Ruch J-V, Lesot H, Begue-Kirn C. Odontoblast differentiation. Initially, these cells seem to be non functional, but they may later constitute a reservoir for the renewal of old odontoblasts destroyed by apoptotic processes [30]. Anatomically, three are successive layers: 1- the cellular stratum (odontoblast cell bodies and Höehl’s cells [27], located at the periphery of the pulp), 2- the immature predentin layer, with a constant 15–20 micrometers thickness), and 3- the mineralized dentin, starting at the mineralization front up to the mantle dentino-enamel junction. (SPECIES). DSPP KO mice display tooth alterations that are very similar to the human dentinogenesis imperfecta type III [82]. The phosphate moieties of phosphoryn are the mediators of mineralization [86] since dephosphorylated DPP has no effect on in vitro mineralization [Milan AM, Sugars RV, Embery G, Waddington RJ. The general concept developed initially is that GAGs are most abundant in predentin and barely detectable in dentin. [25]. Thus MGP is also important as an inhibitor of dentin mineralization. The terminal polarization leads to the partition between i) a cell body where all the organelles implicated in ECM synthesis are present: rough endoplasmic reticulum, Golgi apparatus, immature and mature secretory vesicles, associated with lysosomal equipment (GERL, small and large lysosomal vesicles, multivesicular structures), and ii) a long process protruding in the predentin and adhering to the dentinal walls of the tubules. ECM molecules may also be implicated into cell signaling [58]. Association of bovine dentine phosphophoryn with collagen fragments. Dentin Sialophosphoprotein Knockout Mouse Teeth Display Widened Predentin Zone and Develop Defective Dentin Mineralization Similar to Human Dentinogenesis Imperfecta Type III. a. Inage T, Toda Y. Phosphoprotein synthesis and secretion by odontoblasts in rat incisor as revealed by electron microscopic radioautography. Bronckers AL, Price PA, Schrijvers A, Bervoets TJ, Karsenty G. Studies of osteocalcin function in dentin formation in rodent teeth. . In the maxilla in the median region, odontoblasts precursors migrate from the fronto-nasal bud. Adsorption and interactions of dentine phosphoprotein with hydroxyapatite and collagen. The circumpulpal dentin forms the largest part of the dentin layer. In addition to the dose dependency, the time period allowing interaction between the effectors and potential receptors is an important factor modulating the biological outcome. von Marschall Z, Fisher LW. Wang RZ, Weiner S. Strain-structure relations in human teeth using Moiré fringes. The question of the length of the process remains unanswered. Dentin tubules are missing or reduced in number and bent in these layers of outer dentin. Calcification is usually a non-physiologic event, mineralization is generally physiologic. J Dent Res. Vesicles containing abacus-like structures have been interpreted as being the mode of intracellular transfer of pro-collagen. Goldberg M, Septier D, Rapoport O, Iozzo RV, Young MF, Ameye LG. is expressed by odontoblasts and also found in predentin [ Ueno A, Yamashita K, Nagata T, Tsurumi C, Miwa Y, Kitamura S, Inoue H. cDNA cloning of bovine thrombospondin 1 and its expression in odontoblasts and predentin. [Qin C, D’Souza R, Feng JQ. Apical Foramen. DPP displays a C-terminal domain coding region sequence (a 244 residue sequence). Type I collagen is the major protein of intertubular dentin (90%), whereas no collagen fibrils are observed in the peritubular dentin. warfarin) causes secretion of a non-gamma-carboxylated BGP that does not bind to HA,, accumulates in bone and blocks ossification. osteocalcin) and for some members of the SLRPs family. Both the N-terminal and C-terminal fragments are HA nucleators, while the GAG-PG fragment is an effective inhibitor of HA formation and growth [Gericke A, Qin C, Sun Y, Redfern R, Redfern D, Fujimoto Y, Taleb H, Butler WT, Boskey AL. Dentine and pulp: their structure and reactions. The incorporation of [35S] sulfate into dentin PGs is stable in time and place. Slavkin HC, Croissant RD, Bringas P, Matrosian P, Wilson P, Mino W, Guenther W. Matrix vesicles heterogeneity: possible morphogenetic functions for matrix vesicles. As a Ca2++ binding protein, and a collagen-binding protein, SPARC may contribute indirectly to dentin mineralization, but this has to be confirmed. A RGD motif mediates cell attachment/signaling. Electron histochemical observation of ultra-thin Epon sections stained with a phosphotungstic acid/chromic acid mixture or using the “stains all” method with the light microscope show both stainings at the mineralization front. Dentin - Meaning, Development, Structure, Types and FAQs - Vedantu Dentin - an overview | ScienceDirect Topics The N-terminal region of DPP is distinct from other ECM proteins, however both. Kagayama M, Sasano Y, Tssuchia M, Watanabe M, Mizoguchi I, Kamakura S, Motegi K. Confocal microscopy of Tomes’s granular layer in dog premolar teeth. Therefore they were clearly not destroyed, but were thought to be enzymatically modified. Percentage of silver grains in odontoblasts, predentin and dentin [25], National Library of Medicine Calcium indirectly regulates immunochemical reactivity and functional activities of the N-domain of thrombospondin-1. Irving JT. It is however possible that the processes withdraw but some non-functional remnants of the process may remain, adhering to the tubule wall [31]. These chains are assembled in a triple helix with a coiled coil conformation [, Fibrillar growth is primarily due to the lateral self-assembly of fibril subunits, followed by a linear fusion implicated in collagen lengthening [, Collagen is synthesized and subsequently controlled by the odontoblasts. Mantle dentin is the outermost thin layer of dentin [] characterized by a low content of highly phosphorylated non-collagenous matrix proteins relative to that in circumpulpal dentin that comprises the rest of the bulk of mineralized dentin layers []. Bone SialoProtein (BSP) is also a candidate for playing a role in the vertebrate biomineralization process. They form an amorphous gel allowing the transportation/fibrillation of collagen fibrils moving from the proximal to the distal part of the predentin. In intertubular dentin, s form the plate-like crystallites, 2–5 nm in thickness and 60nm in length. Two unusual metalloproteinases that are essential for procollagen processing probably have important roles in development and cell signaling. The network of porosities, probably formed by organic remnants, is vertically oriented, and unrelated to the tubules [6]. Thyagarajan T, Sreenath T, Cho A, Wright JT, Kulkarni AB. Septier D, Hall RC, Embery G, Goldberg M. Immunoelectron microscopic visualization of pro- and secreted forms of decorin and biglycan in the predentin and during dentin formation in the rat incisor. However, the mutation does not produce a dentinogensis imperfecta or a dentin dysplasia but its effect is pronounced on X-link hypophosphatemic rickets and causes the occurrence of large interglobular spaces in circumpulpal dentin, filled with ECM molecules accumulating in these spaces instead of diffusing in the whole dentin. However, the thickness of the outer layer is about 200mm, therefore larger than the presumed width of the mantle dentin. Contour lines of Owen. . Firstly, the dentin outer layers result from cell-derived events involving the presence of matrix vesicles and their enzymatic equipment. Mantle dentin They are produced from the expression of genes located on chromosome 4 q21. Indeed radioautographic data evidence two distinct groups of GAGs in predentin and dentin. For years a sudanophilic band was reported to be present at the dentin-predentin junction, at the dentin edge [122, 123]. Kardos TB, Hubbard MJ. Such dentin may also be a physio-pathological response to the release of some components of dental material fillings, free-monomers of resins or silver amalgam containing mercury. Calcospherulites isolated from the mineralization front of bone induce the mineralization of type I collagen. It is not synthesized by odontoblasts, but may be found in dentin. The role of dentin ECM in dentin formation and mineralization, The publisher's final edited version of this article is available free at, Collagen is the major protein found in dentin. They display some elastic properties and therefore provide some resilience, important from a mechanical point of view and allowing dissipation of stress forces [7]. At some stage of maturation (probably when cross-links provide stability to the collagen fibrils), they are incorporated and immobilized in the forming circumpulpal dentin. There is a high probability that during the last 50 years, almost all the major dentin ECM molecules have been identified. Non-collagenous proteins are post-translationally modified by casein kinases (phosphorylation), protein phosphatases (dephosphorylation), BMP1 and PHEX (fragmentation), and sulfatases (sulfation).. Ca++ ions interact with the acidic residues and furthermore combine with PO4--- to initiate the nucleation process. They form a ring around the lumen of the tubules. Consequently dentinogenesis provides an excellent model to study the biomineralization processes of skeletal tissues. 2008 Apr 1;105(13):5266-70.] This observation may shed light on a processes shared by bone and dentin. As structural proteins, ECM molecules are implicated into the formation and mineralization of dentin. Dentin provides support to enamel, preventing enamel fractures during occlusal loading. They have been reported in the literature as “crystal ghosts”. Matrix Gla protein inhibition of tooth mineralization. They were further identified as CS/DS proteoglycans [45] and KS proteoglycans [46]. Lipophilia of enamel matrix—a chemical investigation of the neutral lipids and lipophilic proteins of enamel. Bone Sialoprotein. It took ~ 2h to see a significant labeling, above the background, in the cells and in predentin as well. Munhoz COG, Leblond CP. They are constantly interacting, up- or down- regulated by other ECM molecules . Genetically altered mouse models: the good, the bad, and the ugly. As a working hypothesis clarifying the cascade of events leading to mineralization in the collagen-based tissues, a series of steps have been indicated. Some confusion arises between osteocalcin and bone matrix gla protein (BGP). The possible occurrence of such cell-independent diffusion adds a third possibility to the two previously reported cell-controlled pathways. This dual secretion is supported by other experiments related to proteoglycans (PGs) incorporation within predentin and dentin. Dentin and mandibular bone hypomineralization was observed, together with a twisted appearance of enamel rods [119]. This region has been named DMP2 (dentin matrix protein 2), and this part is not phosphorylated. Some of them are characterized as matricellular molecules. This dentin is relatively? Höehl E. Beitrag zur histology der pulpa und des dentins. Along these lines, some crystallo-chemical specificities of the inter- and peri-tubular dentins have been established. In bone, MEPE appears to be an inhibitor of mineralization as the MEPE null animal is hypermineralized. Often, terminology is not always used in a proper way. Teeth contain in their central parts dental pulps, which are usually non-mineralized. One important concept in this chapter involve the cells in (or near) dentin. Depending of the labeled precursor, secretion either occurs in the proximal predentin or at the distal predentin- inner dentin edge. Genetic evidence for key roles of decorin and biglycan in dentin mineralization. The interaction of bovine dentine phosphophoryn and collagen during fibrillogenesis of collagen in vitro. The functions of these peripheral layers have not been clearly established. Abstract. Hall R, Septier D, Embery G, Goldberg M. Stromelysin-1 (MMP-3) in forming enamel and predentine in rat incisor – coordinated distribution with proteoglycans suggests a functional role. Tartaix PH, Doulaverakis M, George A, Fisher LW, Butler WT, Qin C, Salih E, Tan M, Fujimoto Y, Spevak L, Boskey AL. The formation of peritubular dentin result from intercellular diffusion. Dentin is a bone-like tissue, consisting of collagen fibrils reinforced with carbonated hydroxyapatite particles. More over, mineralization was absent in tooth root dentin and cellular cementum, while crown dentin showed “breakthrough” areas of mineralization. Sreenath T, Thyagarajan T, Hall B, Longenecker G, D’Souza R, Hong S, Wright JT, MacDougall M, Sauk J, Kulkarni AB. The concomitant formation of inter- and peri-tubular dentin results from two different type of mineralization. The first data obtained with the Transmission Electron Microscope after heart perfusion of the fixative solution established that in the cat, processes are located in the inner third, and never extended more than half distance between the pulp and the DEJ. In the crown, the so-called mantle dentin, indentation measurements using Vickers microhardness show a gradual increase in hardness along the outer 200mm [7]. Dentin sialoprotein and dentin phosphoprotein have distinct roles in dentin mineralization. This cascade of events corresponds firstly to the synthesis of procollagen fibrils in odontoblasts cell bodies. The formation of circumpulpal dentin occurs in a three compartments model: odontoblast cell bodies, predentin and dentin. They are located either at the surface the collagen fibrils, and parallel withthe collagen fibril axis; the crystallites randomly fill interfibrillar spaces [19]. Interactions between ECM molecules, the role of specific domains exposed after cleavage by proteases or matricryptic events, the occurrence of isoforms and the folding of ECM molecules pave the way for a better understanding, and therefore mimicking of the process of mineralization. The role of other dentin ECM molecules is more ambiguous, either because they are ubiquitous molecules, or because they act as mineralization inhibitors in many biological models. Bone Morphogenetic Protein-1/Tolloid-like proteinases process Dentin Matrix Protein-1. Reactionary dentin is different from what is named reparative dentin. From a structural point of view, dentin tubules are scarce in the mantle dentin, and lacking in many cases. Secondly, the active transformation of predentin into dentin is the origin of intertubular dentin formation. had extensive hypomineralization with amounts of unmineralized ECM from four- to eight-fold higher in dentin and alveolar bone when compared with that in wild-type tissues. Ushiyama J. Radioautographic data and experiments using microtubule inhibitors suggest the occurrence of flux of forces in predentin and the active transport of collagen fibrils from the proximal to the distal predentin where the mineralization process occurs [25]. The diameter in the proximal third of predentin of the fibrils is about 20 nanometers, 40 nanometers in the central third, and 55–75 micrometers in the distal part, near the mineralization front. Phospholipids, that may be removed chemically (chloroform/methanol or acetone) or enzymatically (phospholipase C) are located in predentin in inter-collagenic spaces, forming a continuous network. It is shown that the researched biological subjects have similar spectral composition and tooth dentin can be . However, in contrast to bone, there is little or no remodeling in dentin. These predentin PGs may constitute a substrate for stromelysin (MMP-3). Six genes expressed in bones and teeth encode the current members of the SIBLING family of proteins. It is also possible that the postponed modification of predentin components into dentin also delays the mineralization process. Because similar molecules are present in bone and dentin, they may have the same function. These junctional complexes constitute a solid permeability membrane, and intercellular diffusions are restricted to molecules with small molecular weight. TGF-. Yamakoshi Y, Lu Y, Hu JC, Kim JW, Iwata T, Kobayashi K, Nagano T, Yamakoshi F, Hu Y, Fukae M, Simmer JP. The OPN null mice did not have a detectable dental phenotype, and no other data are yet forthcoming to define a role of the molecule in dentinogenesis. Taken together, the silver grains, immunolabeling and histochemical staining of metadentin, at the dentin edge near the predentin, support this assumption. At lowermagnification, inter-tubular crystallites have a needle like appearance. The molecule is very similar to the Bone Acidic Glycoprotein (BAG75), although BAG75 is somehow heavier than the DMP1. It constitutes the body of teeth and is covered by a hard enamel layer. Reactionary dentin appears either as a layer of the osteodentin type, or as a tubular or atubular orthodentin, depending the speed and severity of the carious attack, the progression of the reaction and the age of the patient. Inter-tubular dentin results from the changes occurring between a dynamic non-mineralized predentin and the dentin located behind the mineralization front, a border that we now call metadentin [22]. Before During the period of migration the pre-odontoblasts proliferate and a fixed number of divisions allows these cells to reach the periphery of the dental pulp. DMP-1 mutation is important in an autosomal-recessive form of hypophosphatemic rickets. In the root, inter-odontoblastic collagen fibrils, the so-called von Korff fibrils, are also oriented also at right angles to the dentin inner surface. J Dent Res. Large amorphous dots of phospholipids/malachite green/aldehyde complexes are also stained within dentin. Biochem J. Reports in the literature suggest that locally produced levels of OCN are not sufficient to influence dentinogenesis [107]. The non-phosphorylated recombinant protein acts as a HA nucleator. Autoradiographie de la dentinogenèse en microscopie électronique à l’aide de proline tritiée chez le rat. This labeling is stable and remains even after longer periods of time. To summarize this section, DPP or phosphophoryn appears as candidate to be implicated in intertubular dentin mineralization. There is also a GAG-glycosamino glycan (chondroitin sulfate) containing fraction [Qin C, Huang B, Wygant JN, McIntyre BW, McDonald CH, Cook RG, Butler WT. Baker SM, Sugars RV, Wendel M, Smith AJ, Waddington RJ, Cooper PR, Sloan AJ. Circumpulpal dentin forming the bulk of the tooth, comprises intertubular and peritubular dentin. Therefore, it was assumed that these acidic phospholipids are specifically associated to the mineralization phase. However, some hypothesis may be drawn from their physical and chemical -chemical properties. Emphasis has more recently been placed on the specific properties of specific domains of the molecule, which are exposed or hidden in some presentations of the molecule Many of the ECM proteins are intrinsically disordered [Tompa P. Structure and Function of Intrinsically Disordered Proteins, CRC Press, Boca Raton, FLA, 2009], having flexible structures that vary as they interact with their miscellaneous partners (other proteins, enzymes, mineral). Ogbureke KU, Fisher LW. Calcified tissue that is not as hard as enamel but harder than cementum. Weinstock M, Leblond CP. This enzyme hydrolyzes pyrophosphate and provides inorganic phosphate to promote mineralization [113].. Other enzymes also play a role in odontogenesis. The labeling seen throughout dentin was reinforced at 1h. DPP causes nucleation at low concentrations, and inhibition of crystal growth at high concentrations [. Light and electron microscopy histochemical methods established the presence of glycosaminoglycans (GAGs) in predentin and dentin [39]. Gorter de Vries I, Quartier E, Boute P, Wisse E, Coomans D. Immunocytochemical Localization of Osteocalcin in Developing Rat Teeth. 2010 Apr;89(4):355-9.] Synthesis, migration and release of precursor collagen by odontoblasts as visualized by radioautography after 3H-proline administration. They follow mainly an intercellular pathway, albumin and phospholipids being implicated in the transport of mineral toward and therefore in the mineralization process of intertubular dentin. They are aligned in strands, which may contribute to the gradual reduction in diameter of the root [, Altogether, it is clear that collagen fibrils are important in dentinogensis mostly by providing an organized scaffold. Mantle dentin is the first dentin deposited; circumpulpal or primary dentin constitutes the bulk of the tooth. Goldberg M, Feinberg J, Lecolle S, Kaetzel MA, Rainteau D, Lessard JL, Dedman JR, Weinman S. Co-distribution of annexin VI and actin in secretory ameloblasts and odontoblasts of the rat incisor. In vertebrates,, biomineralization The conclusion drawn at that time was that GAGs are mineralization inhibitors and must be removed by cleavage followed by subsequent degradation at place where mineralization should be initiated. Acellular cementum was missing in these animals,, and unmineralized osteodentin formed within the pulp. Suzuki S, Sreenath T, Haruyama N, Honeycutt C, Terse A, Cho A, Kohler T, Müller R, Goldberg M, Kulkarni AB. In dentin, the SIBLING family includes DSPP, immediately cleaved after secretion into DSP, DGP and DPP. Some signals are derived from biologically active cryptic sites, revealed after conformational alterations of the molecule. This is due to the proteolytic cleavage by BMP-1/Tolloid-like proteinases into NH2-terminal sequence [93]. Processes are also implicated in the re-internalization of some fragments after the degradation of some ECM molecules. Zones of dentin have structural differences. The same staining pattern is seen with “Stains All” (9). Different forms of DMP1 play distinct roles in mineralization. The same features were detected in young fibromodulin (Fmod) -deficient mice (newborn and up to 21 day-old mice). Introduction. The polyaspartate-containing OPN extracted from one is a mineralization inhibitor that depends on its status phosphorylation Recombinant non-phosphorylated OPN and chemically dephosphorylated OPN have no effect on HA formation. When the localization of Phosphophoryn was examined by immunostaining,, light staining is observed over the odontoblasts and proximal processes. 2009 Oct;45(4):693–703.]. However, in the absence of NCP, collagen fibrils do not appear to be directly involved in mineralization, and in this context, only an association of bovine dentin phosphoprotein with collagen fragments is effective [. Evidences for a potential role of PGs in dentin mineralization are supported by in vitro studies demonstrating the capacity of biglycan to initiate crystal nuclei [117] and by observations carried out in vivo on biglycan, decorin and fibromodulin KO mice [23,24]. A limited number of reports are focusing on the effects of BSP on reparative dentinogenesis [refs]. In contrast, in the mineralized dentin, the diameter of the collagen fibrils is stable. It can have both positive and negative outcomes and among many examples includes ectopic calcification, vascular calcification and kidney stone formation. The molecule consists of 300 amino acids, plus a 17amino acids signal peptide. Frontiers | Enamel and dentin in Enamel renal syndrome: A confocal ... The second group of small PGs is secreted near the predentin-dentin junction and is apparently associated with the mineral phase. Together these anhydrous sites contribute to the initiation and growth of a mineral phase. Its molecular weight is about 38 and 35 kDa in ???? Later, the band is covered by the dentin newly formed during the next 48h and more, which is not labeled. We have observed a reverse situation in predentin, where the collagen fibrils in the Fmod- deficient mice have an increased diameter, as it was the case for BGN-KO mice [24]. BSP is characterized by the repetition of several polyglutamic acid segments and by a arginine- glycine- aspartate (RGD) motif that mediates cell attachment. With a molecular weight of 53.5 kDa, DMP-1 possesses 93 serines and 12 threonines in the appropriate context for phosphorylation. The Dentinoenamel Junction | SpringerLink Thirdly, a passive deposit of serum-derived molecules along the tubule walls leads to the formation of peritubular dentin. Reduced expression of dentin sialophosphoprotein is associated with dysplastic dentin in mice overexpressing transforming growth factor-beta 1 in teeth. The site is secure. In the root, similar layers are identified as follows 1) a Tomes granular layer, formed by calcospheritic structures that have not fully merged, and consequently by interglobular spaces, and/or 2) the hyaline Hopewell-Smith layer, each 15 – 30 micrometers in thickness. The dentin of the teeth of an adult human being contains about 28 percent organic matter, about 64 percent inorganic matter, and about 8 percent water. Initially, odontoblasts constantly produce matrix molecules that result in the formation of a 10 micrometers thick layer, reduced afterward to a daily 4 micrometers deposit. Dentin. Kawasaki K, Buchanan AV, Weiss KM. Torres-Quintana M-A, Lécolle S, Goldberg M. Effects of inositol hexasulphate, a casein kinase inhibitor on dentine phosphorylated proteins in organ culture of mouse tooth germs. DPP accounts for more than 50% of the NCP in most dentin. The molecular weight of this glycoprotein is 60–80 kDa, with high carbohydrate content reported to represent ~ 50% of the molecular weight. dentin [64]. official website and that any information you provide is encrypted However, this last type of so-called “dentin” does not result from the activity of odontoblasts or their associated cells, but specifically from pulp progenitors, implicated in the formation of a bone-like or in structure-less mineralization (pulp diffuse mineralization or pulp stones). In vitro apatite induction by phosphophoryn immobilized on modified collagen fibrils. Saito T, Yamauchi M, Abiko Y, Matsuda K, Crenshaw MA. However, it has been noted that their number is increased when secretion is impaired by pharmacological drugs such as vinblastine or others vinca alkaloids, or colchicines, a family of drugs that act on the polymerization of cytoskeletal proteins namely tubulin [, Procollagen non-helical extensions are cleaved by procollagen peptidases and the fibrils transformed into native collagen. Its molecular weight is about 100kDa in rat, bovine and porcine. The presence of stromelysin-1 (MMP-3) explains how the PD-PGs can be degraded and why they turnover so rapidly [42]. The growth of these crystals is also directed by the ECM proteins. Porcine dentin matrix protein 1: gene structure, cDNA sequence, and expression in teeth. The formation of inter-tubular dentin provides a unique three-layer model, very convenient to study matrix-derived mineralization. 2008 May 12;205(5):1145-53.]. DMP-1 is immunolocated predominantly at the mineralization front. Holland PWH, Harper SJ, McVey JH, Hogan BLM. A chondroitin sulfate chain attached to the bone dentin matrix protein 1 NH2-terminal fragment. Gotliv B-A, Robach JS, Veis A. However, this global distribution provides an oversimplified view, because dentin is a puzzle of different types of dentin, reflecting different functions and bearing their own specificities. It also contains DMP-1, BSP, osteopontin and MEPE. These IDPs include osteopontin and bone sialoprotein [Fisher LW, Torchia DA, Fohr B, Young MF, Fedarko NS. TGF beta-1 downregulates DSPP expression (80A and 80B)In contrast, BMP-2 activates DSPP expression via NF-Y signaling [81]. Proteoglycans, lipids and other ECM proteins are implicated in the formation of a thin amorphous network, giving rise to a dense hypermineralized peritubular dentin. This was matter of contention, because GAGs or PGs were identified in the mineralized compartment. Abstract The results of comparative spectral assessment of circumpulpal and mantle dentin and possibility of their further use for making bone substitute materials in dental surgery and implantology are presented in the work. Some matrix components migrate directly from the serum to the dentin compartment. Two von Korff fibres were not only visible in mantle dentine but also in circumpulpal dentine. This clearly shows that the band seen at the mineralization front is not resulting from the transformation of a labeled predentin into dentin, but that there are concomitantly two secretory places where labeled molecules are released. In the proximal predentin (near the cell bodies) the mean diameter of collagen fibrils is about 20nm, whereas in the central part the mean diameter reaches 40nm, and in the distal part, near the mineralization front, fibril diameter vary between 55–75nm [25]. 2010 Apr 9. The number of dentine tubules is about 18 000 and 21 000 tubules per mm2 [5]. When analyzing the phenotype of Dspp−/− Dcn −/−, the enlarged predentin found in the Dspp KO is rescued by the absence of DCN. Dentin Basic Structure, Composition, and Function It is still unclear if odontoblasts processes are involved or not in the second flux of secretion. Spontaneous precipitations of mineral complexes may also occur, but in general not in an apatitic form. Four events then occur: 1) The migration of the Golgi apparatus from the basal part to a supra-nuclear area, 2) The development of cytoskeletal proteins, microtubules and cilium, actin microfilaments, and vimentin and nestin-containing intermediate filaments.
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