Reduced expression of dentin sialophosphoprotein is associated with dysplastic dentin in mice overexpressing transforming growth factor-beta 1 in teeth.
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Transforming growth factor (TGF)-beta1 is expressed in developing tooth from the initiation stage through adulthood. Odontoblast-specific expression of TGF-beta1 in the tooth continues throughout life; however, the precise biological functions of this growth factor in the odontoblasts are not clearly understood. Herein, we describe the generation of transgenic mice that overexpress active TGF-beta1 predominantly in the odontoblasts. Teeth of these mice show a significant reduction in the tooth mineralization, defective dentin formation, and a relatively high branching of dentinal tubules. Dentin extracellular matrix components such as type I and III collagens are increased and deposited abnormally in the dental pulp, similar to the hereditary human tooth disorders such as dentin dysplasia and dentinogenesis imperfecta. Calcium, one of the crucial inorganic components of mineralization, is also apparently increased in the transgenic mouse teeth. Most importantly, the expression of dentin sialophosphoprotein (dspp), a candidate gene implicated in dentinogenesis imperfecta II (MIM 125420), is significantly down-regulated in the transgenic teeth. Our results provide in vivo evidence suggesting that TGF-beta1 mediated expression of dspp is crucial for dentin mineralization. These findings also provide for the first time a direct experimental evidence indicating that decreased dspp gene expression along with the other cellular changes in odontoblasts may result in human hereditary dental disorders like dentinogenesis imperfecta II (MIM 125420) and dentin dysplasia (MIM 125400 and 125420). (+info)
Displacement of the contents of dentinal tubules and sensory transduction in intradental nerves of the cat.
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Experiments were performed on anaesthetized cats to test the hypothesis that fluid flow through dentinal tubules is part of the mechanism involved in the transduction of pain-producing stimuli in teeth. In 11 animals, fluid flow through dentine and single- and multi-unit activity in intradental nerves were recorded simultaneously during the application of changes in hydrostatic pressure (-500 to +500 mm Hg) to exposed dentine. Seventeen A-fibres (conduction velocity (CV), 10.6-55.1 m s(-1)) were isolated that were pressure sensitive. The thresholds of these units in terms of dentinal fluid flow were in the range 0.3-2.1 nl s(-1) mm(-2) during outward flow from the pulp and 2.0-3.5 nl s(-1) mm(-2) during inward flow. All the units were more sensitive to outward than inward flow. Twenty-eight units (CV, 0.6-48.8 m s-1) were not pressure sensitive, and 12 of these had conduction velocities in the C-fibre range (< 2.5 m s(-1)). The velocities of the tubular contents were calculated by estimating the number and diameters of dentinal tubules exposed. At the threshold of single-fibre responses these velocities were in the range 31.7-222.9 microm s(-1) during outward flow 211.4-369.6 microm s-1 during inward flow. Repetitive pressure stimulation of dentine resulted in a progressive reduction in the evoked discharge, which was probably due to pulp damage. In seven animals, 10 single intradental nerve fibres were selected that responded to hydrostatic pressure stimuli and their responses to the application of hot, cold, osmotic, mechanical and drying stimuli to exposed dentine were investigated. With these stimuli dentinal fluid flow could not be recorded in vivo for technical reasons and was therefore recorded in vitro after completion of the electrophysiological recordings. With each form of stimulus, the discharge evoked in vivo was closely related to the flow predicted from the in vitro measurements. The results were therefore consistent with the hypothesis that the stimuli act through a common transduction mechanism that involves fluid flow through dentine. (+info)
Evolutionary modification of development in mammalian teeth: quantifying gene expression patterns and topography.
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The study of mammalian evolution often relies on detailed analysis of dental morphology. For molecular patterning to play a role in dental evolution, gene expression differences should be linkable to corresponding morphological differences. Because teeth, like many other structures, are complex and evolution of new shapes usually involves subtle changes, we have developed topographic methods by using Geographic Information Systems. We investigated how genetic markers for epithelial signaling centers known as enamel knots are associated with evolutionary divergence of molar teeth in two rodent species, mouse and vole. Our analysis of expression patterns of Fgf4, Lef1, p21, and Shh genes in relation to digital elevation models of developing tooth shapes shows that molecular prepatterns predict the lateral cusp topography more than a day in advance. A heterotopic shift in the molecular prepatterns can be implicated in the evolution of mouse molar, changing locations from which historically homologous cusps form. The subtle but measurable heterotopic shifts may play a large role in the evolution of tooth cusp topographies. However, evolutionary increase in the number of longitudinal cusps in vole molar has involved accelerated longitudinal growth and iterative addition of new cusps without changes in lateral cusp topography. The iterative addition of cusps after the establishment of lateral cusp topography may limit the independence of individual morphological features used in evolutionary studies. The diversity of mammalian molar patterns may largely result from the heterotopic and iterative processes. (+info)
Digital imaging of bone and tooth modification.
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Digital cameras are capable of producing images of cut marks and other three dimensional subjects comparable to those obtained from the scanning electron microscope (SEM). Until now, the SEM has offered unparalleled depth of field and surface rendition. SEM units are, however, expensive to acquire and maintain, and SEM image production is time-intensive. Furthermore, SEM images lack color and are often incapable of imaging bone modifications because of magnification and chamber size limitations. A digital imaging method for producing extremely high depth of field enlargements of three dimensional, sub-millimeter scale objects circumvents these problems. In our presentation we employ four case studies of hard tissue modification related to: (1) the origins of meat-eating in the human lineage; (2) evidence for cannibalistic behavior among Neanderthals; (3) pre-Columbian evidence of North American dentistry; and (4) the earliest evidence of cranial surgery in North America. Procedures for replica production, image-capture, and image enhancement are provided. The digital images produced are compared to those obtained with the SEM. Image processing software, a crucial component of this method, allows complete control of graphic data, making graphic fraud a larger threat than ever before. Issues in ethics stemming from the application of this technology to scientific analysis are considered. (+info)
Expression of class 3 semaphorins and neuropilin receptors in the developing mouse tooth.
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The semaphorins are a large family of secreted or cell-bound signals needed for the development of the nervous system. We compared mRNA expression of class 3 semaphorins (Sema3A, 3B, 3C and 3F) and their two receptors (Neuropilin-1 and -2) in the embryonic mouse first molar tooth germ (E10-18) by radioactive in situ hybridization. All genes showed distinct developmentally regulated expression patterns during tooth organogenesis. Interestingly, Sema3A and 3C were first detected in the early dental epithelium, and later both genes were present in the epithelial primary enamel knot, a putative signaling center of the embryonic tooth regulating tooth morphogenesis. Prior to birth, Sema3A was also observed in tooth-specific cells, preodontoblasts, which later differentiate into odontoblasts secreting dentin, and in the mesenchymal dental follicle cells surrounding the tooth germ. Sema3B appeared transiently in the dental mesenchyme in the bud and cap stage tooth while Sema3F was expressed in both epithelial and mesenchymal components of the tooth. Of note, Npn-1 expression pattern was largely complementary to that of Sema3A, and transcripts were restricted to the dental mesenchymal cells. Npn-1 expression was first seen in the developing dental follicle, and later transcripts also appeared in the dental papilla mesenchyme. In contrast, Npn-2 signal was seen in both epithelial and mesenchymal tissues such as in the primary enamel knot and preodontoblasts. (+info)
Cell-specific patterns of Cbfa1 mRNA and protein expression in postnatal murine dental tissues.
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Cbfa1 (core binding factor alpha 1) is a transcription factor that is a key determinant of the osteoblastic lineage. Recent data showed that Cbfa1 is also highly expressed in early stages of tooth development and is involved in crown morphogenesis and cytodifferentiation of odontoblasts. Here we report the mRNA expression and protein localization of Cbfa1 in the mouse dentition in (later) stages of crown and root development. In addition to osteoblasts, osteocytes, chondrocytes, odontoblasts, dental follicle cells, cementoblasts and periodontal ligament cells, we report also Cbfa1 expression in dental epithelial cells (secretory and maturation ameloblasts) and several non-mineralizing cell types (hair follicles, ducts of salivary glands, and junctional epithelium of the gingiva). (+info)
Anatomical appraisal of the skulls and teeth associated with the family of Tsar Nicolay Romanov.
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This article describes the identification of skeletal remains attributed to the family of Tsar Nicolay Romanov and other persons buried together at a site near present-day Ekaterinburg, Russia. Detailed descriptions are given regarding the objective methods of craniofacial and odontological identification that were used. Employing computer-assisted photographic superimposition techniques and statistical analysis of morphologic and other characteristics of the specimens, this study identifies with a high likelihood of certainty the remains of the Tsar, his wife, three of his four daughters, and four household assistants. Very strong evidence is presented that the Tsar's daughter Anastasia was killed in 1918. This study demonstrates the effectiveness of the methods and trustworthiness of the results, as well as the prospects of future application of the methods for the identification of skeletonized human remains. Anat Rec (New Anat) 265:15-32, 2001. (+info)
Autogenous tooth transplantation: an alternative to dental implant placement?
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Autogenous tooth transplantation, or autotransplantation, is the surgical movement of a tooth from one location in the mouth to another in the same individual. Once thought to be experimental, autotransplantation has achieved high success rates and is an excellent option for tooth replacement. Although the indications for autotransplantation are narrow, careful patient selection coupled with an appropriate technique can lead to exceptional esthetic and functional results. One advantage of this procedure is that placement of an implant-supported prosthesis or other form of prosthetic tooth replacement is not needed. This article highlights the indications for autogenous tooth transplantation using 3 case reports as examples. A review of the recommended surgical technique as well as success rates are also discussed. (+info)