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At least 109 records · Page 6Linked to original sources
PubMed2004

Does space in the jaw influence the timing of molar crown initiation? A model using baboons (Papio anubis) and great apes (Pan troglodytes, Pan paniscus).

Radiographic and histological studies of baboon (Papio hamadryas, P. anubis) and chimpanzee (Pan troglodytes) permanent tooth development have found that periods of molar crown mineralization overlap markedly in chimpanzees but are staggered in baboons. Here we test the hypothesis that these intertaxon differences in molar initiation are primarily due to the space available in the mandibles of each species for these teeth. This study includes radiographic, linear measurement, and three-dimensional (3D) coordinate landmark data taken from baboon (Papio anubis n=51) and great ape (Pan paniscus n=43, P. troglodytes n=60) mandibles and permanent molars across a broad developmental range for each taxon. Unexpectedly, 3D multivariate statistical shape analysis of the molar crypt, crown, and root data shows that all three species trajectories of molar row shape change are indistinguishable from each other. Qualitative analysis of these 3D data reveals subtle and inconclusive intergeneric differences in the space maintained between adjacent molars during growth. The space distal to each newly initiated molar is slightly greater in the baboon. Bivariate analyses comparing molar row and mandibular corpus proportions in Papio and Pan fail to show clear or consistent taxonomic differences in the ratio of space afforded developing molars in the alveolar bone. Thus, there is a poor correlation between mandibular proportion and both intermolar spacing and 3D molar development pattern. Contrary to earlier studies, these results suggest that pattern of molar crown initiation and temporal overlap of adjacent mineralizing crowns is not significantly different between Papio and Pan. This may be due in part to the inclusion here of not only 3D molar crown data but also 3D molar crypt data. This study strongly refutes the hypothesis that space available in the mandible directly underlies different times of permanent molar crown initiation between Papio and Pan.

Animals↗
PubMed2005

Ultrastructural examination of dentin using focused ion-beam cross-sectioning and transmission electron microscopy.

Focused ion-beam (FIB) milling is a commonly used technique for transmission electron microscopy (TEM) sample preparation of inorganic materials. In this study, we seek to evaluate the FIB as a TEM preparation tool for human dentin. Two particular problems involving dentin, a structural analog of bone that makes up the bulk of the human tooth, are examined. Firstly, the process of aging is studied through an investigation of the mineralization in 'transparent' dentin, which is formed naturally due to the filling up of dentinal tubules with large mineral crystals. Next, the process of fracture is examined to evaluate incipient events that occur at the collagen fiber level. For both these cases, FIB-milling was able to generate high-quality specimens that could be used for subsequent TEM examination. The changes in the mineralization suggested a simple mechanism of mineral 'dissolution and reprecipitation', while examination of the collagen revealed incipient damage in the form of voids within the collagen fibers. These studies help shed light on the process of aging and fracture of mineralized tissues and are useful steps in developing a framework for understanding such processes.

Aged↗
PubMed2000

The matrix metalloproteinase gelatinase A in human dentine.

A dentine protein extraction protocol was modified in order to identify matrix metalloproteinase gelatinolytic activities in the non-mineralized and mineralized phases of human dentine. Dentine proteins from 24 individual permanent molars from patients aged 15-73 years were sequentially extracted, first with guanidinium chloride (G1 extract), then EDTA (E extract), and after this demineralization step, again by guanidinium chloride (G2 extract) to dissociate collagen-associated proteins. Extracts were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and the gels were processed by Western blotting and zymography to detect gelatinolytic activities. Active and latent forms of gelatinase A were identified in the non-mineralized dentine fraction (G1 extract) of 58% of the teeth. Other gelatinolytic species were also detected by zymography with apparent M(r) of 92, 54 and 30 kDa. Although gelatinase A was detected in the G1 extracts of teeth from all ages, indicating more recent synthesis and remodelling of the predentine, gelatinase A was never detected in any E extract or in the G2 extracts of patients older than 41 years. The presence of the active form of gelatinase A in mineralized human dentine implicates this enzyme in dentine mineralization.

Adolescent↗
PubMed2000

Early development of the tush and the tusk of the African elephant (Loxodonta africana).

This early development was studied from a serial histological sections of eight elephant embryos with masses varying between 1 and 240 g. The tush and the tusk develop from one tooth germ in a deciduous to permanent tooth relation. In order to study the mineralization of the dental organ of the tush and cap and bell stage of the tusk, embryos older than 3-months' gestation (weighing more than 250 g) would be required.

Animals↗
PubMed2001

Ultrastructure of early mineral deposition during hyaline layer formation in rat molars.

There is no consensus on whether the first mineralized layer, the hyaline layer, that is juxtaposed to root dentine is a variety of dentine or cementum or even a tissue of epithelial origin. Some suggest that there is no intermediate tissue between the acellular extrinsic fibre cementum (AEFC) and the root dentine. Here, to study hyaline layer formation and mineralization we examined by transmission electron microscopy the early stages of root development in upper molars from 10 to 13 day old Wistar rats. In addition to conventionally processed material, undemineralized and unstained sections were examined, which showed the deposition of fine mineral crystals in contact with the mineralized surface of root dentine. Early mineralization of the hyaline layer occurred in the region of the inner basement membrane, which persisted between the inner cellular layer of Hertwig's epithelial root sheath and the outer mineralized root dentine. When the root sheath began its fragment, collagen fibrils from the developing periodontal ligament began to insert into the mineralising hyaline layer, which was 0.5-0.8 micron wide. As the fragmentation of the root sheath HERS increased, more collagen fibrils appeared intermingled with the mineralising hyaline layer. In more advanced stages, when the hyaline layer had become fully mineralized and the formation of the AEFC began, the hyaline layer could no longer be identified. Thus, the hyaline layer is clearly discernible at early stages of periodontal development. Subsequently, it is masked by intermingling of cementum and dentine and therefore it is not possible to detect it in the formed roots of rat molars.

Animals↗
PubMed1998

Comparative observations on the spacing of short-period (von Ebner's) lines in dentine.

The spacing of short-period incremental markings in dentine was measured in longitudinal ground sections and in longitudinal demineralized silver-stained sections of permanent human canines and premolars. Measurements were made (i) within 50 microm from the granular layer of Tomes (GLT), (ii) between 100 and 200 microm from the GLT, and (iii) in the axial plane of the tallest cusps. Median values for the spacing of calcospheritic lines closest to the GLT in the ground sections increased from 1.8 to 2.8 microm as the lines gradually coalesced into a laminar pattern beyond the GLT pulpally. Median values for the spacing of short-period lines in the cuspal dentine, where dentine formation is known to be fastest, were 4.1 microm. Markings in the demineralized sections were between 25 and 39% closer together, presumably due to contraction and shrinkage during specimen preparation. The spacings of short-period incremental lines measured on ground sections of non-human primate dentine (gibbon, siamang, orang) and on pig dentine, all between 100 and 200 microm from the GLT, clustered between 2.5 and 3.5 microm. Apart from gibbon dentine (in which spacings were closer together in this position than in the others), the distribution of measurements was not significantly different in pig, orang or human dentine. However, none of the data for the comparative samples presented here revealed spacings of short-period lines anywhere close to the 16 microm previously reported for circumpulpal dentine in animals. These data suggest that there may be many other animals where the mode and, to some extent, rate of dentine mineralization close to the root surface follows a common pattern. While data for the spacing of incremental markings in dentine provide no evidence for their periodicity, it is clear that the measurements made in the ground sections match the reported daily rates of mineralization at these locations, whereas those in demineralized silver-stained sections do not. Tissue shrinkage is probably a better explanation for this than the generally accepted view that they represent 12 h increments of dentine mineralization. This study provides a better basis for identifying and describing these lines, and for distinguishing them from other kinds of incremental markings in dentine.

Animals↗
PubMed1999

Formation and mineralization of murine molar roots with hypocalcaemia induced by a low-calcium diet and the changes after returning to a normal diet.

The purpose was to examine the formation and mineralization of molar roots in rats with hypocalcaemia, induced by a low-calcium diet and the changes after returning to a normal diet. Two-week-old male Wistar rats were fed a low-calcium diet (0.03% calcium) during the period when the first molar roots form and then a diet containing normal amounts of calcium (1.83% calcium) was restored. The blood calcium, the length and mineralization of the first upper molar roots, and the density of surrounding alveolar bone were measured, and the morphological and histological features of the roots examined. While the rats were fed the low-calcium diet, they had a significantly lower blood calcium than normal controls. Morphologically, the upper first molar roots were shorter and the predentine layer was thicker. The mineralization of dentine and the surrounding alveolar bone was significantly less than in the controls and no mineralization was detected in the thickened predentine. After a normal calcium diet had been restored, the blood calcium, thickness of dentine, alveolar bone density, and length of the roots caught up with the normal. In addition, hypomineralized dentine and interglobular dentine were observed. Subsequently, the mineralization of the dentine increased and the amount of interglobular dentine gradually decreased. These results suggest that in rats a low-calcium diet induces hypocalcaemia, causing the formation of interglobular dentine and hypomineralization of the dentine of the roots. Most physiological variables recovered completely with the return to a normal-calcium diet, although some hypomineralization of the dentine remained.

Animals↗
PubMed1999

Difficulties in estimating age using root dentine translucency in human teeth of varying antiquity.

Estimation of age at death is an essential part of reconstructing information from skeletal material. This becomes more difficult after development has ceased and following taphonomic alteration in archaeological material. Most biological markers of age do not record the chronological age (calendar age), but the biological or physiological age of the individual. Of the age-related changes in the mature dentition of modern samples, the extent of root dentine translucency (RDT) has been shown to correlate closely with chronological age. A protocol for measurement of RDT was established and applied to modern and archaeological teeth of known age (Spitalfields sample). Percentage length of RDT in sectioned teeth was found to correlate well with chronological age in the modern sample but not in the archaeological sample. The majority of the archaeological sample was affected by a morphological change creating a "chalky" appearance to the dentine. Removal of the obviously affected teeth did not improve the correlation coefficients to any useful degree. "Chalky" dentine appeared, under the light microscope, to be composed of large fenestrations, islands of mineralized tissue and masses of filiform structures that appeared to be following the path of the dentinal tubules in their invasion of the peripheral dentine. The filiform structures are consistent in their appearance with a previously reported tunnelling mycelium and impart such an effect on RDT that it cannot readily be used for age estimation in affected teeth.

Adult↗
PubMed2000

A histological study of the effect of growth hormone on odontogenesis in the Lewis dwarf rat.

The effect of growth hormone (GH) on the dentition has been described in children with pituitary dwarfism where teeth fail to form; those that do form tend to be reduced in size and the eruption potential is diminished. The aim here was to examine the effect of GH on odontogenesis via molar development in Lewis (control), dwarf (Dw) and Dw GH-treated (Dw+GH) rats aged 3, 6, 9, 12 and 15 days. Dw+GH animals received a twice-daily dose (65 microg/kg) of GH which commenced at 2 days of age. Animals were killed, mandibles removed, processed to embedding in paraffin, sectioned and stained for histological examination of molar morphology during development. Variations in enamel mineralization and root development were observed. In 6-day-old animals, enamel mineralization was delayed in Dw and Dw+GH animals. Root initiation was evident at 6 days of age in controls but was not observed until 9 days of age in Dw and Dw+GH animals. At 12 days of age, maturation of enamel in Dw and Dw+GH animals remained delayed. By 15 days of age no variation in tooth development was evident. These data indicate that enamel mineralization is affected by the level of circulating GH in the rat. A specific deficiency of GH did not appear to delay bone resorption prior to tooth emergence.

Animals↗
PubMed1999

Apparent hypodontia: a case of misdiagnosis.

The case of a 12-year-old girl is reported, whose pretreatment radiograph demonstrated agenesis of two premolars and a canine and slow development of the contralateral premolars. A follow-up radiograph taken 1 year later showed initial mineralization of a tooth germ in the site of one of the apparently missing premolars. The cause, diagnosis, and treatment planning implications of delayed mineralization and slow development of second premolars are discussed with reference to the literature.

Anodontia↗
PubMed1997

Periapical repair and apical closure of a pulpless tooth using calcium hydroxide.

A case with a wide-open apex and a large cystlike periapical lesion in an adult is presented. The lesion formed as a result of necrosis from trauma to a maxillary central incisor 12 years ago. After nonsurgical endodontic treatment with calcium hydroxide paste and a calcium hydroxide-containing root canal sealer, apical closure and significant healing of the periapical lesion within 15 months were observed. This report suggests that even large periapical lesions (likely cystic) could respond favorably to nonsurgical treatment.

Adult↗
PubMed2001

Expression of cementum-derived attachment protein in bovine tooth germ during cementogenesis.

Cementum-derived attachment protein (CAP) is a 56 kDa collagenous protein that promotes attachment of mesenchymal cells. Previous studies have shown that the presence of CAP is restricted to cementum in adult human tissues. In this study, we report generation of a monoclonal antibody against CAP and its use for the investigation of CAP in developing bovine tooth germs. Mice were immunized with CAP purified from bovine cementum, and a monoclonal antibody, 3G9, was produced. Immunohistochemical staining of bovine tooth germ at root forming stage using 3G9 antibody showed that the tissue distribution of CAP expression was limited to cementum matrix and cementoblasts during cementogenesis. Alveolar bone did not stain with the 3G9 antibody, whereas anti-type I collagen stained positively. CAP was purified from bovine tooth germs with immunoaffinity purification using the 3G9 antibody. Examination of the immunoaffinity-purified fraction showed that CAP existed in tooth germ as a 65 kDa protein. The protein was susceptible to bacterial collagenase. To investigate the possible biological function of CAP during cementogenesis, we isolated dental follicle cells from the bovine tooth germ, and showed that they adhered to surfaces containing CAP. These data demonstrate that CAP is expressed by bovine cementoblasts as a 65 kDa protein and that the CAP may have a function in cementogenesis.

Animals↗
PubMed2000

Advanced dental maturity in children with juvenile rheumatoid arthritis.

The subjects of the investigation comprised 95 girls and 73 boys with juvenile rheumatoid arthritis (JRA), and 102 girls and 66 boys representing healthy controls, all with a chronological age from 6.3 to 14.4 yr. The dental development was assessed from panoramic radiographs using a seven-tooth model. The radiographs were evaluated on three separate occasions with a minimum interval of one month in a randomized order, and blind with respect to absence or presence of JRA. In both JRA patients and healthy controls, dental maturity was ahead of chronological age. In addition, dental maturity was significantly advanced in JRA patients with 0.26 yr in girls and 0.28 yr in boys. It is tentatively suggested that the advanced dental development in JRA patients compared with healthy children was partly an effect of treatment with cortisone, while the influence of the disorder per se remains to be elucidated.

Adolescent↗
PubMed2003

Immunocytochemical characterization of ectopic enamel deposits and cementicles in human teeth.

Despite the relative frequency and clinical relevance of radicular enamel deposits and cementicles, their etiology and nature are unknown. The purpose of the present study was therefore to evaluate the presence and distribution of mineralization-associated non-collagenous matrix proteins (NCPs) in various types of root-associated ectopic mineralizations. Human teeth were processed for embedding in epoxy or acrylic resins. Tissue sections were incubated with antibodies to amelogenins (AMEL), bone sialoprotein (BSP), and osteopontin (OPN). Radicular enamel deposits contained residual organic matrix that labeled for AMEL. In contrast, BSP and OPN were not detected in the residual enamel matrix, they were found in the cementum deposited on its surface as well as in collagen-free cementicle-like structures in the adjacent periodontal ligament. True cementicles consisted of a collagenous matrix intermixed with a non-collagenous ground substance. Labeling for BSP and OPN was mainly associated with the interfibrillar ground substance. No immunoreactivity for AMEL was detected in cementicles. These data indicate that ectopic enamel deposits on the root retain a high amount of AMEL, whereas cementicles contain BSP and OPN, two NCPs typically found in bone and cementum. These NCPs may, like in their normal tissue counterparts, play a role in the mineralization process.

Amelogenin↗