Ultrastructural localization of dentine phosphoprotein in rat tooth germs by immunogold staining

Dentine phosphoprotein (DPP) was localized on thin frozen sections of fixed rat tooth germs by indirect immunogold staining. Antisera were directed against DPP and against glutaraldehyde-treated DPP and were characterized by immuno-electroblotting. In odontoblasts, DPP was found to be localized in the cisternae of the rough endoplasmic reticulum (RER) and the Golgi apparatus and in Golgi-associated vesicles. Odontoblastic processes were moderately positive for DPP and dentine was intensely labeled on frozen sections of unfixed tissue. Predentine showed a slight immunoreactivity. These results indicate the synthesis of DPP in the RER, its accumulation in the Golgi apparatus and its vesicular transport and secretion via the odontoblastic processes into dentine. The close association of the gold particles with the dentinal collagen fibres makes a role of DPP in linking mineral to collagen conceivable. Matrix vesicles were negative for DPP, suggesting that the protein is not present at the sites of matrix vesicle-associated nucleation.     

In vitro electrical impedance spectroscopy of human dentine: the effect of restorative materials

The influence of different restorative materials on in vitro dielectric properties of sound dentine was investigated. The studied samples were three-layer materials consisting of successive disks of dentine and silver amalgam or nanohybrid composite resin. Before being tested, the samples were maintained in physiological solution never more than 48 h from the extraction. Also, sections of intact dentine were similarly prepared for electrical measurements. Complex dielectric permittivity of these specimens was determined in a wide frequency range using the parallel-plate capacitor technique. Very similar dielectric responses of intact dentine and amalgam-dentine material were observed. This is explained on the basis of high dc conductivity exhibited by both samples. In contrast, resin-dentine specimen revealed a much more insulating behavior. A simple theoretical model for heterogeneous systems could be applied to these dental three-layer materials. The dielectric properties of restored dentine are strongly dependent on the kind of restorative material employed in each case. This suggests that electrical data should be used carefully in caries diagnosis on restored teeth.     

雨强对黄土坡面土壤水分入渗及再分布的影响

基于典型黄土的坡地人工降雨实验,对比研究了降雨、入渗及再分布规律;以雨强为主要影响因素,分析了降雨入渗及水分再分布过程中水土物质迁移的定量关系．结果表明,雨强变化对黄土坡面降雨入渗及土壤水分再分布的微观水分运动过程具有重要影响．雨强增大时,入渗和再分布湿润锋均随降雨历时延长而逐渐增加,但水分再分布过程的湿润锋增加速率比入渗慢得多;入渗湿润锋与时间关系可用幂函数表示,同时可表示为雨强的幂函数关系．再分布湿润锋与时间也存在定量关系．雨强越大,初始和稳定的土壤水分入渗率越高,累积入渗量随降雨时间增加得越快．此外,雨强越大,坡顶与坡脚湿润锋深度差异越小,坡面再分布过程的土壤含水量在各层的差异和递减趋势越明显．     

雨强对黄土坡面土壤水分入渗及再分布的影响

基于典型黄土的坡地人工降雨实验,对比研究了降雨、入渗及再分布规律;以雨强为主要影响因素,分析了降雨入渗及水分再分布过程中水土物质迁移的定量关系.结果表明,雨强变化对黄土坡面降雨入渗及土壤水分再分布的微观水分运动过程具有重要影响.雨强增大时,入渗和再分布湿润锋均随降雨历时延长而逐渐增加,但水分再分布过程的湿润锋增加速率比入渗慢得多;入渗湿润锋与时间关系可用幂函数表示,同时可表示为雨强的幂函数关系.再分布湿润锋与时间也存在定量关系.雨强越大,初始和稳定的土壤水分入渗率越高,累积入渗量随降雨时间增加得越快.此外,雨强越大,坡顶与坡脚湿润锋深度差异越小,坡面再分布过程的土壤含水量在各层的差异和递减趋势越明显.     

Ultrastructural localization of dentine phosphoprotein in rat tooth germs by immunogold staining

Summary Dentine phosphoprotein (DPP) was localized on thin frozen sections of fixed rat tooth germs by indirect immunogold staining. Antisera were directed against DPP and against glutaraldehyde-treated DPP and were characterized by immuno-electroblotting. In odontoblasts, DPP was found to be localized in the cisternae of the rough endoplasmic reticulum (RER) and the Golgi apparatus and in Golgi-associated vesicles. Odontoblastic processes were moderately positive for DPP and dentine was intensely labeled on frozen sections of unfixed tissue. Predentine showed a slight immunoreactivity. These results indicate the synthesis of DPP in the RER, its accumulation in the Golgi apparatus and its vesicular transport and secretion via the odontoblastic processes into dentine. The close association of the gold particles with the dentinal collagen fibres makes a role of DPP in linking mineral to collagen conceivable. Matrix vesicles were negative for DPP, suggesting that the protein is not present at the sites of matrix vesicleassociated nucleation.     

Sealing of open dentinal tubules by laser irradiation: AFM and SEM observations of dentine surfaces

Dentin of human teeth is a vital hydrated tissue. It is strongly sensitive to dehydration and drying that are commonly used in preparation of samples for scanning electron microscopy. Experience in examination of dentine surfaces of extracted human third molars using contact mode atomic force microscopy under moist conditions is described. The examined dentine surfaces are modified by laser radiation produced by a pulsed Nd:YAG laser that leads to sealing of open dentinal tubules under suitable conditions that are reached after covering dentine surfaces with dye agents. Out of four investigated dye agents erythrosin solution in water has been found the most suitable and the lower and upper limits of pulse energies for sealing of dentinal tubules have been set.     

Microleakage in composite resin restorations.

The aim of the present study was to evaluate the marginal microleakage of the newest generation of composite resin restorative materials. Class V restorations were prepared in human extracted teeth. Different combinations of restorative materials were used. All the materials tested showed marginal microleakage along the dentinal walls, suggesting that the adhesion value is not sufficient to counteract the composite shrinkage and to reduce the marginal space.     

Development and fine structure of pharyngeal replacement teeth in juvenile zebrafish (Danio rerio) (Teleostei, Cyprinidae)

Teeth are commonly used model systems for the study of epithelial-mesenchymal interactions during organogenesis. We describe here the ultrastructural characteristics of developing pharyngeal replacement teeth in juvenile zebrafish, an increasingly important model organism for vertebrate development. Replacement teeth develop in close association with the dental organ of a functional tooth. Morphogenesis is well advanced prior to the start of cytodifferentiation. Fibrillar enameloid matrix is formed first, followed by the deposition of predentine. Initial mineralization of the enameloid proceeds quickly; maturation involves the presence of ruffled-bordered ameloblasts. Dentine mineralization is inotropic and is mediated by matrix vesicles. Woven-fibred attachment bone matrix is deposited before completion of dentine mineralization. Eruption of fully ankylosed teeth is a fast process and may involve degenerative changes in the pharyngeal epithelium. Mononucleated osteoclasts and clastic cells located in the pulp cavity intervene in tooth resorption prior to shedding. Structural differences with larval, first-generation zebrafish teeth include the presence of dentinal tubules and the absence of an electron-dense covering membrane. Part of these differences may relate to size differences of the teeth. Others, like the site of the replacement tooth bud, suggest that initiation may take place in already committed epithelium from the first initiation event in the larval stage.     

原油污染对黄绵土和风沙土水分入渗的影响

原油进入土壤后会堵塞土壤孔隙,影响土壤斥水性,改变土壤水分运动状况。本研究利用土柱模拟的方法,研究了不同原油污染程度(0、0.5%、1%、2%、4%)对黄绵土和风沙土水分入渗过程的影响。结果表明: 随着原油含量的增加,两种土壤湿润锋的推进速度和入渗速率均减小,土壤原油污染程度为4%时湿润锋运移到土柱底部的所需时间最长,污染程度为0时湿润锋运移到土柱底部的所需时间最短,黄绵土湿润锋达到土柱底部所需最长时间是最短时间的5倍,风沙土最长时间是最短时间的48倍;当湿润锋运移到土柱底部时,黄绵土的累积入渗量随原油含量的增加而减小,而风沙土的累积入渗量先增大后减小;在高浓度(2%、4%)原油处理下,风沙土的累积入渗量曲线出现“翘尾”现象。Kostiakov入渗模型和Philip入渗模型比Green-Ampt模型能更好地模拟不同原油处理下的黄绵土土壤水分入渗过程,但对风沙土而言,两种模型对低浓度(0、0.5%、1%)原油处理的土壤水分入渗过程拟合较好。原油污染能够显著影响土壤水分入渗过程,且对风沙土的影响更大。     

How the microstructure of dentine can contribute to reconstructing developing dentitions and the lives of hominoids and hominins

Accounts of dentine microstructure are less well established in the primate life history literature than those of enamel microstructure. The aim of this paper is to draw some basic comparisons between enamel and dentine, but at the same time to show how dentine microstructure can make a major but different contribution to reconstructing past lives than enamel can. Dentine has both an organic and an inorganic component. The organic component contains growth factors, stable isotopes and DNA that survive long after death. The mineral component contains trace elements and preserves an incremental record of tooth growth. These can be used to put a time scale to many past events when the chemistry or microstructure of dentine has become altered during tooth growth. Dentine microstructure allows us to reconstruct tooth root growth in the past and has contributed to a fuller understanding of the modular nature of developing dentitions among hominoids and hominins.     

Visualization of glycosaminoglycans in rat incisor extracellular matrix using a hyaluronidase-gold complex

Summary The enzyme-gold technique was used on dental tissues. Hyaluronidase was complexed with gold, and ultrathin sections of rat incisors were incubated with the hyaluronidase-gold complex to localize chondroitin-sulphate and hyaluronic acid at the ultrastructural level. The hyaluronidase-gold complex was, found in predentine and dentine, especially at the mineralization front, in interglobular spaces and around dentinal canaficuli. The very young enamel was labelled, but not the later stages of formation. This method allowed a very precise localization of hyaluronic acid and/or chondroitin sulphate in rat incisors extracellular matrices. These findings support the important role of glycosaminoglycans in dentine mineralization.     

Scanning electron microscopy and dentinal permeability analysis of smear layer.

The aim of the present study was to evaluate the surface morphology and the permeability of dentine after different acid treatments: polyacrylic acid, maleic acid, phosphoric acid and saline solution as control. Dentine permeability was expressed as hydraulic conductance. All the acid treatments removed the smear layer and increased the dentine permeability.     

Leaching and transformation of urea in dry and wet soils as affected by irrigation water

Summary The leaching losses of urea in dry and wet soils as affected by the irrigation water, were studied in 90 cm long and 5 cm diameter plexiglass columns. In dry sandy loam soil urea leached with irrigation water and peaks of urea were observed with water front but in sandy soil the wetting front moved faster leaving the urea peak behind. In initially wet soils the urea peak did not coincide the wetting front, following infiltration and after redistribution for 24 hours of infiltration. More urea was recovered in sandy soil than in sandy loam soil following infiltration and redistribution for 24 hours. Urea leached only upto 30 cm with 5 and 7.5 cm irrigation water whereas with 10 and 15 cm irrigation water profiles urea penetrated to deeper layers. The sub-surface application of urea did not change the leaching behaviour of urea. Urea behaves as a non-reacting ion like Cl with respect to its movement with soil-water before it is hydrolysed.     

The structure and stratigraphy of<Emphasis Type="Italic">Speonesydrion</Emphasis> from New South Wales,Australia, and the dentition of primitive dipnoans

New material ofSpeonesydrion iani, an Early Devonian dipnoan from New South Wales, has provided additional Information on the dentition and jaws. Two new partial palates have been found, and X-rays of the parasphenoid shows that the structure is well preserved. The palatal teeth are well worn even in partly grown material, and they do not originate at a growth point, but at a thickening of the palate. More mandibles have been collected, and thin sections have been prepared to allow a discussion of their histology. On the mandible the teeth are clear, and they are much more defined than they are on the palate. The dental heel is variably developed, and grows in phases by thickening of the dentine at the contact with the bone. Dentine forms on the bone at the base of the heel, partly by Solution of the bone and the addition of dentine from the pulp canals, but also by direct growth from the pulp canals dorsal to the bone. In the latter case the dentine and bone are in contact, and the two tissues intermingle. The teeth are also formed on a thickened bone and consist of dentine capped with enamel making a crest. Dentine and bone are related as in the heel. We conclude that the teeth inSpeonesydrion are not homologous with the teeth in other dipnoans, and are formed by a different process involving the aggregation of denticles.     

间歇降雨和多场次降雨条件下黄土坡面土壤水分入渗特性

基于可控的坡面间歇降雨和多场次降雨试验,对黄土坡面土壤水分入渗及分布特征进行了研究.结果表明：间歇降雨条件下,两次降雨期间的累积径流量均随降雨历时的延长呈近似线性增加,湿润锋也随降雨时间的延长而增加;在两次降雨的间歇期,湿润锋增加缓慢.入渗率随着坡度的增大而减小,第2次降雨的入渗率随时间而减小的趋势更明显;15°坡面的累积入渗量比25°大,分别为178和88 mm.多场次降雨条件下,各场次降雨的初始入渗率均较高,其中第1场降雨的土壤入渗率、累积入渗量在各时段均明显高于其他场次,后3场降雨的入渗率差异不大;降雨场次越多,湿润锋越深.     

On the Importance of Hysteresis in Numerical Modeling of Surfactant-Induced Unsaturated Flow

It is known that surfactants can induce flow in unsaturated porous media due to the dependence of capillary pressure on surface tension. A commonly observed feature in systems with surfactant-induced flow is a transient wetting/drying/wetting sequence associated with the propagation of a surfactant solute front under monotonic flow conditions. Previous efforts to model surfactant-induced flow in relatively complex (e.g., two-dimensional systems) have not successfully incorporated hysteretic moisture retention properties. In this research, hysteretic, two-dimensional simulations of surfactant-induced flow were performed to assess the potential importance of considering hysteresis in such simulations. Hysteretic simulation results were compared to experimental data and to non-hysteretic simulations. The results suggest that the inclusion of hysteresis in numerical simulations can improve the match between simulated and experimental results in systems with surfactant-induced unsaturated flow. Furthermore, the inclusion of hysteresis in numerical simulations played a significant role in predicting the distribution of the contaminant and correct pressure head/moisture condition at the end of the experiment.     

Biomimetic Remineralization of Demineralized Dentine Using Scaffold of CMC/ACP Nanocomplexes in an In Vitro Tooth Model of Deep Caries

Currently, it is still a tough task for dentists to remineralize dentine in deep caries. The aim of this study was to remineralize demineralized dentine in a tooth model of deep caries using nanocomplexes of carboxymethyl chitosan/amorphous calcium phosphate (CMC/ACP) based on mimicking the stabilizing effect of dentine matrix protein 1 (DMP1) on ACP in the biomineralization of dentine. The experimental results indicate that CMC can stabilize ACP to form nanocomplexes of CMC/ACP, which is able to be processed into scaffolds by lyophilization. In the single-layer collagen model, ACP nanoparticles are released from scaffolds of CMC/ACP nanocomplexes dissolved and then infiltrate into collagen fibrils via the gap zones (40 nm) to accomplish intrafibrillar mineralization of collagen. With this method, the completely demineralized dentine was partially remineralized in the tooth mode. This is a bottom-up remineralizing strategy based on non-classical crystallization theory. Since nanocomplexes of CMC/ACP show a promising effect of remineralization on demineralized dentine via biomimetic strategy, thereby preserving dentinal tissue to the maximum extent possible, it would be a potential indirect pulp capping (IPC) material for the management of deep caries during vital pulp therapy based on the concept of minimally invasive dentistry (MID).     

Asymptotic analysis of the stress field in adhering dental restorations

Polymer-based composites are widely used in restorative dentistry as alternatives to metals and ceramics to fill cavities in teeth. They adhere to the walls of the cavity in the tooth, thus forming a composite body consisting of dentine, enamel, and composite resin. Geometric discontinuities along the interfaces between these materials can induce singularities in the stress field, which in turn lead to premature failure of the restoration. In the present investigation, a complex stress function technique is employed to derive the order of the stress singularity. It is shown that the order of the singularity depends on both the material properties of the restorative material and the local geometry of the cavity. It is also shown that the singularity in the stress field can be avoided through careful design of the cavity shape. The results presented correlate well with experimental results reported in the literature.     

Enamel and dentine ultrastructure in the early Jurassic therian Kuehneotherium

Three fragmentary molars of Kuehneotherium from Wales were progressively abraded by grinding and studied by scanning electron microscopy. A fourth molar was reduced to small blocks, thin sections of which were examined by transmission electron microscopy. Enamel showed a 'preprismatic' pattern, consisting of columns of crystals disposed as pinnae but not separated by an interprismatic substance. No enamel tubules were observed. Incremental lines were present. Inner dentine was permeated by numerous tubules not surrounded by peritubular dentine but a peripheral dentine layer adjacent to the enamel-dentine junction was atubular. Calcified deposits were occasionally observed in the lumen of dentine tubules, some of which were interpreted here as dentinal sclerosis consecutive to masticatory wear.