↑ Return to Publications

Print this Page

Papers

  • Molecular level evaluation on HEMA interaction with a collagen model.

    Molecular level evaluation on HEMA interaction with a collagen model.

    Dent Mater. 2014 Dec 10;

    Authors: Hiraishi N, Tochio N, Kigawa T, Otsuki M, Tagami J

    Abstract
    OBJECTIVE: 2-Hydroxyethylmethacrylate (HEMA) diffuses in wet dentin and promotes adhesion during dentin priming and bonding. We have investigated the molecular level interaction between HEMA and a collagen model by using saturation transfer difference (STD) NMR.
    METHODS: The binding of HEMA to collagen was preliminarily investigated by suspending demineralized human dentin powders in a 4mM HEMA solution for 1h and measuring the decrease in the HEMA concentration on a spectrophotometer. The molecular level interaction of HEMA with atelocollagen, which was used as a collagen model, was investigated by STD-NMR spectroscopy.
    RESULTS: The HEMA concentration in the suspension did not change, indicating that HEMA did not bind to dentin collagen. This was confirmed by STD-NMR; when the atelocollagen resonance was saturated, no saturation was propagated to HEMA and no STD signals were detected.
    SIGNIFICANCE: The HEMA protons were not near the atelocollagen surface, indicating HEMA did not interact with atelocollagen. The collagen fibrils may be surrounded by water molecules in dentin/bond interfaces, which prevent the direct HEMA binding interaction.

    (25499247) – as supplied by publisher]

    Bibliography

  • Phytic Acid: An Alternative Root Canal Chelating Agent.
    .

    Phytic Acid: An Alternative Root Canal Chelating Agent.

    J Endod. 2014 Nov 20;

    Authors: Nassar M, Hiraishi N, Tamura Y, Otsuki M, Aoki K, Tagami J

    Abstract
    INTRODUCTION: The objectives of this study were to investigate the effect of phytic acid, inositol hexakisphosphate (IP6), as a final rinse on the surface of instrumented root canals and smear-layered flat dentin surfaces treated with sodium hypochlorite (NaOCl) and to evaluate its effect on the viability and alkaline phosphatase activity of osteoblast-like cells (MC3T3-E1).
    METHODS: The universally accepted chelating agent EDTA was used as the control in all conducted experiments. Root canals of human canines were instrumented with rotary files and irrigated with 5% NaOCl, followed by a final rinse of 17% EDTA (1 minute), 1% IP6 (1 minute or 30 seconds), or distilled water. NaOCl-treated flat coronal dentin surfaces were also treated with 17% EDTA (1 minute), 1% IP6 (1 minute or 30 seconds), or distilled water. The presence or absence of smear layer was evaluated with scanning electron microscopy. Cell viability and alkaline phosphatase assays were performed to evaluate the effect of IP6 and EDTA on cultured MC3T3-E1 cells.
    RESULTS: The results demonstrated the ability of IP6 to remove the smear layer from instrumented root canals and flat coronal dentin surfaces. When compared with EDTA, IP6 was less cytotoxic and did not affect the differentiation of MC3T3-E1 cells.
    CONCLUSIONS: IP6 shows the potential to be an effective and biocompatible chelating agent.

    (25453568) – as supplied by publisher]

    Bibliography

  • Phytic Acid: An Alternative Root Canal Chelating Agent.
    .

    Phytic Acid: An Alternative Root Canal Chelating Agent.

    J Endod. 2014 Nov 20;

    Authors: Nassar M, Hiraishi N, Tamura Y, Otsuki M, Aoki K, Tagami J

    Abstract
    INTRODUCTION: The objectives of this study were to investigate the effect of phytic acid, inositol hexakisphosphate (IP6), as a final rinse on the surface of instrumented root canals and smear-layered flat dentin surfaces treated with sodium hypochlorite (NaOCl) and to evaluate its effect on the viability and alkaline phosphatase activity of osteoblast-like cells (MC3T3-E1).
    METHODS: The universally accepted chelating agent EDTA was used as the control in all conducted experiments. Root canals of human canines were instrumented with rotary files and irrigated with 5% NaOCl, followed by a final rinse of 17% EDTA (1 minute), 1% IP6 (1 minute or 30 seconds), or distilled water. NaOCl-treated flat coronal dentin surfaces were also treated with 17% EDTA (1 minute), 1% IP6 (1 minute or 30 seconds), or distilled water. The presence or absence of smear layer was evaluated with scanning electron microscopy. Cell viability and alkaline phosphatase assays were performed to evaluate the effect of IP6 and EDTA on cultured MC3T3-E1 cells.
    RESULTS: The results demonstrated the ability of IP6 to remove the smear layer from instrumented root canals and flat coronal dentin surfaces. When compared with EDTA, IP6 was less cytotoxic and did not affect the differentiation of MC3T3-E1 cells.
    CONCLUSIONS: IP6 shows the potential to be an effective and biocompatible chelating agent.

    (25453568) – as supplied by publisher]

    Bibliography

  • Effect of different desensitizers on inhibition of bovine dentin demineralization: micro-computed tomography assessment.
      .

    Effect of different desensitizers on inhibition of bovine dentin demineralization: micro-computed tomography assessment.

    Eur J Oral Sci. 2014 Nov 1;

    Authors: Lodha E, Hamba H, Nakashima S, Sadr A, Nikaido T, Tagami J

    Abstract
    This study evaluated the effect of two desensitizers on inhibition of dentin demineralization, after immersion in artificial saliva using micro-computed tomography (μCT). Dentin blocks cut from bovine incisors were treated with deionized water (DW, a negative control) or one of three desensitizers: a fluoride varnish (Duraphat, a positive control), a calcium phosphate desensitizer (Teethmate Desensitizer), and a fluoro-alumino-calcium silicate-based desensitizer (Nanoseal). After each treatment, the specimens in Duraphat, Nanoseal, and Teethmate Desensitizer groups were pre-immersed in artificial saliva (pH 6.5) for either 1 d or 1 wk. The mineral loss of the specimens after demineralization (pH 5.0, 3 h) was evaluated by μCT. The treated surface was investigated with scanning electron microscopy. Mineral loss in all treatment groups was significantly lower than that in DW. Duraphat was the most effective treatment against demineralization, followed by Nanoseal. Nanoseal showed significantly better reduction in mineral loss following immersion for 1 wk in artificial saliva than for 1 d. However, Teethmate Desensitizer and Duraphat did not exhibit enhanced inhibition of demineralization over a longer period of immersion in artificial saliva. Scanning electron microscopy images showed deposition of particles on the dentin in both Teethmate Desensitizer. The application of Teethmate Desensitizer and Nanoseal to the exposed dentin surface resulted in inhibition of demineralization, with Nanoseal resulting in improved inhibition after prolonged immersion in artificial saliva.

    (25363830)

    Bibliography

  • Ultramorphological Assessment of Dentin-Resin Interface After Use of Simplified Adhesives.
    .

    Ultramorphological Assessment of Dentin-Resin Interface After Use of Simplified Adhesives.

    Oper Dent. 2014 Oct 9;

    Authors: Marghalani H, Bakhsh T, Sadr A, Tagami J

    Abstract
    SUMMARY This study assessed dentin/resin interface integration in Class I cavities restored with simplified adhesives by using a focused ion-beam milling (FIB) and transmission electron microscope (TEM). Class I cavities (1.5-mm depth with dentin thickness of ∼0.5 mm, 4-mm length, and 2-mm width) were prepared on freshly extracted, sound human molars. Two all-in-one adhesive systems (Scotchbond/Single Bond Universal [SUD] and Xeno-V(+) [X5D]) were used and compared with a two-step etch-and-rinse system (Prime&Bond NT [NTD]). The adhesives were applied according to the manufacturers’ guidelines. A universal resin composite (Filtek Z350 XT Universal) was used to restore the cavities in one bulk filling and was irradiated at 550 mW/cm(2) for 40 seconds by a quartz-tungsten-halogen light (Optilux 501). After exposure to liquid nitrogen coolant, the specimens were milled to nanoscale thickness by FIB to view and then assess the area of dentin-resin interface by TEM. Unlike the unfilled X5D, a noticeably smooth transition zone at the dentin-resin interface was shown for the SUD and NTD adhesives. The SUD demonstrated an uneven hybrid layer with clearly demineralized collagen bundles. Ultramorphologically, dispersed needlelike apatite crystals were detected within the partially demineralized dentin or the hybrid layer of both compositionally different all-in-one simplified adhesives. Conversely, these crystals were entirely absent from the hybrid layer of the etch-and-rinse NTD adhesive. In the X5D group, a bright band was noted beneath the hybrid layer. The methacryloxydecyl dihydrogen phosphate monomer containing ultramild self-etch adhesive (SUD) was still validated in terms of its capability in dentin adhesion.

    (25299704)- as supplied by publisher]

    Bibliography

  • The effect of tooth age on color adjustment potential of resin composite restorations.
    .

    The effect of tooth age on color adjustment potential of resin composite restorations.

    J Dent. 2014 Sep 18;

    Authors: Tanaka A, Nakajima M, Seki N, Foxton R, Tagami J

    Abstract
    OBJECTIVES: The purpose of this study was to investigate the effect of tooth age on color adjustment potential of resin composite restorations in human teeth.
    METHODS: Twenty extracted human premolars with an A2 shade, extracted for orthodontic reasons from younger patients (20-28 yrs) (younger teeth) and periodontal reasons from older patients (45-69 yrs) (older teeth), were used in this study. Cylindrical shaped cavities (3.0mm depth; 2.0mm diameter) were prepared in the center of the crowns on the buccal surface. One of four resin composites of A2 shade (Kalore, KA; Solare, SO; Clearfil Majesty, MJ; Beautifil II, BF) was placed in the cavity, and the color was measured at four areas (0.4mm x 0.4 mm(2)) on the restored teeth (area 1; tooth area 1.0mm away from the border of resin composite restoration: area 2; tooth border area 0.3mm away from margin of resin composite restoration: area 3; resin composite border area 0.3mm away from margin of resin composite restoration: area 4; resin composite area at the center of resin composite restoration) using a spectrophotometer (Crystaleye). The color of each area was determined according to the CIELAB color scale. Color differences (ΔE*) between the areas of 1 and 2, 2 and 3, 3 and 4 and 1 and 4 were calculated, and also the ratio of ΔE*area2-3 to ΔE*area1-4 (ΔE*area2-3/1-4), ΔE*area3-4 to ΔE*area1-4 (ΔE*area3-4/1-4) and ΔE*area1-2 to ΔE*area1-4 (ΔE*area1-2/1-4) as a parameter of the color shift in resin composite restoration, were determined. Moreover, the light transmission characteristics of the resin materials and dentine discs from the younger and older teeth were measured using a goniophotometer. The data were statistically analyzed using two-way ANOVA, and Dunnett’s T3 and t-test for the post-hoc test.
    RESULTS: ΔE*area2-3 (color difference between resin composite and tooth at the border) and ΔE*area1-4 (color difference between resin composite and tooth) of the older teeth groups were significantly larger than those of younger teeth groups (p<0.05). The ΔE*area2-3/1-4 (mis-match rate in color shifting at the border) of the older teeth groups was larger than that of the younger teeth groups (p<0.05). ΔE*area3-4/1-4 (color shifting rate of resin composite side) was significantly larger in older teeth than younger teeth (p<0.05), while ΔE*area1-2/1-4 (color shifting rate of tooth side), was significantly smaller in older teeth than younger teeth (p<0.05). In each tooth group, there were no significant differences in ΔE*area2-3, ΔE*area1-4, ΔE*area2-3/1-4, ΔE*area3-4/1-4 and ΔE*area1-2/1-4 between the materials (p>0.05). Analysis of the light transmission properties indicated that older dentine transmitted more light, while younger dentine exhibited greater light diffusion and transmitted less light.
    CONCLUSIONS: The color shifting effects at the border of the resin composite restorations were influenced by the age of the tooth. This behavior might be influenced by the light transmission characteristics of dentine in restored teeth. Clinical Significance: The potential for color adjustment of resin composite restorations may be less in older teeth than younger teeth.

    (25242100)- as supplied by publisher]

    Bibliography

  • Effect of hesperidin incorporation into a self-etching primer on durability of dentin bond.
    .

    Effect of hesperidin incorporation into a self-etching primer on durability of dentin bond.

    Dent Mater. 2014 Sep 3;

    Authors: Islam MS, Hiraishi N, Nassar M, Yiu C, Otsuki M, Tagami J

    Abstract
    OBJECTIVE: Collagen degradation at the resin-dentin interface deteriorates dentin bond durability. The use of natural cross-linkers might offer a positive approach to stabilize the resin-dentin interface. This study evaluated the effects of incorporation of natural cross-linkers into a self-etch adhesive primer on the immediate and long-term micro-tensile bond strengths (μTBS) to dentin.
    METHODS: Experimental primers were prepared by incorporating either 0.5%, 1%, 2%, 5% of hesperidin (HPN) or 0.5% of proanthocyanidins (PA) into Clearfil SE primer. Extracted human molar teeth were restored using the experimental primers or the pure SE primer (control). The mechanical properties of the bonded interfaces were measured using the nano-indentation tests. Beam-shaped bonded specimens were sub-divided for one-day and one-year μTBS test. Interfacial collagen morphology was observed using transmission electron microscopy.
    RESULT: The immediate μTBS significantly increased in 0.5%, 1% and 2% HPN-incorporated groups when compared with the control. The mechanical properties of bonded interface were improved with 1% and 2% HPN-incorporated primers. For the long-term μTBS, the 2% and 5% HPN-incorporated group were significantly higher than the control. The morphology of the collagen fibrils were preserved by 5% HPN-incorporation after one-year storage. The PA group, however, failed to improve the μTBS and the mechanical properties of the bonded interfaces.
    SIGNIFICANCE: The incorporation of 2% HPN into the self-etching primer had a positive effect on the immediate μTBS and mechanical properties of the resin-dentin interfaces. The 5% HPN group preserved the morphology of the collagen in the hybrid layer after one-year storage in artificial saliva.

    (25194169)- as supplied by publisher]

    Bibliography

  • Effects of light curing method and resin composite composition on composite adaptation to the cavity wall.
    .

    Effects of light curing method and resin composite composition on composite adaptation to the cavity wall.

    Dent Mater J. 2014 Jul 2;

    Authors: Yoshikawa T, Morigami M, Sadr A, Tagami J

    Abstract
    This study aimed to evaluate the effects of the light curing method and resin composite composition on marginal sealing and resin composite adaptation to the cavity wall. Cylindrical cavities were prepared on the buccal or lingual cervical regions. The teeth were restored using Clearfil Liner Bond 2V adhesive system and filled with Clearfil Photo Bright or Palfique Estelite resin composite. The resins were cured using the conventional or slow-start light curing method. After thermal cycling, the specimens were subjected to a dye penetration test. The slow-start curing method showed better resin composite adaptation to the cavity wall for both composites. Furthermore, the slow-start curing method resulted in significantly improved dentin marginal sealing compared with the conventional method for Clearfil Photo Bright. The light-cured resin composite, which exhibited increased contrast ratios duringpolymerization, seems to suggest high compensation for polymerization contraction stress when using the slow-start curing method.

    (24988883)- as supplied by publisher]

    Bibliography

  • Sealing performance of resin cements before and after thermal cycling: evaluation by optical coherence tomography.
    .

    Sealing performance of resin cements before and after thermal cycling: evaluation by optical coherence tomography.

    Dent Mater. 2014 Sep;30(9):993-1004

    Authors: Turkistani A, Sadr A, Shimada Y, Nikaido T, Sumi Y, Tagami J

    Abstract

    OBJECTIVES: Self-adhesive resin cements have been recently introduced; however, there is little data available on their long-term performance. In this in vitro study, swept-source optical coherence tomography (OCT) at 1310 nm center wavelength was used for monitoring adaptation of indirect resin restorations after thermal cycling.

    METHODS: Resin inlays were luted to class-I cavities of extracted human teeth using three resin cements; Clearfil SA Luting (SA; Kuraray), Bistite II DC or Multibond II (Tokuyama Dental). Each cement was applied with or without pre-coating of dentin by a self-etch adhesive (Clearfil SE Bond) and a low-viscosity microfilled resin. OCT imaging was performed after 24 h, after 2000 and after 10,000 thermocycles (n=5). Selected samples were sectioned for interfacial observation by confocal laser scanning microscope (CLSM). Floor adaptation (percentage) was analyzed by software on 20 B-scans throughout each specimen, and subjected to statistical analysis by three-way ANOVA test at a significance level of 0.05.

    RESULTS: Resin cement type, resin coating and thermal aging all significantly affected adaptation (p<0.05). Initially, SA showed the highest adaptation; however, thermal aging significantly affected its sealing. The best results for all the cements were consistently achieved when the resin coating technique was applied where no deterioration of interfacial integrity was observed in the coated groups. CLSM closely confirmed OCT findings in all groups.

    SIGNIFICANCE: OCT could be used for monitoring of composite inlays with several interfacial resin layers. The application of a direct bonding agent in the resin-coating technique improved interfacial sealing and durability of all resin cements.

    (24946983) – in process]

    Bibliography

  • Evaluation of the marginal fit at implant-abutment interface by optical coherence tomography.
    .

    Evaluation of the marginal fit at implant-abutment interface by optical coherence tomography.

    J Biomed Opt. 2014 May 1;19(5):55002

    Authors: Kikuchi K, Akiba N, Sadr A, Sumi Y, Tagami J, Minakuchi S

    Abstract
    ABSTRACT. Vertical misfit of implant-abutment interface can affect the success of implant treatment; however, currently available modalities have limitations to detect these gaps. This study aimed to evaluate implant-abutment gaps in vitro using optical coherence tomography (OCT). Vertical misfit gaps sized 50, 100, 150, or 200 μm were created between external hexagonal implants and titanium abutments (Nobel Biocare, Göteborg, Sweden). A porcine gingival tissue slice, 0.5, 1.0, 1.5, or 2.0 mm in thickness, was placed on each implant-abutment interface. The gaps were evaluated by swept-source OCT at a center wavelength of 1330 nm (Panasonic Healthcare, Ehime, Japan) with beam angles of 90, 75 and 60 deg to the implant long-axis. The results suggested that while the measurements were precise, gap size and gingival thickness affected the sensitivity of detection. Gaps sized 100 μm and above could be detected with good accuracy under 0.5- or 1.0-mm-thick gingiva (GN). Around 70% of gaps sized 150 μm and above could be detected under 1.5-mm-thick GN. On the other hand, 80% of gaps under 2.0-mm-thick GN were not detected due to attenuation of near-infrared light through the soft tissue. OCT appeared as an effective tool for evaluating the misfit of implant-abutment under thin layers of soft tissue.

    (24805806)- in process]

    Bibliography

  • Endodontic instruments after torsional failure: Nanoindentation test.
    .

    Endodontic instruments after torsional failure: Nanoindentation test.

    Scanning. 2014 Mar 9;

    Authors: Jamleh A, Sadr A, Nomura N, Ebihara A, Yahata Y, Hanawa T, Tagami J, Suda H

    Abstract
    This study aimed to evaluate effects of torsional loading on the mechanical properties of endodontic instruments using the nanoindentation technique. ProFile (PF; size 30, taper 04; Dentsply Maillefer, Switzerland) and stainless steel (SS; size 30, taper 02; Mani, Japan) instruments were subjected to torsional test. Nanoindentation was then performed adjacent to the edge of fracture (edge) and at the cutting part beside the shank (shank). Hardness and elastic modulus were measured under 100-mN force on 100 locations at each region, and compared to those obtained from the same regions on new instruments. It showed that PF and SS instruments failed at 559 ± 67 and 596 ± 73 rotation degrees and mean maximum torque of 0.90 ± 0.07 and 0.99 ± 0.05 N-cm, respectively. Hardness and elastic modulus ranged 4.8-6.7 and 118-339 GPa in SS, and 2.7-3.2 and 52-81 GPa in PF. Significant differences between torsion-fractured and new instruments in hardness and elastic modulus were detected in the SS system used. While in PF system, the edge region after torsional fracture had significantly lower hardness and elastic modulus compared to new instruments. The local hardness and modulus of elasticity of endodontic instruments adjacent to the fracture edge are significantly reduced by torsional loading. SCANNING 9999:1-7, 2014. © 2014 Wiley Periodicals, Inc.

    (24610598)- as supplied by publisher]

    Bibliography

  • Characterization of transparent dentin in attrited teeth using optical coherence tomography.
    Related Articles on PubMed

    Characterization of transparent dentin in attrited teeth using optical coherence tomography.

    Lasers Med Sci. 2014 Feb 16;

    Authors: Mandurah MM, Sadr A, Bakhsh TA, Shimada Y, Sumi Y, Tagami J

    Abstract
    Attrition and wear of tooth surface occur with aging and result in loss of enamel, with exposure and histological changes in dentin. Dealing with attrited teeth and restoration of the lost tissue are clinically challenging. The main objective of this study is to characterize the exposed transparent dentin in the occlusal surface of attrited teeth by optical coherence tomography (OCT). Naturally attrited, extracted human teeth with occlusal-transparent dentin were investigated in comparison to sound and carious teeth. The teeth were subjected to OCT imaging and then cross-sectioned and polished. OCT B-scans were compared to light microscopy images of the same cross section. In OCT images, some changes were evident at the transparent dentin in attrited teeth. An OCT attenuation coefficient parameter (μ t) was derived based on the Beer-Lambert law as a function of backscatter signal slope. The mean values of μ t were 1.05 ± 0.3, 2.23 ± 0.4, and 0.61 ± 0.27 mm(-1) for sound, carious, and transparent dentins, respectively. One-way ANOVA with Tukey’s post-hoc showed a significant difference between groups (p < 0.05). Physiological changes in transparent dentin that involve deposition of mineral casts in the dentinal tubules lead to lower attenuation of OCT signal. OCT has a potential role to detect transparent dentin on the surface of attrited teeth and can be used in the future as a clinical adjunct tool.

    (24532117) – as supplied by publisher]

    Bibliography

  • Detection of occlusal caries in primary teeth using swept source optical coherence tomography.
    Related Articles on PubMed

    Detection of occlusal caries in primary teeth using swept source optical coherence tomography.

    J Biomed Opt. 2014 Jan 1;19(1):16020

    Authors: Nakajima Y, Shimada Y, Sadr A, Wada I, Miyashin M, Takagi Y, Tagami J, Sumi Y

    Abstract
    ABSTRACT. This study aimed to investigate swept source optical coherence tomography (SS-OCT) as a detecting tool for occlusal caries in primary teeth. At the in vitro part of the study, 38 investigation sites of occlusal fissures (noncavitated and cavitated) were selected from 26 extracted primary teeth and inspected visually using conventional dental equipment by six examiners without any magnification. SS-OCT cross-sectional images at 1330-nm center wavelength were acquired on the same locations. The teeth were then sectioned at the investigation site and directly viewed under a confocal laser scanning microscope (CLSM) by two experienced examiners. The presence and extent of caries were scored in each observation. The results obtained from SS-OCT and conventional visual inspections were compared with those of CLSM. Consequently, SS-OCT could successfully detect both cavitated and noncavitated lesions. The magnitude of sensitivity for SS-OCT was higher than those for visual inspection (sensitivity of visual inspection and SS-OCT, 0.70 versus 0.93 for enamel demineralization, 0.49 versus 0.89 for enamel cavitated caries, and 0.36 versus 0.75 for dentin caries). Additionally, occlusal caries of a few clinical cases were observed using SS-OCT in vivo. The results indicate that SS-OCT has a great detecting potential for occlusal caries in primary teeth.

    (24474506) – in process]

    Bibliography

  • Evaluation of new treatment for incipient enamel demineralization using 45S5 bioglass.
    Related Articles on PubMed

    Evaluation of new treatment for incipient enamel demineralization using 45S5 bioglass.

    Dent Mater. 2014 Jan 13;

    Authors: Bakry AS, Takahashi H, Otsuki M, Tagami J

    Abstract
    Bioglass 45S5 is a silica-based bioactive glass capable of depositing a layer of hydroxyl carbonate apatite on the surface of the glass when immersed in body fluids. The present paper studies a new technique for treating early human dental enamel caries lesions by using a paste composed of 45S5 bioglass and phosphoric acid. Artificial caries lesions were induced in enamel flat surfaces by means of a decalcification solution. All specimens were exposed to a brushing-abrasion challenge to test the durability of any newly formed layer resulting from the application of 45S5 bioglass paste. The specimens treated with bioglass paste showed complete coverage with a layer of brushite crystals. The brushing-abrasion challenge did not statistically affect the percentage of enamel coverage with the crystalline layer formed by the application of bioglass (p<0.05). These crystals were converted to hydroxyapatite crystals when stored in artificial saliva for 14 days. The current technique suggests the possibility of restoring incipient enamel erosive lesion with an abrasion durable layer of hydroxyapatite crystals.

    (24433821) – as supplied by publisher]

    Bibliography

  • Nanoindentation hardness of intertubular dentin in sound, demineralized and natural caries-affected dentin.
    Related Articles on PubMed

    Nanoindentation hardness of intertubular dentin in sound, demineralized and natural caries-affected dentin.

    J Mech Behav Biomed Mater. 2013 Dec 24;32C:39-45

    Authors: Joves GJ, Inoue G, Sadr A, Nikaido T, Tagami J

    Abstract
    The purpose of this study was to investigate the mechanical properties of intertubular dentin in sound, natural caries-affected (NCAD) and artificial caries-affected dentin (ACAD) using nanoindentation.
    MATERIALS AND METHODS: Non-caries molars and caries molars with International Caries Detection and Assessment System (ICDAS II) score 5 at the occlusal site were used and caries was excavated using a spoon excavator, a round bur at low speed without water and a dye solution as guidance to detect the infected tissue. Specimens with remaining dentin thickness (RDT) >2mm were selected. ACAD teeth were created from sound teeth over 7 days in a demineralizing solution. Specimens were embedded into plastic rings with acrylic resin and then sagittal mesial-distal sectioned from crown to the long axis of the root under cooling water using a low-speed diamond blade. The surface of interest was fine polished sequentially. Hardness measurement was performed within an axial depth of 1000μm with at least of 320 indentations on each sample. Mann-Whitney U Test was used to compare the hardness as the variable among different dentin types (SOUND, NCAD and ACAD) at each dentin depth level.
    RESULTS: There was no significant difference in nanohardness between NCAD and ACAD up to a depth of 130μm (p>0.05). NCAD consistently showed lower hardness. ACAD showed no significant difference in hardness with SOUND dentin beyond 190μm (p<0.05). The lesion front in ACAD was considered to be located around the depth of 180μm.
    CONCLUSION: Natural and artificial caries-affected dentin tissues were superficially comparable in intertubular nanohardness. There is a certain layer within the natural caries-affected dentin with higher hardness; however the long-term effects of caries beneath the lesion extend deeply through intertubular dentin. Sound dentin at deep areas (close to the pulp chamber) is considered to be soft.

    (24394774) – as supplied by publisher]

    Bibliography

  • Dental Pulp Dendritic Cells Migrate to Regional Lymph Nodes.
    Related Articles on PubMed

    Dental Pulp Dendritic Cells Migrate to Regional Lymph Nodes.

    J Dent Res. 2013 Dec 30;

    Authors: Bhingare AC, Ohno T, Tomura M, Zhang C, Aramaki O, Otsuki M, Tagami J, Azuma M

    Abstract
    Dendritic cell (DC) migration to regional lymph nodes (RLNs) is an essential step in adaptive immunity, and cell-surface antigens on migrating DCs greatly affect the quality and quantity of subsequent immune responses. Although MHC class II(+) DC-like cells exist in the dental pulp, the lineage and function of these cells remain unknown. Here, we identified migratory DCs from the dental pulp after cusp trimming and acid etching in KikGR mice, in which the photoconvertible fluorescent protein changed from green to red upon violet light exposure. Two major cell fractions from the dental pulp had migrated to the RLNs at 16 hrs after cusp treatment, which showed the following lineage markers in the main and second fractions: CD11c(high)CD11b(++)Ly6C(low) Ly6G(low) F4/80(+) and CD11c(med)CD11b(+++)Ly6C(++)Ly6G(+++)F4/80(-), respectively. These lineage markers indicate that the former cells were DCs that had migrated through afferent lymphoid vessels, and the latter were granulocytes recruited via blood circulation. Migratory dental pulp DCs were mature, expressing the highest levels of CD273 (B7-DC) and CD86 co-stimulators and MHC class II. Our results suggest that cariogenic-bacteria-exposed dental pulp DCs migrate to RLNs and there trigger adaptive immune responses.

    (24378366) – as supplied by publisher]

    Bibliography

  • Effect of smear layer deproteinizing on resin-dentine interface with self-etch adhesive.
    Related Articles on PubMed

    Effect of smear layer deproteinizing on resin-dentine interface with self-etch adhesive.

    J Dent. 2013 Dec 7;

    Authors: Thanatvarakorn O, Nakajima M, Prasansuttiporn T, Ichinose S, Foxton RM, Tagami J

    Abstract
    OBJECTIVES: This study aimed to investigate deproteinizing effect of sodium-hypochlorite (NaOCl) and mild acidic hypochlorous-acid (HOCl) pretreatment on smear layer-covered dentine and to evaluate their effects on morphological characteristics of resin-dentine interface with self-etch adhesive.
    METHODS: Human coronal-dentine discs with standardized smear layer were pretreated with 6% NaOCl or 50ppm HOCl for 15s or 30s. Their deproteinizing effects at the treated smear layer-covered dentine surfaces were determined by the measurement of amide:phosphate ratio using ATR-FTIR analysis. In addition, using TEM, micromorphological alterations of hybridized complex and nanoleakage expression were evaluated at the interface of a self-etch adhesive (Clearfil SE Bond) to the pretreated dentine surface with or without subsequent application of a reducing agent (p-toluenesulfinic acid salt; Accel(®)).
    RESULTS: Both pretreatments of NaOCl and HOCl significantly reduced the amide:phosphate ratio as compared with the no-pretreated group (p<0.05), coincident with the elimination of the hybridized smear layer on their bonded interfaces. Nanoleakage within the hybrid layer was found in the no-pretreated and NaOCl-pretreated groups, whereas the subsequent reducing agent application changed the reticular nanoleakage to spotted type. HOCl-pretreated groups showed less nanoleakage expression in a spotted pattern, regardless of reducing agent application.
    CONCLUSIONS: NaOCl and HOCl solutions could remove the organic component on the smear layer-covered dentine, which could eliminate the hybridized smear layer created by self-etch adhesive, leading to the reduction of nanoleakage expression within hybrid layer.
    CLINICAL SIGNIFICANCE: Smear layer deproteinizing could modify dentine surface, giving an appropriate substrate for bonding to self-etch adhesive system.

    (24321293) – as supplied by publisher]

    Bibliography

  • The inhibition effect of non-protein thiols on dentinal matrix metalloproteinase activity and HEMA cytotoxicity.
    Related Articles on PubMed

    The inhibition effect of non-protein thiols on dentinal matrix metalloproteinase activity and HEMA cytotoxicity.

    J Dent. 2013 Dec 4;

    Authors: Nassar M, Hiraishi N, Shimokawa H, Tamura Y, Otsuki M, Kasugai S, Ohya K, Tagami J

    Abstract
    OBJECTIVES: Phosphoric acid (PA) etching used in etch-and-rinse adhesives is known to activate host-derived dentinal matrix-metalloproteinases (MMPs) and increase dentinal permeability. These two phenomena will result, respectively; in degradation of dentin-adhesive bond and leaching of some monomers especially 2-hydroxyethyl methacrylate (HEMA) into the pulp that would negatively affect the viability of pulpal cells. This study is the first to investigate the inhibitory effect of non-protein thiols (NPSH); namely reduced glutathione (GSH) and N-acetylcysteine (NAC) on dentinal MMPs and compare their effects on HEMA cytotoxicity.
    METHODS: Dentin powder was prepared from human teeth, demineralized with 1% PA and then treated with 2% GSH, 2% NAC or 2% chlorhexidine (CHX). Zymographic analysis of extracted proteins was performed. To evaluate the effect of GSH, NAC and CHX on HEMA cytotoxicity, solutions of these compounds were prepared with or without HEMA and rat pulpal cells were treated with the tested solutions for (6 and 24h). Cells viability was measured by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cytotoxicity data were analyzed by one-way ANOVA and Tukey post-hoc tests (P<0.05). Results: The inhibitory effect of GSH and NAC on dentinal MMPs was confirmed. GSH showed similar effectiveness to NAC regarding HEMA cytotoxicity inhibition.
    CONCLUSION: NPSH were effective to inhibit dentinal MMPs and HEMA cytotoxicity.
    CLINICAL SIGNIFICANCE: The tested properties of NPSH provide promising clinical use of these agents which would enhance dentin-bond durability and decrease post-operative sensitivity.

    (24316344) – as supplied by publisher]

    Bibliography

  • Acceleration of curing of resin composite at the bottom surface using slow-start curing methods.

    Acceleration of curing of resin composite at the bottom surface using slow-start curing methods.

    Dent Mater J. 2013 Nov 15;

    Authors: Yoshikawa T, Morigami M, Sadr A, Tagami J

    Abstract
    The aim of this study was to evaluate the effect of two slow-start curing methods on acceleration of the curing of resin composite specimens at the bottom surface. The light-cured resin composite was polymerized using one of three curing techniques: (1) 600 mW/cm(2) for 60 s, (2) 270 mW/cm(2) for 10 s+0-s interval+600 mW/cm(2) for 50 s, and (3) 270 mW/cm(2) for 10 s+5-s interval+600 mW/cm(2) for 50 s. After light curing, Knoop hardness number was measured at the top and bottom surfaces of the resin specimens. The slow-start curing method with the 5-s interval caused greater acceleration of curing of the resin composite at the bottom surface of the specimens than the slow-start curing method with the 0-s interval. The light-cured resin composite, which had increased contrast ratios during polymerization, showed acceleration of curing at the bottom surface.

    (24240907) – as supplied by publisher]

    Bibliography

  • Polymerization behavior within adhesive layer of one- and two-step self-etch adhesives: A micro-Raman spectroscopic study.

    Polymerization behavior within adhesive layer of one- and two-step self-etch adhesives: A micro-Raman spectroscopic study.

    Dent Mater J. 2013 Nov 15;

    Authors: Sakano W, Nakajima M, Prasansuttiporn T, M Foxton R, Tagami J

    Abstract
    This study investigated the polymerization behavior within the adhesive layer of one- and two-step self-etch adhesives at the dentincomposite interface. Dentin surfaces were applied with Clearfil S(3) Bond (TS), Clearfil S(3) Bond Plus (TSP) and Clearfil SE Bond (SE), and then placed with a light-curing resin composite. After water storage for 24 h, the bonded teeth were sectioned and polished perpendicular to the adhesive interface, and the degree of conversion (DC) of the adhesive layer between the dentin and composite were determined using micro-Raman analysis. For all the adhesives, the DCs of the adhesive layers significantly decreased near the adhesive-composite join (p<0.05). For the maximum DC value (Pmax) and the DC value at the adhesive-composite join (Pitf), TS was significantly lower than TSP and SE (p<0.05). The polymerization of oxygen-inhibited layer at the top of the adhesive could not reach maximum DC even after polymerization of the overlying resin composite.

    (24240894) – as supplied by publisher]

    Bibliography