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Objective: Thermally activated acrylic resins (RAATs) are widely used in dentures as a base material due to their good dimensional stability and biocompatibility. However, their low thermal conductivity is a disadvantage, as it affects acceptance when using dental prostheses. Thus, the objective of this work was to measure the conduction heat in RAATs with and without incorporation of silica and silver nanoparticles (NP) and rigid reline (RR). Material and Methods: For this, samples were made and divided into 10 groups (n = 6). The first five groups were 2-mm-thick samples: G1 (RAAT control), G2 (RAAT + RR control), G3 (RAAT and NP + RR), G4 (RAAT + RR and NP), and G5 (RAAT and RR modified by NP). In the other five groups, 8-mm-thick samples were made: G6 (RAAT control), G7 (RAAT + RR control), G8 (RAAT and NP + RR), G9 (RAAT + RR and NP), and G10 (RAAT and RR modified by NP). The heat that cross the surface of the specimens was quantified using a wireless device. The data were submitted to two-factor ANOVA statistical analysis and Tukey Ìs test with a 5% significance level. Results: After measuring the temperature variation as a function of time, it can be observed that there was a statistically significant difference for thermal conduction between the control groups and those modified with NP. Conclusion: Thus, it was possible to conclude that the NP improved the heat conduction in RAAT and in the RR because the nanoparticles have a higher thermal conductivity. (AU)
Objetivo: As resinas acrílicas termicamente ativadas (RAATs) são amplamente utilizada em próteses dentárias como material de base, pois possuem uma boa estabilidade dimensional e biocompatibilidade. Porém, como desvantagem, possuem baixa condutividade térmica, o que prejudica a aceitação do uso de próteses dentárias. Assim, o objetivo deste trabalho foi medir a condução de calor em RAAT com e sem incorporação de nanopartículas de sílica e prata (NP) e reembasador rígido (RR). Material e Métodos: Para isso, foram confeccionadas amostras que foram divididas em 10 grupos (n=6). Os primeiros cinco grupos eram amostras de 2 mm de espessura: G1 (RAAT controle), G2 (RAAT + RR controle), G3 (RAAT e NP + RR), G4 (RAAT + RR e NP) e G5 (RAAT e RR modificados por NP). E nos outros cinco grupos foram feitas amostras com espessura de 8 mm: G6 (RAAT controle), G7 (RAAT + RR controle), G8 (RAAT e NP + RR), G9 (RAAT + RR e NP) e G10 (RAAT e RR modificados por NP). O calor percorrido pela superfície dos corpos de prova foi quantificado por meio de um dispositivo sem fio. Os dados foram submetidos à análise estatística ANOVA dois fatores e teste de Tukey com 5% de significância. Resultados: Após medir a variação da temperatura em função do tempo, pode-se observar que houve diferença estatisticamente significante para a condução térmica entre os grupos controle e os modificados com NP. Conclusão: Assim, foi possível concluir que a NP melhorou a condução de calor na RAAT e no RR, pois as nanopartículas apresentam maior condutividade térmica. (AU)
Subject(s)
Thermal Conductivity , Acrylic Resins , Nanoparticles , Metal NanoparticlesABSTRACT
Introduction: Commonly used polymethyl methacrylate (PMMA) denture base material cannot be considered as ideal due toinferior thermal and mechanical properties.Aim: The aim of the study was to evaluate and compare the thermal conductivity, flexural strength, and surface hardness ofheat cure acrylic resin incorporated with 10 wt.% and 15 wt.% alumina and conventional denture base resin.Materials and Methods: A total of 108 specimens were prepared. Specimens were divided into three main groups. Group Aspecimens were disk shaped (50 mm × 5 mm) and used for measuring thermal conductivity. Groups B and C specimens wererectangular shaped (65 mm × 10 mm × 3 mm) and were used for measuring flexural strength and surface hardness, respectively.Each group was further divided into three subgroups (1, 2, and 3) depending on the concentration, namely, PMMA without filler(control), PMMA + 10 wt.% of Al2O3, and PMMA + 15 wt.% of Al2O3 containing 12 samples each. Thermal conductivity wasmeasured using a modified guarded hot plate apparatus. Flexural strength was assessed with a three-point bending test usinga universal testing machine. Hardness testing was conducted using a Vickers Hardness Tester. The results were analyzedusing one-way ANOVA followed by post hoc comparison by Tukey’s method.Results: Mean values of thermal conductivity were (in W/mK) 0.190, 0.231, and 0.275 for subgroups A1, A2, and A3, respectively.The mean flexural strength values were (in MPa) 56.62, 66.73, and 74.24 for subgroups B1, B2, and B3, respectively. Meanvalues of surface hardness was calculated to be (in HV) 15.17, 16.51, and 17.91 for subgroup C1, C2, and C3, respectively.There was statistically significant improvement in thermal conductivity, flexural strength, and surface hardness after incorporationof alumina and the increase was in proportion to the weight percentage of alumina filler.Conclusion: Incorporation of alumina into heat cure denture base resin significantly improved the thermal conductivity, flexuralstrength, and surface hardness.
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Objective:To discuss the topical action characteristics of the biological transmission of moxibustion heat via temperature collection and numerical modeling.Methods:Temperature of moxibustion was measured at multiple points at a distance of 3 cm to obtain the moxibustion temperature field nephograms by the high-accuracy temperature measure array.Finite element analysis was used to imitate the three-dimensional dynamic distribution of temperature in acupoint tissues.Results:Through numerical analysis,the one-dimensional,two-dimensional and three-dimensional distributions of temperature in human acupoint tissues at 5 min of moxibustion were established.The result showed that moxibustion heat mainly transmitted from the surface of the tissue to the internal,and the influence of moxibustion heat decreased with the depth of the tissue.The analysis of the nephograms of acupoint tissue temperature at 5,10,15 and 20 min of moxibustion showed that with the increase of the moxibustion time,the temperature in acupoint tissues constantly rose,and the transmission depth of moxibustion heat also further expanded inside acupoint.Conclusion:By establishing the three-dimensional dynamic model of heat transmission inside acupoint tissues with the biological parameters of human tissues and the temperature values obtained,this study used finite element analysis software ANSYS 14.0 and discovered the rules in the transmission of heat in body tissues during moxibustion,and the features in moxibustion heat transmission (from the proximal to the distant) and heat penetration (from the surface to the internal).This study provides theoretical and experimental support for the application of moxibustion in clinical practice.
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Objective:To investigate the effect of thermal conductivity on the apical sealing ability of different dental gutta-percha cones during the warm vertical condensation obturation.Methods:Four kinds of dental gutta-percha cones were used in this study:Bio-GP points (BP,B&L,Korea),large-tapered gutta-percha (DP,DENTSPLY,America),PROTAPER Universal gutta-percha points (DPP,DENTSPLY,America) and mtwo gutta-percha points (VP,VDW,Germany).Volume differences method was used to determine the main components and the thermal conductivity determinator was used to measure the thermal conductivity of these dental gutta-percha cones.Furthermore,20 cones randomly selected from each kind of dental gutta-percha cones.And 10 cones of each dental gutta-percha cones,which were cut out the part of 4 mm in length from the apical end,were heated (200 ℃) from the upper end without compression,and the temperature of the gutta perchacones surface was monitored in time by the infrared thermal imager during the whole heating process.In addition,the rest of the 10 cones of each dental gutta-percha cones were used to obturate the root canal in the transparent root canal resin model using warm vertical condensation technique.The cross-sectional surface was observed by stereomicroscope (× 40) at 1 mm and 3 mm from the working length and the gutta-percha obturation area proportion was measured and analyzed.The data were analyzed by one-way ANOVA.Results:The proportion of inorganic fillers (80.90％ ± 1.14 ％) (P ＜ 0.05) and the thermal conductivity (2.247 ± 0.002)of DP was siguificantly higher than BP (79.28％ ± 3.88％,1.179 ± 0.003),DPP (68.46％ 5.09％,0.604 ±0.001),VP (78.86％ ± 1.87％,1.150 ±0.001) (P ＜0.05).During the thermal obturation without compression at the setting temperature (200 ℃),DP could achieve 65 ℃ beyond 1 mm from the heating point,and BP,DPP and VP only reached 65 ℃ within 1 mm.After warm vertical condensation obturation,all the groups showed increased gutta-percha obturation area proportion.At the position of WL-3,DP (96.89％ ±0.03％) showed significantly higher proportion of gutta-percha obturation area than BP (95.47％ ±0.06％),DPP (95.21％ ±0.03％) and VP (95.15％ ±0.03％) (P ＜ 0.05).Conclusion:DP contains more inorganic fillers,possesses higher thermal conductivity,and leads a better apical sealing ability than BP,DPP and VP at the position of WL-3 during warm vertical condensation obturation.
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Objective To determine the thermal conductivity under different temperatures and concentrations, and specific heat capacity under different concentrations of water extracts of Salvia Miltiorrhiza Radix et Rhizoma; To establish the mathematical model of thermal conductivity-temperature, thermal conductivity-concentration, thermal conductivity-temperature-concentration and specific heat capacity-concentration of water extracts of Salvia Miltiorrhiza Radix et Rhizoma. Methods Thermal conductivity and specific heat capacity were measured by the instantaneous double hot wire thermal conductivity meter and the electrothermal specific heat capacity meter. Excel, 1stOpt and MATLAB were used to analyze the experimental data. Results The method of using brix to facilitate and accurately characterize the concentration was established. The relationship between the thermal conductivity and the temperature and the concentration of water extracts of Salvia Miltiorrhiza Radix et Rhizoma were all linearly negative (λ=a-bT, λ=a-bC), and the influence of temperature and concentration on the thermal conductivity had a certain interaction. λ=a-bC-cT-dCT could be used as the temperature and the concentration on the thermal conductivity of the integrated role model. And the specific heat capacity of the extract was negatively correlated with the concentration (cp=a-bC). Conclusion The thermal conductivity and the specific heat capacity of the extract of water extracts of Salvia Miltiorrhiza Radix et Rhizoma are different at different temperatures and concentrations, and the model can be used to characterize the changing law of thermodynamics of the extracts. It can provide guidance significance for the thermal characteristics analysis in TCM pharmaceutical process and TCM production equipment selection and design, and production process control.
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The pequi fruit (Caryocar coriaceum Wittm) has a great economic interest, regarding the use of its fruits in cooking as a source of vitamins and extraction of oils for the manufacture of cosmetics. However, are unknown studies on the thermophysical properties (specific heat, thermal diffusivity and thermal conductivity), in which properties are very important to the pulp being favored in an industrial level. The work in question was aimed at studying the physical properties of the pequi pulp with levels of total soluble solids of 6, 8, 10 and 12 °Brix. The physical properties were studied: specific heat, thermal diffusivity and thermal conductivity. The specific heat of the pulps was determined using the method of mixtures, the thermal diffusivity was determined using the method proposed by Dickerson and the thermal conductivity KD-2 equipment. Therefore, it was found that the specific heat tended to increase with the increase of temperature and total soluble solids content of the pulp. The thermal diffusivity of the pequi pulp decreased with the increase in total soluble solids; the thermal conductivity of the pulp did not show a definite increase in temperature trend in the pulps investigated.
O fruto do pequi (Caryocar coriaceum Wittm) possui um grande interesse econômico, no que se refere ao uso de seus frutos na culinária como fonte de vitaminas e na extração de óleos para a fabricação de cosméticos. Todavia, são desconhecidos estudos voltados para as propriedades termofísicas (calor específico, difusividade térmica e condutividade térmica), nas quais são propriedades de suma importância para que a polpa seja beneficiada a nível industrial. O trabalho em questão teve como objetivo estudar as propriedades físicas da polpa de pequi com teores de sólidos solúveis totais de 6, 8, 10 e 12 oBrix. As propriedades físicas estudadas foram: calor específico, difusividade térmica e condutividade térmica. O calor específico das polpas foi realizado por meio do calorímetro de mistura, a difusividade térmica utilizando-se o método do cilindro de Dickerson e a condutividade térmica no equipamento KD-2. Portanto, constatou-se que o calor específico apresentou tendência de aumento com o aumento da temperatura e do teor de sólidos solúveis totais das polpas. A difusividade térmica da polpa de pequi diminui com o aumento dos sólidos solúveis totais, a condutividade térmica das polpas não apresentou uma tendência definida com o aumento da temperatura nas polpas estudadas.
Subject(s)
Thermal Conductivity , Magnoliopsida , GrasslandABSTRACT
The aim of this study is to determine some physical and mechanical properties of Paulownia tomentosa wood grown in Turkey. The samples trees harvested from Kargi in Corum. Physical properties including air-dry density, oven-dry density, basic density, swelling, shrinkage and oven-dry and air-dry thermal conductivity coefficients; mechanical properties including bending strength, modulus of elasticity in bending, compression strength parallel to grain, hardness, bonding strength were analyzed. Paulownia tomentosa wood’s air dry and oven dry densities were determined as 0.317 and 0.294 g cm-3; basic density was determined as 0.272 g cm-3; volumetric shrinkage and swelling were determined as 7.78 and 8.41%; tangential, radial and longitudinal air-dry thermal conductivity coefficients were determined as 0.089, 0.090 and 0.133 kcal/mhoC, respectively. Fiber saturation point (FSP) was found 28.79%; bending strength, Modulus of elasticity in bending, compression strength parallel to grain and Brinell hardness values (parallel and perpendicular to grain) were determined as 43.56 N mm-2, 4281.32 N mm-2, 25.55 N mm-2, 2.01 kgf mm-2 and 0.88 kgf mm-2, respectively. Consequently, paulownia wood can be widely used for various purposes such as house construction, furniture making, pulp and paper and handicrafts.