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PubMed1997

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.

Animals↗

PubMed1997

SEM examination of secondary dentine under and opposite cervical carious lesions.

The deposition of calcified secondary dentine underlying carious lesions and on the wall opposite to the carious lesions was examined in this study. Twenty single rooted human teeth were used in this work. The teeth were cleaned and fractured into two longitudinal halves, which were examined under a scanning microscope. The results showed complete disappearance of the dentinal tubules, globular mineralized deposits, and mineralized deposits of fibrous morphology underlying carious lesions, while on the dentinal walls opposite to the carious lesions were calsospherites, mineralized secondary dentine, and typical deposition of secondary dentine.

Adult↗

PubMed1991

Scanning electron microscopic study of odontoblasts and circumpulpal dentin in a human tooth.

Two combined scanning electron microscopic methods including modified fixative procedures were used for studying the morphologic aspects of the odontoblasts and the corresponding dentinal wall at different endodontic levels. The odontoblasts were tightly packed in the pulp horn, where they assumed pear-shaped profiles and, from crown to apex, successively looked spindle shaped, club shaped, and globular. Their number decreased in the pulp radicular portion, where the interglobular spaces were enlarged. The filling fibrillar material varied from crown to apex. A globular circumpulpal dentin was observed at all levels of the root canal. The tubule openings varied in number and size.

Adult↗

PubMed1980

Long-term effects of colchicine on dentinogenesis in rat incisors.

Colchicine in doses of 0.5, 1.0 and 1.5 mg/kg was administered to 15 rats divided in three experimental groups. Histomorphologic investigation of the maxillary incisors after 2 weeks revealed; 1) alterations in the odontoblasts mainly related to size, shape, polarity and staining properties, and 2) presence of irregular dentin separated from normal dentin by one or two incremental lines. The dentinal irregularities were dose-dependent and consisted of twisting of the dentinal tubules, globular formations and cellular inclusions in addition to niche-like defects.

Animals↗

PubMed1996

Adenomatoid odontogenic tumor with extensive formation of tubular dentin.

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.

Adult↗

PubMed1998

Dentin dysplasia type I. Report of case and ultrastructural study.

Radicular dentin dysplasia (DD-I) is a rare hereditary dental alteration. It is characterized clinically by almost normal looking crowns and severe hypermobility of the teeth. The radiographic analysis, on the other hand, discloses the obliteration of all pulp chambers, the short, malformed roots and plenty of periapical bone radiolucencies on noncarious teeth. A case of radicular dentin dysplasia is presented. In this 43-year-old woman the diagnosis was supported, besides the clinical and radiographic analysis, by the pedigree of the proband, which showed the autosomal dominant pattern of feature transmission. Further-more, the electron microscopic analysis of one extracted molar revealed the atubular structure of the secondary dentin, and its globular organization.

Adult↗

PubMed1987

Scanning electron microscopy of incinerated teeth.

The aim of the present scanning electron microscopy study was to document the nature of morphologic changes occurring in human enamel and dentin subjected in vitro to temperatures in the range of 200-1,000 degrees C for variable times. The results of the investigation confirm that human enamel and dentin remain microscopically identifiable after incineration at 1000 degrees C. Furthermore, these tissues remain identifiable after incineration at 1,000 degrees C for periods greater than 3 h. No consistent or reliable differences in morphology could be detected in enamel or mineralized dentin incinerated in the temperature range 200-600 degrees C. Temperature-dependent changes involving the predentin zone were observed. Following incineration at 800 degrees C for over 3 h and at 1,000 degrees C for 3 h, a metamorphosis of enamel and dentin into a globular form was observed.

Adult↗

PubMed2006

Mandibular phenotype of p20C/EBPbeta transgenic mice: Reduced alveolar bone mass and site-specific dentin dysplasia.

CCAAT enhancer binding proteins (C/EBP) comprise a family of basic-leucine zipper transcription factors that regulate cellular differentiation and function. To determine the role of C/EBP transcription factors in osteoblasts and odontoblasts, we generated a transgenic (TG) mouse model with Co1a1 (pOBCol3.6) promoter-targeted expression of a FLAG-tagged dominant negative C/EBP isoform, p20C/EBPbeta (previously LIP). Two of the four transgenic lines presented with abnormalities in the developing incisors, including breakage, overgrowth, and malocclusion. Histological examination revealed that the amount of alveolar bone was reduced in TG compared to wild-type (WT) mice. By microcomputed tomography (microCT), the bone volume fraction of the mandible was reduced at the level of the first and third molars, demonstrating a severe mandibular osteopenia. The lingual dentin morphology of TG incisors differed dramatically from WT. Labial dentin (enamel side) showed normal thickness and tubular dentin structure, whereas the lingual dentin was thinner (25-30% of WT at the alveolar crest) with an amorphous globular structure characteristic of dentin dysplasia. FLAG immunostaining was seen in both lingual and labial odontoblasts, indicating that the site-specific defect was not due to a lack of labial transgene expression. Northern blot analysis demonstrated reduced osteocalcin expression in TG mandibles, while bone sialoprotein was increased, consistent with prior results in calvariae and long bones. Dental sialophosphoprotein, a marker of the odontoblast lineage whose absence causes dentin dysplasia, was modestly reduced in TG mice by Northern blot and in situ hybridization analysis. By fluorescence microscopy, pOBCol2.3-GFP, a marker of the odontoblast lineage, was expressed in both labial and lingual odontoblasts, although GFP-marked lingual odontoblasts were more flattened than WT cells. Moreover, GFP-positive processes in the lingual dentin tubules were truncated and less organized than those in WT dentin. MicroCT analysis showed reduced tissue density in the lingual dentin. These data suggest that C/EBP transcription factors may be involved in the regulation of odontoblast polarization and dentin matrix production.

Alveolar Bone Loss↗

PubMed1997

Cyclosporin A-induced alterations of dentinogenesis in rat molars.

Cyclosporin A (CsA), a widely used immunosuppressive drug, induces gingival overgrowth and modifications of bone remodelling. The scope of this study was to investigate the possible effect of CsA on dentin. Thirty mg/kg/day of CsA were administered orally to male Sprague-Dawley rats for nineteen weeks. The same number of control rats received oil-based vehicle solution. Rats were anesthetized, and tissues were fixed by an intracardiac perfusion of fixative solution. Mandibles were dissected, demineralized, and processed for Epon embedding. Semi-thin sections of the first molars revealed alterations at the secondary dentin-pulp interface in four out of six experimental animals. The changes consisted of the formation of: 1) osteodentin spurs, in which the volume and interface with the secondary dentin varied from about 25,000 to 75,000 microns 3 and from 1400 to 3530 microns 2, respectively; 2) abnormally shaped and irregularly spaced incremental lines; and 3) numerous globular formations embedded in dentin or free in the pulp. These results indicate that CsA induces abnormal mineralized matrix formation in dentin and in the peripheral part of the pulp in rat molars.

Administration, Oral↗

PubMed1991

Morphological study of calcospherites in rat and rabbit incisor dentin.

Calcospherites from incisors of rats and rabbits were studied, by means of secondary and backscattered electron images, using scanning electron microscopy. Part of each incisor specimen was made anorganic to allow observation of the surface of the mineralization front by scanning electron microscopy; the other part was ground on one side for observation by scanning electron microscopy with a backscattered electron image detector. In both species the labial mineralization front was wavy and the image showed fused calcospherites, whereas the lingual mineralization front appeared to consist of a combination of linear and globular forms. In rat labial dentin the calcospherites were large and globular form, but they did not develop in the lingual dentin and were small and oval. The shape and size of rabbit incisor calcospherites varied from the pulp horn to the root apex. There were great differences between rats and rabbits with respect to the size and shape of the calcospherites at the mineralization front. This may be due to species differences and possibly the differing rates of dentinogenesis in rats and rabbits.

Animals↗

PubMed1987

Treatment of dentin with stannous fluoride--SEM and electron microprobe study.

The effect of SnF2-treatment of dentin surfaces was investigated by means of scanning electron microscopy (SEM) and electron microprobe analysis. Human dentin was treated with aqueous SnF2 solutions of concentrations varying from 1 to 10%. The treatment periods lasted for 1, 5, 10, or 60 min. Both tin and fluoride were identified on the surfaces. The concentration varied depending on the extensiveness of the treatment. Immersion in 1 M KOH for 15 h removed both tin and fluoride from the surfaces. This reaction was not observed after immersion in H2O for the same time period. Examination of the SnF2-treated dentin surfaces showed a dense layer of globular particles and in addition some larger particles. The dentinal tubules were totally covered even after the treatment with the lowest concentration of SnF2. Deposition of tin- and fluoride-containing globules on dentin surfaces may be of clinical interest. This layer may have importance both for the caries resistance of dentin and for hypersensitivity reactions.

Dental Caries↗

PubMedDate not supplied

Oral manifestations of familial hypophosphatemic rickets after phosphate supplement therapy: a review of the literature and report of case.

The patient was a seven-year-old boy with familial vitamin D-resistant hypophosphatemic rickets. His mother, and her mother, were also affected. Before phosphate treatment was introduced in the patient, an impaired incorporation of calcium, and its exchange with sodium, was thought to be the principal etiological factor in the formation of globules. Supplementation therapy then resulted in a less elevated Ca/P ratio in the root area of the affected teeth, as well as a cure for the boy's bone structure. What the therapy did not cure was the globular appearance of the dentin and the hypomineralized stripe of pulpal horn extending to the cusp tips, an apparent permanent outcome of the disease.

Abscess↗

PubMed1992

Morphological aspects of the resin-dentin interdiffusion zone with different dentin adhesive systems.

Cross-sections of resin-dentin interfaces were etched with an argon-ion beam to make their substructure detectable by scanning electron microscopy. The dentin adhesive systems were categorized morphologically into three groups, and an attempt was made to clarify their adhesive mechanism. The first group of products removed the smear layer. The argon-ion bombardment clearly disclosed a hybrid or resin-impregnated dentin layer. It is hypothesized that conditioning with acidic or chelating agents demineralized the dentin surface-layer to a certain depth, leaving behind a collagen-rich mesh-work. Hydrophilic monomers are then believed to alter this collagen-fiber arrangement in a way that facilitates penetration of the adhesive resin, resulting in a mechanical, intermingled link between collagen and the adhesive resin. The second group preserved the smear layer. In this case, the dentinal tubules were obliterated with globular particles at their orifices and remained patent underneath these smear plugs. This type of adhesive system aims at the incorporation of the smear layer into the hydrophilic monomers, which have an affinity for the organic and/or inorganic components of the underlying dentin. Finally, a third, small group only partly dissolved the smear layer, creating a thin resin-impregnated dentin layer and a resin-impregnated smear plug. This study clearly showed that the application of recent adhesive systems induced structural changes in the dentin surface morphology, creating a retentive interface, called the inter-diffusion zone, between the deep, untouched dentin layers and the composite filling material. This resin-dentin interdiffusion zone offers bonding sites for copolymerization with the resin composite and, concurrently, might have protective potential for the pulp tissues.

Acid Etching, Dental↗

PubMed1975

On the configuration of incremental lines in human dentine as revealed by tetracycline labelling.

The pattern of tetracycline labelling in dentine was investigated in ground sections of human teeth under visible and ultraviolet light. The tetracycline lines presented different appearances near the enamel-junction region, near the dentine-cementum junction, in the mantle dentine, and in the circumpulpal dentine, depending on whether the mineralization front was linear, globular or linear-globular.

Cementogenesis↗

PubMed2005

Single-bottle adhesives behave as permeable membranes after polymerisation. II. Differential permeability reduction with an oxalate desensitiser.

OBJECTIVES: This study examined the changes in hydraulic conductance and ultrastructure of dentine bonded with simplified etch-and-rinse adhesives to oxalate desensitiser pre-treated acid-etched dentine. METHODS: Human dentine disks were acid-etched, treated with an oxalate desensitiser (BisBlock, Bisco), and bonded with One-Step (OS), Single Bond (SB), OptiBond Solo Plus (OB) or Prime and Bond NT (PB). Similar disks from each group were acid-etched, and bonded without oxalate pre-treatment. Hydraulic conductance of the specimens was measured at 20 cm of water pressure and analysed with nonparametric statistical methods. Epoxy resin replicas of the smear layer-covered dentine and bonded dentine were examined with SEM for the extent of fluid transudation. Specimens bonded under perfusion were examined with TEM after tracer immersion. RESULTS: OB and PB exhibited a highly significant reversal of the reduced hydraulic conductance obtained with BisBlock on unbonded acid-etched dentine. Profuse water transudation across the bonded dentine was observed from the replicas. Adhesive interfaces were covered with spherical globules that interfered with dentine hybridization. Conversely, no significant difference in hydraulic conductance was observed in SB, between Bisblock pre-treated, unbonded and bonded acid-etched dentine. Significantly lower hydraulic conductance was shown on application of OS to Bisblock-treated acid-etched dentine. Water transudation was sparse, interfering surface globular structures were absent, and only angular subsurface crystals were seen in the dentinal tubules. CONCLUSIONS: Convective water fluxes through dentine may be reduced by applying Bisblock to acid-etched dentine before bonding with One-Step or Single Bond. However, reducing adhesive permeability with the use of oxalate desensitiser is not applicable to low acidity adhesives such as OptiBond Solo Plus and Prime and Bond NT.

Adhesives↗

PubMed1986

Scanning microscopy of platypus teeth.

Anorganic unerupted developing teeth and air-dried erupted teeth of the platypus (Ornithorhynchus anatinus) were examined in a scanning electron microscope and in a tandem scanning reflected light microscope. Typically mammalian developing fronts of enamel and dentine were identified in the anorganic unerupted specimens. The developing teeth were particularly small and fragile and the enamel elusive and difficult to examine in the normal way for morphological detail. Prepared fractured surfaces of unerupted specimens revealed preferentially oriented crystallite groups in the enamel generally perpendicular to the developing front and a highly globular, mineralized pattern in the dentine with fine diameter, sparsely distributed dentinal tubules. Although optically homogeneous, the enamel of both developing and mature teeth displayed well-defined incremental lines, radial clefts, crystallite domains of variable size and outline, and fine tubules when examined by high contrast, back-scattered electron imaging. The enamel is prismatic only in part; well-formed, regular prisms not being a primary feature of platypus enamel. This can be related to the variability inherent in the developing surface and the thinness of the enamel layer. No surface was found which could be confidently identified as cementum; those developing surfaces not covered by enamel displaying small calcospherites which elsewhere marked the outer aspect of the dentine.

Animals↗

PubMed1976

Structural changes in odontodysplasia.

Report is made of a histologic and scanning electron microscopic (SEM) study of teeth affected by odontodysplasia. The enamel was found to be thinner than normal, and the entire surface showed numerous depressions. The prismatic orientation, diameter, and density were found to be normal. Although the mantle dentin remained normal, the rest of this tissue showed a tendency to globular formation. The orientation, density, size, and shape of the dentinal tubules appeared to be normal. The cementum, in general, was normal, but in some instances appeared to be scalloped or globular. The pulp consisted of normal tissue but was found to be larger than normal. The presence of denticles was an outstanding feature.

Dental Enamel↗

PubMed1995

Providing an environment for reparative dentine induction in amputated rat molar pulp by high molecular-weight hyaluronic acid.

To study provision of this environment, wound healing was examined by light and electron microscopy following pulp amputation and direct capping with hyaluronic acid. Molar pulps of female Sprague-Dawley rats were mechanically exposed and directly capped; the cavities were then restored with glass-ionomer cement. As an experimental control. Calvital (a commercial preparation of calcium hydroxide paste) was used as the direct pulp-capping agent in other rats, and its effect on pulp healing was compared with that of hyaluronic acid. In hyaluronic acid-treated pulps, at 2 days after amputation, wound surfaces were covered with blood and fibrin clots and inflammatory cells such as neutrophils and macrophages. At 1 week, differentiation of fibroblastic and odontoblast-like cells was observed beneath the wound layer; and odontoblast-like cells produced globular calcified nodules along the existing dentine walls. At 2 weeks, a layer of reparative dentine had been formed by odontoblast-like cells over the dentine walls. Between 30 and 60 days, the formation of reparative dentine had extended throughout the pulp chamber. The healing observed after direct capping with hyaluronic acid was, except for the formation of dentine bridges, similar to that seen after Calvital capping. These results suggest that high molecular-weight hyaluronic acid can provide an environment suitable for reparative dentine formation through mesenchymal cell differentiation during healing of the amputated dental pulp.

Animals↗