Matsumoto Dental University Repository
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コンポジットレジンの曲げ強さにおけるサーマルサイクルの影響
Get PDFapplication/pdfPossible changes in material's characteristics of six types of commercially available composite resins have been investigated in an intraoral enviroment. After samples were subjected to the thermocycling treatment for 1000, 3000 and 10,000 cycles between 4℃ and 60℃, the bend strength and fracture strain were measured. At the same time, same mechanical properties of tested samples were evaluated after they were immersed in 37℃ distilled water for equivalent time to the above mentioned thermocylcing duration. Fractographic observations were also conducted on fractured surface of bend strength tests. Main conclusions are as follows; 1. Thermocycled samples showed lower values of bend strength and fracture strain, as compared to control samples. 2. Bend strengths of sample groups SD and UN which were immersed in 37℃ distilled water exhibited higher values than those of control group. Other sample groups showed an increase or decrease in bend strengths. 3. Strain amount of sample group CF which was immersed into distilled water increased. Other sample groups exhibited either an increase or decrease. 4. It was clearly observed that mechanical properties of composite resins are influenced by the intraoral temperature. 5. Among tested sample groups, it was found that SD sample group was the least sensitive to thermal effect in its mechanical characteristics; while CF sample group exhibited the most sensitivity to external thermal effects.journal articl
上顎左側第三大臼歯と臼後歯との双生歯の1例について
Get PDFapplication/pdfA case of a fused tooth, involving the left maxillary third molar and the supernumerary tooth, found in a 22-year-old male patient was examined. This supernumerary tooth had 6 cusps and one root. Its root was fused with the root of the third molar on the distal side. 3 DX^[○!R] images and Soft X-ray photographs indicated that both the third molar and the supernumerary tooth also partially shared the same cavity. This fused supernumerary tooth was identified as the distomolar, the so-called fourth molar.journal articl
チタンと歯科用貴金属合金のレーザー溶接に関する研究
Get PDFapplication/pdfLaser welding has been reported as a promising welding technique for joining titanium materials. However, since it is anticipated that titanium prostheses will become more popular in the near future, dissimilar-material laser welding of titanium materials should be evaluated and investigated. When titanium materials are fusion-welded to dissimilar materials, several problems mayoccur, including corrosion of the weldment and elemental-dissolution from the weldment, possibly causing deterioration of the original excellent properties of titanium materials. Furthermore, since laser welding for dissimilar joining with titanium materials has not been well established, poor penetration might take place. In the present study, the feasibility of laser welding of titanium materials to dental precious alloys was investigated. The study included bending strength, strain, hardness and elemental-dissolution of the dissimilar joints. The following results were obtained. 1. Bend strengths of similar weldments were lower than those obtained with base materials, except TI. 2. Distortion of similar weldments showed lower values than base materials. 3. Similar weldments of TI-TI exhibited a higher value of hardness, while other similar weldments showed lower hardness values than those obtained for base materials. 4. Dissimilar weldments of titanium showed lower bending strength and strain than did base materials. 5. Dissimilar Titanium weldments showed greater hardness than those obtained from the base materials. 6. SEM fractography of dissimilar joints revealed many porosities which appeared to be created during the welding procedure. Moreover, fractured surfaces indicated the presence of brittle materials at the dissimilar titanium joints. 7. The dissolution amount of Ti from dissimilar titanium joints in 1% lactic acid aqueous solution exhibited a higher value than that detected from base materials. 8. There were no statistically significant differences in bending strength before and after immersion in 1% lactic acid aqueous solution in both similar and dissimilar titanium joints. 9. Only TI-PT joints exhibited a lower value of strain after immersion in 1% lactic acid aqueous solution than the strain before the immersion.journal articl
咬合力と顎顔磯形態との関連性 : 簡易型咬合力計を用いて
Get PDFapplication/pdfIt is very important for orthodontists to understand the relationship between bite force (function) and facial pattern (morphology) with regard to orthodontic prognosis. Much research related to bite force has already been conducted in the dental field. A simple method, however, for measuring occlusal force has not been reported. We have utilized a handy type of occlusal force meter for orthodontic patients, and the data we obtained by the occlusal force meter was very helpful in judging the prognosis of the patient. The purpose of this research was to investigate the relationship between the maximum bite force measured by a handy type bite force meter and the skeletal pattern. Forty-four male adults were selected for this research to measure the maximum bite force, and their cephalometrics were also analyzed. A fairy strong correlation was found between the maximum bite force and both the mandibular plane angle (r=-0.425), and the facial angle (r=0.483). On the other hand, a weak correlation was found between the force and the occlusal plane (r=-0.321) as well as the gonial angle (r=-0.239).journal articl
陶材焼付け強度に及ぼす金属材料の前処理の影響
Get PDFapplication/pdfCurrently, Ni-Cr alloy as a substrate for porcelain-fused metal has been shifted to Co-Cr alloy and precious metal alloys in China. In this study, effects of various pre-treatments done on Ni-Cr alloy, Co-Cr alloy and precious metal alloy on porcelain bond strengths were investigated. Three surface treatments were tested, including sand-blasting, rough-surface polishing, and de-gassing treatment. Mirror-finish polishing was a control surface condition for this study. Dental porcelain was fired to three differently treated surfaces of three alloys. The porcelain bond strengths were evaluated by three-point bend flexural tests. Sample size was 6 (n=6). The followings are main results and conclusions. 1. The Ni-Cr alloy was not influenced by surface treatments on its porcelain bond strength. 2. Porcelain bond strength with precious metal alloys exhibited lower values and was adversely influenced by surface treatments. 3. With precious metal alloys, it is recommended to generate a larger surface roughness, so that sufficient mechanical retention force can be achieved.journal articl
Dandy-Walker症候群患者の全身麻酔経験
Get PDFapplication/pdfDandy-Walker syndrome is characterized by perfect or partial defect of the cerebellum vermis and cystic dilatation of the posterior fossa communicating with the fourth ventricle. We used general anesthesia for comprehensive dental treatment in a case with this syndrome who had a ventriculo-peritoneal (VP) shunt. The patient was a 3-year-old boy diagnosed with Dandy-Walker syndrome at 5 months after birth. A VP shunt was inserted into the lateral ventricle and the cyst on the posterior fossa at 10 months. After the VP shunt operation, there were no symptoms of cerebellum dysfunction or increased intracranial pressure. A diazepam suppository (6mg) was administered 90 minutes before the start of anesthesia. After the establishment of a venous route, anesthesia was induced with thiopental sodium (100mg) and nasotracheal intubation was facilitated with vecuronium bromide (2.5mg). Ventilation with a face mask and laryngoscopy were performed without difficulty. Anesthesia was maintained with oxygen (2l/min), nitrous oxide (4l/min) and sevoflurane (1～2%). Prostheses after pulpectomy in 4 teeth and composite resin filling in 4 teeth were performed and the anesthesia was over uneventfully after 3 hours and 35 minutes. There were no postoperative complications such as vomiting, disturbance of consciousness and ataxy. There are several problems with the management of this syndrome, such as avoidance of embedded shunt-valve dysfunction by magnetic fields such as in MRI exposure, and by external force, choice of anesthetic that has less effect on cerebral pressure, and maintenance of adequate respiratory condition during operation and postoperative period.journal articl
矯正用固定源に用いたインプラント周囲骨組織と歯の移動効果
Get PDFapplication/pdfThe purpose of present study was to determine the anchorage potential of mini-titanium implant for orthodontic tooth movement in two Beagle dogs. Extracted upper and lower second premolar to maintain the orthodontic mesial tooth movement of third premolar. Sixteen mini-titanium implants (1.0 x 5.0mm; eight loaded and eight control) were placed bilaterally in healed upper and lower jaw bone. After twelve weeks, orthodontic device was applied to upper and lower canine, third and fourth premolars. Third premolars were retracted mesialy on 200g of continuous force for entire sixteen weeks by Ni-Ti closed coilspring that were placed between mini-titanium implant and third premolar. Fluorochrome bone labels (Tetracycline, Calcein blue, Alizarine red and Xylene orange) were injected during orthodontic force application to determine the remodeling at bone-implant interface and effect of tooth movement. Bone contact, remodeling at surrounding bone-implant interface and environment of non-movement and movement tooth were observed by back scattered electron micro images (BSE), electron prove micro analyzer (EPMA), laser scanning micro images (LSM) and light micro scope images. The result of our study showed upper and lower third premolars were bodily moved mesialy 3.5mm on the average and non-loaded control tooth were remain in the force system without any anchorage. Bone contact at surrounding bone-implant interface maintained rigid osseointegration. Slight active bone remodeling was observed at surrounding bone-implant interface during orthodontic force application than non retracted control implant. We concluded that the mini-titanium implants successfully resisted the orthodontic load and could be maintain the tooth movement or remain in orthodontic force system.journal articl