Norio Hori

Tokyo Medical and Dental University, Edo, Tōkyō, Japan

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Publications (43)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: 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
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    ABSTRACT: The objective of this study was to determine whether ultraviolet (UV) light treatment of titanium implants could enhance osseointegration to sufficiently overcome the negative aspects of shorter implants in a rat femur model. Acid-etched miniature titanium implants with lengths of 2 mm (longer implants) and 1.2 mm (shorter implants) were prepared. Some of these implants were treated with UV light for 48 hours prior to surgery. The strength of osseointegration generated by these implants was evaluated using a biomechanical implant push-in test in a rat model. Peri-implant osteogenesis was examined by scanning electron microscopy for tissue morphology and energy dispersive x-ray spectroscopy for elemental composition. Push-in test values for the longer implants were 80% and 100% greater than those of the shorter implants at weeks 4 and 8 of healing, respectively. UV treatment of the shorter implants significantly increased their push-in value, resulting in a 100% higher value than untreated longer implants at week 2 and a push-in value that was equivalent to that of the untreated longer implants at weeks 4 and 8. Scanning electron micrographs and energy dispersive x-ray spectroscopic examinations after push-in testing revealed that the UV-treated implant surfaces were covered more extensively by bone or tissue remnants containing calcium and phosphorous than the untreated surfaces. The titanium surfaces were converted from hydrophobic to superhydrophilic status after UV treatment, although the cause-result relationship between the acquired superhydrophilicity and biologic effects remained unclear. Within the limits of this investigation, UV light pretreatment substantially enhanced the osseointegration capacity of acid-etched titanium implants. The deficiencies of osseointegration in implants with a 40% shorter length were overcome by UV treatment in the rat model using miniature implants. These results need to be confirmed in other animal models and implants that more closely resemble human dental implants to determine the true clinical significance.
    The International journal of oral & maxillofacial implants 01/2010; 25(2):287-94. · 1.91 Impact Factor
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    ABSTRACT: The objectives of this in vitro study were to determine whether the commercial collagen material used in bone augmentation procedures induces oxidative stress-mediated adverse effects on the viability and function of osteoblasts and to determine whether N-acetyl cysteine (NAC), an antioxidant amino acid derivative, can alleviate these effects. Commercial collagen sponge (Collaplug) and membrane (BioGide) were treated with NAC. Rat calvaria-derived osteoblasts were directly seeded on these materials with or without NAC pretreatment. Cytotoxic evaluation was performed by flowcytometric cell viability assay, confocal laser microscopic analysis of attached cell morphology and reactive oxygen species (ROS) localization, and alkaline phosphatase staining. Cell viability was less than 40% on both collagen sponge and membrane 24 hours after seeding and increased to 50% with NAC pretreatment. Cell death was characterized by apoptosis. Colonization of attached cells was sparse on the untreated sponge and membrane on day 1, and the cells were round, small, and filled with intense and closely packed intracellular ROS. In contrast, NAC-pretreated material had dense cell colonies consisting of well-spread osteoblasts and fully developing cytoskeleton and cellular processes with little ROS generation. On day 7 of culture, NAC-pretreated collagen sponge and membrane yielded an expanded alkaline phosphatase-positive area occupying 60% and 80% of the surface area, respectively, whereas the untreated collagen materials had limited alkaline phosphatase activity (7% or less). Commercial collagen sponge and membrane induced considerable cell death, impaired initial function, and generated extraordinary intracellular ROS in attached osteoblasts, whereas NAC pretreatment substantially ameliorated these effects. The potential benefits of NAC's detoxifying capacity on bone regeneration using collagen matrix materials in an animal model should be confirmed with further study.
    The International journal of oral & maxillofacial implants 01/2010; 25(5):939-46. · 1.91 Impact Factor
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    ABSTRACT: To examine the bioactivity of differently aged titanium (Ti) disks and to determine whether ultraviolet (UV) light treatment reverses the possible adverse effects of Ti aging. Ti disks with three different surface topographies were prepared: machined, acid-etched, and sandblasted. The disks were divided into three groups: disks tested for biologic capacity immediately after processing (fresh surfaces), disks stored under dark ambient conditions for 4 weeks, and disks stored for 4 weeks and treated with UV light. The protein adsorption capacity of Ti was examined using albumin and fibronectin. Cell attraction to Ti was evaluated by examining migration, attachment, and spreading behaviors of human osteoblasts on Ti disks. Osteoblast differentiation was evaluated by examining alkaline phosphatase activity, the expression of bone-related genes, and mineralized nodule area in the culture. Four-week-old Ti disks showed = or < 50% protein adsorption after 6 hours of incubation compared with fresh disks, regardless of surface topography. Total protein adsorption for 4-week-old surfaces did not reach the level of fresh surfaces, even after 24 hours of incubation. Fifty percent fewer human osteoblasts migrated and attached to 4-week-old surfaces compared with fresh surfaces. Alkaline phosphatase activity, gene expression, and mineralized nodule area were substantially reduced on the 4-week-old surfaces. The reduction of these biologic parameters was associated with the conversion of Ti disks from superhydrophilicity to hydrophobicity during storage for 4 weeks. UV-treated 4-week-old disks showed even higher protein adsorption, osteoblast migration, attachment, differentiation, and mineralization than fresh surfaces, and were associated with regenerated superhydrophilicity. Time-related degradation of Ti bioactivity is substantial and impairs the recruitment and function of human osteoblasts as compared to freshly prepared Ti surfaces, suggesting a "biologic aging"-like change of Ti. UV treatment of aged Ti, however, restores and even enhances bioactivity, exceeding its innate levels.
    The International journal of oral & maxillofacial implants 01/2010; 25(1):49-62. · 1.91 Impact Factor
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    ABSTRACT: There is a great demand for dental implant surfaces to accelerate the process of peri-implant bone generation to reduce its healing time and enable early loading. To this end, an inverse correlation between the proliferation and functional maturation (differentiation) in osteoblasts presents a challenge for the rapid generation of greater amounts of bone. For instance, osteoblasts exhibit faster differentiation but slower proliferation on micro-roughened titanium surfaces. Using a unique micro-nano-hierarchical topography of TiO(2) that mimics biomineralized matrices, this study demonstrates that this challenge can be overcome without the use of biological agents. Titanium disks of grade 2 commercially pure titanium were prepared by machining (smooth surface). To create a microtexture with peaks and valleys (micropit surface), titanium disks were acid-etched. To create 200-nm TiO(2) nanonodules within the micropits (nanonodule-in-micropit surface), TiO(2) was sputter-deposited onto the acid-etched surface. Rat bone marrow-derived osteoblasts and NIH3T3 fibroblasts were cultured on machined smooth, micropit, and nanonodule-in-micropit surfaces. Despite the substantially increased surface roughness, the addition of 200-nm nanonodules to micropits increased osteoblast proliferation while enhancing their functional differentiation. In contrast, this nanonodule-in-micropit surface decreased proliferation and function in fibroblasts. The data suggest the establishment of cell-selectively functionalized nano-in-micro smart titanium surfaces that involve a regulatory effect on osteoblast proliferation, abrogating the inhibitory mechanism on the micropitted surface, while enhancing their functional differentiation. Biomimetic and controllable nature of this nanonodules-in-micropits surface may offer a novel micro-to-nanoscale hierarchical platform to biologically optimize nanofeatures of biomaterials. Particularly, this micro-nano-hybrid surface may be an effective approach to improve current dental implant surfaces for accelerated bone integration.
    Dental materials: official publication of the Academy of Dental Materials 12/2009; 26(4):275-87. · 2.88 Impact Factor
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    ABSTRACT: In this study, we tested the potential of UV-photofunctionalized titanium surfaces to overcome compromised bone-titanium integration in a gap healing model. Titanium in rod and disk forms was acid etched and then stored for 4 weeks under dark ambient conditions. Titanium rods with and without UV pretreatment were placed into a rat femur with (contact healing) or without (gap healing) contact with the innate cortical bone. The titanium implants were subjected to a biomechanical push-in test, micro-CT bone morphometry, and surface elemental analysis after 2 weeks of healing. The strength of bone-titanium integration in the gap healing model was one-third of that in the contact healing model. However, UV-treated implants in the gap healing condition produced a strength of bone-titanium integration equivalent to that of untreated implants in the contact healing condition. Bone volume around UV-treated implants was 2- to 3-fold greater than that around the untreated implants in the gap healing model. A bone generation profile drawn along the long axis of the implant exhibited greater contrast between the untreated and UV-treated surfaces in the cortical area than in the bone marrow area. The bone tissue formed on UV-treated implants showed a higher Ca/P ratio than that formed on untreated titanium. The rate of cell proliferation, alkaline phosphatase activity, and calcium deposition in femoral periosteal cells and in bone marrow-derived osteoblasts were greater in cultures on UV-treated titanium disks than in cultures on untreated disks. The UV-enhanced function in periosteal cells was more pronounced when they were co-cultured with bone marrow-derived osteoblasts, indicating a synergistic effect of UV-treated titanium with biological signals from bone marrow-derived osteoblasts. Within the limitation of the model used in this study, UV-photofunctionalized titanium surfaces may overcome the challenging condition of bone-titanium integration without cortical bone support. UV treatment of implants induced marked improvements in the behavior of bone formation and quantity and quality of bone tissue around the implants. These effects may be related to the promoted function of both periosteum- and bone marrow-derived osteogenic cells at the local level around UV-treated titanium surfaces.
    Biomaterials 12/2009; 31(7):1546-57. · 8.31 Impact Factor
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    ABSTRACT: The dentate gyrus (DG) of the hippocampal complex is one of the few areas of the rodent brain where neurogenesis continues throughout adulthood. We investigated the effects of the molarless condition on cell proliferation, rate of differentiation into neurons in the subgranular zone of the DG, and plasma corticosterone levels. The molarless condition decreased cell proliferation in the DG and increased plasma corticosterone levels. Approximately 80% of newly generated cells differentiated into neurons and the remaining 20% of the cells differentiated into astrocytes. These ratios were not significantly different between control and molarless rats. In conclusion, the rates of neurogenesis and gliogenesis in the DG are suppressed by the molarless condition, and this suppression might be associated with the increased corticosteroid levels in molarless subjects.
    Neuroscience Letters 11/2009; 469(1):44-8. · 2.03 Impact Factor
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    ABSTRACT: During implant healing, mechanical force is transmitted to osteogenic cells via implant surfaces with various topographies. This study tested a hypothesis that osteoblasts respond to mechanical stimulation differently on titanium with different surface topographies. Rat bone-marrow-derived osteoblastic cells were cultured on titanium disks with machined or acid-etched surfaces. A loading session consisted of a 3-minute application of a 10- or 20-mum-amplitude vibration. Alkaline phosphatase activity and gene expression increased only when the cells were loaded in 3 sessions/day on machined surfaces, regardless of the vibration amplitude, whereas they were increased with 1 loading session/day on the acid-etched surface. The loading did not affect the osteoblast proliferation on either surface, but selectively enhanced the cell spreading on the machined surface. Analysis of the data suggests that osteoblastic differentiation is promoted by mechanical stimulation on titanium, and that the promotion is disproportionate, depending on the titanium surface topography. The frequency of mechanical stimulation, rather than its amplitude, seemed to have a key role.
    Journal of dental research 09/2009; 88(9):812-6. · 3.46 Impact Factor
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    ABSTRACT: Control of hyperplastic and invasively growing gingival tissue is crucial for maintaining normal oral function and for successful bone regenerative therapy. We tested the hypothesis that materials containing N-acetyl cysteine (NAC), an antioxidant cysteine derivative, can control proliferation and function of oral mucosal cells. Oral mucosal cells derived from the rat palatal tissue were cultured with or without NAC at different concentrations (2.5-10.0mM). To simulate inflammatory conditions, cultures were treated with hydrogen peroxide. NAC was also applied via collagen materials in membrane and sponge forms to explore the clinical applicability. The redox balance inside the cells was evaluated by measuring the concentration of intracellular glutathione (GSH). Adding NAC into cultures of oral mucosal cells reduced their proliferation, transcriptional expression, and collagen production in an NAC-concentration-dependent manner without cytotoxic effects. Furthermore, NAC substantially reduced the hydrogen peroxide-induced elevation of cellular proliferation and collagen production. The controlling effects of NAC were also demonstrated in cells cultured on NAC-containing collagen materials and were associated with an increase in intracellular glutathione (GSH) reserves and a decrease in the oxidized form of glutathione (GSSG). These results indicate that NAC may abrogate inflammation- or oxidative-stress-induced hyperfunction of oral mucosal cells and that it can be delivered effectively via biodegradable materials. This study provides a basis to explore NAC-containing biomaterials that are functionalized to control oral soft tissue growth and function without cytotoxicity.
    Dental materials: official publication of the Academy of Dental Materials 09/2009; 25(12):1532-40. · 2.88 Impact Factor

Publication Stats

487 Citations
138.78 Total Impact Points

Institutions

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