A novel sol-gel Bi2-xHfxO3+x/2 radiopacifier for mineral trioxide aggregates (MTA) as dental filling materials

Funding Information: The authors would like to thank Taipei Medical University Hospital for financially sup-porting this work under grant no. 110TMU-TMUH-16 and partially supported by MOST 109-2221-E-038-014. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Mineral trioxide aggregate (MTA) is well known as an effective root canal filling material for endodontics therapy. Within MTA, bismuth oxide (Bi2O3) serving as the radiopacifier still has biocompatibility concerns due to its mild cytotoxicity. In the present study, we tried to modify the Bi2O3 radiopacifier by doping hafnium ions via the sol-gel process and investigated the effects of different doping ratios (Bi2-xHfxO3+x/2, x = 0–0.3) and calcination temperatures (400–800 °C). We mixed various precursor mixtures of bismuth nitrate (Bi(NO3)3·5H2O) and hafnium sulfate (Hf(SO4)2) and controlled the calcination temperatures. The as-prepared Hf-doped Bi2O3 radiopaci-fier powders were investigated by thermogravimetric analysis (TGA), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Portland cement/radiopacifier/calcium sulfate (75/20/5) were mixed and set by deionized water (powder to water ratio = 3:1). Changes in radiopacity, diametral tensile strength (DTS), and in vitro cell viability of the hydrated MTA-like cement were carried out. The experimental results showed that the group containing radiopacifier from sol-gelled Bi/Hf (90/10) exhibited significantly higher radiopacity (6.36 ± 0.34 mmAl), DTS (2.54 ± 0.29 MPa), and cell viability (84.0±8.1%) (p < 0.05) when compared to that of Bi/Hf (100/0) powders. It is suggested that the formation of β-Bi7.78Hf0.22O12.11 phase with hafnium addition and calcining at 700 °C can prepare novel bismuth/haf-nium composite powder that can be used as an alternative radiopacifier for root canal filling mate-rials.publishersversionPeer reviewe

Recent Advances in Conjugated Polymers for Light Emitting Devices

A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review

Vertical consolidation of double-layered clay under liner time-dependent loading

本研究主要在探討兩種不同塑性指數組合黏土層在不同線性荷重速率下單向度垂直壓密沉陷之行為。在研究過程中考慮上下不同黏土層隨荷重改變之壓密係數及滲透係數，以有限差分法分析並推求在此不同線性荷重速率下雙層黏土層之壓密沉陷量並和試驗值相比較。 本研究採用三種不同塑性指數之黏土，首先對此三種不同土樣分別進行傳統的單向度垂直壓密試驗，求取在各荷重下垂直單向度之壓密試驗與變形量的關係，並在此一系列試驗過程中計算體積壓縮係數mv值，接著在各荷重壓密試驗完成後進行變水頭滲透試驗量測各荷重下之滲透係數kv值，根據(公式略)之計算進而求得各級荷重下壓密係數Cv值，並以此作為有限差分法分析孔隙水壓之用，以預估在不同線性荷重速率下雙層黏土層壓密試驗之理論沉陷量值。在有限差分法分析孔隙水壓隨荷重時間改變下之過程中，雙層黏土層在介面間的孔隙水壓，是根據體積的改變是由於流速率的差異假設下求得其關係式，在上下兩土層則是以相同空隔間距△z予以分析。 另外則以MTS材料試驗機對不同塑性指數所組合雙層黏土層進行各種不同線性荷重速率之壓密，直接量取其壓密沉陷量與時間之關係圖並與有限差分法所預測之壓密沉陷實驗值相比較。 經分析後發現空隔間距 劃分的愈小，其所預估的沉陷量和時間之關係與量測值愈接近。至於以荷重16kgf/cm2固定滲透係數kv和壓密係數Cv所分析沉陷量與荷重時間之關係；與以滲透係數kv和壓密係數Cv隨荷重改變所分析之結果相比較，可以發現固定滲透係數kv和壓密係數Cv分析所得理論沉陷量與實驗值間差異較為大，所以實驗在線性荷重速率下雙層黏土之垂直壓密沉陷量理論分析需考慮滲透係數kv和壓密係數Cv隨荷重而改變。摘要 I 目錄 III 表目錄 V 圖目錄 VIII 照片目錄 X 第一章 緒論 1 1.1 研究背景 1 1.2 研究目的與方法 3 第二章 文獻回顧 5 2.1 單向度垂直壓密行為 5 2.1.1 壓密係數Cv對沉陷量預估的重要性 6 2.1.2 荷重應力與Cv值變化之關係 7 2.1.3 壓密係數之求取 10 2.2 雙層黏土壓密孔隙水壓之求法 11 2.3 有限差分法在壓密問題之應用 15 第三章 試驗設備及程序 18 3.1 試驗項目 18 3.2 試驗設備 19 3.2.1 一般物理性質試驗設備 19 3.2.2 壓密試體的製作設備 19 3.2.3 改良之垂直壓密儀 20 3.2.4 材料試驗機MTS設備及資料擷取系統 20 3.3 試驗流程 21 3.4 試驗程序 22 3.4.1 材料的選定 22 3.4.2 一般物理性質試驗 23 3.4.3 試體的製作方法 23 3.4.4 垂直壓密試驗與變水頭滲透試驗 25 3.4.5 不同線性荷重速率下雙層黏土垂直壓密試驗 26 第四章 試驗結果與分析 36 4.1 一般物理性質試驗結果 36 4.2 垂直壓密實驗之結果 37 4.2.1 滲透係數kv值之量測 38 4.2.2 壓密係數Cv值與垂直有效壓力p&acute;間之關係 39 4.3 有限差分法(finitedifferencemethod)預測沉陷量 40 4.4 壓密沉陷量測值與有限差分法預測值之比較 42 第五章 結論與建議 119 5.1 結論 120 5.2 建議 121 參考文獻 12

Evaluation of the root and canal systems of maxillary molars in Taiwanese patients: A cone beam computed tomography study

Background: This study evaluated variations in root canal configuration in the maxillary permanent molars of Taiwanese patients by analyzing patients' cone beam computed tomography (CBCT) images. Comparisons were made among these configurations and those previously reported. This information may serve as a basis for improving the success rate of endodontic treatment. Methods: The root canal systems of 114 Taiwanese patients with bilateral maxillary first or second molars were examined using CBCT images. The number of roots, canals per root, and additional mesiobuccal (MB) canals, as well as the canal configuration were enumerated and recorded. Results: Of the 196 maxillary first molars examined, three (1.5%) had a single root, two (1.0%) had two roots, and 191 (97.5%) had three separate roots. Out of all first molar roots examined, 44% of mesiobuccal (MB) roots had a single canal and the remainder had a second MB (MB2) canal. Of the 212 maxillary second molars examined, 16 (7.1%) had a single root, 51 (24.2%) had two roots, 143 (67.8%) had three roots, and two (0.9%) had four separate roots. For the MB roots, 92.3% of three-rooted maxillary second molars had a single canal and the remainder had an MB2 canal. In all three-rooted maxillary first and second molars, each of the distal and palatal roots had one canal. Conclusions: The root canal configurations of the MB roots of maxillary molars were more varied than those of the distobuccal and palatal roots, and the root canal configurations of maxillary second molars were more varied than those of the first molars. These findings demonstrate CBCT as a useful clinical tool for endodontic diagnosis and treatment planning

Fabrication of device with poly(N-isopropylacrylamide)-b-ssDNA copolymer brush for resistivity study

Abstract In this study, we grafted bromo-terminated poly(N-isopropylacrylamide) (PNIPAAm) brushes onto thin gold films deposited on silicon, and then reacted with NaN3 to produce azido-terminated PNIPAAm brushes. A probe sequence of single-stranded DNA (ssDNA) with a 4-pentynoic acid succinimidyl ester unit was grafted onto the azido-terminated PNIPAAm brushes through a click reaction, resulting in the formation of block copolymer brushes. The PNIPAAm-b-ssDNA copolymer brushes formed supramolecular complexes stabilized by bio-multiple hydrogen bonds (BMHBs), which enhanced the proton transfer and thereby decreased the resistivity of the structures. In addition, the optimal operation window for DNA detection ranges from 0 to 0.2 M of NaCl concentration. Therefore, the specimens were prepared in the PBS solution at 150 mM NaCl concentration for target hybridization. The supramolecular complex state of the PNIPAAm-b-ssDNA copolymer brushes transformed into the phase-separated state after the hybridization with 0.5 ng/µL of its target DNA sequence owing to the competition between BMHBs and complementary hydrogen bonds. This phase transformation of the PNIPAAm and probe segments inhibited the proton transfer and significantly increased the resistivity at 25 °C. Moreover, there were no significant changes in the resistivity of the copolymer brushes after hybridization with the target sequence at 45 °C. These results indicated that the phase-separated state of the PNIPAAm-b-ssDNA copolymer brushes, which was generally occurred above the LCST, can be substantially generated after hybridization with its target DNA sequence. By performing the controlled experiments, in the same manner, using another sequence with lengths similar to that of the target sequence without complementarity. In addition, the sequences featuring various degrees of complementarity were exploited to verify the phase separation behavior inside the PNIPAAm-b-ssDNA copolymer thin film

Thermoelectric Properties of Alumina-Doped Bi0.4Sb1.6Te3 Nanocomposites Prepared through Mechanical Alloying and Vacuum Hot Pressing

In this study, γ-Al2O3 particles were dispersed in p-type Bi0.4Sb1.6Te3 through mechanical alloying to form γ-Al2O3/Bi0.4Sb1.6Te3 composite powders. The composite powders were consolidated using vacuum hot pressing to produce nano- and microstructured composites. Thermoelectric (TE) measurements indicated that adding an optimal amount of γ-Al2O3 nanoparticles improves the TE performance of the fabricated composites. High TE performances with figure of merit (ZT) values as high as 1.22 and 1.21 were achieved at 373 and 398 K for samples containing 1 and 3 wt % γ-Al2O3 nanoparticles, respectively. These ZT values are higher than those of monolithic Bi0.4Sb1.6Te3 samples. The ZT values of the fabricated samples at 298–423 K are 1.0–1.22; these ZT characteristics make γ-Al2O3/Bi0.4Sb1.6Te3 composites suitable for power generation applications because no other material with a similarly high ZT value has been reported at this temperature range. The achieved high ZT value may be attributable to the unique nano- and microstructures in which γ-Al2O3 nanoparticles are dispersed among the grain boundary or in the matrix grain, as revealed by high-resolution transmission electron microscopy. The dispersed γ-Al2O3 nanoparticles thus increase phonon scattering sites and reduce thermal conductivity. The results indicated that the nano- and microstructured γ-Al2O3/Bi0.4Sb1.6Te3 alloy can serve as a high-performance material for application in TE devices

Influence of Deformation and Stress between Bone and Implant from Various Bite Forces by Numerical Simulation Analysis

Endosseous oral implant is applied for orthodontic anchorage in subjects with multiple tooth agenesis. Its effectiveness under orthodontic loading has been demonstrated clinically and experimentally. This study investigates the deformation and stress on the bone and implant for different bite forces by three-dimensional (3D) finite element (FE) methods. A numerical simulation of deformation and stress distributions around implants was used to estimate the survival life for implants. The model was applied to determine the pattern and distribution of deformations and stresses within the endosseous implant and on supporting tissues when the endosseous implant is used for orthodontic anchorage. A threaded implant was placed in an edentulous segment of a human mandible with cortical and cancellous bone. Analytical results demonstrate that maximum stresses were always located around the implant neck in marginal bone. The results also reveal that the stress for oblique force has the maximum value followed by the horizontal force; the vertical force causes the stress to have the minimum value between implant and bone. Thus, this area should be preserved clinically to maintain the structure and function of a bone implant

MOESM1 of Fabrication of device with poly(N-isopropylacrylamide)-b-ssDNA copolymer brush for resistivity study

Additional file 1: Figure S1. Thickness of (a) PN4, PN8, PN12, PN16 and PN20, and (b) PN4D, PN8D, PN12D, PN16D and PN20D plotted as a function of temperature