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インプラント材としてのチタンの機械的性質 : 純度による影響
Get PDFapplication/pdfCommercially available titanium materials are classified on a standard scale form 1 to 4. The standard is based on the amount of Oxygen, Nitrogen, and Iron contained in the titanium. Recently, implant material made of type 4 titanium, has been marketed. This study compares several mechanical properties including tensile strength, elongation, yield strength, energy to break and hardness between type 2 and type 4. The followings conclusions were obtained: The tensile strength, yield strength, and energy to break of type 4 are higher than those of type 2. Elongation of type 4 is less than that of type 2. Hardness of type 2 is than that of type 4. Overall evaluations of mechanical properties indicate that pure titanium type 4 is superior to type 2 as an implant material.journal articl
睡眠時ブラキシズムの病態生理 : 最近の見解
Get PDFapplication/pdfSleep bruxism (SB) is considered to be a clinically relevant problem for dentists but a definitive understanding of its pathophysiology is lacking. In dental studies, various physiological backgrounds, especially sleep, have been often overlooked. Recent physiological studies revealed that SB is associated primarily with sleep-related periodic fluctuations in autonomic, cortical and motor activity. To adopt a more comprehensive perspective of SB pathophysiology in clinical dentistry, integrated physiological studies in both humans and animals are required.journal articl
ヒト乳歯の吸収と脱落
Get PDFapplication/pdfThe resorption and shedding of the human deciduous teeth are physiological processes associated with the replacement of permanent teeth. Numerous studies have been reported the tissue changes which occur during physiological root resorption of the human deciduous teeth, however, to date, the precise mechanism of this resorptive process is not fully understood. Especially, there is little information about how root resorption is initiated, and how the final shedding of tooth is regulated. In this review, firstly, we introduce the phenomenon of the odontoclastic resorption at the pulpal surface of coronal dentin prior to the shedding of human deciduous teeth. Secondly, the cytodifferentiation of human odontoclasts is described with special attention has been paid to the morphology and function. We also demonstrate cellular/extracellular events during the tooth resorption-repair process in this internal resorption. Finally, a possible mechanism of exfoliation of human deciduous teeth is discussed.journal articl
骨代謝における骨芽細胞と破骨細胞の細胞連関
Get PDFapplication/pdfBone is an actively metabolized tissue. Bone volume is maintained through a balance of bone formation by osteoblasts and bone resorption by osteoclasts. Recent research demon-strated that receptor activator of NF-kB (RANK)-RANK ligand (RANKL) mechanism plays a pivotal role in the differentiating and activating osteoclasts. Osteoblast-lineage cells, consisting of osteoblasts, osteocytes and bone lining cells, regulate bone resorption via the expression of RANKL. The balance of RANKL and OPG, a decoy receptor for RANKL, is thought to regulate the bone remodeling. Thus, bone remodeling is accomplished by the harmonized interaction between osteoblast-lineage cells and osteoclasts. RANK-RANKL mechanism is also engaged in pathological bone resorption such as periodontal diseases. New approach based on the interaction between osteoblasts and osteoclasts will be neces-sary to prevent and treat bone diseases.journal articl
大脳皮質および大脳基底核の咀嚼運動制御における機能的意義
Get PDFapplication/pdfIt has been known that masticatory movement, especially during chewing, is controlled by the brain stem. However, as mastication is a sequential action from food intake to swallowing, the higher brain such as the cerebral cortex and basal ganglia is thought to be needed for the control of the masticatory sequence. In the cerebral cortex, the cortical masticatory area (CMA), to which the repetitive electrical stimulation induces the rhythmical jaw movements like masticatory movements, may be involved in the control of mastication. Based on jaw movement patterns, the CMA is divided into two parts. One is the part of the CMA in which a T-pattern similar to jaw movements during food-transport (initial stage) in natural mastication is evoked by electrical stimulation. The other part of the CMA is more dorso-medially located, and a C-pattern similar to jaw movements during chewing can be induced. The CMA is suggested to play an important role in the initiation and/or performance of masticatory movement. In the striatum, which is the input area of the basal ganglia, the ventral part of the putamen receives the input from the CMA. Furthermore, the input from the T-pattern inducing CMA is broader than that from the C-pattern inducing CMA. Neurons in the ventral part of the putamen change their firing frequency during mastication depending on the masticatory sequence, not on the masticatory cycles. Most of them alter their activities during the initial stage. From these findings, it is suggested that the cerebral cortex and basal ganglia are significant in the control of complex functions during the initial stage, and in making the masticatory sequence smooth.journal articl
日本の歯科医師数,歯科診療所数および歯科診療医療費に関する1検討 : マクロ的視点からの分析
Get PDFapplication/pdfIn the 47 years between 1955 and 2002, the number of dentists in Japan grew by 2.98 times, and the number per 100,000 people grew by 2.09 times. By the classification of business, the composition rate of employees in dental clinics and hospital dental schools has been on the increase. Since 1984 there has been no relationship between the increase in the number of dentists and the intake capacities of dental schools, so some other factor has been working to increase the proportion of dentists. In 2002, the number of dental clinics in Japan was 2.0 times the number in 1975 in real numbers, and also 1.87 times larger per 100,000 people. In the same year the number of dental clinics ranged from 83.8 per 100,000 people in the Tokyo metropolitan area to 33.1 in Fukui Prefecture; this distribution is remarkably unequal, considering the fact that the mean number of dental clinics over the whole country was 51.1 per 100,000 people. Private clinics accounted for 87.5% of all facilities. Dental expenses in 2002 were 22.8 times those in 1965. However, dental expenses as a proportion of people's medical expenses had decreased, from 10.7% in 1980 to 8.4% in 2002. Expenditures on dental services peaked in the 45- to 64- age group, although there was also a peak in the group aged 65 years and over, as there was for general medical expenses. On the other hand, there was a peak in per person dental expenses for age 65 and older, the same as in general medical expenses. Analysis of the relationship between dental expenses and the number of dentists engaged in medical treatment suggested a possibility that the increase in the number of dentists as a supply factor was related to the increase in dental expenses.journal articl
実験動物用マイクロCTを用いたrhBMP-2・アテロコラーゲンゲルによるウサギの顎骨欠損部再建の経時的観察
Get PDFapplication/pdfA rabbit experimental mandibular defect was reconstructed with rhBMP-2 and atelocollagen gel, and examined using μCT (R_mCT, Rigaku mechatronics, Tokyo) in vivo and histological techniques. Using eight rabbits, we made an experimental mandibular defect and filled it with 1% atelocollagen gel including rhBMP-2 10μg (Astellas Pharma Inc.). In μCT observation, the density was slightly elevated at the bone marrow side at day 5, and the phenomenon gradually expanded during the course of this experiment. Histologically, mesenchymal cell proliferation and immature bone formation occurred at one week, and mature bone gradually increased and filled in at four weeks. The histological data suggests that atelocollagen gel is effective as carrier of rhBMP-2. The μCT observation is extremely useful for follow-up of such reconstruction of animal bone defect model.journal articl