↑ Return to Publications

Print this Page

Papers

  • Inhibition of hydroxyapatite growth by casein, a potential salivary phosphoprotein homologue.

    Inhibition of hydroxyapatite growth by casein, a potential salivary phosphoprotein homologue.

    Eur J Oral Sci. 2015 Jun 17;

    Authors: Romero MJ, Nakashima S, Nikaido T, Ichinose S, Sadr A, Tagami J

    Abstract
    Salivary phosphoproteins are essential in tooth mineral regulation but are often overlooked in vitro. This study aimed to evaluate the effect of casein, as a salivary phosphoprotein homologue, on the deposition and growth of hydroxyapatite (HA) on tooth surfaces. Hydroxyapatite growth was quantified using seeded crystal systems. Artificial saliva (AS) containing HA powder and 0, 10, 20, 50, or 100 μg ml(-1) of casein, or 100 μg ml(-1) of dephosphorylated casein (Dcasein), was incubated for 0-8 h at 37°C, pH 7.2. Calcium concentrations were measured using atomic absorption spectroscopy (AAS). Surface precipitation of HA on bovine enamel and dentine blocks, incubated in similar conditions for 7 d, was examined using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) with selected area electron diffraction (SAED). Casein adsorption was assessed using modified Lowry assays and zeta-potential measurements. The AAS results revealed a concentration-dependent inhibition of calcium consumption. Hydroxyapatite precipitation occurred when no casein was present, whereas precipitation of HA was apparently completely inhibited in casein-containing groups. Adsorption data demonstrated increasingly negative zeta-potential with increased casein concentration and an affinity constant similar to proline-rich proteins with Langmuir modelling. Casein inhibited the deposition and growth of HA primarily through the binding of esterized phosphate to HA active sites, indicating its potential as a mineral-regulating salivary phosphoprotein homologue in vitro.

    (26083784) – as supplied by publisher]

    Bibliography

  • Inhibition of hydroxyapatite growth by casein, a potential salivary phosphoprotein homologue.

    Inhibition of hydroxyapatite growth by casein, a potential salivary phosphoprotein homologue.

    Eur J Oral Sci. 2015 Jun 17;

    Authors: Romero MJ, Nakashima S, Nikaido T, Ichinose S, Sadr A, Tagami J

    Abstract
    Salivary phosphoproteins are essential in tooth mineral regulation but are often overlooked in vitro. This study aimed to evaluate the effect of casein, as a salivary phosphoprotein homologue, on the deposition and growth of hydroxyapatite (HA) on tooth surfaces. Hydroxyapatite growth was quantified using seeded crystal systems. Artificial saliva (AS) containing HA powder and 0, 10, 20, 50, or 100 μg ml(-1) of casein, or 100 μg ml(-1) of dephosphorylated casein (Dcasein), was incubated for 0-8 h at 37°C, pH 7.2. Calcium concentrations were measured using atomic absorption spectroscopy (AAS). Surface precipitation of HA on bovine enamel and dentine blocks, incubated in similar conditions for 7 d, was examined using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) with selected area electron diffraction (SAED). Casein adsorption was assessed using modified Lowry assays and zeta-potential measurements. The AAS results revealed a concentration-dependent inhibition of calcium consumption. Hydroxyapatite precipitation occurred when no casein was present, whereas precipitation of HA was apparently completely inhibited in casein-containing groups. Adsorption data demonstrated increasingly negative zeta-potential with increased casein concentration and an affinity constant similar to proline-rich proteins with Langmuir modelling. Casein inhibited the deposition and growth of HA primarily through the binding of esterized phosphate to HA active sites, indicating its potential as a mineral-regulating salivary phosphoprotein homologue in vitro.

    (26083784) – as supplied by publisher]

    Bibliography

  • Microgaps and Demineralization Progress around Composite Restorations.

    Microgaps and Demineralization Progress around Composite Restorations.

    J Dent Res. 2015 Jun 16;

    Authors: Turkistani A, Nakashima S, Shimada Y, Tagami J, Sadr A

    Abstract
    This study investigated the influence of adhesives and marginal sealing on demineralization progress using optical coherence tomography (OCT). Cavities (4 × 2 mm) were prepared in bovine incisors and restored using Clearfil SE Protect (SP), Bond Force (BF), Scotchbond Universal (SB), or G-Bond Plus (GB), followed by Estelite Flow Quick flowable composite. The control group received no adhesive (n = 10). After 3-d incubation in artificial saliva and 10,000 thermal cycles, gaps at enamel and dentin margins were measured at 8 locations on cross-sectional images obtained from each restoration using swept-source OCT at 1310-nm wavelength. Specimens were demineralized using acidified gel (pH = 4.5) for 5 wk and scanned every week to monitor the lesion progress at the same marginal locations. Repeated-measures analysis of variance showed that demineralization period and adhesive type and their interaction had a significant effect on the lesion size in both substrates (P < 0.001). SP, BF, and SB had significantly lower enamel and dentin initial gaps than the control and GB (P < 0.05). Enamel lesion progress was slower in the fluoride-releasing adhesives SP and BF and significantly different from SB, GB, and the control (P < 0.001). SP and BF dentin lesions were significantly different from GB and the control (P < 0.001), but not from SB (P > 0.05). A significant positive correlation (P < 0.05) was found between initial gap length and formed lesion size in both substrates, which was stronger in enamel (r = 0.63) than dentin (r = 0.35). Microgaps forming at the margins of restorations depend on adhesives and significantly contribute to the progress of demineralization around the margins, while fluoride release may decrease the rate of progression.

    (26082389) – as supplied by publisher]

    Bibliography

  • Microgaps and Demineralization Progress around Composite Restorations.

    Microgaps and Demineralization Progress around Composite Restorations.

    J Dent Res. 2015 Jun 16;

    Authors: Turkistani A, Nakashima S, Shimada Y, Tagami J, Sadr A

    Abstract
    This study investigated the influence of adhesives and marginal sealing on demineralization progress using optical coherence tomography (OCT). Cavities (4 × 2 mm) were prepared in bovine incisors and restored using Clearfil SE Protect (SP), Bond Force (BF), Scotchbond Universal (SB), or G-Bond Plus (GB), followed by Estelite Flow Quick flowable composite. The control group received no adhesive (n = 10). After 3-d incubation in artificial saliva and 10,000 thermal cycles, gaps at enamel and dentin margins were measured at 8 locations on cross-sectional images obtained from each restoration using swept-source OCT at 1310-nm wavelength. Specimens were demineralized using acidified gel (pH = 4.5) for 5 wk and scanned every week to monitor the lesion progress at the same marginal locations. Repeated-measures analysis of variance showed that demineralization period and adhesive type and their interaction had a significant effect on the lesion size in both substrates (P < 0.001). SP, BF, and SB had significantly lower enamel and dentin initial gaps than the control and GB (P < 0.05). Enamel lesion progress was slower in the fluoride-releasing adhesives SP and BF and significantly different from SB, GB, and the control (P < 0.001). SP and BF dentin lesions were significantly different from GB and the control (P < 0.001), but not from SB (P > 0.05). A significant positive correlation (P < 0.05) was found between initial gap length and formed lesion size in both substrates, which was stronger in enamel (r = 0.63) than dentin (r = 0.35). Microgaps forming at the margins of restorations depend on adhesives and significantly contribute to the progress of demineralization around the margins, while fluoride release may decrease the rate of progression.

    (26082389) – as supplied by publisher]

    Bibliography

  • Study on the influence of leucine-rich amelogenin peptide (LRAP) on the remineralization of enamel defects via micro-focus x-ray computed tomography and nanoindentation.
    .

    Study on the influence of leucine-rich amelogenin peptide (LRAP) on the remineralization of enamel defects via micro-focus x-ray computed tomography and nanoindentation.

    Biomed Mater. 2015;10(3):035007

    Authors: Hossein BG, Sadr A, Espigares J, Hariri I, Nakashima S, Hamba H, Shafiei F, Moztarzadeh F, Tagami J

    Abstract
    Regeneration of severely damaged enamel (e.g. deep demineralized lesions) is currently not possible, because the structural units of enamel crystal construction are removed after its maturation. The aim of this in vitro study was to evaluate the effect of surface impregnation by leucine-rich amelogenin peptide (LRAP) on the remineralization of eroded enamel using micro-focus x-ray computed tomography (µCT). Fifteen bovine enamel blocks were embedded in resin and three zones (sound, demineralization, and remineralization) were defined on each specimen. Lesions were prepared by immersing the samples in demineralization solution for 7 d. The samples were soaked in distilled water or 60 or 120 µg mL(-1) solution of LRAP in water for 30 min. After the surface treatment, specimens were incubated in artificial saliva for either 5 or 10 d at 37 °C. The amount of mineral gain (dΔZ%) and the relative changes in the lesion depth (dLD%), obtained from µCT, were used to evaluate the effect of LRAP on the remineralization of lesions. The effects of LRAP on cross-sectional integrated hardness ΔINH were studied after 10 d using nanoindentation. ANOVA test was used to determine the effect of time and/or LRAP concentration on dΔZ%, dLD% and ΔINH mean values. Tukey’s analysis was used for multiple comparison testing (α = 0.05). Analysis of µCT data showed significant effect of time and LRAP concentration on the dΔZ% (p = 0.013, p = 0.003) and the dLD% (p  <  0.001, p = 0.002) mean values. The nanoindentation hardness was significantly improved by 120 µg mL(-1) LRAP (p = 0.02). Also, the peptide treatment affected the mineral distribution throughout the lesion by inhibiting of superficial deposition. This study showed that the treatment of eroded lesions in enamel by LRAP can improve and regulate the pattern of remineralization in vitro.

    (26041048) – in process]

    Bibliography

  • In situ characterization of resin-dentin interfaces using conventional vs. cryofocused ion-beam milling.
    .

    In situ characterization of resin-dentin interfaces using conventional vs. cryofocused ion-beam milling.

    Dent Mater. 2015 May 15;

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

    Abstract
    OBJECTIVE: The introduction of focused ion beam (FIB) milling has facilitated preparation of hard tissue samples for transmission electron microscope (TEM). However, this technique generates high temperature that may alter or damage morphological features in biological tissue. Therefore, the aim of this study was to determine the effects of cryogenic cooling on the morphological features of dentin interfaces with dental restorative materials in samples prepared by FIB for TEM examination.
    METHODS: After preparation of a cylindrical-shaped cavities in extracted, non-carious premolar teeth, the specimens were restored with dental adhesive/composite and categorized into two restorative materials groups; (PB) a combination of Clearfil Protect Bond (Kuraray Noritake Dental, Japan)/Estelite Sigma Quick composite (Tokuyama Dental, Japan), and (SB) Filtek Silorane restorative system (3M ESPE, USA). The specimens were subjected to interfacial cross-sectioning, followed by observation and area selection using confocal laser microscopy. Later, ultrathin sections were prepared using FIB with cryogenic cooling (PB-C) and (SB-C), or without cooling (PB-NC) and (SB-NC) that all were examined under TEM.
    RESULTS: Resulting TEM images of the ultra-morphological features at the resin-dentin nano-interaction zone were improved when FIB preparation was conducted in the cryogenic condition and no sign of artifacts were detected.
    SIGNIFICANCE: Conducting ion beam milling with cryogenic cooling was advantageous in minimizing the elevation in specimen temperature. This led to preservation of dentin microstructures that revealed additional information about substrates that are necessary for advanced characterization of tooth-biomaterial interactions.

    (25986333) – as supplied by publisher]

    Bibliography

  • Evaluation of a new hardness tester (Cariotester): Comparison with transverse microradiography for assessing the inhibitory effect of fluoride application on bovine root dentin demineralization.
    .

    Evaluation of a new hardness tester (Cariotester): Comparison with transverse microradiography for assessing the inhibitory effect of fluoride application on bovine root dentin demineralization.

    Dent Mater J. 2015 May 1;

    Authors: Sugawara T, Nakashima S, Shimizu A, Tagami J, Momoi Y

    Abstract
    The objective of this study was to investigate the correlation between CT depth, indentation depth determined by a new hardness tester (Cariotester), and the transverse microradiography (TMR) parameters, i.e., lesion depth and mineral loss. For that purpose, this study evaluated the feasibility of using Cariotester as a root caries diagnostic system and capability of Cariotester to detect effect of fluoride application on inhibiting dentin demineralization. Fluorides were applied to bovine root dentin specimens, which were subsequently demineralized for 1-21 days and then CT depth and TMR parameters were assessed. There were significant correlations between CT depth and TMR parameters in fluoride and non-fluoride groups. There were significant differences between fluoride and non-fluoride groups for CT depth and TMR parameters respectively. Current results suggested that Cariotester may be capable of providing an objective evaluation of root caries progression and the fluoride effect on inhibiting dentin demineralization.

    (25948139) – as supplied by publisher]

    Bibliography

  • Validation of Optical Coherence Tomography against Micro-computed Tomography for Evaluation of Remaining Coronal Dentin Thickness.
    .

    Validation of Optical Coherence Tomography against Micro-computed Tomography for Evaluation of Remaining Coronal Dentin Thickness.

    J Endod. 2015 May 1;

    Authors: Majkut P, Sadr A, Shimada Y, Sumi Y, Tagami J

    Abstract
    INTRODUCTION: Optical coherence tomography (OCT) is a noninvasive modality to obtain in-depth images of biological structures. A dental OCT system has become available for chairside application. This in vitro study hypothesized that swept-source OCT can be used to measure the remaining dentin thickness (RDT) at the roof of the dental pulp chamber during excavation of deep caries.
    METHODS: Human molar teeth with deep occlusal caries were investigated. After obtaining 2-dimensional and 3-dimensional OCT scans using a swept-source OCT system at a 1330-nm center wavelength, RDT was evaluated by image analysis software. Microfocus x-ray computed tomographic (micro-CT) images were obtained from the same cross sections to confirm OCT findings. The smallest RDT values at the visible pulp horn were measured on OCT and micro-CT imaging and compared using the Pearson correlation. Pulpal horns and pulp chamber roof observation under OCT and micro-CT imaging resulted in comparable images that allowed the measurement of coronal dentin thickness.
    RESULTS: RDT measured by OCT showed optical values range between 140 and 2300 μm, which corresponded to the range of 92-1524 μm on micro-CT imaging. A strong correlation was found between the 2 techniques (r = 0.96, P < .001).
    CONCLUSIONS: Further analysis indicated linear regression with a slope of 1.54 and no intercept, closely matching the bulk refractive index of dentin. OCT enables visualization of anatomic structures during deep caries excavation. Exposure of the vital dental pulp because of the removal of very thin remaining coronal dentin can be avoided with this novel noninvasive technique.

    (25937180) – as supplied by publisher]

    Bibliography

  • Effect of phytic acid etchant on the structural stability of demineralized dentine and dentine bonding.
    .

    Effect of phytic acid etchant on the structural stability of demineralized dentine and dentine bonding.

    J Mech Behav Biomed Mater. 2015 Apr 6;48:145-152

    Authors: Kong K, Islam MS, Nassar M, Hiraishi N, Otsuki M, Yiu CK, Tagami J

    Abstract
    OBJECTIVE: This study examined the effect of phytic acid (IP6) in stabilizing the morphology of dentine collagen network and resin-dentine bonding.
    METHODS: Dentine beams were fully demineralized with 10% phosphoric acid (PA) or 1% IP6 (pH 1.2). PA-demineralized beams were divided into three groups: (a) no further treatment (control), (b) treatment with 5% glutaraldehyde (GA) for 1h and (c) treatment with 1% IP6 (pH 7) for 1h. IP6-demineralized beams received no further treatment. The beams were then subjected to ultimate tensile strength (UTS) testing. Dentine micromorphology evaluation was performed using a field-emission scanning electron microscope (FE-SEM). Dentine disks were etched with 35% PA for 15s or 1% IP6 for 30s. PA-etched dentine disks were divided into three groups as (a), (b) and (c) as for UTS testing, but the treatment with GA or IP6 was done in 1min. For microtensile bond strength (µTBS) testing, flat dentine surfaces etched with PA or IP6 were blot-dried (wet dentine) or air-dried for 10s (dry dentine) and bonded with an etch-and-rinse adhesive followed by composite build-up.
    RESULTS: IP6-demineralized dentine showed significantly higher UTS, when compared to PA-demineralized dentine. GA and IP6 significantly improved UTS of PA-demineralized dentine. FE-SEM observation revealed that dentine collagen network was preserved by GA and IP6. No significant difference in µTBS was found between the wet and dry IP6-etched dentine groups.
    CONCLUSION: IP6 etching showed a structural stabilizing effect on demineralized dentine matrix and produced good resin-dentine bonding, regardless of dentine moistness or dryness.

    (25933170) – as supplied by publisher]

    Bibliography

  • Assessment of natural enamel lesions with optical coherence tomography in comparison with microfocus x-ray computed tomography

    Assessment of natural enamel lesions with optical coherence tomography in comparison with microfocus x-ray computed tomography

    Espigares J, Sadr A, Hamba H, Shimada Y, Otsuki M, Tagami J, Sumi Y.

    J. Med. Imag. 2(1), 014001 (Feb 11, 2015). doi:10.1117/1.JMI.2.1.014001

    A technology to characterize early enamel lesions is needed in dentistry. Optical coherence tomography (OCT) is a noninvasive method that provides high-resolution cross-sectional images. The aim of this study is to compare OCT with microfocus x-ray computed tomography (μCT ) for assessment of natural enamel lesions in vitro. Ten human teeth with visible white spot-like changes on the enamel smooth surface and no cavitation (ICDAS code 2) were subjected to imaging by μCT (SMX-100CT, Shimadzu) and 1300-nm swept-source OCT (Dental SS-OCT, Panasonic Health Care). In μCT , the lesions appeared as radiolucent dark areas, while in SS-OCT, they appeared as areas of increased signal intensity beneath the surface. An SS-OCT attenuation coefficient based on Beer–Lambert law could discriminate lesions from sound enamel. Lesion depth ranged from 175 to 606  μm in SS-OCT. A correlation between μCT and SS-OCT was found regarding lesion depth (R=0.81 , p<0.001 ) and also surface layer thickness (R=0.76 , p<0.005 ). The images obtained clinically in real time using the dental SS-OCT system are suitable for the assessment of natural subsurface lesions and their surface layer, providing comparable images to a laboratory high-resolution μCT without the use of x-ray.

  • Optical coherence tomography for evaluation of enamel and protective coatings.
    .

    Optical coherence tomography for evaluation of enamel and protective coatings.

    Dent Mater J. 2015;34(1):98-107

    Authors: Alsayed EZ, Hariri I, Sadr A, Nakashima S, Bakhsh TA, Shimada Y, Sumi Y, Tagami J

    Abstract
    Optical coherence tomography (OCT) is an interferometric imaging technique. This study aimed to employ OCT to evaluate four different resin-based materials including a coating containing glass-ionomer filler and calcium, a giomer, and two fluoride-releasing self-etch resins. The coating and its underlying and adjacent enamel were monitored using swept-source OCT (center wavelength: 1330 nm) at baseline, after 5,000 thermal cycles, and after 1, 4 and 7 days of demineralization (pH 4.5). The coatings showed different thicknesses (60-250 micrometers) and various levels of structural and interfacial integrity. OCT could detect a demineralization inhibition zone adjacent to the edge of the fluoride- and calcium-releasing material. Localized demineralization was occasionally observed under thinner coatings. Protection of susceptible enamel surfaces by thin resin-based bioactive coatings provides protection from demineralization. OCT can be used to non-destructively monitor the integrity of such coatings, as well as enamel changes beneath and adjacent to them.

    (25748465) – in process]

    Bibliography

  • The role of MDP in a bonding resin of a two-step self-etching adhesive system.
    .

    The role of MDP in a bonding resin of a two-step self-etching adhesive system.

    Dent Mater J. 2015 Feb 24;

    Authors: Matsui N, Takagaki T, Sadr A, Ikeda M, Ichinose S, Nikaido T, Tagami J

    Abstract
    The purpose of this study was to evaluate the role of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) contained in the bonding resin of a two-step self-etch adhesive system. An experimental adhesive (M0) containing MDP only in the primer, but not in the bonding resin was prepared. Clearfil SE Bond (MM) and M0 were compared in terms of microtensile bond strength to dentin, ultimate tensile strength of the bonding resin, and dentin-resin bonding interface morphology under SEM and TEM. The immediate µTBS values of MM significantly decreased after thermal cycles while M0 were stable even after 10,000 cycles. In the SEM observations, formation of erosion was observed beneath the acid-base resistant zone only in M0. The results suggested that MDP in the bonding resin of the two-step self-etching system; 1) improved the immediate bond strength, but caused reduction in long-term bond durability; 2) offered the advantages of acid-base resistance at the ABRZ forefront area.

    (25740167) – as supplied by publisher]

    Bibliography

  • Age-specific prevalence of erosive tooth wear by acidic diet and gastroesophageal reflux in Japan.
    .

    Age-specific prevalence of erosive tooth wear by acidic diet and gastroesophageal reflux in Japan.

    J Dent. 2015 Feb 12;

    Authors: Kitasako Y, Sasaki Y, Takagaki T, Sadr A, Tagami J

    Abstract
    OBJECTIVES: To evaluate the age-specific prevalence of erosive tooth wear in Japanese adults.
    METHODS: The study sample consisted of a total of 1,108 adults aged 15 to 89 yrs in Tokyo, Japan. The subjects were asked to complete a self-administered nutrition-related questionnaire. Two examiners evaluated tooth wear in a full-mouth recording, using a modified tooth wear index developed based on the Smith and Knight Tooth Wear index. Subjects who had frequent acid consumption or gastric reflux and at least one tooth with an initial enamel smooth surface wear were placed in an erosive wear positive group, and the rest of subjects were placed in the erosive wear negative group.
    RESULTS: The median (IQR) prevalence of erosion was 19.1 (1.8) at enamel level and 6.5 (3.7) with dentin exposure. There were statistical differences in prevalence of erosive wear among different age groups (p<0.05). Dietary habits found to be frequent in erosive wear positive group included acidic juices for younger subjects (15-39 yrs), and acidic fruits for older subjects (60-89 yrs). The prevalence of gastroesophageal reflux and eating disorder was 3.5%. A severe loss of dental tissue was observed on labial and incisal surfaces of anterior teeth in the erosive wear positive group.
    CONCLUSIONS: In the studied sample of Japanese adults, 26.1% had signs of erosive wear. Clinical significance: Erosive wear, in combination with abrasion and attrition, results in severe loss of tooth tissue. Frequent consumption of acidic fruits and drinks was significantly associated with erosive tooth wear at different age groups.

    (25684603) – as supplied by publisher]

    Bibliography

  • Self-etch adhesive systems: a literature review.
    .

    Self-etch adhesive systems: a literature review.

    Braz Dent J. 2015 Jan-Feb;26(1):3-10

    Authors: Giannini M, Makishi P, Ayres AP, Vermelho PM, Fronza BM, Nikaido T, Tagami J

    Abstract
    This paper presents the state of the art of self-etch adhesive systems. Four topics are shown in this review and included: the historic of this category of bonding agents, bonding mechanism, characteristics/properties and the formation of acid-base resistant zone at enamel/dentin-adhesive interfaces. Also, advantages regarding etch-and-rinse systems and classifications of self-etch adhesive systems according to the number of steps and acidity are addressed. Finally, issues like the potential durability and clinical importance are discussed. Self-etch adhesive systems are promising materials because they are easy to use, bond chemically to tooth structure and maintain the dentin hydroxyapatite, which is important for the durability of the bonding.

    (25672377) – in process]

    Bibliography

  • Formation and characterization of hypermineralized zone beneath dentine lesion body induced by topical fluoride in-vitro.

    Formation and characterization of hypermineralized zone beneath dentine lesion body induced by topical fluoride in-vitro.

    Arch Oral Biol. 2015 Jan 10;60(4):574-581

    Authors: Khunkar SJ, Utaka S, Hariri I, Sadr A, Ikeda M, Nakashima S, Nikaido T, Tagami J

    Abstract
    OBJECTIVE: This in-vitro study aimed to evaluate and characterize the hypermineralized zone (Hyper-zone) formed beneath the remineralized dentine lesion body by transverse microradiography (TMR), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS).
    DESIGN: Demineralized bovine dentine specimens were treated with fluoride solutions (APF, NaF) and remineralized for 2-4 weeks. Then thin sections were prepared to characterize the Hyper-zone by TMR, EDS. Fractured specimen surfaces were observed by SEM.
    RESULTS: TMR analysis revealed a higher mineral density at Hyper-zone than that of sound dentine (48vol%) ranging from 50 up to 61vol% and the thickness ranging from 197 to 344μm for 4-week specimens, while specimens without fluoride treatment did not show Hyper-zone. SEM pictures at Hyper-zone showed no evident crystal-like deposits in dentinal tubules and no notable difference when compared to that in sound dentine. EDS analysis demonstrated higher concentrations of Ca and P at Hyper-zone than those in sound dentine, which corresponded to the TMR profile, while the magnesium (Mg) concentration was low at this zone.
    CONCLUSIONS: Demineralized dentine lesions exposed to fluoride and remineralization treatments exhibited Hyper-zone beneath the lesion body, in which the mineral density was higher than that of sound dentine. Possible mechanism for the formation of Hyper-zone was discussed by assuming removal of mineral regulators such as Mg and other organic substances from sound dentine during de-/remineralization processes.

    (25616245) – as supplied by publisher]

    Bibliography

  • Immobilization of phosphate monomers on collagen induces biomimetic mineralization.
    .

    Immobilization of phosphate monomers on collagen induces biomimetic mineralization.

    Biomed Mater Eng. 2015 Jan 1;25(1):89-99

    Authors: Nurrohman H, Nakashima S, Takagaki T, Sadr A, Nikaido T, Asakawa Y, Uo M, Marshall SJ, Tagami J

    Abstract
    BACKGROUND: Immobilization of phosphoproteins on type-I collagen via covalent binding may induce extra- and intrafibrillar mineralization.
    OBJECTIVE: This study tested the hypothesis that methacrylate phosphate esters immobilized on reconstituted type-I collagen can mimic the nucleating role of phosphoproteins.
    METHODS: Three functional monomers (MDP, GPDM and Phenyl-P) that differed in chemical structure and steric hindrances around the phosphate moiety were evaluated. Reconstituted type-I collagen was either left untouched (control) or treated by 5% monomer/ethanol for 20 s. All samples were incubated in simulated dentinal fluid as mineralizing medium at 37°C for 7 or 14 days. The extra- and intrafibrillar mineralization were examined by SEM and TEM/SAED crystallography, respectively.
    RESULTS: FT-IR spectroscopy showed that the phosphate groups were incorporated on reconstituted collagen, irrespective of their chemical structure. MDP immobilization induced dense growth of extrafibrillar mineral over time, while with GPDM- and Phenyl-P-immobilized collagen, mineralization was moderate and sparse, respectively. TEM/SAED evidence disclosed that intrafibrillar minerals exclusively occurred in MDP-immobilized collagen.
    CONCLUSIONS: Immobilization of MDP, which had the lowest steric hindrance, could induce significant biomimetic extra- and intrafibrillar mineralization; resembling the lowest level of hierarchy organization of dentin.

    (25585983) – in process]

    Bibliography

  • 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

  • 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