Since the wavelength of Er:YAG laser closely matches the absorption wavelength of water, it has been reported that dentin for irradiation which contains water could be ablated by the laser. However, it is difficult to estimate the depth of dentin to be ablated by Er:YAG laser because it is considered to depend not only on the irradiation's energy output, pulse count, duration, method and shape of the tip, but also the properties of the dentin for irradiation. As for dentin for irradiation, it seems possible that affected dentin which may contain much water in the oral environment can be selectively and successfully removed by using Er:YAG laser. In this study, therefore, the ablating capacity of Er:YAG laser of different irradiation energies was examined in relation to the change in surface layer properties of test dentin for irradiation, that is, sound bovine dentin and artificially decalcified dentin. The ablated depth was determined after the test dentin surface was contact-irradiated by using the tip of a C400F at the same total energy and duration of irradiation. The influence of laser irradiation was examined by X-ray diffraction analysis(XRD), and the changed surface layer properties of the test dentin were observed by scanning electron microscope(SEM). The depth of dentin ablated by Er:YAG laser was found not to depend on the total amount of energy but was influenced by the energy output per pulse under the present experimental conditions. A good linear correlation was observed between the ablated depth and the energy output in sound dentin, suggesting that it may be possible to predict the depth to be ablated. In the case of decalcified dentin which seems to contain much water, the ablated depth tended to be greater compared with sound dentin. The depth of 240-290μm was observed at 56-112mJ/pulse・10sec, the level of which may serve as a predictor of the depth to be ablated. XRD findings of both dentin conditions indicated that a clearer structure of hydroxyapatite crystal could be obtained by Er:YAG laser irradiation. From SEM findings, various ablated forms were observed to be caused by the laser irradiation depending on the different conditions of the dentin surface layer, even though the energy output was the same.

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Dental papilla cells are composed by cranial neural crest-derived mesenchymal progenitors that can differentiate into odontoblasts via epithelial-mesenchymal interaction. However the differentiation potential of these cells remains largely unknown. We therefore attempted to establish immortalized mouse dental papilla cells, and investigated whether they possess odontoblast progenitors. Cells growing out from the dental papilla tissue of mouse incisors at postnatal 1 day were immortalized by human papillomaviruses type 16 E6 gene deleted with PDZ domain binding motif (MDP^E6). MDP^E6 was successfully immortalized and continuously grown beyond population doubling 80 without changing cell morphology or proliferation rate. To investigate the differentiation potential of MDP^E6, it was treated with osteogenic differentiation medium for 21 days. MDP^E6 showed high alkaline phosphatase activity and mineralized nodule formation. RT-PCR analysis showed that MDP^E6 expressed osteoblast-phenotype related genes, such as bone sialoprotein, osteocalcin or osterix. However, expression of odontoblast marker genes such as dentin sialoprotein(DSP)and dentin matrix protein 1 was not observed in this condition. These data suggest that MDP^E6 did not induce the expression of DSP by osteogenic differentiation medium. The odontoblast differentiation potential of MDP^E6 was assessed by treatment with bFGF. As a result, MDP^E6 showed an odontoblast-like phenotype that showed a prolonged columnar structure and induced the expression of DSP. DSP expression levels were found to increase by 3-fold over the levels in plate cultures without bFGF. Our results suggest that MDP^E6 possesses odontoblast progenitors that can differentiate into odontoblasts by bFGF signaling. Thus, MDP^E6 provides a useful cell culture system for investigating the molecular mechanisms of odontogenesis.

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A number of studies have suggested that green tea has antibacterial and anticariogenic properties, with such properties generally having been attributed to the inherent catechin and fluoride present within tea leaves, both in vitro and in vivo. The aim of this experiment was to determine the effect of fluoride, derived from partially refined green tea extract (PF-4; fluoride concentration was 3,900μg/g), on the demineralization of enamel and dentin in vitro and further, to discuss its efficacy as a means of caries prevention. Demineralizing acid buffers containing 0.01, 0.05, 0.1, 0.2, 0.4, and 0.8 weight percent of PF-4, and 0.4 ppm F and 4.0 ppm F as NaF, were prepared. Finely polished bovine enamel and dentin blocks with windows were immersed in these demineralizing buffers for four days at 37℃. The mineral profiles, integrated mineral loss(IML) and lesion depth(Ld) were analyzed by transversal microradiography(TMR). Lesion formations on the enamel and dentin of the buffers containing low concentrations of PF-4 were characterized by a surface layer of relatively thick but low mineral volume and a less demineralized body of lesions, when compared with the lesions formed by the same amounts of the buffers containing fluoride (NaF). The IML of both enamel and dentin showed a gradual preventive effect against demineralization as PF-4 concentration increased. Enamel lesions formed with the PF-4 buffer showed a decrease in IML and Ld, while dentin showed decreased IML, but unchanged Ld with a commensurate increase in PF-4 concentration. These findings typify the demineralizing traits of buffers containing PF-4 and are thought to be caused by the development of diffusion barriers, which were formed by tea-derived organic substrates and amino acids, and aluminum and several metallic ions binding to the apatitic surface of tooth substrates. In conclusion, this in vitro study demonstrated that the anti-demineralizing effect of PF-4 is most likely characterized by decreasing demineralization of the body of lesions. It also suggested that low concentrations of PF-4 appear to nlav a more effective role in this than NaF.

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Diamine silver fluoride (Saforide®) is used clinically to prevent the progress of dental caries and desensitize hypersensitive teeth. Unfortunately, diamine silver fluoride stains teeth black due to silver precipitation; therefore, it is mainly applied to deciduous teeth. To overcome this drawback, ammonium hexafluorosilicate(SiF:(NH_4)_2SiF_6)was prepared. Silica was employed instead of silver because it does not change the color of teeth, and is well known to induce apatite formation from simulated body fluids. The purpose of this study was to evaluate the occluding ability and duration of dentin tubule occlusion after SiF treatment in a simulated oral environment. The occluding ability of SiF was evaluated using human dentin disks. The surface of dentin disks was observed with a scanning electron microscope (SEM)immediately after SiF treatment and 7 days after immersion in synthetic saliva. SEM observation showed that open dentin tubules were occluded completely with silica-calcium phosphate precipitate immediately after SiF treatment. In addition, newly formed crystals covered the dentin surface 7 days after immersion in synthetic saliva. EDXA analysis showed that the precipitate formed in the dentin tubules after SiF treatment contains silica, calcium and phosphorous indicating silica-calcium phosphate complex. The Ca/P molar ratio of the precipitate formed with SiF treatment was 2.02, and the value gradually decreased after immersion in synthetic saliva. In contrast, the Ca/P molar ratio of newly formed crystals at the dentin surface showed a relatively constant value(Ca/P=1.16-1.28)throughout the experimental period. It seems that calcium-deficient apatite may be precipitated at the dentin surface due to the Ca/P ratio being significantly lower than that of intertubular dentin. SiF treatment induced calcium phosphate precipitation from synthetic saliva; therefore, it has a continuous effect on dentin tubule occlusion under a simulated oral environment.

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The purpose of this study was to examine the microstructure and elemental analysis of surface reaction type pre-reacted glass-ionomer (S-PRG) filler. Composite resins filled with S-PRG filler particles, multifunctional (MF) glass filler and raw material multifunctional (RMF) glass filler were used. Each specimen was observed under a scanning electron microscope (SEM) and analyzed with an energy dispersive X-ray micro analyzer. In addition, the microstructure of each specimen was observed under a transmission electron microscope (TEM). In all specimens, the TEM images showed low electron density spherules inside the fillers. However, a low electron density layer was observed only in S-PRG fillers. These findings suggested that the filler surface had been altered by the reaction of S-PRG. The SEM images illustrated no difference among the specimens. According to elemental analysis, there was no difference among the fillers;elements such as Al, Si, Sr were found to be the main constituents of S-PRG filler and B, O, C, F, Na were also found in low concentrations. The evolution of S-PRG filler could be identified with the examination carried out in this study.

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Extracted human teeth have been used for teaching composite restoration procedures in dental schools, however, it is becoming difficult to procure extracted human teeth. The purpose of this study was to evaluate the bond strengths to artificial enamel and dentin of the resin composite adhesive systems:AQ Bond Plus (AQ), Clearfil Mega Bond and Single Bond. Artificial teeth were mounted in self-curing acrylic resins and facial surfaces were wet-ground with #600 SiC paper. Enamel and dentin surfaces were treated with each adhesive system. Shear bond strength was measured after storage in water for 5 min or 24 h at a cross-head speed of 1.0mm/min. Enamel bond strengths ranged from 8.2 to 12.9 MPa for the group of 5 min and from 8.9 to 17.9 MPa for the group of 24 h. Dentin bond strengths ranged from 7.1 to 14.0 MPa for the group of 5 min and from 7.5 to 19.8 MPa for the group of 24 h. There was no significant difference between the 5 min and 24 h group for AQ. From the results of this in vitro study, artificial teeth could be used as a substitute for extracted human teeth.

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It is well known that tongue coating is the main cause of halitosis. Tongue coating consists of desquamative epithelial cells, leukocytes, saburra and bacteria. Mechanical tongue cleaning is used for treating physiologiohalitosis, and practitioners should always instruct their patients on how to brush their tongues to prevent harmful effects. The objective of this study was to compare a Dentalpro® tongue brush (2.5 mil filament) with commercially available tongue brushes and two experimentally designed tongue brushes (4 mil and 6 mil filament) for controlling the tongue brushing force. Thirty three subjects were instructed on how to use the three kinds of tongue brushes and brushed their tongue stained with Red-coat® thoroughly in their regular customary manner using a brushing force measuring apparatus. The results were analyzed using ANOVA/Scheffe's test and paired comparison t-test (p<0.05). As a result, the mean brushing force for the 2.5, 4.0 and 6.0 mil tongue brush groups were 61.3±39.7g, 56.8±50.0g and 49.3±20.7g respectively. The experimental tongue brush reduced the tongue brushing force compared with the Dentalpro® tongue brush, however, there was no statistically significant difference among the brushing force of the three tongue brushes. The force in the stained tongue group was 88.8±59.2g, and in the no-stained tongue group was 56.7±43.6g. The brushing force in the stained tongue group was statistically significantly higher than in the no-stained tongue group. This result suggested that brushing the tongue coating increased the tongue brushing force.

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Ultrasonic imaging is used in many fields as a non-invasive technique and offers considerable potential in diagnosis as well as serving as a tool for research. Ultrasonic devices for examining soft tissue, particularly in the abdominal region, the brain and the eye, have been available in medical fields. The purpose of this study was to ultrasonically determine the flaws inside the resin-dentin interface by using a phased array system. A standard cavity (φ4×2mm) was prepared on the labial surfaces of bovine incisors with a diamond point. Adhesives were applied and resin composites were filled into the cavity with or without internal flaws. The phased array system used in this study was OmniScan^MX®(RD Tech); an array probe was put on the restoratives and scanning was done in AS mode. Using the phased array method, flaws existing inside the dentin-resin interface could be detected. The results of this study suggest that the phased array system could be used for analyzing qualitatively the status of the resin-dentin interface.

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Purpose: This study examined the relationship between tooth abnormalities and chemotherapy in children with neuroblastoma. Materials and methods: We performed oral examination and orthopantomography in 11 children(7 boys and 4 girls) before or after chemotherapy. They were diagnosed as having progressed neuroblastoma and were treated with chemotherapy in the pediatric department of a university hospital, Kyoto Prefectural University of Medicine. Results: As a result, chemotherapy was started between 2 months old and 5 years and 3 months old. In 7 patients that continued chemotherapy until they were 2 years old, tooth abnormalities were detected in the first premolar, second premolar, lateral incisor and second molar on orthopantomography examination. The tooth abnormalities occurred between the period of chemotherapy and tooth embryonic formation and calcification. Conclusion: We concluded that chemotherapy is associated with the formation of tooth germ defects.

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The objective of root canal filling is tight sealing of the root canal and apical region to protect the periapical tissue from exogenous stimulation via the root canal, and to semipermanently preserve the tooth. The current major method of root canal filling is physical sealing, but deterioration of root canal filling materials may cause apical periodontitis. Thus, it may be better to seal the apex by hard tissue formation in the apical region. However, it is not clear whether the hard tissue formed completely seals the apical root canal and protects the region from infection. In this study, we experimentally induced hard tissue formation in the apical region using biological materials, TBC and α-TCP then reopened the root canal, and histopathologically investigated whether the apical region was completely sealed, and whether the new hard tissue served as a protective wall against infection. No invasion of inflammatory cells was noted 12 months after sealing using TBC and α-TCP. The apical region was tightly sealed with new hard tissue, and re-opening of the root canal did not cause inflammation in the periapical region. The importance of sealing of the apical region with hard tissue was suggested. The newly formed hard tissue served as a protective barrier against infection.

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Porphyromonas gingivalis, a Gram-negative anaerobe, has been identified as an important periodontal pathogen. Gingipains from P. gingivalis play a major role in not only bacterial housekeeping but also inactivation of host defenses. In this study, we investigated the effect of anti-P. gingivalis egg yolk antibody against gingipains (IgY-GP) in human volunteers for 8 weeks. IgY-GP administration did not cause a significant change in clinical parameters. However, P. gingivalis levels in saliva were significantly decreased. Further studies are needed to clarify the usefulness of IgY-GP and the clinical application for periodontal disease.

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The decontamination of implant surface is critical to suppress inflammation of soft tissue surrounding an implant or to obtain re-osseointegration in patients with peri-implantitis. An appropriate decontamination method, however, has yet to be defined. The purpose of this study was to evaluate the most effective decontamination method using a hydroxyapatite (HA)-blasted acid-bathed titanium plate contaminated with periodonto-pathic bacteria in vitro. Actinobacillus actinomycetemcomitans (A. a) Y4 was cultured on stationary titanium plates aerobically at 37℃ for 4 hours. After bacterial adhesion, they were decontaminated each with saline (control), 0.1% chlorhexidine (CHX), etched by 35% phosphoric acid gel (Etch), washed by electrolysis soft oxidized water (EO), high-pressure water (WA), and sodium bicarbonate powder abrasive with high-pressure water (PA). Then, the surface structure and degree of bacterial attachment were observed using a scanning electron microscope (SEM). Quantitative and qualitative elemental analyses were carried out using an electron probe microanalyzer (EPMA). From SEM observation, the PA group was the most effective at removing A. a from the implant surface. In contrast, the control and Etch groups had no effect. The examination by EPMA showed that PA, EO, and CHX groups had notable effects in decontamination, while the control and Etch groups did not. Furthermore, the PA method was the most effective in decontamination, though its profile of the surface was planarizedas compared to that of the control group on SEM observation. In contrast, the WA group had an undetectably insensibly low effect compared with the PA group, but the surface was not changed. We suggest that WA is the most effective decontamination method, and that the protocol from this study is appropriate for evaluating the decontamination procedure.

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The purpose of this study was to investigate the effect of bleaching agent with titanium dioxide and lowconcentration hydrogen peroxide in terms of tooth color and roughness of the enamel surface. Pyrenees® (Mitsubishi Gas Chemical Company) and Shofu Hi-Lite™ (Shofu) were used as bleaching agents. A powerful standard halogen lamp, Hyperlightel (Kuraray Medical), was used as a light source for the experiment. The bleaching agents were applied on bovine enamel. The tooth color was measured with a spectral color-difference meter for micro-surface, VSS300H (Nippon Denshoku), and evaluated with the CIE L*a*b* color system. A handysurf E-30A (Tokyo Seimitsu) was used for measuring the roughness of the enamel surface (Ra) after each treatment. Twenty bovine crowns were assigned to two groups: group P was bleached with Pyrenees, and group H was bleached with Hi-Lite. The ΔE*ab was 3.38 on average with group P and was 3.65 on average with group H. The post-treatment L* levels in groups P and H were significantly higher than the pre-treatment levels. a* levels in the two groups gradually increased, but there was no significant difference compared with the pre-treatment levels. The post-treatment b* levels in the two groups were significantly lower than the pre-treatment levels. There was no significant difference among the two groups. The post-treatment Ra in the two groups showed no significant difference compared with the pre-treatment levels. From the results of this study, it was suggested that Pyrenees could develop the same effects as Hi-Lite.

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It is generally agreed that complete cleaning of the root canal is of crucial importance for the successful outcome of endodontic therapy. The aim of this study was to investigate the antibacterial effects of the Er:YAG laser on experimentally infected root canals in vitro. Root dentin of bovine incisors was used for this study. After the pulp tissue was removed, samples were inoculated with a suspension of Enterococcus faecalis for 5 days, and subsequently Er:YAG laser equipped with a cone-shaped tip (diameter:135μm) was irradiated at a power of 30, 50, and 70 mJ. The disinfecting efficacy was evaluated using light and transmission electron microscopes. Bacteria stained with Gram staining were seen in the dentinal tubules at the mean depth of 500μm after 5 days of incubation. Light microscopic investigation revealed plate-shaped defects that increased with the amount of energy applied. Immediately adjacent to the defect surface, some bacteria were seen. Ultrastructurally, these bacteria appeared to maintain their typical shapes. These results suggest that the antibacterial effects of Er:YAG laser predominantly depend on the action of tissue ablation. It seems to be difficult to eliminate all bacteria that exist deep in the root dentin.

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Enamel matrix derivative (EMD) has been used during periodontal surgery for the regeneration of periodontal tissues. It is known that periodontal flap operation with Emdogain® Gel (Emd®-Gel), mainly composed of EMD, shows early healing and less inflammation compared to open flap debridement alone. One reason for this is thought to be that EMD has antimicrobial activity, however, the antimicrobial effect of EMD has not been clearly evaluated, because EMD is composed of multiple proteins such as amelogenin (AMEL), enamelin, seathlin and proteases. Especially, AMEL, which consists mainly of EMD (more than 90%), exists as an assembly of various molecular masses. The purpose of this study was to evaluate the antimicrobial effects of AMEL on oral microorganisms. EMD was extracted from the tooth germs of immature enamel in porcine fresh mandible. Twenty-five kDa porcine AMEL and its derivatives (20kDa, 13kDa and 6kDa) were purified by Sephadex G-100 gel filtration. Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans and Candida albicans were used for the antimicrobial test. Emd®-Gel, PGA, AMEL fractions and histatin 5 were used as test solutions. Each test solution was added to a calibrated suspension of microbes, and antimicrobial effects were examined based on the calculated number of colony forming units on an agar medium. Emd®-Gel showed antimicrobial effects on all microorganisms, and PGA also showed a strong antimicrobial effect on periodontal disease-related bacteria, but not on C. albicans. An antimicrobial action against P. gingivalis was found in 25kDa, 20kDa and 6kDa AMEL fractions of 250μg/ml, but the activities were low. Antimicrobial effect of AMEL was not found on P. intermedia and A. actinomycetemcomitans. Therefore, the antimicrobial effects of Emd®-Gel on periodontal disease-related bacteria seem to be due to the PGA. Meanwhile, all AMEL fractions showed a strong antimicrobial effect of concentration dependence on C. albicans. Antimicrobial effects of Emd®-Gel on C. albicans seem to be mainly caused by AMEL. However, it is possible that enamelin and seathlin may have antimicrobial effects, because EMD is composed of these proteins other than AMEL. Further studies are needed to elucidate the property of AMEL and other proteins in EMD to develop antimicrobial peptide and examine the availability of clinical application.

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Since Ishikawa et al. introduced Vitapex® (Neo Dental Chemical Products Co., Ltd. Japan) in 1977, the material has been widely used in pulpectomized and infected root canal treatment. In this paper, we show that Vitapex® may have a high degree of absorbability from the obturated root canal. The patient was a 47-year-old female who had received infected root canal therapy by another dental practitioner. Three upper anterior teeth with large periapical cyst-like lesions (radiolucencies) had been followed by extrusive canal obturation with Vitapex® into the periapical rarefactions (lesions). The teeth were asymptomatic and there was no postoperative discomfort for 3 months after root canal filling. Radiographic examination revealed that the overfilled sealer (paste) showed a well demarcated or radiopaque mass just after the obturation, then gradually diffused and was absorbed, and that the paste radiopacity disappeared approximately 4 months later from part of the canal of a tooth. The diagnosis in the endodontic retreatment of the upper left central incisor was acute suppurative apical periodontitis with a large buccal swelling. Clinical and radiographic recalls after retreatment of the root canal by using the laminated root canal filling with FR-Ca paste had been done for 20 years. Endodontic retreatment of the involved tooth resulted in successful resolution and healing of periapical cystic lesions 20 years later. In this case, radiographs showed radiolucent lesions at apices of some lower incisors. The lesions were distinguished from infectious inflammatory lesions because the pulp appeared vital and the teeth were intact without any history of trauma. Periapical cemental dysplasia appeared to be a very likely possibility in this case. These teeth were followed for 20 years and no evidence of pulp involvement was clinically or radiographically evident.

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