The purpose of this investigation is to examine the bonded interface restored to adultdog teeth with resin-composite by scanning electron microscope (SEM). The Class V cavities prepared were acid conditioned with 40% phosphoric acid gel (K-etchant; Kuraray), applied adhesive primer (Clearfil Photo Bond; Kuraray) and restored with a resincomposite (Clearfil Photo Posterior; Kuraray). After seven days (short-term) and 90 days (long-term), these teeth were extracted, and observed the bonded interface with SEM. As the result, the junction was very tight between the enamel and resin-composite in both short- and long-term period. The junction between the dentin and resin-composite was also tight in the short-term period. In the long-term specimen, on the other hand, exfoliation was partially observed in the region along the dentinal wall, and bacterial cells were detected in the exfoliated gap area. However, high-magnification SEM view of that area showed that the hybridized dentin continues to seal the underlying mineralized dentin. These results suggested that the hybrid layer dose not permit invasion of stimuli such as microorganisms and their products to the pulp, which were histologically intact. Thus, we concluded that the hybridized dentin functioned as barrier of dentin/pulp complex from external stimuli like enamel.

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One of the most important mechanisms of dentin bonding is believed to be based on the creation of a resin-dentin interdiffusion (hybrid) layer. The purpose of this study was to analyze the resin-dentin interdiffusion zone by means of micro laser Raman spectroscopy. Caries affected human dentin was obtained using the combined criteria of visual inspection and staining with a caries detector solution. Resin composites were bonded to dentin with the two-step bonding systems, and specimens were sectioned parallel to dentinal tubules and then polished. Raman spectra were successively recorded along a line perpendicular to the dentin-adhesive interface in steps of 0.2μm.
The representative Raman bands scanned across the resin-dentin interface showed transitional changes in the hydroxyapatite and resin components, indicating that the minerals removed by the self-etching primer or phosphoric acid were gradually replaced by resin. Evidences of poor saturation of the adhesive resin in the caries affected dentin, and the resin saturation of the partially demineralized dentin in the sound dentin were detected.

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We used the argon ion beam etching method to recognize the resin impregnated hybrid layer. But we had not been able to find out the target of the argon ion and the mechanism of this etching process. The purpose of this study was to observe the morphological changes of the tooth tissue after argon ion beam etching. Freshly extracted human intact teeth and the teeth with moderate dentin caries were used. These teeth were cut longitudinally, embedded in an epoxy resin, and then polished. After the FE-SEM observation of the polished surfaces, the surfaces were subjected to the argon ion beam etching for 30, 90, and 180 seconds. Then, the morphological changes of the intact enamel, intact dentin, and caries-affected dentin after argon ion beam etching were carefully observed under the FESEM. It was proved that by using this technique, enamel surface and relatively harder intratubular dentin were not damaged compared to intertubular dentin. This tendency was more pronounced for the caries-affected dentin. It was concluded that the argon ion beam could etch not only the hydroxyapatite but also the collagen fibers of the dentin to some extent depends on the side of the tooth substrate.

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The aim of this in vitro study was to evaluate the bonding durability both to enamel and dentin of three fluoride-releasing enamel/dentin adhesive systems-experimental ABF and Imperva Fluorobond as a 2-step type (self-etching primer+adhesive) and Reactmer as a 1- step type (self-etching-priming-adhesive). The tensile bond strength was determined after 1 day in 37°C water, 360 days in 37°C water, and after thermocycling between 5°C and 55°C water for 5, 000 times. ABF showed high bond strength to enamel and dentin after 1 day. Bond strength in enamel was significantly degraded particularly by thermocycling, but fracture modes were almost all cohesive failures of bonding resins. Therefore, TBS values might be reflected by the tensile strength of bonding resin and real bond strengths at interface must be higher than the values obtained from the TBS tests. Fluorobond indicated the similar dentin bonding durability to ABF, but bond strength to enamel was inferior. Adhesive failures were mainly observed in enamel: thereby bonding durability to enamel was insufficient. In Reactmer, bond strengths both to enamel and dentin were significantly reduced by long-term water storage, and tensile fractured surfaces were cohesive failures of bonding/composite resin at all specimens. These findings suggest that the bonding resin of this system might degrade in water immersion with the passage of time.

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This study evaluated the effects of polishing after 24-hour storage in water on the gap formation around Class V restorations (n=10, 14 points, total points measured= 140) using one conventional glass-ionomer for high powder-liquid ratio (Fuji IX GP, GC), one resinmodified glass-ionomer for high powder-liquid ratio (Fuji VIII, GC), and one conventional glass-ionomer (Fuji II, GC) and one resin-modified glass-ionomer (Fuji II LC, GC) as controls. This study also examined the shear bond strength to enamel substrate and to dentin substrate and flexural strength of these restorative materials, which may influence the gap formation.
When the specimens of the four types of glass-ionomer material were polished immediately after the setting procedure, 80-120/140 (14 points × 10 cavities) gaps around the Class V restorative cavity were observed. In contract, only 10-20/140 gaps were observed when the specimens were polished after one-day storage. Significant differences in the four glassionomer restorative materials were observed between immediate polishing and polishing after one-day storage.
Bond strength and flexural strength played important roles in reducing the gap formation in Class V restorative cavity with four glass-ionomer restorative materials. In contract, the effect of the high powder-liquid ratio did not play an important role in reducing the gap formation for conventional and resin-modified glass-ionomer restorative materials.

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The rapid growth of light-cured materials has been resulted in a general need and more frequent use of curing units. Several types of curing units offer to optimize polymerization of resin composites in a given situation. A curing unit which utilize a solid state light emitting diode (LED) as a light source has been developed. Though spectral distributions of LED curing units are thought to be suitable for polymerization of visible light-cured resins, little is known about the curing characteristics of the LED curing units. The purpose of this study was to evaluate the effect of LED curing units on mechanical properties of light-cured resins.
LED curing units Aqua Blue (Toesco) and Lux O Max (Akeda Dental), and a halogen lump curing unit Optilux 400 (Demetron) as a control, were used. Depth of cure and Knoop hardness number on longitudinally sectioned surface of Clearfil AP-X (Kuraray Medical), Lite-Fil II A (Shofu) and Filtek Z250 (3M ESPE) were measured. From the results of this study, depth of cure and Knoop hardness number of the light-cured resins polymerized with the LED curing unit, whose light intensity was lower than those of the halogen lump curing unit, were lower and the need of prolonged irradiation time was indicated.

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The purpose of this study was to evaluate the adhesive efficiencies of four one-step bonding systems (AQ, OB, RB, XB) which were recently commercially available, comparing with that of the two-step wet-bonding system (EX) with acid etching. The influences of grinding condition on bonding to tooth substrates were examined by measuring shear bond strengths to bovine enamel and dentin polished up with 150, 600 or 1, 000-grid waterproof abrasive paper.
The bond strengths of one-step bonding systems to enamel were in the range of 13.5 to 21.3 MPa, and generally lower than those of EX (21.5-23.8 MPa). Especially, for AQand OB, the bond strengths to enamel ground with 150 and 600-grid papers were significantly lower than that ground with 1000-grid paper. The bond strengths of one-step systems to dentin varied among systems and were almost equal to those of EX (10.2-16.0 MPa). AQ, OB and RB showed the bond strengths of 12.4-15.4, 11.4-13.0 and 9.2-10.3 MPa, respectively. For these systems, there was not a significant difference among bond strengths with grinding condition. For XB (12.2-17.3 MPa), however, the bond strength to dentin ground with 150-grid paper was significantly higher. For EX, the bond strength to dentin ground with 1000-grid paper was significantly lower.

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The halogen lamp curing unit (HA) was popularly used to cure composite resin. Recently various light-curing units have been developed and used clinically, such as light-curing unit using Xenon-lamp (XE) and blue light-emitting diode (LED). These light-curing units have merits in shorter irradiation time and reduction of amount of fever. However little is known about the influence on cure and adhesion of composite resin to tooth. The present study aimed to examine the influence on hardness and bond strength of composite resin by using these light-curing units. The light intensity of these light curing units were measured. Three kinds of composite resins were used in this study. The Vickers hardness on these surfaces and the tensile bond strength were measured using freshly extracted bovine teeth. The light intensity of HA, XE, and LED was 348mW/cm², 1, 993mW/cm² and 131mW/cm², respectively. Vickers hardness of composite resins cured with XE and LED were lower than those cured with HA. The results indicated that XE was advantageous on curing bonding agent with the only 5 seconds because of its high light intensity.

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Recently, different curing units have been developed in an attempt to improve the performance of resin-based restorations. The purpose of this study was to evaluate the modulus of elasticity of a resin composite (Clearfil AP-X, Kuraray Medical), a bonding system (Clearfil Mega Bond, Kuraray Medical), hybrid layer and dentin substrate of class II restoration in extracted human third molar teeth. Three curing units were employed: a halogen lamp (Candelux, Morita), a metal halide (experimental, Moritex), and a xenon (Arc-Light, Air Techniques) curing unit. The Young's modulus of elasticity was determined using nano-indentation tester (ENT-1100, Elionics) at the interfaces of gingival wall, axial wall, and pulpal wall. Statistical analysis was performed using the analysis of variances and multiple comparison at 95% confident interval. Different curing units and different sites of examination had no influence on the modulus of elasticity of resin composite, adhesive resin, hybrid layer and dentin (p=0.31, p=0.56). Statistically significant differences of the modulus of elasticity among resin composite, adhesive resin, hybrid layer, and dentin were demonstrated (p<0.001).

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The purpose of the current study was to evaluate clinical performance of resin-bonded fixed partial dentures (FPDs) seated with specific materials and technique. The FPDs were made from a cobalt-chromium alloy (Biocast), air-abraded with alumina, and seated with a tri-n-butylborane initiated adhesive resin (Super-Bond). Abutment enamel was etched with phosphoric acid prior to bonding procedure. A total of 10 FPDs and 20 abutments were clinically evaluated. During an average observation period of 15 years and 3 months, detachment occurred in the two abutments of different cases. An interface failure between the tooth and the luting agent was detected in one abutment, whereas recurrent dental caries was observed in the abutment of the other case. It was suggested that the materials and technique employed were clinically reliable as long as enamel surfaces had been properly etched with phosphoric acid.

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We examined the adhesion of 4 kinds of direct bonding materials to teeth and plaque accumulation on experimental orthodontic composite resin with Improved surface reaction type Pre-Reacted Glass Ionomer (IS-PRG) filler.
The tensile adhesive strength of experimental orthodontic composite resin with 3.2wt% IS-PRG filler was similar to that of the control group in which Transbond (3M) was used.
Test resins containing IS-PRG produced showed the anti-plaque effects on the resin surface in this study.
These result indicate the fluoride released from IS-PRG filler is connected with prevention of plaque accumulation on the surface.

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