恒牙牙体硬组织钙磷成分的检测:分光光度法与EDTA滴定法（英文）

背景:目前酸蚀与黏结技术已经广泛应用于口腔临床,有资料表明年轻恒牙与成年恒牙的牙体硬组织中的主要无机元素钙和磷的含量有一定的差异。目的:通过分光光度法与EDTA滴定法测量年轻恒牙与成年恒牙的牙釉质与牙本质中主要无机元素(钙、磷)的含量。方法:年轻恒牙与成年恒牙离体牙各20颗,用生石膏和水混合,待近干时,将牙齿垂直铸于其中,使牙面暴露。用syj-200精密切割机将模型切割成切片,然后将切片放入浓硝酸中,通过加热器使之溶解,然后制备成标准溶液,最后采用分光光度法与滴定法分别测量两者硬组织的钙和磷的浓度。结果与结论:结果证实,年轻恒牙的牙体硬组织钙磷含量和钙/磷比值小于成年恒牙(P0.05),说明有机物含量较成年恒牙多;矿化程度低于成年恒牙(P0.05),相对于成年恒牙更加耐酸,临床操作可适当延长对年轻恒牙的酸蚀时间,以达到更佳的酸蚀效果。     

人胎子宫发育的体视学研究

目的：探讨人胎儿子宫发育过程细胞核质变化规律。材料与方法：利用体视学原理,对３３例胎龄１４～３５周人胎儿子宫内层及肌层厚度、细胞核平均体积、核浆比、粗面内质网表面积密度等体视学参数进行测算。结果：在胎龄１４～２５周期间,胎儿子宫内层随胎龄增长,其组织厚度、细胞核浆比以及粗面内质网表面积密度均无显著变化,细胞核平均体积显著增大。 胎龄２６～２９周,内层组织厚度增长迅速,细胞核浆比显著降低,粗面内质网     

遗传性乳光牙与正常恒牙牙本质表面形貌及元素分布和显微硬度的差异

背景:目前国内外对遗传性乳光牙本质的研究主要集中于牙本质发育异常家系调查和表型分析,对遗传性乳光牙本质的物理性能的研究鲜有报道。目的:对比研究遗传性乳光牙与正常恒牙的牙本质的表面形貌,元素分布以及显微硬度的差异。方法:收集3例遗传性乳光牙本质患者需要拔除的牙齿,共5颗。选择年龄、性别相匹配的无龋坏的正畸牙作为对照的正常恒牙。采用扫描电镜,X射线能量色谱仪,纳米压痕仪对遗传性乳光牙和正常恒牙的牙本质进行表面形貌观察,元素分布以及显微硬度进行测试。结果与结论:遗传性乳光牙的牙本质结构松散,牙本质小管结构改变;遗传性乳光牙的牙本质中钠、锌、硫、钙含量显著高于正常恒牙,而镁、磷、氯降低正常恒牙(P0.01);遗传性乳光牙的牙本质中钙/磷比值为1.76,明显高于正常恒牙(P0.01)。遗传性乳光牙的牙本质的显微硬度是(1.18±0.18)GPa,明显低于正常恒牙牙本质的显微硬度(1.72±0.48)GPa(P0.01)。因此,说明遗传性乳光牙本质小管结构发生改变,其硬度低于正常恒牙牙本质的硬度,这可能与遗传性乳光牙本质元素分布有关。     

人上颌切牙邻面牙釉厚度的X光片比较

通过对牙釉牙厚度的测量比较,分析不同性别、不同牙位及牙齿不同部位间牙釉质厚度的差异,探讨其原因及意义。方法：利用临床Ｘ光检查,对１４至１９岁青少年的上颌切牙进行摄片测量,并进行统计学分析。结果：人上颌切牙邻面的牙釉质厚度在不同性别和不同牙位之间均无显著性差异,但位于近中面和远中面的牙釉质厚度比较则差异显著。结论：牙釉质的厚度与所行使的功能以及牙胚发育期的造釉细胞功能相关     

微波技术在制作牙体组织切片中应用

牙体组织由牙釉质、牙本质、牙骨质3种钙化的硬组织和1种牙髓组织组成。因其十分坚硬,渗透性极差,脱钙、浸蜡时间均较长,制作完整的切片较困难。我们在制作牙体组织切片的实际工作中体会到采用微波技术处理牙体组织,制作常规石蜡切片及进行免疫组化染色过程中,注意在关键环节上的处理,可缩短制作周期,并获得令人满意的效果。     

人胎儿子宫发育的体视学研究

目的探讨人胎儿子宫发育过程细胞核质变化规律。材料与方法利用体视学原理,对 33 例胎龄 14～35 周人胎儿子宫内层及肌层厚度、细胞核平均体积、核浆比、粗面内质网表面积密度等体视学参数进行测算。结果在胎龄 14～25 周期间,胎儿子宫内层随胎龄增长,其组织厚度、细胞核浆比以及粗面内质网表面积密度均无显著变化,细胞核平均体积显著增大。胎龄 26～29 周,内层组织厚度增长迅速,细胞核浆比显著降低,粗面内质网表面积密度迅速增加,细胞核平均体积显著减小,肌层随胎龄增长细胞核浆比逐渐降低,粗面内质网表面积密度显著增加,细胞核平均体积无明显变化。结论胎龄 26～29 周是胎儿子宫发育的重要时期。     

人天然牙的高分辨X线微区衍射分析

通过使用X线微区衍射法直接对人天然牙表面正常牙釉质、牙本质及龋坏组织三个测量点进行检测,以测试X'pert Pro型衍射仪对人天然牙正常和早期龋损组织晶体结构改变的检测能力.结果显示,牙磷灰石由多种物相构成,是一种生物混晶,主要物相为羟基磷灰石,龋坏组织中可能有新物相的形成.从正常牙釉质到牙本质再到龋坏组织,晶体a轴逐渐增大,c轴基本不变.晶体晶胞参数计算结果:正常牙釉a=9.550(A),c=6.883(A);正常牙本质a=9.554(A),c=6.883(A);龋坏组织a=9.558(A),c=6.884(A).晶粒尺寸计算结果:正常牙釉质D002=27.600 nm;正常牙本质D002=16.561 nm;龋坏组织D002=13.163 nm.结晶性:正常牙釉质＞正常牙本质＞龋坏组织.结果表明采用新型高分辨X线衍射仪可以非常方便地对牙齿进行X线衍射微区分析.     

不同年龄组修复性牙本质生成情况探讨

目的观察不同年龄段人的牙齿在受到龋损刺激后,修复性牙本质的生成情况.方法收集5组不同年龄组含有牙本质浅层龋的离体牙,每组各5颗牙齿.制作标本切片,HE染色,显微镜下观察.测量修复性牙本质厚度,作统计学检验.结果5组不同年龄牙齿的修复性牙本质平均厚度分别为:3.36、2.6、2.8、4.2、3.36,统计学检验无明显差异.结论受龋损刺激后,不同年龄牙齿的修复性牙本质生成情况无明显差异.     

人体天然牙骨牙本质界面区元素分布变化的电子探针微区分析

采用电子探针能谱微区分析方法初步测定了天然牙牙体组织牙骨质牙本质界面区的钙（Ｃａ）、磷（Ｐ）和硫（Ｓ）三种元素的分布变化特点，以考察人体天然牙硬组织中的无机和有机成分在骨牙本质界面区的分布变化特点。实验结果表明：骨牙本质界面区的Ｃａ、Ｐ元素的分布变化波动幅度较小，在骨牙本质界面区牙骨质和牙本质中的Ｃａ、Ｐ、Ｓ元素的平均重量百分比Ｃｉ值都变化不大，提示牙体组织中的无机和有机成分在骨牙本质界面区的分布未随着牙体组织解剖结构的改变而发生明显变化。     

数字化全牙列下颌骨三维解剖建模

目的探讨建立具有高质量牙列的下颌骨三维数字化解剖模型。方法用激光扫描获取1套标准下颌牙列解剖标本的精确三维模型,用CT扫描数据重建下颌骨三维模型,使用基于几何和图像解剖标志的配准变形方法将每颗牙齿模型对齐融合到下颌骨模型,进一步生成牙齿的牙釉质、牙本质、牙周膜。结果成功建立了具有高质量牙列的下颌骨三维数字化解剖模型,每颗牙齿具有牙冠细节和完整的牙根,区分牙釉质、牙本质、牙周膜,可以对任意解剖区域放大和旋转观察,显示解剖标志。结论高质量牙列的下颌骨三维数字化解剖模型具有逼真的三维显象和方便的教学学习功能,可用于口腔、颌面、解剖等多个学科。     

Quantitative analysis of the calcium and phosphorus content of developing and permanent human teeth.

It was the aim of this study to investigate the distribution of Ca, P and C in predentin, dentin and enamel in human tooth buds and permanent teeth by EDX element analysis. The mandible of a 16-week-old human fetus containing eight mineralizing tooth buds and three human permanent molars were fixed in formaldehyde and embedded in Technovit 9100. Serial sections of 80 microm thickness of the mandible were cut in the frontal-dorsal direction, and polarized light micrographs were taken of these sections. The permanent teeth were cut in mesio-distal direction. The sections were investigated with scanning electron microscopy and EDX element analysis with a Philips XL 30 FEG scanning microscope and an EDAX energy-dispersive X-ray system using spot measurements, EDX line-scans and element mapping. Quantitative measurements were made in predentin, mineralizing dentin adjacent to predentin, mature dentin, mineralizing enamel and young enamel of developing teeth and mature enamel of permanent teeth. In developing teeth the Ca and P content increased rapidly from outer predentin towards mineralizing dentin. In enamel prisms of developing teeth the Ca and P content increased linearly from the surface towards the enamel-dentin junction. In permanent teeth only a small layer of predentin was found. The Ca and P content in enamel and circumpulpal dentin of permanent teeth was higher than in developing teeth. The Ca/P ratio differed between predentin and dentin areas reflecting different calcium phosphate compositions, but it was the same in mineralizing and young enamel. The differences in the distribution of Ca and P reflect different mineralizing patterns of the enamel and dentin matrices.     

Effect of Down syndrome on the dimensions of dental crowns and tissues

Abnormal growth in Down syndrome (DS) is reflected by variable reduction in size and simplification in form of many physical traits. This study aimed to compare the thickness of enamel and dentine in deciduous and permanent mandibular incisor teeth between DS and non‐DS individuals and to clarify how these tissues contribute to altered tooth size in DS. Sample groups comprised 61 mandibular incisors (29 permanent and 32 deciduous) from DS individuals and 55 mandibular incisors (29 permanent and 26 deciduous) from non‐DS individuals. Maximum mesiodistal and labiolingual crown dimensions were measured initially, then the crowns were sectioned midsagittally and photographed using a stereomicroscope. Linear measurements of enamel and dentine thickness were obtained on the labial and lingual surfaces of the crowns, together with enamel and dentine–pulp areas and lengths of the dentino‐enamel junction. Reduced permanent crown size in DS was associated with a reduction in both enamel and dentine thickness. After adjustments were made for tooth size, DS permanent incisors had significantly thinner enamel than non‐DS permanent teeth. The DS permanent teeth also exhibited significant differences in shape and greater variability in dimensions than the non‐DS permanent teeth. Crown dimensions of deciduous incisors were similar in size or larger in DS compared with non‐DS deciduous teeth. Enamel and dentine thicknesses of the deciduous teeth were similar in DS and non‐DS individuals. The findings indicate that growth retardation in DS reduces both enamel and dentine deposition in the permanent incisors but not in the earlier‐forming deciduous predecessors. The results are also consistent with the concept of amplified developmental instability for dental traits in DS. Am. J. Hum. Biol. 13:690–698, 2001. © 2001 Wiley‐Liss, Inc.     

Enamel biorhythms of humans and great apes: the Havers‐Halberg Oscillation hypothesis reconsidered

The Havers‐Halberg Oscillation (HHO) hypothesis links evidence for the timing of a biorhythm retained in permanent tooth enamel (Retzius periodicity) to adult body mass and life history traits across mammals. Potentially, these links provide a way to access life history of fossil species from teeth. Recently we assessed intra‐specific predictions of the HHO on human children. We reported Retzius periodicity (RP) corresponded with enamel thickness, and cusp formation time, when calculated from isolated deciduous teeth. We proposed the biorhythm might not remain constant within an individual. Here, we test our findings. RP is compared between deciduous second and permanent first molars within the maxillae of four human children. Following this, we report the first RPs for deciduous teeth from modern great apes (n = 4), and compare these with new data for permanent teeth (n = 18) from these species, as well as with previously published values. We also explore RP in teeth that retain hypoplastic defects. Results show RP changed within the maxilla of each child, from thinner to thicker enameled molars, and from one side of a hypoplastic defect to the other. When considered alongside correlations between RP and cusp formation time, these observations provide further evidence that RP is associated with enamel growth processes and does not always remain constant within an individual. RP of 5 days for great ape deciduous teeth lay below the lowermost range of those from permanent teeth of modern orangutan and gorilla, and within the lowermost range of RPs from chimpanzee permanent teeth. Our data suggest associations between RP and enamel growth processes of humans might extend to great apes. These findings provide a new framework from which to develop the HHO hypothesis, which can incorporate enamel growth along with other physiological systems. Applications of the HHO to fossil teeth should avoid transferring RP between deciduous and permanent enamel, or including hypoplastic teeth.     

Forensic study of sex determination using PCR on teeth samples

In this study, sex determination using polymerase chain reaction (PCR) on tooth material was evaluated from the viewpoint of forensic medicine. The sensitivity of PCR for detection of the Y chromosome-specific alphoid repeat sequence and the X chromosome-specific alphoid repeat sequence was 0.5 pg of genomic DNA. Sex could be determined by PCR of DNA extracted from the pulp of 16 freshly extracted permanent teeth and dentine including the surface of the pulp cavity of 6 freshly extracted milk teeth. Sex could be determined using the pulp in all 20 teeth (10 male and 10 female) preserved at room temperature for 22 years. For the pulp of teeth stored in sea water, the sex could be determined in all 8 teeth immersed for 1 week and in 5 of 6 teeth immersed for 4 weeks. In the remaining 1 tooth, in which sex determination based on the pulp failed, the sex could be determined correctly when DNA extracted from the tooth hard tissue was examined. For teeth stored in soil, the sex could be determined accurately in all 8 teeth buried for 1 week, 7 of 8 teeth buried for 4 weeks, and in all 6 teeth buried for 8 weeks. When teeth were heated for 30 min, sex determination from the pulp was possible in all teeth heated to 100, 150, and 200 degrees C, and even in some teeth heated to 250 degrees C. When this method was applied to actual forensic cases, the sex of a mummified body estimated to have been discovered half a year to 1 year after death could be determined readily by examination of the dental pulp. In the skeletons of 2 bodies placed under water for approximately 1 year and approximately 11 years and 7 months, pulp tissues had been dissolved and lost, but sex determination was possible using DNA extracted from hard dental tissues. These results indicate that this method is useful in forensic practices for sex determination based on teeth samples.     

Comparison between deciduous and permanent incisor teeth in morphology of bovine enamel.

Functional incisor teeth (deciduous and permanent teeth) from Bovidae (14 species) were prepared for scanning electron microscopic observation. Ultrastructural patterns of the enamel layer of deciduous and permanent incisor teeth varied (ex. prisms, arrangement pattern of matrices, and in thickness of enamel layer) in each species. The ultrastructures of prisms in longitudinal sections were classified into three types; A, radial, B, tangential, and C, mix of A and B arrangement enamel; modified Koenigswald's method (1982) in examined species. Type A was found in a large part of permanent and a small part of deciduous incisor teeth, while types B and C were mainly found in the deciduous teeth. These morphological features show the remarkable correlation between permanent and deciduous teeth.     

The dental pathology of northern elephant seals (Mirounga angustirostris)

Skulls (n=104) of northern elephant seals from California were examined macroscopically. The animals varied in age but the numbers of each sex were roughly equal. The majority (86%) of teeth were available for examination. The mandibular first premolars were the most common teeth to be congenitally absent, with 2.3% missing. Supernumerary teeth (usually a supplemental mandibular molar) were associated with only 1.4% of normal teeth (or empty alveolar sockets). At least one persistent deciduous tooth was present in 38% of skulls, 70% of which were juvenile skulls. The majority (95.8%) of premolars had the type 2a tooth form, with only 3.8% and 0.5% of type 2b and 2c, respectively. Forty-six skulls, of which 43 were from adults, showed signs of attrition. Tooth fractures were uncommon, affecting only 33 teeth (1.2%). One skull showed an "incremental line" suggestive of enamel hypoplasia. Periodontal hard tissue lesions were seen in 44.3% of all teeth present (46.0% of skulls). Six cases of periapical disease with bone loss were observed.     

Dental Defects as a Potential Indicator of Chronic Malnutrition in a Population of Fallow Deer (Dama dama) from Northwestern Germany

We studied enamel defects in mandibular cheek teeth of fallow deer from an enclosed population that had grown far beyond the carrying capacity of its habitat. Macroscopic inspection revealed a high frequency of pathological enamel alterations in the permanent premolars and the third molar, which form late during dental development, while earlier forming teeth (deciduous premolars and first molar) were generally not affected. Macroscopic enamel alterations comprised opacity and posteruptive discoloration, loss of occlusal enamel ridges, and presence of enamel surface lesions. Backscattered electron imaging in the SEM revealed a marked hypomineralization and related increased porosity of the outer compared to the central and inner enamel portions in the affected teeth. In contrast, the enamel of the unaffected first molars showed a homogeneous high degree of mineralization. Microindentation hardness testing demonstrated a significantly reduced and highly variable hardness of the outer enamel of the affected teeth. The recorded enamel alterations are indicative of a disturbance of enamel maturation. Based on findings of experimental studies by other authors that explored the effects of dietary deficiencies on the mineralization of dental hard tissues in different mammal species, we suggest a dietary calcium deficiency as the cause of the observed pathological enamel changes in the fallow deer. The supposed calcium deficiency only affected teeth whose crown mineralization takes place after weaning, while the deciduous premolars and the first molar, whose crown formation occurs prenatally or during the early postnatal period of intense milk feeding, were unaffected. Anat Rec, 299:1409–1423, 2016. © 2016 Wiley Periodicals, Inc.     

Development of coronal cementum in hypsodont horse cheek teeth

The horse is a grazing herbivore whose cheek teeth are hypsodon; that is, they possess long crowns that are completely covered by coronal cement at eruption. For elucidation of the sequential events in the formation of this coronal cementum in the mandibular horse cheek teeth, in the present study the lower 3rd permanent premolar teeth (PM₄) from 3.5‐, 4‐, and 5‐year‐old horses were compared by using radiography, microcomputed tomography (Miro‐CT), light microscopy (LM), and scanning electron microscopy (SEM). The present study clearly showed that prior to coronal cementogenesis tartrate‐resistant acid phosphatase (TRAP)‐positive odontoclasts resorbed on the enamel surface of the reserve crown in horse cheek tooth. Enamel resorption areas were relatively narrow, and started from the cuspal tips, and moved in the apical direction during tooth development. A primary cementum was initially deposited on the irregularly pitted enamel–cementum junction (ECJ) of the infolding and peripheral enamel. The infolding cementum filled grooves completely by the time of tooth eruption. On the other hand, in the peripheral cementum, the secondary and tertiary cementum layers were sequentially deposited on the primary cementum. These two cementum layers were sites for the insertion of the periodontal ligaments, and were continually laid down on the primary cementum coronally rather than apically throughout the life. The results of the present study suggest that the coronal cementum of horse cheek teeth is a multistructural and multifunctional tissue, meeting the requirements of its many different functions. Anat Rec, 297:716–730, 2014. © 2014 Wiley Periodicals, Inc.     

Congenital absence of permanent teeth in a six‐generation Chinese kindred

We report on rare, heritable, permanent tooth agenesis in a large Chinese kindred. The congenital absence of permanent teeth except the first and second accessory teeth was observed in 52 individuals through six successive generations in the kindred comprising 328 members. Clinical assessments were carried out, and inheritance mode and spousal influence of the anomaly on their offspring were analyzed. Consequently, the anomaly was transmitted in an autosomal dominant fashion with incomplete penetrance (P = 0.88), and no significant clinical manifestations other than the oligodontia were found. A geographical or environmental effect on the affected individuals was obviously eliminated, because any who are related to the kindred but live under the same conditions are fully healthy. The disorder we describe, therefore, differs from any previously reported oligodontia/anodontia syndromes. The oligodontia ranged from a few teeth to the whole set of teeth, and usually occurred at a period from age 7 or 8 years, the time when primary teeth are normally replaced by permanent teeth, to the forties. Roentgenography of the affected persons indicated that only the first and/or second accessory teeth with tooth buds developed as permanent teeth. In fact, the diphyodontic germination sometimes occurred in the oral cavity of the affected individuals. Am. J. Med. Genet. 90:193–198, 2000. © 2000 Wiley‐Liss, Inc.     

Squamate egg tooth development revisited using three-dimensional reconstructions of brown anole (Anolis sagrei,Squamata, Dactyloidae) dentition

The egg tooth is a hatching adaptation, characteristic of all squamates. In brown anole embryos, the first tooth that starts differentiating is the egg tooth. It develops from a single tooth germ and, similar to the regular dentition of all the other vertebrates, the differentiating egg tooth of the brown anole passes through classic morphological and developmental stages named according to the shape of the dental epithelium: epithelial thickening, dental lamina, tooth bud, cap and bell stages. The differentiating egg tooth consists of three parts: the enamel organ, hard tissues and dental pulp. Shortly before hatching, the egg tooth connects with the premaxilla. Attachment tissue of the egg tooth does not undergo mineralization, which makes it different from the other teeth of most squamates. After hatching, odontoclasts are involved in resorption of the egg tooth's remains. This study shows that the brown anole egg tooth does not completely conform to previous reports describing iguanomorph egg teeth and reveals a need to investigate its development in the context of squamate phylogeny.