This study aimed to develop an all-in-one adhesive resin available for both dry and moist tooth surfaces. An experimental all-in-one adhesive, containing phosphoric acid monomers and Bis-GMA as main components, and ethanol/acetone/water for solvents, was designed for the project. Bovine incisors were ground with #600 SiC paper to expose flat enamel and dentin surfaces. The teeth were divided into dry and moist groups. In the dry group, the surface was strongly air-dried for 5 s while in the moist group, the surface was wet with a saliva-contaminated solution. The specimens were made to measure the tensile bond strength after storage in water for 24 h (n=6). Furthermore, human molars were ground with #1000 SiC paper to expose flat enamel and dentin. The specimens for observing the bonding interface structure under FESEM were made under the dry or moist conditions. The tensile bond strength for enamel and dentin was 21.6±3.8 and 20.3±2.0 MPa, respectively, in the dry group; and 21.6±1.8 and 21.0±6.1 MPa, respectively, in the moist group. Statistical analysis revealed no significant difference between groups (p>0.05). SEM figures showed tight adhesion to enamel and dentin in both the dry and moist groups. It was concluded that the experimental all-in-one adhesive might be useful for both moist and dry surfaces.

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Recently, fiber-reinforced resin composites, which show similar elastic modulus to dentin and high bonding efficacy, have been widely used as a post to reduce root fractures, achieve high retention, and ensure root canal sealing. Many resin composite core build-up systems containing dual-cure self-etching adhesive are on the market. SHOFU INC. developed the “BeautiCore System” as a bioactive resin core system, applying original S-PRG technology. In this study, we observed the interfacial structure between the radicular or coronal dentin and the resin composite under FE-SEM. The results showed that BeautiCore Flow Paste/radicular dentin junction or BeautiCore Paste/coronal dentin junction was very tight. However, the adhesive layer was very thin and could not be clearly observed. Furthermore, the hybrid layer could not be recognized at the superficial dentin surface. We thought that this system was clinically useful based on the high bonding efficacy to dentin, and easy buildup performance with two different kinds of flow resin composite.

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The purpose of this study was to evaluate the shear bond strength of orthodontic brackets to human enamel and the enamel surface morphology using three orthodontic adhesives: PrimeMaster LC, TransBondTM XT and BeautyOrthoBond. Unground enamel of extracted human premolar was treated according to the manufacturer’s instructions. For evaluation, stainless steel brackets were bonded to the enamel surface under ambient conditions (temperature: 23°C, relative humidity: 50±5%) or humid conditions (temperature: 37°C, relative humidity: ≥ 95%) prior to being stored under dH2O at 37°C for 24 h. The specimens treated under ambient conditions were divided into two groups and one was subjected to thermocycling for 5,000 cycles at temperatures alternating between 5 and 55°C. Shear bond strength testing of all specimens was performed using a universal loading machine at a cross-head speed of 1.0 mm/min. Data was statistically analyzed by ANOVA and Tukey’s test, and failure modes were assigned to each specimen. Although the shear bond strength of PrimeMaster LC was comparable to or better than that of TransBondTM XT, the shear bond strength of BeautyOrthoBond was significantly low. After the shear bond strength test, the dominant failure mode showed that there was a difference among the three adhesive systems. PrimeMaster LC indicated that the failure mode was mostly at the enamel/adhesive and cohesive failures within the resin owing to the effect of adhesion promoting monomers, whereas those treated with TransBondTM XT occasionally showed enamel fracture. These findings suggest a difference in bonding performance of the three orthodontic adhesives.

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The purpose of this study was to examine the influence of various mouthrinses on impacting-sliding characteristics of bovine enamel. Thirty bovine mandibular incisors were mounted in self-curing resin and the facial enamel surfaces were wet ground with #2,000 SiC paper. Solutions of five mouthrinses: ConCool F (CF, pH5.4), Check-UP (CU, pH5.8), Listerine (LR, pH4.2), Listerine Zero (LZ, pH4.2), Shumitekuto (SH, pH6.8), and distilled water (DW, pH7.2) as a control were used. The enamel specimens immersed in one of the solutions were subjected to the impacting-sliding wear test using stainless steel antagonist tips up to 1,000 cycles, after which the wear loss was recorded. Furthermore, specimen surfaces were observed using 3D laser scanning microscopy and scanning electron microscopy. Knoop hardness measurement of the enamel surface was also conducted. The wear loss ranged from 7.5 to 24.3×104 μm3 for the 100-cycle group, from 11.8 to 80.9×104 μm3 for the 500-cycle group, and from 16.2 to 137.8×104 μm3 for the 1,000-cycle group. Acidic mouthrinses (LR and LZ) showed significantly higher wear loss compared to the other mouthrinses (p<0.05). Lower Knoop hardness was detected for the specimens immersed in LR and LZ solutions compared to the other solutions. These results implied that the impacting-sliding enamel wear differed according to the chemical components and pH of the mouthrinses used. It was also suggested that various wear mechanisms such as adhesive wear and tribochemical wear were involved in the impacting-sliding enamel wear.

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The purpose of this study was to examine the actual adhesion state of direct resin composite restoration applied with the resin core system. A standardized Class 2 MO core cavity was prepared in 60 human extracted lower first molars. Pretreatment for the cavity walls and resin core material filling of the pulp cavity were performed with Clearfil DC Bond＋DC core Automix (DC) or Clearfil Bond SE ONE + DC core Automix ONE (SE). Then, the coronal part of the cavity was restored with Clearfil AP-X. Restored specimens were divided into two groups (n=15): one with dynamic load stress (S+) and the other without the stress (S-). For the S+ group, dynamic load stress (16 kgf×3×105 times) was applied in water at 37℃. For the S- group, no stress was applied. The specimens were trimmed to standardized beam specimens, and micro-tensile bond strength (μ-TBS) to four intra-cavity dentin walls, gingival wall (G), pulpal-floor wall (P), coronal-axial wall (CA), and pulpal-axial wall (PA) were measured. The data was examined using ANOVA and Weibull analysis. The μ-TBS to G was significantly higher than that of the other walls except for the value of DC (S-) to P, regardless of dynamic load stress and resin core system. The influence of load stress was significant only for the μ-TBS to P. The Weibull modulus of G was significantly greater than that of the other dentin walls, regardless of the stress and the system. At both 10% and 90% probabilities of failure levels, the adhesion on the four dentin walls tended to require less stress to debond by dynamic load stress, regardless of the resin core system.

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The objective of this study was to investigate the influence of the concentration of hydrogen peroxide contained in bleaching agents on resin-bond strength to bleached enamel. Flat human enamel surfaces were bleached with Pyrenees (P: 3.5% H2O2, Nissin), TiON In Office (T: 22.5% H2O2, GC) or Hi Lite (H: 35% H2O2, Shofu). The bleached specimens were stored in 37°C water for 0 (no-storage), 1, 3, 7, or 14 days. Non-bleached specimens were prepared as a control (C). All specimens were prepared with a resin composite and were subjected to the compressive-shear-bond test and fracture mode observation after 24 h storage in 37°C saline. In the no-storage specimens, T0 and H0 demonstrated significantly lower bond strength with adhesive failure compared to that of C with mixed failure, although P0 exhibited almost the same bond strength and mixed fracture pattern as C. After 1-day storage, P1, T1 and H1 showed almost the same bond strength with mixed fracture as C. No significant difference in bond strength was found after 3-, 7- and 14-day storage regardless of the peroxide concentration. The immediate bond strength to bleached enamel was reduced in accordance with the concentration of hydrogen peroxide. No significant differences were found in the rate of recovery of bonding performance with time regardless of the peroxide concentration. Resin restoration in a bleached tooth must be performed after a lapse of more than one day.

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Composite resin buildups with fiber posts are widely used because of their high effectiveness in the prevention of root fractures and high aesthetics of the gingival margin. The fiber post can basically be installed at the center of the composite resin core. However, installation in the appropriate position cannot depend on only experience and intuition. We have devised a new laboratory procedure to determine the exact position of the fiber post for composite resin buildups using a silicone index. The “Optical Fiber Post” used in this report has high optical transparency and excellent mechanical strength by using a double structure integrated with the sleeve. The new laboratory procedure using a silicone index was the most reliable and efficient when the double structure with optical fiber post and sleeve was used. When using the silicone index procedure, molding and pressing can be simultaneously performed and a sufficient resin core can be fabricated even by an inexperienced technician.

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