Norio Hori

Tokyo Medical and Dental University, Edo, Tōkyō, Japan

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Publications (57)138.78 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The time-dependent degradation of titanium bioactivity (i.e., the biological aging of titanium) has been reported in previous studies. This phenomenon is caused by the loss of hydrophilicity and the inevitable occurrence of progressive contamination of titanium surfaces by hydrocarbons. In this study, we tested the hypothesis that gamma ray treatment, owing to its high energy to decompose and remove organic contaminants, enhances the bioactivity and osteoconductivity of titanium. Titanium disks were acid-etched and stored for 4 weeks. Rat bone marrow-derived osteoblasts (BMOs) were cultured on titanium disks with or without gamma ray treatment (30 kGy) immediately before experiments. The cell density at day 2 increased by 50% on gamma-treated surfaces, which reflected the 25% higher rate of cell proliferation. Osteoblasts on gamma-treated surfaces showed 30% higher alkaline phosphatase activity at day 5 and 60% higher calcium deposition at day 20. The strength of in vivo bone-implant integration increased by 40% at the early healing stage of week 2 for gamma-treated implants. Gamma ray-treated surfaces regained hydrophilicity and showed a lower percentage of carbon (35%) as opposed to 48% on untreated aged surfaces. The data indicated that gamma ray pretreatment of titanium substantially enhances its bioactivity and osteoconductivity, in association with the significant reduction in surface carbon and the recovery of hydrophilicity. The results suggest that gamma ray treatment could be an effective surface enhancement technology to overcome biological aging of titanium and improve the biological properties of titanium implants. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 09/2012; 100(8):2279-87. · 2.31 Impact Factor
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    ABSTRACT: We investigated whether surface roughness and control of surface electric charge of a hydroxyapatite (HA)/titanium oxide (TiO2) hybrid coating could enhance biological responses associated with bone formation. After acid etching, a titanium surface was modified with HA and TiO2 by the dual sputtering deposition technique using radiofrequency sputtering. These surfaces were analyzed for surface roughness and surface electric charge intensity. Rat bone marrow-derived osteoblast-like cells were cultured on HA/TiO2 hybrid surfaces with different electric charges. The attachment and spreading behavior of these cells were significantly increased on the hybrid surface (p<0.05). In vivo experiment, the strength of bone-titanium implant integration with a hybrid surface was 3 times that of a control (p<0.05). The dual sputtering deposition technique created a HA/TiO2 hybrid structure. Our results show that the surface electric charge on a titanium surface is an important factor for enhancing biological responses.
    Dental Materials Journal 05/2012; 31(3):368-76. · 0.81 Impact Factor
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    ABSTRACT: The effects of certain disinfectants on the stability of a polymethyl methacrylate denture base resin were investigated, including those of a novel disinfection method using reactive oxygen species (ROS). The surface roughness and flexural strength were analyzed to assess the effects of the disinfectants on material properties. The following disinfectants were tested: 5% sodium hypochlorite, 70% alcohol, and ROS. Furthermore, the attachment of Candida albicans to the resin surface was investigated. The disinfection method using sodium hypochlorite significantly increased the surface roughness and decreased flexural strength. The surface roughness and flexural strength of the ROS-treated specimens did not significantly differ from those of the control specimens, and the ROS-treated specimens exhibited diminished Candida attachment. These results demonstrate that the ROS disinfection method preserves acceptable material stability levels in polymethyl methacrylate resins.
    Dental Materials Journal 05/2012; 31(3):443-8. · 0.81 Impact Factor
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    Neuroscience Letters. 03/2012; 512(1):59.
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    ABSTRACT: The mechanism by which hydroxyapatite (HA)-coated titanium promotes bone-implant integration is largely unknown. Furthermore, refining the fabrication of nano-structured HA to the level applicable to the mass production process for titanium implants is challenging. This study reports successful creation of nanopolymorphic crystalline HA on microroughened titanium surfaces using a combination of flame spray and low-temperature calcination and tests its biological capability to enhance bone-implant integration. Sandblasted microroughened titanium implants and sandblasted + HA-coated titanium implants were subjected to biomechanical and histomorphometric analyses in a rat model. The HA was 55% crystallized and consisted of nanoscale needle-like architectures developed in various diameters, lengths, and orientations, which resulted in a 70% increase in surface area compared to noncoated microroughened surfaces. The HA was free from impurity contaminants, with a calcium/phosphorus ratio of 1.66 being equivalent to that of stoichiometric HA. As compared to microroughened implants, HA-coated implants increased the strength of bone-implant integration consistently at both early and late stages of healing. HA-coated implants showed an increased percentage of bone-implant contact and bone volume within 50 μm proximity of the implant surface, as well as a remarkably reduced percentage of soft tissue intervention between bone and the implant surface. In contrast, bone volume outside the 50 μm border was lower around HA-coated implants. Thus, this study demonstrated that the addition of pure nanopolymorphic crystalline HA to microroughened titanium not only accelerates but also enhances the level of bone-implant integration and identified the specific tissue morphogenesis parameters modulated by HA coating. In particular, the nanocrystalline HA was proven to be drastic in increasing osteoconductivity and inhibiting soft tissue infiltration, but the effect was limited to the immediate microenvironment surrounding the implant.
    International Journal of Nanomedicine 01/2012; 7:859-73. · 4.20 Impact Factor
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    ABSTRACT: Decreased dopamine (DA) release in the hippocampus may be caused by dysfunctional mastication, although the mechanisms involved remain unclear. The present study examined the effects of soft- and hard-food diets on oxidative stress in the brain, and the relationship between these effects and hippocampal DA levels. The present study showed that DA release in the hippocampus was decreased in rats fed a soft-food diet. Electron spin resonance studies using the nitroxyl spin probe 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl directly demonstrated a high level of oxidative stress in the rat brain due to soft-food diet feeding. In addition, we confirmed that DA directly react with reactive oxygen species such as hydroxyl radical and superoxide. These observations suggest that soft-food diet feeding enhances oxidative stress, which leads to oxidation and a decrease in the release of DA in the hippocampus of rats.
    Neuroscience Letters 12/2011; 508(1):42-6. · 2.03 Impact Factor
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    ABSTRACT: This study addresses the control of the biological capabilities of titanium through specific nanosurface features and its potential modulation by UV photofunctionalization. Rat bone marrow derived osteoblasts were cultured on titanium disks with micropits alone, micropits with 100 nm nodules, micropits with 300 nm nodules, or micropits with 500 nm nodules, with or without UV treatment. After a 24 h incubation protein adsorption, as well as the attachment, retention, and spread of osteoblasts were examined in correlation with the topographical parameters of the titanium substrates. Each of the biological events was governed by a different set of multiple surface topographical factors with a distinctive pattern of regulation. For instance, without UV treatment the protein adsorption and cell attachment capability of titanium substrates increased linearly with increasing average roughness (Ra) and surface area of titanium disks, but increased polynomially with increasing nanonodule diameter. The cell retention capability increased polynomially with increasing nanonodular diameter and Ra, but increased linearly with increasing surface area. Consequently, the micropits with 300 nm nodules created the most favorable environment for this initial osteoblast behavior and response. UV treatment of the nanonodular titanium surfaces resulted in considerable enhancement of all biological events. However, the pattern of UV-mediated enhancement was disproportionate; exponential and overriding effects were observed depending upon the biological event and topographical parameter. As an example of overriding enhancement, the cell retention capability, which fluctuated with changes in various topographical parameters, became invariably high after UV treatment. The present data provide a basis for understanding how to optimize nanostructures to create titanium surfaces with increased biological capabilities and uncover a novel advantage of UV photofunctionalization of titanium substrates that synergistically increases its nanotopography enhanced biological capabilities whereby most of the initial biological events of osteoblasts were overwhelmingly enhanced beyond a simple proportional increase.
    Acta biomaterialia 06/2011; 7(10):3679-91. · 5.09 Impact Factor
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    ABSTRACT: Recent publications reported the time-dependent degradation of bioactivity of titanium which was defined as biological aging of titanium (Att et al., Biomaterials 2009). It is known that the rate of attachment, proliferation, and differentiation of osteogenic cells on titanium surfaces substantially decreases with time (age of titanium) up to 4 weeks after the titanium surfaces are processed. Objectives: The objective of this study was to determine whether the biological aging of titanium continues in a longer term of up to 6 months. Methods: Commercially pure titanium discs were acid-etched and used immediately after processing (fresh surface) for experiments, or after storing in dark for 1 month (1-m-old surface), 3 months, or 6 months. Rat bone marrow-derived osteoblasts were seeded onto these differently aged titanium discs. The number of attached cells and cell density were evaluated by WST-1 assay. Cell spreading behavior along with the expression of a focal adhesion protein, vinclulin, was examined using confocal laser microscopy. Alkaline phosphatase (ALP) activity of cells was also assessed. Results: The number of attached cells after 3 h incubation was 30% lower on 1-m-old surfaces and 40% lower on 6-m-old surfaces compared to fresh surfaces (p<0.05). The cell density measured at day 3 was reduced in correlation to the age of titanium. ALP activity, which was dropped by 35% on 1-m-old surfaces compared to fresh surfaces, was further reduced by another 12% on 6-m-old surfaces. The area of cell spread and the vinculin expression evaluated 3 h after seeding showed a significant progressive reduction as titanium surfaces aged. Conclusions: There found a significant continuing reduction of biological capability of titanium over 1 month up to 6 months period of time after processing, which included the reduced capability of cell attraction and inducing osteoblastic functional phenotype.
    IADR General Session 2011; 03/2011
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    ABSTRACT: Objectives: Nanostructuring technologies have proven to create unique biological properties of various materials. Particularly, the creation of nanoscale topography together with microscale topography may provide an additional functionality of materials while preserving the advantages of microscale features. The objective of this study was to examine the osseointegration capability of a newly created micro-nano-hybrid titanium surface, consisting sandblast-created microtopography and alkaline- and heat-created nanotufted structures, in comparison with a surface with microtopography alone. Methods: Cylindrical implants (1 mm in diameter and 2 mm in length) were prepared by sandblasting the surfaces with or without further alkaline and heat treatment (JMM: Japan Medical Materials Corp.). Ti-6Al-4V and Ti-15Mo-5Zr-3Al were used as a base material. Implants, placed into rat femur, were examined for peri-implant bone morphogenesis using histomorphometry and for the strength of osseointegration using an implant biomechanical push-in test (n=6). Results: Alkaline and heat treatment of both titanium alloys resulted in a formation of unique micro-and-nano-hybrid morphology, consisting of sandblast-created microtopography and alkaline- and heat-created tufts of nanospheres (nanotufted surface), having a great contrast with the surface created by sandblasting alone (microtopography surfaces). Push-in values for nanotufted Ti-15Mo-5Zr-3Al implants was 70% greater than for microtopography implants at week 2 of healing. The difference (50%) remained significant at week 4. The bone-implant contact at week 2, which was 29% for microtopography surfaces, increased to 57% for nanotufted surfaces. The bone-implant contact was 72% for nanotufted surfaces at week 4, while the one for microtopography surfaces was 51%. Similar higher osseointegration capability was found for nanotufted Ti-6Al-4V surfaces. Conclusion: A combination of sandblasting and alkaline- and heat-treatment of titanium alloy create unique nanotufted structures along with microtopography. These micro-nano-hybrid surfaces are capable of not only accelerating the process but also elevating the degree of osseointegration compared to surfaces with microtopography alone.
    IADR General Session 2011; 03/2011
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    ABSTRACT: Objective: There are several studies regarding the development and modification of titanium surfaces by coating with proteins for enhanced osseointegration and better titanium-cell interactions. We recently discovered a natural decrease of biological capability of titanium over time (J Dent Res 88: 663-7, 2009). The objective of this study was to determine whether the timing of protein coating (i.e., coating applied to fresh or aged titanium) affects the amount of protein adsorption to titanium and the attachment and functional phenotype of osteoblasts. A hypothesis tested was that coating freshly prepared titanium surfaces is more efficient and effective to create cell-attractive surfaces than coating aged titanium surfaces. Materials and methods: We prepared titanium disks with a machined surface and used immediately (fresh) or 4 weeks (4-w-old) after storing in the dark. Fibronectin was coated onto these titanium disks by incubating them for 3 hours. Rat bone marrow-derived osteoblasts were cultured to examine initial cell attachment (24 h), spreading behavior, and alkaline phosphatase (ALP) activity. Results: Fresh titanium surfaces adsorbed 70% greater amount of fibronectin than 4-w-old surfaces. Coating titanium surfaces with fibronectin substantially increased the number cells attached to titanium regardless of their age. However, the number of cells attached to fibronectin-coated fresh titanium was 70% greater than that for fibronectin-coated 4-w-old titanium. Cells spread most rapidly on fibronectin-coated fresh titanium. Likewise, ALP activity was high in order of fibronectin-coated fresh surface, fibronectin-coated 4-w-old surface, uncoated fresh surface, uncoated 4-w-old surface. Conclusion: The age of titanium surfaces (fresh or old after processing) considerably affects the efficiency of protein coating, which leads to the different degrees of osteoblast attraction and function. Applying protein coating to freshly prepared titanium surfaces is assumed to be most efficient and effective.
    IADR General Session 2011; 03/2011
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    ABSTRACT: Initial cell adhesion to titanium is an important step for establishing osseointegration. We previously reported that advancement of cell adhesion to a UV-treated titanium was associated with UV light-catalytic hydrophilic conversion of the titanium surface. However, the physiological response and behavior of cells via intracellular signal transduction across these physicochemical linkages remain unknown. We hypothesized that UV-treated titanium enhances activation of adhesion-related signaling by virtue of its hydrophilic surface. Objectives: This study aimed to examine the intracellular response with respect to attachment, spreading and motility of osteoblastic cells. Methods: Rat bone marrow-derived osteoblastic cells were cultured for 3 h or 24 h on acid-etched titanium disks with or without UV light pretreatment. The wettability nature of the titanium surfaces was examined by the contact angle of 10 l H2O. Spread and cytoskeletal development were evaluated by confocal microscopic image-based cytomorphometry with actin filament staining. The activated intracellular signal transduction was evaluated by quantifying paxillin-mediated signaling with Western blotting. Gene expression of the Rho family of small GTPasesRac, Rho and Cdc42was assessed by a RT-PCR. Results: Wettability of UV-treated titanium disks showed superhydrophilic property. Cells on the UV-treated surfaces were larger with well-developed cell processes filled with organized actin filaments compared to those of the non-UV-treated disks. Intracellular signaling transduction, determined by the phosphoTyr31-paxillin/paxillin ratio, was increased from 25% to 50% by UV treatment. Gene expression of Cdc42 on the UV treated surface was 2- and 2.5-fold greater than that on the untreated surface after 3 h and 24 h incubations, respectively. In addition, gene expression of Rac increased 70% on the UV-treated surface. Conclusion: UV treated titanium enhanced intracellular response in osteoblasts via UV-induced superhydrophilicity, which may have expedited spread and cytoskeletal development, and increased paxillin-mediated signal transduction and subsequent activation of small GTPase Rho family members.
    IADR General Session 2011; 03/2011
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    ABSTRACT: Objectives: There are few reports about relationship between the mastication and the oxidative stress. The aim of this study was to investigate the effects of alteration with the food textures on the oxidative stress and neurotransmitter release in hippocampus of rat. Methods: We divided the animal (3 weeks male Wistar rats) into three experimental groups; 1) hard food (HF) group (12 weeks), 2) soft food (SF) group (12 weeks), 3) mix food (MF) group (soft food for 10 weeks, and then hard food for 2 weeks). We assessed oxidative stress in the brain using the in vivo L-band electron spin resonance (ESR) technique and dopamine (DA) release in the hippocampus using a microdialysis. We measured the scavenge activity of hydroxyl radical (HO.) by DA using in vitro X-band ESR technique. All groups were measured the weight after end of experimental period. Statistical analyses were performed Student's t-test and post hoc test. Results: There were no significant differences in weight between each group. The significant increase of oxidative stress in the brain (P<0.05) was observed in SF and MF group. SF group had the significant decrease in DA release in the hippocampus. In addition, DA significantly deceased on HO. generation in vitro. Conclusions: We demonstrated that the treatment with SF induced oxidative stress in the brain, and that they reduced DA release in hippocampus. Further, DA had a scavenge activity on HO. generation system, directly. These results suggested that HO. generated by change of mastication with the differences of food textures was reduced DA in hippocampus, and it was likely that they may be induced the adverse effects of brain function.
    IADR General Session 2010; 07/2010
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    ABSTRACT: Objective: The senescence-prone (SAMP8) mouse is a non-genetically manipulated rodent model of Alzheimer's disease. Amyloid-beta (Aβ) protein accumulates in the hippocampus as these mice age. We have previously shown that reduced mastication due to molar extraction impairs hippocampal-dependent spatial learning in this mouse strain. Whether or not there is a correlation between the amount of Aβ protein and the degree of cognitive impairment caused by the reduced mastication is not clear. To address this issue, we measured the amount of Aβ protein in the hippocampus of molar-intact and molarless SAMP8 mice with an Enzyme-Linked ImmunoSorbent Assay (ELISA). Methods: We extracted all upper molar teeth of an experimental group of 8-week-old male SAMP8 mice (molarless group, n=13). A control group of SAMP8 mice of the same age had no treatment (molar-intact group, n=14) except anesthesia. We killed each mouse at 12 weeks of age and immediately tested its hippocampus with an ELISA to quantify the amount of Aβ protein. Results: The mean amount of Aβ protein in hippocampi of mice in the molarless group was 12.6 ± 0.2 pmol/l , which was significantly more than that of the control group (11.1 ± 0.4 pmol/l). Conclusion: The present result suggests that the molarless condition promotes an accumulation of Aβ protein in the hippocampus of the SAMP8 mice, thereby impairing cognitive function.
    IADR General Session 2010; 07/2010
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    ABSTRACT: Titanium surfaces with nano-micro-hybrid structures were previously demonstrated to show higher biological capability than surfaces with microtopography alone. Also, we have shown that UV light treatment of titanium surfaces enhances substantially their bioactivity. However, potential synergistic effects of nano-micro-hybrid surfaces and UV treatment have never been addressed. Objectives: This study assesses biological capability of UV-treated nano-micro-hybrid titanium surfaces. Method: Four different titanium surfaces were created: acid-etched surface as a micropit surface; titanium dioxide (TIO2) depositioned surfaces onto the acid-etched surface with 3 different deposition time which created 100-nm, 300-nm, and 500-nm nodules, respectively, within the micropits. Untreated and UV-treated titanium surfaces were compared for albumin adsorption, attachment, proliferation and mineralization of bone marrow-derived osteoblasts. Results: The surfaces treated UV on nano-micro-structure significantly increased the albumin absorption during 2 hours incubation, among which 300nm nodules with UV showed a highest number. Such difference remained significant even after 24 h incubation. At day 5, UV treatment of micro-nano-hybrid surfaces increased ALP activity more than 2-fold regardless of the size of nanonodules. Micro-nano-hybrid surfaces with 300-nm nodules showed the highest number. The amount of calcium deposition evaluated at day 14 was also increased on UV-treated micro-nano-hybrid surfaces. The effect of UV was more pronounced on micro-nano-hybrid surfaces than on surfaces with micropits alone. Conclusion: UV treatment of micro-nano-hybrid titanium surfaces considerably enhanced their biological capability. However, the effect was disproportionate with the size of nanonodules. Microtopography with 300 nm nodules showed the highest UV responsiveness.
    IADR General Session 2010; 07/2010
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    ABSTRACT: Recently, time-dependent degradation of titanium bioactivity, termed as biological aging of titanium, was reported. This phenomenon is caused by progressive contamination of hydrocarbons onto titanium surfaces. Currently, there is no means available to prevent this adverse event. Objectives: We tested a hypothesis that gamma-ray treatment of titanium enhances bioactivity and osteoconductivity of titanium due to its high energy to decompose and remove organic contaminants. Methods: Titanium disks were acid-etched and stored for 4 weeks. Rat bone marrow-derived osteoblasts were cultured on titanium disks with or without gamma-ray treatment (30 kGy) immediately before experiments. The attachment, spread, proliferation, alkaline-phosphatase (ALP) activity, and mineralizing capability of cultured osteoblasts were evaluated. The strength of in vivo osseointegration was evaluated by biomechanical implant push-in test in a rat model. X-ray photoelectron spectroscopy was used to quantify atomic elements on titanium surfaces. Results: The number of attached cells after 24 h of culture increased by 25% on gamma-ray-treated titanium surfaces compared to untreated surfaces (Bonferroni, p<0.05). After 3 h, cells were larger on gamma-ray-treated surfaces with their cyto-projections stretched and actin fibers formulated, whereas cells on untreated surfaces remained circular. The cell density at day 2 increased by 50% on gamma-treated surfaces (p<0.05), which was supported by 25% higher rate of cell proliferation. Osteoblasts on gamma-treated surfaces showed 30% higher ALP activity at day 5 and 60% higher calcium deposition at day 20 (p<0.01). The push-in valueincreased by 40% at early healing stage of week 2. Gamma-ray treatment reduced the atomic ratio of carbon from 50% to 37%. Conclusion: Gamma-ray treatment of titanium significantly enhanced its bioactivity and osseointegration capability. If it would be applied immediately before the use of titanium implants, it could be an effective surface enhancement technology to overcome biological aging of titanium.
    IADR General Session 2010; 07/2010
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    ABSTRACT: Ultraviolet (UV)-photofunctionalization of titanium to enable the establishment of a nearly complete bone-implant contact was reported recently. However, the underlying mechanism for this is unknown. We hypothesized that UV-treated titanium surfaces acquire distinct electrostatic properties that may play important roles in determining the bioactivity of these surfaces. The objective of this study was to determine the protein adsorption capability of UV-treated titanium surfaces under various electrostatic environments. The amount of albumin adsorbed on UV-treated and untreated titanium disks was evaluated under different pH conditions above and below the isoelectric points of albumin and titanium. The effects of additional treatment with various ionic solutions were also examined. Albumin adsorption on UV-treated surfaces at pH 7.0 was considerably greater (6-fold after 3h of incubation and 2.5-fold after 24h) than that to UV-untreated surfaces. UV-enhanced albumin adsorption was abrogated at pH 3.0 or when these titanium surfaces were treated with anions, while maintaining UV-induced superhydrophilicity. Albumin adsorption on UV-untreated titanium surfaces increased after treating these surfaces with divalent cations but not after treating them with monovalent cations. These results indicated that UV-treated titanium surfaces are electropositively charged as opposed to electronegatively charged UV-untreated titanium surfaces. This distinct UV-induced electrostatic property predominantly regulates the protein adsorption capability of titanium, superseding the effect of hydrophilic status, and converts titanium surfaces from bioinert to bioactive. As a result, direct titanium-protein interactions take place exclusively on UV-treated titanium surfaces without the aid of bridging ions.
    Acta biomaterialia 05/2010; 6(10):4175-80. · 5.09 Impact Factor
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    ABSTRACT: In many cases, dentists try to manage denture pain by adjusting dentures. However, some patients complain of oral discomfort over a long period even after appropriate denture adjustments. In some of these situations, simple denture adjustment does not alleviate the discomfort of these patients. It is known that denture stomatitis may occur in response to plaque accumulation on dentures. One of the chief pathogenic microorganisms causing this type of inflammation is Candida albicans. A common symptom of oral candidiasis is pain in the oral mucosa complicated by angular stomatitis. In this paper, we report a case of oral candidiasis that was diagnosed and managed based on the patient's complaints.
    Journal of prosthodontic research. 04/2010; 55(1):48-52.
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    ABSTRACT: The mechanism underlying the recently found photofunctionalization of titanium is unknown. We focused on how the initial interaction between the cells and photofunctionalized titanium is enhanced at a molecular-level and the role played by the electrostatic status of the titanium surfaces in the possible regulatory mechanism for determining their bioactivity. Rat bone marrow-derived osteoblasts were cultured on untreated and ultraviolet (UV)-treated titanium surfaces. UV treatment converted the titanium surfaces from hydrophobic to superhydrophilic. The number of osteoblasts attached to UV-treated titanium surfaces was substantially greater than that attached to untreated surfaces (5-fold and 2-fold after 3 and 24 h of incubation, respectively). Osteoblasts cultured for 3 and 24 h on these titanium surfaces were detached mechanically by vibrational force and enzymatically by trypsin treatment. Cell adhesion evaluated by the percentage of remaining cells after these detachments was substantially greater for cells on UV-treated titanium surfaces compared to untreated titanium surfaces (110-120% greater for cells incubated for 3 h and 50-60% greater for cells incubated for 24 h). Osteoblasts on UV-treated surfaces expressed more vinculin. UV-enhancing effect in cell adhesion was also demonstrated under a serum-free condition. UV-enhanced cell adhesion was abrogated when the UV-treated titanium surfaces were electrostatically neutralized by either removing the electric charge or masking with monovalent anions, while the surfaces maintained superhydrophilicity. In conclusion, the establishment of osteoblast adhesion is accelerated and augmented remarkably on UV-treated titanium surfaces, associated with upregulated expression of vinculin. This study has identified an electrostatic property of UV-treated titanium surfaces playing a regulatory role in determining their bioactivity, superseding the effect of the hydrophilic nature of these surfaces. A mechanism underlying the UV-induced conversion of titanium from bioinert to bioactive, in which direct cell-titanium interaction is exclusively enabled, is proposed.
    Biomaterials 04/2010; 31(10):2717-27. · 8.31 Impact Factor
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    ABSTRACT: The osseointegration capability of titanium decreases over time. This phenomenon, defined as biological aging of titanium, is associated with the disappearance of hydrophilicity and the progressive accumulation of hydrocarbons on titanium surfaces. The objective of this study was to examine whether coating of titanium surfaces with 4-(2-Hydroxylethyl)-1-piperazineethanesulfonic acid (HEPES) buffer, a nonvolatile zwitterionic chemical buffering agent, could prevent the time-dependent degradation of the bioactivity of titanium. Commercially pure titanium samples, prepared as disks and cylinders, were acid-etched with H(2)SO(4). A third of the samples were used for experiments immediately after processing (new surfaces), while another third were stored under dark ambient conditions for 3 months (3-month-old surfaces). The remaining third were coated with HEPES after acid-etching and were stored for 3 months (HEPES-coated 3-month-old surfaces). The 3-month-old surfaces were hydrophobic, while new and HEPES-coated 3-month-old surfaces were superhydrophilic. Protein adsorption and the number of osteoblasts attached during an initial culture period were substantially lower for 3-month-old surfaces than for new and HEPES-coated 3-month-old surfaces. Alkaline phosphatase activity and calcium deposition in osteoblast cultures were reduced by more than 50% on 3-month-old surfaces compared to new surfaces, whereas such degradation was not found on HEPES-coated 3-month-old surfaces. The strength of in vivo bone-implant integration for 3-month-old implants, evaluated by the push-in test, was 60% lower than that for new implants. The push-in value of HEPES-coated 3-month-old implants was equivalent to that of new implants. Coating titanium surfaces with HEPES containing an antioxidant amino acid derivative, N-acetyl cysteine (NAC), further enhanced osteoblast attachment to the surfaces, along with the increase level of intracellular glutathione reserves as a result of cellular uptake of NAC. These results suggest that HEPES coating of titanium surfaces maintained their superhydrophilicity for at least 3 months and resulted in a continuous retention of bioactivity and osteoconductivity similar to freshly prepared surfaces. This coating technology may be useful for preventing biological aging of titanium and delivering biological molecules for synergistic enhancement of bone-titanium integration.
    Biomaterials 03/2010; 31(18):4818-28. · 8.31 Impact Factor
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    ABSTRACT: Lack of cytocompatibility in bone substitutes impairs healing in surrounding bone. Adverse biological events around biomaterials may be associated with oxidative stress. We hypothesized that a clinically used inorganic bone substitute is cytotoxic to osteoblasts due to oxidative stress and that N-acetyl cysteine (NAC), an antioxidant amino acid derivative, would detoxify such material. Only 20% of rat calvaria osteoblasts were viable when cultured on commercial deproteinized bovine bone particles for 24 hr, whereas this percentage doubled on bone substitute containing NAC. Intracellular ROS levels markedly increased on and under bone substitutes, which were reduced by prior addition of NAC to materials. NAC restored suppressed alkaline phosphatase activity in the bone substitute. Proinflammatory cytokine levels from human osteoblasts on the bone substitute decreased by one-third or more with addition of NAC. NAC alleviated cytotoxicity of the bone substitute to osteoblastic viability and function, implying enhanced bone regeneration around NAC-treated inorganic biomaterials.
    Journal of dental research 03/2010; 89(4):411-6. · 3.46 Impact Factor

Publication Stats

519 Citations
138.78 Total Impact Points

Institutions

  • 2012
    • Tokyo Medical and Dental University
      Edo, Tōkyō, Japan
    • Nihon University
      Edo, Tōkyō, Japan
  • 2009–2012
    • Kanagawa Dental College
      • • Department of Oral and Maxillofacial Rehabilitation
      • • Department of Clinical Care Medicine
      Yokosuka, Kanagawa-ken, Japan
  • 2009–2011
    • University of California, Los Angeles
      • Center for Reconstructive Biotechnology
      Los Angeles, California, United States
  • 2010
    • Tokyo Dental College
      Japan