The aim of this study was to evaluate the effect of artificial saliva during enamel bleaching for 12 weeks in vitro. Cut bovine incisors were classified into six groups. In Group C, enamel specimens were immersed in artificial saliva (pH 6.5) for 12 weeks as a control. In Groups Hw and Hr, the enamel specimens were bleached with HiLite (containing 35% hydrogen peroxide) once a week for 12 weeks. In the Group Hw, the specimens were kept in deionized water along with being subjected to bleaching. On the other hand, in Group Hr, the artificial saliva was used for keeping them. An acid resistance test was performed in Groups CD, HwD, and HrD following a 6 week treatment period. Compared with Group C, slight demineralization with 60vol% mineral was detected in Group Hw. The integrated mineral loss (IML) was significantly higher than that in Group C. Also, the nano-hardness value of the surface was decreased. On the other hand, the mineral profile of Group Hr was similar to that of Group C, and no subsurface lesions were detected. Furthermore, the nano-hardness of the surface did not decrease. The acid-resistance tests showed lesions in the CD, HwD, and HrD groups; there were no significant differences between the groups. Raman spectra from the surface of Group Hr showed that the bleached surfaces had a more intense phosphate peak than those of non-bleached surfaces. A difference was not recognized at other depths in the cross-cut sections. From the results of this study of long-term bleaching for 12 weeks, we can conclude that saliva in the oral cavity replenishes mineral elements on bleached surfaces.

View full abstract

It has been reported that nowadays, to diagnose root fracture by the naked eyes correctly, dyes such as iodine, methylene blue or caries detector solution, measurement of electric impedance, transillumination, fiberoptic endoscope, microscope, bite test and ultrasonic devices have been used. However, these methods have not been widely used for diagnosis because they are not subjective and correct in cases of imperfect fracture or cracks. The purpose of this study was to examine the possibility of diagnosis of root fracture by DIAGNOdent®. As a basic study, human roots of teeth without fracture were used to examine the relationship between the values by DIAGNOdent® (D values) and the dependence on time and concentration of methylene blue dye solution. Artificial grooves to simulate root fractures were made on the root surfaces and the relationships between D values and the widths or depths of grooves with or without dye solution were examined. Next, artificial root fractures were made on the roots of teeth, and the relationship between D values and presence or absence of dye solution and the effect of ethanol concentration on D values were also examined. Statistical analyses were performed by the Mann-Whitney U test. D values were time-dependent up to 5 minutes without changes after 5 minutes, and concentration-dependent with dye solution. D values were also dependent on the width and depth of grooves with dye solution. D values increased significantly after root fracture, especially using dye solution or dye solution including 20% or 40% ethanol concentration. These results suggest that root fracture could be diagnosed by DIAGNOdent® with methylene blue dye solution.

View full abstract

We have found and reported an unusual case in which conventional intraoral radiography and panoramic radiography could not prove the presence and expansion of periapical lesions in each root of multirooted teeth. This study suggested that the important information acquired by 3DX® Multi-Image micro Computed tomography could help us in making an accurate diagnosis and determining a practical treatment.

View full abstract

The objective of this study was to investigate the ultra-morphological smear layers produced by various dental instruments, and to evaluate the effect of the smear layers on the short-and long-term bonding effectiveness of two commercially available one-step adhesive systems bonded to dentin. Smear layers were produced on flattened mid-coronal dentin surfaces of extracted human molars by one of the following materials: two types of diamond burs (regular-grit or superfine-grit) or two types of SiC papers (#600 or #2,000). Thickness of the smear layers and size of the particles of the four materials were measured by SEM. TEM images of the smear layers were taken, as well. Two types of dentin surfaces produced using a regular-grit diamond bur and #2,000 SiC paper were conditioned with either Clearfil S³Bond (Kuraray, S3) or Absolute (Dentsply-Sankin, AB) without light-curing, rinsed with acetone, and observed by SEM. Moreover, resin composites (Z-100, 3M ESPE) were bonded with either S3 or AB, and incrementally built-up on two types of the dentin surfaces. The specimens were sectioned into slabs and further trimmed into an hourglass shape with an interface area of approximately 1mm². They were left untouched or thermo-cycled (100,000 cycles). Micro-tensile bond strength (μTBS) testing and ultra-morphological observation by TEM were performed. The larger the particle sizes were, the thicker the width of the smear layer became, although TEM images of smear layers produced by the four materials revealed no differences in ultra-morphology. For S3, thick smear layers were not removed completely, whereas AB removed the smear layers despite their thickness. Whether the specimens were thermo-cycled or not, the μTBS of S3 on the dentin surface with thick smear layers was significantly lower than that of the thin, smear layer covered dentin surface. However, the μTBS of AB was not affected by the thickness of smear layers. For both adhesives, 100,000 thermo-cycles significantly decreased μTBS despite the thickness of the smear layers, and TEM images revealed scattered voids, which appears to be an indication of interfacial degradation. It is concluded that 1) the thickness of the smear layer produced on the dentin surface was dependent on the materials used; 2) thick smear layers affected the bonding effectiveness of S3 which had a low ability to dissolve the smear layers; 3) smear layers did not always affect the bonding effectiveness because AB completely removed the smear layers regardless of their thickness; and 4) the bonding effectiveness of one-step adhesive systems decreased after long-term thermo-cycling.

View full abstract

Objectives: Previous studies showed that fluorine can enhance enamel remineralization. This effect is expected and many fluoride-releasing materials are developed in resin systems. However, the clinical evaluation of resin systems is not certain. The automatic pH-cycling system used from the former study can simulate daily changes in pH that occur in the oral cavity. Therefore, the aim of this study was to evaluate the caries inhibition effect of fluoride-releasing resin composites using this pH-cycling system. Materials and Methods: BS groups consisted of Beautifil II (F+) and Fluoro Bond Shake One (F+), AMF groups consisted of Clearfil AP-X and Clearfil Mega Bond FA (F+), UM groups consisted of Unifil-Flow (F+) and Clearfil Mega Bond, and SM groups consisted of Solare and Clearfil Mega Bond. The buccal surface of human premolars was filled up with each material, and a 150μm thick single-section specimen was prepared and the polished surface was coated with wax. The examination condition was 6 cycles/day for five weeks, and a demineralizing solution (lactic acid solution, pH 4.5) and remineralizing solution (HEPES solution, pH 7.0) were used to reproduce the same pH changes that typically occur in the oral cavity. For all groups, the Transverse Micro Radiography (TMR) image of each specimen was examined to evaluate the progression of caries with respect to integrated mineral loss and lesion depth. Results: Evaluation of the results of integrated mineral loss showed that, at 1w, the BS group was the significantly lowest, followed by the SM group, AMF group, and UM group, respectively. At 3w, the BS group was the lowest, followed by the AMF group, UM group, and SM group, respectively. At 5w, the order was the same as that for 3w. The results for lesion depth showed that, at 1w, the UM group was the lowest, followed by the AMF group, BS group, and SM group, respectively. At 3w, the BS group was the lowest, followed by the AMF group, SM group, and UM group, respectively. At 5w, the BS group was the lowest, followed by the AMF group, UM group, and SM group, respectively. With respect to fluoride release, the inclusion of Beautifil II and Unifil-Flow in lactic acid solutions was significantly high compared with inclusion in de-ionized-water. In terms of bonding materials, there was no statistically significant difference between the use of Fluoro Bond Shake One and Clearfil Mega Bond FA. Conclusion: In this study, it turned out that the caries inhibition effect was high in the BS group, and the effect of fluorine was low in the UM group. From this result, caries inhibition effect differs depending on the type of fluoride-releasing resin composites used. It is thought that clarifying the differences among these fluoride-releasing materials can lead to the development of new, more effective materials.

View full abstract

It has been reported that chemotherapy influences tooth abnormalities in children with neuroblastoma. This study examined the influence of anticancer agents on the formation of deciduous teeth, and the relationship between the absence of teeth and the period of chemotherapy. The case was a female infant, who underwent excision of an abdominal tumor at 11 months old and was diagnosed as having progressive neuroblastoma (stage 1). After operation, the neuroblastoma was treated with chemotherapy for 4 months (from 1 year and 1 month old to 1 year and 4 months old) in the pediatric department of a university hospital, Kyoto Prefectural University of Medicine. At 3 years and 7 months old and 6 years and 5 months old, we performed oral and orthopantomography examination and analyzed deciduous teeth for whether anticancer agents containing platinum influence the formation of deciduous teeth using electron probe micro analysis (EPMA). As a result, the absence of teeth was detected in the first and second premolars. The period of embryonic formation and calcification of teeth coincided with the period of chemotherapy. Deciduous teeth showed no morphologic change and there were no teeth whose enamel and dentin clearly contained platinum. These results suggest that chemotherapy has an influence when teeth are immature but not when teeth are mature.

View full abstract

It has been reported that 95% of diabetes mellitus patients exhibit non-insulin dependent type 2 disease in Japan. Diabetes mellitus is attracting attention as a risk factor of periodontal disease. The formation and accumulation of advanced glycation end products (AGEs) are known to progress faster under diabetes, and there is accumulating evidence that AGEs play a role in the development of diabetes by inducing islet beta cell damage and insulin resistance. In early wound healing, the type III collagen is an important factor during tissue maturity. We created periodontal defects in the maxillary first molars of normal and type 2 diabetes model rats in order to examine the relationship between AGEs and type III collagen. We observed pathologically the early wound healing of periodontal defects. Palatal dehiscence defects were surgically created on the bilateral maxillary first molars in normal and type 2 diabetes model rats. Rats were euthanized at 3, 5, 7 and 14 days after surgical operation, and perfusion-fixed, followed by removal of the periodontium including maxillary first molar and preparation of paraffin sections. Paraffin sections were stained with hematoxilin-eosin (HE). AGEs and type III collagen were detected immunohistochemically. At 5 days and 7 days, localization of type III collagen was stronger in the control group than the experimental group. Type III collagen fibers were irregularly arranged in the experimental group at 14 days. There were many amorphous capillary vessels, and AGEs localized the vascular endothelium of the vessels in all experimental groups. AGEs react with the receptor for AGEs (RAGE), then promote the production of nitric oxide in vascular endothelium. A large amount of nitric oxide might decrease the production of type III collagen and increase amorphous blood capillaries via fibroblasts, vascular endothelium and pericyte. It is suggested that AGEs inhibit the formation of type III collagen, produce poor amorphous capillary vessels, and interfere in the early period of the wound healing process.

View full abstract

Recently resin composite restoration has been applied in various clinical cases with the development and improvement of dental devices and materials. However, the fatal occurrence of polymerization shrinkage within a resin composite restorative is an important factor that affects the clinical prognosis of the restoration. The purpose of this study was to examine the effect of cavity configuration on the bonding reliability of two self-etch adhesive systems, i.e., an one-bottle all-in-one system; Clearfil Tri-S Bond (TS, Kuraray Medical), and a two-bottle self-etching primer system; Clearfil Mega Bond (MB, Kuraray Medical), to cavity floor dentin. The occlusal enamel of extracted human molars was ground horizontally to expose a flat dentin surface. Five standardized cavities, i.e., Class I (4.0mm long, 4.0mm wide, 2.0mm deep, C-value=3.0), MO (1.7), MOD (1.0), MODB (0.7), and Flat (0.3), were prepared on the flat dentin surface (n=10, each cavity). Every cavity was pretreated with either TS or MB, in accordance with the manufacturer's instructions, and the same volume of universal resin composite restorative, Clearfil AP-X (Kuraray Medical), was placed into each cavity and then light cured. After storage in a moisture box at 37℃ for 24 hours, restored tooth specimens were sectioned vertically into four quadrate stick form specimens (1.0×1.0mm). The micro-tensile bond strengths (μ-TBS) of the stick specimens were then measured. The data of the μ-TBS obtained from the five types of cavities restored with two different adhesive systems were examined using Weibull analysis (n=20). Regardless of the system, the Weibull modulus of Class I (3.0) indicated the maximum value and that of Flat (0.3) indicated the minimum value. The Weibull modulus of the standardized cavity increased with decreasing C-value, and the value of MB was statistically greater than that of TS. From the results, the bonding reliability of the cavity increased as the C-value decreased. The reliability of MB was superior to TS. However, that of MB was superior to TS only for Class I (3.0); there were no differences in the reliability between the two systems in the other four cavity configurations (1.7-0.3).

View full abstract

Recently, improvements in the adhesiveness of composite resins, increased esthetic demands made by patients, and wider acceptance of the concept of MI have led to the more frequent use composite resins for esthetic restorations. In order to achieve highly esthetic restorations, it is important to select the color of the composite resin by taking in to account the effects of surrounding colors. With higher esthetic demands, composite resins that are used for filling are applied in layers, and due to the chameleon effect, it is now possible to achieve restorations that closer to the color of natural teeth. However, when matching colors in clinical settings, various conditions need to be considered with respect to shade selection and morphological recovery, and this requires considerable skill. In this study, the effects of base chromatic colors on the colors of composite resins were investigated. In this study, the following four composite resins were used: Beautifil II, Estelite Σ, Filtek™ Supreme DL, and Tetric Ceram. A3 shade was used in all cases. As bases, the standard white board, black board, and six colors of low-foam vinyl chloride boards were used. Round discs were prepared and placed on each base, and then color analysis was performed using a spectrophotometer. The L* value of the bases in relation to the color of the composite resins was the highest for black, followed by red, blue, green, and yellow, in this order. The a* value was the highest for red and lowest for green, while the b* value was the highest for yellow and lowest for blue. The color difference ΔE*ab between the standard white board and each base was the highest for white, followed by green, blue, yellow, red, and black, in this order. With each composite resin, the color difference ΔE*ab for each base was calculated in relation to the color measured on the standard white board. For all composite resins, ΔE*ab was the highest for white, followed by yellow, red, green, black, and blue, in this order. The fact that there were differences between the color difference of the bases and color difference of the composite resins on bases with different colors, indicates that the color of the composite resins is affected by not only base brightness, but also base saturation. Based on color differences, the color of the composite resins is less likely to be affected by red and green base colors.

View full abstract

The purpose of this study was to evaluate the effectiveness of the additional application of HEMA solution to the adhesion of one-bottle self-etching systems to caries-affected dentin. Sound, artificial demineralized and remineralized dentin were used in this study. Demineralized dentin was created by immersion into a demineralization solution for 5 days. Remineralized dentin was created by immersion into a remineralization solution for 1 or 4 weeks after demineralization. Clearfil Tri-S Bond (Kuraray Medical) was used for adhesion of resin composite to the dentin. The dentin surfaces were treated as follows: (A) in accordance with the manufacturer's instructions (control), (B) after additional application of HEMA/propanediol solution for 60 seconds and application of Tri-S Bond in accordance with the manufacturer's instructions (H group), and (C) after additional application of HEMA/propanediol solution for 60 seconds and application of Tri-S Bond using an agitation technique (H/A group). Resin composites (Clearfil AP-X) were built up incrementally in accordance with the manufacturer's instructions. Specimens were stored in water at 37℃ for 24 hours, after which the teeth were serially sectioned into multiple slices. The micro-tensile bond strength of the individual specimens was then measured in a universal testing machine at a crosshead speed of 1.0mm/min. A confocal laser scanning microscope (CLSM) was used to evaluate the penetration of the primer into the dentin in each group. There were no significant differences in the bond strength between sound and demineralized dentin groups in the control group. Bond strengths in remineralized dentin (both 1 and 4 weeks) were significantly lower than those in sound and demineralized dentin. Normal penetration of monomer into the dentin via dentinal tubules was observed in sound dentin. On the other hand, in the demineralized and remineralized dentin (both 1 and 4 weeks), the monomer hardly penetrated at all into dentin as it did in sound dentin. The bond strengths in the three groups (sound, 1-week and 4-week remineralized dentin), with the exception of the demineralized dentin, showed improvement by additional application of HEMA/propanediol. In this study, the further improvement of bond strengths by the application of HEMA/propanediol and performing of additional agitation technique was not accepted. In conclusion, it is suggested that HEMA/propanediol application might increase the bond strength in sound and remineralized dentin.

View full abstract

The effects of mouthrinse on the surface properties of resin matrix in a light-curing resin composite, immersed in several types of mouthrinse, were investigated by dynamic hardness measurement. A Bis-GMA-based resin composite Z250, an alcohol-containing mouthrinse Listerine® and a non-alcohol mouthrinse Ora² were used in this study As a reference for the mouthrinses, distilled water and 20% ethanol were used. Disk-shaped specimens cured by irradiation of visible light were immersed in either mouthrinses or reference solutions. Then the dynamic hardness, Knoop hardness, elastic modulus, as well as plastic deformation and elastic deformation, were measured using a dynamic ultra-micro hardness tester. The immersion conditions were set as follows: 1) six cycles of 30sec immersion at 6hr intervals, 2) six cycles of 10min immersion at 6hr intervals, and 3) consecutive 60min immersion. The dynamic hardness and elastic modulus of the specimens immersed in either Listerine® or 20% ethanol were significantly decreased, regardless of the immersion conditions, compared to the immersion in water. The immersion in Ora² caused no significant change in the surface properties. These results suggested that the deterioration of the resin surface was caused by the action of ethanol as a component, and that daily use of ethanol-containing mouthrinses could soften the surface of the resin, lower its frictional resistance and accelerate the deterioration of the resin composite surface.

View full abstract