Dental Journal of Iwate Medical University
Online ISSN : 2424-1822
Print ISSN : 0385-1311
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  • Chie ENDO, [in Japanese], Shigenobu KIMURA, [in Japanese], [in Japanes ...
    Volume 43 (2018) Issue 1 Pages 1-11
    Released: June 13, 2018
    JOURNALS FREE ACCESS

    Objectives: Although it was reported that preoperative oral care could reduce the risk of postoperative infections, the inhibitory effect of oral care on bacterial adhesion to endotracheal tubes remains to be elucidated. In this study, we assessed the number of total bacteria and oral streptococci on the extubated endotracheal tubes after surgery with / without preoperative oral care.

    Materials and Methods: Fifty-three extubated endotracheal tubes were obtained after surgery from 20 patients with preoperative oral care (OC group) and 33 patients without oral care (NOC group). The oral care consisted of professional mechanical tooth cleaning (PMTC) performed 7 days and 1 day before surgery. Whole saliva was obtained from all the patients on the morning of surgery. The extubated tubes were washed twice with sterile phosphate-buffered saline and then vortexed. The bacterial suspensions and saliva samples were plated onto blood agar plates and Mitis-Salivarius agar plates. After 48 hours incubation under anaerobic conditions, the total bacteria and oral streptococci were counted. In vitro, the adhesive ability of oral streptococcal species to endotracheal tubes was examined using 7 laboratory strains of oral streptococci.

    Results: Bacteria totaling more than 103 CFU per tube were detected in all the samples, and oral streptococci were predominant. The numbers of total bacteria and oral streptococci adhering to the tubes in the OC group were significantly lower than those in the NOC group. However, there was no significant correlation in either group between the numbers of bacteria (total bacteria and oral streptococci) on the endotracheal tube and those in the saliva samples, suggesting that the plaque streptococci could preferentially adhere to the tube. Furthermore, the in vitro adhesion assay revealed that mutans streptococci have the highest adhesive ability to endotracheal tubes.

    Conclusion: Significant number of bacteria, especially oral streptococci including mutans

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  • Tomohiko MURAKAMI
    Volume 43 (2018) Issue 1 Pages 12-23
    Released: June 13, 2018
    JOURNALS FREE ACCESS

    Denture adhesives improve denture retention, stability and masticatory function. However, the effects of denture adhesives on oral microorganisms have not been elucidated. This study aimed to investigate the effects of three different forms of denture adhesives (cream, powder and cushion forms) on the pathogenicity of Porphyromonas gingivalis. To this end, the number of adherent P. gingivalis, scanning electron microscope (SEM) images of biofilm formation on the surface of specimens, and gingipain activity were examined. In this in vitro study, P. gingivalis strain ATCC33277 suspension was seeded on acrylic resin and each type of denture adhesive, and incubated for 2 hours at 4 ℃. The number of P. gingivalis adherent to the resin/ denture adhesives was quantified using a quantitative real-time PCR assay. Then, to simulate conditions of use for denture adhesives, the specimens of adherent P. gingivalis were incubated for 1,2,3,6,12 and 24 hours at 37 ℃ in ABCM medium. The number of adherent P. gingivalis at the end of each incubation period was quantified, and the surfaces of the specimens were examined under a SEM. Gingipain activity was examined using a fluorescence assay. The degree of initial adhesion was significantly higher with cream and powder adhesives. The number of adhered P. gingivalis increased with time, however, the slower growth rate was shown after an incubation period of 12 hours. In cream and powder adhesives, biofilm formation was observed by SEM. For all the denture adhesives, high Arg-gingipain activities were observed after 6 hours. Our results indicate that denture adhesives likely enhance the pathogenicity of P. gingivalis.

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  • Hiroaki SATOH
    Volume 43 (2018) Issue 1 Pages 24-35
    Released: June 13, 2018
    JOURNALS FREE ACCESS

    The McGill consensus statement determined in 2002 that a two-implant overdenture (2- IOD) should be the first choice of treatment for an edentulous mandible. In recent years, some researchers have reported on the success rate of 2-IOD supported by dental implant and stress analysis in a simulation model. However, there are indefinite factors such as denture base morphology, the number of artificial teeth, occlusal scheme and selection of attachment. We focused on locator attachments installed on 2-IOD and applied the edentulous jaw model. This study aimed to elucidate the influence on the residual ridge of different retention force of the mandibular implant overdenture in locator attachments.

    Two implants (Φ3.75 mm × 11.5 mm, Bränemark System® Mk Ⅲ Groovy RP, Nobel Biocare, Kloten, Switzerland) were placed at areas equivalent to the bilateral canines of an experimental jaw model and fabricated 2-IOD. Six miniature pressure sensors were embedded in the experimental denture to measure pressure in the bilateral buccal premolar regions, the bilateral buccal shelves, and the bilateral lingual molar regions. The load on the experimental dentures was set at 50 N with reference to the masticatory force of complete denture (CD) wearers. Measurements were performed using retention discs of different retention forces. The experimental CD was fabricated as a control.

    Under the bilateral load conditions, the mucosal pressures exerted by 2-IOD were significantly lower in all sites with 2-IOD than with CD. Under the unilateral load conditions, the mucosal pressures exerted by 2-IOD were significantly lower in the buccal premolar regions and the buccal shelves (support regions of the denture).

    The results of this study revealed that when the same occlusal force is exerted in the case of CD or 2-IOD, locator attachments should reduce the impacts on residual ridge.

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  • Ayaka NAKASATO
    Volume 43 (2018) Issue 1 Pages 36-47
    Released: June 13, 2018
    JOURNALS FREE ACCESS

    The purpose of the present study was to evaluate the effect of bite force improvement after denture treatment on brain activity in elderly edentulous people.

    Subjects were edentulous patients aged 65 and older, who visited the Iwate Medical University Hospital Dental Center with a chief complaint of inconvenience of their complete dentures( Old dentures). Seventeen subjects were judged to need new complete dentures by a prosthodontist were included in this study. After the evaluation, the prosthodontist made new dentures. Oral function was evaluated by bite force and brain activity was examined with f MRI. The task paradigm for f MRI was an alternation between 30 seconds of chewing gum and 30 seconds of rest, and the procedure was repeated three times in each scanning session. The old denture (OD) condition and the new denture (ND) condition were compared.

    Both bite force and brain activity with the ND were significantly increased compared with OD. Chewing gum was associated with activity in the temporal pole, inferior parietal lobe, frontal lobe, insula lobe, temporal lobe, hippocampus, precuneus and cerebellum. Bite force was associated with activity in the cerebellum, temporal lobe, frontal lobe, insula lobe, precentral gyrus, postcentral gyrus, putamen, thalamus and parahippocampus gyrus.

    In edentulous elderly people, bite force improvement was associated with higher brain activity in the frontal lobe and parahippocampus gyrus, and thus might contribute to maintain cognitive function.

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  • Manami NAKASATO, Yu SHIMOYAMA, Yuko OHARA-NEMOTO, Daisuke SASAKI, Taka ...
    Volume 43 (2018) Issue 1 Pages 48-60
    Released: June 13, 2018
    JOURNALS FREE ACCESS

    Periodontitis is known as a risk factor for type 2 diabetes mellitus (T2DM). However, the molecular mechanism is still unclear. The incretin peptides, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide, are major regulators of post-prandial insulin secretion, which are rapidly degraded to inactive forms with the cleavage of Ala2-Glu3 bond by dipeptidylpeptidase 4 (DPP4). Recent studies demonstrated that Porphyromonas gingivalis, one of the major causative organisms of chronic periodontitis in humans, possesses DPP4. Since the prokaryotic DPP4 is a homologue to mammalian DPP4, it is possible that periodontopathic bacterial infection could lead to the onset or progression of type 2 diabetes mellitus through the degradation of incretins by those DPP4s. In this study, we assessed the cell-associated DPP4s and their GLP-1-hydrolyzing activity in periodontopathic bacteria. The results indicated that, among the 6 periodontopathic bacteria tested, P. gingivalis, Tannerella forsythia and Prevotella intermedia possess cell-associated DPP4, which can hydrolyze GLP-1 to the inactive form. In addition, further characterization of T. forsythia DPP4 (TfDPP4) using recombinant TfDPP4 indicated that TfDPP4 has a similar amino acid sequence and molecular profiles (molecular mass, the isoelectric point, pH- and salt-dependences) to P. gingivalis DPP4 (PgDPP4).

    In conclusion the present findings indicate that some periodontopathic bacteria can possess functional DPP4 associated with its cell surface that can degrade incretins as does human DPP4, and thus periodontitis with periodontopathic bacterial infection could be an important risk factor for T2DM.

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  • Maiko Maiko OHTA, Akira NEMOTO, Naoyuki CHOSA, Seiko KYAKUMOTO, Seiji ...
    Volume 43 (2018) Issue 1 Pages 61-73
    Released: June 13, 2018
    JOURNALS FREE ACCESS

    Sensory neurons in the periodontal ligament (PDL) transmit the impulses, which are generated by the mechanical stimulation of the tooth, into the trigeminal ganglion, resulting in the excitement of the nucleus ventralis posteromedialis of the thalamus. When sensory neurons are injured, the neurites become atrophied and degenerated. Nerve growth factor (NGF) belonging to neurotrophic factors plays important roles in neurite extension and regeneration of injured sensory neurons. We evaluated how the major component of the outer membrane of gram-negative bacteria, lipopolysaccharide (LPS), affected transforming growth factor-beta1 (TGF- β1)-induced NGF expression in rat PDL-derived fibroblasts SCDC2 cells. qRT-PCR and ELISA analyses showed that LPS suppressed TGF- β1-induced NGF synthesis through the activation of Toll-like receptor 4 (TLR4). In addition, inhibitor of κB (I- κB) kinase-2 (IKK-2) inhibitor, TPCA-1, abrogated LPSinduced suppression of TGF- β1-promoted NGF expression. Intriguingly, western blotting showed that LPS inhibited TGF- β1-induced activation of p38 mitogen-activated protein kinase (MAPK) that mediated TGF- β1-induced intra-cellular signal transduction for NGF expression. These results suggested that TLR4-mediated signaling activated by LPS suppresses TGF- β1-induced NGF expression in PDL fibroblasts by inhibiting TGF- β1-induced p38 MAPK activation in a nuclear factor- κ B-dependent manner, possibly resulting in the suppression of the regeneration of injured PDL neurons. (194 words)

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  • Akihiro FUKUTOKU
    Volume 43 (2018) Issue 1 Pages 74-82
    Released: June 13, 2018
    JOURNALS FREE ACCESS

    The purpose of this study was to analyze the amount of wear with an intra-oral scahher in order to observe the wear process on implant superstructures.

    This study included 30 patients who gave informed consent. Implant superstructures and antagonists on the first molar were captured with an intra-oral scanner (3M true definition scanner, 3M, St. Paul, MN, USA) when they were placed, and again 3 months later. Scanned data were imported to an image measuring program (GOM Inspect, GOM, Brunswick, Germany) and saved as STL files. Subsequently, the scanned data just after placement were compared with those after 3 months. The deviation of structural changes in functional cusps of first molars was calculated as the amount of wear. The statistical analysis was performed with the statistical analyze software (IBM SPSS, Armonk, IBM, NY, USA).

    The mean amount of wear on implant superstructures was 76 ± 30 ㎛ for Zirconia(Zr) and 71 ± 27 ㎛ for Hybrid Composite Resin(HC). There were no significant differences between the two groups. The mean loss of height on the antagonist tooth was 58 ± 25 ㎛for Zr and 60 ± 20 ㎛ for HC. There were no significant differences between these groups. Moreover, there were no significant differences in wear between screw-retained superstructure and cement-retained ones. However, superstructure wear for men was significantly larger than that for women (p<0.05).

    The accuracy of the intra-oral scanner was adequate for measuring the amount of wear. Thus, this measuring system could be useful for observing the morphological change of implant superstructures. There were no differences between the wear on implant superstructures made of Zr and those made. Therefore, those results indicated that Zr which was adjusted and polished properly could be applicable for implant superstructures. Moreover, there were differences between the wear of the men group and the women group, indicating that the occlusal force affected the results.

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  • Mami CHIKUDA, Shigeharu JOH, Kenichi SATO
    Volume 43 (2018) Issue 1 Pages 83-96
    Released: June 13, 2018
    JOURNALS FREE ACCESS

    When added to local anesthetics, dexmedetomidine has been shown to increase the local anesthetic effect, decrease local blood flow, and suppress inflammation. However, the effects and mechanism of action of dexmedetomidine on lingual arteries have not been determined. The aim of this study was to investigate the effect of dexmedetomidine on lingual arterial vascular smooth muscle, evaluating changes in contraction tension and intracellular calcium ion concentration [Ca2+]i. Endothelium-denuded lingual arteries were sliced into 2- to 3-mm rings. Specimens were loaded with a fluorescent calcium indicator. Changes in isometric contraction tension and [Ca2+]i were measured with the addition of various substances at various concentrations, under different conditions of baseline stimulation (with KCl, adrenaline, caffeine, or histamine) ,and under conditions of intra or extracellular calcium store depletion. Dexmedetomidine increased the contraction tension and [Ca2+]i induced by high-KCl depolarization. Dexmedetomidine inhibited receptor-activated Ca2+ channels and phosphatidylinositol-1,4,5- triphosphate-induced Ca2+ release, but not Ca2+-induced Ca2+ release. The findings of the present study elucidate the effects and mechanism of action of dexmedetomidine on vascular smooth muscle. This information will be useful in the development of dexmedetomidine-containing local anesthetics that are safe for use in patients with cardiovascular compromise.

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