Lymphatic networks in the periodontal tissue and dental pulp as revealed by histochemical study.

The structural organization and fine distribution of the lymphatic networks in the periodontal tissues (gingiva, periodontal membrane, and alveolar process) and dental pulp of animals and humans were reviewed with special reference to histochemical examination by light and electron microscopy. The distinction between lymphatics and blood vessels was made on cryostat sections of undecalcified and calcified teeth treated with EDTA solution and whole mount preparations of periodontal membranes using 5'-nucleotidase (5'-Nase)-alkaline phosphatase (ALPase) double staining. This staining procedure allowed lymphatic vessels in the periodontal tissue and dental pulp to be differentiated from blood vessels. The specificity and localization of the enzyme reactions were confirmed by comparative histochemical studies of the same specimen with light microscopy and scanning or transmission electron microscopy. Well-developed 5'-Nase-positive lymphatic networks were observed on the tissue sections and whole mount preparations of the gingiva, periodontium, and dental pulp. More lymphatic vessels were seen in the root area of the periodontium than in the cervical area. In the dental pulp, lymphatic vessels were more numerous in the central part than in the peripheral odontoblastic layer. These distributions of the lymphatic capillary networks are discussed in relation to their ability to supply lymph to the teeth.     

Ultrastructural changes in feline dental pulp with periodontal disease

A light and transmission electron microscopic study was conducted on dental pulp on cats suffering periodontal disease. After extraction, pulp tissues were fixed and embedded in Epon-Araldite. Thick layers of predentin (50 microm) and odontoblasts (30 microm) were observed. In thin sections, odontoblasts showed many mitochondria and secretary vesicles. Some capillaries with several fenestrations were located within the odontoblastic layer. All the sections of pulp examined displayed a generalized infiltration of chronic inflammatory cells. Fibroblasts displayed lytic changes in some areas. These findings imply that the pulp is significantly affected by periodontal disease and furcation-involved teeth should be a carefully considered factor when dental treatment is planned.     

Review on microbial metabolomics of probiotics and pathogens: Methodologies and applications

In recent years, microbial metabolomics, a new field that has attracted wide attention, provides a map of metabolic pathways and clarifies the interaction mechanism between microorganisms and hosts. Many microorganisms are found in the human intestine, oral cavity, vagina, etc. Probiotics could maintain the good health of the host, while pathogens and an imbalance of bacterial flora lead to a series of diseases of the body and mind. Metabolomics is a science for qualitative and quantitative analysis of all metabolites in an organism or biological system, which could provide key information to understand the related metabolic pathways and associated changes. This approach analyzes the final products of cellular regulatory processes, the level of which can be regarded as the ultimate response of the biological system to genetic or environmental changes. Microbial metabolomics has been widely used in different research fields, such as microbial phenotypic classification, mutant screening, metabolic pathways, microbial metabolic engineering, fermentation engineering monitoring and optimization, microbial environmental pollution, and so on. However, there are only a few reviews on microbial metabolomics of probiotics and pathogens. This review summarizes the main methodologies, including sample preparation, identification of metabolites, data processing, and analysis. Recent applications in microbial metabolomics of probiotics and pathogens are also described. This paper first summarized the research progress and application of microbial metabolomics from two aspects: probiotics and pathogenic bacteria. Probiotics and pathogenic bacteria do not exist independently most of the time; hence, these were reviewed in the research field of coexistence of probiotics and pathogenic bacteria, which was subdivided into important microbial research fields closely related to human health, including the human gut, oral cavity, food, and nutrition-related microorganisms. Then, the main problems and trends associated with microbial metabolomics are discussed.     

Dental neuroplasticity,neuro-pulpal interactions,and nerve regeneration

This review covers current information about the ability of dental nerves to regenerate and the role of tooth pulp in recruitment of regenerating nerve fibers. In addition, the participation of dental nerves in pulpal injury responses and healing is discussed, especially concerning pulp regeneration and reinnervation after tooth replantation. The complex innervation of teeth is highly asymmetric and guided towards specific microenvironments along blood vessels or in the crown pulp and dentin. Pulpal products such as nerve growth factor are distributed in the same asymmetric gradients as the dentinal sensory innervation, suggesting regulation and recruitment of those nerve fibers by those specific factors. The nerve fibers have important effects on pulpal blood flow and inflammation, while their sprouting and cytochemical changes after tooth injury are in response to altered pulpal cytochemistry. Thus, their pattern and neuropeptide intensity are indicators of pulp status, while their local actions continually affect that status. When denervated teeth are injured, either by pulp exposure on the occlusal surface or by replantation, they have more pulpal necrosis than occurs for innervated teeth. However, small pulp exposures on the side of denervated crowns or larger lesions in germ-free animals can heal well, showing the value of postoperative protection from occlusal trauma or from infection. Current ideas about dental neuroplasticity, neuro-pulpal interactions, and nerve regeneration are related to the overall topics of tooth biomimetics and pulp/dentin regeneration.     

Dental pulp stem cells and banking of teeth as a lifesaving therapeutic vista

Exfoliated deciduous or an extracted healthy adult tooth can be used to harvest, process, and cryogenically preserve dental pulp stem cells. Future stem cell-based regenerative medicine methods could benefit significantly from these mesenchymal stem cells. Teeth serve as a substantial source of mesenchymal stem cells, otherwise disposed of as medical waste. Care should be taken to store this treasure trove of stem cells. Collective responsibility of patients, dentists, and physicians is necessary to ensure that this valuable resource is not wasted and that every possible dental pulp stem cell is available for use in the future. The dental pulp stem cells (DPSC) inside teeth represent a significant future source of stem cells for regenerative medicine procedures. This review describes the ontogeny, the laboratory processing and collection, and isolation methods of DPSC. This review also discusses currently available stem cell banking facilities and their potential use in regenerative medicine procedures in dental and general medical applications in the future.     

Three-dimensional wall structure and the innervation of dental pulp blood vessels.

The involvement of neural components in plasma extravasation and blood flow in the dental pulp has been established by pharmacological and physiological studies. We review here the segmental constitution of pulp vessels and the possible involvement of neural components in both the contractility and permeability of the pulp vessels from a morphological viewpoint. Six vascular segments can be identified based on the morphology of peri-endothelial cells, such as smooth muscle cells and pericytes. These are: muscular arterioles, terminal arterioles, precapillary arterioles, capillaries, postcapillary venules, and collecting or muscular venules. The perivascular nerve forms a mesh with numerous terminal varicosities, some of which attach directly to arteriolar smooth muscle cells. This mesh can be seen by scanning electron microscopy, and indicates the important role of neural components in regulating the pulpal circulation. After administering norepinephrine (0.2 mg/kg/dog), the surface texture of the smooth muscle cells of pulp arterioles reveals marked irregularities, which are correlated with arteriolar contraction. The pericytes in larger postcapillary venules (diameter 20 microm or larger) also show irregularities, whereas no changes are seen in the pericytes of either smaller postcapillary venules or capillaries. The intercellular spaces of pericytes in the postcapillary venules are wide enough for leukocytes to pass through, and the occasional extravasation of leukocytes through venule walls can be seen under electron microscopy. The microvessels of healthy human dental pulp react weakly to selectins, indicating that apparently healthy dental pulp may be weakly inflamed. In rat dental pulp, CGRP-immunoreactive nerves and nerve terminals containing many granular vesicles supply the postcapillary venules more densely than the arterioles, which suggests the involvement of postcapillary venules in neurogenic inflammation in the dental pulp.     

Imaging of endodontic biofilms by combined microscopy (FISH/cLSM – SEM)

Scanning electron microscopy is a useful imaging approach for the visualization of bacterial biofilms in their natural environments including their medical and dental habitats, because it allows for the exploration of large surfaces with excellent resolution of topographic features. Most biofilms in nature, however, are embedded in a thick layer of extracellular matrix that prevents a clear identification of individual bacteria by scanning electron microscopy. The use of confocal laser scanning microscopy on the other hand in combination with fluorescence in situ hybridization enables the visualization of matrix embedded bacteria in multi-layered biofilms. In our study, fluorescence in situ hybridization/confocal laser scanning microscopy and scanning electron microscopy were applied to visualize bacterial biofilm in endodontic root canals. The resulting fluorescence in situ hybridization /confocal laser scanning microscopy and scanning electron microscopy and pictures were subsequently combined into one single image to provide high-resolution information on the location of hidden bacteria. The combined use of scanning electron microscopy and fluorescence in situ hybridization / confocal laser scanning microscopy has the potential to overcome the limits of each single technique.     

Natural frequency analysis of tooth stability under various simulated types and degrees of alveolar vertical bone loss

The aim of this study was to test natural teeth stability under various simulated types and degrees of alveolar vertical bone loss, as well as to assess the role that the surrounding bone played for maintaining tooth stability. A three-dimensional finite element model of the human maxillary central incisor with surrounding tissue, including periodontal ligament, enamel, dentin, pulp, and alveolar bone, was established. One side and multiple vertical bone loss were simulated by means of decreasing the surrounding bone level apically from the cemento-enamel junction in 1 mm steps incrementally downward for 10 mm. Natural frequency values of the incisor model with various types and degrees of bone loss were then calculated. The results showed that, with one-sided bone resorption, the model with labial bone loss had the lowest natural frequency decreasing rates (8.2 per cent). On the other hand, in cases of multiple bone loss, vertical bone resorption at the mesial and distal sides had more negative effects on tooth stability compared to vertical bone losses on facial and lingual sides. These findings suggest that the natural frequency method may be a useful, auxiliary clinical tool for diagnosis of vertical periodontal diseases.     

The fracture-flip technique reveals new structural features of the Escherichia coli cell wall

With few exceptions, all bacteria possess a wall which protects them and controls their communication with the environment. In Gram-negative bacteria the cell wall exhibits a complex and unique multilayered organization. We have applied a modification of the freeze-fracture technique known as 'fracture-flip' to visualize the real surfaces of the different wall layers in a Gram-negative bacterium, Escherichia coli . In combination with treatments to weaken the interlayer connections, this technique has provided new insights into the structure of the bacterial wall. Large areas of an intermediate layer (most probably the peptidoglycan-containing matrix) have been visualized for the first time between the plasma membrane and the outer membrane of the wall. Extensive regions corresponding to the cytoplasmic face of the plasma membrane have also been obtained. These images provide new three-dimensional views of the bacterial cell wall and provide the structural framework for the analysis of the molecular relationships between the different cell wall components.     

A novel whole tooth-in-jaw-bone culture of rat molars: Morphological, immunohistochemical, and laser capture microdissection analysis

In conventional whole‐tooth culture systems, limitation exists regarding maintenance of the vitality of the dental pulp, because this tissue is encased in rigid dentin walls that hinder nutrition supply. We here report a whole tooth‐in‐jaw‐bone culture system of rat mandibular first molars, where transcardiac perfusion with culture medium was carried out before placement of the jaw bone into culture medium, aiming to facilitate longer time preservation of the dental pulp tissue. Following 7 days of culture, the pulp tissues were analyzed by histology and immunohistochemistry to ED2 (antiresident macrophage). ED2‐positive macrophages were also analyzed for their Class II MHC, interleukin‐6 (IL‐6), and p53 mRNA expression levels by means of immune‐laser capture microdissection (immune‐LCM). Dentin sialophosphoprotein (DSPP) mRNA expression in odontobalstic layer was also examined by LCM. Teeth cultured following saline‐perfusion and nonperfusion served as cultured controls. Normal teeth also served as noncultured controls. Histological examination demonstrated that the structure of the pulp tissue was well preserved in the medium‐perfused explants in contrast to the cultured control groups. The Class II MHC, IL‐6, and p53 mRNA expression levels of ED2‐positive cells and DSPP expression levels of odontoblastic layer tissues in the pulp of medium‐perfused explants were not significantly different from those in the noncultured normal teeth. In conclusion, the structural integrity and mRNA expression in the pulp were maintained at the in vivo level in the ex vivo whole tooth‐in‐jaw‐bone culture system. The system may lay the foundation for studies aiming at defining further histological and molecular mechanism of the pulp. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Lymphatic vessels in the oral cavity: different structures for the same function.

A study using a light and transmission electron microscope was performed on some structural characteristics of the lymphatic capillaries in different regions of the human oral cavity. The lymphatic capillaries of dental pulp, masticatory mucosa (gingiva and peri-implant mucosa) and lining mucosa (cheek) were examined. Our attention was focused on the morphologic characteristics of the endothelial wall in the lymphatic capillaries. In particular, the connections between endothelial cells were investigated. In the lymphatic capillaries of the dental pulp, the endothelial wall was always very complex. It frequently presented protrusions of the endothelial cells that overlapped and formed intercellular channels. These channels were thus contained by the vessel endothelial wall with their extremities opening out towards the surrounding interstitium and the vessel lumen. The endothelial wall of the lymphatic capillaries of the cheek was very smooth and thin without complex intercellular junctions. The endothelial cells were joined by end-to-end junctions and open junctions were frequently observed. Intercellular channels were also found in the endothelial wall of lymphatic capillaries of the gingiva and the peri-implant mucosa. The presence of numerous clefts represented by the open junctions in the lymphatics of the cheek and the existence of complex intercellular adhesions with the formation of intercellular channels in the endothelial wall of the lymphatic capillaries of the dental pulp and gingiva induce us to believe that these may play a role in the various mechanisms used by lymphatic capillaries to absorb interstitial fluids. These mechanisms are based on the different morpho-functional characteristics of the surrounding tissue.     

Mesenchymal stem cells,the secretome and biomaterials: Regenerative medicine application

Mesenchymal stem cells (MSCs) are multipotent cells usually isolated from bone marrow, endometrium, adipose tissues, skin, and dental pulp. MSCs played a crucial role in regenerative therapy and have been introduced as an interdisciplinary field between cell biology and material science. Recently, MSCs have been widely explored for their application in regenerative medicine and COVID-19 treatment. Different approaches to evaluate the future of biomaterials and stem cell properties have been developed. However, misconceptions and ethical issues still exist, such as MSCs being non-angiogenic, anti-apoptotic, and immunoregulatory competencies. Embryonic stem cells isolation primarily requires the consent of donors and can include the killing of fertilized eggs. These issues generate questions related to ethical and moral issues. However, MSCs have gained considerable attention for tissue regeneration owing to their differentiation ability with immunomodulatory effects. They are capable of secreting a broad range of biomolecules such as proteins, nucleic acids, exosomes, microRNAs, and membrane vesicles, collectively known as secretomes. Secretomes are released in response to the surrounding microenvironment. In this article, we briefly address topics related to the therapeutic potential of MSCs as an advanced approach in the field of regenerative medicine and various perspectives.     

Artefacts arising during preparation of hydrated paper pulp samples for low-temperature SEM

Beating, a pulp treatment widely used in the paper industry, causes disruption of cell wall layers and fibrillation. Previous studies of the effects of beating on fibre morphology have used conventional methods of specimen preparation, with all the attendant problems of shrinkage and distortion during dehydration. Low-temperature scanning electron microscopy (LTSEM) therefore seemed to offer an ideal method for examining fully hydrated wood pulp fibres. Cryofixation of pulp followed by sublimation of superficial ice, however, is shown to generate artefacts indistinguishable from structures present in the samples. Fibrillar and membranous structures were generated in LTSEM-prepared sugar solutions; their presence in pulp samples was therefore attributed to the dissolved carbohydrates inherent in pulp suspensions. Since artefact and fact are currently impossible to distinguish in LTSEM-prepared pulp samples, it seems that the technique should be applied to wet paper or pulp samples with considerable circumspection.     

Resin luting materials: Tissue response in dog's teeth

The aim of this study was to evaluate radiographically and histologically the pulpal and periapical response to self‐adhesive (Rely X? Unicem) and self‐etching and self‐curing (Multilink^®) resin‐based luting materials in deep cavities in dogs' teeth. Deep class V cavities (0.5‐mm–thick dentin) were prepared in 60 canine premolars and the following materials were applied on cavity floor: Groups I/V—RelyX? Unicem; Groups II/VI—Multilink^®; Groups III/VII—zinc phosphate cement (control) and; Groups IV/VIII—gutta‐percha (control). Cavities were restored with silver amalgam. Animals were euthanized after 10 days (groups I–IV) and 90 days (groups V–VIII). Tooth/bone blocks were radiographed and processed for histopathological evaluation of pulp and periapical tissue response to the materials. All materials presented similar histopathological features and radiographic findings at both periods. The pulp tissue was intact. The apical and periapical regions and periodontal ligament thickness were normal. No inflammatory cells, resorption of mineralized tissue (dentin, cementum, and alveolar bone) or bacteria were observed. The lamina dura was intact and no areas of periapical bone rarefaction or internal/external root resorption were observed radiographically. It can be concluded that Rely X? Unicem and Multilink^® caused no adverse tissue reactions and may be indicated for cementation of indirect restorations in deep dentin cavities without pulp exposure. Microsc. Res. Tech. 78:1098–1103, 2015. © 2015 Wiley Periodicals, Inc.     

Improved sectioning and ultrastructure of bacteria and animal cells embedded in lowicryl

Lowicryl K4M-embedded Gram-positive and Gram-negative bacteria have a tendency to separate between the cell surface and the resin. This often leads to distortion of bacteria and more especially of mycobacteria. We describe attempts made to overcome this technical problem. Different assays were made on Bacillus subtilis, Escherichia coli, and Mycobacterium avium: (1) Modification of the bacterial surface by coating of bacteria with proteinic compounds; (2) treatment of bacteria with metallic salts known to modify cell wall polysaccharides; and (3) comparison between Lowicryl K4M and HM20. Conditions have been found in which the separation of all bacterial species from the resin is abolished. The most important factor appeared to be the treatment of bacteria before dehydration, with 0.5% uranyl acetate for 30 min. The second most important factor, especially for M. avium and to a lower extent for Gram-negative bacteria, was the use of Lowicryl HM20. Pre-embedding in gelatin instead of agar improved sectioning of M. avium, but had no effects on the other bacterial species. These conditions applied to macrophages infected with Shigella dysenteriae or M. avium also gave excellent results. In addition to sectioning improvement of bacteria, uranyl acetate improved the ultrastructure of bacteria and macrophages. All organelles were more clearly delineated and, hence, more easily identified. Finally, it was shown that UA treatment did not affect immunogold labeling of a variety of antigens.     

Periodontal regeneration: a challenge for the tissue engineer?

Periodontitis affects around 15 per cent of human adult populations. While periodontal treatment aimed at removing the bacterial cause of the disease is generally very successful, the ability predictably to regenerate the damaged tissues remains a major unmet objective for new treatment strategies. Existing treatments include the use of space-maintaining barrier membranes (guided tissue regeneration), use of graft materials, and application of bioactive molecules to induce regeneration, but their overall effects are relatively modest and restricted in application. The periodontal ligament is rich in mesenchymal stem cells, and the understanding of the signalling molecules that may regulate their differentation has increased enormously in recent years. Applying these principles for the development of new tissue engineering strategies for periodontal regeneration will require further work to determine the efficacy of current experimental preclinical treatments, including pharmacological application of growth factors such as bone morphogenetic proteins (BMPs) or Wnts, use of autologous stem cell reimplantation strategies, and development of improved biomaterial scaffolds. This article describes the background to this problem, addresses the current status of periodontal regeneration, including the background biology, and discusses the potential for some of these experimental therapies to achieve the goal of clinically predictable periodontal regeneration.     

Evaluating the lucrative role of probiotics in the aquaculture using microscopic and biochemical techniques

The present study focused to elucidate the promising role of probiotics in the fish culture, by employing microscopic and biochemical parameters to rationalize the possible outcomes. After preliminary feeding trial histopathological analysis revealed clear and visible changes in the intestinal and liver cells of CTRL (control group) compared to probiotics supplemented group, the bacterial inoculations resulted in shorten and swelled villi, while liver kupffer cells increased many folds in the CTRL. Moreover, there was clear hypertrophy and lamellar fusion in the gills tissues examined under microscope. Furthermore, intriguing results were obtained, such as a substantial increase in the weight gain, specific growth rate (%BW/day), FCE%, survival%, and improved secretions of amylase, cellulase, and protease activities. Likewise, high crude protein, fats content, while low moisture and total Ash was noticed in EXP I (Probiotics supplemented) compared to CTRL. The microscopic and biochemical analysis disclosed the positive role of probiotics on the fish health, thus we suggest its supplementations in the fish diet.     

口腔设备和材料进出口发展趋势

随着人类生活水平的提高,人们对牙齿的保健、美观和牙病防治的意识增强,为口腔医疗器械孕育良好的市场基础,口腔用医疗器械需求量日益增加。从贸易角度看,我国口腔材料和设备进口规模稳步快速增长,2006-2010年复合增长率高达27.89%,而出口金额逐年增长,但增长幅度逐渐降低,主要原因在于我国产品在材料和技术方面与发达国家还有一定差距。本文分析我国口腔设备和材料2010年进口和出口情况,重点分析进口和出口规模、区域和国别市场、省市和贸易方式等情况,以期为我国企业开拓国际市场提供参考。