Shika gakuho. Dental science reports最新文献

The performance of the Rotate/Rotate CT scanner "TCT-700 S" (Toshiba) was evaluated on the basis of the item entitled "User's initial acceptance tests (phase II)," set forth in "Standard of performance evaluation for X-ray computed tomography (second recommendation)" proposed by Takenaka et al. (1982). This report describes measurements for noise, contrast scale, spatial resolution, and high- and low-contrast resolution. Recommended phantoms were used to test performance. Results 1. Noise edepended on slice thickness and mAs. It increased as slice thickness decreased. No matter what the slice thickness, noise was great when mAs settings were small. Furthermore, short scan time caused considerable noise for each slice thickness. Reduction of mAs setting caused remarkable increased in noise when slice thickness were 1 mm or 2 mm Under routine examination, when thickness was 5 mm, at 120 kV, with an mAs setting of 440, scan field S(diameter 240 mm), and convolution filter FC-2, noise was 0.31%. When slice thickness was 10 mm at 120kv, 800mAs, with a scan field S (diameter 240 mm), and convolution filter FC-2, contrast scale was 1.84 x 10(-4) (cm-1/CT number). 2. When slice thickness was 5 mm, at 120 kV, with a mAs setting of 1200, scan field S(diameter 240 mm), and a convolution filter of FC-2, spatial resolution was 0.5LP/mm. 3. When slice thickness was 5 mm, at 120kV, with a mAs setting of 1200, scan field S (diameter 240 mm), and convolution filter of FC-2, minimum high-contrast resolution was 0.5 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

The present paper reports results of a study to evaluate clinico-pathologically the effects of calcium hydroxide eugenol preparations on exposed pulp tissues in permanent human teeth. The experiments were performed on 80 vital human teeth from patients ranging in age from 12 to 54 years. The experimental teeth were arbitrarily divided into the following 4 groups. Group CRCS: 20 cases treated with CRCS (Hygienic, Akron, Ohio, USA). Group KEZ: 20 cases treated with Dentalis KEZ (Neo Dental Chemical Products, Tokyo, Japan). Group CE: 20 cases treated with calcium hydroxide eugenol (positive control) Group E: 20 cases treated with pure eugenol (negative control). After local anesthesia, the experimental teeth were isolated with rubber dums or cotton rolls. Following preparation of Black's simple class 1 cavities with a diamond instrument mounted high-speed air turbine, the pulp was intentionally exposed by means of a steel bur mounted electric engine. The cavity and exposed pulp surface were cleaned with saline and dried on absorbent material. Then the experimental materials (agents) were applied to exposed pulp surface. The cavity was lined with gutta-percha temporally stopping, and the remainder was filled with silver amalgam. The teeth were clinically observed at various intervals from immediately to 530 days after treatment and then extracted under local anesthesia and prepared for histopathological study. Decalcified sections were stained with hematoxylin and eosin. 1) CLINICAL OBSERVATIONS: During the observation period, symptoms occurred in the following: Group CRCS: 4 (20%) out of 20 cases. Group KEZ: 4 (20%) out of 20 cases. Group CE: 6 (30%) out of 20 cases. Group E: None of 20 cases No spontaneous pain was observed in these groups. 2) Clinical evaluations Group: CRCS: 16 cases (80%) were good, 3 cases (15%) were satisfactory, and 1 cases (5%) were failure. Group KEZ: 16 cases (80%) were good, 1 cases (5%) were satisfactory, and 3 cases (15%) were failure. Group CE: 14 cases (70%) were good, 4 cases (20%) were satisfactory, and 2 cases (10%) were failure. Group E: 20 cases (100%) were good. 3) Histopathological observations. Various kinds and degree of pulp changes were occurred in each group. Hyperemia and round-cell infiltration resulting from damage caused by treatment and medicaments were frequent in each group. No suppurative inflammation occurred in group CE. Pulp cicatrization and apposition of dentin on pulp chamber walls were observed frequently in each groups. Hard tissue formation was observed in numerous cases of group CE and in some cases in group CRCS and KEZ.(ABSTRACT TRUNCATED AT 400 WORDS)

The following results were obtained from a study on differences in eruption of the lateral segments of permanent dentition; that is, 3 (canine), 4 (first premolar), and 5 (second premolar). This study has been conducted for 9 years and 6 months on the same individuals (30 males and 29 females, aged between 6 years and 15 years and 6 months). Every 3 months, oral examinations using dental models of the upper and lower jaws were performed. In studying eruption order, teeth in the lateral segment were treated as a group. Replacement period started with the initial eruption of any of the teeth listed above and ended with the eruption of the last tooth in the group. comparisons were made between right and left lateral segments. Results 1. In the upper jaw of males, eruption orders 4----3----5, 4.3----5, and 4----3.5 were dominant in 76.90% of the right sides and 77.78% of the left sides. Corresponding percentages for females were 56.00% for the right and 57.90% for the left side. The difference between right and left sides was 0.8% in male subjects and 1.69% in female subjects. Dominant types of eruption order in the lower jaw were 3----4----5, 3.4----5, and 3----4.5. In males, these types occurred in 77.77% of right sides and 82.29% of left sides. Corresponding percentages for females were 96.00% for the right and 99.99% for the left side. The difference between right and left sides was 11.52% in male subjects and 3.99% in female subjects. 2. Initiation of replacement period varies according to eruption-order type.(ABSTRACT TRUNCATED AT 250 WORDS)

The Population of 12-15 years is a key age group for oral health because the permanent dentition and periodontal tissues are almost complete at this stage. The purpose of this study was to evaluate oral health status and to develop an effective school dental health program for junior high schools students. The survey was performed on 527 persons aged 12-13 at 2 junior high schools in the suburbs of Chiba city. Periodontal disease was evaluated on the basis of the CPITN, and analyzed for severity and region of periodontal disease. Gingivitis was examined with PMA index, using color photo slides taken of anterior dentition at the time of inspection. At the same time, caries experience and oral hygiene index were also estimated. The results were as follows: (1) The mean DMFT was 3.89. Caries prevalence in females was higher than males. Ratio of treated teeth rate was 77.03%; that of untreated teeth rate was 22.65%. Females revealed less treatment for caries than males. Oral hygiene index showed significant difference between males and females. Labial and buccal parts of the maxillary and molar region on the mandibular showed remarkable plaque deposition. Calculus accumulation in this population was greatest on the lower incisor. (2) The mean PMA index was 7.36. Gingivitis was highly prevalent in both sexes, although it was more severe in males. There was correlations between PMA index and OHI. (3) From the results of CPITN, 10.6% of the subjects showed no signs of periodontal disease (Code 0), and 5.7% exhibited gingival bleeding (Code 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Various alumina particles were investigated for use as core reinforcement to strengthen aluminous-porcelain jacket crowns. The alumina particles were either spherical or nonspherical and were between 5.3 microns and 60 microns in size. Initially comparisons were made among such properties as particle-size distribution, apparent density, specific surface area, and flow. Then each alumina powder was mixed with feldspar at rates of from 10wt% to 70wt% at increments of 10wt%. Formed into columns, the powder was fired at 1350 degrees C for 5 minutes. The resulting feldspar-alumina composites were compared for shrinkage then cut and prepared into disc specimens. The disc-rupture test was employed to measure composite strengths. A scanning electron microscope was employed to observe alumina particles and composite cross sections. Results 1. Spherical alumina (average particle size 5.4 microns), spherical alumina (average particle size 28.9 microns), and nonspherical alumina (average particle size 58.0 microns) were higher in apparent density and flow rate but lower in specific surface area. 2. Feldspar-alumina composites shrank approximately 30%; shrinkage of 15-20% occurred only in composites involving spherical alumina (average particle size 5.4 microns). 3. Composites of feldspar and spherical alumina were observed to be stronger than those of feldspar and nonspherical alumina. Composites containing 50-60wt% (especially when the alumina particle size was 5.4 microns) were the sturdiest. 4. Increasing the amount of alumina proportionally increased composite strength. In composites containing nonspherical alumina, volume amount and strength were not always proportional. 5. Microscopic examination of composite cross sections showed uniform dispersion of spherical alumina but no dispersion of nonspherical alumina. In conclusion, spherical alumina (especially when average particle size is 5.4 microns) demonstrated the best powder properties as a reinforcing core material and therefore is most suitable for reinforcing the core of the porcelain jacket crown.

Various parameters were used in observing the process of wound healing in rats with streptozotocin-induced diabetes (STZ diabetes). Sections stained according to the Hematoxylin-Eosin, Van-Gieson, and Azan methods were used in observing histological changes. At the same time, wound strength during the healing was measured as a parameter for evaluating the healing process. In addition, changes in leukocytes, plasma fibrinogen, activated factor XIII (aXIII), collagen content of the incised wound, and metabolic changes were determined. Results 1. Histological studies showed that, in STZ diabetes, the inflammatory response was minimal and occurred later than in normal cases. In the incised wound, cellular infiltration of polymorpho-nuclear leukocytes and fibrin nets accumulated poorly. The fibrin net was coarse and fragile. Furthermore, epithelialization of the wound was late: it did not occur until 5 days after the operation. In cases of STZ diabetes, patterns of hyperplasia and fibroblast arrangements were abnormal. Collagen regeneration and proliferation processes were remarkably retarded. 2. In normal, wound strength increased from the 5 postoperative day. After 10 days had passed, it increased remarkably until, after 30 days, it had returned to the preoperative level. In STZ diabetes, however, no increase in wound strength occurred for the first 14 days after the operation. There after strength increased slowly; but, 40 days after the operation, 80% of the preoperative level still had not been reached. 3. Changes in leukocytes were much later occurring in STZ diabetes than in normal. Recovery took longer than in normal. 4. In STZ diabetes, increases in plasma fibrinogen and decreases of the aXIII factor were slower than in normal. The a XIII factor decreased remarkably, and recovery was slow. 5. In terms of collagen content in the wound incision, in STZ diabetes, tropocollagen increase occurred later than in normal. But, from the 5 to the 14 postoperative days, its level was higher than that in normal. Maturation-process collagen and mature collagen increased still more slowly. In normal, mature collagen had reached preoperative level 20 days after the operation, in STZ diabetes, 80% of preoperative level still had not been reached 30 days after the operation. 6. These studies showed that the following factors hinder wound healing in cases of diabetes mellitus: minimal inflammatory response, incomplete formation of the fibrin nets, retardation of epithelialization, retarded action of plasma fibrinogen and the a XIII factor, reduced fibroblast activity, and slow increase in collagen content.

Histopathological observations of vital human and monkey dental pulp were performed to evaluate biologically a new root canal filling material APC containing hydroxyapatite. Experimental materials were divided into the following 3 groups. Group 1. Direct application to pulp wound (monkey teeth), 30 and 90 days. Group 2. Direct application to pulp wound (human teeth), 8-477 days. days. Group 3. Root canal filling on pulp stump (human teeth), 7-461 days. After extraction, the experimental teeth were fixed, demineralized, dehydrated and embedded in celloidin, they were prepared as thin sections and submitted to hematoxylin-eosin staining. Light microscopic observations were then made of them. After fixing, some specimens were embedded in resin and prepared in ultra thin sections before being triple stained with tannic acid-ethanol uranium-lead. They were submitted to observation under a HITACHI H-600 transmission electron microscope (TEM). Element analysis was performed on some unstained sections by means of energy dispersive X-ray analysis with a Kevex 7000A. Results 1. Application of APC to monkey dental pulp had no inhibiting effects on the healing progressed, the formation of regeneration hard tissue was observed. APC is believed to be biocompatible with dental pulp tissues. 2. Of the total of 50 cases in which APC was applied to human dental pulp, by the end of the experiment, 42 had occurred no symptoms of any kind. Broked down further, this means 23 (92%) of 25 cases in Group 2 and 19 (76%) of 25 cases in Group 3. Of the 25 cases in Group 2, 24 (96%) were evaluated as clinically good, none (0%) as fair, and 1 (4%) as unsatisfactory. Of the 25 cases in Group 3, 22 (88%) were evaluated as clinically good, 2 (8%) as fair, and 1 (4%) as unsatisfactory. Histopathologically, various pathological findings occurred in both groups of experimental materials. In the early stage, hyperemia, hemorrhage, round-cell infiltration, suppurative inflammation, and resorption of dentin in chamber walls were observed. By the thirtieth postoperative day, pulp cicatrization, formation of new hard tissue, and apposition of dentin on chamber walls were observed. TEM investigation of round-cell infiltration, observed in both group, revealed incursions of hydroxyapatite and bismuth in the macrophages. The tendency for hard tissue newly generated has began on 73 days in Group 2 and on 32 days in Group 3. This finding was made somewhat earlier in Group 2. Thereafter, dental pulp continued in a healthy condition.(ABSTRACT TRUNCATED AT 400 WORDS)

Exposure distribution was measured and total risk for individual was estimated in intraoral source radiography. Equipment used was a stat Oralix (Philips). Film dosimetry was employed to obtain exposure distribution in oral mucosa and skin surface of head and neck region. A thermoluminescence dosimeter and an ionizing chamber were used to measure organ doses. Total risk was estimated on the basis of these doses. Conclusions 1. Exposure distribution 1) Oral mucosa Examination of upper jaw showed that exposure in palate was distributed between 100 mR near incisive papilla at hard palate and 1800 mR at the rear part of hard palate. Isodose curves were aligned at practically equal intervals from 100 mR to 600 mR. Curve of maximum dose 1800 mR ran forward in the vicinity of both second molars. Its pattern was not symmetrical on right and left side. Exposure in buccal region was distributed between 50 mR in the front part and 600 mR in the rear part. On both the surface of tongue and the inner side of mandible, low-exposure regions existed in the vicinity of the midline. Zones of higher exposure were to be found on right and left side. Examination of low jaw showed that isodose curves between 50 mR and 1000 mR were observed in right and left side of palatal area. Exposure in buccal region was distributed between 60 mR and 600 mR. Exposure at the center of tongue was 1800 mR, but it decreased to 1000 mR at the tip of tongue. High exposure was observed on both sides of tongue and mandible. Examination of lateral jaw showed that maximum exposure 1800 mR occurred on the side of radiation objective. In all three examinations, levels of exposure in oral mucosa were higher in the rear than in the front. Furthermore, exposure distribution was not symmetrical on right and left side. These results coincided with measurements of spatial patterns of x-ray intensity. In all examinations, lead-lining of applicator reduced exposure effectively. 2) Skin surface of head and neck region Examination of upper jaw showed that isodose curve of 10 mR ran through root of nose, eyelid, earlobe and mandibular angle ultimately to reach low lip. Curve of maximum exposure 100 mR was located in cheek region. Examination of low jaw showed that isodose curve of 10 mR descended through upper lip and earlobe ultimately to reach to lower part of thyroid gland. Curve of maximum exposure 100 mR was found in cheek region.(ABSTRACT TRUNCATED AT 400 WORDS)

The purpose of this study is to examine adhesive condition on the inner surface of free enamel. If it was possible to use an adhesive composite resin to reinforce free enamel, it would be unnecessary to remove the free enamel entirely. To this study, we have used a visible light-cured and adhesive composite resin for the inner surface of free enamel. At the first, we carried out SEM examination of adhesive condition on the inner surface of free enamel. Then we performed thermal cycling test for pigment invasion. Results 1. SEM observation found tag-like extensions on the inner surface of free enamel. These extensions were of 2 shapes: horseshoe and beehive. 2. Thermal cycling test for pigment invasion showed practically no difference in marginal leakage between the experimental free-enamel cavities and control box cavities. 3. As a result of observation of adhesive conditions on the inner surface of free enamel, we believe that a certain degree of reinforcement of that enamel can be expected from composite resin.

In previous studies (Shikwa Gakuho 80: 473-485, 1471-1486, 1980), the authors have reported on sealing properties in vitro. But the recent development of many new sealers makes necessary a detailed reexamination at this time. The experimental materials were as follows; Zinc oxide eugenol sealer......Canals Calcium hydroxide eugenol sealer......CRCS, Dentalis KEZ Calcium hydroxide guaiacol sealer......FR Hydroxyapatite sealer......Finapec APC, Apatite root sealer TYPE III The experimental procedure employing a glass tube and the dye-penetration method was similar to the one used in previous studies. Results of the investigation; 1. Degrees of dye penetration were classified into 3 types i) Immediate penetration through the zone between the material and the glass tube within 2 days.--Apatite root sealer TYPE III, Dentalis KEZ ii) Little penetration within 12 hours but gradual penetration to the deep zone thereafter.--CRCS, Canals iii) Slight penetration within 7 days and then gradual penetration 1/5 of the way through the zone between the material and the glass tube.--Finapec APC 2. Dye penetrated through the material in the case of apatite root sealer TYPE III and FR.