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PubMed1986

The effect of aging on tooth morphology: a study on impacted teeth.

The effect of age on dental tissues was studied on histologic sections of totally impacted teeth obtained from patients between 11 and 76 years of age. Impacted teeth were used in order to obviate the influence of the environmental effects prevalent in the oral cavity. The presence of concentric denticles and diffuse calcifications was determined, and the width of secondary dentin, predentin, and cementum was measured. The width of predentin and cementum increased linearly with age, whereas the aging process of secondary dentin formation and diffuse calcifications followed a different pattern. The incidence of concentric denticles was identical for all age groups.

Adolescent↗
PubMed1978

Cementum-like bone production in solitary bone cysts. (so-called "cementoma" of long bones). Report of three cases. Electron microscopic observations supporting a synovial origin to the simple bone cyst.

Three cases of simple bone cysts (S.B.C) in association with cementum-like bone production are reported. Analysis of our cases and the 2 previously reported in the literature as so-called cementomas has led us to conclude that the "cementoma" of long bone is not a distinct entity, but merely, a form of S.B.C. associated with a peculiar, poorly cellular form of bone which mimics tooth cementum by light microscopy only. Electron microscopic studies of this substance demonstrate collagen fibers and numerous matrix vesicles which form the initial sites of calcification. Matrix vesicles are a product of osteoblastic activity and are never found in the cementum of the tooth or oral cementum producing tumors. We also report the first ultramiscroscopic observations on the wall of the simple bone cyst and its lining. Two cell types constitute the lining, having features identical to those described for type A and type B synovial cells. Because of this new observation, we believe, the most reasonable explanation for the simple bone cyst is that it represents a congenital "rest" of synovial tissue displaced into the thin, cortical metaphyseal region of bones at the synovial-capsularbone reflection. Its benign nature and slow growth would explain its discovery in early childhood and the marked preponderance of its proximal humerofemoral location dependent upon the fact that these 2 bones have the largest area of capsular to metaphyseal bone reflection.

Adolescent↗
PubMed1991

[A microradiographic and histological study of a case of dentinogenesis imperfecta type I].

Four temporary teeth, extracted for periodontal infection reasons, from a 53-months-old child with osteogenesis imperfecta, have been coated in methyl metacrylate and prepared for microradiographic analysis and light microscopic study. The enamel and dentin of three teeth (51, 65 and 85) don't show any particularity, some how the cementum is remarkably thin. Pulp chambers was large and contain a great number of calcifications. Some of them present a radial striation around a radio-transparent center, and when coloured with blue of methylen, they revealed inflammatory or fibroblastic cells. The fourth tooth (55) shows a dentinogenetic overproduction which closed the major part of the pulp chamber. The dentin presents two rows of different aspect, separated with a calcified bond. The mantle dentin contains sinuous tubules with a type I arrangement of SIAR classification (1986). But, in the deepest dentin, they are very little size and joined together while approaching the center of the tooth and coast along cellular inclusions, pathognomonic sign of dentinogenesis imperfecta. The pulpal space not obliterated contains a calcification with radial and microlacunary aspect.

Child, Preschool↗
PubMed1991

Resorption of the crown of an unerupted permanent molar.

This case report describes an unusual phenomenon where resorption occurred in the crown of an unerupted permanent molar. It was an incidental radiological finding. After eruption the tooth was extracted. Histological examination revealed resorption of enamel and dentine, and partial replacement by calcific material. The possible aetiology of the condition is discussed.

Child↗
PubMed1975

Electron microscopic study of early formation of the tooth enameloid of a fish (Hoplognathus fasciatus). I. Odontoblasts and matrix fibers.

An electron microscope study was made on the tooth germs of Hoplognathus fasciatus in early developmental stage. Special attention was given to the odontoblasts, enameloid matrix fibers, calcification of enameloid and the hitherto controversial origin of the enameloid. 1. The ameloblasts and the odontoblasts are demarcated by a single layer of basement membrane which persists until immediately before the calcification of the enameloid matrix. 2. This histogenesis of the enameloid matrix begins with the formation of non-striated fibers 140-180 A thick. They are arranged in a direction vertical to the basement membrane and parallel to the sides of odontoblasts. Fibers with regular cross striations of 640 A periodicity later appear and the entire enameloid matrix is formed by these fibers. 3. Along with the formation of the enameloid, the odontoblasts assume a high columnar form, with a marked increase in cell organelles which show marked polarity suggesting active protein synthesis. Numerous odontoblastic processes are noted in the enameloid matrix. Granules, representing precurosors of enamleoid matrix fibers occur in the odontoblasts. Based on these findings, the enameloid matrix fibers must be of mesodermal origin. 4. Deposition of crystals of small size, needle and tube in shape, occurs in the circumference of the fiber bundles. As calcification progresses, crystals appear in the central portion of the bundles. Later, large crystals of rod and platelet shapes become intermingled. In addition to this, small crystals are fused, forming aggregates.

Ameloblasts↗
PubMed2006

[Experimental study of the dental follicle's function in tooth root development].

OBJECTIVE: To study role of dental follicle in tooth root development. METHODS: Sixteen mandibular first molar dental germs from eight five-day postnatal Balb/c mice were divided into two groups randomly. Dental follicle of germs in one group was undetached and that of another group was removed. Subsequently, each of the germs was separately transplanted to back-muscles of adult nude mice. At seventh and fourteenth day after transplanting, the germs were collected, fixed, demineralized, dehydrated, and embedded in wax in sequence. Serial sections of 5 microm thick were made following the routine methods, stained with haematoxylin-eosin dying solution, and observed under a light microscope. RESULTS: All implantations were located in the back-muscles with abundant capillary vasculature. Under microscope, although all tooth germs could further develop after grafting, tooth germs without dental follicle developed slowly with small size and low calcification compared to those with dental follicle. Although position of Hertwig's epithelial root sheath of all germs seemed no changing, roots of the group with dental follicle could further develop and the roots develop toward the apical direction; this tendency couldn't be seen in the germs of another group. Inflammatory cells could be seen in and out of the pulp cavity of the two groups at 7th day after grafting, while no obvious inflammatory cell was observed at 14th day after grafting. CONCLUSION: Dental follicle play an important role in tooth root development. It probably can lead tooth root to develop in normal direction.

Animals↗
PubMed2000

Apatite mineralization in teeth of the chiton Acanthopleura echinata.

Raman spectroscopy has been used to demonstrate, for the first time, that calcium mineralization in the core of the major lateral teeth of the chiton Acanthopleura echinata takes place as an ordered process, with crystalline carbonated apatite being the first mineral deposited. Deposition begins at the top of the tooth core, under the so-called tab region, progresses down the interior surface of the tab and lepidocrocite layer, and then extends outwards to the anterior surface. Mineralization is not initiated until the lepidocrocite layer has isolated the core of the tooth from the magnetite cap. The last region to be infiltrated is the anterior basal region of the tooth cusp, immediately above the junction zone. The junction zone is also a region of high ion density, as determined by energy dispersive spectroscopy (EDS) analysis, but we show here for the first time that it is free of mineral deposits, acting instead as a transfer and storage region.

Animals↗
PubMed1964

CALCIFIED ECTODERMAL COLLAGENS OF SHARK TOOTH ENAMEL AND TELEOST SCALE.

Amino acid analysis of protein from the enamel of shark teeth and from teleost scales shows the presence of collagens which can be classified chemically as ectodermal. This finding, together with results from a histological examination of the development of these tissues, constitutes strong evidence that both proteins are derived from the ectoderm, like the enamel of higher vertebrates. Since both are calcified, calcification cannot be a specific property of collagens of mesodermal origin alone.

Amino Acids↗
PubMed1988

Changes in bone mineralization pattern: a response to local stimulus in maxilla and mandible of dogs.

A pilot study was carried out in order to verify the pattern of changes in mineralization of bone in the maxillas and mandibles of dogs which had a tooth extraction or luxation. Bone mineral content was determined using computerized microdensitometry. Significant changes in patterns of mineralization were found for alveolar bone, cortical bone and trabecular bone at the sites adjacent to the area of operation. These findings suggest that the three envelopes of jaw bones of the dogs are influenced by Regional activation phenomenon (RAP). These results have important implications for the design of clinical studies of periodontium. A more detailed study should elucidate the cellular mechanisms by which these changes occur.

Animals↗
PubMed1998

Regional odontodysplasia. Report of two cases.

Two cases of regional odontodysplasia in girls are reported; one affected the lower incisors, and the other the left maxilla. The first case was radiographically followed over a 6-year period, during which time the ghost teeth exhibited significant dentin formation, along with a resultant decrease in pulp size and relative normalization of the radicular anatomy. The second case involved the deciduous molars and the first permanent molar. In addition to tooth alterations, both cases exhibited many odontogenic epithelial islands and extensive areas of calcification in the mucosa. Diagnosis, causes, and treatment are discussed in the light of recent data.

Adolescent↗
PubMed1982

Osteogenesis imperfecta lethal in infancy: case report and scanning electron microscopic studies of the deciduous teeth.

Radiologic evaluation of the skeleton and scanning electron microscopic studies of the teeth were performed on an infant boy with a lethal osteogenesis imperfecta (OI) syndrome who died at 10 mo of pneumonia. The skeletal findings included ribs that were focally expanded by fracture calluses, flat vertebral bodies, and wide limb bones. On fractured tooth surfaces, the enamel and dentin were normal as was the dentin calcification front. Although microscopic abnormalities have been noted in teeth from previously reported infants with lethal OI, a few studies also report infants with normal teeth. These differences in dental findings may indicate heterogeneity in OI lethal in infancy. Results of our study indicate that, until the primary biochemical defects in the OI syndromes are elucidated, examination of teeth from other infants with lethal OI and detailed evaluation of other clinical and skeletal features will aid in delineating heterogeneity and variation in expression in lethal OI.

Humans↗
PubMed2005

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.

Analysis of Variance↗
PubMed2000

Osteoprotegerin reverses osteoporosis by inhibiting endosteal osteoclasts and prevents vascular calcification by blocking a process resembling osteoclastogenesis.

High systemic levels of osteoprotegerin (OPG) in OPG transgenic mice cause osteopetrosis with normal tooth eruption and bone elongation and inhibit the development and activity of endosteal, but not periosteal, osteoclasts. We demonstrate that both intravenous injection of recombinant OPG protein and transgenic overexpression of OPG in OPG(-/-) mice effectively rescue the osteoporotic bone phenotype observed in OPG-deficient mice. However, intravenous injection of recombinant OPG over a 4-wk period could not reverse the arterial calcification observed in OPG(-/-) mice. In contrast, transgenic OPG delivered from mid-gestation through adulthood does prevent the formation of arterial calcification in OPG(-/-) mice. Although OPG is normally expressed in arteries, OPG ligand (OPGL) and receptor activator of NF-kappaB (RANK) are not detected in the arterial walls of wild-type adult mice. Interestingly, OPGL and RANK transcripts are detected in the calcified arteries of OPG(-/-) mice. Furthermore, RANK transcript expression coincides with the presence of multinuclear osteoclast-like cells. These findings indicate that the OPG/OPGL/RANK signaling pathway may play an important role in both pathological and physiological calcification processes. Such findings may also explain the observed high clinical incidence of vascular calcification in the osteoporotic patient population.

Acid Phosphatase↗