Recently, the resin bonding system has been simplified to shorten the clinical procedures. The one-bottle/onestep type resin bonding agent “Bond Force^TR” was developed by Tokuyama Dental Corp. The aim of this study was to examine the interfacial ul^TRas^TRucture of Bond Force^TR under SEM and TEM, and the tensile bond s^TRength (TBS) to bovine teeth and μTBS to human teeth were determined and compared with Clearfil Mega Bond as a con^TRol. For SEM observation of the bonding interfaces, human enamel, intact dentin (ID), and caries-affected dentin (CAD) were used, and for TEM observation, human intact dentin was used. A human ex^TRacted molar was longitudinally cut, and the surface of the enamel and ID was created with #1, 000 SiC paper. CAD was exposed with a steel-round bur according to staining difference by a caries detector. SEM observation showed no gap formation between Bond Force^TR and enamel/ID/CAD. The resin-dentin hybrid layer was hardly observed at the interface. An interfacial s^TRucture of200-300nm width was found at the superficial layer of dentin under TEM, suggesting that a nano-level bonding mechanism had been created. The means of TBS (SD) were21.9 (3.6) MPa to enamel and 23.3 (2.5) MPa to dentin, and the mean of μTBS was50.0 (9.8) MPa to human dentin showing no statistical difference from Clearfil Mega Bond (49.4 (10.0) MPa)(p>0.05). This resin bonding agent showed satisfactory adhesion to the tooth tissue, and was thought to be promising for clinical use.

View full abstract

The purpose of this study was to evaluate the mechanical properties of an experimental PMMA resin cement PRC-01 (PRC). Film thickness, flexural strength and tensile bond strength to both enamel and dentin were compared with three commercially available resin cements: Multibond (MB), Super-Bond C&B (SB), and Super-Bond Quick (SBQ). Film thickness and flexural strength (three-point bending test) were measured according to ISO 4049. In addition, the film thickness affected by working time was measured after0, 1, 2and3minutes. The tensile bond strength to both enamel and dentin substrate of bovine teeth were measured after5minutes, 10minutes and 24hours respectively. The results were as follows. The film thickness of all cements met the ISO4049standard. Only PRC showed no increase in film thickness after3minutes. MB showed the lowest value in the modules in bending, while the other three cements showed no statistically significant difference. SBQ showed the lowest value in the modules in bending, while the other three cements showed no statistically significant difference. PRC showed high tensile bond strength to both enamel and dentin after5minutes, which was similar to that of MB. All cements showed no statistically significant difference in the tensile bond strength after24hours. The results indicate that PRC has good mechanical properties.

View full abstract

The purpose of this study was to examine the effect of Er: YAG laser irradiation on the bonding reliability of cervical resin composite restorations. The efficiency of an antibacterial self-etching primer adhesive system was also investigated. Standardized V-shaped cavities were prepared finally with an Er: YAG laser unit (L) or a rotary cutting unit (R); 20cavities by each were prepared in the cervical region of extracted human lower premolars. The cavities were restored with two types of self-etching primer adhesive systems, an antibacterial system, Clearfil Mega Bond FA (F, Kuraray Medical), and a conventional system, Clearfil Mega Bond (M, Kuraray Medical), and with a resin composite, according to the manufacturer's instructions. Four types of restored specimen, 10each, were subjected to a combination stress load test simulating an intra-oral environment. The micro-tensile bond strength (μ-TBS) to the gingival dentin wall of the specimens after the combination stress load was measured. The data were examined using ANOVA and Weibull analysis. The μ-TBS (SD) of LF/RF/LM/RM restorations were7.0 (4.6)/12.4 (4.8)/9.0 (4.9)/15.4 (6.1) MPa. The μ-TBS of L restorations was significantly smaller than that of R restorations at p<0.01, regardless of the system. There was a significant difference in Weibull modulus between L and R restorations at p<0.01, regardless of the system, and the bonding reliability of L restorations was statistically inferior to that of R restorations. There was no significant difference in Weibull modulus between F and M restorations, regardless of the unit used for final cavity preparation, and similar bonding reliability was recognized in both restorations.

View full abstract

The adhesion of an experimental one-bottle one-step resin bonding agent (SI-R20603) to tooth structures was evaluated by SEM and TEM. For SEM observation, human extracted molars were used. After carious dentin was removed, the crown was horizontally cut to expose caries-affected dentin (CAD). The surface ground with # 1, 000 SiC paper was treated with SI-R20603 and filled with a resin composite. The specimen was cut into halves and embedded. After the cut surface was polished, argon-ion beam etched and Pt-sputtered, the bonding interface with enamel, intact dentin and CAD was observed by SEM. For TEM observation, intact dentin of human extracted molars was used. The bonding specimen created as above was ultra-thinned without demineralization. In SEM figures, the bonding agent created a rigid junction with enamel, intact dentin and CAD. TEM figures revealed tight adhesion to intact dentin. Although both in SEM and TEM no hybrid layer was observed at the bonding interface with dentin, an intermediate zone of approximately 0.5μm thick was found between the superficial dentin surface and the bonding agent. The results indicated that the adhesion of the experimental bonding agent is promising.

View full abstract

The purpose of this study was to investigate the bonding performance of a one-step adhesive to human cementum and compare the result with that of the two-step adhesive. Two commercially available adhesives were investigated: a one-step adhesive (Clearfil Tri-S Bond), and a two-step self-etch adhesive (Clearfil Mega Bond). The cementum and dentin regions were chosen from the mesial and distal surfaces of extracted human molars and bonded with each adhesive. Small cylinders of resin composite, approximately0.7mm in diameter and0.5mm in height, were bonded to the surface and a micro-shear bond test was performed to evaluate the bond strength. The shear bond test results showed significantly lower bonding of both of the adhesives when they were applied to the cementum (p<0.05). The two-step adhesive showed higher bonding values than the one-step adhesive (p<0.05).

View full abstract

The purpose of this study was to determine the effect of opaque shades on the color of layered resin composite restorations. The materials used were opaque-A2 and Body-A2shades from Filtek^TM Supreme (3M ESPE)(FS) and Gradia Direct (GC)(GD). L*, a*, and b* of the layered resin composites (1mm of body shade on 2mm opaque shade or1mm of body shade on 2mm body shade) were evaluated using a colorimeter on a black backing. When the opaque shades were used, L* and b* of FS and a* and b* of GD showed higher values compared with not using opaque shades. Therefore, usage of the opaque shades could be beneficial to obtain higher brightness and chroma in the layering technique of composite resin restorations.

View full abstract

In this study, the effect of the roughness of porcelain surface on the bond durability of resin to the silanated porcelain surface was examined, since the manufacturer recommends grinding the fractured porcelain surface by a diamond point to roughen the porcelain surface before repairing fractured porcelain using resin composite. Furthermore, the effects of the silanating period of the roughened porcelain surface and the application of bonding agent on the bond durability were studied.
The bond durability of the resin to the silanated porcelain surface differed between porcelain surfaces prepared by grinding with #100and #1, 000. The roughness of the porcelain surface affected the bond durability of resin composite. This result clearly suggests that grinding of the fractured porcelain surface by a diamond point provides noticeably higher bond durability than that by the # 100grinding.
On the other hand, the extension of the silanating period from10seconds from 60 minutes increased the bond durability. However, the obtained bond durability was the same as that obtained when the resin composite was directly applied to the silanated porcelain surface without any application of bonding agent. The application of bonding agent to the silanated porcelain surface did not improve the bond durability.

View full abstract

Recently, various all-in-one adhesive systems have been developed. Reducing the steps of the adhesive procedure makes it possible to shorten the application time. On the other hand, recent clinical studies showed that the simplified systems may restrict the efficacy of bonding. Moreover, most of the all-in-one systems were reported to produce lower bond strength compared to2-or3-step adhesives in vitro. The purpose of this study was to evaluate all-in-one adhesives by assessing their microtensile bond strength.
Enamel and dentin slices were prepared by grinding occlusal surfaces of extracted human molars and polishing with600-grit silicon carbide paper under running water. Three commercially available all-in-one adhesives, Clearfil Tri-S Bond, OptiBond All · In · One, Tokuyama Bond Force and2-step self-adhesive Clearfil Mega Bond were used. After the bonding procedure, resin composites were incrementally built up on flat enamel and dentin surfaces. After storage in 37°C water for 24 hours, they were sectioned into beams (cross-sectional area1mm²) for the bond strength measurement and tested at a crosshead speed of1mm/min. The data were analyzed by Kruskal-Wallis and Games-Howell tests. The results showed that the bond strength of Clearfil Mega Bond was significantly higher than that of Bond Force in enamel. However there was no significant difference between allin-one bonding systems. For dentin, Bond Force showed significantly higher bond strength than Tri-S Bond. The results of this study showed that the two-step self-etching adhesives do not always produce greater bond strengths than that of the all-in-one systems.

View full abstract