Ultrastructural changes in the cemento‐enamel junction caused by acidic beverages: An in vitro study

The present in vitro study was aimed at evaluating the morphological changes in the cemento‐enamel junction (CEJ) after exposure to acidic beverages using the scanning electron microscopy (SEM). The initial pH and titratable acidity (TA) was analyzed from follow groups: (I) Coca cola, (II) orange juice, (III) Cedevita, (IV) Red Bull, (V) Somersby cider, and (VI) white wine. The CEJ samples (n = 64), obtained from unerupted third molars, were allocated to one control (artificial saliva, n = 16) and six experimental groups (n = 8). The experimental samples were immersed in beverages (50 ml) for 15 min, three times daily, 10 days, and in artificial saliva between immersions. SEM analysis was performed in a blind manner, according to scoring scale. One‐way ANOVA and Tukey's post hoc tests, as well as Kruskal–Wallis and Mann–Whitney U test used for statistical analysis. The pH values of the acidic beverages ranged from 2.65 (Coca cola) to 3.73 (orange juice), and TA ranged from 1.90 ml (Coca cola) to 5.70 ml (orange juice) of NaOH to reach pH 7.0. The SEM analysis indicated statistically significant differences between the control samples and those immersed in acidic beverages. The Groups IV, I, and II, showed the highest CEJ damage grade while those of the Group VI were the lowest. All the tested acidic beverages caused morphological changes in the CEJ with a smaller or larger exposure of dentine surface, and were not always related to the pH or TA of acidic beverages.     

Metallization and Ar‐O plasma effects on dental enamel roughness evaluated with SEM and MeX™ for 3D reconstruction

The MeX? software is a useful tool for tridimensional data collection for surface evaluation and could be relevant to evaluate the same specimen in different phases of the study, assuming repeated measures of dental enamel roughness. The aim of this study was to evaluate the influence of sample metallization for dental enamel roughness analysis with 3D images reconstructed using MeX? software from Scanning Electron Microscopy (SEM) images. The influence of 74.98% (%mol/mol) argon?oxygen plasma for carbon layer removal on surface roughness of the metallized specimen was also evaluated. Dental enamel specimens were prepared for SEM analysis with and without carbon metallization using conventional or environmental modes. Argon?oxygen plasma for carbon layer removal was used and surface roughness was re‐evaluated. Roughness obtained by SEM and MeX? reconstructed images, with or without metallization, did not differ. No significant alteration on surface roughness after carbon layer removal using plasma was found. SEM baseline evaluation using conventional mode without sample preparation and in environmental mode were not comparable. Roughness of enamel 3D images reconstructed with MeX? software from SEM images, with or without metallization was similar. The 74.98% (%mol/mol) argon?oxygen plasma removed the carbon layer with no effect on enamel roughness.     

低温烧结活性瓷釉涂层钢筋耐腐蚀性能试验研究

为了研究低温烧结活性瓷釉（LTCRE）涂层的性能和机理,利用差示扫描量热法（DSC）和热重法（TG）对LTCRE涂层的烧结温度进行优化,采用扫描电子显微镜（SEM）、X射线能谱分析（EDS）和X射线衍射（XRD）分析涂层微观结构和腐蚀过程,通过中性盐雾试验和氙灯老化试验研究LTCRE涂层钢筋的耐腐蚀性能. LTCRE涂层的优化烧结温度为500~540 °C,涂层具有结构致密、孔隙率低的特点,LTCRE涂层钢筋在腐蚀后的质量变化为普通钢筋的1.6%,800 h盐雾腐蚀后人为缺陷孔的剥离半径为0.26 mm,在氙灯照射下耐老化时长超过500 h. 结果表明,LTCRE涂层作为无机陶瓷涂层,具有比环氧树脂涂层更优异的耐老化性能,具备长期稳定的耐腐蚀能力. 涂层密实少孔的结构和烧结时良好的化学反应使得LTCRE涂层钢筋能够有效阻止外界腐蚀物质渗入与蔓延,即使在缺陷孔发生腐蚀后也能够阻止腐蚀加剧,起到涂层自愈合的效果.     

乾隆御制釉上彩母子图的文化解读

在乾隆御制釉上彩出现为数不少的西洋式母子图题材,这类题材在形式上既有强烈的西洋特点,又融入了部分的中国传统文化因素。本文试图通过对这类釉上彩西洋式母子图题材的分析,来解读其背后所隐涵的东西方文化在18世纪的碰撞与融合,尤其是耶稣会士希望通过合儒来达到传播天主教所做出的努力。     

一次搪耐酸搪瓷界面过渡层结构研究

采用合理配方设计,使用一次涂搪工艺,制备出了同时具有优良密着性能和耐酸性能的搪瓷板。采用扫描电子显微镜和能谱仪对一次搪耐酸搪瓷板界面显微结构和元素进行分析,研究结果表明,密着性能优良的一次搪耐酸搪瓷界面呈现咬合齿轮状,元素分析表明瓷层元素和金属元素相互扩散,相互渗透,在性能上表现为密着强度优良。     

废旧聚酯改性漆包线绝缘漆的性能研究

采用溶胶凝胶法制备Al2O3溶胶,以废旧聚酯塑料瓶和Al2O3溶胶为原料制备聚酯多元醇溶液,然后将聚酯多元醇溶液与氨基树脂、环烷酸锌混合制成聚酯漆包线漆。通过红外光谱和X射线衍射分析对聚酯漆包线漆进行分子结构和物相表征。测试改性聚酯漆包线漆的热冲击、耐电压、介质损耗等性能。结果表明:Al2O3掺杂质量分数为10%时,制得的改性聚酯漆包线漆的性能最佳,介质损耗曲线的拐点温度可达到179℃,耐热性能明显提高。     

Different bacterial models for in vitro induction of non‐cavitated enamel caries‐like lesions: Microhardness and polarized light miscroscopy analyses

The aim of this study was to compare different bacterial models for in vitro induction of non‐cavitated enamel caries‐like lesions by microhardness and polarized light microscopy analyses. One hundred blocks of bovine enamel were randomly divided into four groups (n = 25) according to the bacterial model for caries induction: (A) Streptococcus mutans, (B) S. mutans and Lactobacillus acidophilus, (C) S. mutans and L. casei, and (D) S. mutans, L. acidophilus, and L. casei. Within each group, the blocks were randomly divided into five subgroups according to the duration of the period of caries induction (4–20 days). The enamel blocks were immersed in cariogenic solution containing the microorganisms, which was changed every 48 h. Groups C and D presented lower surface hardness values (SMH) and higher area of hardness loss (ΔS) after the cariogenic challenge than groups A and B (P < 0.05). As regards lesion depth, under polarized light microscopy, group A presented significantly lower values, and groups C and D the highest values. Group B showed a higher value than group A (P < 0.05). Groups A and B exhibited subsurface caries lesions after all treatment durations, while groups C and D presented erosion‐type lesions with surface softening. The model using S. mutans, whether or not it was associated with L. acidophilus, was less aggressive and may be used for the induction of non‐cavitated enamel caries‐like lesions. The optimal period for inducing caries‐like lesions was 8 days. Microsc. Res. Tech. 78:444–451, 2015. © 2015 Wiley Periodicals, Inc.     

Stress and strain distribution in demineralized enamel: A micro‐CT based finite element study

Physiological oral mechanical forces may play a role on the progression of enamel carious lesions to cavitation. Thus, the aim of this study was to describe, by 3D finite element analysis, stress, and strain patterns in sound and carious enamel after a simulated occlusal load. Micro‐CT based models were created and meshed with tetrahedral elements (based on an extracted third molar), namely: a sound (ST) and a carious tooth (CT). For the CT, enamel material properties were assigned according to the micro‐CT gray values. Below the threshold corresponding to the enamel lesion (2.5 g/cm³) lower and isotropic elastic modulus was assigned (E = 18 GPa against E₁ = 80 GPa, E₂ = E₃ = 20 GPa for sound enamel). Both models were imported into a FE solver where boundary conditions were assigned and a pressure load (500 MPa) was applied at the occlusal surface. A linear static analysis was performed, considering anisotropy in sound enamel. ST showed a more efficient transfer of maximum principal stress from enamel to the dentin layer, while for the CT, enamel layer was subjected to higher and concentrated loads. Maximum principal strain distributions were seen at the carious enamel surface, especially at the central fossa, correlating to the enamel cavity seen at the original micro‐CT model. It is possible to conclude that demineralized enamel compromises appropriate stress transfer from enamel to dentin, contributing to the odds of fracture and cavitation. Enamel fracture over a dentin lesion may happen as one of the normal pathways to caries progression and may act as a confounding factor during clinical diagnostic decisions. Microsc. Res. Tech. 78:865–872, 2015. © 2015 Wiley Periodicals, Inc.     

Influence of priming time and primer’s concentrations on bovine enamel bond strengths

This study investigated the effects of priming time (5, 30 or 60?s), 10-MDP (10-methacryloyloxydecyl dihydrogen phosphate)-containing primer’s concentrations (0.5, 1, 5, 10 and 20% (w/w)) and two neutral primers (5% (w/w) of 10-MDP-Na or EDTA-2Na) on bovine enamel microtensile bond strength (μTBS) using a novel prime-and-rinse approach. After priming, the enamel surfaces were thoroughly water-sprayed and dried before resin composite was placed. There was a significant influence of primer’s concentrations and priming time on bovine enamel μTBS when 10-MDP-containing primers were used (p?<?0.001), revealing the optimal priming time (30?s) and the best combination (priming with 20% of 10-MDP for 30?s). The prime-and-rinse approach might be an innovative supplement to contemporary dental adhesive procedures. The neutral primer (5% of 10-MDP-Na) produced moderate enamel μTBS on highly polished enamel surfaces, while another neutral primer (5% of EDTA-2Na) failed, suggesting that chemical bonding of 10-MDP to enamel hydroxyapatite crystallites could yield detectable bond strengths on smooth enamel surfaces.