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.

The Importance of Being Honest

3D Printing ◽  
2017 ◽  
pp. 333-360 ◽  
Author(s):  
Stefano Brusaporci
Keyword(s):  
Scientific Computing ◽  
3D Model ◽  
Digital Model ◽  
Historic Buildings ◽  
Historical Buildings ◽  
Architectural Heritage ◽  
Digital Heritage ◽  
Digital Modeling ◽  
Scientific Analysis ◽  
The Relationship

The chapter presents a reflection on the concept of transparency in digital modeling and visualization of Architectural Heritage. Moving from topics of transparency and from the experiences in using paradata in different fields to state model's source, the degree of reliability of virtual re-constructions, and to made the digital model testable by other professionals, transparency and paradata are studied and declined for a dedicated application to historical buildings. In fact paradata is useful for model's design, use, management, diffusion, archiving, and interoperability. This according to an aim of model's intellectual transparency, and scientific computing and visualization of historic buildings. Follows issues about: the relationship between physical and digital heritage, the design of the digital 3D model and the database, the communication of transparency through spatial visualizations and multiple windowed representations, the transparency as possible methodological workflow for scientific analysis.

scholarly journals Model Analysis of Digital Models in Moderate to Severe Crowding: In Vivo Validation and Clinical Application

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Jae Hee Yoon ◽  
Hyung-Seog Yu ◽  
Yoonjeong Choi ◽  
Tae-Hyun Choi ◽  
Sung-Hwan Choi ◽  
...  
Keyword(s):  
Clinical Application ◽  
Digital Model ◽  
Digital Models ◽  
Linear Measurements ◽  
Significant Difference ◽  
Cast Model ◽  
Clinically Significant ◽  
Plaster Model ◽  
Model C

Objective. We investigated the suitability of intraoral-scan models for measuring tooth dimensions and the amount of crowding in patients with severe tooth crowding. Materials and Methods. Fifty-eight patients who had undergone intraoral scans for diagnosis were included. Cast models were divided into two groups depending on the amount of crowding, as determined by initial caliper-based measurements (mild crowding [MC] group: <3.0 mm; severe crowding [SC] group: >4.5 mm). Twenty maxillary models and 20 mandibular models were used in this study. For the three types of models (i.e., IS digital model, C cast model, and CS digital model), the reproducibility and the precision of linear measurements were evaluated. Results. We found that linear measurements made using digital calipers on a plaster model and on the relevant software were reproducible. There was no significant difference in most linear measurements between digital models and the C model. There were differences in the amount of crowding (p<.05), although these were not clinically significant. There was no relationship between the precision of crowding in the three types of models and the severity of crowding. Conclusions. Digital models can be used for measuring crowding in both mild and severe crowding cases. However, crowding measured by digital models tends to be lesser than that measured by cast models, and this should be considered during clinical application.

The Importance of Being Honest

2017 ◽  
pp. 66-93 ◽  
Author(s):  
Stefano Brusaporci
Keyword(s):  
Scientific Computing ◽  
3D Model ◽  
Digital Model ◽  
Historic Buildings ◽  
Historical Buildings ◽  
Architectural Heritage ◽  
Digital Heritage ◽  
Digital Modeling ◽  
Scientific Analysis ◽  
The Relationship

The chapter presents a reflection on the concept of transparency in digital modeling and visualization of Architectural Heritage. Moving from topics of transparency and from the experiences in using paradata in different fields to state model's source, the degree of reliability of virtual re-constructions, and to made the digital model testable by other professionals, transparency and paradata are studied and declined for a dedicated application to historical buildings. In fact paradata is useful for model's design, use, management, diffusion, archiving, and interoperability. This according to an aim of model's intellectual transparency, and scientific computing and visualization of historic buildings. Follows issues about: the relationship between physical and digital heritage, the design of the digital 3D model and the database, the communication of transparency through spatial visualizations and multiple windowed representations, the transparency as possible methodological workflow for scientific analysis.

Do Extra-Platelet Sources Contribute to the Plasma Level of Thrombospondin?

1988 ◽  
Vol 59 (02) ◽  
pp. 273-276 ◽  
Author(s):  
J Dawes ◽  
D A Pratt ◽  
M S Dewar ◽  
F E Preston
Keyword(s):  
Platelet Count ◽  
Background Concentration ◽  
Serum Concentrations ◽  
Bone Marrow Depression ◽  
Serial Sampling ◽  
Control Serum ◽  
Platelet Release ◽  
Highly Correlated ◽  
The Relationship

SummaryThrombospondin, a trimeric glycoprotein contained in the platelet α-granules, has been proposed as a marker of in vivo platelet activation. However, it is also synthesised by a range of other cells. The extraplatelet contribution to plasma levels of thrombospondin was therefore estimated by investigating the relationship between plasma thrombospondin levels and platelet count in samples from profoundly thrombocytopenic patients with marrow hypoplasia, using the platelet-specific α-granule protein β-thromboglobulin as control. Serum concentrations of both proteins were highly correlated with platelet count, but while plasma β-thromboglobulin levels and platelet count also correlated, there was no relationship between the number of platelets and thrombospondin concentrations in plasma. Serial sampling of patients recovering from bone marrow depression indicated that the plasma thrombospondin contributed by platelets is superimposed on a background concentration of at least 50 ng/ml probably derived from a non-platelet source, and plasma thrombospondin levels do not simply reflect platelet release.

Plasminogen Depletion during Streptokinase Treatment or Two-Chain Urokinase Incubation Correlates with Decreased Clot Lysability Ex Vivo and In Vitro

1993 ◽  
Vol 70 (06) ◽  
pp. 0998-1004 ◽  
Author(s):  
Páll T Önundarson ◽  
H Magnús Haraldsson ◽  
Lena Bergmann ◽  
Charles W Francis ◽  
Victor J Marder
Keyword(s):  
Myocardial Infarction ◽  
Ex Vivo ◽  
Time Dependent ◽  
State Variables ◽  
Thrombolytic Treatment ◽  
Direct Proportion ◽  
Plasmin Activity ◽  
Plasma Exposure ◽  
The Relationship

SummaryThe relationship between lytic state variables and ex vivo clot lysability was investigated in blood drawn from patients during streptokinase administration for acute myocardial infarction. A lytic state was already evident after 5 min of treatment and after 20 min the plasminogen concentration had decreased to 24%, antiplasmin to 7% and fibrinogen 0.2 g/1. Lysis of radiolabeled retracted clots in the patient plasmas decreased from 37 ± 8% after 5 min to 21 ± 8% at 10 min and was significantly lower (8 ± 9%, p <0.005) in samples drawn at 20, 40 and 80 min. Clot lysability correlated positively with the plasminogen concentration (r = 0.78, p = 0.003), but not with plasmin activity. Suspension of radiolabeled clots in normal plasma pre-exposed to 250 U/ml two-chain urokinase for varying time to induce an in vitro lytic state was also associated with decreasing clot lysability in direct proportion with the duration of prior plasma exposure to urokinase. The decreased lysability correlated with the time-dependent reduction in plasminogen concentration (r = 0.88, p <0.0005). Thus, clot lysability decreases in conjunction with the development of the lytic state and the associated plasminogen depletion. The lytic state may therefore limit reperfusion during thrombolytic treatment.

scholarly journals A New Method to Evaluate Trueness and Precision of Digital and Conventional Impression Techniques for Complete Dental Arch

2021 ◽  
Vol 11 (10) ◽  
pp. 4612
Author(s):  
KweonSoo Seo ◽  
Sunjai Kim
Keyword(s):  
Intraclass Correlation ◽  
Three Dimensional ◽  
New Method ◽  
Digital Impression ◽  
Dental Arch ◽  
Digital Models ◽  
Digital Impressions ◽  
Measuring Machine ◽  
Master Model ◽  
Conventional Impression

Purpose: The aim of this study was to present a new method to analyze the three-dimensional accuracy of complete-arch dental impressions and verify the reliability of the method. Additionally, the accuracies of conventional and intraoral digital impressions were compared using the new method. Methods: A master model was fabricated using 14 milled polyetheretherketone cylinders and a maxillary acrylic model. Each cylinder was positioned and named according to its corresponding tooth position. Twenty-five definitive stone casts were fabricated using conventional impressions of the master model. An intraoral scanner was used to scan the master model 25 times to fabricate 25 digital models. A coordinate measuring machine was used to physically probe each cylinder in the master model and definitive casts. An inspection software was used to probe cylinders of digital models. A three-dimensional part coordinate system was defined and used to compute the centroid coordinate of each cylinder. Intraclass correlation coefficient (ICC) was evaluated to examine the reliability of the new method. Independent two sample t-test was performed to compare the trueness and precision of conventional and intraoral digital impressions (α = 0.05). Results: ICC results showed that, the new method had almost perfect reliability for the measurements of the master model, conventional and digital impression. Conventional impression showed more accurate absolute trueness and precision than intraoral digital impression for most of the tooth positions (p < 0.05). Conclusions: The new method was reliable to analyze the three-dimensional deviation of complete-arch impressions. Conventional impression was still more accurate than digital intraoral impression for complete arches.

scholarly journals Marginal quantile regression for longitudinal data analysis in the presence of time-dependent covariates

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
I-Chen Chen ◽  
Philip M. Westgate
Keyword(s):  
Parameter Estimation ◽  
Longitudinal Data ◽  
Quantile Regression ◽  
Mean Squared Error ◽  
Time Dependent ◽  
Regression Methods ◽  
Squared Error ◽  
Highly Correlated ◽  
Time Dependent Covariates ◽  
Independence Structure

AbstractWhen observations are correlated, modeling the within-subject correlation structure using quantile regression for longitudinal data can be difficult unless a working independence structure is utilized. Although this approach ensures consistent estimators of the regression coefficients, it may result in less efficient regression parameter estimation when data are highly correlated. Therefore, several marginal quantile regression methods have been proposed to improve parameter estimation. In a longitudinal study some of the covariates may change their values over time, and the topic of time-dependent covariate has not been explored in the marginal quantile literature. As a result, we propose an approach for marginal quantile regression in the presence of time-dependent covariates, which includes a strategy to select a working type of time-dependency. In this manuscript, we demonstrate that our proposed method has the potential to improve power relative to the independence estimating equations approach due to the reduction of mean squared error.

Prediction of Hearing Threshold in Infants Using Auditory Steady-State Evoked Potentials

2002 ◽  
Vol 13 (05) ◽  
pp. 236-245 ◽  
Author(s):  
Gary Rance ◽  
Field Rickards
Keyword(s):  
Hearing Loss ◽  
Steady State ◽  
Hearing Threshold ◽  
Normal Hearing ◽  
Older Children ◽  
Behavioral Thresholds ◽  
Similar Threshold ◽  
Highly Correlated ◽  
The Relationship ◽  
Audiometric Test

This retrospective study examines the relationship between auditory steady-state evoked potential (ASSEP) thresholds determined in infancy and subsequently obtained behavioral hearing levels in children with normal hearing or varying degrees of sensorineural hearing loss. Overall, the results from 211 subjects showed that the two test techniques were highly correlated, with Pearson r values exceeding .95 at each of the audiometric test frequencies between 500 and 4000 Hz. Analysis of the findings for babies with significant hearing loss (moderate to profound levels) showed similar threshold relationships to those obtained in previous studies involving adults and older children. The results for infants with normal or near-normal hearing did, however, differ from those reported for older subjects, with behavioral thresholds typically 10 to 15 dB better than would have been predicted from their ASSEP levels.

scholarly journals Cats in the forest: predicting habitat adaptations from humerus morphometry in extant and fossil Felidae (Carnivora)

Paleobiology ◽  
10.1666/12001 ◽  
2013 ◽  
Vol 39 (3) ◽  
pp. 323-344 ◽  
Author(s):  
Carlo Meloro ◽  
Sarah Elton ◽  
Julien Louys ◽  
Laura C. Bishop ◽  
Peter Ditchfield
Keyword(s):  
Morphological Variability ◽  
Olduvai Gorge ◽  
Environmental Predictors ◽  
Linear Measurements ◽  
Multivariate Statistical ◽  
Linear Discriminant ◽  
Related Group ◽  
Discriminant Analyses ◽  
The Stability ◽  
The Relationship

Mammalian carnivores are rarely incorporated in paleoenvironmental reconstructions, largely because of their rarity within the fossil record. However, multivariate statistical modeling can be successfully used to quantify specific anatomical features as environmental predictors. Here we explore morphological variability of the humerus in a closely related group of predators (Felidae) to investigate the relationship between morphometric descriptors and habitat categories. We analyze linear measurements of the humerus in three different morphometric combinations (log-transformed, size-free, and ratio), and explore four distinct ways of categorizing habitat adaptations. Open, Mixed, and Closed categories are defined according to criteria based on traditional descriptions of species, distributions, and biome occupancy. Extensive exploratory work is presented using linear discriminant analyses and several fossils are included to provide paleoecological reconstructions.We found no significant differences in the predictive power of distinct morphometric descriptors or habitat criteria, although sample splitting into small and large cat guilds greatly improves the stability of the models. Significant insights emerge for three long-canine cats:Smilodon populator,Paramachairodus orientalis, andDinofelissp. from Olduvai Gorge (East Africa).S. populatorandP. orientalisare both predicted to have been closed-habitat adapted taxa. The false “sabertooth”Dinofelissp. from Olduvai Gorge is predicted to be adapted to mixed habitat. The application of felid humerus ecomorphology to the carnivoran record of Olduvai Gorge shows that the older stratigraphic levels (Bed I, 1.99–1.79 Ma) included a broader range of environments than Beds II or V, where there is an abundance of cats adapted to open environments.

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