Korff Fibres Research Articles

Relationships between dentin and enamel mineral at the dentino–enamel boundary: electron tomography and high‐resolution transmission electron microscopy study

To better understand the nature of the relationships between mineral phases at the dentino-enamel boundary (DEB), we performed electron tomography (ET) and high-resolution transmission electron microscopy (HR-TEM) of the apical portions of rat incisors. The ET studies of the DEB at the secretory stage of amelogenesis revealed that nascent enamel crystals are co-aligned and closely associated with dentin crystallites in the mineralized von Korff fibers, with the distances between dentin and enamel crystals in the nanometer range. We have further studied the relationships between dentin and enamel crystals using HR-TEM lattice imaging of the DEB. Among dozens of high-resolution micrographs taken from the DEB we were able to identify only one case of lattice continuity between dentin and enamel crystals, indicating direct epitaxy. In other cases, although there was no direct continuity between the crystalline lattices, power spectra analysis of lattice images revealed a very high level of co-alignment between dentin and enamel crystals. Hence, we propose here that the high degree of alignment and integration between dentin and enamel mineral can be established either by epitaxy or without direct interactions between crystalline lattices, probably via regulation of mineral formation and organization by integrated organic matrices of dentin and enamel at the DEB.

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

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. 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. 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. 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.

The mineralization of mantle dentine and of circumpulpal dentine in the rat: an ultrastructural and element-analytical study.

The purpose of this study was to compare the biomineralization of circumpulpal dentine with that of mantle dentine by ultrastructural and element-analytical techniques. Forty upper second molar germs of 10-day-old albino rats were cryofixed in liquid nitrogen-cooled propane and embedded in resin after freeze drying. Semithin dry sections were cut for analyzing the calcium and phosphorous concentration in initial mantle dentine, at the mineralization front of circumpulpal dentine, in the middle region of circumpulpal dentine and in mantle dentine peripheral to circumpulpal dentine. For the morphological evaluation of mineral deposits we compared ultrathin and unstained sections of cryofixed molars with chemically fixed molars. For both dentine types it was found that they develop via identical steps of mineral formation at collagen fibrils and non-collagenous matrix molecules. In circumpulpal dentine no globular mineral protrusions along the mineralization front (i.e. calcospherites) and no indications of interglobular dentine at the transition from circumpulpal dentine to mantle dentine were present. Two von Korff fibres were not only visible in mantle dentine but also in circumpulpal dentine. Matrix vesicles were present only during the formation of an initial coherent layer of mantle dentine and could not be observed during successive formation of mantle dentine and circumpulpal dentine. The element-analytical data did not demonstrate any difference in the mineral content between the two dentine types. Therefore, we conclude that mantle dentine and circumpulpal dentine in the rat molar possess a high degree of structural and chemical similarity and that only the extent of terminal branching of the odontoblast processes gives an approximate estimation of the thickness of mantle dentine.

Immunoelectron-microscopic study of the localization of fibronectin in the odontoblast layer of human teeth

Indirect immunofluorescence-based studies have shown similarities in the distribution patterns of fibronectin-positive fibrous structures and so-called von Korff fibres. The aim of the present study was to analyse the reactivity of fibronectin in the odontoblast layer of fully developed human teeth by means of immunoelectron microscopy. Between the odontoblasts, discrete and undulatory fibrillar fascicles with peroxidase labelling were observed. They seemed to be in contact with odontoblasts in some areas, while in others they appeared to be intervening between two neighbouring odontoblasts. Higher magnifications of the fibrillar material demonstrated axial periodic staining of about 70 nm. Peroxidase reaction of fibronectin was also recognized along the cell membrane of odontoblasts facing predentine. The fibronectin in fibrillar fascicles observed between odontoblasts would be held in place by the direct molecular interaction with collagen fibrils and contribute to the pulpward migration of these cells and maintenance of their specific morphology. At the distal end of odontoblasts, a tight seal would be maintained by means of odontoblast-fibronectin adhesion.

Type III collagen is a major component of interodontoblastic fibers of the developing mouse molar root.

Recently, collagenous interodontoblastic fibers (IOF) were reported in some particular developmental stages and/or locations of the tooth. However, it remained unclear whether these fibers were identical to so-called von Korff fibers. To clarify this issue, we examined the developing mouse molar by three-dimensional reconstruction of 8 confocal images within a 6 micron-thick section using laser scanning confocal microscopy, and confirmed our findings using immunoelectron microscopy. In the root pulp during circumpulpal dentin formation, the IOF stained weakly for type I collagen, but stained strongly for type III collagen by a double-staining technique. It could be clearly seen that many immunoreactive fibers ran spirally among the odontoblasts and entered the predentin. This distribution pattern of IOF was similar to that of the classical von Korff fibers. Furthermore, the existence of anti-type III reactive collagen fibrils between odontoblasts was confirmed, whereas IOF were not observed in the coronal pulp during circumpulpal dentin formation. This study presents for the first time, immunohistochemical observations which demonstrate the presence of IOF at least during root circumpulpal dentin formation and which reveal that type III collagen is a major component of IOF.

Collagen fibrils in the odontoblast layer of the rat incisor by scanning electron microscopy using the maceration method

There is not universal agreement on the existence of the extracellular pathway from the pulp along the odontoblast layer to the predentin. To confirm this pathway, the architecture of collagen fibrils in the rat incisor dentin and pulp, especially in the odontoblast layer of the lateral (periodontal ligament) sides of the tooth, was demonstrated in the present investigation using scanning electron microscopy of the maceration method for collagen networks. Numerous collagen bundles were observed in the odontoblast layer in the mature odontoblast region which, except for the young odontoblast region, comprises the major portion of the incisor. The collagen bundles went from the pulp, through the odontoblast layer, and were woven into the collagen network of the predentin. The meshwork structure was composed of fine secondary fibrils among these collagen bundles. The surface of the predentin contained many oval-shaped holes which were surrounded by collagen fibrils. Fracturing the dentin longitudinally relative to the dentinal tubules revealed that the arrangement of the collagen fibrils at the surface of the tubules was either circular or oblique. In the young odontoblast region, i.e., the thin portion from the apical end of the incisor where the mineralization of the dentin does not occur and where the height of the odontoblasts was less than 30 microns, many thick bundles composed of thick collagen fibrils ran straight from the pulp to the predentin through the odontoblast layer and fanned out in the collagen network of the predentin. These thick bundles might correspond to the so-called "von Korff fibers." The distribution of collagen fibrils in the pulp was random except on the surface of the blood vessels where the fibrils comprised two sheets of collagen: the inner sheet which coursed longitudinally to the long axis of the vessel, and the outer sheet which ran transversely. It was considered that the fluid in the pulp could flow to the predentin along the collagen fibrils through the tight junction between the odontoblasts.

A confocal laser scanning microscopic study of the immunofluorescent localization of fibronectin in the odontoblast layer of human teeth

The distribution of fibronectin in dental pulp was studied in developing and developed human teeth by indirect immunofluorescence using a confocal laser scanning microscope. In the apical region of developing teeth, intense fluorescence was found along the basement membrane facing the mesenchyme of Hertwig's epithelial sheath and first-formed (mantle) predentine. With further elongation of odontoblasts, fibronectin was observed between the cells, appearing as corkscrew fibres passing from the pulp into predentine parallel to the long axis of the odontoblasts. In the coronal region of developing and developed teeth a similar distribution of fibronectin was observed in the odontoblast layer. At the border zone between odontoblasts and predentine the reaction was intense, but was weak in the predentine itself. In the calcified dentinal matrix it had disappeared completely, except for the area along the dentinal tubules. The results demonstrate that fibronectin is present in the odontoblast layer during all stages of dentinogenesis. Fibronectin-positive fibrous structures between odontoblasts probably correspond to von Korff fibres, and are closely related to odontoblast differentiation and dentinogenesis.

Investigation of the role of Von Korff fibers during murine dentinogenesis: Bhavna Shroff Farmington, Connecticut: University of Connecticut, 1989

The existence and significance of Von Korff fibers during early dentinogenesis are still very controversial. The purpose of the present study was to re-examine the questions of the existence, nature and significance of Von Korff's fibers using light microscopy and immunohistochemistry. Specimens were obtained from 3 days-old CD-I mice and mandibles were carefully dissected under constant irrigation and immediately fixed in 10% neutral buffered formalin for light microscopy. Sections were treated or not with collagenase prior to silver staining. For immunohistochemistry, specimens were fixed in 95% ethanol and embedded in paraffin. Sections were reacted with goat anti-human-bovine type I or type III collagen and a rhodamine (RITC) labelled rabbit anti-goat IgG was then reacted as a secondary antibody. Slides were then examined under a Zeiss II photomicroscope equipped with epifluorescence. Our results have confirmed the presence of argyrophilic material concentrated at the periphery of the dental papilla and stretching from the subodontoblastic layer to the future dentino enamel junction. The distribution of type III collagen was very similar to the distribution of the silver staining at the cervical loop area. Type I collagen distribution was different and concentrated in areas where odontoblasts were fully differentiated. Our study showed that Von Korff fibers are not artefactual. We have established the presence of an apical compartment containing type I collagen fibers and a basal compartment containing type III collagen to explain the image of continuous silver staining crossing the entire thickness of the odontoblast layer.

Interodontoblastic collagen (von Korff fibers) and circumpulpal dentin formation: An Ultrathin serial section study in the cat

The collagenous fibers of von Korff pass from the dentin matrix between the odontoblasts into the dental pulp. Although collagen fibrils are known to be present between odontoblasts, the existence of von Korff fibers has remained controversial. This may be because their continuity between the dentin matrix and the pulp has not been demonstrated ultrastructurally. In this study we have examined the odontoblast layer in the middle to apical regions of perfusion-fixed permanent canine teeth of cats by using transmission electron microscopy. Ultrathin sections of demineralized specimens revealed frequent bundles of collagen fibrils 1) entering the odontoblast layer from the predentin, 2) present between odontoblast cell bodies, and 3) passing from between the odontoblasts into the pulp. The question of continuity of these bundles from the predentin, across the odontoblast layer into the pulp was examined in ultrathin serial sections. Unbroken continuity of a collagen bundle from the predentin between the odontoblasts into the pulp was established in a reconstruction of one series of 22 serial sections and was very strongly suggested by a number of other series in which the numbers of available sections restricted their full visibility. This investigation has shown, therefore, that classical von Korff fibers are present and that these fibers are present in fully erupted teeth with closed apices, i.e., at a time when secondary circumpulpal dentinogenesis is in progress. The findings call for a reexamination of the question of von Korff fibers during mantle dentinogenesis and primary circumpulpal dentinogenesis. Resolution of their existence at the earlier stages of dentinogenesis should be possible by using the ultrathin serial-sectioning technique.

Scanning electron microscope study of the predentin-pulpal border zone in human dentin

Fragments of sound human molars were prepared for the scanning electron microscope (SEM) using modified fixative procedures and the carbon dioxide critical-point method to study the predentin-pulpal border zone. This technique minimizes the usual artifacts related to SEM procedures. The elongated odontoblast bodies are closely related to each other at the predentin level. For the first time in SEM procedures, the cell processes almost completely fill the predentinal tubules. Fibers measuring 0.3 to 0.5 μm in diameter are visible between the odontoblasts and fan out into the predentin. They correspond to the so-called Korff's fibers. Others, measuring less than 0.2 μm in diameter, are visible on the predentinal surface and follow the cell processes into the predentinal tubules. They correspond to nerve fibers. This study demonstrates that the proper use of improved SEM fixative techniques and the carbon dioxide critical-point method provides data on the relation between the different components of the predentin-pulpal border zone, which are in agreement with transmission electron microscope data.

放射線照射の乳歯歯髄および歯根膜に及ぼす影響に関する実験的研究

Left mandibular third deciduous molars of young dogs were irradiated for 3, 000R with 200kVp X-ray and the effect on the dental pulp and periodontal membrane was investigated histopathologically. The results were as follows : 1. From 3rd to 7th days after irradiation, localized inflammatory cell infiltration was observed in part in the dental pulp tissue. In the fiber bundles and blood vessel walls, deposition of hyalin stained lightly with eosin was beginning to be observed. No abnormal findings were observed in the periodontal membrane. 2. On 14th day after irradiation in the coronal dental pulp, cells decreased ; karyopycnosis occurred ; cells were connected only by cellular processes, and large and small reticular networks were formed. In the periodontal membrane, fibers ran irregularly although in part and findings of atrophy were seen. Fibroblasts showed a decreasing tendency. 3. In the cases from 1 to 2 months after irradiation, the pulp tissue showed marked atrophy of odontoblasts and the dental pulp showed hyalinization-like changes. Calcareous degeneration stained densely with hematoxylin was found scattered around the blood vessels. Although the pulp cells dicreased extensively but normal pulp cells were still found. In the periodontal membrane, Sharpey's fibers ran irregularly or became indistinct, and fibroblasts decreased extensively. The periodontal membrane in general showed hyalinization. 4. In the cases of 4 months after irradiation, the pulp tissue on the whole showed marked atrophy and disappearance of odontoblast layers. From the coronal dental pulp to the root pulp, reticular atrophy and hyalinization were seen. In the periodontal membrane, inflammatory cell infiltration was seen in part and membrane fibers, as those in 2nd month, showed marked atrophy, became enlarged, and presented findings of hyalinization. 5. At 8th month, the nucleoli nearly disappeared in the pulp tissue from the crown to the root and the cells were connected like filaments by cellular processes. Nearly all the blood vessels and fibers disappeared. At this stage, Korff's fibers from the pulp to predentin were no longer observed. In the periodontal membrane, most of Sharpey's fibers disappeared. Fibroblasts showed marked atrophy and disappearance, and few normal fibloblasts could be found. In the cementum and alveolar bone, marked resorption was seen. In the resorbed region of the cementum, apposition of cementum-like hard tissue was observed and the hard tissue adhered to the alveolar bone, and findings of bony ankylosis were observed.

Early Dentinogenesis in Mice: von Korff Fibres and Their Possible Significance

By light and electron microscopy we have confirmed the collagenous nature of von Korff fibres in early dentinogenesis in mice. Each fibre array begins as an argyrophil 'stem' lying between the outermost cells of the dental papilla, with finer divisions passing into the papilla. With the appearance of odontoblasts, a cone-like 'spray' of nonargyrophil fibres in continuity with the stem spreads peripherally between these cells to the dental epithelial basement membrane. After the sprays become immured in dentine matrix, the stems are removed. Later, new stems appear. Sprays are restricted to enamel-bearing parts of teeth. The possible nature and functions of von Korff fibres are discussed.

Immunofluorescent localization and extractability of fibronectin in human dental pulp

Fibronectin, visualized in premolar pulps by indirect immunofluorescence, was abundant in the odontoblast layer, around blood vessels and in the core of the pulp. Similarity of alignment of fibronectin with the argyrophilic fibres and von Korff fibres was evident. Fibronectin was extracted from pulps after first removing blood by washing with water, confirmed by eventual negative reaction on α 2-macroglobulin. Extraction of fibronectin from this remaining tissue was most effectively achieved by treatment with collagenase or hyaluronidase, though in all cases some fibronectin remained, indicating that fibronectin in pulp is not exclusively associated with collagen and/or proteoglycans. The fibronectin quantified by electro-immunoassay and expressed as percentage of dry weight was 0.030 per cent in the water extract, 0.094 per cent in the collagenase extract and 0.109 per cent in the hyaluronidase extract. Twice as much fibronectin was extracted from the apical pulp as from the coronal and middle parts, in accord with earlier findings of a higher collagen content in the radicular part. It is suggested that with the loss of collagen type III during odontoblast differentiation and its reappearance with advancing vascularization of the dental papilla, the amount of fibronectin is similarly altered.

A supplemental study on the characteristics of Korff's fibers in the dog.

A supplemental study on the characteristics of Korff's fibers in the dog.

Histological study of pulps of human primary teeth

Twenty-seven primary human canines and incisors showing no clinical signs of caries, root resorption or restorative treatment were extracted for orthodontic purposes from patients ranging in age from 7 to 13 1 2 yr , and processed for histologic examination. Odontoblasts were pseudostratified in depths of 1–7 cells in a pulpward direction, with the thickest layers in the coronal pulp. The zone of Weil and the cell-rich zone were present in the coronal third of normal pulp, but absent in teeth with occlusal attrition. Vascular trunks were oriented coronally and exhibited increased branching as they approached the subodontoblastic layer. Collagenous fibers appeared coarse, densely packed, and coronally oriented in the apical third of the pulp, whereas the middle and coronal fibres were fine, loosely packed and randomly oriented. A cap-like dense zone of collagenous and reticular fibres was noted in pulp horns and the periphery of the coronal pulp. Von Korff's fibres were well developed in the coronal pulp but only poorly developed in apical and middle regions of the pulp. Focal mineralizations, closed apices, and a coronal-to-apical change in the staining characteristics of the predentine-odontoblastic border were also noted. There was no structural difference between primary human pulp and young permanent human pulp, other than the presence of a cap-like zone of reticular and collagenous fibres in primary coronal pulp.

A light and electron microscopic study of the adenomatoid odontogenic tumor

The nature of the “tumor globules” and the calcified material contained within seven adenomatoid odontogenic tumors was investigated hy light and electron microscopy. The results showed that the calcified material was heterogeneous, and probably comprised at least three components. An amyloid-like material which exhibited Congo red birefringence and thioflavine T fluorescence was found. Ultrastructurally, fibrils 10–12 nm in diameter morphologically similar to amyloid fibrils were visualized, and these apparently underwent mineralization. It was thought that this material was stromal rather than epithelial in origin. Dystrophic calcification of degenerate tumor cells and a dentin-like material formed the other two components identified. The “tumor globules” which were richly impregnated with silver stains failed to show the presence of fibrils which could be correlated with reticulin fibers ultrastructurally. It was thought that these areas might be compared with von Korff fibers in a developing tooth, where a fibrillar counterpart has similarly not been demonstrated.

The ultrastructure of dentinogenesis and amelogenesis in rat molar tooth germs grown as organ cultures in vitro.

Tooth germs from foetal rats of 17 days post-insemination were maintained in vitro for 12 days. Odontoblasts and ameloblasts differentiated and secreted their respective matrices in which mineralization occurred. The ultrastructure of the cells was qualitatively similar to that observed in normal development. Odontoblasts contained more lysosome-like bodies and were found to degenerate in some sites. Mantle dentine was formed but few von Korff fibres were observed. Calcospherites were rarely seen and the mineralizing front of dentine was predominantly linear, associated with numerous small early foci of mineral formation. Enamel showed prism formation associated with the Tomes' process of the ameloblast but some local disturbances in the pattern of enamel formation were observed.

Electron microscopic studies on Von Korff fibers in the human developing tooth.

AbstractDeciduous tooth germs were removed from the anterior region of human fetuses between 13‐16 weeks of age and fixed in glutaraldehyde. Some were post fixed in osmium tetroxide whilst others were block stained with silver nitrate and prepared for electron microscopy. Thick Araldite embedded sections were cut at 1 μm and stained in various ways for examination by light microscopy. Thin sections of bulk silver stained material were examined with the electron microscope before and after staining with heavy metals.Fibers lying between the developing odontoblasts were demonstrable under the light microscope and their appearance was consistent with the classical description of von Korff fibers. With the electron microscope bundles of collagen fibers up to 1 μm in diameter were present between newly differentiated odontoblasts. Heavy metal staining of sections from bulk silver impregnated material revealed that silver deposition was associated mainly with collagen fibrils. It is concluded that in the crown of human developing teeth, bundles of collagen fibrils are present between the newly differentiated odontoblasts and that these bundles represent those usually described as von Korff fibers.Similar results were found using material from developing molar teeth of mice.

On the so-called von Korff fibers as seen on the human predentinal surface.

On the so-called von Korff fibers as seen on the human predentinal surface.

Radicular pulpotomy of category III pulps. Part III. Histologic evaluation

Twenty-two sound or symptom-free restored teeth (indicated for extraction) of patients 18 to 60 years of age were subjected to radicular pulpotomy and immediate root canal filling. 2 Eight contralateral teeth served as untreated controls. The histologic evaluation led to these results. The untreated control teeth showed regressive changes in the apical third of the radicular pulps consisting of the disappearance of the odontoblasts, von Korff fibers, and the subodontoblastic vascular network starting at the apex and gradually ascending. The regression increased with age. All the treated teeth showed a vital remaining pulp free of inflammation and necrosis. One month postoperatively capping was effected by dentinal chips encapsulated by a fibrotic tissue. Osteodentin matrix formation had begun around advanced dentin chips and at discrete sites of the dentinal walls, while at other areas modeling resorption took place. The frequency and extent of dentinoclasia seemed to depend on the height of the pulpotomy, but they never constituted a clinical problem since dentinoclasia would repair with osteodentin. The remaining tissue had the characteristics of loose connective tissue. Three months postoperatively, the remaining pulp size had been reduced by osteodentin deposition along the dentinal walls and around the dentinal chips thus forming a more or less complete seal. Calcific obliteration depended on the presence of a dentinal plug and its proximity (3 to 5 mm.) to the apex. This was associated with a progressive fibrosis of the remaining pulp tissue in the absence of inflammatory changes. In the light of the favorable biologic results obtained, it may be justified to introduce radicular pulpotomy into daily practice under the conditions that its specific indications for category III pulps are respected and its exacting techniques applied.