- Characterization of transparent dentin in attrited teeth using optical coherence tomography.
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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
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.
PMID: 24532117 [PubMed - as supplied by publisher]
- Detection of occlusal caries in primary teeth using swept source optical coherence tomography.
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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. 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.
PMID: 24474506 [PubMed - in process]
- Evaluation of new treatment for incipient enamel demineralization using 45S5 bioglass.
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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
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.
PMID: 24433821 [PubMed - as supplied by publisher]
- Nanoindentation hardness of intertubular dentin in sound, demineralized and natural caries-affected dentin.
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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
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.
PMID: 24394774 [PubMed - as supplied by publisher]
- Dental Pulp Dendritic Cells Migrate to Regional Lymph Nodes.
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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
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.
PMID: 24378366 [PubMed - as supplied by publisher]
- Effect of smear layer deproteinizing on resin-dentine interface with self-etch adhesive.
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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
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.
PMID: 24321293 [PubMed - as supplied by publisher]
- The inhibition effect of non-protein thiols on dentinal matrix metalloproteinase activity and HEMA cytotoxicity.
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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
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.
PMID: 24316344 [PubMed - as supplied by publisher]
- 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
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.
PMID: 24240907 [PubMed - as supplied by publisher]
- 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
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.
PMID: 24240894 [PubMed - as supplied by publisher]
- The effect of glutathione on 2-hydroxyethylmethacrylate cytotoxicity and on resin-dentine bond strength.
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The effect of glutathione on 2-hydroxyethylmethacrylate cytotoxicity and on resin-dentine bond strength.
Int Endod J. 2013 Oct 9;
To evaluate the influence of reduced glutathione (GSH) application on 2-hydroxyethylmethacrylate (HEMA) cytotoxicity on rat pulpal cells and evaluate the effect of etched-dentine treatment with GSH on the immediate microtensile bond strength (μTBS) of etch-and-rinse adhesive.
The cytotoxicity of 10 mmol L-1 HEMA, 10 mmol L-1 HEMA + 1 mmol L-1 GSH, 10 mmol L-1 HEMA + 5 mmol L-1 GSH and 10 mmol L-1 HEMA + 10 mmol L-1 GSH was compared (6 h and 24 h). Cells viability was measured by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, followed by morphological observation of cells. Etched-dentine surfaces were rinsed and treated with one of the following solutions: 2% GSH, 5% GSH or 10% GSH, bonded with Adper Single Bond Plus (3M, ESPE, St. Paul, MN, USA) and restored with resin composite. The control group received no GSH treatment. After 1 day of water-storage at 37 °C, the specimens were subjected to μTBS testing. Cytotoxicity and μTBS data were analysed by one-way anova and Tukey post hoc tests (P < 0.05).
There were significant differences between the groups. HEMA elicited a remarkable toxic effect. 10 mmol L-1 GSH prevented HEMA-induced damage at both exposure times. Whilst 5 mmol L-1 GSH lost its protective effect at 24-h exposure time and 1 mmol L-1 GSH showed no protective effect at both exposure times, GSH had no significant effect on the immediate μTBS; however, 5% GSH had higher bond strength value when compared to 10% GSH (P = 0.003).
Controlled concentrations of GSH had a protective effect against HEMA cytotoxicity. GSH had neither positive nor negative influence on μTBS.
PMID: 24117849 [PubMed - as supplied by publisher]
- Effects of solvent drying time on mass change of three adhesives.
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Effects of solvent drying time on mass change of three adhesives.
J Conserv Dent. 2013 9;16(5):418-422
AIM: Adhesives may change their mass due to water sorption or dilution of components after curing. The aim of this study was to evaluate the influence of air-drying time and water storage on mass changes (MC) of three adhesives; Adper Single Bond2 (ASB), One-step plus (OSP), Clearfil S(3) Bond (CSB).
MATERIALS AND METHODS: Rectangular-shape samples from each adhesive were prepared and cured for 120 s with a halogen light curing unit. Prior to curing, their solvent was evaporated by means of three different procedures depending on the passive air-drying time (i.e., no air drying, equal to active air drying, complete evaporation after 3 h). Each group was further divided into two subgroups based on the time of water storage (1-day, 7-days), prior to measurement of MC (n = 10). The data were analyzed using a three-way ANOVA.
RESULTS: Adhesives showed different patterns of MC in relation to air drying and water storage; (P < 0.05). In OSP and CSB with increasing water storage and air drying, the MC increased significantly (P < 0.01).
CONCLUSION: The highest MC in the etch-and-rinse adhesives was observed when the adhesive was not dried, while in the self-etch adhesive the highest changes were observed when the adhesive was completely dried.
PMID: 24082570 [PubMed - as supplied by publisher]
- In vitro evaluation of plant-derived agents to preserve dentin collagen.
In vitro evaluation of plant-derived agents to preserve dentin collagen.
Dent Mater. 2013 Aug 10;
Authors: Hiraishi N, Sono R, Sofiqul I, Yiu C, Nakamura H, Otsuki M, Takatsuka T, Tagami J
OBJECTIVE: Biomodification of dentin by a natural crosslinker has been recommended to improve a mechanical property of demineralized dentin. This study investigated the effect of various plant-derived agents (hesperidin, proanthocyanidin, epigallocatechin gallate and genipin) on the stability of dentin collagen matrix to resist collagenase degradation.
METHODS: The dentin specimens were treated with glutaraldehyde (0.5% and 5.0%) and each plant-derived test solution (0.5%). They were subjected to ultimate tensile strength (UTS) and swelling ratio measurements. Demineralized human dentin powder was incubated with 0.02%, 0.1% and 0.5% of each test agent and followed by bacterial collagenase digestion. The extent of collagen degradation was investigated using hydroxyproline assay.
RESULTS: The UTS and swelling ratio measurements revealed that the mechanical property of dentin was improved by the use of these natural agents. The greatest reduction in collagen degradation was shown following the use of hesperidin, proanthocyanidin, and epigallocatechin gallate at 0.5%.
SIGNIFICANCE: The use of hesperidin, proanthocyanidin, and epigallocatechin gallate could improve the mechanical properties of collagen and resist enzymatic degradation, leading to functional repair of pathological dentin lesion.
PMID: 23942145 [PubMed - as supplied by publisher]
- The importance of size-exclusion characteristics of type I collagen in bonding to dentin matrices.
The importance of size-exclusion characteristics of type I collagen in bonding to dentin matrices.
Acta Biomater. 2013 Aug 5;
Authors: Takahashi M, Nakajima M, Tagami J, Scheffel DL, Carvalho RM, Mazzoni A, Carrilho M, Tezvergil-Mutluay A, Breschi L, Tjäderhane L, Jang SS, Tay FR, Agee KA, Pashley DH
The mineral phase of dentin is located primarily within collagen fibrils. During development, bone or dentin collagen fibrils are formed first and then water within the fibril is replaced with apatite crystallites. Mineralized collagen contains very little water. During dentin bonding, acid-etching of mineralized dentin solubilizes the mineral crystallites and replaces them with water. During the infiltration phase of dentin bonding, adhesive comonomers are supposed to replace all of the collagen water with adhesive monomers that are then polymerized into copolymers. The authors of a recently published review suggested that dental monomers were too large to enter and displace water from collagen fibrils. If that were true, the endogenous proteases bound to dentin collagen could be responsible for unimpeded collagen degradation that is responsible for the poor durability of resin-dentin bonds. The current work studied the size-exclusion characteristics of dentin collagen, using a gel-filtration-like column chromatography technique, using dentin powder instead of Sephadex. The elution volumes of test molecules, including adhesive monomers, revealed that adhesive monomers smaller than about 1000 Da can freely diffuse into collagen water, while molecules of 10,000 Da begin to be excluded, and bovine serum albumin (66,000 Da) was fully excluded. These results validate the concept that dental monomers can permeate between collagen molecules during infiltration by etch-and-rinse adhesives.
PMID: 23928333 [PubMed - as supplied by publisher]
- Effect of a calcium-phosphate based desensitizer on dentin surface characteristics.
Effect of a calcium-phosphate based desensitizer on dentin surface characteristics.
Dent Mater J. 2013;32(4):615-21
Authors: Thanatvarakorn O, Nakashima S, Sadr A, Prasansuttiporn T, Thitthaweerat S, Tagami J
This study aimed to evaluate the ability of a newly developed calcium-phosphate desensitizer in dentin permeability reduction and its integration with dentin surface before and after immersion in artificial saliva (AS) under two different dentin surface characteristics; with or without the collagen exposure.Humandentin discs treated by EDTA to expose collagen fibrils or EDTA/NaOCl to expose plain dentin surface were subjected to a calcium-phosphate desensitizer (Teethmate Desensitizer; TMD), while non-desensitizer treatment served as control. TMD application showed the occlusion in dentinal tubules and reduction in dentin permeability up to 92%, regardless of dentin surface characteristics. After AS immersion, permeability reduction percent (PR%) significantly increased in EDTA/NaOCl pretreatment (p<0.05). Newly-formed crystallites were observed on desensitizer treated dentin and EDTA/NaOCl pretreatment control group, whereas the crystallites did not exist on EDTA pretreatment control group. Ultrasonication revealed the integration of the calcium-phosphate rich layer of desensitizer on dentin surface after AS immersion.
PMID: 23903644 [PubMed - in process]
- Effect of fluoride concentration in adhesives on morphology of acid-base resistant zones.
Effect of fluoride concentration in adhesives on morphology of acid-base resistant zones.
Dent Mater J. 2013;32(4):578-84
Authors: Kirihara M, Inoue G, Nikaido T, Ikeda M, Sadr A, Tagami J
This study aimed to investigate the effect of fluoride concentration in adhesives on morphology of acid-base resistant zone (ABRZ). Seven experimental adhesives with different concentrations of NaF (0 wt%; F0 to 100 wt%: F100) were prepared based on the formulation of a commercially available adhesive (Clearfil Protect Bond, F100). The resin-dentin interface of the bonded specimen was subjected to demineralizing solution and NaOCl, sectioned, polished and argon-ion etched for SEM observation. Fluoride release from each adhesive was measured using an ion-selective electrode. Fluoride ion release from the adhesive linearly increased with higher NaF concentration. The ABRZ area increased significantly with higher NaF concentration except for F0, F10, and F20 (p<0.05). F100 showed the largest ABRZ, where a slope of acid-resistant dentin was clearly observed at the bottom of the ABRZ. The concentration of NaF in the two-step self-etching adhesive resin influenced the amount of dentin structure remaining after acid-challenge.
PMID: 23903639 [PubMed - in process]
- Relationship between perception of difficulty and clinical experience of approximal composite restorations in final-year undergraduate students at Tokyo Medical and Dental University.
Related Articles on PubMed
Relationship between perception of difficulty and clinical experience of approximal composite restorations in final-year undergraduate students at Tokyo Medical and Dental University.
J Med Dent Sci. 2011;58(1):1-5
Authors: Kitasako Y, Sadr A, Nikaido T, Tagami J
The aims of this study were to clarify which steps in approximal restorative procedure were difficult for the final-year undergraduate students at Tokyo Medical and Dental University, and to examine the relationship between perception of difficulty and clinical experience. At mid-term of the clinical education experience, a self-questionnaire was performed by final-year undergraduate students to clarify the difficulty of restorative procedures at the time. There were statistically significant differences in the number of clinical cases experienced at the time between students who designated the matrix application, shade selection and finishing as the easy steps and those who considered them as the difficult ones (Fisher exact test with Bonferroni correction, p < 0.05). There was a significant difference in the total number of procedures designated as difficult between students who had treated above 15 cases and those who had fewer than 15 cases (Wilcoxon rank-sum test, p< 0.05). In the final-year clinical education for operative dentistry, students might need to treat over 15 cases to gain confidence in performing approximal composite restorations independently.
PMID: 23896780 [PubMed - as supplied by publisher]
- Nondestructive assessment of current one-step self-etch dental adhesives using optical coherence tomography.
Related Articles on PubMed
Nondestructive assessment of current one-step self-etch dental adhesives using optical coherence tomography.
J Biomed Opt. 2013 Jul 1;18(7):76020
Authors: Bista B, Sadr A, Nazari A, Shimada Y, Sumi Y, Tagami J
ABSTRACT. This study aimed to nondestructively evaluate sealing performance of eight one-step self-etch adhesives (1-SEAs) using optical coherence tomography (OCT). The two-step self-etch adhesive (2-SEA) served as the control. Round tapered class-I cavities (D=4 mm, H=2 mm) were prepared in bovine incisors, treated with each adhesive (n=5), and restored with a flowable resin composite. Cross-sections were obtained from each restoration using swept-source OCT with 1310-nm laser. The average percentage of the sealed interface (SI%) for each adhesive was calculated using image analysis software, considering increased signal intensity at the interface as gap. Samples were then sectioned and observed under confocal laser scanning microscope (CLSM). Significantly different SI% values were found among different adhesives (analysis of variance, Bonferroni, p<0.05). There was also a significant correlation in SI% between OCT and CLSM (p<0.0001, r=0.96). Additionally, microscopic analysis revealed that the gaps in 1-SEAs occurred not only at dentine-adhesive interfaces but also frequently at adhesive-composite interfaces. Some recent 1-SEAs could achieve reliable short-term sealing comparable to 2-SEA. OCT is a unique tool to nondestructively evaluate the sealing performance of the restoratives through the cavity, provided that cavity walls have a certain minimum inclination with respect to the beam.
PMID: 23887479 [PubMed - in process]
- Effect of phytic acid used as etchant on bond strength, smear layer, and pulpal cells.
Related Articles on PubMed
Effect of phytic acid used as etchant on bond strength, smear layer, and pulpal cells.
Eur J Oral Sci. 2013 Jun 20;
Authors: Nassar M, Hiraishi N, Islam MS, Aizawa M, Tamura Y, Otsuki M, Kasugai S, Ohya K, Tagami J
This study aimed to evaluate the effect of phytic acid (IP6), used as etchant, on resin-dentin bond strength, smear layer removal, and the viability of pulpal cells. Flat dentin surfaces with smear layer were etched with 1% IP6 for 60, 30, or 15 s; in the control group 37% phosphoric acid (PA) was used. Dentin surfaces were rinsed, blot-dried, and bonded with an etch-and-rinse adhesive, followed by composite build-ups. The specimens were subjected to tensile testing after 24 h of water storage at 37°C, and failure modes were determined using scanning electron microscopy. The effectiveness of IP6 to remove the smear layer was observed using scanning electron microscopy. To evaluate the effect on pulpal cells, solutions of 0.1 and 0.01% IP6 and of 3.7 and 0.37% PA were prepared and rat pulpal cells were treated with these solutions for 6 and 24 h. Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The results demonstrated that all application times of IP6 produced bond-strength values that were significantly higher than that of the control. Phytic acid effectively removed the smear layer and plugs, thus exposing the collagen network. Phytic acid had a minimal effect on pulpal cells, whereas PA resulted in a marked decrease in their viability.
PMID: 23879874 [PubMed - as supplied by publisher]
- Mussel-mimetic, bioadhesive polymers from plant-derived materials.
Mussel-mimetic, bioadhesive polymers from plant-derived materials.
J Investig Clin Dent. 2013 Jul 16;
Authors: Hiraishi N, Kaneko D, Taira S, Wang S, Otsuki M, Tagami J
AIM: Mussel-mimetic, bioadhesive polymers are synthesized from plant-derived sources. The strong adhesive action is caused by interactions between the catechol groups at the end of the polymer terminal chains and the substrate surface. Here, we present a preliminary study of the adhesion properties and a discussion of the adhesion mechanism.
METHODS: Two bioadhesive polymers were synthesized from natural plant-derived monomers by the transesterification of: (a) caffeic acid (3,4-dihydroxycinnamic acid; DHCA) and p-coumaric acid (4-hydroxycinnamic acid; 4HCA) to produce poly(DHCA-co-4HCA); and (b) 4-dihydroxyhydrocinnamic acid (DHHCA) and 3-(3-hydroxyphenyl) propionic acid (3HPPA) to produce poly(DHHCA-co-3HPPA). Thermoplastic poly(DHCA-co-4HCA) or poly(DHHCA-co-3HPPA) was placed between glass, carbon, steel, or bovine dentin substrates, and a lap shear adhesion test was conducted to compare them using conventional cyanoacrylate glue and epoxy resin.
RESULTS: The greatest adhesion for all tested substrates was exhibited by poly(DHHCA-co-3HPPA), followed by epoxy resin adhesive, poly(DHCA-co-4HCA), and cyanoacrylate adhesive. The adhesive strength of poly(DHHCA-co-3HPPA) was greater than 25.6 MPa for glass, 29.6 MPa for carbon, 15.7 MPa for steel, and 16.3 MPA for bovine dentin.
CONCLUSION: The adhesion of poly(DHHCA-co-3HPPA) might be the strongest reported for a mussel-mimic adhesive system, and could be a feasible alternative to petroleum adhesives.
PMID: 23857900 [PubMed - as supplied by publisher]
- Combined effect of smear layer characteristics and hydrostatic pulpal pressure on dentine bond strength of HEMA-free and HEMA-containing adhesives.
Related Articles on PubMed
Combined effect of smear layer characteristics and hydrostatic pulpal pressure on dentine bond strength of HEMA-free and HEMA-containing adhesives.
J Dent. 2013 Jul 11;
Authors: Mahdan MH, Nakajima M, Foxton RM, Tagami J
OBJECTIVE: This study evaluated the combined effect of smear layer characteristics with hydrostatic pulpal pressure (PP) on bond strength and nanoleakage expression of HEMA-free and -containing self-etch adhesives.
METHODS: Flat dentine surfaces were obtained from extracted human molars. Smear layers were created by grinding with #180- or #600-SiC paper. Three HEMA-free adhesives (XenoV, G Bond Plus, Beautibond Multi) and two HEMA-containing adhesives (Bond Force, Tri-S Bond) were applied to the dentine surfaces under hydrostatic PP or none. Dentine bond strengths were determined using the microtensile bond test (μTBS). Data were statistically analyzed using three- and two-way ANOVA with Tukey post-hoc comparison test. Nanoleakage evaluation was carried out under a scanning electron microscope (SEM).
RESULTS: Coarse smear layer preparation and hydrostatic PP negatively affected the μTBS of HEMA-free and -containing adhesives, but there were no significant differences. The combined experimental condition significantly reduced μTBS of the HEMA-free adhesives, while the HEMA-containing adhesives exhibited no significant differences. Two-way ANOVA indicated that for HEMA-free adhesives, there were significant interactions in μTBS between smear layer characteristics and pulpal pressure, while for HEMA-containing adhesives, there were no significant interactions between them. Nanoleakage formation within the adhesive layers of both adhesive systems distinctly increased in the combined experimental group.
CONCLUSION: The combined effect of coarse smear layer preparation with hydrostatic PP significantly reduced the μTBS of HEMA-free adhesives, while in HEMA-containing adhesives, these effects were not obvious. Clinical significance: Smear layer characteristics and hydrostatic PP would additively compromise dentine bonding of self-etch adhesives, especially HEMA-free adhesives.
PMID: 23851133 [PubMed - as supplied by publisher]
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