Shika gakuho. Dental science reports最新文献

The purpose of this study is to investigate postnatal developmental changes in the shape of the maxilla. Normal maxillary form at each development stage and amounts of growth were analyzed by longitudinally measuring 136 Indian skulls. Maxillary growth changes were assumed on the basis of mean values and growth rates of each region measured. Results 1) Vertical growth Vertical growth of the maxilla (N-Pr) at the fifth (permanent-dentition) stage approximately doubled growth in the first (pre-eruption) stage. The corpus of the maxilla and its alveolar process lay beneath the foramen infraorbit. Vertical growth in this region (m-Pr) increases rapidly during the period of eruption of deciduous and permanent teeth. In permanent dentition, the vertical dimensions of the upper (N-m) and lower (m-Pr) parts of the foramen infraorbit were almost the same. 2) Growth in width As the eyes grow, the upper face widens. Resulting development in the tensed zygomatic-maxillary suture at the inferior margin of the orbit expands the upper surface of maxilla. Maxillary width increased by approximately 1.8 times between the first and fifth stages.

The form of posterior artificial tooth is an essential factor related to denture stability during mastication and to masticatory ability. Generally, cusp teeth are selected out of consideration for balance during eccentric occlusion. From another viewpoint, cuspless teeth are selected to ensure stability and to prevent the occurrence of lateral vectors caused by the inclination of the occlusal facet. It has been reported, however, that the counterbalance phenomenon occurring between occlusal facets decreases the lateral vector. Moreover, cusp teeth are useful in increasing the possibility of establishing bilateral balance. Guidelines for selecting posterior artificial teeth in the production of functional dentures are diverse and cannot be said to have been firmly established yet. This model experiment, which employed complete lower dentures, was designed to provide basic information for discussing the influence of occlusal facets of cusp teeth on denture movements during mastication and to arrive at some clinical suggestions for selecting posterior artificial teeth. Artificial teeth with cusp angles of 0 degrees, 10 degrees, 20 degrees, and 30 degrees were made by adjusting setting conditions on a condylar type articulator. Four kinds of experimental dentures were made and used in measuring horizontal movements of lower dentures during the crushing of experimental food. Final phase of chewing stroke was taken into consideration in establishing two types of loading direction. One type was at 70 degrees (DL 70 degrees) to the occlusal plane on the frontal plane and from the outer side (the working side). The other type was 90 degrees (DL 90 degrees) to the occlusal plane. Maximum load was 15kg and the denture displacement was analyzed at 2kg, 4kg, 8kg and 15kg. Experimental foods were smoked cuttlefish (sectile food), raisins (food flattened under pressure), and peanuts (crushable food). Analyses were made of experimental denture movement patterns and denture displacement amounts. Results 1. Experimental denture movement patterns differed according to the nature of the experimental food. The pattern in the case of smoked cuttlefish was mainly of the C type; that is, primarily motion first to the balancing side and then to the working side. The pattern for raisins was mainly of the S type; that is, primarily motion first to the working side, then to the balancing side, and then to the working side again. Several patterns appeared in the case of peanuts.(ABSTRACT TRUNCATED AT 400 WORDS)

The purpose of this study is to provide information on normal growth and development of the dental arch and alveolar ridge. Materials were longitudinal casts obtained from 38 children (male: 19, female: 19) with normal dentition. The casts were taken at 2-month intervals for the purpose of providing information on tooth emergence. Measurements for chronological age were taken from 11 years and 6 months to 13 years and 6 months. Measurements for dental age were taken during a period of 1 year before and 1 year after emergence of the permanent second molar. In addition to these dental age measurements, other measurements for dental age were made at each evaluation of dental arch length and basal dental arch length for a period of 1 year before and 1 year after emergence of the permanent second premolar. After a reference plane had been established and each cast had been standardized, a formcorder was used to trace 5 sagittal sections at the midline and at the region of the right and left central and lateral incisors. Growth and development of dental arch length, basal arch length, and alveolar width in both the maxilla and the mandible were measured on these 5 sagittal sections. Total dental arch length was taken to be the distance between the mesial surfaces of the permanent first molars and the labial surface of each incisor. Total basal arch length was taken to be the distance between the ridge of the posterior region of the basal arch and the most concave point of the labial basal arch. In addition to casts, lateral cephalometric films were used to measure, at ages 12, 13 and 14, changes in the vertical and horizontal dimensions of both the central incisors and the jaws and the long axes of the permanent central incisors. Results and conclusions 1. Mean growth in dental arch length 1) In the maxilla When growth was evaluated by chronological age, in 2 years, the total dental arch length decreased 1.0-1.2 mm in the region of the central incisors and 0.8-0.9 mm in the region of the lateral incisors. Evaluated by dental age based on the emergence of the permanent maxillary second premolar, up to 2 months before the emergence of that tooth, no notable changes occurred in the total dental arch length in the regions of both the central and lateral incisors. But a remarkable decrease of 0.9-1.1 mm took place thereafter.(ABSTRACT TRUNCATED AT 400 WORDS)

Proplast I, Proplast II and freeze-dried homogenous cartilage (1 x 2 x 5 mm) were implanted under and over the rabbit mandibular periosteum. Histological observations and contact microradiography (CMR) were performed to investigate the healing process in the surgical sites from 1 to 24 weeks after the operation. In addition, microangiography (MA) was carried out to investigate changes of vascularization in the groups in which Proplast implants were made. Results 1. Proplast implantation group 1) In the supraperiosteal placement group, CMR revealed no new bone formation around or inside the Proplast and no morphological changes of the host bone in contact with the Proplast. In the subperiosteal placement group, from the early postoperative stage, new bone formation occurred from the host bone beside the Proplast. New bone penetrated the Proplast from the new bone region and from the host bone in contact with the Proplast. In 6 months after the operation, Almost all Proplast pores were filled with new bone. From a comparatively early postoperative stage, resorption fossae appeared in the host bone surface. In addition, Haversian canals inside the host bone enlarged and the host bone cortex gradually grew thinner. No differences in new bone volume or host bone changes were noticed between the Proplast I and Proplast II groups. 2) In the supraperiosteal placement group, granulation tissue proliferation with slight round cell infiltration was observed around and inside the Proplast at an early stage. In 2 weeks after the operation, blood clots disappeared from the Proplast, in the center of which granulation tissue proliferated. Thereafter, granulation tissue was gradually transformed into fibrous tissue, although no new bone was observed in any region. Change almost never occurred in the host bone cortex, but slight swelling occurred in the periosteum in contact with the Proplast after 1 week. 3) In the subperiosteal placement group, swelling and slight round cell infiltration were observed in the periosteum covering the Proplast at an early postoperative stage. But, after 4 months, the periosteum had returned to normal condition. Beside and inside the Proplast, rapid granulation tissue proliferation and new bone formation were observed. New bone formation was observed beside the host bone, but not beside the periosteum. For a comparatively long time, resorbed fossae in the host bone surface and enlarged Haversian canals persisted. Host bone width gradually decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

Single intraperitoneal injections (180 mg/kg) of 5-fluorouracil (5-FU) were administered to male Wistar rats weighing 100 g each. After 1, 2, 3, 4, 5, 7, 10 and 21 days, the animals were fixed by perfusion with a mixture of 2.5% glutaraldehyde and 2.0% paraformaldehyde. The maxillary incisors were dissected out; and optical-microscopy, microradiography, and transmission electron-microscopy were made of changes occurring in the dental-papilla cells, odontoblasts, and dentin matrix. 1. One day after the 5-FU injection, considerable amount of damage had occurred in the basal portion of the incisor forming a large void in the dental-papilla (cell-free region) immediately below the inner enamel epithelium. But, 4 days after the injection, the cell-free region was filled again with numerous newly regenerated dental-papilla cells (reparative region). Thereafter these cells differentiated as regular odontoblasts. 2. In 1 day after the injection, dental-papilla cells that had begun differentiating into odontoblasts degenerated and atrophied (degeneration region). Round cells appeared on the pulp sides of degenerated and atrophied odontoblasts 3 days after the injection. These cells increased in both size and number and formed a hard tissue in which the degenerated odontoblasts had embedded. The matrix of the newly forming hard tissue was composed of closely arranged collagen fibrils. Matrix vesicles were observed in the initial stage of its mineralization. Dentin had deposited on the pulp side of this hard tissue 21 days after the injection. 3. Dentin formation in the reparative region began 7 days after the injection; and, by the twenty-first day, ordinary dentin thickness had been attained. In the degeneration region, however, a little dentin was formed. In contrast, on both sides of the degeneration region, dentin formed in a virtually normal fashion and grew thicker with the passing of time, creating a deep, bowl-shaped concavity in the degeneration region.

The author attempted to determine the feasibility of monitoring blood concentration of antimicrobial agents by estimating blood levels of the agents on the basis of their content in saliva. Since it is difficult to determine drug tissue-penetration degree in humans, at present, tissue concentrations must be estimated from corresponding blood concentration. In the case of orally administered drugs exhibiting great individual differences in absorption by the gastrointestinal tract, frequent blood collection is required for blood-concentration monitoring. Noninvasive and very simple saliva collection, on the other hand, has already been used for monitoring concentrations of such drugs as carbamazepine and antiepileptics. PPA, ENX, NFLX, and OFLX are pyridonecarboxylic acid antimicrobial agents of great usefulness because of their expanded antimicrobial spectrum and their effectiveness even against gram-negative bacteria that exhibit no adequate response to other oral antimicrobial agents. After PPA, ENX, NFLX, and OFLX were administered orally to healthy volunteers, serum and saliva samples were collected. The samples were then centrifuged, deproteinized, and freeze-dried. 1. After the freeze-dried samples were dissolved to give tenfold to twentyfold concentrated solutions, levels of agents were bioassayed by means of the thin-layer-disc method. On the basis of the data obtained in this way, pharmacokinetic analyses were performed according to the one compartment model of Imoto and Yamaoka. A personal computer (NEC-8801, 9801) was used in drawing simulated curves. 2. Percentages of salivary as compared to serum concentrations were as follows: PPA (500 mg)-70, ENX (300 mg)-75, ENX (200 mg)-78, NFLX (200 mg)-35, and OFLX (200 mg)-105. Corresponding values for pharmacokinetic data were as follows: PPA (500 mg)-77.2, ENX (300 mg)-74.2, ENX (200 mg)-85.0, NFLX (200 mg)-30.0, and OFLX (200 mg)-91.6. Coefficients of correlation (r =) between salivary and serum concentrations in measured data were as follows: PPA (500 mg)-0.915, ENX (300 mg)-0.989, ENX (200 mg)-0.953, NFLX (200 mg)-0.887, and OFLX (200 mg)-0.886.(ABSTRACT TRUNCATED AT 400 WORDS)

Subcutaneous injections of 8.4 mg of sodium fluoride were administered to young male Wistar rats weighing 100 g each. After 1, 3, 6, 12, and 24 hours and then after 2 and 4 days, the rats were fixed by perfusion; and their upper incisors were subjected to optical microscopy, microradiography, and electron microscopy. In some instances, 0.1% ruthenium red (RR) was added to the fixing or demineralizing solution for the sake of observing acid-mucopolysaccharide distribution. 1. The following changes were observed in odontoblasts: swelling of the rough endoplasmic reticulum, vacuole formation, increased numbers of autophagic vacuoles and Golgi vacuoles, and abnormal accumulation of cytosome-4. All of these changes tended to have recovered by 24 hours after administration. 2. In the predentin, abnormal increases in amounts of amorphous substance occurred 1 hour after and continued until 12 hours after administration. Thereafter, increases gradually retarded; and the level observed in controls was restored by the fourth day after administration. RR staining showed this amorphous substance to contain large amounts of acid mucopolysaccharides. 3. Two types of abnormal collagen--segmental collagen aggregate (SCA) and fibrous long-spacing collagen (FLS)--were observed in the amorphous substance mentioned in the preceding paragraphy. In longitudinal sections, SCAs were 320 nm long and 200 nm wide; symmetrically arranged striations were visible within them. FLSs were observed as long, thick fibrils with periodic striations of about 160 nm. With the passing of time, these abnormal collagen aggregates and fibrils shifted from the distal end of the odontoblast toward the dentin, in which they became embedded. 4. Mineralization in the abnormal collagen commenced with deposition of needle-shaped or thin platelike crystals. As time passed, the collagen came to be completely covered with the crystals. Loosening of collagen molecular binding seems to occur following advances in mineralization and crystal growth. 5. Abnormality in dentin mineralization resulted in the formation of a hypermineralized layer and a hypomineralized layer beneath the hypermineralized layer. The hypermineralized layer contained densely distributed crystals. Its boundary with the hypomineralized was clearly observable. The boundary with teh regular dentin, however, was shifting and indistinct.