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PubMed2004

Post-translational modifications of sibling proteins and their roles in osteogenesis and dentinogenesis.

The extracellular matrix (ECM) of bone and dentin contains several non-collagenous proteins. One category of non-collagenous protein is termed the SIBLING (Small Integrin-Binding LIgand, N-linked Glycoprotein) family, that includes osteopontin (OPN), bone sialoprotein (BSP), dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP), and matrix extracellular phosphoglycoprotein (MEPE). These polyanionic SIBLING proteins are believed to play key biological roles in the mineralization of bone and dentin. Although the specific mechanisms involved in controlling bone and dentin formation are still unknown, it is clear that some functions of the SIBLING family members are dependent on the nature and extent of post-translational modifications (PTMs), such as phosphorylation, glycosylation, and proteolytic processing, since these PTMs would have significant effects on their structure. OPN and BSP are present in the ECM of bone and dentin as full-length forms, whereas amino acid sequencing indicates that DMP1 and DSPP exist as proteolytically processed fragments that result from scission of X-Asp bonds. We hypothesized that the processing of DMP1 and DSPP is catalyzed by the PHEX enzyme, since this protein, an endopeptidase that is predominantly expressed in bone and tooth, has a strong preference for cleavage at the NH2-terminus of aspartyl residue. We envision that the proteolytic processing of DMP1 and DSPP may be an activation process that plays a significant, crucial role in osteogenesis and dentinogenesis, and that a failure in this processing would cause defective mineralization in bone and dentin, as observed in X-linked hypophosphatemic rickets.

Amino Acid Sequence↗
PubMed1985

Localization of calcium in differentiating odontoblasts and ameloblasts before and during early dentinogenesis and amelogenesis in hamster tooth germs.

Potassium pyroantimonate-osmium tetroxide cytochemistry has been used to study the distribution of ionic calcium in hamster tooth germs during cell differentiation and during early dentinogenesis and amelogenesis. Before the onset of mineralization, pyroantimonate (PA) reaction product was found in the nucleus of differentiating preameloblasts and preodontoblasts. In the predentin, it was preferentially located along striated collagen fibrils, lying perpendicular to the basal lamina. At the onset of mineralization, a pronounced increase of PA reaction product was evident in the predentin and on the plasma membrane and in mitochondria of both preodontoblasts and preameloblasts opposite the mineralizing mantle dentin. During early enamel mineralization, PA reaction product was present in the "growing" crystal ends, while in the secretory ameloblasts, most of the PA reaction product was localized on the cytoplasmic side of the apical plasma membranes and in mitochondria. When Tomes' processes developed, PA reaction product, both cytoplasmic and membrane bound, was low or absent deep in the processes, but gradually increased toward the apical terminal web. A corresponding gradient of PA reaction product was observed on the opposing enamel crystallites. From this study we conclude that both preodontoblasts and preameloblasts seem to be involved in calcium acquisition necessary for the early stages of mantle dentin mineralization. Tomes' processes seem to regulate the entry of calcium into the enamel mineralization front.

Ameloblasts↗
PubMed1994

Altered collagen expression in human dentin: increased reactivity of type III and presence of type VI in dentinogenesis imperfecta, as revealed by immunoelectron microscopy.

We used transmission immunoelectron microscopy and polyclonal antibodies to study the reactivities of Types III and VI collagen in dentin of normal human permanent and primary teeth and in primary teeth from five patients with dentinogenesis imperfecta (DI) associated with osteogenesis imperfecta and occurring as a single trait. In the normal permanent tooth, reactivity of Type III collagen was occasional and, where present, peritubular. Staining of normal primary teeth was less occasional but still rare, whereas the abnormal dentin stained more uniformly. Atypical, non-striated fibrillar structures that also showed Type III collagen reactivity were observed in dentin of two of the three patients with DI as a single trait. Later, these two patients proved to be first cousins. Unlike antibodies to the N-terminal pro-peptide of Type I pro-collagen, antibodies to the C-terminal telopeptide of Type I collagen, used for comparison stained the affected dentin homogeneously. Reactivity of Type VI collagen, not detected in normal teeth, was seen in the dentin of all abnormal teeth, in association with non-fibrillar delicate material. This study also shows that although readily detectable in dentin affected by DI, Type III collagen is a minor constituent of normal human dentin matrix.

Collagen↗
PubMed1995

Effects of thyro-parathyroidectomy and parathyroidectomy upon dentinogenesis: Part II: Electron microscopy.

An ultrastructural study was carried out in order to better characterize the findings observed in the first part of our study. The materials and methods are the same as those used in the preceding paper. This study reveals the occurrence of structures which display a symmetrical cross-banded pattern within the predentin and dentin of thyro-parathyroidectomized (TPTX) and parathyroidectomized (PTX) rats. A difference in the distribution of the symmetrical banded structures as dentinogenesis advances, as well as differences in the amount of the symmetrical banded structures between TPTX and PTX rats were observed. The symmetrical banded structures correspond with the so-called symmetrical SLS previously described in the incisor of normal and pathologic rats. The occurrence of these structures at a given stage of the incisor development suggests that the odontoblast is sensitive to the parathyroid hormone deficiency and/or hypocalcemia in a precise stage of its maturation.

Animals↗
PubMed1995

Characterization of protein kinases involved in dentinogenesis.

Protein phosphorylation and dephosphorylation control many different cell functions as well as responses to internal and external signals. It has also been shown that highly phosphorylated acidic proteins have an important role in matrix mediated biomineralization, perhaps functioning as nucleators for crystal formation. Dentine phosphoprotein (DPP) is one of such proteins which is exclusively synthesized by the odontoblast cells and therefore a likely candidate to play a significant role in normal and abnormal dentine biomineralization. These studies are directed at characterizing the protein kinases involved in dentinogenesis and in particular the enzyme(s) responsible for DPP phosphorylation. In this report we present data which indicate that there are several different types of kinases in the odontoblast-enriched dental papilla mesenchyme (DPM), some of which can phosphorylate DPP, such as casein kinase I and II. However, a different DPP-kinase activity was identified. This enzyme(s) appears to be different from other reported kinases, and it is the only kinase that can phosphorylate both phosphorylated DPP and enzymatically dephosphorylated DPP.

Acid Phosphatase↗
PubMed1995

Evidence of two types of odontoblasts during dentinogenesis in elasmobranchs.

The fine structure of the odontoblasts in the sting rays, Dasyatis akajei, Dasyatidae, and Urolophus aurantiacus, Urolophidae, was examined using light and transmission electron microscopy. In the dentinogenesis stage, the odontoblasts have been classified into two types, that is, dark cells and light cells, based on differences in their fine structure. Many dark odontoblasts found along the predentine displayed well-developed organelles with secretory activity around the nuclei. They contained large amounts of expanded rER, widely distributed Golgi apparatus and secretory granules. In contrast, light odontoblasts showed a relatively clear cytoplasm and extended long processes which passed through the predentine and penetrated into the dentine. They contained large numbers of microtubules in the processes and many mitochondria around the nuclei. It is suggested that the light odontoblasts play an important part in material transport to the dentine and/or act as a sensory organ of the tooth. The dark odontoblasts seem to produce the organic matrix of the dentine and to prepare for mineralization in the dentine.

Animals↗
PubMed1996

Dentin matrix protein-1, a candidate gene for dentinogenesis imperfecta.

Dentinogenesis imperfecta (DGI) is an autosomal dominant inherited dental disease which affects dentin production and mineralization. Genetic linkage studies have determined linkage between DGI type II and group-specific component (Gc, vitamin D binding protein), interferon (gamma)-induced cytokine protein 10 (INP10) and secreted phosphoprotein 1 (SSP1, osteopontin, bone sialoprotein 1, early T-lymphocyte activation 1). Therefore, the gene locus has been localized to the long arm of human chromosome 4 in the region 4q13-q21. Dentin matrix protein-1 (DMP-1, AG-1) is a new acidic, phosphorylated dentin extracellular matrix protein which has recently been identified by cDNA cloning. The purpose of this study was to establish the possible association of DMP-1 with DGI type II by determining the human chromosomal localization of this protein. A DMP-1 DNA probe was generated1using PCR amplification of the mouse full-length DMP-1 and labeled with [32P] d-CTP. A panel of rodent somatic cell hybrid clones, previously cytogenetically characterized, was used for the assignment. High stringently DNA hybridization studies and analysis of the chromosomal cell panel indicated that the DMP-1 gene locus is located on human chromosome 4. This data supports the hypothesis that DMP-1 is a candidate gene for the genetic disease DGI type II. This is based on chromosomal localization to human chromosome 4, the expression of DMP-1 mostly by odontoblasts, and its purported physical-chemical properties.

Animals↗
PubMed1999

[Dentinogenesis imperfecta. Scanning electron microscopic study and microanalysis].

BACKGROUND: Dentinogenesis imperfecta (DI) is an inherited dentine defect which affects both the primary and secondary dentitions. Shields et al. in 1973 suggested a classification of DI within three types: type I, associated with osteogenesis imperfecta (OI), type II and type III. Although the varying clinical, radiographic and histological findings in DI have been described in detail, an available method for closer examination of the abnormal dentine matrix, electron microscopy, has seldom been used. Scanning and transmission electron microscopy studies can help to understand the pathogenesis of the different types of heritable dentine defects and the diagnosis and classification of these diseases. The aim of the present study was to evaluate a case of DI using scanning electron microscopy and microanalysis. METHODS: Dentine was obtained from tooth samples from a fourteen-year-old boy affected by DI and from third molars extracted for therapeutic reasons used as controls. Samples were observed with a scanning electron microscope, scanning electron micrographs were evaluated with an image analysis program and specimens were finally observed with a scanning electron microscope equipped for micro-analysis. RESULTS AND CONCLUSIONS: The results obtained showed that the total number of dentinal tubules was significantly reduced and the presence of a dentine mineralization defect in the patient affected by DI, in comparison to the controls.

Adolescent↗
PubMedDate not supplied

Dentinogenesis imperfecta: an early treatment strategy.

Dentinogenesis imperfecta (DI) type 2 is a disease inherited in a simple autosomal dominant mode. As soon as the teeth erupt the parents may notice the problem and look for a pediatric dentist's advice and treatment. Early diagnosis and treatment of DI is recommended, as it may prevent or intercept deterioration of the teeth and occlusion and improve esthetics. The purpose of this article is to present the objectives, treatment options, and problems encountered in the treatment of DI in the early primary dentition. A two-stage treatment of a toddler under general anesthesia is described and discussed. This paper recommends for severe cases of DI two treatment stages performed under general anesthesia. Stage 1 is early (around age 18-20 months) and is directed to covering the incisors with composite restorations and the first primary molars with preformed crowns. Stage 2 (around age 28-30 months) seeks to protect the second primary molars with preformed crowns and cover the canines with composite restorations.

Child, Preschool↗
PubMed2002

Odontoblast phosphate and calcium transport in dentinogenesis.

It has been suggested that odontoblasts are instrumental in translocating Ca2+ and inorganic phosphate (Pi) ions during the mineralization of dentin. The aim of this thesis was, therefore, to study the expression of components of the transcellular ion transport system, Na+/Ca2+ exchangers and Na(+)-Pi contransporters, in odontoblastic and osteoblastic cells. Their activity was assayed in osteoblast-like cells and in the recently developed MRPC-1 odontoblast-like cell line. To assess the relationship between ion transport and mineralization, Ca2+ and Pi uptake activities were determined in mineralizing cultures of MRPC-1 cells. Osteoblastic and odontoblastic cells showed an identical expression pattern of Na+/Ca2+ exchanger splice-variants, NCX1.3, NCX1.7 and NCX1.10, derived from the NCX1 gene, while NCX2 was not expressed. The cells showed a high sodium-dependent calcium extrusion activity. Regarding Na(+)-Pi cotransporter expression, Glvr-1, Ram-1 and the two high capacity cotransporters Npt-2a and Npt-2b were found to be expressed in odontoblasts and MRPC-1 cells. Osteoblast-like cells differed from this in expressing the Npt-1 but not the Ram-1 gene but were otherwise identical to the odontoblastic cells. Odontoblast-like cells exhibited almost twice the sodium-dependent Pi uptake activity of osteoblast-like cells. The presence of NaPi-2a and NaPi-2b, gene products of Npt-2a and Npt-2b, was verified in vivo by immunohistochemistry on mouse teeth. Both cotransporters could be detected in fully differentiated, polarized odontoblasts but not in preodontoblasts prior to dentin formation. Both cotransporters were detected in adjacent bone and in ameloblasts. Studying ion uptake in mineralizing MRPC-1 cultures, large changes were detected concomitant with the onset of mineral formation, when phosphate uptake increased by 400% while calcium uptake started to decline. The increase in Pi uptake was found to be due to activation of the NaPi-2a cotransporter. MRPC-1 cells expressed an odontoblast-like phenotype already at the onset of culture, but in order to form mineral a differentiation involving their ion transporters seems necessary. Calculating the theoretical rate of ion transport needed for dentin formation and comparing with data from the studies in this thesis showed that transcellular ion transport is both possible and sufficient to meet the phosphate and calcium demands of dentinogenesis.

Animals↗
PubMed2003

Dentinogenesis imperfecta associated with osteogenesis imperfecta: report of two cases.

Osteogenesis imperfecta (OI) is a heritable systemic disorder of the connective tissue. Dentinogenesis imperfecta (DI), which is sometimes an accompanying symptom of OI, belongs to a group of genetically conditioned dentin dysplasias and is characterized clinically by an opalescent amber appearance of the dentin. Although the teeth of DI cases wear more easily and excessively compared to normal teeth, they do not appear to be more susceptible to dental caries than normal teeth. Two cases of DI associated with OI are presented in this paper, with 1 case suffering from nursing bottle caries. The purposes of this paper are to present the dental and skeletal characteristics of moderately and mildly involved DI associated with OI, and to discuss the possible methods of dental treatment. Patients with OI and opalescent teeth should be evaluated as soon as the deciduous teeth erupt; immediate dental involvement and oral hygiene instruction can be of help in reducing the necessity of extensive dental care.

Child↗
PubMed1992

Investigation of the role of Von Korff fibers during murine dentinogenesis.

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.

Animals↗
PubMed1992

Calcium transport in dentinogenesis. An experimental study in the rat incisor odontoblast.

Since cellular calcium transport mechanisms during biological calcification are less known, a series of experiments were performed by in vivo as well as in vitro methodologies in the dentinogenically active rat incisor. By means of micro-electrode technique, the pH and pCa (calcium ion activity) in predentin in situ were found to be 7.0 and 2.9, respectively. It was concluded that there exists a Ca2+ion concentrating mechanism over the odontoblast layer in direction towards the mineralization front. The kinetics of this calcium flow was determined in vivo by radiotracer technique. The time for 45Ca2+ uptake into the dentin mineral phase was determined to 10-15 min. Transmembraneous Ca2+ ion pumps and channels in odontoblasts were further analyzed. The resting membrane potential of rat incisor odontoblasts was determined to -24 mV. Using ion-specific mini-electrode technique as well as fluorescence spectrophotometry, calcium channels, Ca(2+)-ATPase and Na+/Ca2+ antiports, responsible for cellular Ca2+ uptake and extrusion, were identified in the odontoblast plasma membrane. Dissected odontoblasts were subjected to subcellular fractionation. An electrophoretic uniporter and a Na2+/Ca2+ exchanger, for Ca2+ release and uptake, respectively, were demonstrated in mitochondria, whereas a Ca(2+)-ATPase was present in the microsomal fraction. Mitochondria, microsomes and whole, digitonin-permeabilized odontoblasts, were able to maintain a steady state Ca2+ activity at pCa = 6.4-6.6 in vitro. In rats treated with colchicine, the incorporation of 45Ca2+ into dentin mineral was severely altered. Similarly, administration to rats of specific calcium channel blockers strongly inhibited 45Ca2+ incorporation. Together, the results indicate that a transcellular pathway is a major route for Ca2+ ion transport during dentinogenesis, and that this may be under a relatively strict cellular control.

Animals↗
PubMed1992

Trimetaphosphatase activity in rat incisor odontoblasts during early dentinogenesis.

The ultrastructural localization of trimetaphosphatase activity have been investigated in early stages of dentinogenesis in the rat incisor. Extracellular reactive structures were present in between the odontoblasts during early secretion and absent later on. Tubular lysosomes were observed for the first time in odontoblasts and seemed to be involved with other elements of the lysosomal system in endocytosis of extracellular substances.

Acid Anhydride Hydrolases↗
PubMedDate not supplied

Hereditary dentinogenesis imperfecta: a treatment program using an overdenture.

The aim of treatment in cases of dentinogenesis imperfecta is to improve the esthetic appearance and maintain the oral masticatory apparatus in a healthy and functional state. In the growing child, it was decided to maintain the teeth for as long as possible under an overdenture, until such time when a permanent prosthetic solution can be decided upon.

Child↗
PubMed1992

Dentin extracellular matrix and dentinogenesis.

The formation of dentin involves secretion of matrix proteins by odontoblasts, prior to the deposition of apatite crystals. These matrix proteins probably play a role in transformation of predentin to dentin. The physical and chemical properties of dentin collagen, similar to those of bone, are especially adapted for binding matrix proteins and as a grid for mineral deposition. Phosphophoryns, polyanionic, and dentin-specific proteins are secreted at the mineralization front and are involved in some way in the mineralization process of circumpulpal dentin. Dentin sialoprotein is specifically made by odontoblasts and pulp cells and may be in the family of bone proteins known to promote cell attachment. Several proteins originally isolated from bone are also found in dentin and are expressed by odontoblasts. Although the mechanisms of dentinogenesis have not been elucidated, detailed studies of dentin matrix proteins should give valuable insights into this process.

Collagen↗
PubMed2006

Esthetic reconstruction of teeth in patient with dentinogenesis imperfecta--a case report.

Dentinogenesis imperfecta (DI) is the result of a dominant genetic defect and affects both the deciduous and permanent dentitions. It is characterized by opalescent teeth composed of irregularly formed and undemineralized dentin which obliterates pulp chamber and root canal. DI can appear as a separate disorder or with osteogenesis imperfecta (OI). The teeth with DI show a grayish-blue to brown hue with dislodged enamel, dysplastic dentine with irregular dentinal tubules and interglobular dentine, short roots and pulpal obliteration, which all may lead to rapid and extensive attrition which require adequate crown reconstruction. The aim of this study was to show a reconstruction of frontal teeth in upper jaw with direct composite veneers in young adult patient with DI.

Adult↗