钾长石在白榴石合成中的应用

利用白榴石晶体的高膨胀性特点 ,解决烤瓷粉与金属合金之间的热匹配问题。以优质钾长石为主要原料 ,采取快速冷却的热处理制度合成白榴石熔块。X -线物相分析表明 ,熔块的主晶相为白榴石 ,熔块的平均热膨胀系数为 2 1.3× 10 - 6 /℃ ,为改善烤瓷粉与金属的热匹配提供了有利的条件。     

牙用遮色瓷热处理制度的研究

首次选用双相成核剂CaF2和TiO2为制备遮色瓷的成核剂，以SiO2-Al2O3-K2O-Na2O系统为其基质成分，采用差热分析仪，扫描电镜和x衍射分析仪等实验手段来探讨本体系遮色瓷制备的热处理制度。结果表明阶梯制度的热处理方式适用于本体系的遮色瓷。瓷粉经过如下的热处理制度：从室温以8℃／min的加热速度升温至750℃保温1h，然后再以4℃／min的升温速度升至960℃，保温2h后冷淬，其白榴石晶体的析晶行为良好，且晶体尺寸较小（约1μm左右）。该热处理制度的确定为改善遮色瓷与金属的热匹配性和提高遮色瓷的理化性能提供了基础。     

牙用遮色瓷热处理制度的研究

首次选用双相成核剂CaF2 和TiO2 为制备遮色瓷的成核剂 ,以SiO2 —Al2 O3 —K2 O—Na2 O系统为其基质成分 ,采用差热分析仪、扫描电镜和x衍射分析仪等实验手段来探讨本体系遮色瓷制备的热处理制度。结果表明阶梯制度的热处理方式适用于本体系的遮色瓷。瓷粉经过如下的热处理制度 :从室温以 8℃ /min的加热速度升温至 75 0℃保温 1h ,然后再以4℃ /min的升温速度升至 96 0℃ ,保温 2h后冷淬 ,其白榴石晶体的析晶行为良好 ,且晶体尺寸较小 (约 1μm左右 )。该热处理制度的确定为改善遮色瓷与金属的热匹配性和提高遮色瓷的理化性能提供了基础     

金属烤瓷牙中遮色瓷的制备

利用TiO2、CaF2等作为成核剂制备白榴石熔块和低熔点乳浊基础熔块,研制了热膨胀性符合要求的遮色瓷粉.试验结果表明,采用多相成核方法可得到含有大量白榴石晶体的熔块,在基础熔块中加入20%～25%的白榴石熔块后可获得与金属合金有良好热匹配的烤瓷粉.     

浅谈镍铬合金烤瓷牙的临床应用

烤瓷牙是临床上用于牙体美容,但是其中镍铬合金烤瓷冠,最近发现少数人对这种成分有过敏反应,本文就这个论题讨论镍铬合金烤瓷牙的临床应用.     

不同烤瓷牙内冠材料对产生龈缘黑线影响的分析

目的:分析镍铬合金,金合金材料制烤瓷内冠以及镍铬合金内冠涂制金粉对冠修复后产生龈缘黑线的影响.方法:对3052例烤瓷冠病例,分别用镍铬合金,金合金制作内冠以及运用金粉涂制镍铬合金内冠进行修复,经一年以上随访.对上述三种材料对产生龈缘黑线状况进行评价.结果:采用金合金制作内冠及对镍铬合金内冠粉制金涂制作烤瓷冠未产生龈缘黑线,而单纯用镍铬合金制作内冠,可能产生龈缘黑线.结论:镍铬合金烤瓷内冠不可避免会产生龈缘黑线,金合金烤瓷内冠避免了上述缺点,而镍铬合金内冠涂制金粉则是一条经济,实效的制作工艺.     

疑因镍铬合金烤瓷牙致白细胞数降低的病例分析

背景：镍铬合金烤瓷牙可引起过敏反应,其对全身脏器和功能的影响引起学者们的关注,尤其是对于肾脏和免疫系统的影响。 目的：针对临床中发现的1例疑因镍铬合金烤瓷牙导致白细胞数降低,进行报告和分析,探讨镍铬合金烤瓷牙对免疫系统的影响。 方法：对临床发现的特殊病例,检查全身和口腔状况,拆除可能致病的修复体,进行相关治疗后行全瓷冠修复,1个月后复查并对比治疗前后的血象。通过查阅文献资料分析镍铬合金烤瓷牙引起白细胞数降低的可能性。 结果与结论：从镍铬合金烤瓷牙的拆除及全瓷冠修复后的白细胞数改变,验证了镍铬合金烤瓷牙致白细胞数降低的推测。资料也表明镍铬合金烤瓷牙可通过一定途径对免疫功能产生影响,这应当引起口腔工作者的注意,采取一定措施,避免不良后果。     

以计算机数字图像处理和模式识别技术设计的烤瓷牙比色系统

背景：制备烤瓷牙时需要将患者牙齿与牙齿比色板比对得到患者牙齿的颜色编号,目前临床中常使用目测法,但这种方法会受到很多客观或主观的条件限制。 目的：设计能够进行图像采集,可实现牙齿比色功能的系统,并且尽量提高识别效果。 方法：利用摄像笔与暗室配合,采集牙齿比色板图像;数字图像处理方法提取图像颜色特征,分别使用最小距离法、K-近邻法和九分法对图像进行识别分类测试,观测分类结果是否满足需求。 结果与结论：利用最小距离法和K-近邻法可以进行识别分类,但由于数据承受量较低,会影响测试分类结果;利用九分法可以很大程度提高分类正确识别率,基本可以得到满意的结果。     

不同配方新型牙用玻璃陶瓷的显微结构与力学性能

背景:通过调整基础玻璃的成分和工艺制度可以得到各种符合预定性能的微晶玻璃.目的:通过不同配方制取以二硅酸锂为主晶相的玻璃陶瓷,晶化后对其力学性能和显微结构进行测定.方法:以二硅酸锂为主晶相,通过熔融法制备不同配方的G1、G2、G3号玻璃胚体,打磨、抛光,相对面互相平行.将G1、G2、G3号玻璃胚体进行晶化热处理(以10...     

一种抛光玻璃电极用的微熔炉

合格的玻璃电极是成功地进行单离子通道电流记录所必需的。为确保电极尖端与细胞膜形成十亿欧姆封接,要对直径1—5微米的电极尖端进行热抛光处理。本文介绍一种微熔炉,其加热部分为外径100微米的V形铂丝,以集成可调稳压元件SW317为核心制成可调直流稳压电源。     

Nanostructure of carious tooth enamel lesion

Carious lesions exhibit a complex structural organization composed of zones of higher and lower mineralization, formed by successive periods of cyclic de- and re-mineralization. A thorough understanding of the lesion morphology is necessary for the development of suitable treatments aiming to repair rather than replace the damaged tissue. This detailed understanding includes the entire lesion down to individual crystallites and nanopores within the natural organization of the crown. A moderate lesion, with surface loss and reaching dentin, and a very early lesion were studied. Scanning small-angle X-ray scattering (SAXS) with a pixel size of 20 × 20 μm² was used to characterize these lesions, allowing for the identification of distinct zones with varied absorption and scattering behavior, indicative of varied porosity and pore morphology. Despite these differences, the overall orientation and anisotropy of the SAXS signal was unaltered throughout both lesions, indicating that an anisotropic scaffold is still present in the lesion. The finding that crystallite orientation is preserved throughout the lesions facilitates the identification of preventive re-mineralizing strategies with the potential to recreate the original nanostructure.     

Deposition of cellular cementum onto hypoplastic enamel of fluorotic teeth in wild boars (Sus scrofa L.)

The nature of deposits present in hypoplastic defects of fluorotic enamel of wild boar teeth was studied by light microscopy and scanning electron microscopy. The fluorotic enamel showed different developmental abnormalities, denoting a severe disturbance of ameloblast function during the secretory stage of amelogenesis. These abnormalities included the occurrence of grossly accentuated incremental lines with associated zones of aprismatic enamel and the presence of different forms of hypoplastic defects. Two types of deposits were present on the hypoplastic enamel: cellular cementum and posteruptively acquired, presumably partially mineralized dental plaque. Coronal cementum is not normally formed in pig teeth. Presence of this tissue in fluorotic teeth of wild boars is seen as indicative of a premature disintegration of the enamel epithelium prior to the completion of amelogenesis. This was supposed to have resulted in a contact of mesenchymal cells of the dental follicle with the surface of the immature enamel and, in consequence, in a differentiation of these cells into cementoblasts. To our knowledge, this is the first study reporting the formation of coronal cementum as part of the spectrum of pathological changes in fluorotic teeth in a species whose tooth crowns are normally free of cementum.     

两种牙体预备方法制作玻璃纤维夹板固定松动前牙5年临床观察

背景：研究发现采用舌侧凹槽加邻面流体树脂牙体预备方法制作玻璃纤维夹板,用其固定松动前牙可达到较为理想的临床固定修复效果。 目的：观察两种牙体预备方法制作玻璃纤维夹板固定松动前牙5年基牙与夹板脱黏率及固定修复效果。 方法：根据慢性牙周病诊断标准,并严格按照牙周夹板固定适应证选取经过牙周基础治疗后需纤维夹板固定的94例Ⅱ-Ⅲ度前牙松动患者,根据松动患牙间是否进行邻面固定分为2组,邻面未固定组采用舌侧凹槽牙体预备方法,邻面固定组采用舌侧凹槽加邻面流体树脂牙体预备方法进行纤维夹板固定。随后5年中定期临床复诊或电话随访,对固定修复效果进行评价。 结果与结论：5年中定期临床复诊或电话随访显示,邻面固定组76例基牙与夹板脱黏7例,邻面未固定组18例基牙与夹板脱黏12例,均已经进行再固定。与邻面未固定组相比,邻面固定组5年后两组患牙的探诊深度、附着丧失明显改善(P  < 0.05),牙槽骨高度占根长的百分比增加(P < 0.05),患者自觉舒适无异物感。结果证实,采用舌侧凹槽加邻面流体树脂牙体预备方法制作玻璃纤维夹板固定松动前牙的5年观察固定效果较好。     

Compositional,structural and mechanical comparisons of normal enamel and hypomaturation enamel

Hypomaturation amelogenesis imperfecta is a hereditary disorder of the enamel that severely influences the function, aesthetics and psychosocial well-being of patients. In this study, we performed a thorough comparison of normal and hypomaturation enamel through a series of systematical tests on human permanent molars to understand the biomineralization process during pathological amelogenesis. The results of microcomputed tomography, scanning electron microscopy, Fourier transform infrared, Raman spectroscopy, microzone X-ray diffraction, thermal gravimetric analysis, energy diffraction spectrum and Vickers microhardness testing together show dramatic contrasts between hypomaturation enamel and normal enamel in terms of their hierarchical structures, spectral features, crystallographic characteristics, thermodynamic behavior, mineral distribution and mechanical property. Our current study highlights the importance of the organic matrix during the amelogenesis process. It is found that the retention of the organic matrix will influence the quantity, quality and distribution of mineral crystals, which will further demolish the hierarchical architecture of the enamel and affect the related mechanical property. In addition, the high carbonate content in hypomaturation enamel influences the crystallinity, crystal size and solubility of hydroxyapatite crystals. These results deepen our understanding of hypomaturation enamel biomineralization during amelogenesis, explain the clinical manifestations of hypomaturation enamel, provide fundamental evidence to help dentists choose optimal therapeutic strategies and lead to improved biofabrication and gene therapies.     

Scanning microscopy of platypus teeth

Summary Anorganic unerupted developing teeth and airdired erupted teeth of the platypus (Ornithorhynchus anatinus) were examined in a scanning electron microscope and in a tandem scanning reflected light microscope. Typically mammalian developing fronts of enamel and dentine were identified in the anorganic unerupted specimens. The developing teeth were particularly small and fragile and the enamel elusive and difficult to examine in the normal way for morphological detail. Prepared fractured surfaces of unerupted specimens revealed preferentially oriented crystallite groups in the enamel generally perpendicular to the developing front and a highly globular, mineralized pattern in the dentine with fine diameter, sparsely distributed dentinal tubules.Although optically homogeneous, the enamel of both developing and mature teeth displayed well-defined incremental lines, radial clefts, crystallite domains of variable size and outline, and fine tubules when examined by high contrast, back-scattered electron imaging. The enamel is prismatic only in part; well-formed, regular prisms not being a primary feature of platypus enamel. This can be related to the variability inherent in the developing surface and the thinness of the enamel layer. No surface was found which could be confidently identified as cementum; those developing surfaces not covered by enamel displaying small calcospherites which elsewhere marked the outer aspect of the dentine.     

Loss of teeth and enamel in tetrapods: fossil record, genetic data and morphological adaptations

Since their recruitment in the oral cavity, approximately 450 million years ago, teeth have been subjected to strong selective constraints due to the crucial role that they play in species survival. It is therefore quite surprising that the ability to develop functional teeth has subsequently been lost several times, independently, in various lineages. In this review, we concentrate our attention on tetrapods, the only vertebrate lineage in which several clades lack functional teeth from birth to adulthood. Indeed, in other lineages, teeth can be absent in adults but be functionally present in larvae and juveniles, can be absent in the oral cavity but exist in the pharyngeal region, or can develop on the upper jaw but be absent on the lower jaw. Here, we analyse the current data on toothless (edentate) tetrapod taxa, including information available on enamel-less species. Firstly, we provide an analysis of the dispersed and fragmentary morphological data published on the various living taxa concerned (and their extinct relatives) with the aim of tracing the origin of tooth or enamel loss, i.e. toads in Lissamphibia, turtles and birds in Sauropsida, and baleen whales, pangolins, anteaters, sloths, armadillos and aardvark in Mammalia. Secondly, we present current hypotheses on the genetic basis of tooth loss in the chicken and thirdly, we try to answer the question of how these taxa have survived tooth loss given the crucial importance of this tool. The loss of teeth (or only enamel) in all of these taxa was not lethal because it was always preceded in evolution by the pre-adaptation of a secondary tool (beak, baleens, elongated adhesive tongues or hypselodonty) useful for improving efficiency in food uptake. The positive selection of such secondary tools would have led to relaxed functional constraints on teeth and would have later compensated for the loss of teeth. These hypotheses raise numerous questions that will hopefully be answered in the near future.     

遗传性牙釉质发育不全家系的调查与分析

采用家系调查方法对一牙釉质发育不全患者的家系情况进行了调查 ,并绘制成系谱图进行遗传学分析。结果发现该家系中连续 5代都出现该病患者 ,且患者子女中发病率近 1 /2 ,亦无性别差异 ,其传递方式符合常染色体显性遗传的特点 ;根据患者的临床表现 ,按照Witkop对该类口腔疾病的分类方法 ,该家系的疾病属于遗传性牙釉质发育不全中的第三种类型 ,即遗传性牙釉质矿化不全症     

基于超声共振谱方法的人牙釉质材料力学特性研究

目的基于超声共振谱(resonant ultrasound spectroscopy,RUS)方法研究人牙釉质材料的力学特性。方法制作长方体状牙釉质样本。估计样本的理论共振频率,与RUS实验测量得到的样本实际共振频率相比较。基于迭代方法调整牙釉质弹性常数,使得理论共振频率和实验共振频率满足均方误差最小准则,并计算弹性模量、剪切模量与泊松比。结果牙釉质样本的弹性模量、剪切模量和泊松比范围分别为61.52~80.46 GPa、21.51~51.86 GPa和0.18~0.43。如果排除差异较大样本的影响,牙釉质的平均弹性模量、剪切模量和泊松比分别为72.84 GPa、31.94 GPa和0.27。结论 RUS方法在测量牙釉质力学特性方面具有可行性与重复性无损测量优势,一次测量就可以实现牙釉质所有弹性常数和力学参数的估计,研究结果为牙科修复材料的研发提供参考。     

Immunohistochemical localisation of amelogenin-like proteins and type I collagen and histochemical demonstration of sulphated glycoconjugates in developing enameloid and enamel matrices of the larval urodele (Triturus pyrrhogaster) teeth

The presence of collagen in enameloid distinguishes it clearly from true enamel, but little is known about the phylogenetic relationship between these 2 tissues. It has previously been reported that amelogenins are the principal proteins of the enamel matrix, that type I collagen and chondroitin sulphates are the predominant matrices in dentine, and that amphibian and reptilian aprismatic enamels contain no sulphated glycoconjugates, although certain sulphated substances are secreted into mammalian prismatic enamel during matrix formation. The larval urodele ( Triturus pyrrhogaster ) teeth are known to be composed of enameloid, dentine, and enamel-like tissue. To characterise the tooth matrices, the localisation of amelogenin-like proteins, type I collagen, and sulphated glycoconjugates was investigated. Chondroitin sulphates and fine fibrils immunoreactive for type I collagen were elaborated as the enameloid matrix inside the dental basement membrane. After the matrix had been deposited in full thickness, coarse collagen fibrils also immunoreactive for type I collagen and chondroitin sulphates were deposited below as the first dentine matrix. Further, enamel-like matrix with no collagen fibrils or sulphated glycoconjugates but strongly immunoreactive for amelogenins was deposited on the dentine. Although no immunolabelling for amelogenins was found over the enameloid matrix, at least at the formation stage, the zone of coarse collagen fibrils of dentine was partially immunoreactive as observed in mammalian mantle dentine. From the ontogeny and matrix constituents of larval urodele teeth, it is suggested that enameloid is originally a dentine-like tissue.