The purpose of this study was to evaluate the coronal leakage of cemented prototype fiber post using a new dye penetration method. Thirty-nine extracted single-rooted lower premolars were used. Their crowns were removed, and the root lengths were standardized at 12 mm. Two roots without root canal preparation were used as negative controls. In the remaining 37 roots, canals were instrumented using ISO size #15-#40 K-files with the standardized method, and a 6 mm-long post space was prepared for each root at the coronal portion. Then, an apical 6 mm of all the roots was resected. Two of the prepared roots were used as positive controls. The remaining 35 roots were randomly divided into 5 groups of 7 roots each, and the post space was filled with one of the following methods: Group A: AD post (Kuraray)+DC core (Kuraray) Group B: DC core Group C: Fibrekor Post (Pentron)+BUILD-IT FR (Pentron) Group D: AD post+Ketac-Cem (3M Espe) Group E: prototype fiber post+DC core A polypropylene tube that contained 0.06 % methylene blue dye solution was attached to the coronal portion of the root. Two millimeters of the apical portion was immersed into distilled water in a glass bottle. The amount of dye emerging through the root into the water was measured with a spectrophotometer at 1, 4, 8, 15, and 30 days after the immersion. Data obtained were statistically analyzed using ANOVA and the Tuke-Kramer test at the 5 % significance level. The amount of dye leakage in all experimental groups increased with the immersion period. There was a significant difference between the groups for experimental groups increased with the immersion period. There was a significant difference between the groups for experimental time intervals (p<0.05, 2-way ANOVA). There was no significant interaction between groups. Statistical analysis revealed that the amount of dye leakage in Group D on the 30th day was significantly larger than that in the other groups (p<0.05, Tukey-Kramer). The results showed that a good sealing was obtained in all post groups when dentin adhesive cements were used. Group E was comparable with currently available fiber post and composite resin systems.

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New approaches to bonding restorative materials to tooth substrates without phosphoric-acid etching, such as single-step self-etch systems, have recently been introduced. Oral environmental conditions may also influence the bond strength of the single-ap-plication bonding systems, but little information on this is available. The purpose of this study was to investigate the influence of relative humidity on the bond strength produced by these simplified bonding systems. Bonding systems employed in this study were G-Bond (GC), i Bond (Heraeus Kulzer), One-up Bond F Plus (Tokuyama Dental), Fluoro Bond Shake One (Shofu), and Clearfil tri-S Bond (Kuraray Medical). Mandibular incisors were extracted from 2-3 year-old cattle and the dentin surfaces were wet ground with #600 SiC paper. The teeth were transferred to a controlled temperature and humidity chamber and left for 5 min to bring them to the test environmental conditions. Specimens were prepared in 3 different environmental conditions: A) 25±0.5℃, 50±5% RH, B) 25±0.5℃, 80±5% RH and C) 25±0.5℃, 95±5% RH. The resin paster of each bonding system were condensed into a Duracon® mold (φ4×2mm) and then irradiated. The finished specimens were transferred to distilled water at 37℃ for 24h from the start of light exposure. Ten specimens per group were tested with an Instron testing machine (Type 4204, Instron) in a shear mode at a crosshead speed of 1.0 mm/min. The results were as follows: 1. The dentin bond strengths of the single-step self-etch systems decreased with increase of RH, and significant decreases in bond strengths were observed except for G-Bond and One-up Bond F Plus. 2. According to the fracture mode after the test, adhesive failure tended to increase with increase of RH.

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Root canal filling is important to seal off the root-canal system completely to prevent bacterial ingress and activity. In this study, the sealing ability of RoekoSeal Automix® was evaluated by the dye penetration test. The setting time, solubility and disintegration, film thickness and flow were also investigated as sealing characteristics. The significance of RoekoSeal Automix® in root filling was examined in comparison with non-eugenol root-canal sealer (Canals®-N.) In the dye penetration test, 42 human single-rooted teeth were used. After preparation of root canals with a K-file to size (#70). 15 teeth were obturated by the lateral condensation technique using RoekoSeal Automix® and gutta-percha points, and were divided into three groups of five teeth. Each group was placed in indian ink at 37℃for 1, 2 and 4 weeks, respectively. A transparent specimen was made from each tooth and the length of dye penetration from the root apex was measured. The same procedure was done for Canals®-N using 15 teeth and another 12 teeth were used as positive and negative controls. The setting time, solubility and disintegration, film thickness and flow were also measured referring to ISO 1566 and 6876. With RoekoSeal Automix®, the lengths of dye penetration for 1, 2 and 4 weeks were 1.62 mm, 1.42 mm and 1.43 mm, respectively, while those of Canals®-N were 2.19 mm, 2.79 mm and 3.11 mm, respectively. A significant difference was found between RoekoSeal Automix® and Canals®-N by 2way ANOVA (p<0.01). The setting time of RoekoSeal Automix® was 85.33 minutes; it was much shorter than Canals®-N of 7 days. The solubility and disintegration, film thickness and flow of RoekoSeal Automix® also showed favorable characteristics for the root canal sealing and the differences between those of RoekoSeal Automix® and Canals®-N were significant by l-way ANOVA (p<0.01). These findings suggested that RoekoSeal Automix® possesses good features in the setting time, solubility and disintegration, film thickness and flow, which would contribute to the root-canal sealing ability of RoekoSeal Automix®

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This study examined the pulpal reactions to adhesive systems that employ a self-etching primer containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB), and evaluated its in vivo bonding ability by animal tests. Class V cavities were prepared on the buccal surfaces of the anterior teeth of beagle dogs and composite filling was performed using the self-etching primer containing 5% MDPB in combination with experimental fluoride-releasing bonding resin or commercial bonding resin. After 7, 30 or 75 days, the teeth were extracted and serial thin sections were prepared following fixation, demineralization, and resin-embedding. The sections were stained with hematoxylin and eosin, and the pulp response was histopathologically examined according to the criteria of ISO7405. In addition, after 7 days, the crown of the canine tooth restored with composites using 5 % MDPB-containing primer and experimental bonding resin was cut, and the ultrastructure of the resin-dentin interface was observed by transmission electron microscopy (TEM). Restoration with MDPB-containing primer either with experimental or commercial bonding resin resulted in no pulpal inflammation for all periods. TEM observation demonstrated integrity of the resindentin interface with the production of a 0.5-1 μm thick hybridized layer and obturation of dential tubules with resin. The results indicate that the self-etching system employing the antibacterial primer containing MDPB, which is utilized for commercial version Clearfil Mega Bond FA, shows excellent biocompatibility and produces an effective bond under in vivo conditions.

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MSX-1 is a member of the homeobox family, which plays important roles in industive tissue interactions during vertebrate organogenesis. As mice deficient in MSX-1 demonstrated tooth morphogenesis failure, MSX-1 could be a key factor controlling inductive signaling molecules between the dental epithelium and mesenchyme during tooth formation. Furthermore, it has been found that FGF8 expressed in dental mesenchyme induced MSX-1 in dental mesenchyme in early tooth development. These results indicated that the relationship between FGF8 and MSX-1 could be an important clue to elucidate dentinogenesis; however, few papers have studied the signaling pathways of MSX-1 expression induced by FGF8 in dental mesenchyme. In this study, we found that MSW-1 was induced by FGF8 throughout mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) in cultured dental pulp cells isolated from rat lower incisors. When MAPK/ERK activation was inhibited with a specific inhibitor (PD98059), MSX-1 expression was remarkably reduced. The specific inhibitor also significantly reduced MSX-1 expression induced by FGF8. Interestingly, the inhibitor had no effect on alkaline phosphatase, but blocked the cell proliferation stimulated by FGF8. These results suggest that MAPK/ERK is necessary for MSX-1 expression induced by FGF8, and plays important roles in dentinogenesis in rat dental mesenchymal cells.

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One of the promising applications of Er. YAG laser is disinfection of residual bacterial biofilm and microcolony in the root canal. However, little information is available regarding the influences of laser irradiation on residual intra-canal bacteria near the root apex. This in vivo study focused on the effects of Er: YAG laser irradiation on the viability of residual bacteria in the root canal around the root apex. Sixty samples from the root canals of 38 patients with chronic periapical periodontitis were examined and used to identify and quantify bacteria using a conventional bacterial culture technique. Forty-two root canals were irradiated by Er: YAG laser, and samples were obtained before and after irradiation. and the other 18 samples from non-irradiated teeth were used as controls. In addition, 5 other samples were observed for viability or death of bacterial cells using a live/dead stain and fluorescence microscope. Before irradiation, 14 bacterial species, detected in 15 of 42 samples examined, were identified. The average of detected bacterial cell number was 37.7 CFU. After irradiation, no bacteria was isolated in 9 of the 15 samples in which bacteria was detected before irradiation. Six bacterial species were isolated from the 6 samples after irradiation. In these 6 samples, the mean cell number detected was 1.7 CFU. From the microscopic observation, viable cells were found in 3 of the 5 samples examined before irradiation. In 1 of these 3 samples after irradiation, viable cells were found, but no dead cells were detected. The results of the present study suggest that Er: YAG laser irradiation against residual bacteria in the canal near the root apex was useful. It is considered that use of the Er: YAG laser in infected root canal treatments could be expanded, if the laser could be irradiated with a wide angle, and if the shape of the chip could be improved.

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The prognosis of root canal treatment largely depends on the quality of root canal filling. The shape of each root canal must be properly determined when performing root canal preparation. In the present study, the supernumerary root canal of a mandibular first premolar was examined by the isometric method and X-ray CT to ascertain its morphology before and after root canal preparation and after root canal filling. The results were as follows: 1. In the radiograph taken by the isometric method, the buccal and lingual root canals appeared like the mesial and distal root canals, respectively. 2. There was marked hypocalcification of the root canal wall on the lingual side of the buccal root canal and the buccal side of the lingual root canal. 3. Depending on the height of the orifice of root canals, root canal filling might be difficult to perfirm. These findings suggest that when performing root canal treatment in a supernumerary root canal, it is important to determine the morphology and position of the root canal by radiography, check the height of the origice of the root canal, and pay attention to avoid excessive widening of hypocalcified areas.

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Substance P (SP) induces the expression of proinflammatory cytokines, such as IL-6, which are implicated in pulpal inflammation. We examined whether SP induces IL-6 production using enzymelinked immunosorbent assay (ELISA) in human dental pulp cell (PF-10) cultures. SP induced IL-6 production after 2 h stimulation, and the production remarkably increased after 24 h to 48 h. The SP antagonist L703606 inhibited SP-induced IL-6 production in a dose-dependent manner. Extracellular signal-regulated kinase (ERK) and p38 mitogen-acti-vated protein kinase (MAPK) mediated SP-induced IL-6 production, as shown by the use of specific inhibitors of these kinases. Furthermore, in the siRNA experiments, specific siRNA for activator protein-1 (AP-1) and selective promoter factor 1 (Sp1) inhibited SP-induced IL-6 production. Our results suggest that ERK, p38 MAPK, AP-1, and Sp1 are key factors on the signaling pathway for SP-induced IL-6 production in human dental pulp cells.

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