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H Agematsu

Publications and source records attributed to H Agematsu.

13 recordsLinked to original sources
PubMed2006

Three-dimensional analysis of pulp chambers in maxillary second deciduous molars.

OBJECTIVE: The purpose of this study was to clarify the positional relationship between the crown contour and the pulp chamber using micro-CT system for restorations of maxillary second deciduous molar. METHODS: Five maxillary second deciduous molar teeth each from the deciduous dentition and the mixed dentition periods were used. The positional relationship between the crown contour and pulp chamber was three-dimensionally observed by micro-CT. In addition, the thickness of the dentin at each of the pulp horns and the volume ratio of the pulp chamber against the whole crown were measured. RESULTS: In relationship to the crown contour and the pulp chamber, the pulp horn of the mesiobuccal cusp showed greatest protrusion and eminent swelling of its mesial wall in both the deciduous dentition and the mixed dentition periods. Furthermore, the pulp chamber was shifted to the mesial side. The volume ratio of the pulp chamber to the whole crown, the ratio in the mixed dentition period showed to be significantly smaller than in the deciduous dentition period. The dentin thickness at the mesiobuccal pulp horn was the thinest. CONCLUSIONS: These results suggest that in preparation of cavities in maxillary second deciduous molars, care is necessary not to expose of the mesiobuccal pulp horn. Especially, the mesial wall of the mesiobuccal pulp horn should be noted.

Child↗
PubMed2005

Superficial and deep layer muscle fibre properties of the mouse masseter before and after weaning.

To clarify changes in the properties of the masseter muscle superficial and deep layer muscle fibres, which initiate masticatory movement, myosin heavy chain isoforms were evaluated based on immunohistochemistry at the transcription level in male mice both before and after weaning. In the results, MHC-2b isoforms, the isoforms with the fastest contraction speed, were observed in the superficial layer after weaning. However, MHC-2a isoforms with slower contraction speeds were not apparent. By contrast, in the deep layer, MHC-2a isoforms were present, as were MHC-2b isoforms, however, there were fewer MHC-2b isoforms present than in the superficial layer. The most rapid movement in the mouse mandible was observed anteroposteriorly during mastication. As the superficial layer of the masseter muscle runs parallel to the direction of mandibular movement, the presence of MHC-2b isoforms in it is consistent. The presence of MHC-2a isoforms in the deep layer, lying at right angles to the direction of mastication movement, is consistent with the positional adjustment of the mandible contributed by the deep layer muscle fibres during masticatory movement. We therefore conclude that complicated masticatory movement is achieved by the presence of various muscle bundles within the masseter, each carrying out different roles.

Animals↗
PubMed2005

Changes in the properties of mouse tongue muscle fibres before and after weaning.

The purpose of this study was to clarify any changes in muscle fibre properties in different regions of murine tongue during development, and to assess the effects of functional changes including weaning on these muscle fibres. The tongue was divided into upper and lower regions at the lateral margin, and the expression of myosin heavy chain (MHC) isoforms at different ages was investigated. Expression of genes encoding MHC proteins was quantified at the transcription level by quantitative reverse transcriptase polymerase chain reaction, and the protein expression of MHC isoforms was assessed by immunostaining. No difference was found in isoform expression between the upper and lower regions of the tongue before weaning. However, the expression of MHC-2b increased markedly in both regions after weaning, while that of MHC-2a decreased. At the age of 16 weeks, the expression of MHC-2b in the lower region was greater than that in the upper region. These findings show that during weaning, when there is a shift from sucking behaviour to mastication, the expression of MHC-2b increases along with an increase in the speed and strength of muscle contraction. Also, contraction force becomes stronger in the lower region of the tongue than the upper region at the age of 16 weeks.

Animals↗
PubMed1998

Attachment of the sphenomandibular ligament to bone during intrauterine embryo development for the control of mandibular movement.

The present study examined the relationship between jaw movement and the site of attachment of the sphenomandibular ligament, which is involved in the control of lateral jaw movement. Major fibers of this ligament are attached to the sphenoid spine and the mandibular lingula. During early stages of embryonic development, however, this ligament is not attached to the sphenoid spine. No consensus has yet been reached concerning the time at which this ligament becomes attached to this spine. The present study was performed to resolve this question and to analyze the relationship of this event of jaw movement. Attachment of the sphenomandibular ligament to the sphenoid spine was observed in fetuses at a gestational age of about 8 months (32 weeks). This may be because fetuses undergo functional changes (initiation of jaw movement such as mastication and swallowing) at this gestational age. This finding suggests that the attachment of the sphenomandibular ligament to the sphenoid spine may be related to fetal jaw movements.

Embryonic and Fetal Development↗
PubMed1997

Immuno-scanning electron microscope characterization of large tubules in human deciduous dentin.

BACKGROUND: This study was undertaken to elucidate the type and origin of collagen fibrils which construct the large tubules in deciduous coronal dentin by scanning electron microscope and anti-types I and III collagen antibody procedures. METHODS: The studies were performed on human deciduous teeth. The teeth were fixed in 4% paraformaldehyde solution and then fractured either mesio-distally parallel to the long axis of the tooth or transversely perpendicular to the long axis of the tooth crown. The specimens were three-dimensionally observed employing the scanning electron microscope to distinguish the content of large tubules. Polyclonal antibodies of anti-type I and anti-type III collagen with 20 nm colloidal gold, and secondary electron imaging and backscatter electron imaging of high-resolution field emission scanning electron microscopy were used to examine the types of collagen fibrils. RESULTS: The large tubules extended from the vicinity of the incisal edge of the dentino-enamel junction to the pulp cavity. Inside the large tubules, fibers in compact bundles run parallel to the longitudinal axis of the tubules. The fiber bundles consisted of collagen fibrils which were 50-150 nm in diameter with typical cross striation. Immuno-scanning electron microscopy showed type I collagen-labelling gold particles and type III collagen-labelling gold particles to be abundant on the fibrils. Types I and III collagen-labelling gold particles were present on the banded collagen fibrils regardless of their diameter. CONCLUSIONS: It was found that type III collagen is present together with type I collagen on the fibrils constructing the large tubules of the human deciduous dentin. This immunohistochemical study suggested that the fibrils constructing the large tubules were derived from the von Korff fibers, and types I and III collagens formed copolymers.

Child↗
PubMed1993

Electron microscopic study of the cytoskeleton of osteoblasts in rat alveolar bone: microfilaments and intermediate filaments as demonstrated by detergent perfusion.

To visualize the cytoskeleton and to preserve the morphology of osteoblasts in the alveolar bone, rats were perfused with a mixture of Triton X-100 and a low concentration of glutaraldehyde, and their alveoli were observed under a transmission electron microscope. The alveolar bone osteoblasts contained a large number of fibers (5-6 nm in diameter) which seemed to be microfilaments. In the cytoplasm just below the cell membranes at the osteal cell surfaces, the microfilaments formed thick bundles distributed in parallel with the long axis of the cell. These findings suggest that, in rat alveolar bone osteoblasts, the bundles of microfilaments located immediately below the cell membranes at the osteal cell surfaces are stress fibers in situ.

Actin Cytoskeleton↗
PubMed1993

Histological studies on the effects of tooth brushing on repair of alveolar bone after periodontal osseous surgery in the rat incisor.

The purpose of this study was to elucidate the effects of tooth brushing on repair of alveolar bone after periodontal osseous surgery in the labial alveolar bone of rat incisor. The surgery was performed on 24 Wistar rats divided into 2 groups: the experimental group, which was subjected to tooth brushing, and the control group, which was not. In the experimental group, daily tooth brushing was initiated at 4 weeks after surgery. The rats were sacrificed after 1 or 2 weeks of tooth brushing. Microradiographic, light and fluorescence microscopic examinations were made of sections of the alveolar bone and its surrounding tissue. After 1 week of tooth brushing, callus with a low degree of mineralization and with large, irregularly arranged, young osteocytes appeared in the superficial layer and crest portion of alveolar bone in the brushing region. Numerous blood vessels had invaded the callus. In this region, the height of osteoblasts on the callus surface increased. At the alveolar crest region, the callus was approximately 3 times thicker than in the superficial region. After 2 weeks of tooth brushing, modification had occurred in the callus; this region had evolved into developed bone with a compact matrix. These findings suggest that the intermittent mechanical stress of tooth brushing is useful in activating the cells of the alveolar periosteum and in stimulating bone formation.

Alveolar Process↗
PubMed1993

Cytoskeletal organization in fibroblasts of rat calvaria periosteum: microfilaments demonstrated by detergent perfusion.

The authors examined the microfilament of fibroblasts in rat calvarial periosteum by transmission electron microscopy after perfusing rats with a mixed solution of Triton X-100 and a low concentration of glutaraldehyde. Fibroblasts in the periosteum were fusiform and had elongated oval nuclei. Microfilaments with diameters of 5-6 nm were noted within the cytoplasm. Although these microfilaments were parallel to the long axis of the cell, stress fibers, which are thick bundles of microfilaments present in cultured fibroblasts, were not observed in these fibroblasts.

Actin Cytoskeleton↗
PubMed1993

Scanning electron microscopic observation on the dentin surface of rat enamel-free areas.

Formation of the enamel covering on the dentin of the tooth crown is thought to depend upon the dentin surface structure during the early stages of enamel development. For this reason, observations were made of the dentin surfaces of both the enamel-free area (EFA) and the region beneath the enamel area. After treatment with sodium hypochlorite and formic acid, scanning electron microscope observations were made of the EFA surface and the exposed dentin surface beneath the enamel of unerupted rat mandibular first molars. Cone-like projections consisting of matrix fibers were observed on the dentin surface covered with the enamel. These cone-like projections formed continuous ridges that connected with the network structure. At the concavities of these network structures these projections were distributed sparsely. Instead of the cone-like projections, the matrix fibers formed a coarse network structure along the surface at the EFA.

Amelogenesis↗
PubMed1990

Scanning electron microscopic observations of microcanals and continuous zones of interglobular dentin in human deciduous incisal dentin.

Scanning electron microscopic (SEM) observation of the coronal dentin of deciduous incisors revealed microcanals and continuous zones of interglobular dentin (CID) in the labio-lingual central portion of dentin beneath the incisal edge. The microcanals, which were clearly larger than dentinal tubules, extended from the incisal edge to the vicinity of the pulp cavity. They were located essentially in the labio-lingual central portion of the dentin and were arranged linearly in the mesio-distal direction. Inside the microcanals, collagen fiber bundles were arranged almost in parallel with the canal long axis: spherical bodies 1.0-2.5 microns in size made up of assemblies of regular parallelpipedal crystals and granulated crystals were also seen. In some instances, bacteria had invaded incisal dentin that had been exposed by attrition. The CID were made up of interglobular dentin aligned with the long axis of the tooth. As was true in the case of the microcanals, several zones were arranged irregularly in the mesio-distal direction, generally in the labio-lingual central portion of the coronal dentin. The CID were confined to about half the width of the incisal edge dentin on the incisal edge side and did not appear in the vicinity of the pulp cavity. Within the interglobular dentin itself, which was surrounded by calcospherites, were longitudinal collagen fibers connected with dentinal tubule walls inside calcified dentin and collagen bundles forming a network with those fibers. Spherical bodies 1.0-1.5 microns in size were observed attached to the surfaces of the bundles or distributed among these fibers. In some instances, the microcanals penetrated the CID.

Child↗