Factors controlling apatite crystallization, with particular reference to the effect of fluoride and accompanying ions.
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Apatites↗
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Microradiography of oral tissues.
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Dental Calculus↗
Mechanical properties and microstructure of hypomineralised enamel of permanent teeth.
Isolated enamel defects are commonly seen in first permanent molar teeth but there has been little work on the physical and morphological composition of affected molars. The aim of this study was to determine the mechanical and morphological properties of hypomineralised first permanent molar teeth, utilising the Ultra-Micro-Indentation System (UMIS) and scanning electron microscope, respectively. Further investigations using Energy Dispersive X-ray Spectrometery (EDS), Back Scatter Electron (BSE) Imaging, and X-ray diffraction were employed to attempt to determine the chemical composition, mineral content and crystalline structure of the hypomineralised tissue, respectively, of eight first permanent molars with severe enamel hypomineralisation. The hardness and modulus of elasticity were found to be statistically significantly lower (0.53+/-0.31 and 14.49+/-7.56 GPa, respectively) than normal enamel (3.66+/-0.75 and 75.57+/-9.98 GPa, respectively). Although the fractured surface of the hypomineralised enamel was significantly more disorganised and the relative mineral content was reduced by approximately 5% in comparison to sound enamel, the mineral phase and Ca/P ratio was similar in hypomineralised and sound enamel. The dramatic reduction in the mechanical properties of first permanent molar teeth has ramifications when clinicians are choosing restorative materials to restore the defects. The reason for the dramatic reduction in mechanical properties of hypomineralised first permanent molar teeth is at present unknown.
Absorptiometry, Photon↗
Odontoblast primary cilia: facts and hypotheses.
Odontoblasts, the cells responsible for the dentine formation, are organized as a single layer of highly polarized and differentiated post-mitotic cells along the interface between the dental pulp and the mineralized tubules. They lay down the physiological secondary dentine throughout the life of the teeth. Odontoblasts play a central role in the transportation of calcium to the dentine and they possibly mediate early stages of sensory processing in teeth. A primary cilium, 9+0 configuration, have been regularly identified in a supra nuclear location. Calbindin D28k has been detected at the base of the cilium membrane. The cilium structure was positive with detyrosinated alpha tubulin antibodies in vivo and in cultured human odontoblasts. Transcripts of tektin, a protein involved in ciliogenesis, were expressed in vitro. The putative role of the primary cilium constituting a critical link between external teeth stimuli and odontoblast responses is extensively discussed.
Calbindin 1↗
Age estimation of unaccompanied minors. Part II. Dental aspects.
Recent years have brought a worldwide increase in cross-border migration due to a globalized economy and ongoing belligerent conflicts. As a result, the percentage of foreigners among the general population has steadily increased not only in Germany, but also in other countries. This trend has triggered a growing demand for forensic medicine to assess the age of adolescents and young adults. The individuals examined here are unaccompanied minors without valid identification documents who do not know their age or else are suspected of not giving their correct age. The mineralization of third molars is the main criterion for dental age estimation of living subjects in the relevant age group. To date insufficient knowledge has been obtained about how ethnic origin can influence tooth mineralization. This, however, constitutes a restraint on the reliability of age estimates and hence on the forensic value of information essential to legal security. A comparative study was conducted to present comparative data on third molar mineralization in a Caucasoid, Mongoloid and African sample. In conclusion, forensic age estimates of living subjects would be more powerful tools if population-specific standards were applied to evaluations of wisdom tooth mineralization. Since the mineralization of third molars is usually completed by the age of 19 or 20 years, this feature cannot be used to ascertain whether a person has attained the forensically relevant age of 21 years. The question was whether determination based on an orthopantomogram of a combination of features relevant to dental age estimation of adults supplies forensically useful information for ascertaining whether a person has attained 21 years of age. The features considered include the DMFT index of all permanent teeth, the DMFT index of all permanent teeth excluding third molars and the DFT index of third molars projecting beyond the occlusal plane. It can be concluded that an evaluation of the variations of the DMFT index does not by itself yield sufficient data to determine with the accuracy required in criminal proceedings whether a person has attained 21 years of age. An additional X-ray examination of the medial clavicular epiphyseal cartilage is, therefore, strongly recommended when assessing whether a person is over 21.
Adolescent↗
Studies on the progress of third-molar mineralisation in a Black African population.
The forensic determination of the age of living people has become increasingly important in recent years. With regard to the relevant age group, the radiographic assessment of third-molar mineralisation is of particular importance. So far, the influence of geographic origin on the mineralisation rate has been insufficiently analysed. The paper is based on a total of 595 conventional orthopantomograms of 474 male and 121 female Black Africans aged between 10 and 26 years for whom dates of birth were known. The mineralisation status of third molars was evaluated based on Demirjian's classification of stages [Demirjian et al., 1973. A new system of dental age assessment. Hum. Biol. 45, 221-227]. This study presents the means and standard deviations, median values and the lower and upper quartiles separately for both sexes for the mineralisation stages D-H. Statistically significant differences between the upper and lower jaws were observed in males examined with regard to their attaining the stage F. Mandibular teeth developed 0.8 years earlier than maxillary teeth. Significant sex-specific differences were found with regard to the age at which tooth 38 reached the stage G. In females, tooth 38 reached stage G 1.5 years earlier than in males. In comparison to White probands, the Black African sample showed a tendency to achieve the mineralisation stages earlier. We would recommend using population-specific standards for age determination purposes.
Adolescent↗
Effects of proinflammatory cytokines on the expression of mineralization markers and heme oxygenase-1 in human pulp cells.
The roles of IL-1alpha and TNF-alpha in early pulp inflammation were investigated by determining the alkaline phosphatase (ALP) activity, the osteonectin (ON), osteocalcin (OC), bone sialoprotein (BSP), and heme oxygenase-1 (HO-1) expression using an immunoblot method. Primary cultured dental pulp cells were treated with IL-1alpha, TNF-alpha, or both for 3, 7, and 14 days. The pulp cells treated with IL-1alpha for 3 days showed elevated ALP activity and increased ON, OC, and HO-1 expression, whereas TNF-alpha treatment did not increase the ALP activity and no BSP was expressed until day 14. The pulp cells treated with both IL-1alpha and TNF-alpha for 3 days showed increased HO-1 expression compared with that of the control. These data suggest that IL-1alpha and TNF-alpha produced in the early inflammatory reaction have different functions in human pulp cells. IL-1alpha induces ALP, ON, and OC in tooth mineralization and it may play a role in the cytoprotection of pulp cells via HO-1 expression, while long-term treatment of TNF-alpha may inhibit the tooth mineralization.
Alkaline Phosphatase↗
Studies on the chronology of third molar mineralization in a Japanese population.
In Germany, a sharp increase in forensic age estimations of living individuals has been observed in recent years. With regard to the relevant age group, radiologic assessment of the mineralization stage of the third molars is of particular importance. Still, the influence of ethnicity on the pace of mineralization has been insufficiently analyzed. A total of 1615 orthopantomograms of 929 female and 686 male Japanese subjects aged between 12 and 30 years was examined. The mineralization stages of third molars were evaluated on the basis of Demirjian's stages modified in accordance with Mincer's model. For the individual mineralization stages, the study presents the means and standard deviations for the genders separately. No statistically significant differences in the chronology of third molar mineralization between maxilla and mandible and between sides were observed. A comparison between genders largely did not render significant differences either. Apart from forensic age determination in living subjects, the presented reference data can also be used for age estimations of unidentified corpses and skeletons.
Adolescent↗
Effects of an enamel matrix derivative on human osteoblasts and PDL cells grown in organoid cultures.
OBJECTIVE: The objective of this study was to investigate cellular effects of enamel matrix derivative (EMD) in human derived, primary osteoblasts and periodontal ligament (PDL) cells grown in organoid cultures. STUDY DESIGN: Cell replication was assessed by BrdU-incorporation. [(3)H]-proline incorporation was measured to determine the synthesis of proline-containing proteins, such as collagen. In addition, calcium accumulation and alkaline-phosphatase-activity were quantified. Electron microscopy for morphological analysis was performed. RESULTS: Our results showed that EMD enhances BrdU-incorporation in PDL cells and osteoblasts. Also, in osteoblast organoid cultures [3H]-proline incorporation was 3-fold increased (P < .01). Extensive matrix deposition was noted in osteoblast cultures by electron microscopy. In osteoblasts, high levels of calcium accumulation and alkaline-phosphatase-activity were found. However, EMD did not promote mineralization. CONCLUSION: Our results indicate that under organoid culture conditions EMD is able to promote the synthesis of proline-containing proteins such as collagen but not matrix mineralization of primary human osteoblastic cells.
Adult↗
Autoradiographic investigation of the effect of 1-hydroxyethylidene-1, 1-bisphosphonate on matrix protein synthesis and secretion by secretory ameloblasts in rat incisors.
Seven daily subcutaneous injections of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) can induce enamel hypoplasia. Several enamel-free zones were observed along the crown-analogue side of rat incisors during the secretory stage of amelogenesis. Ameloblasts related to the enamel-free zones lay directly on the abnormally non-mineralized mantle dentine, whereas the adjacent ameloblasts, which were forming the enamel matrix layer, were associated with the region where mineralization of dentine was proceeding. The further purpose of this study was to investigate the synthetic and secretory activity of these two groups of ameloblasts and to trace the fate of the radioactively labelled proteins. [(3)H]-proline was administered to Wistar rats 12 h after the last injection of HEBP. Light-microscopic autoradiography was performed. Quantitative analysis indicated that the ameloblasts of the enamel-forming zones in the drug-treated group showed a distribution pattern of silver grains similar to that of the controls. The ameloblasts of the enamel-free zones also demonstrated incorporation of [(3)H]-proline at the same level. There was some labelling over the non-mineralized mantle dentine, which was supposed to indicate the penetration of ameloblast products. From these results, it is concluded that HEBP does not affect the ameloblast activity in protein synthesis. The complete failure of enamel-layer formation in some specific regions is probably due to the failure in protein secretion and protein deposition. This study provides additional evidence that the mineralization of dentine is an essential factor in successful enamel matrix secretion and deposition.
Ameloblasts↗
Secondary ion mass spectrometry and X-ray microanalysis of hypomineralized enamel in human permanent first molars.
A common finding in Swedish children is hypomineralization in first molars of unknown cause. Little is known about the chemical composition of the disturbed enamel. The aim here was to analyse the concentration gradients for F, Cl, Na, Mg, K and Sr in hypomineralized enamel from 17 permanent molars by means of secondary ion mass spectrometry, to complete this analysis with an examination of the main matrix elements O, P and Ca by means of X-ray microanalysis, and to compare them with normal enamel. Hypomineralized enamel had a higher content of carbon and the calcium as well as the phosphorus concentration was lower than in normal enamel. The mean Ca/P ratio in hypomineralized areas was significantly lower (1.4) than in the adjacent normal enamel (1.8). The F content was highly variable in impaired enamel and higher than in normal, but close to the surface there was most often no difference between the two. Contents of Mg and K were slightly higher in hypomineralized areas, especially towards the surface. Also Na had a somewhat higher content toward the surface in defective enamel. Cl and Sr contents had negligible or no diversity in relation to the degree of mineralization.
Calcium↗
Fluoride alters casein kinase II and alkaline phosphatase activity in vitro with potential implications for dentine mineralization.
Dentine phosphoprotein (DPP), a major non-collagenous acidic protein of dentine, undergoes altered phosphorylation in vivo in the presence of high fluoride concentrations. This has major implications for the altered mineralization patterns found during fluorosis. In dentine, casein kinase II is involved in phosphorylating DPP, and alkaline phosphatase (ALP) is ascribed roles in the dephosphorylation of DPP, increasing the inorganic phosphate at the mineralization front and the removal of pyrophosphate. Here the influence of fluoride in vitro on the activity of purified casein kinase II and ALP and its relation to altered patterns of mineralization were examined. Kinetic analysis showed that casein kinase II activity was completely inhibited at 0.04 M NaF. Vmax when compared to the control assay was significantly decreased (P < 0.0001) between concentrations 4 x 10(-4)-4 x 10(-8) M NaF. Significant changes to the Km (P < 0.0001) were also observed. ALP activity was inhibited by NaF (0.09-9 x 10(-8) M), with Vmax significantly decreased (P < 0.0001) at 0.09 M NaF. Alterations in the activity of these enzymes in the presence of fluoride may in part explain the decreased phosphorylation observed in DPP isolated from fluorotic dentine and may aid understanding of the altered matrix mediated mineralization patterns found during fluorosis.
Alkaline Phosphatase↗
Expression and localization of MGP in rat tooth cementum.
Tooth cementum, a calcified hard tissue covering the root surfaces, is an important component connecting the teeth to the collagenous fibres of the periodontal ligament. Although the overall composition of cementum may closely resemble that of bone, each part has not been fully characterized. Here, the localization of the matrix gamma-carboxyglutamic acid (Gla) protein (MGP), one of the major Gla-containing proteins in the body, in cementum was investigated using immunohistochemistry and in situ hybridization. (1) Strong MGP antigenicity was observed in the acellular cementum, but was only moderate in the cellular cementum; (2) polygonal periodontal ligament cells facing the acellular cementum and the uncalcified cellular cementum expressed MGP mRNA, indicating that these cells produced MGP and deposited it on the cementum; (3) MGP accumulated at the junction between the uncalcified and calcified cellular cementum; and (4) the distribution pattern of MGP antigenicity resembled that of osteopontin. As one function of MGP could be as a negative regulator for mineral apposition, the expression of MGP in the cells adjacent to the cementum may be important to prevent hyperapposition of minerals.
Animals↗
Immunochemical localization of the small leucine-rich proteoglycan lumican in human predentine and dentine.
The immunocalization of the small interstitial leucine-rich keratan sulphate proteoglycan lumican was studied in human teeth using a polyclonal antibody towards lumican and a standard indirect peroxidase technique. There was intense labelling for lumican in predentine, with immunopositivity also observed in and around the tubules, around the odontoblasts and in the pulp with a fibrillar distribution. The previous reported ability of lumican to control collagen fibrillogenesis and it putative function in collagen spacing suggest potential roles for lumican in predentine in relation to mineralization.
Adolescent↗
Sibling similarities in the tempo of human tooth mineralization.
The extent of tooth mineralization is a useful estimate of a child's physiological age it reflects the rate at which the child is developing towards maturity. As it is not known to what degree dental age is regulated by the genotype, this investigation estimated familial resemblance in the tempo of tooth mineralization. Panoramic radiographs of the children in 185 sibships were scored for stages of tooth formation, and dental age was calculated from sex-specific standards. Intraclass correlations of mineralization tempo were computed for maxillary and mandibular canines, premolars, second molars, and third molars. Correlations of mineralization tempo were significantly different than zero for all 10 teeth and ranged from 0.17 (SE = 0.06) for the mandibular second molar to 0.43 (SE = 0.05) for the mandibular second premolar. Intraclass correlations increased significantly when multiple teeth were used to more comprehensively define each child's dental age. Using an unweighted average of all 10 tooth types yielded a correlation of 0.41 (SE = 0.05). It appears, then, that a considerable proportion of the total variability in tooth-mineralization rate can be attributed to transmissible effects operating in the population under investigation.
Adolescent↗
The immunohistochemical localization of phospholipase Cgamma and the epidermal growth-factor, platelet-derived growth-factor and fibroblast growth-factor receptors in the cells of the rat molar enamel organ during early amelogenesis.
Findings on the localization and possible roles of the major growth factors, epidermal (EGF), platelet-derived (PDGF) and fibroblast (FGF) in early amelogenesis are contradictory and inconclusive. This study sought to localize immunohistochemically phospholipase (PLCgamma) and the EGF, PDGF and FGF receptors in the cells of the enamel organ during the events leading directly to early enamel formation in rat molars. PLCgamma is an immediate, downstream, signal-transduction pathway effector unique to the three receptors. A whole-head, freeze-dried sectioning method was used to reduce the possibilities of false-negative staining. A modification of the avidin/biotin complex method of immunohistochemical localization was used. Anti-PLCgamma and antibodies to each of EGF, PDGF and FGF receptors colocalized in the preameloblasts of the cervical loop, adjacent to the undifferentiated mesenchymal cells of the dental pulp. This staining disappeared shortly after the beginning of dentine mineralization. Staining for all four antibodies appeared on the proximal ends of the differentiating presecretory ameloblasts at the level of the beginning of predentine matrix deposition and continued in the secretory ameloblasts. It appears that EGF, PDGF and FGF have roles in the differentiation of ameloblasts and in control of cellular functions in presecretory and secretory ameloblasts. Their roles may represent redundancy of the kind seen in highly conserved tissues.
Ameloblasts↗
The effect of thyrocalcitonin and growth hormones on bone metabolism.
The use of the hormone, thyrocalcitonin, has been shown to change the bone metabolism so that resorption is decreased and calcium increased. The growth hormone seems to add to bone mass and indirectly prevents resorption. The combination of growth hormone and calcitonin seems to cause an unusual amount of resorption. This research has shown that metallic endosteal blade implants are not automatically successful even in short spans with additional support from two abutment teeth. It is true that the type of occlusion of the squirrel monkey is different from that of man, but the prosthetic devices that were placed in these animals can be validly compared to similar devices placed in man. While the hygiene cannot be practiced effectively by the animal, the psychogenic and emotional problems of man offset this disadvantage. Also, the diet of the monkey is not as traumatic to a prosthesis as is man's. Two of the most important criteria for implant success have not proved satisfactory: (1) no pocket depth beyond 3 mm. and (2) negative radiographic pathosis around the implant. While this study was not meant to be one of criticism or evaluation of metallic implants, it should be noted that thyrocalcitonin and the growth hormone, individually used, played an important part in retarding bone resorption around the blade. Autogenous bone grafts for residual alveolar ridge restoration often fail due to rapid osseous resorption and volume loss. The maintenance of osseous elements in the autogenous bone grafts when calcitonin had been administered was quite revealing. This might be the chemotherapeutic basis for the many conditions involving bone that dentists are called upon to treat.
Absorptiometry, Photon↗
Ultrastructure of initial crystal formation in dentin.
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Ameloblasts↗