Kanagawa shigaku. The Journal of the Kanagawa Odontological Society最新文献

Thirty 28-day-old male Wistar rats were randomly divided into 5 experimental groups of 6 animals, and fed low-fluoride diet (0.07 ppm F) and drinking water containing fluoride at constant concentration (20 ppm F) ad libitum for 49 days in combination with strontium chloride added to provide 0, 5, 10, 20, 40 ppm Sr. Enamel mottling was observed through over-all experimental period, and at an end of the experiment, all animals were sacrificed. There was no significant difference in weight gain among groups. Enamel mottling of mandibular incisors in Sr groups appeared at 7th day (cumulated fluoride ingested: under 3.0mg), while mottling in control group (0 ppm Sr and 20 ppm F) appeared at 14th day (cumulated fluoride ingested: ca. 6.6 mg). However, severity of mottling was higher in low-strontium group (5 and 10 ppm Sr) than in high-strontium groups (20 and 40 ppm Sr). Data of contents of Sr, F, Ca and P in incisors and femurs obtained through chemical analysis suggested that an exchange of Sr and Ca would take place in apatite and that the exchange reaction of F- and OH- could be urged by Sr. Further, data of serum F level demonstrated that the fluoride retention in serum could be urged by lower level of strontium rather than higher one.

The various methods were introduced in the daily prosthodontic field evaluating occlusal contacts for diagnosis and analysis. Maness in 1987 developed the T-Scan system, which is considered as a new computerized device capable to interpret occlusal contacts information quantitatively. The system is composed of a sensor, sensor frame, handle, cable and system unit. Record and analysis mode made possible the occlusal contacts in three ways, such as the balance plot, the time display and comparison screen. However, accuracy and reproducibility of occlusal marking through this system is still uncertain. Therefore, this preliminary study was conducted on four specific points loaded on a sensor by application of the weight of 0.1 kg through 10 kg. The following results were obtained 1. There exists certain non-sensible areas caused by its constructional feature. 2. The most sensible area can be measured from 0.1 Kg to 2.1 Kg, and therefore, this device is more suitable for recording within lower loadings. 3. Although the system has a certain disadvantage of reproducibility, this contributes to attain diagnosis and treatment of occlusal contacts for a quantitative evaluation.

The authors used a human dry skull on which the cranial bone mandible had been joined with an artificial articulator disk to form a single unit. Impact acceleration corresponding to weak and strong tapping was considered a dynamic load in examining the vibration transfer characteristics of the facial cranial bone when impact was applied from the mentum section in a situation designed to be closer to reality. Flexion injection type (resonance frequency f0 = 100 to 150 Hz, produced by GC Corp.) was applied to the human dry skull as an artificial periodontal membrane at thickness of 0.3 mm. In addition, Exaflex heavy body type (f0 = 400 Hz, produced by GC Corp.) was applied as an artificial disk. This was then placed on a damper produced by spreading a rubber dam sheet with a thickness of 35 microns on a tire tube with a diameter of 35 cm and an air pressure of 35 kg/cm2. Investigations were then made concerning linearity and reciprocity to determine whether an experimental system could be achieved or not. This was then followed by modal analysis. As a result, the following matters were ascertained: (1) The resonating area differed according to the extent of the force. (2) An increase in the viscoelastic elements of the silicon was accompanied by attenuation of force. (3) Directionality of force attenuation was caused by the complexity of bone structure. (4) A tapping force of 0.3G or 1G was sufficiently attenuated by the facial cranial bone. (5) The transfer function at the bone seams and thinner areas of the bones was insufficient for modal analysis of the facial region and total cranial bone of the human dry skull.

The primary etiological agent of all periapical lesions has long been considered to be bacterial. Furthermore, bacteria from infected root canals are potential antigens capable of initiating immunological reactions in periapical tissues. The purpose of this study, therefore, was clarify the immunological potentials of Veillonella parvula (V. parvula), which was frequently isolated from root canals with periapical lesion. Immunobiological activities of V. parvula sonic extracts were investigated on the enhancement of monocytes migration, induction of interleukin-1 (IL-1) production, mitogenicity and polyclonal activation of B cell. Following results were obtained: 1. Both LPS and protein of V. parvula sonic extracts strongly enhanced the activity of human peripheral monocytes migration. 2. Induction of IL-1 on C3H/HeN mice macrophage by V. parvula sonic extracts were stronger than that of S. typhimurium LPS as positive control. 3. It was found that mitogenicity of LPS from V. parvula on splenocytes was stronger than that of the protein, however mitogenicity on thymocytes was not shown in both preparation. 4. The polyclonal activation of B cell on splenocytes of BALB/c nu/nu mice by V. parvula was induced by the protein and LPS. 5. These findings indicate that both the protein and LPS from V. parvula have a regulation of immunobiological responses against macrophages and lymphocytes.

The purpose of the present study was to clarify wound healing process of periodontal tissue following experimental flap surgery, when applied the guided tissue regeneration (GTR) technique using a cross-linked atelocollagen membrane (AM). Mucoperiosteal flaps were made on the palatal gingiva of maxillary first molars of rats. The cementum was removed by curettage in order to expose the dentin surface. An AM was implanted into the site of dissection in the experimental group, while the control group received no implantation. The resorption processes of AM and wound healing processes of exposed root surface in the experimental group were examined by electron microscopic observation, 1, 3, 5, 7, 14 and 21 days, and 2, 3 months after the implantation. While the wound healing processes of periodontal tissue in the control group were examined at the fine structural level, 2 and 3 months after the flap surgery. The results were as follows. At the resorption processes of AM, the early invasion of a large number of neutrophils appeared in the site of of implantation. Neutrophils were attracted to and adhered to the AM fibers over the first few days after. AM was resolved to fine fibrous structure by the neutrophils between 1 and 3 days. A large number of macrophages appeared in the implanted site between 3 and 7 days, and neutrophils subsided after 5 days. The implanted material was rapidly resolved be macrophages with active phagocytosis, sometimes forming giant cells. Fibroblasts were invading to peripheral gingival connective tissue and were development of microfilament were observed. The implanted materials were completely resolved after 14 days. In light microscopical findings, of the experimental group, epithelial downgrowth was markedly inhibited, fibrous bundles of the gingival connective tissue were clearly arranged vertical to the root surface and new cementum tissue deposited to the root surface after 21 days. At electron microscopic observation in early stage of healing, dens granular layer (d. g. l.) was presented to the dentin surface. After 2 or 3 months of the control group, high density fibrous layer increased to the root surface. Connective tissue fiber bundles were paralleled to the root surface. The above results indicate that the GTR technique using an atelocollagen membrane may provide an effective method to promote periodontal tissue regeneration after periodontal surgery.

The principal means of preventing dental caries in Japan are dietary control and tooth-brushing. However, these measures in public health have not been conducive to a definite reduction of dental caries, while the use of fluorides has led to a remarkable and rapid decrease in caries prevalence. Fluoride mouth-rinsing are usually incorporated into the school-based programs. Many trials were carried out in the elementary schools and a 30-50% reduction in caries increment was reported. To provide greater benefits to the permanent teeth, therefore, it is suggested that fluoride mouth-rinsing should be started earlier in the age. However, fluoride mouth-rinsing is not recommended generally for preschool children who cannot rinse out their mouths well. Among the solutions for mouth-rinsing, there are some different types in the fluoride used, the fluoride content and the frequency of application. The most commonly used fluoride mouth-rinsing solution for daily use is 0.05-0.1% NaF in neutral or weak acid solution. The present study was conducted to confirm the fluoride mouth-rinsing with a lower content of fluoride solution would have an additional cariostatic effect if it is started at the age of four. Participants rinsed with a weak acid (pH 5.0) NaF solution (100 ppm F) for 30 seconds 5 times a week. After all, they were received benefits from fluoride before eruption of the permanent teeth. In the present study, it was demonstrated that the effect of dental caries inhibition was greater than those in the previous study. Especially, many lower first molars were free from dental caries. After 7 years, the caries reduction rates were about 48% in DMFT and 54% in DMFS respectively. So far as 4 first molars, the caries reduction rate was about 41% in DMFT, and this figure was almost the same as all DMFT. It was recommended that the fluoride mouth-rinsing program with a lower fluoride content solution should be started at the age of four.

The bone-resorbing action of lipopolysaccharides (LPS) in vitro has unknown mechanism of action. In order to evaluate the effect of LPS on rat calvaria and the influence of LPS on the bone-resorbing activity of macrophages, the following experiments were conducted. The addition of macrophages 10(6)/ml to a culture system composed of rat calvaria increased calcium release from the cultured bone. Addition of macrophages 10(6)/ml preincubated with 10(-2) mg/ml LPS caused a more pronounced release of calcium from the cultured bone. Combined use of Indomethacin, a prostaglandin synthesis inhibitor, with macrophages and macrophages preincubated with LPS inhibited calcium release, suggesting a possible participation of prostaglandins in osteoclast mediated bone resorption.