Biomedical subjects

Toru Nikaido

Publications and source records attributed to Toru Nikaido.

32 records · Page 2Linked to original sources

PubMed2003

Effect of artificial saliva contamination on pH value change and dentin bond strength.

OBJECTIVE: This study was to examine the effect of artificial saliva contamination on pH change of the dentin surface and the micro-shear bond strength (MSBS) of the two bonding systems to contaminated dentin. METHODS: Fifty-six human dentin disks were tested with two resin bonding systems: a self-etching primer system, Clearfil SE Bond (Kuraray Medical Inc., Tokyo, Japan), and a one-bottle adhesive system, Single Bond (3M-ESPE, St. Paul, MN). Dentin surfaces were conditioned with the self-etching primer (primer) or phosphoric acid (etchant) and divided into four groups: conditioning without contamination (conditioning), contamination with artificial saliva (contamination), re-conditioning the contaminated dentin (re-conditioning), water-rinsing the contaminated dentin and re-conditioning (rinsing and re-conditioning). The pH change on the dentin surface was measured using a pH-imaging microscope (SCHEM-100, Horiba Ltd, Kyoto, Japan) to estimate the acid-base characteristics of the conditioned and contaminated dentin surface. The MSBS to the dentin was examined after storage in distilled water at 37 degrees C for 1 week. RESULTS: The pH of intact dentin surfaces was 6.9. Conditioning with the primer and etchant decreased the pH to 5.4 and 5.9, respectively. Saliva contamination increased the pH slightly, and re-conditioning decreased the pH again. The MSBS of the two bonding systems decreased after contamination. Re-priming restored the MSBS to control values, while re-etching did not. Rinsing and re-priming produced a reduction in MSBS, and rinsing and re-etching did not increase the MSBS. SIGNIFICANCE: The conditioning and saliva contamination changed the pH value of dentin surface. The MSBS decreased after contamination; however, re-priming with SE Bond primer was an adequate treatment to restore the bond strength.

Acid Etching, Dental↗

PubMed2003

Efficacy of a resin coating on bond strengths of resin cement to dentin.

PURPOSE: The aims of this study were to (1) evaluate the effect of a resin coating consisting of a dentin bonding system and a flowable resin composite on the microtensile bond strength (micro-TBS) of a resin cement to dentin in indirect composite restorations and (2) compare the bond strengths of direct and indirect composite restorations. MATERIALS AND METHOD: Occlusal surfaces of human premolars were ground to obtain flat dentin surfaces and were divided into seven groups. For indirect restorations, the dentin surfaces of the experimental groups were bonded with a dentin bonding system (DBS), Clearfil SE Bond (SE) or Single Bond (SB) with and without a flowable resin composite, Protect Liner F (PLF), temporized for one day and cemented with a resin cement (Panavia F) according to the manufacturer's instructions. The dentin surfaces of the control group were temporized without prior treatment, and indirect composite (Estenia) was bonded with Panavia F. For the direct restorations, either SE or SB was applied to the dentin surface and the entire surface was built up with direct composite (Clearfil AP-X). After 24 hours in water storage, micro-TBS was measured at a crosshead speed of 1 mm/min. The data were analyzed with one-way analysis of variance and Fisher's protected least significant difference test (p < .05). RESULTS: The original bond strength of the resin cement (Panavia F) to dentin significantly improved with the use of a resin coating technique in indirect restorations (p < .05). The combination of DBS + PLF showed significantly higher bond strengths compared with the single use of DBS. The combination of SE + PLF as a resin coating provided the highest bond strengths in indirect restorations (p < .05). However, the best bond strengths were observed when SE and SB were used for direct composite restorations (p < .05). CONCLUSIONS: The application of a resin coating consisting of a dentin bonding system and a flowable resin composite on the dentin following cavity preparation significantly improved the micro-TBS of the resin cement Panavia F to dentin in indirect restorations. However, the bond strengths of indirect composite restorations were significantly lower than those of direct composite restorations even with the resin coating technique. CLINICAL SIGNIFICANCE: Indirect composite restorations may require a resin coating to improve the bonding performance of the resin cement Panavia F to dentin. However, adhesive systems with direct composite restorations still provide superior bond strengths compared with indirect restorations.

Analysis of Variance↗

PubMed2003

Evaluation of in vitro secondary caries using confocal laser scanning microscope and X-ray analytical microscope.

PURPOSE: To evaluate in vitro secondary caries formation and inhibition by using a confocal laser scanning microscope (CLSM), and further map the calcium distribution with an X-ray analytical microscope (XAM). MATERIALS AND METHODS: 36 box-shaped cavities were prepared on bovine root dentin and restored with Fuji II, Fuji II LC (improved), or Clearfil Liner Bond 2V system with a non-fluoride releasing resin-based composite; Clearfil AP-X was used as a negative control. After immersion in a buffered demineralizing solution of 50 mmol/L of acetic acid adjusted to pH 4.5 for 3.5 days, longitudinal half sections were cut through each restoration and polished for analysis under CLSM. In order to confirm the CLSM results, the same samples were subsequently examined by means of the X-ray analytical microscope (XAM). The values of the outer lesions and the inhibition zones obtained by the two different CLSM and XAM measurements were then analyzed by one-way ANOVA, Fisher's PLSD Test at the 95% level of confidence and correlation coefficient. RESULTS: Inhibition zones and outer lesions were clearly detected under CLSM around the glass-ionomer and resin-modified glass-ionomer restorations. As expected, an inhibition zone was not detected adjacent to the resin-based composite restoration. Additionally, using the transmission x-ray images of XAM, the inhibition zones were observed as high density areas, and the outer lesions as low density areas. The width of the inhibition zones and the depth of the outer lesions measured under the CLSM were similar to those obtained from the XAM.

Acetates↗

PubMed2003

Tensile bond strengths of resin cements to bovine dentin using resin coating.

PURPOSE: To evaluate the effect of a resin coating technique on dentin tensile bond strengths of dual-cured resin cements. METHODS: 10 bovine dentin specimens were tested for tensile bond strengths of each of the following four materials: Panavia F, Link Max, Bistite II, Rely-X. Bovine dentin ground with 600-grit SiC was bonded with a resin cement according to the manufacturers' instructions or the resin coating technique, which was used in combination with one coat of a dentin adhesive; Clearfil SE Bond, Unifil Bond, One-Up Bond F or Single Bond, with one coat of a low viscosity micro-filled resin, Protect Liner-F. Each dentin adhesive and the low viscosity micro-filled resin were cured for 10 seconds and 20 seconds respectively. After 1 day storage in water, the specimens were subjected to the tensile bond test at a crosshead speed of 2 mm/minute. The data were analyzed by two-way ANOVA and Fisher's PLSD test (P < 0.05). The mode of failure after the tensile bond test was classified by visual inspection. The resin cement - dentin interfaces were examined by SEM. RESULTS: The tensile bond strengths (MPa +/- SD) of four resin cements to dentin with/without resin coating were: Panavia F (22.9 +/- 3.1; 10.2 +/- 2.5), Link Max (16.1 +/- 4.4; 9.6 +/- 3.2), Bistite II (14.8 +/- 3.2; 14.3 +/- 3.9), and Rely-X (15.7 +/- 4.7; 13.5 +/- 4.5), respectively. The resin coating significantly improved the bond strengths of resin cements to dentin in Panavia F and Link Max, while there were no significant differences of mean bond strengths between Bistite II or Rely-X with and without resin coating (P> 0.05). Regarding the fracture modes, complete and partial adhesive failures were observed in the cases without resin coating. For the resin coating groups, the fracture modes were much more complicated, although, adhesive failures rarely occurred. Hybrid layer formation was observed for all materials used.

Analysis of Variance↗

PubMed2003

Micro-shear bond strengths of adhesive resins to coronal dentin versus the floor of the pulp chamber.

PURPOSE: To evaluate the micro-shear bond strengths to superficial coronal dentin and the floor of the pulp chamber using two dentin bonding systems and to compare the ultrastructure of the resin-dentin interface of the two regions. METHODS: 30 non-carious molars were used to obtain 2 mm thick slabs of coronal dentin and dentin at the pulp chamber. The specimens in each region were divided into three sub-groups to be bonded as follows; Clearfil SE Bond was used according to the manufacturer's instructions, Single Bond was applied to either wet dentin (Blot dry Group) or air-dried dentin (Dry Group) after phosphoric acid etching. A resin composite cylinder 0.5 mm high and 0.75 mm in diameter formed using a vinyl tube was bonded to the dentin. Specimens were stored at 37 degrees C for 24 hours in water and then stressed in shear at a crosshead speed of 1 mm/minute. The data were analyzed with one-way ANOVA and Fisher's PLSD test at the 5% level of significance. In addition, the ultrastructure of cross-sectioned dentin surfaces, the conditioned dentin surface and the resin dentin interfaces were observed by SEM. RESULTS: The bond strengths of Clearfil SE Bond and the Single Bond Blot dry group were approximately 40 MPa in coronal dentin and 30 MPa in the dentin at the floor of the pulp chamber respectively. However, the bond strengths of Single Bond were significantly lower in the Dry condition (MPa) (P < 0.05). SEM observations revealed the thickness of the hybrid layer created by Clearfil SE Bond in coronal dentin and at the floor of the pulp chamber were less than 1.0 microm thick. For Single Bond, a 3-4 microm hybrid layer was created in coronal dentin, while a thinner hybrid layer was observed in the floor of the pulp chamber. Morphological and structural variations in dentin may have influenced the bond strengths of the bonding systems to the floor of the pulp chamber.

Acid Etching, Dental↗

PubMed2003

The resin-coating technique. Effect of a single-step bonding system on dentin bond strengths.

PURPOSE: An experimental single-step bonding system, RZ-II, has been developed as a resin coating material for crown preparation. The purpose of this study was to compare the dentin microtensile bond strengths (MTBSs) of RZ-II in direct and indirect use. MATERIALS AND METHODS: Human molar dentin was used. The specimens were divided into three groups of n = 20 each. Group 1: RZ-II was applied to the dentin surface once or twice, and built up with a direct composite. Group 2: The dentin surface was provisionally covered and stored in water for 1 day. The provisional material was removed and an indirect composite was then bonded to the dentin surface. Group 3: RZ-II was applied to the dentin surface once or twice for "resin coating" before the placement and removal of provisional material. An indirect composite was then bonded to the coated dentin. After 1 day, MTBSs were measured at a crosshead speed of 1 mm/min. The data were analyzed using one-way ANOVA and Fisher's PLSD test (p < 0.05). The interface between the indirect composite and resin-coated dentin was also observed using a SEM. RESULTS: The MTBSs of RZ-II in Groups 1 and 3 were significantly higher than those of Group 2 (p < 0.05). The thickness of the resin-coating layer and the hybrid layer were 5 to 6 microm and less than 1 microm, respectively. CONCLUSION: The single-step bonding system, RZ-II, could be useful as a resin coating material for crown preparation.

Adhesiveness↗

PubMed2002

Effect of resin-coating technique on dentin tensile bond strengths over 3 years.

PURPOSE: The resin-coating technique has been developed to protect prepared dentin and underlying pulp tissue. The purpose of this study was to evaluate the resin-coated dentin bond durability over a period of 3 years of a resin cement and to compare it with two representative resin cements. MATERIALS AND METHODS: Ten bovine dentin specimens were tested for tensile bond strengths with each of the following three materials: CLAPEARL DC with a resin-coating technique (CDRC), Panavia 21 (PA21), and Super Bond C&B (SBCB) at 1 day, 6 months, 1 year, and 3 years. Mean bond strengths were compared statistically by two-way analysis of variance and Fisher's PLSD test (p < .05). The mode of failure was classified by scanning electron microscope observation and analyzed using the Mann-Whitney U-test. RESULTS: The 3-year bond strengths of all resin cements were significantly lower than those at the other experimental periods except for 1 year (p < .05). There was no significant difference in mean bond strength between CDRC and SBCB (p > .05). Regarding the fracture modes, in the case of CDRC, an increase in adhesive failure at the resin-dentin interface was observed as the time period lengthened. Statistical differences were observed between SBCB and the other materials at 1 year (p < .05) and between PA21 and the other materials at 3 years (p < .05). CLINICAL SIGNIFICANCE: The mean tensile bond strengths of the three resin cements to dentin decreased at different rates during the study; the rate at which the bond decreases is likely to affect the long-term durability of restorations.

Acid Etching, Dental↗

PubMed2002

The in vitro dentin bond strengths of two adhesive systems in class I cavities of human molars.

PURPOSE: The purpose of this study was to evaluate the in vitro dentin bond strengths of two dentin bonding systems in Class I cavities following fatigue load cycling (FLC) with thermal cycling (TC). MATERIALS AND METHODS: Class I cavities were prepared in 12 human molars and restored with either Clearfil SE Bond (SE) and Clearfil AP-X resin composite (AP-X) or Single Bond (SB)/AP-X according to the manufacturers' instructions. After water storage for 1 week, untreated controls and test samples were subjected to 50,000 FLC with TC from 5 degrees C to 55 degrees C for 625 cycles and stored in water for 1 week. Microtensile bond strength (MTBS) tests were measured on the floor of the cavities at a crosshead speed of 1 mm/min. Data were statistically analyzed using one- and two-way ANOVA and Fisher's PLSD test at a 5% level of significance. RESULTS: The MPa results were: SE 30.5+/-12.8 (control) and 23.2+/-10.8 (50,000 FLC); SB 5.1+/-9.2 (control) and 4.7+/-5.7 (50,000 FLC). Bond strengths were not statistically significantly affected by FLC (p > 0.05); however, they were influenced by the bonding system (p < 0.05). The MTBS of SE was significantly higher than that of SB (p < 0.05) under FLC and TC test conditions. Over half of the SB specimens debonded during sample preparation, showing blister-like structures, suggesting that an over-wet phenomenon occurred on the cavity floor. CONCLUSION: SE produced excellent dentin bonds that were much stronger than those produced by SB, which was shown to be a technique-sensitive bonding system.

Acid Etching, Dental↗

PubMed2002

Enhanced bond strengths of compomers using two dentin bonding systems.

PURPOSE: To measure bond strengths of three commercial compomers using recent dentin bonding systems, and to observe the micromorphology of the cross-sectional interface of the bonded specimens. MATERIALS AND METHODS: One hundred and ten bovine teeth stored frozen were used. The dentin surfaces were ground flat with #600-grit silicon carbide paper, and divided into three groups for bonding: original bonding system group (Xeno Bond/Xeno, Prime&Bond 2.1/Dyract AP, and F2000 Primer/Adhesive/F2000 compomer), Clearfil Liner Bond 2V group (LB 2V/Xeno, LB2V/Dyract AP, LB2V/F2000 compomer, LB2V/AP-X), and Single Bond group (SB/Xeno, SB/Dyract AP, F2000 compomer, SB/Z100). After the bonding procedures had been performed, the bonded assemblies were stored in water for 24 hours at 37 degrees C. Then, tensile bond strengths were measured using a universal testing machine at a crosshead speed of 2 mm/minute. All data were statistically analyzed using one-way ANOVA and Fisher's PLSD at 95% of confidence. Specimens for SEM observations were bonded in the same manner as for the tensile bond test, cut in half, and embedded in epoxy resin. These were then polished to high gloss, gold sputter-coated, and observed with the SEM. RESULTS: Compomers bonded to dentin with recent dentin bonding systems showed significantly higher bond strengths than those with the original bonding systems (P< 0.05). Tensile bond strength of Clearfil Liner Bond 2V was also significantly higher than that of Single Bond (P< 0.05). SEM observations showed good interaction between the compomers, adhesive systems, and dentin with any restorative material used. For Xeno Bond/Xeno, Prime & Bond 2.1/Dyract AP, and Primer/Adhesive/F2000 compomer, the thicknesses of the hybrid layer were approximately 0.8-1.1 microm, 0.3-0.5 microm, and 0.7-1.5 microm respectively. On the other hand, the hybrid layer produced by LB2V was approximately 0.5 to 1.0 microm, whereas for SB was approximately 3.1 to 4.1 microm thick. The thickness of the hybrid layers created in each bonded sample depended on the adhesive material used.

Analysis of Variance↗

PubMed2002

Shear bond strengths to coronal and pulp chamber floor dentin.

PURPOSE: To evaluate the bond strengths of two different types of resin bonding systems to coronal dentin and dentin of the pulp chamber floor. MATERIALS AND METHODS: 20 extracted human molars were sectioned into three regions; superficial coronal dentin, deep coronal dentin and floor of pulp chamber dentin. The dentin surface of each region was bonded with Single Bond or Clearfil Liner Bond 2V. A core build-up light-cured resin composite, Clearfil Photocore, was placed and light-cured for 40 seconds. After storage in 37 degrees C water for 24 hours, shear bond strengths were measured using a single plane shear test assembly at a crosshead speed of 2.0 mm/minute. Morphological changes of the conditioned dentin and hybrid layer formation were observed by SEM. RESULTS: For Single Bond, the bond strengths to superficial dentin were within anticipated bounds (23 MPa), whereas the bond strengths to deep dentin (15 MPa) and floor of pulp chamber dentin (13 MPa) were significantly lower (P < 0.05). For Clearfil Liner Bond 2V, higher bond strengths (approximately 30 MPa) were obtained for each region. The data were analyzed by one- and two-way ANOVA, and Fisher's PLSD (P < 0.05). The appearance of the conditioned dentin varied according to dentin region and conditioner. For Single Bond, thick hybrid layers (3-4 microm) were observed, while thin hybrid layers (less than 0.5 microm) were observed in Clearfil Liner Bond 2V for all regions.

Analysis of Variance↗

PubMedDate not supplied

Morphological and mechanical characterization of the acid-base resistant zone at the adhesive-dentin interface of intact and caries-affected dentin.

This study examined the ultrastructure of both intact and caries affected dentin-adhesive interface after artificial secondary caries formation, using scanning electron microscopy and nanoindentation testing. Half of the prepared specimens were bonded with Clearfil SE Bond (Kuraray Medical, Japan) and a resin composite (Metafil Flo, Sun Medical, Japan) for the nanoindentation test. The other specimens were stored in a buffered demineralizing solution for 90 minutes, then observed using SEM. An acid-base resistant zone (ABRZ) was observed beneath the hybrid layer, distinguished by argon-ion etching. The ABRZ of caries-affected dentin was thicker than that of normal dentin, while its nanohardess was lower than normal dentin (p<0.05). It is suggested that the monomer of Clearfil SE Bond penetrated deeper than previously reported, creating a so-called "hybrid layer." However, its physical properties depended on the condition of the dentin.

Acids↗

PubMedDate not supplied

Effect of residual water on dentin bond strength and hybridization of a one-bottle adhesive system.

This research investigated the effects of wet and dry conditions of phosphoric acid etched dentin on resin bonding and determined the optimum moisture condition for resin bonding using an ethanol-based one-bottle adhesive system. Bovine dentin surfaces were etched with 35% phosphoric acid and rinsed with water. Under four wet and dry conditions (overwet, blot dry, one-second dry and desiccated), resin composite was bonded using Single Bond. Tensile bond strength was measured and the results analyzed by one-way ANOVA and Fisher's PLSD test at the 5% level. The resin-dentin interfaces of bonded specimens were observed with SEM. The bond strength of overwet, blot dry, one-second dry and desiccated groups were 5.2 MPa, 12.6 MPa, 11.9 MPa and 4.4 Mpa, respectively. The blot dry group and one-second dry groups revealed significantly higher bond strengths than the desiccated and overwet groups (p < 0.05). The formation of hybrid layers approximately 5 microm thick (overwet and blot dry), 2 microm (one-second dry) and 3 microm (desiccated) were observed. The coefficient of variation in the blot dry group was very high, even though a higher mean was observed. In the one-second dry group, the moisture content of the collagen network was possibly too low, such that hybrid layer formation was not as good even though the bond strength was high.

Acid Etching, Dental↗

PubMedDate not supplied

The effect of a "resin coating" on the interfacial adaptation of composite inlays.

The relatively low bond strengths of resin cements to dentin may result in poor interfacial adaptation of composite inlays. This study determined whether the interfacial adaptation of composite inlays could be improved by applying an adhesive system and a low viscosity microfilled resin to the prepared cavity walls before making an impression. Ten MOD cavities were prepared on extracted human premolars with gingival margins located above and below the cemento-enamel junction. A "resin coat" consisting of a self-etching primer system (Clearfil SE Bond) and a low viscosity microfilled resin (Protect Liner F) was applied to the cavities of half of the prepared teeth, while the remaining teeth served as non-coated control specimens. All the teeth were restored with composite inlays (Estenia) fabricated by the indirect method and cemented with a dual-cured resin cement (Panavia F). After finishing the margins with superfine burs, the bonded inlays were thermocycled between 4 degrees C and 55 degrees C for 400 cycles. Specimens were sectioned with a diamond saw and the tooth-restoration interfaces were observed with a confocal laser scanning microscope. The data were analyzed with two-way ANOVA and Fisher's PLSD test (p < 0.05). The percentage length of gap formation at the dentin-restoration interface of the "resin coated" teeth (7.1 +/- 3.5) was significantly less than that of the non-coated teeth (85.7 +/- 6.7) (p < 0.05). The concept of coating the prepared cavity with an adhesive system and a low viscosity microfilled resin resulted in observing fewer gaps at the internal dentin-restoration interface compared with the non-coated specimens.

Analysis of Variance↗

PubMedDate not supplied

Evaluation of active and arrested carious dentin using a pH-imaging microscope and an X-ray analytical microscope.

A pH-imaging microscope was tested on carious teeth to examine the acid-base characteristics of active and arrested carious dentinal lesions and compared with an assessment of mineral loss in carious affected lesions using an x-ray analytical microscope. Extracted human molars, 22 active and 83 arrested carious teeth, were sliced vertically to maximize the presence of visible carious lesions. The pH change on the dentin surface was measured with a pH-imaging microscope, and the mineral loss was measured with an x-ray analytical microscope. The pH value of intact dentin and active and arrested carious dentinal lesions showed 7.0 (n=105), 5.8 (n=22) and 6.6 (n=83), respectively (analyzed by Kruskal-Wallis). The mineral loss was distinguishable in active dentinal lesions (4.92 times as much as intact dentin), while arrested lesions showed a slight mineral loss (2.19 times as much as intact dentin). The changes in pH value and mineral loss were significantly correlated (Pearson's correlation coefficients r=-0.8024) in active carious dentin lesions and weakly correlated (r=-0.1480) in arrested carious dentin lesions. Changes in tooth substance with the progression of the active carious process were reflected in a reduction in pH value and an increase in the amount of mineral loss.

Adolescent↗