by immunohistochemical and nystatin perforated patch-clamp techniques. Immunohistochemical observation showed the localization of TRPV1-immunoreactions on the distal regions of odontoblast membranes. In the patch-clamp experiments, we observed capsaicin-induced inward currents that were inhibited by capsazepine, a TRPV1 channel antagonist. Our results indicate a significant expression of TRPV1 channels in odontoblasts, suggesting that odontoblasts may directly respond to noxious stimuli such as a thermal-heat stimulus, and point to the necessity for a reconsideration of the cellular mechanisms of dentin sensation based on the transmembrane ionic signals in odontoblasts.
Cone-beam CT (CBCT) systems specifically designed for hard-tissue imaging of the maxillofacial region have recently become commercially available. The newly-developed CBCT system, CB Throne ® (Hitachi Medical Corp., Tokyo), is characterized by a number of features such as low dose, sub-millimeter spatial resolution, and a small footprint. This system has been clinically applied at Chiba Hospital, Tokyo Dental College, since April 2005. This article reports the characteristics of this system, and its diagnostic power for maxillofacial lesions and the pre-operative planning dental implants.
The objective of this study was to three-dimensionally observe the morphological characteristics of mesiobuccal root canals of Japanese maxillary first molars using microcomputed tomography (Micro-CT) and classify root canal variations. This study used 90 maxillary first molars. Three-dimensional reconstruction was performed using data obtained by Micro-CT, and cross-sections of the root canals were observed. Moreover, the root canal morphology was classified by the configuration and root canal diameter, and was evaluated for occurrence using the classification by Weine et al. (1969) as a reference. Overall, single root canals were observed in 44.4%, incomplete separation root canals in 22.3%, and completely separate root canals (upper and lower separation root canals) in 33.3%. Mesiobuccal root canals often had intricate configurations, and accessory root canals (lateral canals and apical ramifications) were observed in most of the mesiobuccal root canals (76.7%), irrespective of whether there were ramifications of the main root canals. While there were no marked differences in the incidence of root canal ramifications between this study and earlier reports, the incidence of accessory root canals was higher in this study. This result may be explained by the far more superior visualization ability of Micro-CT than conventional methods, which allowed the detection of microscopic apical ramifications previously difficult to observe.
Rat dental pulp RPC-C2A cells, established and kindly provided by Kasugai et al. (1988), were maintained in minimum essential medium (MEM, Invitrogen, Carlsbad, CA, USA) supplemented with 10% heat-inactivated fetal bovine serum (FBS) and 10 mg/mL kanamycin at 37°C in a humidified atmosphere at 5% CO 2 with 20% O 2 . As hypoxic conditions, cells were cultured in a humidified atmosphere at 5% CO 2 with 2% O 2 . Cell Proliferation AssayCells were seeded in 96-well plates at a density of 5 x 10 4 cells/well and cultured for 24 hrs, and then further cultured for an additional 6, 12, or 24 hrs under normoxic or hypoxic conditions. Cell viability was measured by water-soluble tetrazolium salt (WST-1) reduction activity, with a cell counting kit (Dojindo, Kumamoto, Japan). WST-1 was added at a final concentration of 0.5 mM and ABSTRACT AMP-activated protein kinase (AMPK) is a stressresponsive enzyme involved in cell adaptation to an energy crisis. We hypothesized that hypoxia suppresses oxidative phosphorylation and ATP production, resulting in AMPK activation to protect cells. We investigated the effects of hypoxia on cell proliferation, the expression of AMPK and hypoxia-inducible factor 1␣ (HIF-1␣), the activation of AMPK, and the relationship between AMPK and HIF-1␣ expression in rat dental pulp RPC-C2A cells. AMPK in the cells was composed of catalytic ␣1, and regulatory 1 and ␥1 subunit isoforms. Cell proliferation was initially suppressed under hypoxia, but it increased thereafter, together with an increase in the expression of AMPK and HIF-1␣, and the activation of AMPK. Down-regulation of AMPK␣1 by siRNA inhibited cell proliferation under both normoxia and hypoxia, revealing that AMPK induction and activation were required for cell proliferation, although HIF-1␣ expression under hypoxia was not affected.
We experienced two cases of inferior alveolar nerve paresthesia caused by root canal medicaments, which were successfully relieved by microscopic endodontic treatment. In the first case, the paresthesia might have been attributable to infiltration of calcium hydroxide into the mandibular canal through the root canals of the mandibular left second molar tooth. In the second case, the paresthesia might have been attributable to infiltration of paraformaldehyde through the root canals of the mandibular right second molar tooth. The paresthesia was relieved in both cases by repetitive microscopic endodontic irrigation using physiological saline solution in combination with oral vitamin B 12 and adenosine triphosphate.
Aim To investigate the effects of hydrogen peroxide on cell viability and expression and activation of AMP -activated protein kinase (AMPK) in rat dental pulp cell line RPC-C2A.Methodology RPC-C2A cells derived from rat dental pulp were maintained in MEM supplemented with 10% FBS at 37°C, in a humidified atmosphere at 5% CO2. Cells were cultured in the presence or absence of H 2 O 2 for up to 60 min at concentrations of from 0.1 mM to 3.0 mM. Cell viability was analyzed by WST-1 reduction assay. Expression of AMPK subunit isoforms was analyzed by Western blotting using antibodies to the catalytic a1 and regulatory ß1 and ?1 subunit isoforms. T he effect of silencing AMPKa1 on cell viability was determined using siRNA. ResultsExposure to H2O2 decreased cell viability time-and dose-dependently. The catalytic AMPKa 1 subunit and its activated form, phospho-AMPKa , increased with exposure to H2O2 time -and dose-dependently, whereas the regulatory ß1 and ?1 subunits showed no change. D ownregulation of AMPKa 1 resulted in a reduc tion in cell viability in H2O2-treated cells at a concentration of 0.1 mM for 30 min incubation, indicating an increased sensitivity to H 2 O 2 .Conclusions Reactive oxygen induced energy fuel gauge enzyme AMPKa expression and 2 its activation by phosphorylation in RPC-C2A cells, suggesting that AMPK is essential for protection against H 2 O 2 -induced non-apoptotic cell death. Therefore, AMPK may be a therapeutic modulation target for treatment of dentin-pulp complex injured by reactive oxygen.
This study evaluated the wear resistance and sealing property of endodontic temporary restoratives by means of functional stressing using a wear simulator. The pulp chamber of 28 extracted molars was opened and filled with cotton, and then the cavity was filled with a temporary material -Caviton, Temporary Pack, Neodyne-α, or TERM. Specimens were subjected to a wear test, and data for wear and dye penetration were analyzed by one-way ANOVA independently(p<0.05) . Wear values of Neodyne-α(0.09±0.05 mm)and TERM(0.24±0.06 mm)were significantly less than those of Caviton(1.79±0.15 mm)and Temporary Pack(1.02±0.40 mm) . In terms of dye penetration, Neodyne-α leaked significantly less than the other materials at 0.40±0.32 mm. On the other hand, there were no significant differences between TERM(1.30±0.57 mm)and Temporary Pack(2.10±0.12 mm) , and between Caviton(2.60±0.41 mm)and Temporary Pack.
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