Shika gakuho. Dental science reports最新文献

Changes in the salivary glands, liver and pancreas in rats with experimentally induced liver injuries were examined. The injuries (experimental group) were induced by subcutaneous injections of carbon tetrachloride (0.01ml/kg body weight) in a 50% olive-oil solution. The injections were administered twice weekly for 10,20 and 40 weeks. Control animals received the same doses of olive oil during the same periods. 1. In the experimental group, serum glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) increased remarkably, whereas serum albumin decreased. 2. Swelling of the liver and multiple nodular formations occurred in the experimental group. Liver fibrosis with the formation of pseudolobules indicated a form of liver cirrhosis. 3. No significant histological changes were observed in the pancreases of animals in the 10- and 20-week experimental groups. Vacuolation in the acinar cells was observable in 3 of 8 cases in the 40-week experimental group. 4. In connection with histological findings of parotid glands, vacuolation of the acinar cells occurred in 7 of 12 cases in the 10-week experimental group, in 7 of 8 cases in the 20-week experimental group, and in all 8 cases in the 40-week experimental group. Vacuole numbers and sizes increased as the experimental period was prolonged. 5. Immunohistochemical investigation showed strong positive reactions to the anti-amylase antibody around vacuoles in acinar cells of parotid glands. In unvacuolated acinar cells, on the other hand, only slight positive reaction was observed. 6. Electronmicroscopic observation of the acini revealed greatly enlarged lumina and dilated intercellular canaliculi connected to the lumina. Small vacuoles were observed on the basement of the acini. 7. No such significant changes as fibrosis, vacuolation, and atrophy of acinar cells were observed in the submandibular and sublingual glands of the experimental animals. 8. Serum amylase activity increased more in the experimental than in the control rats. Electrophoretic patterns suggested that in the control group 95 percent of serum amylase was parotid type, and also in the experimental group 95 percent of serum amylase was parotid type. 9. Amylase activity in the parotid glands also increased more in the experimental than in the control animals.

Morphological observation of the roots of 2,164 lower first Japanese molars of known sex and side attributes, obtained from the collection of the Okamto Research Laboratory of Dentistry, produced the following results. 1. Roots varied from single to quadruple, but double roots were most common (70.6% in males and 83.4% in females). Next most frequent were triple roots 28.6% in males, 15.75% in females). Single-root was 0.7% in males, 1.1% in females. 2. Quadruple root occurred in only 1, male case (0.04% of the total). 3. Apical ramification occurred in 19.0% of all roots in the double-root category; 16.2% were ramifications on the mesial side only. In triple-root teeth, the ratio was higher: 21.9% for mesial roots. 4. Double-root teeth demonstrated 3 types of form of root apex pointed, rounded, and flat. These types were subdivided into 8 categories. The pointed type was most common (18.9% of the total) for both mesial and distal roots. 5. Orientation and curvature in doubler-root teeth (mesial and distal) were of 2 types. The separated type (Type I), in which the mesial and distal roots separate on the apical side, was most common (96.6% in males, 95.3% in females). 6. In triple-root teeth, size, orientation, and curvature of distal-lingual roots diversified into 8 types. Type V, in which lengths were about 2/3 that of the buccal root, size about half, and general curvature in the buccal-distal cheek plane with general straightness in the mesial-distal plane, was most common, accounting for 40.9% of the males and 47.0% of the females. 7. In double-root teeth, ramification degree between mesial and distal roots was 20.97 degrees in males and 18.97 degrees in females. In triple-root teeth the corresponding angles were 21.33 degrees in males and 18.98 degrees in females. In both cases, the angle was larger in male specimens. 8. In double-root teeth, root length was 12.75 mm in males and 12.41mm in females; root-trunk length was 3.22mm for males and 3.42mm in females. Differences between the sexes were significant in both cases. The root-trunk-length index was 25.24 for males and 27.56 for females, and the ratio of the length of root trunk to the root was 1/4. In triple-root teeth, root length was 12.66mm for males and 12.28mm for females; root-trunk length was 2.99mm for males and 3.21mm for females. The distal-lingual root length in triple-root teeth was 11.48mm in males and 11.10mm in females.(ABSTRACT TRUNCATED AT 400 WORDS)

In permanent teeth described as having incompleted roots, dentin is still in the process of deposition on internal dentin walls and the root is in the process of completion. The purpose of this study of dog's immature permanent teeth was to investigate pulp healing and continuous root and internal dentin-wall developments after direct pulp capping with two types of calcium hydroxide paste on mechanically exposed pulp. Material and methods In this study, 148 vital permanent premolars with incompletely formed apices were obtained from 26 dogs (6 months old). The animals were generally anesthetized with 5% sodium pentobarbital, and a cavity was prepared on the occlusal surface of each experimental tooth using an air turban handpiece with diamond bur. After the cavity preparation, the central pulp horn of each tooth was mechanically exposed with a sterile round bur (ISO No. 007, 2/0). In experimental teeth on the right side, a calcium hydroxide-iodoform paste "Calvital" was applied on the exposed pulp, in experimental teeth on the left side, the exposed pulp was capped with a hard-setting calcium hydroxide paste "Dycal". The cavities were lined with first a zinc-oxide eugenol cement and then a zinc-phosphate cement. Then the cavities were filled with silver amalgam. The dogs were sacrificed by means of sodium pentobarbital at intervals of 3, 7, 14, 28, and 56 days after direct pulp capping. Their jaws and teeth were removed, fixed with formalin, and 100 cases out of 148 teeth with bones from 20 dogs were decalcified, and embedded in celloidin. Each specimen was serially sectioned, stained with hematoxylin-eosin, thionin-picric acid and van Gieson's stain, and evaluated microscopically. In order to identify postoperative dentin formation, intravenous injections of tetracycline were administered to the remaining 6 dogs (48 teeth) at various intervals after the experimental procedure. Two dogs were sacrificed each of the experimental periods. Specimens were embedded in resin and sectioned to a thickness of 50 microns. Undecalcified ground sections were observed by contact microradiography, and tetracycline labeling was evaluated by ultraviolet light. Results and Conclusion 1. Pathological evaluations of the 2 groups "Calvital" group: 49 (98.0%) of 50 cases were evaluated as good, and 1 case (2.0%) as moderately good. "Dycal" group: 31 (62.0%) of 50 cases were evaluated as good, 15 (30.0%) as moderately good, and 4 (8.0%) as bad.(ABSTRACT TRUNCATED AT 400 WORDS)

In this study, the purpose of which is to examine reinforcement of free enamel, we employed visible light-cured adhesive composite resins applied to the inner surface of free enamel and the enamel surface. An Autograph DCS-5000 was used to measure physical tensile shearing strength; a scanning electron microscope (SEM) was used to observe the fracture surface of the adhesive area between the enamel and the composite resin. Results 1. Adhesive strength on the inner surface of free enamel was about 20% lower than that of the enamel surface. Nonetheless, we judged the inner surface of free enamel to have adhesive strength. 2. SEM observation showed that breaking occurred at the boundary of the adhesive surface between the enamel and the bonding material. It is possible to expect a certain amount of reinforcement of free enamel from the use of composite resins.

The objective of this study is to find correlation between erythrocyte-membrane osmotic resistance and periodontal changes. The hepatic function, chemical blood findings, and gingival changes including color, flow of gingival fluid, and local histological changes were studied in rats that had been treated with carbon tetrachloride. Results 1. Rats treated with carbon tetrachloride showed such changes in internal conditions as the following: mild inflammatory alterations, tendency to anemia, severe liver-cell injury, and liver dysfunction. 2. These changes affected the findings of erythrocyte-membrane osmotic resistance and the CPC hemolysis curve pattern. Both the hemolysis maximum point and the hemolysis end point were in the hypotonic side in the group treated with carbon tetrachloride. The maximum point of the CPC hemolysis curve pattern was also in the hypotonic side and not in the middle. 3. In male rats treated with carbon tetrachloride, while erythrocyte-membrane osmotic resistance was changing, round cells infiltrated into the tunica propria next to the epithelium in interdental papillae. Proliferation of the junctional epithelium in the direction of the root apex and hypertrophy in the lateral direction were also observed. These findings indicate mild inflammatory changes in the gingival tissues of the group that had been treated with carbon tetrachloride. Changes in internal conditions of rats treated with carbon tetrachloride affected alterations of erythrocyte-membrane osmotic resistance. Concurrent with these changes, slight inflammatory alterations occurred in the periodontal tissue.

Many studies have been made of pulpal reactions to pulp protection (lining) materials have always employed a smear layer between the dentin wall and the lining materials. In this study, the author has attempted to evaluate pulpal response without a smear layer and compared effects of pulp protection (lining) with and without smear layers. Materials and methods. The experiment employed 84 vital human teeth ranging in age from 14 to 54 years. The experimental teeth were divided into 4 groups for the purposes of histopathological studies and scanning electron microscope (SEM) observation. Group C: No EDTA-treatment and lining with gutta-percha temporary material, 10 cases for histopathological study and 4 cases for SEM observation. Group TC: EDTA-treatment and lining with gutta-percha temporary material, 10 cases for histopathological study and 4 cases for SEM observation. Group P: No EDTA-treatment and lining with Protect Cement. 20 cases for histopathological study and 8 cases for SEM observation. Group TP: EDTA-treatment and lining with Protect Cement. 20 cases for histopathological study and 8 cases for SEM observation. After local anesthesia, Black's simple class I cavities were made in the experimental teeth with a diamond instrument mounted on a high-speed air turbine at room temperature with a water spray coolant. In Groups TC and TP only, an aqueous solution of 0.5% EDTA (pH 7.4) 10 ml was applied from cavity floor to dentin for 60 seconds. All cavities were then washed with distilled water, and the dentin was dried with an air stream. The floor of cavities were lined with thin layers of the following materials: Group C and TC, gutta-percha temporary material (G-C Dental Industrial Co., Tokyo, Japan). Group P and TP lining of Protect Cement which is a zinc phosphate cement containing 0.5% paraformaldehyde (Neo Dental Chemical Products, Tokyo, Japan). The restoration of each cavity was then filled with silver amalgam. Experimental teeth were clinically observed for 2 periods: short (about 14 days) and long (about 60 days) after treatment. They were then extracted under local anesthesia and prepared for histopathological study and SEM observation. Results 1. Clinical observations. During the observation period, symptoms occurred as indicated below. Group C: 2 (20%) out of 10 cases Group TC: 3 (30%) out of 10 cases Group P: None out of 20 cases Group TP: 3 (15%) out of 20 cases The only kind of clinical discomfort observed hypersensitivity to cold water. 2. Clinical evaluations Group C: 10 cases (100%) were good.(ABSTRACT TRUNCATED AT 400 WORDS)

In panoramic tomography, redundant shadows of the mandibular ramus overlapping with tomographic images on the opposite side prevent radiological diagnosis. Redundant shadows differ from tomographic images in sharpness, film contrast, and imaging quality. In addition to mismatching of film velocities and X-ray beams, familiar causes of such unsharpness, still another source must be taken into consideration: the influence of varying slit widths. In the past, research has been concentrated on real images defined by McDavid et al.; that is, tomographic images and tomographic blurring images. The present study, however, qualitatively evaluates the unsharpness of redundant shadows of the mandibular ramus, especially with reference to the effects of first-slit width. At the same time, comparisons are made with tomographic images overlapping with redundant shadows of the mandibular ramus region. An orthopantomograph OP5 was employed as the panoramic X-ray apparatus. In the first step of the evaluation, X-ray beam alignments were examined in the horizontal dimension. To evaluate unsharpness of the mandibular ramus, we used regression analysis by the least-squares method and the Nitka method. Horizontal beam alignments and image layers as calculated by McDavid et al. (1985) were applied in setting the aluminum plate. Conclusions 1. In the case of redundant shadows of the mandibular ramus, unsharpness of the posterior margin and the condylar process depends on first-slit width, which is a major influence on imaging quality. 2. Intensity of edge and film contrast exert about equal influences on unsharpness of redundant shadows of the mandibular ramus. Both factors were influenced by the set-up position of the subject. 3. Film contrast exerted a greater influence than edge intensity on unsharpness of overlapped tomographic images. 4. The wider the first-slit width, the greater the indistinct area of redundant shadows of the mandibular ramus and overlapped images. But, for the purposes of diagnosis, maximum slit width is probably between 3 and 5 mm.

This study demonstrates the electrophysiological and morphological characteristics of the nerve fibers and its endings in the cat periodontal ligament. Furthermore, it shows regeneration of periodontal nerves after alveolar segmental osteotomy of two groups: the repositioned group and the group in which the segment was moved. Electrophysiological investigation were made by applying various stimuli to the mandibular canine and recording changes in response from the canine periodontal branch of the inferior alveolar nerve. For the sake of morphological investigations, changes in the nerve fiber and its endings were observed by means of the silver stain and histochemical method. Results 1. Both fast-adapting and slow-adapting responses were obtained from normal cats. Latency was short 0.45 +/- 0.07 msec, and mean conduction velocity was about 30m/sec. Vibratory stimulation demonstrated a 1:1 response from 10Hz to 250Hz, with no decrease in amplitude observed during stimulation. Pressure stimulation caused a small-continuous amplitude. 2. Nerve fibers distributed in the periodontal ligament entered from the bottom, together with the pulpal nerve and through some holes in the lateral wall of the bony socket. Scarcely, nerve fibers relating with those running from the gingiva were observed in the cervical region. 3. Both free nerve endings and encapsulated endings occurred in the periodontal membrane. Most free nerve endings were especially numerous in the apical 2/3 and these types were simple and sharp, though a few of them were bumplike, spindlelike or clublike. These latter types were especially numerous in the cervical 1/3, and especially in the area between the canine and the third incisor. 4. In both groups, it was possible to record nerve action potential 4 weeks after the osteotomy. Mean conduction velocity was 6.16 +/- 0.63 m/sec in the repositioned group and 5.41 +/- 0.15 m/sec in the moved-segment group. Mean conduction velocity recovered rapidly 6 weeks after osteotomy to reach 15.85 +/- 1.81 m/sec in the repositioned group and 13.71 +/- 1.91 m/sec in the moved-segment group. Thereafter increase was gradual; 48 weeks after osteotomy, the values were 21.60 m/sec for the repositioned group and 20.00 m/sec for the moved-segment group. Regeneration rates were 71.3% for the repositioned group and 66.0% for the moved-segment group. 5. In both group, fast-adapting responses had recovered 4 weeks after the osteotomy; and slow-adapting responses were clearly recorded 6 weeks after the osteotomy.(ABSTRACT TRUNCATED AT 400 WORDS)

Many studies have made on the physiological significance of the periodontium in relation to oral functions. But, although its importance to oral functions has been pointed out, few investigations have been carried out on the periodontal pressoreceptive information system. To help rectify this situation, as a link in investigations of soft-food textures, the author attempted to determine how a sense of pressure was perceived when loads gradually increasing from very small were applied to the tooth surface. In addition, the author attempted to clarify the way the periodontium discerns differences between initial and secondary loadings in a range of small loads between the touch sensation and the pressure sensation. Subjects were 10 males with sound, natural dentition and no disorders in mandibular functions. In order to eliminate intervention from pressoreceptors in the masticatory muscles and the mandibular joints, the upper first premolar was chosen as the test tooth. Small loads were applied in 2 directions: parallel to the first premolar vertical axis (vertical) and from the lingual to the buccal sides parallel to the occlusal plane (horizontal). For vertical loading, the mesial pit on the occlusal surface was chosen as the loading point. The middle point on the lingual surface was chosen as loading point for horizontal loading. First, loading on the tooth surface was gradually increased to obtain (1) threshold value for touch sensation; that is, minimal load required to incite a touch sensation, and (2) critical value for pressure sensation; that is, minimal load required to incite the pressure sensation subsequent to the touch sensation. Each subject was requested to press a hand switch in the moment he experienced the sensation of being touched and then again when, during increases of load, the touch sensation changed to the pressure sensation. The loading device was built into an electric strain gauge. Loads were increased gradually from 0 g to 60 g, with an increase ratio of about 10 g/sec. Loading wave and switching signal were simultaneously recorded on an oscillograph. Second, in order to determine the ability to discriminate small loads, with the same loading device, initial load was applied to the tooth. This load served as control. As soon as the load was sensed, it was removed. Then the secondary (testing) load was applied. Subjects were requested to say whether the secondary load was larger, smaller than or same as the initial one.(ABSTRACT TRUNCATED AT 400 WORDS)