Biomedical subjects

Hidehiko Sano

Publications and source records attributed to Hidehiko Sano.

52 records · Page 3Linked to original sources

PubMed2003

Sublethal, 2-week exposures of dental material components alter TNF-alpha secretion of THP-1 monocytes.

OBJECTIVES: The aim of this study was to investigate the hypothesis that dental material components alter cytokine secretion from monocytes if applied for several weeks at sublethal doses. The current study significantly extended exposure times of monocytes to the components over times published in previous studies. These exposure times approached the estimated average life span of monocytes in the bloodstream. METHODS: Human THP-1 monocytes were exposed to 2-hydroxyethylmethacrylate (HEMA, 0-1.2mmol/l), triethyleneglycoldimethacrylate (TEGDMA, 0-0.75mmol/l), Hg(2+) (0-2 micromol/l), or Ni(2+) (0-20 micromol/l) for 2 weeks. The cells were then collected and additionally incubated for 24h, with or without bacterial lipopolysaccharide (LPS), a common component of dental plaque. TNF-alpha secretion from THP-1 was determined using by enzyme-linked immunosorbent assay. RESULTS: None of the dental material components induced TNF-alpha from THP-1 by themselves, but LPS alone strongly induced TNF-alpha secretion as expected. HEMA and TEGDMA significantly suppressed (40-70%) TNF-alpha secretion from cells stimulated with LPS. Hg(2+) at 2.0 micromol/l doubled TNF-alpha secretion from THP-1s stimulated with LPS over LPS alone. Ni(2+) did not significantly affect TNF-alpha secretion, with or without LPS exposure. Significance. The results in this study suggest that sublethal, 2-week exposures of some dental material components may alter TNF-alpha secretion from THP-1 monocytes when the cells are challenged. These alterations may influence the biological response of tissues to materials in an inflammatory intraoral environment.

Analysis of Variance↗

PubMed2003

In vitro degradation of resin-dentin bonds analyzed by microtensile bond test, scanning and transmission electron microscopy.

Our knowledge of the mechanisms responsible for the degradation of resin-dentin bonds are poorly understood. This study investigated the degradation of resin-dentin bonds after 1 year immersion in water. Resin-dentin beams (adhesive area: 0.9mm(2)) were made by bonding using a resin adhesive, to extracted human teeth. The experimental beams were stored in water for 1 year. Beams that had been stored in water for 24h were used as controls. After water storage, the beams were subjected to microtensile bond testing. The dentin side of the fractured surface was observed using FE-SEM. Subsequently, these fractured beams were embedded in epoxy resin and examined by TEM. The bond strength of the control specimens (40.3+/-15.1MPa) decreased significantly (p<0.01) after 1 year of water exposure (13.3+/-5.6MPa). Loss of resin was observed within fractured hybrid layers in the 1 year specimens but not in the controls. Transmission electron microscopic examination revealed the presence of micromorphological alterations in the collagen fibrils after 1 year of water storage. These micromorphological changes (resin elution and alteration of the collagen fibrils) seem to be responsible for the bond degradation leading to bond strength reduction.

Biocompatible Materials↗

PubMed2003

Resin-enamel bonds made with self-etching primers on ground enamel.

Self-etching primer adhesives have recently been introduced to simplify bonding. However, the fundamental bonding mechanism of self-etching primers to enamel is not yet fully understood. This study aimed to investigate resin-enamel bonds of self-etching primer adhesives on ground enamel. Two self-etching primer adhesives (Clearfil Liner Bond 2 V and Clearfil SE Bond) were used in this study. A total-etch adhesive (One-Step) was used as a control. Resin-enamel beams were subjected to the microtensile bond test. Subsequently, the failure modes of all specimens were quantified using image analysis. Undemineralized and demineralized ultrathin sections of the resin-enamel bonded specimens were examined using transmission electron microscopy. The bond strengths of Clearfil SE Bond (39.8 +/- 11.9 MPa) and One-Step (46.2 +/- 12.7 MPa) were significantly greater than that of Clearfil Liner Bond 2V (30.4 +/- 6.2 MPa). Scanning electron microscopy of the fractured surfaces revealed the failure direction and weakest portion within each bond. Transmission electron microscopy showed a thin hybridized complex of resin in enamel produced by the self-etching primers without the usual micrometer-sized resin tags seen in resin-enamel bonds produced using the total-etch adhesive. The morphological features of the resin-enamel bonds produced by two self-etching primers tested were different from that created with the total-etch adhesive.

Adhesives↗

PubMed2003

Effect of depth and tubule direction on ultimate tensile strength of human coronal dentin.

The purpose of this study was to evaluate the effect of dentin depth and tubule direction on the ultimate tensile strength (UTS) of human dentin. Dentin slabs of 0.5-mm thickness were trimmed either from the mesial and distal (for specimens with the tubules parallel to the tensile force; parallel group) or from the occlusal and pulpal surfaces (perpendicular group) to reduce the cross-sectional area of the superficial, middle, and deep regions to 0.25 mm2, and subjected to microtensile testing. From SEM photomicrographs of the fractured specimens of the parallel group, the tubule density was investigated. For both parallel and perpendicular groups, superficial dentin showed a significantly higher UTS than deep dentin. The tubule density of superficial dentin was significantly lower than that of middle and deep dentin. When performing the microtensile bond test to deep dentin, it is possible that cohesive failure of dentin can occur at relatively low tensile stresses.

Dental Restoration Failure↗

PubMed2003

Contraction stress of composite resin build-up procedures for pulpless molars.

PURPOSE: The purpose of this study was to photoelastically evaluate contraction stresses associated with various resin composite build-up procedures for pulpless molars. MATERIALS AND METHODS: Photoelastic models of endodontically treated mandibular molars were fabricated to simulate a preparation for a full-cast crown. The model configuration included three lateral walls, but no post space. The buildups were made with dual-curing resin composite using the following procedures: 1) bulk dual cure, 2) bulk chemical cure, 3) horizontal two increments, dual cure, and 4) indirect. Five specimens were fabricated for each condition. The stresses developed in the models were recorded photographically in the field of a circular polariscope. RESULTS: The build-up procedures tested generated widely different stress distributions and intensities. The highest stresses were seen with the bulk dual-cure method. The slower polymerization chemical-cure group developed distributions similar to the bulk dual-cure group with a significantly lower fringe order. The two horizontal increments dual-cure techniques developed an individual group of fringes for each layer. Compared with the bulk dual-cure group, stresses around the occlusal margin were reduced by incrementalization, while fringes were more closely spaced at the line angles with a slightly lower fringe order. The indirect method demonstrated the lowest stress which extended over the smallest area. CONCLUSION: Contraction stress in resin composite buildups varied significantly depending upon the procedures of fabrication. The bulk dual-cure method developed the most severe contraction stresses, while the indirect technique resulted in significantly lower contraction stresses than the other techniques tested.

Analysis of Variance↗

PubMed2003

Microtensile bond strength of eleven contemporary adhesives to enamel.

PURPOSE: To compare the microtensile bond strength (microTBS) to enamel of 10 contemporary adhesives, including three one-step self-etch systems, four two-step self-etch systems and three two-step total-etch systems, with that of a conventional three-step total-etch adhesive. METHODS: Resin composite (Z100, 3M) was bonded to flat, #600-grit wet-sanded enamel surfaces of 18 extracted human third molars using the adhesives strictly according to the respective manufacturer's instructions. After storage overnight in 37 degrees C water, the bonded specimens were sectioned into 2-4 thin slabs of approximately 1 mm thickness and 2.5 mm width. They were then trimmed into an hourglass shape with an interface area of approximately 1 mm2, and subsequently subjected to microTBS-testing with a cross-head speed of 1 mm/minute. RESULTS: The microTBS to enamel varied from 3.2 MPa for the experimental one-step self-etch adhesive PQ/Universal (self-etch) to 43.9 MPa for the two-step total-etch adhesive Scotchbond 1. When compared with the conventional three-step total-etch adhesive OptiBond FL, the bond strengths of most adhesives with simplified application procedures were not significantly different, except for two one-step self-etch adhesives, experimental PQ/Universal (self-etch) and One-up Bond F, that showed lower bond strengths. Specimen failures during sample preparation were recorded for the latter adhesives as well.

Composite Resins↗

PubMed2003

Color differences and color changes in Vita Shade tooth-colored restorative materials.

PURPOSE: To evaluate the color differences of four tooth-colored restorative materials of the same designated Vita shade, and the color changes of the materials caused by light curing. METHODS: CIELAB coordinates (L* a* b*) of four tooth-colored materials: Clearfil ST (CL), Beautifil (BE), Reactmer (RE) and Z250 (Z2) were determined in three shades (A2, A3 and B3) before and after light curing using a colorimeter. From the L* a* b* after light curing, CIELAB color differences (deltaE*) between different cured materials of the same shade name were calculated. If the calculated deltaE* were above 2, color differences were estimated as "perceptible". DeltaE* was also calculated before and after light curing, using the CIELAB values, in order to evaluate color changes caused by light curing. RESULTS: As for the deltaE* between various cured materials of the same shade, except for deltaE* between BE and RE on A2 and between BE and RE on A3, every combination indicated perceptible color differences. The deltaE* calculated before and after light curing of A2, A3 and B3 shades were 7.4, 7.1 and 7.2 for CL, 6.0, 5.1 and 4.8 for BE, 4.0, 3.2 and 3.4 for RE and 1.8, 1.7 and 2.1 for Z2, respectively, indicating that most materials showed perceptible color changes.

Analysis of Variance↗

PubMed2002

Micromorphological changes in resin-dentin bonds after 1 year of water storage.

The purpose of this study was to evaluate the degradation of resin-dentin bonds after 1 year of water storage. Resin-dentin-bonded specimens were prepared with the use of an adhesive resin system (One-Step: Bisco). Half of the experimental specimens were sectioned perpendicular to the adhesive interface to produce a beam (adhesive area: 0.9 mm(2)) before being stored in distilled water at 37 degrees C for 1 year. The remaining half of the bonded specimens were sectioned into beams of similar dimensions after 1 year of water storage. Additional bonded specimens that had been stored in water for 24 h before sectioning into beams were used as controls. The beams in the two experimental groups and the control group were subjected to microtensile bond testing. Fractography was performed on all fractured beams with the use of FE-SEM. There were significant (p <.05) differences in bond strength among the control specimens (55.9 +/- 12.9 MPa), specimens that had been sectioned into beams after water storage (68.9 +/- 18.6 MPa), and specimens that had been sectioned into beams before water storage (28.1 +/- 9.3 MPa). Fractography revealed that the resin material was gradually extracted from the periphery to the center portion of the beam. This probably accounted for the decrease in bond strength after 1 year of water storage.

Bicuspid↗

PubMed2002

Effect of NaOCl treatment on bond strength between indirect resin core-buildup and dentin.

The aim of this study was to investigate the bond strength between indirect resin core-buildup and dentin treated with or without hypochlorite (NaOCl) gel. The post-space was made in five extracted human molars with obturated root canals, and the indirect resin core was produced on a gypsum model. Then, the dentin surface was treated with/without NaOCl, followed by luting of the resin core into the cavity. After storage for 24 h in 37 degrees C water, the specimens were sectioned for measuring bond strength to the root and coronal dentin, and were subjected to micro-tensile bond strength (MTBS) testing. Two-way ANOVA showed that significant differences in MTBS were revealed for both factors of NaOCl treatment and dentin region. It is concluded that, for indirect resin core-buildup, the proper use of the NaOCl gel to dentin could increase the bond strength.

Acid Etching, Dental↗

PubMed2002

Relation of enamel prism orientation to microtensile bond strength.

PURPOSE: To evaluate the effect of enamel prism orientation on microtensile bond strengths (MTBS) to enamel using two current bonding systems. MATERIALS AND METHODS: The crown segments of extracted human third molars were cut mesio-distally to obtain buccal and lingual halves. One of the halves was cut horizontally at the middle of the crown to make a flat enamel surface parallel to prism orientation (parallel specimen). The other half was ground at the equator of the crown to produce a flat enamel surface perpendicular to the prism orientation (perpendicular specimen). Each surface was ground with 600 grit silicone carbide paper, treated with Clearfil Liner Bond IIsigma (LB) or Single Bond (SB) according to the manufacturers' instructions and resin composite, AP-X or Z100, respectively, was built up onto it. After storage in water at 37 degrees C for 24 hours, all bonded specimens were sectioned and trimmed for measuring MTBS. In MTBS, the parallel specimens were stressed perpendicular to the prism long axis and the perpendicular specimens were stressed parallel to the prism axis. RESULTS: MTBS of specimens stressed perpendicular to the prism long axis were 11.93 +/- 5.56 MPa for LB and 10.97 +/- 1.80 MPa for SB. MTBS of specimens stressed parallel to the prism axis in LB and SB were 19.07 +/- 6.35 MPa and 23.99 +/- 9.20 MPa, respectively. For each prism orientation, no difference in MTBS was found between the bonding systems (P> 0.05). Both systems showed lower MTBS in specimens stressed perpendicular to the prism long axis than in specimens stressed parallel to the prism axis.

Acid Etching, Dental↗

PubMed2002

In vivo long-term durability of the bond to dentin using two adhesive systems.

PURPOSE: The objective of this work was to evaluate the in vivo long-term durability of bond strength and morphological appearance of interfaces between dentin and two adhesive systems. MATERIALS AND METHODS: Class V cavities were prepared on the facial surfaces of 6 intact teeth of a monkey, and restored with Unifil Bond/Unifil F and Fuji Bond LC/Clearfil AP-X. One year later, 10 other teeth were restored with the same materials and the monkey was sacrificed after 24 hours. For in vitro examination, 6 more teeth were extracted from the monkey, restored in a similar manner with the two materials, and stored in 37 degrees C water for 1 day. All specimens were subjected to the microtensile bond strength (microTBS) test. The debonded surfaces of specimens were morphologically observed with the FE-SEM. RESULTS: There were no statistically significant differences among the mean microTBS obtained for Unifil Bond/Unifil F under the three conditions (1 day and 1 year in vivo, and 1 day in vitro), and most specimens showed cohesive failure within resin composite (Unifil F). However, FE-SEM observations showed that resinous material within the hybrid layer made by Unifil Bond seemed to increase in porosity after 1 year. For Fuji Bond LC/Clearfil AP-X, pTBS at 1 day in vitro was significantly higher than that at 1 year in vivo, and bond strengths in vivo tended to decrease over time, although a statistically significant difference was not observed. From FE-SEM observations, most specimens showed cohesive failure within the adhesive (Fuji Bond LC). CONCLUSION: Bond strengths of the two adhesive systems tended to decrease for 1 year in vivo.

Adhesiveness↗

PubMedDate not supplied

Prevention of artificial caries: effect of bonding agent, resin composite and topical fluoride application.

This study investigated the effect of fluoride containing resin composites and bonding agents, as well as the topical fluoride (F) application on the inhibition of artificial caries progression by using a pH-cycling model with alternating demineralizing (pH:4.5) and remineralizing (pH:7.0) solutions. Two bonding systems (F-containing bonding system [Reactmer Bond: RB] and non-F containing bonding system [Clearfil SE Bond: SE]), two resin composites, (F-containing [Reactmer Paste: RP] and non-F containing [Clearfil AP-X: AP]) were used. A combination of each bonding agent and a resin composite, RB+RP, RB+AP, SE+RP and SE+AP, was placed in 2 x 3 x 1.5-mm cavities on root dentin of extracted molars (n=96). Specimens were subjected to pH-cycling for 6 or 12 weeks. Half of all specimens were immersed in 0.05% NaF solution for 1 minute once a day as a topical F application. After the pH cycling period, a microradiograph of each specimen was taken, and the outer lesion depth of the artificial caries was measured by means of image analyzing software. The depths of the outer lesions at different periods were analyzed by one-way ANOVA and Sheffe's test at p=0.05. The combination that received F treatment showed reduced lesion depth compared to the same combination without F application. Except for the F application group of 12 weeks, there was no significant difference in lesion depth among each bonding and composite combination (p>0.05). At week 12 with the F application, RB+RP showed the shallowest lesion compared to the other combinations (p<0.05). The results indicated that the F application reduced the progression of artificial caries. Moreover, the combination of fluoride containing bonding agent and restorative material was the most effective for the inhibition of artificial caries progression based on the 12-week experimental period with topical F application.

Cariostatic Agents↗

PubMedDate not supplied

Effect of different bur grinding on the bond strength of self-etching adhesives.

This study compared the microtensile bond strength (MTBS) of three all-in-one adhesive systems and a two-step system using two types of burs to prepare the dentin surfaces. Flat coronal surfaces of 24 extracted human molars were produced using either regular-grit or superfine-grit diamond burs. Resin composite was then bonded to equal numbers of these surfaces using one of the four adhesives: Clearfil SE Bond (CSE), G-Bond (GB), SSB-200 (SSB) or Prompt L-Pop (PLP). After storage for 24 hours in 37 degrees C distilled water, the bonded teeth were sectioned into slices (0.7-mm thick) perpendicular to the bonded surface. The specimens were then subjected to microtensile testing and the bond strengths were calculated at failure. Bond strength data were analyzed by two-way ANOVA and the GamesHowell test for interaction between adhesive and type of cut dentin. The fractured surfaces were observed by SEM to determine the failure mode. In addition, to observe the effect of conditioning, equal numbers of the two bur-cut dentin surfaces of eight additional teeth were conditioned with the adhesives and observed by SEM. Based on the results, when CSE and SSB were bonded to dentin cut with a regular-grit diamond bur, the MTBS values were significantly lower than that of superfine bur-cut dentin; whereas, GB and PLP showed no significant differences in MTBS between the two differently cut surfaces. SEM observation of the fractured surfaces revealed a mixed mode (adhesive in some areas and cohesive in others in the same sample) of failure in all specimens except PLP, which showed cohesive failure within the adhesive for both types of bur preparation. Generally, SEMs of the conditioned surfaces using both types of burs showed partial removal of the smear layer for CSE, minimal for GB and SSB and complete removal for PLP. In conclusion, when cutting dentin, selecting the proper bur type is important for improving the bond strength of some self-etching adhesive systems.

Adhesiveness↗

PubMedDate not supplied

Change of color and translucency by light curing in resin composites.

OBJECTIVE: This study evaluated color and translucency changes caused by light curing resin composite materials. METHODS: The CIELAB parameters (L*, a* and b*) of disks of A2 and opaque A2 shades of Charisma (Heraeus-Kulzer), Solare (GC) and Filtek Supreme (3M) were evaluated on the backings of black, white and the material itself both before and after light curing to evaluate color and translucency changes (by means of calculating deltaE* and the translucency parameter, respectively). RESULTS: Solare and Filtek Supreme showed significantly smaller color changes during light curing than Charisma; however, the value of deltaE* of all the products/shades was still in the clinically unacceptable range. Regarding translucency changes during light curing, the A2 and opaque A2 shades of Charisma showed a statistically significant increase, although no difference was observed in the other products. CONCLUSIONS: Solare and Filtek Supreme tended to show less changes in translucency and color during light curing compared to Charisma. Nevertheless, the changes in color during light curing were still in the range of unacceptable color change. Therefore, direct shade matching of these materials for a precise shade match should be performed by using the cured material.

Color↗

PubMedDate not supplied

Effects of multiple adhesive coatings on dentin bonding.

Simple changes to bonding techniques can improve resin-dentin bond strengths. This study evaluated the effect of multiple consecutive coatings of adhesive resin on dentin by measuring both microtensile bond strength and nano-leakage following exposure to ammoniacal silver nitrate. Resin-dentin bonded specimens were prepared using two total-etch adhesives (OptiBond Solo Plus/Kerr or Single Bond/3M ESPE). During bonding, resin application and air evaporation were done 1, 2, 3, 4, 6 or 8 times on acid-etched, moist dentin surfaces. Mean microtensile bond strengths were evaluated by two-way ANOVA and Fisher's PLSD test (p<0.05; n=16 for each group). Additionally, nanoleakage of silver nitrate was evaluated by transmission electron microscopy (TEM). The results indicated that bond strengths increased with each coating up to four coats. Nanoleakage decreased with each coat, becoming very small after four or more coats. This adhesive application method can be easily applied to clinical practice, thereby improving the quality of resin-dentin bonds.

Bicuspid↗

PubMedDate not supplied

Effect of conditioner on bond strength of glass-ionomer adhesive to dentin/enamel with and without smear layer interposition.

The effect of a polyalkenoic acid conditioner pretreatment on the bond strength of a glass-ionomer adhesive to tooth substrates with or without smear layer was evaluated. Smear-layer covered and smear-layer free dentin and enamel surfaces were prepared from 24 extracted human molars. Resin composite was bonded to the surfaces using FujiBond LC with or without a polyalkenoic acid conditioner and subjected to microtensile bond strength (microTBS) testing. Failure modes were determined using scanning electron microscopy. For dentin, smear-layer coverage and conditioner treatment did not reveal significant differences in microTBS, which ranged from 20 to 29 MPa. For enamel, smear-layer coverage did not significantly affect microTBS, whereas, the use of conditioner significantly improved microTBS, reaching the same microTBS-values as when bonded to dentin. Regarding failure mode, most dentin specimens failed mixed adhesive cohesively. For enamel, adhesive failures mostly occurred when no conditioner was used, though mixed failures were predominant when the specimens were conditioned beforehand. Bonding of the glass ionomer adhesive to dentin can be achieved without the separate use of a polyalkenoic acid conditioner, even with the interposition of a smear layer. However, instrumented and non-instrumented enamel requires separate conditioning to provide sufficient micro-mechanical retention.

Acrylic Resins↗