Plaster Blocks Research Articles

Thermal Behaviour of Hydrofugated Plaster Block Masonry with Variation of Coating Thickness

The objective of this research is to analyze the influence of ceramic coating, simulating the external side, and plaster with different thicknesses, simulating the internal side of a prototype of solid water-repellent gypsum block masonry, aiming to improve the thermal performance mainly in the settlement joints of the block. For this purpose, two specific test methods were used: thermal camera and infrared thermography. The temperature differences between the internal and external faces were analyzed by means of thermocouples connected in the middle of the prototype and the mapping of the temperature profile on the surface of the cladding. It was found that the addition of gypsum sheathing plus ceramic improves the thermal performance of the masonry system, observing that the variation of the thickness of the gypsum mortar provides a gain in thermal resistance, a reduction in thermal transmittance and an increase in thermal capacity.

Effects of self-etch adhesive agitation with diode laser on dentin bond strength.

The present study assessed the effect of active application of self-etch adhesives with diode laser irradiation on the shear dentin bond strength. Sixty bovine incisors, each embedded individually in hard plaster blocks, were divided into two groups based on the adhesive system used: Group 1 Adper Easy One and Group 2 Clearfil SE Protect. Based on the application technique of self-etch adhesives, each main group was further divided into three subgroups: passive application, active application with a micro-brush, and active application with a 976-nm diode laser tip (phototherapy active application). Shear bond strength tests were conducted using a universal testing machine and the data were analyzed by two-way ANOVA. Post hoc multiple comparisons were performed with the Tukey HSD test. Additionally, the statistical analysis of failure mode distribution was carried out using the chi-squared test (p < 0.05). While the adhesive system exhibited significant differences in shear dentin bond strengths, there were no significant differences in application techniques. Regardless of the application technique, Clearfil SE Protect demonstrated significantly higher dentin bond strength than Adper Easy One. In the present study, the utilization of phototherapy through a 976-nm diode laser for the active application of the tested self-etch adhesives demonstrated similar initial dentin bond strengths to conventional application methods.

Determination of dielectric properties of plaster blocks for sealing masonry using non-destructive frequency scanning methods

With the increasing use of traditional and new models of wireless communication systems, the study and determination of the electrical characteristics of materials used in civil construction is an important topic to establish an understanding of how the radio frequency signal behaves inside built environments. This study presents an extensive process of characterization of electrical parameters of plaster blocks used in the construction of walls. Different from the literature where a prior estimation of the data occurs to enable sampling parameters to be obtained, this work proposes an innovative way of obtaining them entirely based on the analysis of the material through frequency measurements, which results in a greater level of precision of the data results. Analyses are made in the frequency range from 0.7 to 5.2 GHz, which has been used for several wireless communication standards. To carry out the electrical characterization of dielectric materials, a non-invasive methodology is proposed based on an innovative combination of the Nicolson–Ross–Weir Method (NRW) and the Ray Tracing Method. Through the proposed methodology and an extensive campaign of measurements using frequency scanning equipment, calculated and experimental data of Shielding Effectiveness (SE), complex relative electrical permittivity, loss tangent, attenuation coefficient and conductivity were obtained for a wide range of frequency, considering different samples of plaster blocks. The obtained results are compared to those available in the related literature, confirming the accuracy of the proposed analysis.

Parameters of thermal performance of plaster blocks: Experimental analysis

This work aims to obtain parameters of thermal performance of various types of plaster blocks for vertical sealing. The methodology consisted of making test elements with 8 types of plaster blocks, in addition to plasterboard of different densities. Thermal resistance, transmittance, capacity, and delay were calculated, according to the Brazilian standard NBR 15220. Thermal behavior tests were carried out with controlled heating through a heat source, digital thermometer, infrared thermography, and an instrumented thermal chamber developed for this work. The experimental results corroborated with the trend indicated by the calculated parameters. The massive and hollow blocks of 100 mm had the best results followed by the 76 mm hollow blocks. The 50- and 70-mm massive blocks were among those with the worst thermal behavior. The study through the thermal chamber and real test elements associated with the normative methods allowed the practical verification regarding the thermal behavior of the components.

A comparative study on microleakage of two low shrinkage composite materials in Class II cavities: A stereomicroscopic analysis.

To compare the microleakage of Filtek bulk fill posterior and Beautifil II LS composites in Class II cavities using stereomicroscope. A total of 34 extracted teeth were randomly divided into two groups. Teeth were prepared and mounted on a plaster block. In each tooth, Class II cavities were prepared, following which the cavities were etched and bonded. In Group I, 17 teeth were restored with Filtek bulk fill posterior composite in bulk fill technique and in Group II, 17 teeth were restored with Beautifil II LS following manufacture's instructions. The samples were then thermocycled and then the tooth were immersed in 1% methylene blue for 24 h and were divided into two halves mesiodistally using a diamond disc at low speed. Then, all the sections were observed under a stereomicroscope at ×10 magnification. Mann-Whitney U-test displayed a statistically significant higher mean rank among Filtek bulk fill group (mean rank = 23.09) when compared to Beautifil II LS composite group (mean rank = 11.91). The study concluded that in Class II restorations, Beautifil II LS showed significantly less microleakage than Filtek bulk fill posterior.

Experimental Investigation of a New Design of Insulation Gypsum Plaster Blocks

Green building materials are an alternative to ordinary materialsoffering multiple environmental benefits. This study consists of an experimental investigation of a new design of gypsum plaster blocks. First, a mix design of gypsum plaster and water mixture was prepared. The optimal mix composition was determined according to the mechanical and physical properties, such as the water absorption, the temperature of hydration, the density, and the compressive strength of different gypsum plaster and water mixtures made by varying the water dosage. The second part of this investigation aims to study a new design of green blocks prepared from the optimal water and gypsum plaster mixture. The new blocks are perforated to lighten them and to reduce their thermal conductivity in order to make them moreinsulate. Experimental tests were conducted on the block prototype, such as the measurement of dimensional tolerances, compressive strength, density, flatness, water absorption, residual moisture, surface hardness, and thermal conductivity. Experimental test results show that the new blocks have very low density, and their compressive strength is sufficient for wall construction. In addition, the manufacturing process of the new blocks is very easy and very fast. Finally, the obtained physical and mechanical properties of the new gypsum plaster blocks give it the opportunity to be used for interior walls for building constructions.

Frequency of MB2 in maxillary first and second molars in Gujarati population

Aim: The aim of this study was to investigate the frequency of second mesiobuccal canal in maxillary first and second molars. Materials and Methods: Maxillary fifty first molars and fifty second molars were collected and embedded into plaster blocks. The teeth were photographed digitally from the occlusal aspect using a stereomicroscope under standard (×8) magnification. The occlusal portions of crowns were then sectioned at cement–enamel junction with slow-speed diamond disk. To gain straight line visibility, overhung dentin over the canal orifices was removed with safe-tip diamond bur. Once again, the teeth were photographed from their occlusal aspect under the same magnification and exposure conditions. Results: MB2 canals were detected 76% and 64% in first and second molars, respectively.

Laboratory and discrete‐based numerical investigation on the collision problem of impactor‐block systems with soft‐porous and hard‐crystalline analog rocks

AbstractWe investigated experimentally the normal coefficient of restitution (COR) of impactors colliding on the surfaces of two different blocks; a soft‐porous block composed of plaster (dry impacts) and a hard‐crystalline rock composed of granite (dry and wet impacts). The experiments were performed in a range of low‐impact velocities and various particle types were used including perfectly spherical smooth glass beads and ceramic balls, rough glass beads as well as natural rough sand grains. Image processing was carried out to quantify the formed contours of craters caused by the surface damage of the soft blocks due to the impact. The results indicated very low COR values on the plaster block compared with the granite block as the energy was dissipated by means of surface plastic deformations on the plaster, however the contour crater images showed that the collision mechanisms depended on the roughness of the impactor. The behavior of impactor‐fluid‐block systems was dependent on both surface roughness and global morphology of the impactors. Discrete‐based (DEM) numerical simulations were performed to provide further insights into the behavior of the impactor‐block systems subjected to collision using the COR values from the experiments as the micro‐scale parameters and data from the literature as the macro‐scale parameters for the model calibration. The numerical output was used to observe the development of compression and tension force chain networks and how these involved during and after impact on different base blocks.

A Focus Control System Based on Varifocal Mirror for CO2 Fiber-Coupled Laser Surgery

Fiber-coupled laser tools combine the precision of lasers with the flexibility of optical fibers. They have been used in surgical procedures, such as transoral microsurgery, to perform precise incisions in delicate structures that are often difficult to reach with other tools. Unfortunately, the performance of fiber tools is not akin to that of traditional laser systems. Prioritizing miniaturization, these tools typically use no optics and ablate tissue in near-contact mode, which induces significant level of tissue carbonization. To avoid this problem, we have developed a focus control system designed for fiber-coupled laser tools based on a microfabricated varifocal mirror. We have demonstrated the efficiency of the system by adjusting the focusing of a CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser beam when ablating plaster block targets while varying the distance to the target within the range of 10mm to 25mm. The proposed system was able to ablate uniform lines, with an average width of 420 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and showed higher precision than fixed focus and bare fiber systems.

Assessment of Artifacts Induced by Various Dental Restorative Materials on Cone-Beam Computed Tomography- An in vitro Study

Objectives: The aim of this study was to assess and compare quantitatively and qualitatively the artifacts induced by various commonly used dental restorative materials in different sections of CBCT image and to characterize the pattern of artifact. Material and Methods: Thirty dental plaster blocks, each with one of each of mandibular second premolar, first molar and second molar teeth with crowns aligned as in the natural dentition were scanned by CBCT device and analyzed using CS 3D imaging software, before and after the first molar was prepared and restored with dental amalgam, composite resin or glass ionomer cement (GIC), 10 plaster blocks being randomly selected for each restorative material. The reformatted axial, coronal and sagittal scans were then quantitatively assessed for artifact by two calibrated dento- maxillofacial radiologists by comparing the control and restored scans of each plaster block in a blinded manner and documented the slice numbers from which the image became diagnostic. Then, the slice numbers were converted into millimeters away from the restoration. Results: Paired t test, ANOVA and post hoc Tukey tests were used for statistical analyses. The level of significance was set at α = 5%. Depending on the extent, the majority of artifacts produced were as follows: Dental amalgam &gt;Composite resin &gt;GIC. The artifact was most extensive in the coronal section. Streaks and scatter artifacts, linear artifacts extending outward from tooth surface and hypodense halo were predominant. Conclusion: Different dental restorative materials cause various amounts of artifacts in different planes of projection of CBCT image due to differences in density and atomic number.

COMPARATIVE EVALUATION OF PUSH-OUT BOND STRENGTH OF FIBER POST LUTED INSIDE THE ROOT CANAL USING LIGHT CURE FLOWABLE COMPOSITE AND DUAL CURE RESIN - AN INVITRO STUDY

Aim: The aim of this study was to compare by means of Push-Out test the difference in bond strength of two different luting agents with fibre post, and the effect of anatomical root levels on the bond strength of each cement. Materials and Methods: A total of 40 freshly extracted maxillary central incisor and canine teeth were included in the study. The teeth were divided into two groups of twenty each, and were assigned to Groups A and B according to the luting agent (light cure, dual cure) used to cement the post inside the root canal. After decoronation, 10 mm standardized post spaces were prepared inside each root. Luting of fiber posts was carried out, as per manufacturers recommendations, with the respective luting agents. Each root was embedded in a cuboidal plaster block and sectioning was carried out to obtain three slices of 2.5 mm thickness from the coronal, middle and apical aspect of the root. This was followed by Push-Out testing on a Universal Testing Machine after a storage period of 2 months. The recorded data were subjected to statistical analysis. Results: Significant differences were found in the bond strength of light cure flowable composite and dual cure resin cement (p&lt;.05) at different anatomical root levels. In the inter-group comparison it was found that dual cure presents superior mean bond strength in comparison with light cure composite. Conclusion: It was concluded from this study that dual cure resin cement is the best material for luting fiber post to root canal. The push-out bond strength was lower in the apical third than the coronal third for light activated cements. Also, light cure flowable composite performs better when shorter posts are used.

Biological and practical tradeoffs in planting techniques for submerged aquatic vegetation

Abstract Global loss of submerged aquatic vegetation (SAV) and associated ecosystem function has prompted an interest in SAV revegetation, particularly where underlying stressors such as nutrient enrichment are mitigated, yet natural recruitment remains low. Typically, SAV is hand-planted, but alternative reliable and practically scalable SAV planting techniques are needed. In mesocosms, we evaluated five planting techniques: 1) hand planting, anchoring using 2) fishing weights and 3) plaster blocks, and sediment-added methods using 4) peat pots and 5) burlap-wraps (“burritos”). Anchoring and sediment-added techniques were also field evaluated at four locations within a single lake. In mesocosms, all techniques effectively established two common North American SAV species, Vallisneria americana and Potamogeton illinoensis. Sediment-added techniques had species-specific benefits, e.g. burritos produced taller Vallisneria leaves, and greater Potamogeton biomass, while peat pots encouraged rapid Vallisneria shoot production. However, no treatment was universally beneficial across all growth metrics. In the field, all techniques were effective at two sites, but at two other sites, no techniques were successful. Results show that under favorable mesocosm and field conditions, all techniques promote establishment; however, subtle differences in technique-driven plant traits (height, density, nutrients) suggest that under specific environmental conditions, some techniques may be more favorable. Also, no technique offers practical advantages in every scenario, but each offers situation-specific advantages. Guidance emerging from this work is that all techniques are potentially effective, but small-scale tests in site-specific restoration scenarios, along with consideration of feasibility constraints, are recommended to inform large-scale plantings.

COMPARATIVE STUDY OF CO2 EMISSIONS FROM CERAMIC BRICK AND PLASTER BLOCK VERTICAL SEALS

The objective of this study is to compare the carbon dioxide (CO2) emissions from materials used in the execution of internal building masonry for construction projects that use plaster blocks and those using ceramic bricks. A total of 20 projects in the city of Recife, Brazil, were analyzed, all of them belonging to a large construction company operating in the Northeast region. The Greenhouse Gas (GHG) emissions were estimated using indexes found in the literature and calculated based on the Energy Life Cycle Assessment (ELCA). The emissions from the transport of materials to the construction site were calculated based on the driving distances between the suppliers and the building sites, taking into account the fuel consumption of the transport vehicles. The construction sites using plaster blocks for the internal masonry seals obtained an average indicator of 19.21 kgCO2/m² of constructed area compared to 33.86 kgCO2/m² from those using ceramic bricks. Construction sites using plaster blocks for internal masonry had a 43.26% reduction in GHG emissions and there was a strong correlation between costs due to the execution of activities and material emissions.

COMPARATIVE STUDY OF CO2 EMISSIONS FROM CERAMIC BRICK AND PLASTER BLOCK VERTICAL SEALS

The objective of this study is to compare the carbon dioxide (CO2) emissions from materials used in the execution of internal building masonry for construction projects that use plaster blocks and those using ceramic bricks. A total of 20 projects in the city of Recife, Brazil, were analyzed, all of them belonging to a large construction company operating in the Northeast region. The Greenhouse Gas (GHG) emissions were estimated using indexes found in the literature and calculated based on the Energy Life Cycle Assessment (ELCA). The emissions from the transport of materials to the construction site were calculated based on the driving distances between the suppliers and the building sites, taking into account the fuel consumption of the transport vehicles. The construction sites using plaster blocks for the internal masonry seals obtained an average indicator of 19.21 kgCO2/m² of constructed area compared to 33.86 kgCO2/m² from those using ceramic bricks. Construction sites using plaster blocks for internal masonry had a 43.26% reduction in GHG emissions and there was a strong correlation between costs due to the execution of activities and material emissions.

Is the digital radiographic detection of approximal caries lesions influenced by viewing conditions?

The aim of this study was to assess the influence of different viewing conditions (combinations of computer display, horizontal viewing angle, and ambient lighting) on the detection of approximal caries lesions on digital radiographic images. Forty posterior teeth were mounted in a plaster block and radiographed by using a CMOS sensor-based system. Three oral radiologists assessed the radiographic images under different conditions of computer display (iMac 5K 27", Barco MDRC-2124, and Dell P2314H), horizontal viewing angles (90 degrees, 67.5 degrees, and 45 degrees), and ambient lighting (low, medium, and high) and were asked to detect the presence of approximal caries lesions, which were confirmed by means of micro-computed tomography (micro-CT), using a 5-point scale. The area under the receiver operating characteristic curve, sensitivity, and specificity were calculated and compared by analysis of variance testing (α = 0.05). Intra- and interobserver agreements were assessed with the Kappa test. Computer display, horizontal viewing angle, and ambient lighting did not significantly influence the diagnosis of approximal caries lesions. In general, moderate values of accuracy, low sensitivity, and high specificity were found for all viewing conditions. The viewing conditions assessed in this study did not influence the detection of approximal caries lesions on digital radiographic images. Dental practitioners are encouraged to find their most comfortable viewing condition for this diagnostic task.

Numerical Analysis of Hygrothermal Building Performance of Gypsum Houses in Brazil

In this study, it is presented a simple modular constructive system based in plaster blocks. It is argued that this building system considerably reduces hand labour, execution time and the final cost of construction. This is particularly important in a country whose goal is to reach 3 million new homes in a brief time. However, the evaluation of the durability of the solutions should be analysed as well as the implementation and performance in various climates Brazil. The hygrothermal performance of the gypsum plaster house was assessed by advanced modelling using WUFI Plus software. The numerical results obtained allowed a discussion on the indoor comfort and energy consumption. For the development of this study, it was important an analysis of the housing deficit in Brazil, in order to look to the world. The analysis indicates a clear need for new housing construction in the country. Preferably should be chosen constructive solutions, simple, fast and easy to implement, without neglecting the comfort and durability. The use of local endogenous natural resources such as plaster, can be an attractive solution from an environmental point of view as well as economical. Thus, an innovative modular building system based on plaster blocks is displayed and monitored to validate the advanced simulation program used. It has been developed a comprehensive numerical simulation study to evaluate the influence of several thermal parameters (thermal insulation of walls and roofs, night ventilation and window solar factor), in the thermal performance of a typical gypsum house.

The tooth as a monitor of cholestatic liver disease in rats

Measure, noninvasively, the deposition of bilirubin in the tooth by using DIAGNOdent and correlate it to liver dysfunction. After confirming the capacity of DIAGNOdent to measure varying bile concentrations in plaster blocks, a cholestatic liver disease model was studied to detect increasing bilirubin impregnation in the teeth of rats. Wistar-EPM rats (n=50) were divided into three groups: (1) BDL: rats submitted to bile duct ligation (BDL); (2) Naïve: rats without procedure; and (3) Sham: rats submitted to laparotomy without BDL (n=10/period/group). The rats' teeth were monitored with the use of DIAGNOdent before the procedure and at days 10 and 50 following surgery. Serum bilirubin was also monitored. Tests invitro showed that DIAGNOdent detected bile in plaster blocks according to its concentration. BDL promoted progressive liver dysfunction, with death occurring approximately 50days later. DIAGNOdent values obtained on teeth showed correlation with the progression of serum hyperbilirubinemia. The tooth was found to be a good tissue for noninvasively monitoring the progression of bilirubinemia in cholestatic liver disease in rats by using DIAGNOdent.

Comparative evaluation of antimicrobial substantivity of different concentrations of chlorhexidine as a root canal irrigant: An in vitro study

IntroductionThe aim of this in vitro study was to evaluate and compare the antimicrobial substantivity of different concentrations of chlorohexidine as root canal irrigant by microbiological assay using mitis salivarius bacitracin streptomycin, MSBS agar plate. MethodsExtracted single rooted permanent human teeth were selected as samples and randomly divided into four groups (three experimental, one control). The samples of the three experimental groups used different concentration of chlorhexidine, CHX (0.1%, 1% and 2%), deionized water used as an irrigant served as control. In each group the apices of teeth were sealed with composite and mounted on plaster blocks. Root canals were prepared using step back technique and enlarged upto no 80. With each change in the file size the corresponding irrigant was used and final irrigation was done with deionized water. Samples were taken with paper points at 12 h, 1 day, 2 days and 3 days respectively and stored in sterile phials which were then arranged on MSBS agar plates for microbiological assay. Results and conclusionResults were analysed by ANOVA and Tukey's HSD test showed that antibacterial substantivity of 2% CHX was best followed by 1% CHX and 0.1% CHX in decreasing order respectively.

Enriching Tortoises: Assessing Color Preference

Environmental enrichment is a principle that is used to enhance the quality of care for nonhuman animals in captivity. To achieve this, it is necessary to understand the animal's needs. This study focused on color preference to provide food stimuli as a source of environmental enrichment for the tortoise, Chelonoidis denticulata. During this study, the stimuli green-, blue-, yellow-, and red-colored bananas and plaster blocks were randomly offered to the tortoises. Analysis of the data showed that the tortoises had a preference for the stimuli dyed with colors red and yellow over the other presented colors. It was possible to conclude that presenting food in different colors stimulated the animals to evaluate their environment and make choices in relation to their color preference. Thus, this experiment introduced an element of choice into their lives, beyond identifying color food preferences for the tortoises. The element of choice is known to be important to animal welfare.

Assessment of metal artifacts in three-dimensional dental surface models derived by cone-beam computed tomography.

ObjectiveThe aim of this study was to assess artifacts induced by metallic restorations in three-dimensional (3D) dental surface models derived by cone-beam computed tomography (CBCT).MethodsFifteen specimens, each with four extracted human premolars and molars embedded in a plaster block, were scanned by CBCT before and after the cavitated second premolars were restored with dental amalgam. Five consecutive surface models of each specimen were created according to increasing restoration size: no restoration (control) and small occlusal, large occlusal, disto-occlusal, and mesio-occluso-distal restorations. After registering each restored model with the control model, maximum linear discrepancy, area, and intensity of the artifacts were measured and compared.ResultsArtifacts developed mostly on the buccal and lingual surfaces. They occurred not only on the second premolar but also on the first premolar and first molar. The parametric values increased significantly with increasing restoration size.ConclusionsMetallic restorations induce considerable artifacts in 3D dental surface models. Artifact reduction should be taken into consideration for a proper diagnosis and treatment planning when using 3D surface model derived by CBCT in dentofacial deformity patients.