Controlled Deposition of HAp Mimicking Tooth Enamel

Chemical compositions and mierosturcture of mature human tooth enamel were investigated by XRD , FTIR and SEM to further understand the characteristics of tooth enamel. In order to obtain apatite crystals chemically and structurally similar to those in tooth enamel, biomimetic way was employed. Self-assembled monolyers terminated with-SO3 H groups were used as deposition substrates and 1.5 SBF （ the concentrations of Ca^2＋ and PO4^3- ions 1.5 times ttum those in simulated body fluid ） with and without 5 ppm F^- were used as soaking medium. The XRD and FTIR results showed that both the deposited fluoride-substituted hydroxyapatite （ F-HAp ） crystals in 1.5 SBF with F^- and hydroxyapatite （ HAp ） crystals in 1.5 SBF were carbonate-contain ing, mimicking human tooth enamel in chemical compositions. The SEM photos showed that needle-like F-HAp crystals had large aspect ratios and grew in bundles, which were similar to the crystals in human tooth enomel. The results provide available information on dental restoration.

XRD Characterization of Crystallinity of Human Tooth Enamel under Influence of Mechanical Grinding

Crystallinity refers to the degree of structural order in a solid and has a big influence on hardness, density, transparency and diffusion. Even within materials that are crystalline completely, the degree of structural perfection can vary, reflecting size and elastic strain of many independent crystalline regions (grains or crystallites) of which these materials are composed. In this work it was attempted to reduce the crystallinity of human enamel using a technique of mechanical grinding (MG) with an ultra-compact FRITSCH Mini-Mill PULVERISETTE 23 machine. Variation in the crystallinity through the MG was monitored by X-ray diffraction (XRD) by broadening of the diffraction peak and examined using the Williamson-Hall plot method. Crystallites in human enamel are regularly arranged and oriented (in the [001] direction) perpendicularly to the interface of enameldentin junction. The results showed an anisotropic feature in crystallinity. Reduction of the crystallinity along the a-axis is due to the crystal strain rather than to the refinement of crystal, and vice versa along the c-axis. After 230 h of the MG, the length of crystallites decreased from 100 nm to 30 nm and width from 40 nm to 37 nm approximately.

Stable isotopes of modern herbivore tooth enamel in the Tibetan Plateau: Implications for paleoelevation reconstructions

Fossil tooth enamel from herbivores is considered one of the best proxies for paleoclimate and paleoelevation reconstructions, due to its low susceptibility to diagenetic alteration. A synthesis of oxygen and carbon isotope analyses of modern tooth enamel from herbivores such as Tibetan yaks, asses and antelopes is assessed. The average δ 13C(PDB) value of herbivore tooth enamel in the Lhasa and south Qiangtang terrains is-11.3‰± 1.1‰, whereas in the north Qiangtang and Hoh Xil terrains value is-10.2‰± 1.4‰ consistent with the current C3-dominant ecotype in the Tibetan Plateau. In addition, the average δ18O(PDB) values from tooth enamel show a northward systematic increase from-11.8‰± 3.4‰ in the Gyirong Basin, to-11.1‰± 1.1‰ in the Lhasa and southern Qiangtang terrains, and then to-9.0‰± 1.1‰ in the northern Qiangtang and the Hoh Xil areas, similar to those of the local river water and precipitation variation trends. It is suggested that δ 18O(PDB) values of tooth enamel should not be used directly to evaluate the paleo-elevation of the Tibetan Plateau, because oxygen isotopic composition from tooth enamel is a com-bination of drinking water (precipitation-and river-sourced) and diet (plant-sourced). Moreover, an empirical relationship between oxygen isotope of tooth enamel and modern river water, and as well as elevation is recommended, which can be used in future studies of Tibetan Plateau paleoelevation.

Reconstructing past subsistence patterns on Zhongba Site using stable carbon and oxygen isotopes of fossil tooth enamel

The oxygen and carbon isotopic ratios in human and animal tooth enamel were measured to reconstruct the subsistence patterns on Zhongba Site between 2400 and 4200 aBP.The results indicate that human consumed chiefly C4 resources,such as millet,and the C3 plants,such as rice and wheat,constituted only a small fraction of the human diets,normally no more than 15%.There are significant differences in food sources between human and pig,and the percentages of C3 plants in pig diets were higher than those in human diets.But theδ13C values of pig partially overlap those of human,demonstrating some similarities in their food sources.The differences in water sources between human and pig are significant.There are significant differences in food and water sources between cattle and deer. This indicates that the two kinds of mammals subsisted in different niches.But theirδ13C values also partially overlap each other,suggesting some similarities in their food sources.There are both signifi- cant differences in meanδ13C andδ18O values between the omnivores,human and pig and the herbi- vores,cattle and deer,implying significant differences in food and water sources between the two categories.During the period the dietary habits of human had not changed,but the pig breeding strategies had changed,from breeding in house to breeding in confinement,and the proportion of C3 plants in pig food increased with time.The scope of human migration had been considerably large by the Warring States because of the development of productive forces.

Automatic modeling together with numerical simulation of the different-scale microstructures of human tooth enamels

The present paper aims to develop an automatical strategy for generating accurate different-scale microstructures of human tooth enamels(HTEs),and to elaborate a numerical scheme for simulating their elastic responses.At first,the strong governing formulation of these microstructures is briefly constructed,and the relevant weak formulation is then deduced based on the virtual work theorem.Afterwards,a subdividing approach,which cuts the elements intercepted by the interfaces between distinct phases automatically,is established with the aid of the level set method(LSM),and the discrete counterpart of the governing formula is obtained by combining the weak formulation derived and a discretized model.To be noted,two silent merits are found when the elaborated strategy is applied:(1) the continents constituting the microstructures of different scales can be arbitrarily-shaped and conveniently reproduced;(2) the periodic boundary condition commonly employed can be enforced on the external surfaces of representative unit cells(RUCs) with no difficulty.Besides,a boundary value problem(BVP) involving a simplified HTE nanostructure is designed,analytically solved,and hereafter applied to verify the correctness of the proposed strategy.It is observed that both the displacement and stress predictions by the computational approach are in good agreement with the relevant analytical results irrespective of the material combinations applied.Eventually,discussions are made on the influence of material organizations of both the 2D and 3D HTE microstructures at the ultrastructural and repeated rod levels,and some concluding remarks are drawn.

基于自我效能理论系统的口腔健康管理对正畸牙釉质脱矿患者的干预效果

目的 研究基于自我效能理论系统的口腔健康管理对正畸牙釉质脱矿患者口腔健康自理能力和脱矿程度的干预效果。方法 采用便利抽样法,选择2022年3月至9月在南京医科大学附属口腔医院固定矫治的120例受试者进行牙釉质脱矿筛查,按照随机数字表法将其分为观察组(n=60)与对照组(n=60)。对照组接受常规护理干预,观察组在对照组的基础上实施基于自我效能理论系统的口腔健康管理,分别在基线(T0)、干预6个月(T1)以及12个月(T2)时评定患者的自我效能感、口腔健康自理能力和牙釉质脱矿指数(EDI)。结果 重复测量方差分析结果显示,干预后,不同时间点观察组患者健康行为自我效能感量表得分和口腔健康自理能力得分均高于干预前和对照组,差异有统计学意义(P<0.05);在T2时观察组患者牙釉质脱矿指数为(0.16±0.09),显著低于对照组的(0.48±0.28),差异具有统计学意义(P<0.05)。结论 基于自我效能理论系统的口腔健康管理可提高正畸牙釉质脱矿患者的自我效能感和口腔健康自理能力、降低牙釉质脱矿率,有效改善口腔卫生情况。

钙离子在牙釉质矿化中的作用

牙釉质的矿化形成是一个信号分子贯穿始终的过程,釉质矿化通过细胞内多种离子与信号通道的紧密调节和上皮与间充质的相互作用,最终使牙釉质成为人体中矿化程度最高、最硬的组织。Ca^(2+)作为细胞内重要的第二信使分子,在生物矿化中调节许多过程,其中就包括调节釉质蛋白的表达。在牙釉质的基本结构羟基磷灰石晶体中,约含有60%质量的Ca^(2+),由此可见Ca^(2+)是牙釉质的关键和必需成分。因此,Ca^(2+)的正常转运在牙釉质矿化过程中起着关键作用。

原子力显微镜对牙釉质脱矿再矿化的分析

原子力显微镜是一种无须样本前处理的集形貌直观化和数据量化为一体的高分辨检测工具。利用原子力显微镜直观观察牙釉质脱矿及再矿化的微观形貌,并量化分析粗糙度和细菌黏附力。采用扫描电子显微镜和显微硬度计进行形貌观察和硬度值量化,验证原子力显微镜对牙釉质脱矿及再矿化的成像和量化效果。结果表明,随着脱矿时间的增加,牙釉质表面结构疏松,粗糙度增大;经过再矿化处理后,随着再矿化时间的增加,表面变得更为紧致,粗糙度降低。其他表征方法获得相似的结果,验证了原子力显微技术检测分析的可靠性。

Tooth Mousse护牙素与氟化钠联合用于正畸釉质脱矿的临床研究

目的:观察Tooth Mousse护牙素与氟化物联合使用预防正畸釉质脱矿的效果。方法:选择固定正畸患者82例,采用自身对照法,A区侧切牙和尖牙戴入托槽后使用0.2%氟化纳漱口3min后,再在托槽周围涂护牙素,保留5min,B区同名牙仅用0.2%氟化钠漱口。每半月复诊重复操作,1年后观察两区牙釉质脱矿程度和牙釉质脱矿率,对其进行比较。结果:1年后A区牙釉质脱矿率低于B区,比较差异有统计学意义。结论:护牙素与氟化物有协同作用,可以减少正畸牙釉质脱矿,促进再矿化。

司米护齿涂剂治疗正畸过程中牙釉质脱矿的有效性和安全性分析

目的 探讨司米护齿涂剂治疗正畸过程中牙釉质脱矿(ED)的临床效果。方法 择取68例正畸治疗的错颌畸形患者,随机分为对照组与实验组,每组34例。对照组给予多乐氟氟化钠护齿剂,实验组给予司米护齿涂剂。对比两组治疗后的牙周情况[菌斑指数、改良出血指数(mBI)]、ED发生率及牙釉质脱矿指数(EDI)。结果 治疗后6、9、12个月,实验组的菌斑指数分别为(1.98±0.13)、(1.95±0.20)、(1.00±0.11),mBI分别为(1.65±0.12)、(1.19±0.13)、(0.92±0.06)均明显低于对照组的(2.65±0.15)、(2.48±0.22)、(1.71±0.15)与(2.06±0.14)、(1.53±0.10)、(1.09±0.05)(P<0.05);治疗后6、9、12个月,实验组的ED发生率分别为14.71%、8.82%、0,均明显低于对照组的41.18%、29.41%、11.76%(P<0.05);实验组治疗后6、9、12个月的EDI分别为(16.35±1.20)、(13.58±1.47)、(9.26±1.02),均明显低于对照组的(20.18±1.62)、(17.50±1.53)、(15.14±1.15)(P<0.05)。结论 对正畸治疗的错颌畸形患者给予司米护齿涂剂安全有效,能够有效预防ED事件,改善牙周指标,值得采纳。

光固化树脂加强型玻璃离子粘结剂应用研究

为分析光固化树脂加强型玻璃离子粘结剂的应用性能,划分3组试验离体牙,制备3组实验样本,依次进行釉质脱矿、抗剪切强度、拉伸力、粘结剂残留程度等测试。结果表明,复合釉质粘结剂样本在脱矿试验时,钙、磷含量迅速流失,易导致牙齿脱矿,且抗剪切能力较弱,拉伸力低,粘结剂残留量略大,当该粘结剂粘接托槽时间较长时容易引发托槽脱落以及微渗透现象等;试验组光固化树脂加强型玻璃离子粘结剂样品可有效防止牙齿样本出现钙、磷流失,抗拉伸强度较大,有较高的抗剪切能力,可有效降低粘结剂残留,并在后续阶段不易发生托槽脱落,可降低牙齿托槽粘接处的白斑率,防止微渗透现象。

Effects of 45S5 bioglass on surface properties of dental enamel subjected to 35% hydrogen peroxide

Tooth bleaching agents may weaken the tooth structure. Therefore, it is important to minimize any risks of tooth hard tissue damage caused by bleaching agents. The aim of this study was to evaluate the effects of applying 45S5 bioglass （BG） before, after, and during 35% hydrogen peroxide （HP） bleaching on whitening efficacy, physicochemical properties and microstructures of bovine enamel. Seventy-two bovine enamel blocks were prepared and randomly divided into six groups： distilled deionized water （DDW）, BG, HP, BG before HP, BG after HP and BG during HP. Colorimetric and microhardness tests were performed before and after the treatment procedure. Representative specimens from each group were selected for morphology investigation after the final tests. A significant color change was observed in group HP, BG before HP, BG after HP and BG during HP. The microhardness loss was in the following order： group HP〉 BG before HP, BG after HP〉 BG during HP〉DDW, BG. The most obvious morphological alteration of was observed on enamel surfaces in group HP, and a slight morphological alteration was also detected in group BG before HP and BG after HP. Our findings suggest that the combination use of BG and HP could not impede the tooth whitening efficacy. Using BG during HP brought better protective effect than pre/post-bleaching use of BG, as it could more effectively reduce the mineral loss as well as retain the surface integrity of enamel. BG may serve as a promising biomimetic adjunct for bleaching therapy to prevent/restore the enamel damage induced by bleaching agents.

Human enamel thickness and ENAM polymorphism

The tooth enamel development gene, enamelin （ENAM）, showed evidence of positive selection during a genome-wide scan of human and primate DNA for signs of adaptive evolution. The current study examined the hypothesis that a single-nucleotide polymorphism （SNP） C14625T （rs7671281） in the ENAM gene identified in the genome-wide scan is associated with a change in enamel phenotype. African Americans were selected as the target population, as they have been reported to have a target SNP frequency of approximately 50%, whereas non-Africans are predicted to have a 96% SNP frequency. Digital radiographs and DNA samples from 244 teeth in 133 subjects were analysed, and enamel thickness was assessed in relation to SNP status, controlling for age, sex, tooth number and crown length. Crown length was found to increase with molar number, and females were found to have thicker enamel. Teeth with larger crowns also had thicker enamel, and older subjects had thinner enamel. Linear regression and generalized estimating equations were used to investigate the relationship between enamel thickness of the mandibular molars and ENAM SNP status; enamel in subjects with the derived allele was significantly thinner （P= 0.040） when the results were controlled for sex, age, tooth number and crown length. The derived allele demonstrated a recessive effect on the phenotype. The data indicate that thinner dental enamel is associated with the derived ENAM genotype. This is the first direct evidence of a dental gene implicated in human adaptive evolution as having a phenotypic effect on an oral structure.

Loss of epithelial FAM20A in mice causes amelogenesis imperfecta, tooth eruption delay and gingival overgrowth

FAM20A has been studied to a very limited extent. Mutations in human FAM20A cause amelogenesis imperfecta, gingival fibromatosis and kidney problems. It would be desirable to systemically analyse the expression of FAM20A in dental tissues and to assess the pathological changes when this molecule is specifically nullified in individual tissues. Recently, we generated mice with a Fam2OA-floxed allele containing the beta-galactosidase reporter gene. We analysed FAM20A expression in dental tissues using X-Gal staining, immunohistochemistry and in situ hybridization, which showed that the ameloblasts in the mouse mandibular first molar began to express FAM20A at 1 day after birth, and the reduced enamel epithelium in erupting molars expressed a significant level of FAM2OA. By breeding K14-Cre mice with Fam20An^x/fl^x mice, we created K14-Cre;Fam20Af/flox/flox （conditional knock out, cKO） mice, in which Fam20A was inactivated in the epithelium. We analysed the dental tissues of cKO mice using X-ray radiography： histology and immunohistochemistry. The molar enamel matrix in cKO mice was much thinner than normal and was often separated from the dentinoenamel junction. The Fam2OA-deficient ameloblasts were non-polarized and disorganized and were detached from the enamel matrix. The enamel abnormality in cKO mice was consistent with the diagnosis of amelogenesis imperfecta. The levels of enamelin and matrix metalloproteinase 20 were lower in the ameloblasts and enamel of cKO mice than the normal mice, The cKO mice had remarkable delays in the eruption of molars and hyperplasia of the gingival epithelium. The findings emphasize the essential roles of FAM20A in the development of dental and oral tissues.

The effect of cold-light-activated bleaching treatment on enamel surfaces in vitro

This in vitrostudy aims to evaluate the crystal and surface microstructure of dental enamel after cold-light bleaching treatment. Twelve sound human premolars were cross-split into four specimens, namely, mesio-buccal （Group LP）, disto-buccal （Group P）, mesio-lingual （Group NP） and disto-lingual （Group L） specimens. These four groups were treated using the standard cold-light bleaching procedure, a bleaching agent, a peroxide-free bleaching agent and cold-light, respectively. Before and after treatment, all specimens were analyzed by high-resolution, micro-area X-ray diffraction and scanning electron microscopy. Using a spectrometer, tooth color of all specimens was measured before and after treatment. The phase of the enamel crystals was identified as hydroxyapatite and carbonated hydroxyapatite. After treatment, specimens in Groups LP and P showed significantly weaker X-ray diffraction peaks, significant reduction in crystal size and crystallinity, significant increase in L~ but decrease in a＊ and b＊, and obvious alterations in the surface morphology. However, specimens in Groups NP and L did not show any significant changes. The cold-light bleaching treatment leads to demineralization in the enamel surface. The acidic peroxide-containing bleaching agent was the major cause of demineralization, whereas cold-light did not exhibit significant increase or decrease effect on this demineralization.

渗透树脂联合生物活性玻璃对早期脱矿牙釉质表面显微硬度及再矿化的影响

目的探究渗透树脂联合生物活性玻璃对早期脱矿牙釉质表面显微硬度及对再矿化的影响。方法选取2021年6月至2022年4月本院收治的80例正畸治疗患者,共取120颗牙齿,随机数字表法分为空白对照组(A组)、渗透树脂组(B组)、渗透树脂联合氟化钠组(C组)及渗透树脂联合生物活性玻璃组(D组),每组30颗。比较处理前、脱矿后、再矿化处理后及再脱矿处理后牙釉质表面粗糙度及牙釉质显微硬度、脱矿24 h、48 h和72 h后钙容量测定及所有区域内荧光量面积(A)、总荧光量(IAF)、平均荧光密度(AF)。结果再矿化和再脱矿处理后组间比较粗糙度值为A组(4.73±0.70μm)>B组(2.87±0.05μm)>C组(1.52±0.09μm)>D组(0.25±0.03μm)](P<0.05);再矿化和再脱矿处理后组间比较牙釉质表面硬度(HV)值为A组(24.74±4.28)<B组(140.15±10.97)<C组(169.44±14.38)<D组(97.68±16.11)(P<0.05);再脱矿24 h、48 h和72 h后的钙溶出总量D组<C组<B组<A组(P<0.05);A组、B组、C组的A和TF显著低于D组(P<0.05),各组间的AF值比较差异无统计学意义(P>0.05)。结论渗透树脂联合生物活性玻璃可提高早期脱矿牙釉质表面显微硬度,且脱矿效果及抗脱矿能力效果良好,具有临床推广应用价值。

儿童第一乳磨牙远中邻面釉质凹陷分布及患龋特点

目的探讨第一乳磨牙远中邻面釉质凹陷的分布特点及患龋情况,为第一乳磨牙邻面龋齿的研究提供参考。方法选取126例至少1颗第一乳磨牙远中邻面存在釉质凹陷的儿童,统计分析其第一乳磨牙远中邻面釉质凹陷的分布情况。结果313颗(62.1%)第一乳磨牙远中邻面存在釉质凹陷,99颗(19.6%)第一乳磨牙远中邻面无法判断凹陷有无,仅有92颗(18.3%)第一乳磨牙远中邻面无凹陷。第一乳磨牙远中邻面釉质凹陷的类型可分为Ⅰ型(57.2%)、Ⅱ型(2.2%)、Ⅲ型(20.4%)、Ⅳ型(1.0%)、Ⅴ型(4.2%)、Ⅵ型(13.1%)和Ⅶ型(1.9%)。第一乳磨牙釉质凹陷类型的牙位分布特点为Ⅰ型占比上颌显著高于下颌,Ⅲ型、Ⅵ型占比下颌显著高于上颌(H_(c)=37.29,P<0.01)。第一乳磨牙远中邻面釉质凹陷的象限分布特点为右下最多,其次为左下、右上、左上,且下颌釉质凹陷牙数显著高于上颌(χ^(2)=14.68,P<0.01)。第一乳磨牙远中邻面国际龋病检查和评估系统(ICDASⅡ系统)龋齿分级的患龋情况无象限差异。结论第一乳磨牙远中邻面釉质凹陷以Ⅰ型最多,其次是Ⅲ型和Ⅵ型;Ⅰ型釉质凹陷主要分布于上颌,Ⅲ型和Ⅵ型釉质凹陷主要分布于下颌。

生物陶瓷仿生矿化牙釉质研究进展

牙齿脱矿及时修复,可避免龋齿的发生,尤其是儿童牙齿矿化不全,更容易导致脱矿而引起龋齿.生物医用活性陶瓷具有较好的生物活性和生物诱导性,可促进组织的矿化.通过钙磷基和钙硅基生物活性陶瓷探讨对牙釉质脱矿后的仿生矿化效果,对比其矿化机制进行阐述.该类生物活性陶瓷具有较好的生物学性能,在口腔及骨修复中发展前景较好,是临床上硬组织修复的首选材料之一.

牙面粘接技术的研究进展

随着人们生活水平的提高,对口腔正畸的需求也逐渐增强。固定矫治器或无托槽隐形矫治是依附于牙齿表面粘接托槽或附件,从而对牙齿及颌骨施加矫治力,而托槽与附件在牙面的粘结极为重要,该文以牙齿表面的粘结技术研究进展做一综述。

儿童第二乳磨牙近中面釉质凹陷临床分析

目的分析第二乳磨牙近中边缘嵴、近中面-舌面非边缘嵴釉质凹陷的分布特点及近中面患龋情况,为第二乳磨牙邻面龋齿防治提供参考。方法选取157名至少1颗第二乳磨牙存在近中边缘嵴釉质凹陷的儿童,分析该组儿童第二乳磨牙近中边缘嵴釉质凹陷、近中面-舌面非边缘嵴釉质凹陷的种类和分布情况及近中面的龋损情况。结果共收集第二乳磨牙628颗。69.4%的第二乳磨牙近中边缘嵴存在釉质凹陷,Ⅲ型主要分布于下颌(χ^(2)=63.01,P<0.05),Ⅳ、Ⅵ、Ⅶ型主要分布于上颌(χ^(2)=15.74~24.03,P<0.05)。52.5%的第二乳磨牙存在近中面-舌面非边缘嵴釉质凹陷,Ⅰ、Ⅲ型主要分布于上颌(χ^(2)=10.23、41.25,P<0.05)。不同牙位釉质凹陷数量差异有统计学意义(H=58.90,P<0.05)。临床检查结果显示,上颌第二乳磨牙早期龋的牙数显著高于下颌(P<0.001)。影像学检查结果显示,上颌第二乳磨牙早期龋牙数显著高于下颌(χ^(2)=75.23,P<0.05);4个牙位的早期龋、中期龋、重度龋的患龋牙数均存在统计学差异(χ^(2)=7.88~28.24,P<0.05)。结论第二乳磨牙近中边缘嵴釉质凹陷的类型、数目和分布,近中面-舌面非边缘嵴釉质凹陷的类型和分布,以及近中面的龋损情况均存在一定的特点。