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The aim of the present study was to investigate the proliferating activity of peri-implant epithelium immunohistochemically using proliferating cell nuclear antigen (PCNA). Eight ITI (Internationale Team für Implantologie) implants were placed into simulated sockets in the mandibles of two beagle dogs two months following tooth extraction. As a control, junctional epithelium of the molar teeth in the same animals were used. The nature of staining and the distribution of PCNA immunoreactivity were determined by scoring a minimum of 100 cells on two sections from each of the implants. In the junctional epithelium, the immunoreactivity to PCNA was detected mainly in the basal cells, in some of the prickle cells, and in a few cells attached to the enamel. In peri-implant epithelium, only some of the basal cells were positive for PCNA. The PCNA score of the peri-implant epithelium was significantly lower than that of junctional epithelium. These results suggest that the peri-implant epithelium maintains a lower capacity to act as a proliferative defence mechanism than does the junctional epithelium.

Although the adenomatoid odontogenic tumor (AOT) is categorized as an odontogenic epithelial tumor with odontogenic ectomesenchyme, AOT with induction of true tubular dentin with or without concomitant formation of enamel is exceedingly rare. This paper reports a case of AOT showing evidence of extensive induction of tubular dentin, but without concomitant formation of enamel. The patient was a 20-year-old female with a rather well-circumscribed intraosseous lesion of the maxillary incisor-premolar area without an embedded tooth. Histologically, extensive induction of a dysplastic form of tubular dentin with globular calcification was evident, in addition to the characteristic histological features of AOT. The present case lends support to the categorization of AOT as an odontogenic tumor consisting of a disorderly mixture of odontogenic epithelium and odontogenic ectomesenchyme with or without dental hard tissue formation.

The purpose of this study was to examine if the migration of human gingival fibroblasts on titanium was promoted by platelet-derived growth factor (PDGF) and whether the release of urokinase-type plasminogen activator (uPA) was correlated with it. The migration of the fibroblast on titanium was significantly promoted by PDGF in a wound healing assay (p0.001). The promotive effect was inhibited by aprotinin, a serine protease inhibitor used for the inhibition of uPA (p0.001). The conditioned medium when fibroblast migration was promoted contained a higher concentration of uPA than did that of the control. These results indicated that the promotive effect of PDGF on the migration of human gingival fibroblasts on titanium was correlated with the release of uPA from the fibroblasts.

The purpose of this study was to examine laminin localization in epithelial rests of Malassez grown on titanium and their gelatinase activity. Laminin localization was confirmed by immunocytochemistry in all epithelial cells grown on titanium. The conditioned medium from the epithelial cells grown on titanium exhibited 72kD- and 92 kD-gelatinase activities by gelatin zymography. Those results suggest that laminin contributes to the epithelial cell attachment to titanium and that gelatinases may be mobilized for epithelial cell movement on titanium.

Osteogenic activity of autografted dental pulp, periodontal ligament, and bone marrow of rat in vivo was investigated. Immunolocalization of ALPase in situ was also studied. One month after the transplantation, osteodentin was formed in all the dental pulp transplants (100%), bone or cementum like tissues were created in 20% of periodontal ligament transplants, and bone like tissues were in 20% of bone marrow transplants. After two months, osteodentin was produced in all the dental pulp transplants (100%) and bone like tissue were in 50% of both periodontal ligament and bone marrow transplants. Immunohistochemically, positive reactions to ALPase in situ were detected in cells just below the odontoblast layers in dental pulp, surface layers of alveolar bone in periodontal ligament, and endosteal membrane of bone marrow space. From these results, it was suggested that the cells of these three kinds of tissue can be termed osteogenic-fibroblasts in vivo.

The aim of this study was to examine about the etiology of large cyst formation in pleomorphic adenoma from the histopathological standpoint by examining four cases of our own as well as previously reported ones. In the first of our cases, a large cyst wall lined with keratinized squamous epithelium was observed. In the second, a large cyst containing mucinous material was lined with a single cell layer of squamous epithelium-like cells. The third case was a carcinoma in pleomorphic adenoma with some large cysts lined with multiple layers of atypical epithelial cells. In the fourth case, a hemorrhagic portion were seen on a large cyst wall without a lining of epithelial cells. From these histopathological observations and the suggestions of previous authors, we surmised that the large cyst formation in pleomorphic adenoma might originate from the squamous metaplasia of tumor cells and the enlargement of duct-like structures by outstanding secretion from tumor cells or salivary gland tissues, hemorrhagic portions, or necrosis in the malignant tumor.

Demineralized dentin pieces were implanted in 18 rat submandibular glands to examine the chondrogenesis and osteogenesis in pleomorphic adenoma of the salivary gland. After 7 days of implantation, a large amount of cartilage tissue was found next to the inner portions of the implanted pieces, and small amounts of the osteoid and cartilage tissues were detected next to the outer portions. A small amount of bone tissue was found in contact with the cartilage 10 days after the implantation. In the inner portions, invasions of capillaries and a small amount of osteoid tissue were noted. These histological findings resembled those of endochondral ossification. Large amounts of bone tissue and resorption of the implant were observed after 14 days. It has been suggested that cartilage and bone are produced by bone morphogenetic proteins (BMP) in demineralized dentin resulting in chondrogenesis followed by osteogenesis in submandibular gland. Apparently, undifferentiated mesenchymal cells are produced by implantation, undergo dedifferentiation, and are redifferentiated into chondroblasts and osteoblasts in the presence of BMP. These results suggest that chondrogenesis and osteogenesis in the submandibular gland are induced by BMP. It is possible that the chondroid tissues in pleomorphic adenoma of the salivary glands are induced by proteins such as BMP.

Freeze-fracture electron microscopy was employed to study the general morphology, membrane fusion during exocytosis, intercellular junctions in adult and developing salivary glands, and morphological changes of intercellular junctions in secretory stimulation and neoplastic disorders. Intramembranous particles distributed on plasma membranes and organelle-membranes were determined on the basis of particle density per unit. Relationship between distribution and density of particles and functions of membranes and organelles was discussed. Fused membranes took the form of smooth areas of intramembranous particles free on the PF face in the submandibular acinar cells induced by isoproterenol stimulation. The sequence of membrane fusion during secretion was discussed from these freeze-fracture observations. Tight junctions which limited solute diffusion between adjacent cells formed continuous belts around the juxtaluminal region of plasma membrane. Their permeability function was regulated by the number and the geometrical pattern of the tight-junctional strands. The junction appeared late during gestational life, and its development and morphology correlated with the establishment of electrochemical tightness. Similarity in the location and morphology between developmental and neoplastic conditions might indicate reflect the function and degree of cytodifferentiation in salivary gland. Gap junctions were detected as clusters of particles, representing voltage-regulated intercellular channels connecting adjacent cells. The junctions were developmentally regulated, and their size and frequency correlated with the functional activity and with cytodifferentiation in neoplastic disorders. Desmosomes, which appeared as round or elongated clusters of particles, provided the mechanical stability necessary to maintain the organization of acini and ducts.

Dental pulp, periodontal ligament, bone marrow and muscle tissue from the same rat were cultured in vitro in order to investigate their osteogenic activity by transmission electron microscope. Immunohistochemical methods with various antibodies were utilized and alkaline-phosphatase (ALPase) activities of these cells were also measured biochemically. Dental pulp cells were stellate in shape, showed an intense ALPase reaction, and had lipid-like droplets. Periodontal ligament cells were composed of spindle fibroblasts and epithelial cells. The former revealed a positive reaction for ALPase and possessed microfilaments. Bone marrow cells were spindle shaped, resembling fibroblasts, but some of them were similar to osteoblasts. Muscle cells were long, slender in shape, and showed no positive reaction for ALPase. The cells from pulp tissue showed the highest activity of ALPase, followed by periodontal ligament and bone marrow; there was no activity in muscle tissue. All the cells except the epithelial-like cells of the periodontal ligament and muscle cells were positive in reaction with ALPase which is a marker for osteogenic cells, and vimentin which is a marker of fibroblastic characteristics. Osteogenic activity and cellular differentiation of these cells were discussed.

This paper reports a case of multiple dens invaginatus (DI) bilaterally involving the maxillary central incisors, mandibular canines, and first premolars. The patient was a 11-year-old boy with steeple-head and mild mental retardation. The maxillary central incisors showed disproportionately large crowns and short roots. A roentgenographic survey of the skeletal system showed a sutural hyperostosis of the skull at bregma and a hypoplastic cervical vertebra. The review of the literature yields 6 cases of multiple DI, including the present case; these can be classified into 2 types, cases of only DI and cases of DI with anomalies of skeletal and other systems. Morphological differences in the central incisors are found between these 2 types.

The present paper describes the relationship between ameloblastoma and ameloblastic fibroma deduced from a case diagnosed as "ameloblastoma combined with ameloblastic fibroma" arising in the mandible of a 5-year-old boy. Histologically, the tumor consisted of ameloblastoma in the central area and ameloblastic fibroma in the peripheral area; it clinically fits the characteristics of ameloblastic fibroma based on predominant age, manner of growth, and encapsulation. We reviewed the literature and discussed the relationship between ameloblastoma a ameloblastic fibroma in terms of tumorigenesis. It is assumed that ameloblastic fibroma can also be transformed into ameloblastoma, if the succeeding hard tissues are not formed, and the collagenous connective tissue substituting for the stromal mesenchymal tissue is formed by the inductive effect of the epithelial strands or other unknown factors. Several possibilities relative to the pathogenesis of ameloblastoma have been proposed by oral pathologists; however, to our knowledge, "ameloblastic fibroma can be transformed into ameloblastoma" has not hitherto been reported. The case we experienced here may be thought as an intermediate tumor pattern between ameloblastic fibroma and ameloblastoma.

The purpose of the present study was to elucidate the biological characteristics of pocket epithelium in experimental periodontitis. Elastic rubber was inserted between the first and second molars of the left maxilla in rats. The rubber was removed after one week, and the animals were sacrificed one week after the removal, i.e., two weeks after the insertion. Sections of the teeth and surrounding tissues were examined by electron microscopy. Periodontal pockets were evident between the tooth surface and epithelial cell layer in the coronal portion. A large number of bacteria surrounded by neutrophils were observed on the cementum surface in the pocket; however, no bacterial invasion could be seen in the epithelium. The epithelial cells were spilt in the central portion by invasion of neutrophils, so that one or two layers of surviving epithelial cells were present on the cementum surface. Numerous fenestrations of capillaries were found in the connective tissue immediately below the epithelium. These results suggest that the pocket epithelium is formed by an intercellular split of the epithelium, not between cementum surface and epithelium.

Cells with both osteogenic and chondrogenic capabilities from various connective tissues, dental pulp, periodontal ligament, bone marrow, muscle and subcutaneous connective tissues of the rat were investigated by using either mineralized or demineralized bone and dentin matrix in vitro. After 28 days of the cell culture, explant cells were examined histologically. Bone and cartilage formations were assessed by counting their numbers in serial sections. Induction of cartilage was occurred only in muscle. New bone formation was occurred most frequently in dental pulp, followed in order by bone marrow and periodontal ligament. These results suggest that osteogenic cells, dental pulp, bone marrow stromal cells, and periodontal ligament can not response to inductive stimuli such as the bone morphogenetic protein, BMP.

Histological, immunohistochemical, and ultrastructural studies were done on a case of congenital gingival tumor with previously undescribed histopathological findings. The present lesion clinically mimicked a congenital epulis (congenital gingival granular cell tumor); however, it histologically consisted of densely packed collagen fibers forming numerous, well demarcated bundles surrounded by flattened cells with long slender cytoplasmic precesses. Immunohistochemical and ultrastructural findings suggested that these flattened cells embracing collagen bundles were fibroblastic in nature. Intracytoplasmic lysozomal granules could not be found in any cells of the lesion. Fibrous lesions similar to the present case have not been documented previously in the literature.

Basal cell adenoma of the parotid gland was studied with immunohistochemical methods. We observed cells in the tumor with positive reaction to polyclonal keratin, prekeratin, monoclonal PKK-1, polyclonal S-100 protein, monoclonal S-100 protein (alpha), secretory component, actin and laminin. However, no cells which stained positively with monoclonal KL-1, amylase, carcinoembryonic antigen, or epithelial membrane antigen were recognized. From these immunohistochemical results and our ultrastructural observations reported previously, we conclude that the cells constituting the basal cell adenoma are ductal, myoepithelial, and squamous cells but not secretory ones. It is also suggested that the origins of basal cell ademona as well as those of pleomorphic and clear cell adenoma are undifferentiated cells of intercalated duct.

Cells of dental pulp, periodontal ligament, bone marrow and muscle derived from the same rat were cultured in vitro. Outgrowth of cells from these four explants were examined using phase-contrast microscope, light microscope and scanning electron microscope. Furthermore, cell lengths were measured randomly from SEM photographs and growth curves were plotted by calculating cell numbers. These cells had different morphology in both shape and length. The bone marrow cells showed the most rapid proliferation rate followed by muscle, periodontal ligament and most slowly in dental pulp cells.

The purpose of the present study is to elucidate influences of diet on periodontal regeneration following experimental periodontitis in rats. S-D rats were divided into two groups, which were fed either a conventional diet (group A) or a sucrose-rich diet (group B). Experimental periodontitis was produced by placement of elastic bands between maxillary molar teeth. After one week, the elastic bands were removed and the animals were sacrified by perfusion fixation with formalin immediately, 1, 3, or 5 days, or 1, 2, 3, 4, 6, or 8 weeks after the removal. Sections of the teeth and surrounding tissue were examined by light microscopy. Three days after the removal, in both groups, granulation tissues with many inflammatory cells were covered by epithelial cells; the attachment site to the root surface was located more apically than the cemento-enamel junction. Distinct periodontal pockets were formed by five days after the removal in group A. In group B, the infiltrations of inflammatory cells were more prominent than in group A. Six weeks after the removal in both groups, an epithelium which resembled long junctional epithelium rather than pocket epithelium became thicker. Eight weeks after the removal, the findings were similar to those of six weeks in group A. However, a severe inflammatory cell concentration was found in group B. These results suggest that periodontal wound healing is markedly influenced by diet, and that this experimental system is useful for studying dynamic changes in both pocket and long junctional epithelia.

Basal cell adenoma of the parotid gland was studied with electron microscopy. The cells constituting this tumor were divided into three types of epithelial cells; ductal, myoepithelial, and squamous cells. The ductal cells, which were polygonal and cuboidal in shape, formed a sometimes distinct lumen. Glycogen were recognized in the cytoplasm of these cells. The myoepithelial cells appeared as plasmacytoid cells which contained abundant microfilaments. The squamous cells were characterized by the presence of well-developed tonofilaments and desmosomes. However, no secretory cells could be found, although small, electron dense granules were detected in the cytoplasm of the ductal cells. The granules were unlike secretory granules in their size, number and location. In consideration of the presence of secretory and myoepithelial cells, we reviewed previously reported literature and discussed the identification of secretory granules. From our and other reported results, we tentatively concluded that the electron dense granules described as secretory granules are not intrinsic secretory granules. Further, we suggested that the cell types and the histogenesis of basal cell adenoma are analogous to those of both pleomorphic and clear cell adenomas.