Dental morphology and variation in theropod dinosaurs: implications for the taxonomic identification of isolated teeth.
Isolated theropod teeth are common Mesozoic fossils and would be an important data source for paleoecology biogeography if they could be reliably identified as having come from particular taxa. However, obtaining identifications is confounded by a paucity of easily identifiable characters. Here we discuss a quantitative methodology designed to provide defensible identifications of isolated teeth using Tyrannosaurus as a comparison taxon. We created a standard data set based as much as possible on teeth of known taxonomic affinity against which to compare isolated crowns. Tooth morphology was described using measured variables describing crown length, base length and width, and derived variables related to basal shape, squatness, mesial curve shape, apex location with respect to base, and denticle size. Crown curves were described by fitting the power function Y = a + bX(0.5) to coordinate data collected from lateral-view images of mesial curve profiles. The b value from these analyses provides a measure of curvature. Discriminant analyses compared isolated teeth of various taxonomic affinities against the standard. The analyses classified known Tyrannosaurus teeth with Tyrannosaurus and separated most teeth known not to be Tyrannosaurus from Tyrannosaurus. They had trouble correctly classifying teeth that were very similar to Tyrannosaurus and for which there were few data in the standard. However, the results indicate that expanding the standard should facilitate the identification of numerous types of isolated theropod teeth. (+info)
Human dental pulp cell culture and cell transplantation with an alginate scaffold.
Many studies on tissue stem cells have been conducted in the field of regenerative medicine, and some studies have indicated that cultured dental pulp mesenchymal cells secrete dentin matrix. In the present study we used alginate as a scaffold to transplant subcultured human dental pulp cells subcutaneously into the backs of nude mice. We found that when beta-glycerophosphate was added to the culture medium, dentin sialophosphoprotein mRNA coding dentin sialoprotein (DSP) was expressed. An increase in alkaline phosphatase, which is an early marker for odontoblast differentiation, was also demonstrated. At 6 weeks after implantation the subcutaneous formation of radio-opaque calcified bodies was observed in situ. Immunohistochemical and fine structure studies identified expression of type I collagen, type III collagen, and DSP in the mineralizing transplants. Isolated odontoblast-like cells initiated dentin-like hard tissue formation and scattered autolyzing apoptotic cells were also observed in the transplants. The study showed that subcultured dental pulp cells actively differentiate into odontoblast-like cells and induce calcification in an alginate scaffold. (+info)
Taurodontism of deciduous and permanent molars: report of two cases.
Taurodontism is an aberration of teeth that lacks the constriction at the level of the CEJ characterized by elongated pulp chambers and apical displacement of bifurcation or trifurcation of the roots, giving it a rectangular shape. Its occurrence in permanent teeth is common and is quite rare in deciduous dentition. Presented in this article are two cases with taurodontism involving deciduous and permanent molars. (+info)
Isolated rat dental pulp cell culture and transplantation with an alginate scaffold.
Many studies have been conducted on tissue stem cells in the field of regenerative medicine, and cultured dental pulp mesenchymal cells have been reported to secrete dentin matrix. In the present study we used alginate as a scaffold to transplant subcultured rat dental-pulp-derived cells subcutaneously into the back of nude mice. We found that when beta-glycerophosphate was added to the culture medium, the mRNA of the dentin sialophosphoprotein (DSPP) gene coding dentin sialoprotein (DSP) and dentin phosphoprotein (DPP) was expressed, and an increase in alkaline phosphatase, an early marker of odontoblast differentiation, was also demonstrated. Six weeks after implantation, subcutaneous formation of radiopaque calcified bodies was observed in situ. Immunohistochemical and fine structure studies identified expression of type I collagen, type III collagen, and DSP in the mineralizing transplants, and isolated odontoblast-like cells began to form dentin-like hard tissue formation. Scattered autolyzing apoptotic cells were also observed in the transplants. The study showed that subcultured rat dental-pulp-derived cells actively differentiate into odontoblast-like cells and induce calcification in an alginate scaffold. (+info)
Stimulatory effects of hydroxyl radical generation by Ga-Al-As laser irradiation on mineralization ability of human dental pulp cells.
The present study was conducted to investigate the effects of Ga-Al-As laser irradiation on the mineralization ability of human dental pulp (HDP) cells. HDP cells in vitro were irradiated once with a Ga-AL-As laser at 0.5 W for 500 s and at 1.0 W for 500 s in order to investigate free radicals as one mechanism for transmission of laser photochemical energy to cells. Production of the hydroxyl radical (*OH) was measured using the ESR spin-trapping method and was found to be increased by laser irradiation. The DMPO-OH was not detected in the presence of dimethyl sulfoxide (DMSO), a *OH scavenger. The formation of calcification nodule was also investigated by von Kossa staining. The number of calcified nodules was increased by 1.0 W-laser irradiation. Alkaline phosphatase (ALP) activity was higher in the 1.0 W-laser irradiation group. Expression of mRNAs for heat shock protein 27, bone morphogenetic proteins (BMPs) and ALP were greater in the 1.0 W-laser irradiation group. Expression of BMPs in the conditioned medium was also higher in the 1.0 W-laser irradiation group. In particular, DMSO decreased the number of calcified nodule produced by 1.0 W-laser irradiation. These results supposed that the mineralization of HDP cells is stimulated by laser irradiation, and that *OH generated by laser irradiation is a trigger for promotion of HDP cell mineralization. (+info)
Radiological and microscopic aspects of the denticles.
In this paper we have realized a study on 43 patients on which the retro-alveolar radiological exam has shown the existence of a calcareous structure within the pulp chamber having in view a better knowledge of this structure and its etiology, way of forming and pathological implications. For 16 of the patients the radiological exam was supplemented by a microscopic examination. Radiologically, the denticles were noticed more often in the pulp chamber of the molars. The examination of the histological samples has evidenced aspects such as the size, shape and structure of the denticles. The concentric disposition of the tissue elements shows that in the formation of a denticle there is a "center" around which a conjunctive substance avid of calcium salts is deposited. The microscopic aspects noticed on large denticles allowed us to sustain the hypothesis that in a large pulp chamber many denticles form simultaneously and grow up and merge generating a large-sized unique calcareous structure. (+info)
A dentin sialophosphoprotein mutation that partially disrupts a splice acceptor site causes type II dentin dysplasia.
Histological changes in human dental pulp following application of intrusive and extrusive orthodontic forces.
The aim of this study was to compare the effects of orthodontic extrusive and intrusive forces on histological changes of the human dental pulp. In this clinical trial, 52 sound upper first premolars from 26 patients scheduled for extraction for orthodontic reasons were selected. They were divided into 2 groups, based on the time intervals for histological evaluation (3 days and 3 weeks). In each group, 10 teeth received orthodontic extrusive forces, 10 teeth underwent intrusive forces, and 6 teeth served as controls. After each period, teeth were extracted and prepared for histological examination under light microscopy and some histological parameters were evaluated. The data were statistically analyzed by Kruskall-Wallis and Mann Whitney tests. Of the parameters evaluated, just vacuolization and disruption of the odontoblastic layer showed statistically significant differences between the control group and both of the experimental groups in each test period (P < 0.05). Additionally, there was no significant difference between 3-day and 3-week intervals in each experimental group, except for fibrosis in the extrusive group which significantly increased after 3 weeks of force application (P = 0.001). Histological pulp changes following extrusive and intrusive force applications for 3 days and 3 weeks show no difference from each other. (+info)