scholarly journals Influence of Delayed Pours of Addition Silicone Impressions on The Dimensional Accuracy of Casts

2014 ◽  
Vol 8 (3) ◽  
pp. 148-153
Author(s):  
A Kumar ◽  
G Mahesh ◽  
R Mehta ◽  
S Pande ◽  
S Wadhwa ◽  
...  
Keyword(s):  
Dimensional Accuracy ◽  
Time Dependent ◽  
Master Model ◽  
Time Periods ◽  
Regular Body

ABSTRACT Aims and objectives To evaluate and compare the time dependent dimensional accuracy of polyvinyl siloxane impressions. Materials and methods A brass master die containing two identical posts simulating two complete crown tapered abutment preparation was served as a standardized master model. Impressions were made with polyvinyl siloxane materials (monophase and regular body) using a brass made custom tray. The impressions were poured at intervals of 75 min, 24 hours, 48 hours and 1 week, Interabutment and intraabutment distance were measured in the recovered stone dies using a profile projector with an accuracy of 0.001mm. Results Results of this study indicated that the casts made were dimensionally accurate and the polyvinyl siloxane silicones are dimensionally stable impressions for one week period. Conclusion Delayed pouring of the impressions at four different time periods did not significantly affect the accuracy of the casts produced.

scholarly journals Evaluation and Comparison of Dimensional Accuracy of Newly Introduced Elastomeric Impression Material using 3D Laser Scanners: An in vitro Study

2013 ◽  
Vol 14 (2) ◽  
pp. 265-268 ◽  
Author(s):  
Naveen S Yadav ◽  
Teerthesh Jain ◽  
Amrita Pandita ◽  
SMA Feroz ◽  
Pradeep LNU ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Laser Scanner ◽  
In Vitro Study ◽  
Dimensional Accuracy ◽  
Time Intervals ◽  
Impression Material ◽  
Impression Materials ◽  
Laser Scanners ◽  
Master Model

ABSTRACT Aim Aim of the present study was to comparatively evaluate dimensional accuracy of newely introduced elastomeric impression material after repeated pours at different time intervals. Materials and methods In the present study a total of 20 (10 + 10) impressions of master model were made from vinyl polyether silicone and vinyl polysiloxane impression material. Each impression was repeatedly poured at 1, 24 hours and 14 days. Therefore, a total of 60 casts were obtained. Casts obtained were scanned with three-dimensional (3D) laser scanner and measurements were done. Results Vinyl polyether silicone produced overall undersized dies, with greatest change being 0.14% only after 14 days. Vinyl polysiloxane produced smaller dies after 1 and 24 hours and larger dies after 14 days, differing from master model by only 0.07% for the smallest die and to 0.02% for the largest die. Conclusion All the deviations measured from the master model with both the impression materials were within a clinically acceptable range. Clinical significance In a typical fixed prosthodontic treatment accuracy of prosthesis is critical as it determines the success, failure and the prognosis of treatment including abutments. This is mainly dependent upon fit of prosthesis which in turn is dependent on dimensional accuracy of dies, poured from elastomeric impressions. How to cite this article Pandita A, Jain T, Yadav NS, Feroz SMA, Pradeep, Diwedi A. Evaluation and Comparison of Dimensional Accuracy of Newly Introduced Elastomeric Impression Material using 3D Laser Scanners: An in vitro Study. J Contemp Dent Pract 2013;14(2):265-268.

scholarly journals Comparative Time-Dependent Evaluation of Dimensional Accuracy of Dies Using Different Tray Adhesives: An In Vitro Study

2018 ◽  
Vol 6 (02/03) ◽  
pp. 106-111
Author(s):  
Ramandeep Kaur ◽  
Manjit Kumar ◽  
Shailesh Jain ◽  
Neha Jindal
Keyword(s):  
Bond Strength ◽  
In Vitro Study ◽  
Dimensional Accuracy ◽  
Time Dependent ◽  
Time Intervals ◽  
Crosshead Speed ◽  
Significant Difference ◽  
Different Types ◽  
Separation Failure

Abstract Statement of Problem The adhesion of impression material to impression tray is very important. Tray adhesive plays a major role in making accurate impression. Although manufactures recommend the use of particular tray adhesives, comparison of their affective adhesiveness has not been reported. The effect of use of tray adhesives on dimensional accuracy of dies has not been established. Purpose The aim of this study was to compare the dimensional accuracy of dies using different tray adhesives at different time intervals. Materials and Methods First part of study comprised 120 samples in six groups with 20 samples in each group. First group comprised samples with no tray adhesive, and in other five groups, different types of tray adhesives were applied. The dies obtained were evaluated for upper diameter, lower diameter, and occlusogingival height. In the second part, there were a total of 125 samples in five groups with 25 samples in each group. Five different types of tray adhesive were applied for five different time intervals 5, 10, 15, 20, and 25 minutes, respectively. The specimens were tested in tensile mode for its debonding force at a crosshead speed of 5 mm/min, until separation failure occurred. Results Significant difference was seen for upper and lower diameters when compared with the group without any tray adhesive. The maximum bond strength was found in the group in which tray adhesive was applied for 20 minutes.

Cosmological Models in Lyra Geometry with Linearly Varying Deceleration Parameter

2018 ◽  
Author(s):  
Kalyani Desikan
Keyword(s):  
Exact Solutions ◽  
Displacement Field ◽  
Deceleration Parameter ◽  
Lyra Geometry ◽  
Cosmological Models ◽  
Time Dependent ◽  
Linearly Varying Deceleration Parameter ◽  
Frw Model ◽  
Time Periods ◽  
The Universe

Cosmological models with linearly varying deceleration parameter in the cosmological theory based on Lyra’s geometry have been discussed. Exact solutions have been obtained for a spatially flat FRW model by considering a time dependent displacement field. We have also obtained the time periods during which the universe undergoes decelerated and accelerated expansions for a matter-dominated universe.

scholarly journals Comparison of the accuracy of fixture-level impression making after splinting prosthetic components

2020 ◽  
Vol 10 (2) ◽  
pp. 5252-5258
Keyword(s):  
Dimensional Accuracy ◽  
Acrylic Resin ◽  
Significant Difference ◽  
Laboratory Procedures ◽  
Master Model ◽  
Implant Dentistry ◽  
Increase In Accuracy ◽  
Post Hoc ◽  
Digital Caliper ◽  
Specific Distance

Considering the effects of different impression-taking techniques on the dimensional accuracy of the final cast and controversies over the best technique in implant dentistry, the present study was undertaken to evaluate the effects of three different open-tray impression techniques on the dimensional accuracy of final casts for implants. A two-piece metallic index was prepared and a patient’s jaw was simulated by placing self-cured acrylic resin in the lower part of the index. Then 2 holes were produced in the acrylic resin at a specific distance from each other, and the analogs were placed in these holes. Three different open-tray impression techniques were evaluated using the upper segment of the index, which mimicked the specific tray. The dimensional accuracy of the casts was evaluated by comparing the distances between the predetermined points on the implant analogs and the positions of the points with similar distances on the master model. A digital caliper (accurate to 0.01 mm) was used to measure the distances. The differences in the measurements on the final casts were analyzed with SPSS 16, using Kruskal-Wallis test. Post hoc Mann-Whitney U test was used for two-by-two comparisons. There was a significant difference between the group in which the analogs and impression copings were not splinted and the group with impression coping splinting without analog splinting and the group with simultaneous splinting of the impression copings and implant analogs, in relation to distances between similar points on the master model. In this context, the second and third techniques better reconstructed the positions of the points. Splinting of impression copings with Duralay acrylic resin prevented the movement of impression copings during the impression-taking procedure and despite an increase in the accuracy of impression taking during splinting of analogs by Duralay acrylic resin, the increase in accuracy was not significant statistically; therefore, splinting of the impression copings without splinting of the analogs is recommended due to an increase in impression-taking accuracy and facilitation of laboratory procedures.

scholarly journals Beyond Microcystins: Cyanobacterial Extracts Induce Cytoskeletal Alterations in Rice Root Cells

2020 ◽  
Author(s):  
Dimitris Pappas ◽  
Manthos Panou ◽  
Ioannis-Dimosthenis S. Adamakis ◽  
Spyros Gkelis ◽  
Emmanuel Panteris
Keyword(s):  
Plant Cells ◽  
Time Dependent ◽  
Rice Root ◽  
Enzyme Assays ◽  
Root Cells ◽  
Alpha Tubulin ◽  
Actin Organization ◽  
Seedling Roots ◽  
Time Periods ◽  
Plant Cytoskeleton

Microcystins (MCs) are cyanobacterial toxins and potent inhibitors of protein phosphatases 1 (PP1) and 2A (PP2A), which are involved in plant cytoskeleton (microtubules and F-actin) organization. Therefore, studies on the toxicity of cyanobacterial products on plant cells have so far being focused on MCs. In this study, we investigated the effects of extracts from 16 (4 MC-producing and 12 non-MC-producing) cyanobacterial strains from several habitats, on various enzymes (PP1, trypsin, elastase), on the plant cytoskeleton and H2O2 levels in Oryza sativa (rice) root cells. Seedling roots were treated for various time periods (1, 12 and 24h) with aqueous cyanobacterial extracts and underwent either immunostaining for α-tubulin or staining of F-actin with fluorescent phalloidin. DCF-DA staining was performed for H2O2 imaging. The enzyme assays confirmed the bioactivity of the extracts of not only MC-rich (MC+), but also MC-devoid (MC-) extracts, which induced major time-dependent alterations on both components of the plant cytoskeleton. These findings suggest that a broad spectrum of bioactive cyanobacterial compounds, apart from MCs or other known cyanotoxins (such as cylindrospermopsin), can affect plants by disrupting the cytoskeleton.

The influence of storage conditions on the physicochemical properties and dimensional accuracy of the alginate impressions

2018 ◽  
Vol 2 (87) ◽  
pp. 68-76
Author(s):  
K. Żelezińska ◽  
M. Nowak ◽  
J. Żmudzki ◽  
C. Krawczyk ◽  
G. Chladek
Keyword(s):  
Tensile Strength ◽  
Design Methodology ◽  
Dimensional Accuracy ◽  
Storage Conditions ◽  
Materials Properties ◽  
Dimensional Changes ◽  
Impression Materials ◽  
Master Model ◽  
Good Relation ◽  
Practical Implications

Purpose: Alginate impression materials are the most commonly used masses for taking impressions. They are characterized by good relation of properties to the price. However, the main problem associated with use of the impression masses is dimensions stability. Manufacturers of alginate masses recommend storage impression without any source of moisture, but dentists frequently store impressions wrapped in a wet materials. This may be the a reason of changes in dimensions and other properties. Moreover, it is recognized, that casting the model in the soon after making impression guarantee better dimensional accuracy. However, models are made usually after 24h. For some masses producers claim unequivocally, that the impressions can be stored for up to 168 h without changing the dimensions. So in this study was investigates how storage conditions affect chosen properties of alginate mass, including the accuracy of the models. Design/methodology/approach: Samples were prepared according to the manufacturer instruction and divided into 5 groups. Measurements were made 20 min after taking the impression and after 24h/168h of storage with/ without the resource of moisture. The measurements of Shore A hardness, tensile strength, mass changes and dimensional changes were made. Accuracies of the dental stone models were investigated with models manufactured after 20 min and 168 h after impressions, in comparison to the master model. Findings: The study showed that the storage conditions and time of storage had influence on properties of alginate impression mass. The resource of moisture has got an influence on dimensions and mass changes, tensile strength, elongation and shore A hardness. The results show that the use of the resource of moisture may be a cause of unfavourable changes in the gypsum model dimensions. Research limitations/implications: The storing of the alginate impressions with the resource of moisture is commonly practiced by the doctors, but it inconsistent with the manufacturer's recommendation. Practical implications: The method storing of the alginate impressions determined not only the materials properties, but also the clinical properties of final products like dentures. Originality/value: The significant of the method of the storing of alginate impression materials on the chosen properties of the materials and the accuracy of the dental stone models were shown.

scholarly journals Effect of Corrosion Damage on the Performance Level of a 25-Year-Old Reinforced Concrete Building

2012 ◽  
Vol 19 (5) ◽  
pp. 891-902 ◽  
Author(s):  
Hakan Yalciner ◽  
Serhan Sensoy ◽  
Ozgur Eren
Keyword(s):  
Reinforced Concrete ◽  
Corrosion Rate ◽  
Plastic Hinge ◽  
Time Dependent ◽  
Earthquake Ground Motion ◽  
Rc Structures ◽  
Bond Slip ◽  
Structural Problems ◽  
Time Periods ◽  
The Impact

Corrosion is a long-term process resulting in the deterioration of the reinforced concrete (RC) structures. Most of the structural problems observed under the impact of either earthquakes or service loads might occur due to corrosion. Therefore, prediction of the remaining service life of a corroding RC structure plays an important role to prevent serious premature damage. In this study, a corroded, 25-year-old high school building which has been demolished at an earlier time was analyzed as a function of corrosion rate. Bond-slip relationships were taken into account in nonlinear analyses as a function of corrosion rate for different time periods (i.e., non-corroded (t: 0), existing (t: 25) and 50 years after construction); and they were used to ensure the effect of time-dependent slip rotation on the global structural behaviour by modifying the target post-yield stiffness of each structural member. Nonlinear push-over analyses were performed by defining the time-dependent plastic hinge properties as a consequence of corrosion effects. In order to define the performance levels of three different time periods, nonlinear incremental dynamic analyses (IDA) were performed for 20 earthquake ground motion records as a function of corrosion rate. Results showed that bond-slip relationship between concrete and steel is very important in evaluating the non-linear behaviour of corroded RC structures.

scholarly journals The Relationship between Digital Model Accuracy and Time-Dependent Deformation of Alginate Impressions

2009 ◽  
Vol 79 (1) ◽  
pp. 30-36 ◽  
Author(s):  
Toros Alcan ◽  
Cenk Ceylanoğlu ◽  
Bekir Baysal
Keyword(s):  
Time Dependent ◽  
Digital Model ◽  
Digital Models ◽  
Model Accuracy ◽  
Linear Measurements ◽  
Plastic Bags ◽  
Digital Modeling ◽  
Master Model ◽  
Highly Correlated ◽  
The Relationship

Abstract Objectives: To investigate the effects of different storage periods of alginate impressions on digital model accuracy. Materials and Methods: A total of 105 impressions were taken from a master model with three different brands of alginates and were poured into stone models in five different storage periods. In all, 21 stone models were poured and immediately were scanned, and 21 digital models were prepared. The remaining 84 impressions were poured after 1, 2, 3, and 4 days, respectively. Five linear measurements were made by three researchers on the master model, the stone models, and the digital models. Time-dependent deformation of alginate impressions at different storage periods and the accuracy of traditional stone models and digital models were evaluated separately. Results: Both the stone models and the digital models were highly correlated with the master model. Significant deformities in the alginate impressions were noted at different storage periods of 1 to 4 days. Alginate impressions of different brands also showed significant differences between each other on the first, third, and fourth days. Conclusions: Digital orthodontic models are as reliable as traditional stone models and probably will become the standard for orthodontic clinical use. Storing alginate impressions in sealed plastic bags for up to 4 days caused statistically significant deformation of alginate impressions, but the magnitude of these deformations did not appear to be clinically relevant and had no adverse effect on digital modeling.

scholarly journals EVALUATION OF THE GOALS SCORING PATTERNS AND THE RELATION BETWEEN TIME AND GOAL SCORING OF FOUR UEFA CHAMPIONS LEAGUE TOURNAMENTS

2018 ◽  
pp. 329
Author(s):  
Yiannis Michailidis ◽  
Athanasios Mandroukas ◽  
Lazaros Vardakis ◽  
Thomas Metaxas
Keyword(s):  
Data Analysis ◽  
Time Dependent ◽  
Chi Square ◽  
Extra Time ◽  
Time Period ◽  
Significant Difference ◽  
Pattern Comparison ◽  
Time Periods ◽  
Level Of Significance

The purpose of this study was to compare time period and patterns of goal scoring in four UEFA Champions League (UCL) tournaments (2013-2017). All matches (n=500) of the four Champions League tournaments were recorded using video and analyzed with the software Sportsscout. Chi-square methods were used for the data analysis and the level of significance was set at p<0.05. The time period and scoring pattern comparison between UCL tournaments did not present any significant difference (X2=84.500, p>0.05 for the time period, X2=25.350, p>0.05 for open play and X2=7.503, p>0.05 for set play). The 15-min analysis for each tournament did not show any significant difference if we exclude all extra time periods. However, in UCL 2013-2014 and 2015-2016 more goals were scored in the second half (X2=9.696, p<0.05 and X2=7.496, p<0.05, respectively). With open play more goals were scored than set play (75% and 25% average, respectively). The action that scored the most goals in open play was combination and crosses (21.6% and 22.4% respectively) and in set play was corners and penalties (33.9%, all). The results showed that no differences occurred between CLs regarding the scoring patterns and time periods of scoring. However, goal scoring might be time dependent because more goals were scored in the second half. An explanation for this could be the fatigue and the tactical strategy. About the patterns, coaches must focus on training crosses and passing combinations. Also, they should give a lot of attention to corners of set plays.

scholarly journals Dimensional Accuracy of Stone Casts Obtained with Multiple Pours into the Same Mold

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Valdimar da Silva Valente ◽  
Artêmio Luiz Zanetti ◽  
Pedro Paulo Feltrin ◽  
Ricardo Tatsuo Inoue ◽  
Carmem Dolores Vilarinho Soares de Moura ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Coordinate Measuring Machine ◽  
Dimensional Accuracy ◽  
Wait Time ◽  
Type Iv ◽  
Impression Technique ◽  
Fixed Prosthesis ◽  
Measuring Machine ◽  
Master Model ◽  
Made In

Aim. The aim of the present study was to compare the dimensional accuracy of stone casts obtained with vinyl polysiloxane molds through the double-impression technique with three pours into the same mold. Methods. A stainless steel master model was constructed simulating a three-unit fixed prosthesis. Twelve impressions were taken of this master model with addition silicone, using the double-impression technique. Three pours of type IV gypsum were then made into each mold, thus producing 36 casts. The pours were made 1 hour, 6 hours and 24 hours after the impression procedure. Next, intra- and interabutment measurements were made in a coordinate measuring machine. Results. Comparative analysis of the dimensional accuracy of stone casts resulting from multiple pours was not statistically significant in pours first and second (P>0.05). These values, however, were statistically significant at third pour in the height in abutment 1 and upper distance interabutment. Conclusion. The wait time (1 hour, and 6 hours) observed before pouring the stone into the same molds did not cause significant dimensional accuracy of the casts.

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