Biomedical subjects

Toru Nikaido

Publications and source records attributed to Toru Nikaido.

At least 19 recordsLinked to original sources

PubMed2006

Effect of curing method and storage condition on fluoride ion release from a fluoride-releasing resin cement.

The purpose of this study was to evaluate fluoride ion release from a resin-modified glass ionomer cement (Fuji IILC improved, FLC) and a fluoridated resin cement (Panavia F, PF) following different curing methods and storage conditions. The specimens, which were either light-cured (LC) or chemical-cured (CC), were stored in either distilled water (DW) or demineralizing solution (DS; pH 4.5) for 1, 3, 7, 15, 30, 60, and 90 days. Fluoride ion release was measured using a fluoride ion-specific electrode. Data (n = 5) were statistically analyzed using one- and three-way ANOVA (p = 0.05). A "burst effect" was observed in the first week from both materials. However, fluoride ion release from FLC was seven times higher than that from PF. Storage in demineralizing solution accelerated the amount of fluoride release from both materials. In addition, LC yielded a lower amount of fluoride ion release from both materials, as compared to CC. It was concluded that both curing mode and storage medium influenced the amount of fluoride release from the tested materials.

Analysis of Variance↗

PubMed2006

Effect of resin coating on adhesion of composite crown restoration.

The purpose of this study was to evaluate the effect of a resin coating technique on the microtensile bond strength (microTBS) of resin cement to dentin in composite crown restorations. Crown preparations were done on human molars. A resin coating material, Hybrid Bond, was immediately applied to the prepared dentin and light-cured, while the tooth without resin coating acted as the control. An impression of the resin-coated tooth was taken, and a composite crown fabricated on the working cast. The composite crown was then bonded with a resin cement, Chemiace II. MicroTBSs were measured at a crosshead speed of 1 mm/min, and the resin-coated group yielded significantly higher microTBSs than the non-coated group (p < 0.05). In terms of microTBS values between the axial and occlusal surfaces, no regional differences in resin-dentin bond strength were detected (p < 0.05). It was concluded that resin coating with Hybrid Bond significantly improved the microTBS of resin cement to dentin in composite crown restorations.

Analysis of Variance↗

PubMed2006

Effects of smear layer and surface moisture on dentin bond strength of a waterless all-in-one adhesive.

The purpose of this study was to evaluate the microtensile bond strength (MTBS) of a waterless all-in-one adhesive system, Absolute, to dentin. Eighteen human molars were either ground with 600-grit SiC paper or cut with a diamond bur. The following dentin bonding procedures were then performed: dentin surface was kept moist; dentin surface was dried; or dentin surface was dried but equivalent amount of water was added to the adhesive (1:1 by volume). After adhesive curing, a resin composite was incrementally built up. After the specimens were kept in water for one day, MTBSs were measured at a cross-head speed of 1 mm/min. Two-way ANOVA (p = 0.05) indicated that the MTBS of the adhesive system was not influenced by surface texture, but enhanced by the presence of water on tooth surface. It was concluded that water is essential to obtaining good dentin bonding for this adhesive system.

Analysis of Variance↗

PubMed2006

Evaluation of antibacterial and fluoride-releasing adhesive system on dentin--microtensile bond strength and acid-base challenge.

This study evaluated the influence of a fluoride-containing adhesive on microtensile bond strength (microTBS) to dentin, as well as analyzed the dentin-adhesive interface after acid-base challenge. Experimental groups were: G1--Clearfil SE Bond control (SE); G2--Clearfil Protect Bond control (PB); G3--Primer[SE]/Adhesive[PB]; G4--Primer[PB]/Adhesive[SE]. For microTBS evaluation, dentin surfaces were ground, bonded, and composite resin crowns were built up to obtain beams to be tested. For interfacial analysis, adhesive system was applied on dentin surface and a low-viscosity resin was placed between two dentin disks. Then, the specimens were subjected to acid-base challenge, sectioned, and polished to be observed by SEM. microTBS data showed no statistical differences among the groups (GI: 51.3, G2: 47.6, G3: 55.0, G4: 53.9; mean in MPa). Through SEM, it was observed that a thick acid-base resistant zone adjacent to the hybrid layer was created only when the fluoride-releasing adhesive was used. In conclusion, the presence of fluoride in an adhesive contributed significantly to preventing secondary caries, and did not interfere with dentin-adhesive bond strength.

Adhesives↗

PubMed2006

Retrospective study of five-year clinical performance of direct composite restorations using a self-etching primer adhesive system.

This study was conducted to assess the five-year clinical performance of composite restorations using a self-etching primer adhesive system, Clearfil Liner Bond II. Restorations were rated using the following scale: A--Good; B--Clinically acceptable; C--Clinically unacceptable; or D--Already replaced. The ratings were analyzed using Freedman's test (p=0.01) and Steel-Dwass test (p=0.05). A total of 83 restorations from 36 patients were identified from treatment records. Twenty-six restorations (31.3%) presented A rating and 36 restorations (43.4%) were clinically acceptable (B rating), while five (6.0%) received C rating and 16 (19.3%) had already been replaced (D rating). The mean survival rate of serviceable restorations (i.e., combined A and B ratings) after five years was 74.7%. It was found that cavity form, including cavity size, and occlusal contact seemed to influence longevity.

Acid Etching, Dental↗

PubMed2006

Coronal leakage inhibition in endodontically treated teeth using resin-coating technique.

The purpose of this study was to evaluate coronal leakage inhibition using a resin-coating technique after endodontic treatment. Thirty-six human incisors were cut at the cementoenamel junction, and endodontic obturations were performed. The specimens were randomly divided into three groups according to post space preparation (10 mm depth), resin coating, and temporization. For the resin coating, the dentin surface was coated with either a combination of Clearfil SE Bond and Protect Liner F (SE/PLF) or RZII (RZ). Then, the specimens were stored in 37 degrees C distilled water for 24 hours and placed in 1% methylene blue solution for 48 hours. After which, the specimens were sectioned faciolingually along the root canal and the length of dye penetration was measured from the cementoenamel junction. Three-way ANOVA revealed that the dye penetration scores were influenced by post space preparation, resin coating, and temporization. Resin coating with RZ significantly reduced the dye penetration score and SE/PLF completely eliminated dye penetration.

Analysis of Variance↗

PubMed2005

Micro-shear bond strength and morphological analysis of a self-etching primer adhesive system to fluorosed enamel.

PURPOSE: The aim of this study was to evaluate micro-shear bond strength and morphological analysis of a self-etching primer adhesive system to fluorosed enamel. MATERIALS AND METHODS: Extracted human molars were classified according to the severity of fluorosis using Thylstrup and Fejerskov index into four groups (TFI: 0, normal; 1-3, mild fluorosis; 3-6, moderate fluorosis; 6-7, severe fluorosis) and divided into following two sub-groups. For the first sub-group, a self-etching primer adhesive system was applied to the ground enamel surfaces and the other sub-group was conditioned with 37% phosphoric acid for 30s prior to application of the same adhesive system. Teeth were then restored with a resin composite, stored for 24h in water and micro-shear bond strengths were measured. After shear testing, the fracture modes were observed under a laser scanning microscope. Morphological study of etching patterns and adhesive interface was done under a scanning electron microscope (SEM). The data were analyzed using two-way ANOVA and Sheffe test (p=0.05). RESULTS: No statistically significant difference was there between the different degrees of fluorosis in each sub-group. However, significant difference in the bond strengths between phosphoric acid etching and self-etching was found in moderate and severe groups. The SEM observations showed at the resin-enamel interface, thick resin tag like extensions penetrated around 3.5 microm into the enamel etched with phosphoric acid, while self-etching primer created, 1 microm lamina like penetration. CONCLUSION: Severity of fluorosis affects the micro-shear bond strength of a self-etching bonding system to fluorosed enamel.

Acid Etching, Dental↗

PubMed2005

Seven-year dentin bond strengths of a total- and self-etch system.

The aim of this study was to determine the durability of tensile bond strengths of a conventional 3-step bonding system (Superbond D-liner Plus) and a self-etching priming bonding system (Clearfil Liner Bond II) to bovine dentin over a 7 yr period. Superficial bovine dentin finished with 600-grit SiC paper was bonded with one of the two adhesive materials. A 4 mm diameter area was bonded, covered with resin composite and stored in 37 degrees C deionized water containing gypsum chips and 0.4% sodium azide as an antibacterial. Bonds were stressed in tension at a crosshead speed of 1 mm min(-1). Mean bond strengths were observed at 1 d, at 1, 3, and 6 months, and at 1, 2, 3, 6 and 7 yr. Ten specimens were tested for the first 3 yr and 15 specimens were tested for 6 and 7 yr. The bond strength of Superbond D-liner Plus significantly decreased over the 7 yr period, whereas Liner Bond II showed a slight but, insignificant, decrease. The fracture mode changed with time for Superbond D-liner Plus, but not for Liner Bond II. It was concluded that systems which use a strong acid for demineralizing the dentin may show greater deterioration of the bond to dentin compared with a self-etching priming system.

Acid Etching, Dental↗

PubMed2005

Shear bond strengths of indirect resin composites to hybrid ceramic.

A hybrid ceramic, Estenia, is a highly-filled composite for indrect use. The purpose of this study was to measure the shear bond strength between Estenia and six incremental materials: Estenia, Cesead II, Epricord, Gradia, Prossimo, and Solidex. Five specimens were prepared for each group, and all specimens were subjected to shear bond strength testing at a cross-head speed of 1 mm/min. Data were analyzed using two-way ANOVA and Dunnett's T3 test at 95% confidence level. The results indicated that the shear bond strength of Estenia to Estenia was significantly lower than that of any other combinations. Apart from storage condition that was found to influence shear bond strength statistically, thermal cycling of the specimens also tended to decrease the bond strength between Estenia and the incremental materials. It was concluded that regularly-filled composites are suitable to be used as an incremental material facing Estenia in combination technique.

Analysis of Variance↗

PubMed2005

Effect of air-powder polishing on dentin adhesion of a self-etching primer bonding system.

The purpose of this study was to evaluate the effect of air-powder polishing with sodium bicarbonate (SB) or crystalline cellulose (CC) on the bond strength of a self-etching primer bonding system to dentin. Ground human dentin surfaces were prepared using 600-grit SiC paper. The teeth were divided into three groups according to dentin treatment: control, air-powder polishing with SB, and air-powder polishing with CC. The dentin surfaces were bonded with a self-etching primer bonding system, followed by a light-cured resin composite. microTBS test and SEM analysis were performed. The results of microTBS test indicated that air-powder polishing with SB affected bond strength to dentin, while that with CC did not influence bond strength. SEM observation of air-polished dentin surfaces showed that dentin surfaces air-polished with SB were roughened and covered with a smear layer, while those with CC were smooth and the smear layer was removed.

Air Abrasion, Dental↗

PubMed2005

Influence of curing method and storage condition on microhardness of dual-cure resin cements.

This study evaluated the influence of curing method and storage condition on the microhardness of dual-cure resin cements: Panavia F 2.0 (PF) and Nexus 2 (NX). The specimens were either light-cured (LC) or chemically cured in darkness (CC). After 24 hours of storage in dry chamber (Dry) or distilled water (DW), the specimens were sectioned and polished. The microhardness of resin cement matrix was measured using a nanoindentation tester (ENT-1100). The data (n = 6) were statistically analyzed with t-test, two-way ANOVA (p < 0.05), and Tukey HSD test (alpha = .05). It was found that the factors of curing method and storage condition had significant effect on microhardness. For both PF and NX, LC presented higher microhardness than CC, while DW showed higher microhardness than Dry. In conclusion, dual-cure resin cements could achieve high degree of cure when light-cured. In addition, the microhardness of the resin cements evaluated did not decrease when kept in water.

Analysis of Variance↗

PubMed2005

Influence of cavity configuration on the adhesion of two resin-based composites to pulpal floor dentin.

PURPOSE: To evaluate the effect of cavity configuration on microtensile bond strengths of two resin composites for core build-up to pulpal floor dentin. METHODS: Access cavity preparation and root canal filling with gutta percha were performed on extracted human molars. Following this, the gutta percha in the pulp chamber was completely removed to expose pulpal floor dentin. The cavity walls remained as a control group (Cavity). For another group, the cavity walls were removed to create a flat surface for bonding (Flat). For the Cavity group, Clearfil SE Bond was applied to the cavity according to the manufacturer's instructions, and either a light-cured resin composite (PH, Clearfil Photo Core) or a dual-cured resin composite (DC, Clearfil DC Core), was placed in the bonded cavity. Clearfil Photo Core was placed in three increments while bulk-filling was used for Clearfil DC Core. The application of the bonding system and the composites to the flat dentin surface was the same as that for cavity. Specimens were stored in water for 1 week, then sectioned vertically into 2 or 3 slabs (0.7 mm thick) and trimmed for the microtensile bond strength (MTBS) test. The MTBSs were measured with a universal testing machine at a crosshead speed of 1.0 mm/minute. RESULTS: The results (mean +/- SD, MPa, n=10) of PH/Cavity, PH/Flat and DC/Flat were 21.9 +/- 3.4, 28.9 +/- 4.0, and 27.6 +/- 6.1 respectively. The MTBS could not be determined in DC/Cavity because of debonding occurred during sample preparation.

Analysis of Variance↗

PubMed2005

Confocal laser scanning microscopic observations of secondary caries inhibition around different types of luting cements.

PURPOSE: To analyze in vitro artificial secondary caries inhibition around conventional luting cements and resin cements using a confocal laser-scanning microscope (CLSM). METHODS: Box shape cavities (approximately 3 mm long, 4 mm wide, and 1.5 mm deep) were prepared in bovine root dentin. One of five cements: Elite Cement 100 (EL) zinc phosphate cement, HY-Bond Carbo Cement (CA) polycarboxylate cement, Fuji I (FI) glass-ionomer cement, Fuji Luting (FL) GIC-based resin cement and Panavia F (PA) fluoride-releasing resin cement, was placed in the cavity. After polishing, the center of the cement surface was covered with an adhesive to preserve the original cement solubility. The specimens were stored in distilled water at 37 degrees C for 1 week, and stored in an artificial demineralizing solution for 3.5 days. Following this, each specimen was sectioned into two halves, trimmed, and polished. Thickness of inhibition zone, depth of outer lesion and cement solubility around each cement were determined by a CLSM. RESULTS: Inhibition zones were not seen in EL and CA, while they were found in FI, FL and PA. The depths of the outer lesions of CA and FI were significantly lower than those of EL, FL and PA (P< 0.05). The highest and the second-highest cement solubility were obtained in EL and CA, respectively. FI and FL indicated significantly lower cement solubility than EL and CA. PA tended to show the lowest cement solubility.

Analysis of Variance↗

PubMed2004

Microhardness and Young's modulus of a bonding resin cured with different curing units.

This study evaluated the microhardness and Young's modulus of a photocurable bonding resin, Clearfil SE Bond (SE), cured with four curing units at different distances. The curing units used were: Candelux (Quartz-tungsten halogen), Lux-O-Max (Blue light emitting diode), Arc-light (Plasma-arc), and Rayblaze (Metal halide). Discs of bonding resin were prepared using vinyl molds and were photocured at the top surface with light tip at three different distances (contact, 2 and 4 mm). After 24 hours of storage in water at 37 degrees C, the specimens were sectioned into halves, embedded in epoxy resin, and polished. The microhardness and Young's modulus of this bonding resin were measured using a nanoindentation tester. Six specimens were prepared for each group. The data was statistically analyzed using two-way ANOVA test and Tukey multiple comparison test (p < 0.01). The microhardness of SE was affected by light source and distance, as was Young's modulus. Candelux and Rayblaze presented the highest hardness and Young's modulus results. Both properties presented high values when the curing unit tip was maintained in contact with the irradiated surface. Increasing the distance between the curing unit tip and the irradiated surface decreased the hardness and Young's modulus of SE.

Analysis of Variance↗

PubMed2004

Surface analysis of dentinal caries in primary teeth using a pH-imaging microscope.

The aim of this in vitro study was to evaluate the pH value of intact and carious dentin in primary teeth using a pH-imaging microscope (SCHEM-100, HORIBA Ltd., Kyoto, Japan). Bucco-lingual cut sections of extracted human primary teeth, which had either mild or severe dentinal caries lesions, were placed on the pH-imaging sensor of the microscope. The pH values were compared statistically by Levene's test for equality of variances and Tukey HSD multiple comparison test (p < 0.05). For both mild and severe lesions in primary dentin, the lowest pH values in the carious lesions were lower than those of intact dentin (6.6, range 6.3-6.9). There were statistical differences between the lowest pH value within the mild lesions (6.2, range 5.8-6.4) and that of the severe lesions (6.0, range 5.9-6.2) (p < 0.05). It was concluded that SCHEM-100 was able to distinguish the pH-value distribution of intact and carious dentin in primary teeth.

Analysis of Variance↗

PubMed2004

Ultrastructure of the dentin-adhesive interface after acid-base challenge.

PURPOSE: To observe the ultrastructure of the dentin-adhesive interface after in vitro sequential challenge by acidic and basic chemicals around adhesive restorations. MATERIALS AND METHODS: Box-shaped cavities were prepared in bovine root dentin and restored as follows: Reactmer Bond and Reactmer Paste (RB/RP), Clearfil SE Bond and Clearfil AP-X (SE/APX), ABF (experimental) and APX (ABF/APX), Single Bond and APX (SB/APX). After the specimens were stored in water for 1 week, the integrity of the bonds tested by sequential immersion were placed in an artificial demineralizing solution (pH 4.5) for 20 min and in 5% NaOCl for 20 min. The specimens were sectioned, polished, then argon-ion etched for 7 min, and gold sputter coated for SEM examination of the dentin-adhesive interface. RESULTS: The morphological results indicated tight bonding between the cavity wall dentin and the adhesive. For the fluoride-releasing restoration, RB/RP, a thick acid-resistant zone was clearly observed adjacent to the restoration; however, the bonding resin, RB, was partially degraded by the acid-base challenge. For SE/APX, ABF/APX and SB/APX, the bonding resins were resistant to the acid-base challenge. With the self-etching adhesive systems, SE and ABF, a thin band of acid-base resistant dentin less than 1 microm thick was observed beneath the hybrid layer. With the wet bonding system, SB, the hybrid layer was partially degraded by the acid-base challenge. CONCLUSION: SEM observation is useful for observing the reactions of adhesives to acid-base challenge. Prevention of secondary caries around a restoration may be influenced by the physical properties of the restorative and adhesive materials, quality of the hybrid layer, and fluoride-release.

Acetic Acid↗

PubMed2004

Effects of light intensity through resin inlays on the bond strength of dual-cured resin cement.

PURPOSE: To evaluate the influence of the light intensity, irradiation time, and thickness of the indirect restoration composite on the bond strength of dual-cured resin cement immediately after cementation, applying the resin coating technique. MATERIALS AND METHODS: Three hundred forty composite blocks as an adhesive surface and four thicknesses of indirect restoration composite disks were prepared. The surface of the composite blocks was coated with low-viscosity resin composite and immersed in water for 24 h. After immersion, dual-cured resin cement was applied to the resin-coated surface and the indirect restoration composite disks were placed on it. Light irradiation was performed through four thicknesses of indirect restoration composite disks with conventional halogen (40 s) and high intensity (10, 20, 40 s) light units. The specimens were stored in water at 37 degrees C for 10 min or 24 h, and the tensile bond test was performed. RESULTS: For the 1-mm composite thickness, there were no significant differences in the bond strengths between 10 min and 24 h after cementation with the four light curing methods. For the composite thicknesses of 3 or 4 mm, the bond strength 24 h after cementation was significantly higher than that at 10 min after cementation with conventional halogen (40 s) and high-intensity light units at 10 s and 20 s, but there was no significant difference with the high-intensity light unit applied for 40 s. CONCLUSION: The bond strength of dual-cured resin cement immediately after cementation could be greatly influenced by the irradiation time and the light intensity penetrating the indirect restoration composite.

Analysis of Variance↗

PubMed2004

Influence of activation mode of dual-cured resin composite cores and low-viscosity composite liners on bond strength to dentin treated with self-etching adhesives.

PURPOSE: The objective of this study was to investigate the effect of light- or chemical initiation on the polymerization reaction of dual-cured composite core buildup materials (CM) with respect to their shear bond strength to dentin treated with self-etching adhesives (SE), in the presence or absence of a low-viscosity composite liner (LI). MATERIALS AND METHODS: Two SEs (Clearfil SE Bond and Unifil Core Bond), their respective CMs (DC Core Paste and Unifil Core), and a LI (Protect Liner F) were tested. After removing the labial enamel surfaces of 8 bovine incisors, each flat dentin surface was sectioned into 4 pieces with similar surface areas (30 mm2). The dentin surfaces were wet abraded with 600-grit SiC paper and randomly divided into 8 groups. Experimental groups comprised the use of a SE and its respective CM with or without an intermediate application of the LI and with or without CM light activation. Three cylinders of CM (0.5 mm high and 0.75 mm in diameter) were applied to each bonded dentin surface (n = 12), using a tygon tubing mold. After water storage for 24 h, specimens were subjected to microshear testing. Data were statistically analyzed by two-way ANOVA and Tukey's test (5%). RESULTS: For both SEs, LI application and CM light activation showed significantly higher bond strengths than the groups in which an intermediate LI was not used or the CMs were only chemically cured. CONCLUSION: The bond strength of CM to dentin using SE is reduced if the LI and light activation are not employed.

Acrylic Resins↗