This investigation was designed to determine how hemodynamic changes would be characteristically evoked in inflamed dental pulp to painful tooth stimulation. The inflamed dental pulp was experimentally induced by cavity preparation in maxillary canines (n=6) in 18-month-old Beagle dogs. Pulpal blood flow (PBF) was continuously monitored by means of laser Doppler flowmetry before, during and after electrical tooth stimulation. Electrical stimulation was conducted for 5 minutes on the enamel surface or the cavity by means of a clinical electrical tooth stimulator. In addition, histopathological changes in the dental pulp following the cavity preparation were investigated (n=6). Results obtained were as follows: 1. Electrical stimulation on the enamel surface of the normal teeth (control:non-cavity preparation) caused a significant increase in PBF during stimulation, then PBF immediately regained its initial value after discontinuation of the stimulation. 2. Electrical stimulation on the deep cavity immediately after the cavity preparation induced a significant increase in PBF. After discontinuation of the stimulation, PBF slowly recovered its initial value. 3. Electrical stimulation on the deep cavity 2 weeks after the cavity preparation evoked a temporary increase in PBF, and then PBF remarkably decreased to a lower level than the initial value even during the stimulation. After discontinuation of the stimulation, PBF remained at a lower level and never regained its initial value. 4. Histopathological findings of the dental pulp revealed a more severe hyperemia 2 weeks after cavity preparation than that immediately after preparation. These results suggest that painful stimulation to the inflamed dental pulp might cause circulatory disturbance, resulting in pulp necrosis.

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Objectives: Once enamel is lost, dental pulp is exposed to physical, chemical and bacterial irritants through dentinal tubules. The outward fluid flow (OF) in dentin provides protection by preventing these irritants from entering the pulp via the tubules. We previously reported that lipopolysaccharide (LPS) diffusion was reduced to nearly zero in intact (ID) and demineralized dentin by OF in vitro. However, LPS is found in the tooth pulp beneath the exposed dentin in vivo. In this study, we examined the changes in hydraulic conductance (Lp) and LPS diffusion across dentin underneath early caries (ECD) compared to ID. Materials and Methods: Six ID and 11 ECD discs were prepared from the crown portion of freshly extracted human third molars. Lp of dentin was measured using a horizontally placed split chamber device. Simulation of the pulp interstitial pressure (1.47kPa) was used to produce the OF. Five of 11 ECD discs were discarded because LPS was detected before the experiment. LPS diffusion against OF through ID and ECD was measured and compared to that with non-outward flow (NF)(n=3 for each group) at 0, 1, 4 and 8h. Results: The Lp of ECD was significantly lower than that of ID (independent West, p<0.00l). The results of the amount of diffused LPS, independent of experimental period, in decreasing order are ID-NF, ECD-NF, ECD-OF, ID-OF(two-way ANOVA, p<0.001). OF reduced the diffused LPS to 1/10 in the ECD group and to 1/10⁴-10⁵ in the ID group. These results indicate that OF reduced the LPS diffusion of ID more than that of ECD. LPS was not detected from six of 11 ECD discs, suggesting that LPS entry may not cause reduction of the functional diameter of dentinal tubules. The hydrodynamic movement of the dentinal tubule fluid, which can cause deformation of the odontoblast cell membrane, may have triggered the reduction of the functional diameter of dentinal tubules.Conclusions: Caries is not a simple process of demineralization of hard tissues accompanied with collapse of collagen fibers, but a dynamic change in which tissue destruction and defense and repair mechanisms coexist. A decrease in outward volumetric flow rate caused by the reduced functional diameter of dentinal tubules in the inner dentin may coexist with an increase in diffusion by demineralization in the outer dentin. This breakdown of the protective mechanism is thought to result in LPS entry into the tooth pulp. Until complete obturation of dentinal tubules and/or atubular dentin formation or pulp necrosis occurs, the competition between pulpal defense mechanism and irritation entry will continue.

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The purpose of this study was to evaluate the effect of examination with 3DX on the prognosis of periapical surgery using a dental microscope. Fourty-two teeth without the 3DX examination and 51 teeth with the 3DX examination were treated by retrograde root canal filling using a dental microscope and followed-up radiographically for 6 months. Their state of healing was categorized into 4 groups: complete, incomplete, uncertain and unsatisfactory. Complete and incomplete healings were regarded as successful. The success rate was 79.2% for the non-3DX group and 83.3% for the 3DX group at 6 months postoperatively. The 3DX group showed earlier healing than the non-3DX group (p<0.05). The 3DX examination may be useful for low-invasive periapical surgery.

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Plaque control plays a most important role in the prevention and treatment of periodontal disease. In the present study, the efficacy of a newly developed toothbrush equipped with two kinds of thumb stopper and modified head and handle was compared with a conventional toothbrush especially on the stiffness of brush and the strength of handle as well as the influence on their plaque removal rates. In addition, the plaque removal effect and the feeling of use were also compared between the modified and conventional toothbrushes with the results as described below: 1. The brush stiffness ranged from 2.14 to 2.39N/cm². In the impact test on a toothbrush handle, no cracking was observed for both modified and conventional toothbrushes. 2. No significant difference was observed in the rate of plaque removal due to different degrees of brush stiffness or handle flexibility. 3. The rate of plaque removal for whole teeth was the highest with the modified toothbrush. As for the plaque removal rate by different tooth sites, the modified toothbrush equipped with thumb stoppers as well as the control toothbrush of conventional type showed a higher removal rate in the molar region. In particular, the modified toothbrush showed a higher removal rate in the adjacent surface, lingual side and mandibular molars. 4. According to the result of questionnaire survey, the modified toothbrush revealed to have a higher score as a whole. The modified toothbrush with thumb stoppers had a higher score in the easiness of brushing back teeth. From the results mentioned above, it was suggested that the operative capacity of toothbrush including brushing pressure is improved with the subsequently increased rate of plaque removal even in molar regions where the brushing is generally difficult by equipping the grip with two kinds of thumb stopper. Furthermore, the brush was allowed to reach the molars, lingual side and adjacent surface more easily by making the grip more flexible in the case of modified toothbrush.

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A new tooth bleaching agent (Pyrenees®) containing visible light sensitive TiO₂ and 3.5% H₂O₂ has been developed. It is a safer bleaching agent for oral soft tissue compared with usual ones containing a high concentration of H₂O₂. The purpose of this study was to evaluate the clinical efficacy of the newly developed bleaching agent. The bleaching procedure was applied to 61 volunteer patients once a week for three weeks. The bleaching effect was determined by calculating the color difference with a colorimeter, observing the tooth color with a shade guide (Vitapan 3D-Master®) as a reference, and monitoring the degree of satisfaction of the patients, compared with pre- and post-operation, during the 6-month examination period. Also, the safety of the agent was investigated according to the clinical examination during the bleaching procedure period. In the clinical evaluation, the bleaching effect of Pyrenees® for discolored vital teeth was clearly recognized during the bleaching period, however the postoperative evaluation showed a diminishing tendency. Regarding the satisfaction degree of patients, over 90% answered "very much" or "much". As for the safety, four cases complained of slight pain for a short time immediately after applying the agent, but the pain disappeared quickly. One case showed gingival erosion, but the gingiva recovered after one week. It is concluded that Pyrenees® is a clinically effective and safe bleaching agent for discolored vital teeth.

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Ni-Ti alloy has special properties, such as low elastic modulus, super-elasticity, and shape memory effect, and has been used for endodontic instruments. Recently, many types of Ni-Ti files have been developed and clinically used. They have special features, including cross sectional shapes and tapers. The aim of this study was to evaluate the mechanical properties of a new Ni-Ti file, Liberator®. This file has unique features of no twist on the blade and is used under high rotational speed. In this study .04 and .06 tapered Liberator® files with 0.30 mm diameter tips were selected as specimens, and the same-size specimens of a commercial Ni-Ti instrument, ProFile®, were used for reference. Phase transformation behavior was measured by differential scanning calorimetry(DSC). A cantilever bending test was used to measure the bending load at the point of 1.2mm and 3.0mm deflection in the loading process. A torsional test was performed according to ISO 3630-1, and maximum torque and angular deflection at fracture were measured. The results of the DSC measurement suggested that Liberator® consisted of austenitic phase alloy at intraoral temperature, and the transformation temperature was found to be suitable for applying super-elasticity in the clinical setting. With respect to the mechanical properties, the bending load values of the .06 tapered Liberator® were significantly lower than those of the .06 tapered ProFile®. However, no significant difference was found between those of .04 tapered instruments. The maximum torque values and angular deflection at fracture of Liberator® were significantly lower than those of ProFile®. From the results of the cantilever bending test, it was found that Liberator® had more flexibility than ProFile® in larger-tapered groups. It was considered that the mechanical properties of Liberator® may result from its cross-sectional design as well as the phase transformation behavior of the alloy. However, since the results of the torsional test showed that Liberator® had low resistance against torsional stress, the loading stress during root canal treatment should be carefully controlled to avoid torsional fracture.

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Some saccharides increase intestinal absorption of calcium and prevent bone loss in ovariectomized rats. In the present study, we examined whether disaccharide trehalose (TH) prevents bone loss after menopause in ovariectomized mice, which are used as an animal model of human postmenopausal osteoporosis. ICR female mice were randomly divided into six groups: a Sham group, an OVX group, a 10mg/kg TH group (TH10), a 50mg/kg TH group (TH50), a 100mg/kg TH group (TH100) and an Estradiol group (control group). The mice of OVX, each TH and Estradiol group were ovariectomized at 8 weeks of age, and thereafter given trehalose by oral administration or estradiol was subcutaneously injected 6 times per week for 4 weeks, and the influence on the weight of body and womb, serum components and bone was examined. There was no statistically significant difference between the OVX and TH or estradiol administration groups in the weight of body, and the concentration of Ca and P in serum. Womb weight increased significantly in the Estradiol group compared with the OVX group, but not in the TH group. Dry weight and trabecular bone area of the femur increased significantly in the TH group and the Estradiol group compared with the OVX group. Bone strength of the femur increased significantly in the TH100 group and the Estradiol group compared with the OVX group, while the TH10 group and the TH50 group slightly increased. Lumbar bone mineral density (BMD) increased significantly in the TH10 group, the TH100 group, and the Estradiol group compared with the OVX group, while the TH50 group slightly increased. These findings suggest that trehalose may be effective in the prevention of osteoporosis after menopause, and may improve the bone quality.

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Periodontal surgery requires operators to have specific knowledge and technical skills for surgery. Practice on a simulation model may help improve skills. We have developed a simulation model for periodontal surgery. Operators need suitable advice or instructions from an instructor during simulation training using the model. HTML atlases were made for practice manuals of periodontal surgery. The purpose of the study was to investigate the effect of the HTML atlases using movies during simulation training on achievement and time for practice and instruction. Twenty dentists, 1-3 years after graduation, practiced on the simulation model. Ten operators practiced wedge operation referring to the HTML atlas using the movies (experimental group) and the other ten referred to the HTML atlas using the still pictures (control group). The results were as follows: 1. The degree of achievement was not significant between both groups. 2. The average time for practice of the experimental group was shorter than that of the control group. 3. The average time for instruction by the instructor of the experimental group was shorter than that of the control group. These results suggested that the HTML atlas using movies saves time for instruction of simulation training.

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Various signal molecules including members of the fibroblast growth factor (FGF) family are involved in tooth development. FGF18 is known to regulate cell proliferation and differentiation in osteogenesis and chondrogenesis. Here, we demonstrated a high expression of Fgf18 and its receptors, Fgf receptor (Fgfr) 2,3, in rodent dental pulp tissues. In vitro study revealed the promotional effects of FGF18 on proliferation of both odontoblastic MDPC-23 cells and osteoblastic Kusa-Al cells. Alkaline phosphatase (ALP) activity and mineralized nodule formation were down-regulated in these cells in the presence of FGF18. These results suggest that FGF18 is an important signal molecule for dental pulp tissues. Further studies are necessary to reveal the precise functions of FGF18 in dental pulp tissues.

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Calcium hydroxide is a pulp-capping agent, and has been used as an intracanal medicament. Although it is considered one of the most effective antimicrobial agents in endodontic treatment, little is known about its bactericidal mechanisms in vitro. In order to evaluate the efficacy of calcium hydroxide as an intracanal disinfectant, we examined the bactericidal effects on clinically isolated bacteria. Using the cylinder-plate method, microbial growth inhibition was not observed around the antibiotic cylinder. The broth dilution procedure indicated that the minimal inhibitory concentration of calcium hydroxide was 0.2%. The agar dilution method also indicated weak antimicrobial activity. These results suggest that calcium hydroxide is not an effective microbial agent as an intracanal disinfectant and that its clinical applications should be reconsidered.

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The exact mechanism of periradicular cystogenesis is not well understood. The purpose of this study was to evaluate histopathologically extensive proliferation of epithelial rests of Malassez in the periodontal ligament and initial periradicular cyst formation with central cavity induced by apical overinstrumentation and overfilling. Thirty-two root canals of thirty-two sound permanent teeth (24 upper and lower anterior teeth, and 8 upper premolars) in four crab-eating (Macaca irus) adult monkeys were prepared for this experiment. Pulp extirpation procedures were performed under general and local anesthesia, with a tooth by a rubber dam in all teeth. The root canal length was determined by using an electronic device (Root canal meter, Onuki). The root canals of most teeth were prepared on the apex. The canals were irrigated several times alternately with 6% sodium hypochlorite and 3% hydrogen peroxide. The canal treatment after the pulp extirpation was as follows. Treatment Group 1: canal instrumented at the apex Group 2: canal instrumented and filled short of the apex Group 3: canal instrumented and filled beyond the apex Most canals were filled with lateral condensation of gutta percha points and zinc oxide eugenol sealers (Canals®, Showa Yakuhin Kako). In half of the cases, the teeth were overfilled with sealers about 1 to 2 mm beyond the apex. In some canals, a sterile dry cotton pledget or moistened cotton pledget with PTC was placed. In other canals the dentinal chips were plugged slightly beyond the apex. All the cavities were carefully lined with zinc phosphate cement and then sealed with amalgam. All test teeth were radiographed. After the experimental period from 1 to 4 weeks, the animals were sacrificed. The teeth were fixed in 10% neutral formalin. After decalcification, serial celloisin sections, 10 to 15μm thick, were prepared and stained with hematoxylin-eosin, Schmol stain and Masson Goldner stain for light microscope observation. The results were as follows: 1. Generally, it was found that a periapical inflammatory response occurred in all teeth of the overinstrumented and overfilled groups. 2. Four weeks following completion of the canal fillings, an area of chronic inflammation was noted far beyond the apex. In the periodontal ligament and in the bone marrow around the apex, small masses of proliferated epithelium were present. 3. Initial developmental stage of periradicular cyst was confirmed by 4-week specimens in the group of overfilled canals.

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Neutrophils migrate to the site of a bacterial invasion where they mount a phagocytic defense; however, degranulation of these neutrophils results in tissue destruction. The role of neutrophils has not been defined in terms of the pathology of pulpal inflammation. To evaluate this role, we examined the effect of granulocyte colony stimulating factor (G-CSF) on functions of neutrophils and changes in pulpal tissues after pulpal exposure of normal rats and of those with neutropenia induced by methotrexate. Pulpal inflammation was induced by exposing the pulp in mandibular first molars. The number of neutrophils in peripheral blood and their chemotactic and phagocytic reactions were measured. The changes in pulpal and periapical tissues following the exposure were also examined histologically and bacteriologically. Neutropenia was induced with methotrexate injection once a day for 3 days in some rats before the exposure. G-CSF was injected every day to both normal and neutropenic rats. In untreated rats, G-CSF injection caused an increase in the number of neutrophils and migration of neutrophils, but did not influence the phagocytosis and pulpal inflammation. In rats made neutropenic by methotrexate, the migration of neutrophils and their phagocytosis were inhibited, and the area of pulpal necrosis was enlarged. Bacterial invasion into the necrotic area was detected. When G-CSF was injected into the neutropenic rats, the neutrophil count increased, the inhibition of chemotaxis and phagocytosis was reversed, and the enlargement of the necrotic area was inhibited. These results suggest that neutrophils defend against bacterial invasion in the pulpal tissue.

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