Shika gakuho. Dental science reports最新文献

The purpose of this study is to determine the fluoride contents of shrimp and of tea samples obtained from Shizuoka prefecture which is famous for tea products area and fishery market and to examine the relations between fluoride and other mineral contents, such as calcium, magunesium and phosphorus. Fluoride contents in tea produced in this area have been reported by Matsuura and Kokubu and other investigators, but more recent data are scarce. Samples were taken from a kind of shrimp known as Sakura-shrimp and from 4 kinds of commercial tea (coarse tea, 2 kinds of green tea and refined green tea). After having been dried and powdered, 1g of each sample was reduced to ashes at 550 degrees C for 10 hours with Ca(OH)2 as a fluoride fixative. Fluoride was distilled from each ash sample at about 140 degrees C with HClO4, and about 200 ml of distillate was collected from each sample. Fluoride contents were determined by means of ion-specific electrode. Calcium and magnesium contents were determined by atomic absorption spectrophotometry, and phosphorus contents were determined by Chen, Toribara and Warner's method. Total fluoride contents of the samples were as follows: 61.73ppm in shrimp, 180.16ppm in coarse tea, 72.62ppm and 89.02ppm in the 2 kinds of green tea, and 71.11ppm in refined green tea. More than 99% of the total fluoride was obtained from 150ml distillate of each sample. Calcium contents were extremely high in shrimp (21,822ppm) and 2,106-2,693ppm in tea samples. Magnesium contents were highest in shrimp (3,088ppm) and lowest in coarse tea (1,333ppm).(ABSTRACT TRUNCATED AT 250 WORDS)

Cementing manipulation is an important final step in adapting crown prosthesis to various oral environments. Preventing elevation of full cast crowns during cementation and improving adaptability of the margin after cementation are especially critical. The purpose of this article is twofold: 1) To clarify the relationship between the viscosity of dental cement and the extent of crown elevation, with special attention to viscosity changes occurring in various cement materials during the hardening process. 2) To study the effects on cemented-crown elevation of the space created between the abutment tooth and the crown, which may be partly related to dental cement behavior during cementation. A total of 4 cement materials was used: Elite Cement 100 as a zinc-phosphate cement, Super Bond C & B and Chemiace as MMA-resin cements containing 4-META, and Panavia EX as a phosphoricester cement. Viscosity was measured by means of MR-3 Soliquidmeter with a cone and plate system (Reheology Engineering). A brass material was processed to experimental crowns cemented to abutment teeth of brass. Crown elevation was measured by comparator (Measurescope Model II, Nikon). In addition, effects of the resistance of dental cement during cementation on crown elevation were studied for the sake of a comprehensive understanding of the elevation phenomenon. 1. Changes in dental-cement viscosity during the hardening process 1) Elite Cement 100 demonstrated the highest initial steady flow coefficient of viscosity. It was followed by Super Bond C & B, Chemiace, and Panavia EX, in that order. The t-test revealed significant differences among these cement materials (significance taken to be 1%). 2) As experimental temperature increased, the viscosity of all tested cement materials increased with progressive hardening. 3) With the passing of time, changes in torque, which represents a change pattern in viscosity, indicated that the tested cement materials have different viscosity-change patterns during the initial setting period. 4) From a clinical viewpoint, Super Bond C & B and Elite Cement 100 had very limited working time, whereas Chemiace and Panavia EX had relatively long working time. 2. Elevation after cementation of experimental crowns 1) For Elite Cement 100, mean elevation was 334microns, for Super Bond C & B 281 microns, for Chemiace 164microns, and for Panavia EX 130microns. The t-test revealed significant differences among these cement materials (significance taken to be 1%). 2) In all the cement materials tested, with a reliability of 99%, sequential correlation was observed between crown elevation and steady flow coefficient of viscosity.(ABSTRACT TRUNCATED AT 400 WORDS)

Subject material for this study was pus collected from patients with purulent inflammation in the oro-maxillary region. Direct gas-liquid chromatography (GLC) analysis was made, bacterial isolation and identification were carried out, and comparisons were made with results from GLC analysis and anaerobic isolates in a PYG medium. In addition, antibiotic susceptibilities of anaerobic bacteria were examined. Results 1. Anaerobic bacteria were isolated from 85 of 100 cases of obstructive abscesses. Of the 85, 49 were cases of mixed infection involving both anaerobic and aerobic bacteria; and 64 cases were involved with more than 2 species of anaerobic bacteria. Of the 184 strains of anaerobic isolates, 53 were Bacteroides sp. and 51 were Peptostreptococcus sp. The 2 groups accounted for more than half of the isolates. 2. Group A, in which no VFA was detected, accounted for 17 out of 100 cases. Group B, in which acetic acid was detected, accounted for 20 cases; and Group C, in which butyric acid was detected, accounted for 20 cases; and Group D, in which iso-valeric acid was detected, accounted for 8 cases. Direct GLC analysis revealed iso-caproic and caproic acids in the 35 cases constituting Group E. 3. Whereas the percentage of anaerobic bacteria was 64.7% in Group A and 60% in Group B, significantly higher percentages were noted in Group C (95%), Group D (100%) and Group E (100%). The following species were isolated as major member in the groups; Group A--Streptococcus intermedius, Group B--Peptostreptococcus micros, Group C--Fusobacterium nucleatum, Group D--Bacteroides gingivalis, and Group E--Peptostreptococcus anaerobius. 4. In all cases, the sum of VFA produced in the PYG medium by anaerobic isolates was classified into Group A' to E'. Ratios of agreement between VFA as revealed by direct GLC and VFA as revealed by PYG.GLC were as follows: Group A-A'; 47.1%, Group B-B' and C-C'; 45%, Group D-D'; 87.5%, and Group E-E'; 62.9%. 5. In Group B, no propionic acid was detected. The 2 cases in which acetic acid occurred in a concentration greater than 14 x 10(-4) meq/ml belonged to Group B'. In Group C, no isobutyric acid was detected; and the 5 cases in which butyric acid was detected in a concentration of more than 7 x 10(-4) meq/ml belonged to Group C'. Varelic acid was not detected in Group D; and 7 out of the 8 cases in which iso-valeric acid, irrespective of concentration, was detected belonged to Group D'.(ABSTRACT TRUNCATED AT 400 WORDS)

For the purpose of analyzing deformations and movements in the maxilla loaded by orthopedic force to the maxillary first molar, a three dimensional finite element model of the maxilla was constructed. For modelling of the maxilla, the right side of an adult Indian skull was used. Constructed model was composed of 1,108 solid elements and 1,195 nodes. Materials of this model was composed of compact bone, cancellous bone, teeth and sutures. Constraint condition was fixed adjacent bone side surrounded by sutures. Load was directed from upward to downward 30 degree, changing every 30 degree reference to occlusal plane. Volume of load were weighed at 1 kg for each directions. Results 1. At upward load, stress was transmitted through the lateral wall of the maxillary sinus. The posterior portion of the maxilla was displaced more upward than anterior. Each process of the maxilla and the maxillary sinus was deformed, however, there was no stress on the orbitary surface. 2. At upward 60 degree load, the maxilla was compressed simply to the direction of load. At the upward 30 degree load, it was compressed backward-downward and rotated clockwise together with bending. 3. At backward load, the maxilla was moved backward and rotated clockwise. At downward 30 degree load, the maxilla was moved backward-downward and rotated clockwise. Both loads bended anterior portion of the maxilla and compressed posterior portion. The center of rotation or bending fell on the line joining the frontal process and the zygomatic process. 4. Of all five directions, backward load showed the maximum value of displacement and upward showed the minimum. Concerning with the absolute value of principal stress, backward load showed the maximum and upward 60 degree load showed the minimum. 5. Concerning with the principal stress value of sutures, compressive stress were distributed equally at upward load. However, as the load went to downward direction, it caused stress concentration. Especially, compressive stress in the pterygopalatine suture and transverse palatine suture, extensive stress in the midpalatal suture were especially great.

In the previous study (Shikwa Gakuho, 85: 413-451, 1985.), Morinaga reported on the histopathology of furcation perforations treated with ethyl cyanoacrylate and showed that, because of its properties, this material cannot be expected to effect a permanent blockade. It did not, however, irritate the wound. The purpose of this study is to investigate the effects of a new cyanoacrylate cement (FH Cement) when applied to furcation perforations. Subjects were 25 mandibular and maxilla premolars and molars obtained from 3 adult dogs. The method used in the study was as follows. After administration of pentobarbital-sodium general anesthesia, the pulp chamber was opened by means of a high-speed air turbine fitted with a diamond point. According to usual procedures, the pulp was removed, and the main root canal was filled. Next the floor of the pulp chamber was deliberately perforated by means of a 1mm round bur that had been previously sterilized in advance pouring a physiological sodium chloride solution at the same time. The perforated areas were then washed with a same solution, wiped, and dried with aseptic cotton pellets. They were then stuffed with cyanoacrylate cement. The cavity was lined with gutta-percha temporary stopping, and the remainder of the cavity was filled with silver amalgam. At periods of 1, 2, 4, 8 and 12 weeks after the operation, the animals were sacrificed by means of electricity under general anesthesia. The jaw bones were removed, fixed, decalcified, and embedded in celloidin. Longitudinal sections were stained with hematoxylin-eosin. Results 1. Periodontal tissues around perforated sites were healed by means of scar tissue, though suppuration occurred in a few cases. 2. Hard tissue was appended to the teeth in a small number of cases. 3. Repair of the alveolar bone was observed in the damaged site in about half of all cases. From the result mentioned above, cyanoacrylate cement (FH Cement) was seemed to did not close the site perforation for it self, but was not a stimulant to wound, in case of appropriate blockade.

The purpose of this study is to evaluate oral hygiene before and after individual method toothbrushing without instruction and to analyze toothbrushing times for school children from 6 to 13 years of age. Subjects were 150 pupils from primary to junior high school affiliated with the faculty of education of an university located in Setagaya, Tokyo: 38 first-grade pupils aged 6, 36 fourth-grade pupils aged 9, 37 sixth-grade pupils aged 11, and 39 second-year junior high school pupils aged 13. Assessments of dental plaque were made by two dentists using the PHP plaque score (Podshadely and Haley, 1968) for primary school pupils and OHI-S (only DI-S; Greene and Vermillion, 1964) for junior high school pupils. Plaque distribution disclosed by an Erythrosine solution was examined before and after toothbrushing, and the performance of toothbrushing by subjects was recorded on video-tape through a one-way mirror so that the children were unaware. Toothbrushing time was measured by 2 or 3 examiners using a time counter of video-monitor. Average scores for dental plaque before and after toothbrushing were almost the same for first and fourth-grade primary school pupils; but scores decreased with a statistically significant difference (p less than 0.01) for sixth-grade pupils. Distribution patterns of plaque scores for fourth-grade pupils showed characteristically narrow ranges (2-5 before brushing and 1-4 after brushing). The majority of subjects (69.4%) had scores of 2-3 after brushing, Whereas only 8.3% showed a range of 2-3 before brushing.(ABSTRACT TRUNCATED AT 250 WORDS)

In this study, responses of fast-adapting sensory units to ramp-shaped pressure and triangular vibratory stimuli were recorded in the molar lingual gingiva and the alveolar mucosa isolated from the cat mandible via the air-gap method. The receptors of the fast-adapting units were classified into five types by a morphological study and the response characteristics of the individual sensory unit were investigated by electrophysiological methods. 1. Fast-adapting units of cat oral mucosa were found to have had five types of encapsulated endings (Type I-V) via a microscopical study. Among the 1,609 endings observed, the occurrence frequency of the individual receptor type was as follows: Type I 64.1%, Type II 9.5%, Type III 13.9%, Type IV 1.2% and Type V 11.3%. Although Type V a-d receptors had not been observed in the cat oral mucosa, their presence was demonstrated in whole thickness preparation stained with methylene blue. 2. The impulse frequency-displacement velocity curves (long-long coordinated) of 32 fast-adapting units (20 animals) showed four different patterns. 9.3% of the fast-adapting units showed a proportional relationship over all ranges of displacement velocity in the impulse frequency-displacement velocity relation. 25.0% showed a proportional relationship in an initial narrow range of displacement velocity and attained a steady state in the higher range. In 21.9% of these units, the impulse frequency remained steady over all the ranges. In the remaining 43.8%, the impulse frequency remained steady in singular range over all displacement velocities tested, however their response times decreased when the displacement velocity was increased. 3. The fast-adapting units were divided into two groups by response mode: a unit group with a Type I receptor and the other with Type II-V receptors (represented by a Type III receptor). The slopes were measured from their relations (log-log coordinates) in threshold amplitude vs. displacement caused by single triangular stimulus. The slope for the Type I group was -0.796 +/- 0.099 (mean +/- S. D.) (Range: -0.593(-)-1.017, n = 22). The slope for the other group was -0.658 +/- 0.024 (Range: -0.607(-)-0.758, n = 6). The slope of the former was larger than that of the latter. 4. The threshold-frequency curves (tuning curve; semilog coordinates) for the Type I group and the other group were analyzed. Both tuning curves of these sensory units revealed no plateaus between the lower-frequency limits and the upper-frequency limits.(ABSTRACT TRUNCATED AT 250 WORDS)

When, the intercuspal position is newly established during reconstruction of maxillomandibular relationship, understanding the process of adaptation for the laterally shifted eccentric intercuspal position is very significant for problems involving maxillo-mandibular registration and diagnosis of occlusion, which has very important meaning for clarifying the neuromuscular control system for mandibular movement. In this studies, changes in clinical symptoms and masticatory movements were observed longitudinally when the laterally shifted intercuspal positions were newly established. Conditions for selecting four subjects were that they wore suitable overlay maxillary dentures connected to abutment teeth and that their mandibular dentition were natural and included good fixed restoration. Experimentally prepared overlay dentures were identical to those worn by subjects except that they included a structure of lateral shift of artificial dentition positioning to given newly laterally shifted intercuspal position. The condition of lateral shift of the intercuspal positions are established by the protrusion of the condyle on one side, amounts of lateral shift of the intercuspal positions were 0, 0.5, 1 and 2mm. From immediately after until a week after insertion of the experimental denture, observations were made to determine clinical symptoms and alterations in the chewing strokes on the frontal plane and in the rhythm of chewing movements. At first, the experimental denture with no lateral shift was inserted into the subject's mouth. Next, this was replaced by the experimental denture with a lateral shift of 1mm, and then this was replaced with a denture with a lateral shift of 2mm. When clinical obstruction was encountered, during this process this was replaced by one with a lateral shift of 0.5mm. Analysis of data of mandibular movement obtained was performed by means of a personal computer system. Results 1. Individual difference was observed in the process of adapting to laterally shifted intercuspal positions. One subject adapted adequately to a shift of 2mm, another to a shift of 1mm; and still another to a shift of 0.5mm. One subject failed to adapt adequately to a shift of 0.5mm. 2. When the laterally shifted intercuspal position was newly established, subject complained of a slightly high feeling in occlusion on the direction opposite to the lateral shift, occlusal sounds, and glide from the initial contact positions to the intercuspal position. All subjects, however, found it difficult to indicate the amount or direction of lateral shift; and there was no obstruction to intentional mastication under these conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

To observe effects of the procedure on craniofacial growth and development, the author removed 10mm of the right zygomatic arch from rats. The subjects (128 rats) were divided into 3 groups: operation group, sham-operation group, and control group. Surgical removal of the right side of the zygomatic arch was performed on 51 rats; sham operations were performed on 42 rats, and 35 rats served as controls. Operations were performed 30 days after the animals' births. The rats were sacrificed 60 to 120 days after birth. Lateral and parietal cephalograms of the crania were projected by means of a profile projector, model V-16, and enlarged 5 times. Because they reveal craniofacial-facial morphology most clearly, 15 lateral and 7 parietal points were selected. Coordinates of these points were plotted by means of an X--Y plotter system Tracings were composed as follows: For lateral cephalograms, the intersphenoid synchondrosis(S)was the zero point, and the line between S and the basion (Ba) was the abscissa. For parietal cephalograms, the occipital bone was the zero point; and the line between (0) and the upper central (Ui) was the abscissa. The masseter muscles were microsectioned for observation of changes in muscle fibers. Results 1. There were no significant differences among the body weights of the 3 groups (control, operation, and sham operation). 2. There were no significant differences in ulnar length among the 3 groups 3. Facial asymmetry and changes in occlusion were noted in the group observed 120 days after surgery. 4. Lateral cephalographic examination showed that the zygomatic arch has almost no influence on craniofacial growth and development in terms of relations among the points examined. 5. Parietal cephalographic examination showed that removal of the zygomatic arch promoted depth development and suppressed width development in the zygomatic-arch region of the side on which surgery was performed. This may indicate that the zygomatic arch acts to suppress anterior and posterior craniofacial growth and development while promoting growth and development in the lateral dimension. 6. Horizontal cytology of the masseter muscle showed atrophied masseteric tissue at the resected site of the zygomatic arch. But, because this was a partial resection, influence of muscular function is slight. And data obtained from this experiment must be considered the outcome of the removal of the zygomatic arch itself.