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PubMed2000

Tubular contents of equine dentin: a scanning electron microscopic study.

The dentinal tubules of 20 permanent equine incisors were investigated by scanning electron microscopy. Occlusal surfaces and longitudinal fracture planes of both etched and undecalcified teeth were examined. Three different types of structure were observed inside the dentinal tubular lumen. Odontoblastic processes could only be visualized in the circumpulpal parts of the tubules. The more peripheral parts were empty or housed cylindrical structures that probably correspond to the laminae limitantes. Collagen fibres were frequently observed in the tubular lumina and were most numerous in the circumpulpal parts of the tubules.

Acid Etching, Dental↗
PubMed2001

Endogenous Msx1 antisense transcript: in vivo and in vitro evidences, structure, and potential involvement in skeleton development in mammals.

Msx1 is a key factor for the development of tooth and craniofacial skeleton and has been proposed to play a pivotal role in terminal cell differentiation. In this paper, we demonstrated the presence of an endogenous Msx1 antisense RNA (Msx1-AS RNA) in mice, rats, and humans. In situ analysis revealed that this RNA is expressed only in differentiated dental and bone cells with an inverse correlation with Msx1 protein. These in vivo data and overexpression of Msx1 sense and AS RNA in an odontoblastic cell line (MO6-G3) showed that the balance between the levels of the two Msx1 RNAs is related to the expression of Msx1 protein. To analyze the impact of this balance in the Msx-Dlx homeoprotein pathway, we analyzed the effect of Msx1, Msx2, and Dlx5 overexpression on proteins involved in skeletal differentiation. We showed that the Msx1-AS RNA is involved in crosstalk between the Msx-Dlx pathways because its expression was abolished by Dlx5. Msx1 was shown to down-regulate a master gene of skeletal cells differentiation, Cbfa1. All these data strongly suggest that the ratio between Msx1 sense and antisense RNAs is a very important factor in the control of skeletal terminal differentiation. Finally, the initiation site for Msx1-AS RNA transcription was located by primer extension in both mouse and human in an identical region, including a consensus TATA box, suggesting an evolutionary conservation of the AS RNA-mediated regulation of Msx1 gene expression.

Amino Acid Sequence↗
PubMed1996

The carboxyl-terminal domain of phosphophoryn contains unique extended triplet amino acid repeat sequences forming ordered carboxyl-phosphate interaction ridges that may be essential in the biomineralization process.

Phosphophoryns (PPs), a family of Asp and Ser(P)-rich dentin proteins, are considered to be archetypal regulators of several aspects of extracellular matrix (ECM) biomineralization. We have cloned a rat incisor PP gene, Dmp2, from our odontoblast cDNA library and localized it to mouse chromosome 5q21 within 2 centimorgans of Dmp1, another tooth-specific ECM protein. The carboxyl-terminal region of Dmp2 protein (60 residue % Ser, 31 residue % Asp) is divided into two domains, one with unique repetitive blocks of [DSS]n,3</=14, the other with [SD]m = 2,3. Conformational analysis shows the phosphorylated form of the [DS*S*]n repeats to have a unique structure with well defined ridges of phosphates and carboxyls available for counter ion binding. The [S*D]m domains have different phosphate and carboxylate interaction edges and thus different calcium ion and apatite surface binding properties. These two domains and the colocalization of Dmp1 and Dmp2 genes at a position equivalent to the dentinogenesis imperfecta type II location on human 4q21 all suggest that the PPs are indeed involved in some aspect of ECM mineralization.

Amino Acid Sequence↗
PubMed2004

Transcriptional regulation of dentin matrix protein 1 by JunB and p300 during osteoblast differentiation.

Dentin matrix protein 1 (DMP1) is an acidic noncollagenous protein localized specifically in the mineralized matrix of bone and dentin. Expression analyses demonstrate that DMP1 is differentially regulated in osteoblasts and odontoblasts. Earlier we have reported on the transcriptional regulation of DMP1 by c-Fos and c-Jun (AP-1) transcription factors. Results from earlier study indicate that c-Fos and c-Jun play an important role in early osteoblast differentiation, whereas they do not have a significant effect on the terminally differentiated osteoblasts. In this paper, we demonstrate a regulatory mechanism by which JunB transcriptionally controls the expression of DMP1 during osteoblast differentiation. The cooperative interaction of JunB with p300 has been shown to dramatically modulate the DMP1 promoter activity during mineralization. Immunoprecipitation and chromatin immunoprecipitation analysis demonstrate the interaction of JunB and p300 in vivo. Further, phosphorylation of JunB at Ser-79 was found to be essential for its interaction with p300. Intrinsic histone acetyltransferase activity of p300 also plays a critical role in regulating DMP1 gene expression.

3T3 Cells↗
PubMed1998

Physical, chemical, and histologic changes in dentin caries lesions of primary teeth induced by regular use of polyol chewing gums.

A previous clinical trial showed that long-term use of saliva-stimulating polyol (xylitol and sorbitol) chewing gums was associated with arrest of dental caries in young subjects. After a 20-22-month intervention (when the subjects were 8 years old), a total of 23 primary teeth with extensive dentin caries lesions whose surface in clinical examination was found to be totally rehardened (remineralized) could be removed because the teeth were near their physiologic exfoliation time. These teeth were subjected to histologic, microhardness, and electron microscopic tests. The majority of the specimens had been remineralized from the surface by a non-cellular-mediated process within the remaining collapsed, organic extracellular matrix associated with the remaining dentinal surface. Many of the underlying dentinal tubules were filled with a matrix that had been subsequently mineralized. Dental microanalyses showed that the topmost (outer) 20-microm-thick rehardened layer of the lesions exhibited the highest Ca:P ratio, which leveled off at a depth of approximately 150 microm. The rehardened surface layer (normally <0.1 mm in thickness) was significantly (P < 0.001) harder than sound dentin and nearly as hard as sound enamel. Although the main source of the mineral present in the rehardened layer was most likely of salivary origin, some extracellular remineralization was probably mediated by odontoblasts. The results complete the dinical diagnoses of the original trial and suggest that regular use of polyol chewing gums may induce changes in dentin caries lesions, which in histologic and physiochemical studies show typical characteristics of rehardening and mineralization.

Calcium↗
PubMed2002

Cross-talk between Msx/Dlx homeobox genes and vitamin D during tooth mineralization.

Rickets is associated with site-specific disorders of enamel and dentin formation, which may reflect the impact of vitamin D on a morphogenetic pathway. This study is devoted to potential cross-talk between vitamin D and Msx/Dlx transcription factors. We raised the question of a potential link between tooth defects seen in mice with rickets and Msx2 gene misexpression, using mutant mice lacking the nuclear vitamin D receptor as an animal model. Our data showed a modulation of Msx2 expression. In order to search for a functional impact of this Msx2 misexpression secondary to rickets, we focused our attention on osteocalcin as a target gene for both vitamin D and Msx2. Combining Msx2 overexpression and vitamin D addition in vitro, we showed an inhibitory effect on osteocalcin expression in immortalized MO6-G3 odontoblasts. Finally, in the same cells, such combinations appeared to modulate VDR expression outlining the existence of complex cross-regulations between vitamin D and Msx/Dix pathways.

Animals↗
PubMed2002

Body weight in mouse embryos specifies staging of tooth development.

Great intra- and interlitter variation in morphological stages is known to exist among mouse embryos of the same strain at a similar chronological stage. With the aim of searching for an easily measurable parameter that correlates well with tooth development, the morpho- and histodifferentiation of teeth were compared in embryos classified according to the embryonic day (ED) specified by wet body weight. The embryos and fetuses were harvested at 12-h intervals from ED12.5 until birth, weighed, fixed, and processed histologically. The tooth age was determined according to the developmental progress of the first molar, evaluated based on morpho- and histodifferentiation criteria. The data documented a better correlation between tooth morpho-histodifferentiation with the age/weight staging than with only the embryonic day. The cyto-differentiation of odontoblasts exhibited a high interlitter variability and was similar within specimens of the same litter, regardless of their body weight differences.

Animals↗
PubMed2006

Molecular mechanisms of cytodifferentiation in mammalian tooth development.

The morphological stages of tooth development--bud, cap, bell, and terminal differentiation--have been known for decades. The past 10 years have seen the elucidation of many of the molecular events driving these morphogenetic stages. Signaling via the fibroblast growth factor (FGF), bone morphogenetic protein (BMP), hedgehog, and wingless protein families and their downstream transcription factors have been identified as key players in the epithelial-mesenchymal signaling loops driving tooth development. Currently the most complete description of the mechanisms in tooth development extends only through the cap stage. The body of work concerning the mechanisms directing the bell and cytodifferentiation stages is growing. This has mainly, but not exclusively, focused on the expression and effects of FGFs and BMPs in these latter stages, and is reviewed here. Additionally, recent results suggest that phenotypic proteins of both ameloblasts and odontoblasts, such as amelogenin and dentin matrix protein 2 may act as the final instructive signals in cytodifferentiation.

Ameloblasts↗
PubMed2003

Induction of reparative dentin formation by ultrasound-mediated gene delivery of growth/differentiation factor 11.

Bone morphogenetic proteins (BMPs) are morphogens implicated in embryonic and regenerative odontogenic differentiation. Gene therapy has the potential to induce reparative dentin formation for potential pulp capping. We have optimized the gene transfer of Growth/differentiation factor 11 (Gdf11)/Bmp11 plasmid DNA into dental pulp stem cells by sonoporation in vivo. Dental pulp tissue treated with plasmid pEGFP or CMV-LacZ in 5-10% Optison (Molecular Biosystems Inc., San Diego, CA) and stimulated by ultrasound (1 MHz, 0.5 W/cm(2), 30 sec) showed significant efficiency of gene transfer and high level of protein production selectively in the local region, within 500 microm of the amputated site of the pulp tissue. The Gdf11 cDNA plasmid transferred into dental pulp tissue by sonoporation in vitro, induced the expression of dentin sialoprotein (Dsp), a differentiation marker for odontoblasts. The transfection of Gdf11 by sonoporation stimulated a large amount of reparative dentin formation on the amputated dental pulp in canine teeth in vivo. These results suggest the possible use of BMPs using ultrasound-mediated gene therapy for endodontic dental treatment.

Animals↗
PubMedDate not supplied

Differentiation ability of rat postnatal dental pulp cells in vitro.

The current rapid progression in stem cell research has enhanced our knowledge of dental tissue regeneration. In this study, rat dental pulp cells were isolated and their differentiation ability was evaluated. First, dental pulp cells were obtained from maxillary incisors of male Wistar rats. Immunochemistry by stem cell marker STRO-1 proved the existence of stem cells or progenitors in the isolated cell population. The dissociated cells were then cultured both on smooth surfaces and on three-dimensional (3-D) scaffold materials in medium supplemented with beta-glycerophosphate, dexamethasone, and L-ascorbic acid. Cultures were analyzed by light and scanning electron microscopy and, on proliferation, alkaline phosphatase activity and calcium content were determined and the polymerase chain reaction was performed for dentin sialophosphoprotein, osteocalcin, and collagen type I. These cells showed the ability to differentiate into odontoblast-like cells and produced calcified nodules, which had components similar to dentin. In addition, we found that the "odontogenic" properties of the isolated cells were supported by three-dimensional calcium phosphate and titanium scaffolds equally well.

Animals↗
PubMed1992

Immunohistochemical localization of epidermal growth factor and its receptor during odontogenesis in the rat.

The expression of epidermal growth factor (EGF) and epidermal growth factor receptor (EGFr) in developing teeth has been immunohistochemically studied in rat embryos (E-16 to E-21). Both EGF and EGFr showed a similar pattern of distribution. A very weak immunostaining was observed in the dental germ cells during the bud, cap, and bell teeth stages, as well as in few ectomesenchymal cells. In developed, but not erupted teeth, a moderate immunoreactivity for EGF and EGFr was present in the odontoblasts, in the ameloblasts and in the internal epithelial cells, but it was stronger in the dentine. In addition, the presence of EGF/EGFr was also observed in the intercalated ducts of salivary glands, primarily the submaxillary gland, in the maxillary bone cells, and in the cells of the peripheral and central nervous system. These results suggest that EGF has little or no effect during the early periods of tooth differentiation, whereas it is probably involved in the production of dentine. Moreover, EGF/EGFr seem to participate in the maturation and differentiation of other embryonic tissues such as tissues of the nervous system and bone.

Ameloblasts↗
PubMed2003

Porcine enamel matrix derivative enhances the formation of reparative dentine and dentine bridges during wound healing of amputated rat molars.

We examined the biological effects of porcine enamel matrix derivative (EMD; Emdogain) on the formation of reparative dentine and dentine bridges in rat molars after pulp amputation. The pulp chambers of upper molars of Wistar rats were perforated and the amputated pulp surfaces were directly capped with either EMD or its carrier propylene glycol alginate (PGA) as control. The cavities were then restored with glass-ionomer cement. On post-amputation days 4-30, the dissected maxillae were examined by light and electron microscopy. In PGA-capped pulp, reparative dentine had been formed over the dentine walls under the prepared cavity on day 7 post-amputation and its thickness extended until day 30. On day 30, as well as reparative dentine formation, diffuse calcification had occurred beneath the amputated wound surfaces. Dentine bridge formation under the amputated coronal pulp surface was observed in 18.2% of amputated pulp on day 30. In EMD-capped pulp, reparative dentine had already been formed by odontoblast-like cells over the dentine walls, already on day 4 post-amputation, and its thickness extended until day 30. The Ca and P weight % and Ca/P ratio of reparative dentine matrix were similar to those of pre-existing dentine matrix, and these values were not different between PGA and EMD-capped pulp. Dentine bridge formation was observed in 27.3% of EMD-capped pulp on day 30. Our results suggest that EMD enhances the formation of both reparative dentine and dentine bridges during wound healing of amputated rat molar pulp.

Amputation, Surgical↗
PubMed1987

Anomalous growth of rat incisor teeth during chronic intermittent vitamin A deficiency.

Rapid, synchronous and repeating cycles of marginal retinoic acid sufficiency and deficiency were produced in rats by following an established protocol. During cycles 11-15 (343-464 days after weaning), 17 of 24 rats (71%) developed tumor-like masses in the connective tissue surrounding the formative ends of one or both upper incisor teeth. The masses were composed of cords of odontogenic epithelium surrounded by a mantle of mesenchyme. Lakes of predentine, associated with foci of keratinized epithelium, were randomly distributed. On the basis of current understanding of odontogenesis, we propose that periodically disturbed differentiation of pulpal mesenchymal cells to dentin-secreting odontoblasts was pivotal to development of the masses. During deficiency, dentin secretion is impaired, the dentin wall perforates and with time the odontogenic epithelium and pulp herniate into the surrounding connective tissues. We propose that the incisal masses arose because the pulpal mesenchyme continued to grow and its secretion product, dentine, continued to be deposited (during periods of vitamin A sufficiency) in an ectopic site where functional attrition from mastication could not occur.

Animals↗
PubMed2000

Immunohistochemical localization of tenascin, fibronectin, and type III collagen in human dental pulp.

The distribution of tenascin (TN), fibronectin (FN), and type III collagen (col III) in the extracellular matrix of the connective tissue of normal, inflamed, and hyalinized human dental pulp was studied by immunohistochemical staining with monoclonal antibodies against these molecules. TN, FN, and col III were present in all normal tissues studied. In areas of hyalinization only col III was observed. None of the molecules studied were seen in areas of inflammatory exudate. Strong staining for TN and FN was found in the periphery of all specimens analyzed next to the odontoblastic layer. We therefore conclude that TN, FN, and col III are present in the extracellular matrix of normal human dental pulp. TN, FN, and col III distribution in inflammatory and degenerative processes is different from that observed in normal human dental pulp.

Antibodies, Monoclonal↗
PubMed2001

Response of human pulpal tissue to orthodontic extrusive applications.

The aim of this study was to investigate histologically the human pulp response to orthodontic extrusive force applications. In group 1, 20 teeth were extruded with the use of a fixed sectional orthodontic appliance. In group 2, 20 teeth were extruded by means of 1/4-inch 4.5-oz elastics. The test periods were 10 and 40 days. None of the teeth in the groups showed any inflammatory reactions or reparative dentin formation at the test periods. Five teeth from the elastics group and two teeth from the sectional appliance group showed large and numerous pulp stones in the serial sections (17.5% of all cases). Seven teeth from the sectional appliance group and two teeth from the elastics group showed odontoblast aspiration into the dentin tubules (22.5%). The results of the study showed that the extrusive forces applied in this study did not cause significant pathological changes in human pulp tissue.

Adolescent↗
PubMed2001

An immunohistochemical study of osteoprotegerin in the human dental pulp.

This study investigated the expression of osteoprotegerin (OPG) in healthy and inflamed dental pulps. Histological sections 7 microm thick of 47 teeth, either caries-free or affected by gross caries, were used. Sections were stained with hematoxylin-eosin, and other sections of the same specimen were subjected to the avidin-biotin peroxidase complex immunohistochemical procedure for detection of OPG. The study focused on the coronal pulp that was divided into peripheral and central regions. In the peripheral pulp healthy and inflamed specimens showed high OPG immunoreactivity of the odontoblastic layer. When no inflammation was present in the central pulp OPG immunoreactivity was light. Fibroblasts and endothelial cells showed immunoreactivity ranging from none to intense. When inflammation was present in the central pulp the chronic inflammatory cells showed intense immunoreactivity.

Chi-Square Distribution↗
PubMed2003

Differential induction of apoptosis by capping agents during pulp wound healing.

Effects of capping agents on two waves of apoptosis during pulp wound healing were examined. After cavity preparation of rat molars, cavities were filled with calcium hydroxide, zing oxide eugenol cement, or 4-META/MMA-TBB resin (4MMT) and some were unfilled. One hour or 1 day after filling, we examined the distribution and the number of apoptotic cells by terminal deoxynucleotidyl transferase-mediated labeling (TUNEL) assay. One hour after filling, there were no differences in distribution patterns or the number of apoptotic odontoblasts among the four groups. One day after filling, we found differences in distribution patterns and the number of apoptotic pulp cells among the four groups. Especially in the 4MMT group, the distribution pattern of apoptotic cells was more broadly spread, and the number of apoptotic cells was significantly larger than those of other groups. These results suggest that capping agents may have an effect on pulp apoptosis and that 4MMT may actively induce apoptosis during pulp wound healing.

Acrylic Resins↗
PubMed2003

Histopathological study of dental pulp tissue capped with enamel matrix derivative.

The purpose of this study was to examine the histopathological response of dental pulp tissue to enamel matrix derivative (EMD) used as a pulp capping material. Thirty-two teeth from two mongrel dogs were divided into four equal groups. One group served as controls, and the others were used for deep Class V cavity preparation followed by direct pulp capping with enamel matrix derivative. The treated teeth were extracted after 1, 4, and 8 weeks and prepared for histopathological examination by light microscopy. All teeth prepared after 4 and 8 weeks demonstrated an increase in tertiary dentin, suggesting that enamel matrix derivative exerts a considerable influence on odontoblasts and endothelial cells of capillaries in dental pulp tissue. These results imply that enamel matrix derivative used as a pulp capping material may play a role in the calcification of dental pulp tissue.

Animals↗