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This study aimed at evaluating the mineral variation induced by polyalkenoate cements in residual dentine after different caries removal methods. Ten extracted sound molars were selected, and five cavities were prepared on the occlusal surface of each specimen. Carious lesions were generated using a microbial protocol, while the caries removal was performed using bur, hand excavator, or two papain-based chemo-mechanical agents. One cavity was left unexcavated in each tooth. Cavities were restored using a zinc polycarboxylate cement (ZPC; n = 25), or a glass ionomer cement (GIC) was used (n = 25). Subsequently, the specimens were stored under simulated pulpal pressure for 45 days. Micro-CT scanning was performed after caries formation, removal, and restoration. Cavity volumes (mm3) and mineral density (MD) changes were calculated. Remineralisation ability was investigated by scanning electron microscopy (SEM) and Fourier-transformed infrared spectroscopy (FTIR). Statistical analysis was performed (5% significance level). Baseline caries, cavity volume, and MD increase after caries removal were similar to all excavation groups (p > 0.05). MD was higher in ZPC compared to GIC (p < 0.05). SEM revealed that the chemo-mechanical techniques produced a smoother dentine surface compared to mechanical methods. FTIR showed silicon-based minerals in GIC-treated dentine, while ZPC-treated presented mineral deposits characterised by amorphous calcium phosphate. In both cases, the presence of carbonates was detected on dentine surfaces. All caries removal techniques performed similarly in terms of carious dentine excavation. ZPC can be used as dentine replacement material after caries removal as it may induce higher MD increase in residual dentine via deposition of calcium phosphates, compared to GIC.

This study aimed to evaluate the in vitro effect of a single application of experimental nanocomposite solutions on the prevention of dental caries around orthodontic brackets. The specimens were exposed to mesoporous silica (MS) nanocomposites containing fluoride by association with titanium tetrafluoride (TiF4) or sodium fluoride (NaF). Nanocomposites also could contain calcium and groups were described as MSCaTiF4, MSTiF4, MSCaNaF, MSNaF, and controls (TiF4, and NaF). Specimens were subjected to the formation of a multispecies biofilm to generate a cariogenic challenge. After 24h, both pH and total soluble fluoride concentration of the culture medium were assessed. Mineral loss was evaluated by percentage of surface mineral loss (%SML), mineral volume variation (ΔZ) of inner enamel and polarized light microscopy (PL). Linear (Ra) and volumetric (Sa) surface roughness and scanning electronic microscopy (SEM) were used to assess enamel topography. Statistical analyses were conducted considering p

Metallic archeological artifacts have specific characteristics that differs them to the other classes of materials due to the transformations that occurs to them, mainly electrochemical. This way, a process called corrosion takes place, starting at the surface of the artifacts, changing the metals in oxides, sulphates, carbonates or other compounds that may result in substantial modifications in their morphology or the total mineralization. Possibly, most part of the archeological artifacts was already suffering this natural deterioration process, even before the period of time that they have remained buried. A number of techniques can be used for the analysis of these artifacts; however, most of them require physical sectioning, which is a complex time-consuming process. This work proposes the use of X-ray microtomography (microCT), which is a non-invasive and expeditious analysis technique, in order to identify the structures and texture of metallic archeological artifacts under incrustations. A set of artifacts found in excavations in the city of Rio de Janeiro (Brazil) were investigated. They show evident forms of degradation, and the incrustations did not allow to clearly identifying them. Through the microCT results is was possible to evaluate the structure of the artifacts, as well as to quantify the material loss caused by corrosion. Such results provided significant data about these historic pieces, which is important for a precise diagnostic about their conservation state, being a useful tool for preserving the morphology of the collected artifact.

Objectives This study aimed to compare and evaluate the porosity and pore size distribution of high-viscosity glass ionomer cements (HVGICs) and conventional glass ionomer cements (GICs) using micro-computed tomography (micro-CT). Materials and Methods Forty cylindrical specimens (n = 10) were produced in standardized molds using HVGICs and conventional GICs (Ketac Molar Easymix, Vitro Molar, MaxxionR, and Riva Self-Cure). The specimens were prepared according to ISO 9917-1 standards, scanned in a high-energy micro-CT device, and reconstructed using specific parameters. After reconstruction, segmentation procedures, and image analysis, total porosity and pore size distribution were obtained for specimens in each group. After checking the normality of the data distribution, the Kruskal-Wallis test followed by the Student-Newman-Keuls test was used to detect differences in porosity among the experimental groups with a 5% significance level. Results Ketac Molar Easymix showed statistically significantly lower total porosity (0.15%) than MaxxionR (0.62%), Riva (0.42%), and Vitro Molar (0.57%). The pore size in all experimental cements was within the small-size range (< 0.01 mm3), but Vitro Molar showed statistically significantly more pores/defects with a larger size (> 0.01 mm3). Conclusions Major differences in porosity and pore size were identified among the evaluated GICs. Among these, the Ketac Molar Easymix HVGIC showed the lowest porosity and void size.

This study aimed to evaluate the endodontic instrumentation outcomes with asymmetrical files compared to reciprocating and hand files (HFs) in 3D-printed prototypes of upper primary incisors using micro-computed tomography (micro-CT). For this purpose, 50 prototypes were randomly divided (n = 10) according to the instrumentation technique as follows: HFs, a reciprocating file (WaveOne® Gold [WOG]), and three asymmetrical movement files: XP-Endo® Shaper (XPS), XP-Endo® Finisher (XPF), and XP Clean (XPC). The specimens were scanned and, after registration of the baseline and instrumented volumes, changes in the root canal volume (RCV), debris accumulation, removed root material volume (RRMV), non-instrumented areas, and the presence of cracks/perforations were quantified. Data were analyzed by analysis of variance and Student’s t-test, while the effect size was calculated for statistically significant outcomes. All groups showed an increase in RCV after instrumentation (p < 0.05), but this was higher with HFs (p < 0.05). Accumulated debris was higher for WOG and XPS (p < 0.05), but WOG exhibited more in the medium and apical third areas. HFs showed the highest RRMV (p < 0.05), especially at the apical third. The non-instrumented areas were lower for HFs and XPC than for the other systems (p < 0.05). Cracks were present in a few WOG (n = 2) and HF specimens (n = 3) and in this group, one of the cracked specimens and two others showed perforations. The asymmetric systems resulted in conservative dentin removal and fewer cracks/perforations as compared to HFs and a reciprocation file in prototyped primary upper incisors. XPC showed the best compromise between RRMV and non-instrumented areas with a low accumulation of debris.

Orientador: Prof. Dr. Roberto Dalledone Machado Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Métodos Numéricos em Engenharia. Defesa : Curitiba, 20/02/2020 Inclui referências: p.169-174 Área de concentração: Mecânica dos Sólidos Computacional Resumo: O dimensionamento de estruturas de concreto armado visa definir a quantidade e a distribuição de armaduras necessárias nas peças. Em regiões que apresentam perturbações no campo de tensões (conhecidas na literatura como "Regiões D"), o Método das Bielas é empregado para o dimensionamento das peças. Uma das dificuldades na aplicação do método é a determinação prévia do campo de tensões, pois este depende da própria geometria da peça e do detalhamento das armaduras. Por esse motivo, preliminarmente, análises elásticas geralmente são empregadas para sugerir uma provável distribuição de tensões que pode definir o modelo de escoras e tirantes. Entretanto, considerando o Estado Limite Último (ELU), a distribuição de tensões pode ser afetada por efeitos não-lineares decorrentes das relações constitutivas dos materiais (concreto e aço), do processo de danificação que a peça venha a sofrer e da distribuição de armaduras. O presente trabalho tem como objetivo apresentar análises computacionais não-lineares em diversas peças de concreto armado, considerando a distribuição de armaduras, a fim de avaliar o seu real comportamento no ELU, e comparar com os resultados estimados pelos métodos usuais de dimensionamento, notadamente o Método das Bielas. Para tanto, são desenvolvidos modelos computacionais de concreto armado através do software de elementos finitos ABAQUS, considerando a Mecânica do Dano Plástico. Os modelos aqui elaborados reproduzem detalhadamente as armaduras utilizadas, inclusive, as construtivas, procurando avaliar a influência da distribuição de armaduras no campo de tensões da peça e na sua capacidade resistente. Diversas situações são examinadas e os resultados são comparados com os processos convencionais de cálculo ou com o Método das Bielas. Os exemplos desenvolvidos confirmam que a distribuição de tensões e a capacidade resistente são afetadas pela distribuição de armaduras adotada. Dessa forma, pretendese avaliar como ocorre a evolução das tensões no interior dos elementos e como as armaduras influenciam em sua topologia e resistência final. Palavras-chave: 1. Escora e Tirantes 2. Método dos Elementos Finitos 3. Método das Bielas 4. Concreto Armado 5. Análise Não-Linear Abstract: The design phase of reinforced concrete structures aims to define the amount and distribution of steel rebars (reinforcement) required in the elements to support the project loads. In regions where the stress field is complex ("D Regions"), the Strut and Tie Method is used to design the concrete elements. One of the difficulties in the application of the method is the determination of stress field that the element will possess, since it depends on the element geometry and the amount of reinforcement used. For this reason, on an initial step, elastic analyzes can be used to suggest a probable field of stresses to be used in the definition of the Strut and Tie Model. However, in the ultimate strength, the stress distribution can be affected by non-linear effects like non regular constitutive relations of the materials (concrete and steel), by damage processes that the part will suffer and by the distribution of reinforcements. The objective of this work is to present nonlinear computational analysis of several elements of reinforced concrete, considering the distribution of reinforcement, in order to evaluate its real behavior in the ultimate state, and to compare with the results predicted by the usual methods of design, mainly the Strut and Tie method. In order to reach this objective, the models of reinforced concrete are developed through the software of finite elements ABAQUS, considering Concrete Damage Plasticity. The models constructed on this paper consider the reinforcement distribution, including the constructive ones, trying to evaluate its influence in the field of tensions and its resistant capacity. Several situations are examined, and the results are compared with the conventional design methods or with the Strut and Tie Model. The developed examples confirm that the stress field and the resistance capacity are affected by the reinforcement distribution. In this way, the present work intends to discuss how the Strut and Tie models are affected by non-linear behavior and by the designed enforcements. Keywords: 1. Strut and Tie 2. Finite Element Method 3. Truss Models 4. Reinforced Concrete 5. Non-Linear Analysis

BACKGROUND Achieving a void-free root canal filling is a challenge in current clinical pulpectomy practice. AIM To compare filling effectiveness and internal voids of root filling materials and obturation techniques in resin-prototyped primary incisors by micro-CT. DESIGN Fifty prototypes were instrumented and randomly divided (n = 10) according to the filling materials (Vitapex® , ZOE, Calcicur® , Feapex, and Calen® -ZO) and obturation technique: lentulo or pressure syringe (n = 5). The specimens were micro-CT scanned (pixel size = 7.83 μm) and reconstructed, and the total volume of filled canal (%FC) and internal voids (%IV) of the bulk filling material was calculated. Kruskal-Wallis and Mann-Whitney tests were used to detect differences and interactions among groups. RESULTS Calen® -ZO, Vitapex® , and ZOE showed similar %FC. Calcicur® showed lower %FC compared with Calen® -ZO, Vitapex® , and ZOE (P

Objective: This study aimed to evaluate the efficacy of passive ultrasonic irrigation (PUI) and the easy clean instrument by micro-computed tomography (CT) for removing remnant filling materials during endodontic retreatment. Materials and Methods: Forty mesial roots of mandibular molars were divided into four groups (n = 10) according to the agitation system and sealer used: Group 1: PUI/AH Plus; Group 2: PUI/TotalFill; Group 3: Easy Clean/AH Plus; and Group 4: Easy Clean/TotalFill. The groups were compared by micro-CT analysis according to the volumes of the obturation and the remaining material before and after the agitation systems were used. Results: There was no difference between the groups for total filling volume and initial and final remaining filling volume (P > 0.05). Conclusions: Both the PUI and easy-clean instrument are effective for removing remnants of filling material with no difference between the groups.

The formation of scales consists in one of the most relevant problems in the oil prospecting field and occurs when incompatible types of water (injected sea water and formation water) are mixed in the reservoir, unavoidably undergoing chemical interaction followed by mineral precipitation. In this work, scale samples extracted from obstructed oil pipes were characterized through X-Ray Microfluorescence and X-Ray microtomography by analyzing their elemental and structural composition. Different types of scale were found according to their elemental distribution (mainly BaSO4 and CaCO3) and to the way that they were deposited inside the pipes. The results of both techniques provided data that can be used to optimize the prevention and removal methods of such materials from pipes and equipments used in oil facilities.

Although X-ray Microcomputed Tomography (microCT) has been used to analyze the marginal fit of dental crowns, the methodology used is simple and subjective, since the quality parameters are uni-dimensional and measured in different views chosen by the operator. This methodology uses as quality parameter the range of thickness in specific regions. The microCT is a non-destructive testing technique that makes possible to perform quantitative and qualitative analysis, and in this study, the technique was used to evaluate de gap volume and to presented the gap thickness distribution along the dental crown. The aim of this study is to develop a new methodology to obtain quality parameters based on gap's volume, which is a tridimensional parameter, to analyze the marginal fit of dental crowns through microCT technique. The samples used in this study was validated by the usual methodology and thus this new methodology allowed defining a gap volume range considered acceptable to assess the manufacturing and materials quality taking into account the thickness range used on the bi-dimensional methodology.

A thermodynamic description of the Mg–Al – Sr ternary in the Mg– Al-rich region was developed based on the microstructures, the crystal structures and compositions of the phases in three samples in the as-cast and 673 K annealed states. The gross compositions of the three alloys were identified for investigation based on a calculated isotherm using the description obtained from those of the constituent binaries via extrapolation. The calculated liquidus projection using the developed description was found to be consistent with the primary phases of solidification obtained from two additional alloys in the as-cast state. In addition, the model-calculated isotherm and liquidus projection are able to rationalize results reported in a recent publication for this ternary. This paper demonstrates the power of using a preliminary calculated phase diagram for selecting key alloys for experimentation, on basis of which a reliable thermodynamic description can be developed.

Solidification behavior and as-cast microstructure have been analyzed in a series of ternary Mg alloys consisting of Mg — Al — X: (Ca, Sr, Ce, La). Thermodynamic calculations of the Mg — Al — Ca, Mg — Al -Sr, and Mg — Al — Ce ternaries were conducted to predict the solidification path of the Mg — 4 Al — 4 X and Mg — 4 Al — 2 X systems. Thermal analyses of the solidification process and accompanying electron microscopy studies of as-cast microstructure were conducted on the same alloys. Scheil calculations and the experimental measurements of liquidus and solidus temperatures are compared. All microstructures consisted of primary α-Mg grains with intermetallic phases along the grain boundaries. Additions of Ca and Sr widen the solidus to liquidus gap to a much greater degree than equivalent levels of Ce and La.

The microstructure and microstructural stability of die-cast AC53 (Mg-5Al-3Ca) and AXJ530 (Mg-5Al-3Ca-0.15Sr) have been investigated in detail by transmission electron microscopy (TEM). Both alloys have an as-cast microstructure of α-Mg with (Mg, Al)2Ca (dihexagonal C36) eutectic at grain boundaries. During aging at 573 K, the C36 phase transforms to Al2Ca (cubic Cl5) phase. These two phases have a crystallographic orientation relationship of (0001)C36//{111}C15 and [2110]C36//[011]C15, and the transformation from C36 to C15 occurs by a shear-assisted process. Despite this change in the phase constitution, the network structure of the intermetallic compound(s) surrounding α-Mg grains is fairly stable, morphologically, even after prolonged exposure at elevated temperature. In the α-Mg matrix phase, precipitation of Al2Ca was observed after aging for 360 ks at 573 K. The precipitates are disc-shaped with a habit plane of {111}C15//(0001)α. AXJ530 shows higher creep resistance than AC53. The dislocation substructure that evolved during creep deformation was investigated in both alloys, and the basal and non-basal slip of a-dislocation and other slip modes of a+c- dislocations were observed. The relationship between creep properties and microstructure is discussed.