Shika gakuho. Dental science reports最新文献

With the aim of improving understanding of the transition the mandible internal structure undergoes between the dentulous and edentulous states, the thickness of the substantia compacta, the ratio of trabecular bone to the total substantia spongiosa, and the thickness of the trabecular bone were measured in 9 edentulous mandibles aged 45 to 65 years. The measurements were made with an image-treatment device outfitted with a personal computer. Results 1. Thickness of the substantia compacta The thickest zones (3.00-3.81 mm) were located on the lingual side of the anterior teeth; the second thickest zones (2.20-2.48 mm) were located on the superior lingual and buccal side of the molars. The thinnest zones (1.66-1.67 mm) were located on the labial side of the anterior teeth; the second thinnest zones (1.71-1.75 mm) were located on the buccal side of the premolars. Little difference (1.90-2.18 mm) was observed in the bases of the mandibular areas. In the region of the lingual side, the thickest zones occurred in the premolars. Little difference in thickness was observed between the premolar and molar zones. On the labial-buccal side, thicknesses increased from the premolar to the molar zones (which were the thickest) and decreased gradually from the mental to the premolar zones. Comparisons showed that the anterior teeth zoon in the edentulous mandible the substantia compacta is thinner on the labial side and thicker on the lingual side than it is in the dentulous mandible. Little difference between the dentulous and edentulous mandibles was observed in the lingual side of the molar zone, although the buccal side was thinner in the edentulous than in the dentulous mandible. 2. Ratio of trabecular bone to the total substantia spongiosa The highest ratios (74.03-89.62%) occurred in the mental zone; the second highest (69.07-82.92%) occurred in the incisor zone. The lowest ratios (30.61-39.61%) occurred in the superior and middle regions of the premolar zone. The inferior area of the premolar zone, however, was relatively wider (42.83-55.66%) than the superior and middle areas. The following ratios of trabecular bone to total substantia spongiosa were observed: The highest ratio occurred in the zone of the anterior teeth, the next highest ratio in the molar zone, and the lowest ratio in the premolar zone. Although, differences in ratios between dentulous and edentulous mandibles were only slight, a lower ratio occurred in the inferior area of the premolar zone. 3. Thickness of trabecular bone within the substantia spongiosa.(ABSTRACT TRUNCATED AT 400 WORDS)

All teeth on the right side of the upper and lower jaws were extracted from canine specimens; and changes in maxillary trabecular-bone structure caused by the resultant reduction in functional pressure were studied by means of image analysis of trabecular-bone density, width, specific length (which indicates bone length to unit area), and trabecular-bone orientations. Results 1. Trabecular-bone density Over the 13-month period, in comparison with the normal side, trabecular-bone density on the experimental side dropped to 69.4% in the incisor region, 82.2% in the premolar region, and from 60.0 to 68.0% in the molar region. The greatest reduction occurred in the molar region. 2. Trabecular-bone width Over the 13-month period, in comparison with the normal side, trabecular-bone width on the experimental side dropped to 86.9% in the incisor region, 86.1% in the premolar region, and from 66.4 to 71.4% in the molar region. The greatest reduction occurred in the molar region. 3. Specific length Over the 13-month period, in comparison with the normal side, specific length on the experimental side dropped to 81.9% in the incisor region, 82.9% in the premolar region, and from 65.6 to 70.5% in the molar region. The greatest reduction occurred in the molar region. 4. Orientation No regular trabecular-bone orientation was observed in the tooth-extraction sockets. In the incisor region, trabecular bone was often distributed at from 100 degrees to 120 degrees in relation to the dental roots. As time passed after extraction, the amount of bone with this orientation gradually decreased. At 13 months, amounts with bone orientation of from 40 degrees to 60 degrees had increased. In the premolar region, a great deal of trabecular bone was oriented at from 140 degrees to 150 degrees in relation to the dental roots. As time passed after extraction, the amount of bone with this orientation gradually decreased. At 13 months, amounts with bone orientation of from 110 degrees to 130 degrees had increased. In the molar buccal region, trabecular bone was often distributed at from 20 degrees to 40 degrees, and 90 degrees in relation to the dental roots. In the molar palatal region, trabecular bone was often distributed at from 120 degrees to 140 degrees in relation to the dental roots. At 13 months, the amount of trabecular bone oriented at about 90 degrees had increased.

This study was designed to evaluate the differences between the regenerative process in cases of autogenous nerve grafting and lyophilized homologous nerve grafting. Rabbit inferior alveolar nerves (10 mm lengths) were resected and replaced with lyophilized homologous segments from the sciatic nerve. On the opposite side, the resected nerves were autogenously grafted. The experimental subjects were divided into autogenous nerve-graft and the lyophilized nerve-graft groups. Results. 1. Regenerating axons appeared in the autogenous-graft group 2 weeks after the operation and 4 weeks after the operation in the homografted lyophilized group. The difference in regeneration between the 2 groups was significant. 2. Regenerating axons in the autogenously grafted nerves made contact with remaining Schwann cells and endneural tubes. Axons in the homografted lyophilized nerves invaded along newly infiltrated Schwann cells and empty tube skeletal structures. The number of regenerating axons from outside the skeletal structure was greater than the number of regenerating axons from inside the skeletal structure. 3. In the case of autogenous grafting, nerve fibers of diameters greater than 3 microns increased 66.7% after 24 weeks; the corresponding figure for homografted lyophilized nerves was 48.4%. 4. In instances of autogenous grafting, 16 weeks after surgery, the ratio of distal proximal myelinated nerve fibers had grown. In cases of homografted lyophilized nerves, this tendency to increase continued until the twenty-fourth postsurgical week. 5. In both groups, it remained possible to record nerve action potentials 12 weeks after surgery. The sensory nerve conduction velocity of autogenously grafted nerves increased gradually to approach control values 24 weeks after surgery. That of homografted lyophilized nerves recovered more slowly. 6. Increases in number of nerve fibers with a diameter of more than 3 microns were proportional to the rate at which sensory nerve conduction velocity recovered.

The aim of this study is to employ an energy dispersive X-ray spectrometer (EDS) in developing a computer software system for the quantitative analysis of elemental concentrations in biological specimens. The methods and the software were applied to the examination of the coronal dentin of human deciduous and permanent teeth. Results 1. Examination methods. Chemical compounds known for their calcium (Ca) and phosphorus (P) contents were used to determine optimum conditions for analysis. The following were the best analytical conditions: 100 kV accelerating voltage, 2 x 10(-10) A probe current, 10 ekV energy scale, 100 sec. counting time, and 100-150 nm section thickness. Under these conditions, it is possible to obtain statistically sufficient integral spectra values. By calculating with the computer software(t-factor) developed in this study, it was possible to arrive at analytical calcium and phosphorus concentration values that are very close to theoretical values. 2. Application to human dentin. Deciduous intertubular dentin contained 24.9% (w/w) Ca and 12.1% (w/w) P; peritubular dentin in the same teeth contained 30.7% (w/w) Ca and 15.3% (w/w) P. Permanent intertubular dentin contained 25.5% (w/w) Ca and 12.5% (w/w) P; peritubular dentin in the same teeth contained 34.5% (w/w) Ca and 16.9% (w/w) P. These results show that, in both permanent and deciduous teeth, concentrations of Ca and P are higher in peritubular than in intertubular dentin. Concentrations Ca and P in both peritubular and intertubular dentin are lower in deciduous than in permanent teeth. The computer software developed for this study differs from chemical analysis and may prove very useful in microanalysis of mineralized tissues on the basis of their ultrastructures.

The purpose of this study was to investigate color differences between shade guides and light-cured composite resins. Resin specimens were made with resins and opaque resins of Silux Plus and Silux (3 M Co.) in a shade-guide metal mold. The resin specimens and the shade guides therefore were identical in shape and size. The sample resin specimens were compared with the shade guides provided with Silux Plus and Silux light-cured composite resins. Color measuring was performed with the Murakami Color Research Laboratory Fast Spectrophotometer C M S -500 and the Flexible Sensor F S -1. Specimens were placed on a plastic disc fixed to the top of the flexible sensor, and identical areas of their incisal, central, and cervical parts were measured. Conclusions. 1) The delta E*ab values between all shade guides and resin specimens showed color differences detectable to the naked eye. 2) Color differences between shade guides and resin specimens were great for the incisal colors (I, X L) and the deep and dark colors (D G, D Y, Y B, D G O, D Y O, Y B O, D D Y O). Color differences were relatively small, however, for the general colors (U, Y, G, U O, Y O, G O). 3) The L* values of shade guides ranged more widely than those of resin specimens. For many colors, L* values of the shade guides were lower than those of the resin specimens. 4) The a* values of shade guides and resin specimens were much more limited. The a* values of all colors showed minus values. The magnitude of a* values of shade guides were lower than those of resin specimens. 5) The b* values of shade guides were higher for some colors and lower for some colors than those of resin specimens.

The purpose of this study is to evaluate the healing process following application of the plication technique at the postdiscal connective tissue of the temporomandibular joint (TMJ). Female monkeys (Macaca fuscata) approximately eight years old were subjected to bilateral TMJ operations. The plication technique was performed in the left joint of each animal. In the right TMJ, the only operation performed was the exposure of the upper joint cavity. Results. 1) No synovial cells occurred on any upper surfaces of postdiscal connective tissue in left, first-week, postsurgical specimens. No synovial cells were observed in the area from the lateral to the middle upper surface of postdiscal connective tissues in specimens taken from the control side. Synovial cells gradually regenerated from the outside and, by the fourth postsurgical week, all of them had recovered in specimens from both sides. 2) During the early period, fibrin precipitation, round cell infiltration, fibroblast proliferation, and vascularization occurred in the plicated region. But these symptoms gradually decreased; and, by the twenty-fourth postsurgical week, collagen fibers surrounded the sutures. In the upper cavity, sutures were covered by newly proliferated connective tissue four weeks after surgery. The giant cells that proliferated around sutures in the fourth week increased gradually. 3) From the first postsurgical week, connective tissue proliferated in the lateral and middle parts of the superior postdiscal connective tissue in the right joint. Similar proliferation occurred in the left joint in the inner side of plicated region. Round cell infiltration took place in these connective tissue in the early period but gradually decreased. As this occurred, numbers of fat cells increased. No significant difference was noticed between proliferation in the right and left joints. No adhesion to the synovium in the glenoid fossa was observed. 4) In the first postsurgical week, connective tissue proliferated bilaterally from the posterior edges of both the glenoid fossa and the postdiscal tissue. In the second and fourth postsurgical weeks, connective tissue proliferation formed a fold narrowing the upper joint cavity. 5) Synovial cells were absent from the lateral to the middle region of both glenoid fossa from the first postsurgical week. Regeneration took place from the outside, and all synovial cells had recovered by the fourth postsurgical week. Disappearance of synovial cells was more extensive in the left than in the right glenoid fossa. 6) Round cell infiltration, vascularization, collagen fiber hyalinization, and hyperplasia of the fibrous covering occurred in the lateral part of the fibrous covering of the glenoid fossa but gradually decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

In fluoride analysis, there are two procedures for the determination of fluoride depending on nature of samples. One procedure directly can determine fluoride contents by fluoride ion electrode, dissociating fluoride from the sample with the acid (perchloric acid). The other procedure needs to separate fluoride from biological sample using steam-distillation or micro-diffusion method, and then the determination by means of fluoride ion electrode can be applied. In this study, we applied a modified microdiffusion method by Hinoide (1990) for its availability in different temperatures and reaction time, and then estimated to determine fluoride contents of Shrimp (Sakura-shrimp) as a biological sample by this method. It is also very important to determine fluoride contents of foodstuffs and biological samples with regard to bioavailability of fluoride in vivo. The results were as follows: 1. Using the modified microdiffusion method, the fluoride recovery rate attained more than 95% in the range of 0.1-10 micrograms fluoride from a standard solution under the experimental condition of 60 degrees C and 90 degrees C of reaction temperatures and 60, 90 and 120 minutes of reaction time. 2. For the sample of shrimp, fluoride contents analyzed by means of the modified micro-diffusion and steam-distillation methods showed almost similar values, although the fluoride contents by steam-distillation method revealed relatively lower value. The difference might be derived from a loss of fluoride in ashing the sample before applying the steam-distillation method. The modified microdiffusion method used in this experiment can be utilized routinely and precisely in fluoride analysis for small amounts of biological sample.

The purpose of this study is to observe and compare growth and development in the dental arch, the alveolar process, and the palate in reference to dental age, which is based on tooth emergence, and chronological age. Subjects consisted of serial dental casts taken at two-month intervals from 40 children (20 males and 20 females) with normal occlusion in permanent dentition. In terms of dental age, observations were made for a total of two years, one year before and one year after the tooth emergence of first premolar and second premolar. In terms of chronological age, observations were made for a total of two years, one year before and one year after the average age of tooth emergence of first premolars and second premolars in this sample of children. Results and Conclusions. Comparisons between growth changes in the dental arch, the alveolar process, and the palate on dental and chronological age showed some regions in which growth patterns were similar and others in which growth patterns were different. The differences between both growth patterns from two ages were classified into two groups according to the tooth which caused the difference: those produced by the tooth used as a standard for dental age and those produced by teeth other than that used as a dental-age standard. 1) Differences resulting from the influence of the tooth used as a dental-age standard In regions of the tooth used as a dental-age standard, differences occurred in growth patterns on both kinds of age in practically all measured items. In regions adjacent to that of the tooth used as a dental-age standard, the differences were observed in growth patterns of the alveolar process and the palate but not in those of the dental arch. The differences were the most pronounced in the regions of dental-age-standard teeth than in the adjacent regions. The majority of the differences caused by teeth used as standards for dental age were thought to have been the results from the influence of eruption. No growth-pattern differences were observable in regions more than two teeth away from the tooth used as a dental-age standard. 2) Differences resulting from the influences of teeth other than that used as a dental-age standard Using the emergence time of a certain tooth as a dental-age standard, the emergence times of other teeth lead to be come together in some degree.(ABSTRACT TRUNCATED AT 400 WORDS)