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Home  > Department of Pulp Biology and Endodontics  > The aim of research

The aim of research

1) The immune defense system in periapical tissue and dental pulp

The immune system in pulp
We have studied the immune defense system in the pulp tissue. It has been shown that macrophages and dendritic cells are already in normal pulp tissue, surveillance systems have been built against the penetration of exogenous disturbance of dentinal tubules, furthermore it is revealed that NK cells also present in normal pulp. In other words, there is a possiblity is of that against foreign invasion to some extent, pulp tissue can respond adequately, to achieve the integrity of the pulp tissue by controlling a foreign invasion quantitatively. In addition, the cavity preparation by the experimental stimulus, dendritic cells in the cavity beneath lost once, to come emerged again revealed. Dendritic cells, it reacts rapidly with respect to foreign invasion, and rapid migration to lymph nodes, activation of acquired immunity in the unit, indicating a dynamic and re-invasion of the pulp local further been shown. Further, the TLR4 is expressed in pulp dendritic cells were also revealed.

Possibility of pulpitis control due to the suppression and the role of nitric oxide in pulpitis
From the fact that the number of macrophages with the progress of pulpitis, containing nitric oxide synthase is increased revealed immunohistologically, I was administered inhibitor specific for this enzyme. As a result, the number of inflammatory cells infiltrating the pulp decreased significantly.

Crosstalk of the nervous system and immune system at apical periodontitis
Periapical lesion is characterized by alveolar bone destruction and inflammatory cell infiltration of periapex, but I considered the possibility that the nervous system is involved in this process. As a result, consistent with the infiltration of MHC Class II cells, nervous system and blanching actively than extensive stage of periapical lesion, a large number of nerve was observed in the lesion. Moreover, activation of the CD86-positive DC was also observed at the periphery of the lesion expansion phase. Intimate contact with the nerve was also observed with (MHC Class II-positive cells mainly) inflammatory cells.

2) The dendritic cells at apical periodontitis
Dendritic cells cells present in periapical periodontitis, that it is composed of dendritic cells cells of many different cell surface expression of antigens and forms became clear from experiments using immune electron microscopy.

3) Function of fibroblasts in tumor angiogenesis
As the function of fibroblasts in tumor angiogenesis, the supply of nutrients to the tumor cells is considered mainly. However, as a result of co-culturing tumor cells and fibroblasts of different gene expression, that a change in gene expression in fibroblasts alter the expression of genes in tumor cells was strongly suggested. Further the change in the gene expression is also involved in tumor cell proliferation has been suggested.

4) Study of root canal preparation using Ni-Ti files

the intensity of an electric current flowing through the DC motor such Denta port root canal formation using the Ni-Ti file is proportional to the stresses applied to the file roughly. Result was examined in detail the intensity of the torque is measured with the current value, that there is potential for the development of safer auto reverse torque mechanism is revealed. Based on these results, it is continuing the research towards the development of more effective torque auto reverse mechanism.

5)Studies on the Improvement of Electrical root canal length measuring instrument

For improvement of root canal length measuring instrument, we are going to use computer simulation for measuring the electrical characteristics of the root canal by impedance analyzer. It was found that for that express accurately the frequency characteristics of the root canal in the equivalent circuit in series or parallel which consists of one capacitor and one traditional resistance is impossible, more complex equivalent circuits are required . It is also ongoing research and whether including an electrically diagnosis of root fractures, the discovery of the root canal opening.

6)Studies on the distortion of root canal wall dentin

While the root canal filling or preparation, it can cause root fracture by large distortion in the root canal wall dentin unexpectedly. Under such conditions the weighted stress repeatedly in a short time, that can reach 0.2-0.3% distortion amount of total accumulated strain occurs is revealed. In addition, root canal filling, I added the analysis also distortion of dentin of reverse root canal filling and preparation at the time by the ultrasonic vibration or laser. Currently, in order to understand the relationship between the intensity of the distortion and occurrence of microcracks, which is being prepared so as to the studies using the micro-focus-CT.

7)Application of the drug in endodontic treatment

Improvement of endodontic treatment, for the purpose of control of pain and inflammation, I have to verify the application of the drug in endodontic treatment. The main cause of endodontic disease is a bacterial infection of multiple, Toll-like receptor for sensing components of bacteria, immunohistochemistry the distribution of CD14 and TLR4 is a receptor of Lipopolysaccharide of Gram-negative bacteria, particularly It was found that it examined by, pulp within and is expressed in trigeminal ganglia. In the future, we plan to examine in detail with reference to the rat trigeminal ganglia primarily, relationship with other receptors, the effect of the presence or absence of inflammation.

​​8)Studies on the laser application to endodontic treatment

①By considering the transmittance of the laser beam through a dental microscope and protective goggles, it should be discussed that the safety of using Nd: YAG, Er:YAG, semiconductor laser of transmitting energy , these groups were compared as the reference maximum permissible exposure for the eye of each laser (MPE). In the present experimental conditions, when the use of laser under the microscope, I was considered 0, transmission energy is safe to use when wearing special protective glasses.
②By processing the tip of the light guide fiber for the Nd:YAG laser, and a conical tip shape was subjected to laser irradiation on the dentin in combination of titanium oxide solution. Dentin is cut by laser irradiation, the possibility of application to form a root canal has been suggested. To allow irradiation of the side by processing the tip of the light guide fiber for the Nd:YAG laser, the possibility of laser irradiation on the root canal wall was suggested. In the future, I repeat examination application to such as sterilization and disinfection of the root canal.
③ Er:YAG laser is possible to cut the dentin without causing little stress and the minimum thermal effect. I have examined the intensity of the distortion of dentin caused to retrograde root canal preparation using ultrasonic scaler and Er:YAG laser. Considered stress on the dentin of retrograde root canal preparation, time is small compared to ultrasonic scaler, and be expected removal of smear layer. Er: YAG laser is useful by using at the retrograde root canal preparation.

9) The electrophysiological studies on Dentin / Pulp Complex and toothache

①By using a dual patch clamp method, We revealed that etedrial conductance is an information of transmission system via a gap-junction and ion channels odontoblasts membranes. I made it clear physical elasticity of the film itself further.
②Vascular endothelial cells and vascular smooth muscle has a coupling electrical, and showed that performs information transmission by the cell-cell contact than the control by the nerve. I made it clear effect on the vasoconstriction of calcium hydroxide.
③You searched electrophysiologically and chronic inflammation aging is what influence the relationship between the sense of the subject and the activity of the nerve fibers have been recorded in microneurogram.
④In addition to search over time the changes in the activity of rat masticatory muscles when was induced experimental pulpitis, were searched for involvement in the modulation of this muscle activity of the endogenous opioid system. Muscle activity increases in pulpitis caused when, was attenuated after that, it was re-increased by antagonist of opioid receptor. This evoked activity decreased with increasing weeks of age.
⑤We confirmed the possibility to search for changes in neuronal activity in the rat central nervous system Experimental pulpitis onset, modulation of the activity thereof has occurred through the NMDA receptor. Further, the involvement of central suppression mechanism in via endogenous opioids has also been suggested.
⑥It was found that delivery to the pulp of the drug via the dentinal tubules using high concentration drug pressure towards the pulp side and iontophoresis can be promoted.
⑦Clearly how the cellular components of dentinal tubules in-directly under, the addition of lime monster is, or affect the permeability of the material to the pulp side against the flow of outward dentinal tubules in solution of demineralized dentin was.

10) Diagnosis of fracture of vertical root of using the (3DX) small radiation field CT
Diagnosis of fracture of vertical root is difficult, it is tooth extraction in many cases. The depth of the periodontal pockets or around roots transmitted image oral findings, the dental X-rays is an important clue has been reported for diagnosis. However, since it is similar to periodontal disease or periapical lesion, it is often difficult to obtain a definitive diagnosis is transmitted image findings.
In this study, we examine the possibility of diagnosis of fracture of vertical root using (3DX, Morita) a small radiation field CT. It has a high resolution of voxel size 0.125mm cube, 3DX can shoot 3-D high-definition image of the cylindrical imaging area diameter 40mm, 30mm of height. Further, three-dimensional image can be observed from the XYZ direction any site. Effective dose in the 0.006-0.014 mSv 1 time per shot, which is a radiation dose equivalent to almost the panoramic X-ray and (dental shooting) intraoral X-ray imaging.
In patients who visited the University Dental Hospital outpatient dental caries, to perform the 3DX shooting as subjects patients to schedule resection apical or tooth extraction as a treatment has a transmission image to dental X-ray photo. Based on the information that was taken, endodontic dental and medical radiologists to evaluate the form of X-ray transmission image and the presence or absence of fracture. I do a treatment based on the diagnosis then, were changed by the 3DX shooting or the original diagnosis. I do a resection apical tooth extraction diagnosis if a root fracture, if apical periodontitis. The definitive diagnosis with the diagnosis, and compared with the diagnosis by 3DX image. In addition, the presence or absence of image fracture in 3DX, for the spread of the transmission image, compare whether there is a difference in its typical pattern in tooth fracture and non-folding tooth fracture, and confirm with only diagnostic imaging preoperative by 3DX Consider Is it possible to obtain a diagnosis.
Frontier Molecular Destruction and Reconstruction of Tooth and Bone): (21st Century COE Program molecule tooth bone science of

11) pulp maintenance (global center of excellence program, international research center for molecular Science in tooth and bone disease)
①Elucidation of the characteristics of pulp mesenchymal cells
It has been and is undifferentiated mesenchymal cells of neural crest-derived dental pulp cells forming the subject of the pulp tissue, and have the ability to differentiate into odontoblasts which form dentin is a hard tissue specific teeth , the details are still unknown. For FGF18 expressing pulp tissue-specific, we analyzed the functions and the expression kinetics. Among the whole body, then the brain, the lungs, FGF18, was highly expressed in the pulp tissue. In addition, it appears that FGF receptors of all types are expressed in pulp tissue, FGF18 is functioning through the receptor of these FGF18. In FGF18KO mouse, tooth germ is formed, but the growth is inhibited, the size of the molars and incisors was smaller obviously. In addition, in cultured cells, FGF18 was strongly promoted the proliferation, calcification worked in the direction of inhibition. For more information about the features of FGF18, as well as promote further studies, we would like to consider the possibility of its clinical application.

② Elucidation of the mechanism of differentiation ameloblast
In the generation of the tooth, it has been reported that the signal network from both mesenchymal and epithelial tissues and has an important meaning. In particular, is considered enamel hat and plays a role as a signal center, I have to control the differentiation of odontoblasts and ameloblasts. Sonic hedgehog (Shh) is a signaling molecule typical produced in enamel hat, thereby controlling the differentiation of epithelial cells through Patched its receptor. This time, we experimented using ameloblasts strain ALC, were observed rise enamel matrix expressed by Shh. In addition, expression of enamel matrix is ​​also promoted by forced expression of Gli1 is an important transcriptional regulator of Shh signal, and their expression was inhibited by RNAi and Gli1 specific to reverse. Amelogenin expression nitrite and Melo Brass Tin was confirmed in transplantation experiments in mice subcutaneously. Specifically, Shh signaling is an important factor for inducing differentiation ameloblasts, it appeared that signal to induce enamel matrix protein expression directly through Gli1.

③Elucidation of the characteristics of odontoblast
Odontoblast is a hard tissue-forming cells characteristic in the tooth, Dentin Sialoprotein is odontoblast marker and only specific, (osteoblasts also produced in trace amounts). The odontoblast, to differentiate received signals from epithelial cells from dental papilla cells in the development process, but the differentiation from pulp cells is induced after the odontoblast is lost on an outpatient invasive, such as in dental pulp of mature that. However, details of the differentiation mechanism is still unknown. As well as to clarify the mechanism of differentiation into odontoblasts from pulp cells and dental papilla cells, to promote the study on the characteristics of the odontoblast is a hard tissue-forming cells and tooth-specific.