Color Difference Map Research Articles

Paper and nylon based optical tongues with poly(p-phenyleneethynylene)-fluorophores efficiently discriminate nitroarene-based explosives and pollutants

Discrimination of nitroarenes with hydrophobic dyes in a polar (H2O) environment is difficult but possible via a lab-on-chip, with polymeric dyes immobilized on paper or nylon membranes. Here arrays of 12 hydrophobic poly(p-phenyleneethynylene)s (PPEs), are assembled into a chemical tongue to detect/discriminate nitroarenes in water. The changes in fluorescence image of the PPEs when interacting with solutions of the nitroarenes were recorded and converted into color difference maps, followed by cluster analysis methods. The variable selection method for both paper and nylon devices selects a handful of PPEs at different pH-values that discriminate nitroaromatics reliably. The paper-based chemical tongue could accurately discriminate all studied nitroarenes whereas the nylon-based devices represented distinguishable optical signature for picric acid and 2,4,6-trinitrotoluene (TNT) with high accuracy.

Spatial Trueness Evaluation of 3D-Printed Dental Model Made of Photopolymer Resin: Use of Special Structurized Dental Model.

(1) Background: Various 3D printers are available for dental practice; however, a comprehensive accuracy evaluation method to effectively guide practitioners is lacking. This in vitro study aimed to propose an optimized method to evaluate the spatial trueness of a 3D-printed dental model made of photopolymer resin based on a special structurized dental model, and provide the preliminary evaluation results of six 3D printers. (2) Methods: A structurized dental model comprising several geometrical configurations was designed based on dental crown and arch measurement data reported in previous studies. Ninety-six feature sizes can be directly measured on this original model with minimized manual measurement errors. Six types of photo-curing 3D printers, including Objet30 Pro using the Polyjet technique, Projet 3510 HD Plus using the Multijet technique, Perfactory DDP and DLP 800d using the DLP technique, Form2 and Form3 using the SLA technique, and each printer's respective 3D-printable dental model materials, were used to fabricate one set of physical models each. Regarding the feature sizes of the simulated dental crowns and dental arches, linear measurements were recorded. The scanned digital models were compared with the design data, and 3D form errors (including overall 3D deviation; flatness, parallelism, and perpendicularity errors) were measured. (3) Results: The lowest overall 3D deviation, flatness, parallelism, and perpendicularity errors were noted for the models printed using the Objet30 Pro (overall value: 45 μm), Form3 (0.061 ± 0.019 mm), Objet30 Pro (0.138 ± 0.068°), and Projet 3510 HD Plus (0.095 ± 0.070°), respectively. In color difference maps, different deformation patterns were observed in the printed models. The feature size proved most accurate for the Objet30 Pro fabricated models (occlusal plane error: 0.02 ± 0.36%, occlusogingival direction error: -0.06 ± 0.09%). (4) Conclusions: The authors investigated a novel evaluation approach for the spatial trueness of a 3D-printed dental model made of photopolymer resin based on a structurized dental model. This method can objectively and comprehensively evaluate the spatial trueness of 3D-printed dental models and has a good repeatability and generalizability.

A visible colorimetric sensor array based on chemo-responsive dyes and chemometric algorithms for real-time potato quality monitoring systems

The colorimetric sensor array real-time monitoring system with multivariate analysis was established for discrimination of potato varieties with different types and degrees of corruption. The characteristic volatile compounds of fresh, dry rot and soft rot potatoes was identified by Gas Chromatography-Mass Spectrometry and the 3 × 4 array was fabricated to capture the characteristics volatile compounds. The sensor array system produced a visible color difference map upon its exposure to volatile compounds of potato. Discrimination of potatoes with the same types or different degrees of corruption was subsequently achieved using principal component analysis and hierarchical clustering analysis dendrogram. The k-nearest neighbor algorithm for potato classification provided the best results with 100 % discrimination on both the calibration and prediction sets. The linear discriminant analysis model achieved a 99.76 % calibration set and a 99.31 % prediction set for potato grading. An online warning device based on array was devised to realize unmanned monitoring for potato quality.

Trueness of intraoral scanning of edentulous arches: A comparative clinical study.

To compare the accuracy of intraoral scanning (IOS) of the edentulous arch with the hybrid protocol of cast digitization (CD), and to investigate the effect of arch type and area on trueness. Participants that were edentulous in both arches were recruited. Two impression protocols were used; the IOS as the test protocol with an IOS device (TRIOS 4; 3Shape, Denmark), and the CD as the control, including tracing compound (TRACING STICKS; Kemdent, UK) for border molding, polyvinyl siloxane (Hydrorise Monophase; Zhermack, Italy) for impression, and cast digitization with a laboratory scanner (ceramill® map400, AMANNGIRRBACH, Germany). Scanned files were exported to a 3D inspection software (Geomagic Control X; 3D Systems, NC) for trueness analysis. The CD file (reference file) for each participant was split into 2 areas; the dynamic area representing the mobile tissues at the peripheral border, and the static area representing the rest of the arch. Statistical analyses were performed with 1-sample t-test for the difference between CD and IOS protocols, paired sample t-test for the difference between the static and dynamic areas for each arch, and an independent sample t-test for the difference between the maxillary and mandibular arches for each area, with α=0.05. Effect size was calculated with Cohen's d (d), with 0.2 as small, 0.5 as medium, and 0.8 as large. A total of 21 participants were included. The difference between the IOS and CD protocol was significant for all subset comparisons (p<0.001, d: 2.5-6.2, large effect size). Dynamic areas had lower trueness in comparison with static areas (p<0.001, d=4.57, large effect size for the maxillary arch, p<0.001, d=3.96, large effect size for the mandibular arch). Mandibular arch had lower trueness in comparison with the maxillary arch (p<0.001, d=1.45, large effect size for the static areas, p=0.009, d=0.85, large effect size for the dynamic areas, p<0.001, d=1.71, large effect size for all areas). Color difference map showed marked positive deviation in the buccal dynamic areas of both arches, and nonmatching areas with evident overstretching. While the IOS of edentulous arches could be feasible for attached mucosa, providing a functional shape for the peripheral border remains a challenge, with a thinner and more outward border for the IOS in comparison with the CD protocol. The IOS of the mandibular arch is more difficult and has lower trueness in comparison with the maxillary arch.

Non-invasive detection of COVID-19 using a microfluidic-based colorimetric sensor array sensitive to urinary metabolites.

A colorimetric sensor array designed on a paper substrate with a microfluidic structure has been developed. This array is capable of detecting COVID-19 disease by tracking metabolites of urine samples. In order to determine minor metabolic changes, various colorimetric receptors consisting of gold and silver nanoparticles, metalloporphyrins, metal ion complexes, and pH-sensitive indicators are used in the array structure. By injecting a small volume of the urine sample, the color pattern of the sensor changes after 7 min, which can be observed visually. The color changes of the receptors (recorded by a scanner) are subsequently calculated by image analysis software and displayed as a color difference map. This study has been performed on 130 volunteers, including 60 patients infected by COVID-19, 55 healthy controls, and 15 cured individuals. The resulting array provides a fingerprint response for each category due to the differences in the metabolic profile of the urine sample. The principal component analysis-discriminant analysis confirms that the assay sensitivity to the correctly detected patient, healthy, and cured participants is equal to 73.3%, 74.5%, and 66.6%, respectively. Apart from COVID-19, other diseases such as chronic kidney disease, liver disorder, and diabetes may be detectable by the proposed sensor. However, this performance of the sensor must be tested in the studies with a larger sample size. These results show the possible feasibility of the sensor as a suitable alternative to costly and time-consuming standard methods for rapid detection and control of viral and bacterial infectious diseases and metabolic disorders.Graphical Supplementary InformationThe online version contains supplementary material available at 10.1007/s00604-022-05423-1.

Accuracy of zirconia crowns manufactured by stereolithography with an occlusal full-supporting structure: An in vitro study

Statement of problemAdditive manufacturing is emerging as an alternative method of fabricating dental restorations, but the support design needs to be optimized. PurposeThe purpose of this in vitro study was to evaluate the 3-dimensional trueness and adaptations of zirconia crowns manufactured by stereolithography (SLA) with an occlusal full-supporting structure, compared with those SLA-printed with pillar supports, and those made by milling. Material and methodsA zirconia abutment was prepared, and an anatomic contour crown was designed. The crowns were manufactured by SLA and milling (n=6). For SLA manufacturing, a full-supporting base and pillar supports were designed. The 3-dimensional (3D) trueness of the fabricated crowns was characterized by 3D deviation analysis. The adaptations of crowns in the SLA-base and milling groups were measured by using a triple-scan method. Color-difference maps and the root mean square (RMS) values were used to characterize the 3D trueness. One-way analysis of variance (ANOVA) and Tukey post hoc test were used to analyze the difference in RMS values among the 3 groups, and Student t test was used to analyze the difference in cement-gap width between the milling group and the SLA group with the full-supporting base (α=.05). ResultsThe 3D deviation analysis showed that in the external area, the RMS value of the SLA-pillar group was significantly higher than that of the SLA-base and the milling groups (P<.05). In the intaglio area, the milling group showed a lower RMS value than the 2 SLA groups (P<.05). The color-difference maps showed the SLA-base group had smaller positive errors at the cusp inclines than the SLA-pillar group. No statistically significant difference was found in adaptations between the SLA-base and milling groups (P>.05). ConclusionsThe occlusal full-supporting base provided improved support in fabricating the crowns, and no remnants were left after removal. The zirconia crowns manufactured by SLA with an occlusal full-supporting structure had good external 3D trueness and clinically acceptable adaptation.

Discrimination of basmati rice adulteration using colorimetric sensor array system

This study involved the fabrication of colorimetric sensor array system for rapid discrimination of adulterants in premium grade basmati rice. Purposely, low-grade white rice was used to adulterate the pure basmati rice at 5%, 10%, 15%, 25%, 50%, and 75% weight ratios. Sensor array system was used to capture the odors of prepared samples, resulting in color difference map based on chemical environment. The principal component analysis (PCA), hierarchical cluster analysis (HCA), and k-nearest neighbors (kNN) algorithm were subsequently used to identify the similarity between authentic and adulterated samples. A decent discrimination between authentic and adulterated rice samples was observed in the scatter plot of PCA and HCA dendrogram. The multilayered kNN models were able to effectively discriminate the prepared rice samples. The study concludes that fabricated sensor array system may be used as an effective tool for rapid discrimination of authentic and adulterated samples. • Colorimetric sensor array was fabricated for discrimination of rice adulteration. • Volatile compounds of basmati rice and adulterant were identified using GC-MS. • PCA and HCA were able to discriminate different levels of adulteration. • Optimal discrimination results were achieved with multilayered kNN algorithm. • Fabricated system promotes the development and application of sensor arrays.

Discrimination of rice varieties using smartphone-based colorimetric sensor arrays and gas chromatography techniques

A smartphone-based colorimetric sensor array system was established for discrimination of rice varieties having different geographical origins. Purposely, aroma profiling of nine rice varieties was performed using solid-phase microextraction gas chromatography-mass spectrometry. Alcohols, aldehydes, alkanes, ketones, heterocyclic compounds, and organic acids represent the abundant compounds. Colorimetric sensor array system produced a characteristic color difference map upon its exposure to volatile compounds of rice. Discrimination of rice varieties was subsequently achieved using principal component analysis, hierarchical clustering analysis, and k-nearest neighbors. Rice varieties from same geographical source were clustered together in the scatter plot of principal component analysis and hierarchical clustering analysis dendrogram. The k-nearest neighbors algorithm delivered optimal results with discrimination rate of 100% for both calibration and prediction sets using sensor array system. The smartphone-based colorimetric sensor array system and gas chromatography technique were able to effectively differentiate rice varieties with the advantage of being simple, rapid, and low-cost.

Collaboration of cyclometalated platinum complexes and metallic nanoclusters for rapid discrimination and detection of biogenic amines through a fluorometric paper-based sensor array

• A paper-based fluorescence sensor array is developed for biogenic amines. • Cyclometalated platinum complexes and metallic nanoclusters represent collaborative effects in detection and discrimination. • The sensor array offers rapid determination of biogenic amines in human urine. A simple and efficient fluorometric paper-based sensor array for discrimination and determination of biogenic amines (BAs) as biomarkers of graft injury has developed by combining two functional elements: (i) four cycloplatinated (II) complexes and (ii) eight metal nanoclusters with different capping agents. This combination provides a wide color emissive variation, when exposing to the BAs. The turn off interaction of the fluorescent sensor elements and BAs leads to the naked eye detectable colorimetric changes (under irradiation by UV lamp of 366 nm). Therefore, a distinct color difference map achieved for each BAs. It demonstrated that designed sensor array could discriminate BAs individually with 100% classification accuracy by principle component analysis and hierarchical cluster analysis. In addition, the proposed sensor can discriminate seven families of amines in the concentration range of 5–100 ppm. Besides, it was represented potential for quantitative assessment of hexylamine, dipropylamine, putrescine, pyridine and creatinine with limits of detections of 0.75, 0.72, 0.80, 1.7 and 1.4 ppm, respectively. The roles of each group of functional elements were investigated in qualitative and quantitative analysis. The sensor array containing four cycloplatinated (II) complexes represented higher discrimination ability whereas for quantitative analysis using all 12 elements in the sensor array gived better results. The feasibility of the real application of the fabricated sensor array was also confirmed via analyzing the five adult’s urine samples with appropriate sensitivity and accuracy.

Accuracy of three digital scanning methods for complete-arch tooth preparation: An in vitro comparison

Statement of problemThe accuracy of digital scanning for complete dental arch and implant-supported complete-arch restorations has been reported. However, research addressing the accuracy of digital scanning methods for complete-arch tooth preparation is lacking. PurposeThe purpose of this in vitro study was to compare the accuracy of intraoral scanning, impression scanning, and cast scanning for complete-arch preparation. Material and methodsMaxillary and mandibular jaw typodonts with 28 teeth prepared for complete crowns were used as reference casts and digitized as reference data sets with a desktop scanner. Three digital scanning methods were applied. First, the reference casts were each scanned 10 times with an intraoral scanner to generate the intraoral scanning group data sets. Second, the reference casts were each captured 10 times by using polyvinyl siloxane impression material, and the impressions were scanned with a desktop scanner to generate the impression scanning group data sets. Third, the impressions obtained in the impression scanning group were used to make gypsum casts which were then digitized with a desktop scanner to generate the cast scanning group data sets. Accuracy was determined by trueness and precision. Three-dimensional deviations of the prepared arches and anterior and posterior segments were measured from root mean square values and depicted on color-difference maps. Differences among test groups were analyzed by using a 1-way ANOVA and the post hoc Bonferroni test for normally distributed data or the Kruskal-Wallis test with Bonferroni correction for non-normally distributed data (α=.05). ResultsThe trueness of the maxillary arch was significantly higher in the impression scanning group than in the cast scanning and intraoral scanning groups (P<.05), but no significant differences were found among the 3 groups of the mandibular arch (P>.05). The precision of both arches was significantly higher in the impression scanning and intraoral scanning groups than in the cast scanning group (P<.05). Color maps showed horizontal symmetrical displacement in the intraoral scanning group relative to the reference data sets and within-group unilateral distal-end distortion. Irregular arch deformations were noted in the impression scanning group, and buccal and occlusal expansion occurred in the anterior-posterior direction in the cast scanning group. Pooled data for anterior teeth indicated that the trueness was lowest in the intraoral scanning group; however, that for the maxillary anterior teeth did not differ, while that for the mandibular anterior teeth differed significantly among groups (P<.05). For the posterior teeth, deviation was the lowest in the impression scanning group, and significant differences were noted in both arches among the 3 groups (P<.05). ConclusionsOf the methods tested, impression scanning was the most accurate for the creation of a digital cast of a complete prepared arch.

Spectrofluorimetric study of the complexation of ochratoxin A and Cu2+: Towards the hybrid fluorimetric sensor and visual detection of ochratoxin A in wheat flour samples from farm to fork

In this study, the ochratoxin A (OTA) interaction with some metal cations exhibits a quenching effect of the Cu2+, Co2+, and Ni2+ in the OTA intrinsic fluorescence intensity. The property of the OTA fluorescence change in complexation with the Cu2+ has been applied in developing a label-free and selective fluorimetric sensor for fast detection of the OTA trace amounts in wheat flour samples. The achieved color difference map (CDM) based on the spectral profile provides the technical support for the rapid visual sensing of OTA in the wheat flour samples. The feasibility of the hybrid fluorimetric sensor and visual OTA detection in wheat flour samples has been confirmed with the high-performance liquid chromatography (HPLC) method as a standard method. The calculated LOD (0.4 ng g−1) and LOQ (1.2 ng g−1) values of the proposed method are much lower than the maximum permissible limit of OTA value reported by the European Union (5 ng g−1).

A 3×3 visible-light cross-reactive sensor array based on the nanoaggregation of curcumin in different pH and buffers for the multivariate identification and quantification of metal ions

Here, a facilely constructed 3 × 3 visible-light cross reactive sensor array based on nanoaggregation of curcumin (Cur) is proposed for the identification and quantification of metal ions (MIs). Synthesis of nanocurcumin (NCur) was characterized by UV–Vis spectrophotometry, transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR). The average particle size was estimated about 5.21 ± 1.13 nm) n = 50 (. Our sensor array consists of nine receptors with distinct but overlapping specificities for 11 MIs: Al3+, Cd2+, Co2+, Cu2+, Hg2+, Fe2+, Fe3+, Mn2+, Ni2+, Pb2+, and Zn2+. The receptors include the nine solutions of NCur at three buffers of phosphate, ammonium, and tris each at three pH of 7, 8, and 9 (in total 9 receptors). On account of different pH and buffers, NCur-MI binding affinities can be distinguished by monitoring the UV–Vis absorbance changes. These changes are optical fingerprints that can be used to identify each MI. The absorption values in sixteen wavelengths (i.e. 332, 352, 372, 392, 412, 432, 452, 472, 492, 512, 532, 552, 572, 592, 612, and 632 nm) are considered as analytical signals to quantitatively evaluate of the absorbance responses of the sensor array. A color difference map is provided to qualitatively visualize of the colorimetric sensor array responses. Under optimal conditions, the MIs are successfully discriminated in the range of 4–48 μmol L−1. The limit of detections (LODs) values ranged from 0.47 (for Fe3+) to 1.40 μmol L−1 (for Pb2+). Furthermore, two different mixing sets of the MIs are prepared for multivariate multicomponent analysis. Finally, the suggested sensor array is employed to evaluate its practicability in the discrimination of MIs in samples of river water and serum. Moreover, it can identify the MIs in these samples. The sensor array presents a simple, save time, cost-effective, and environmentally friendly method for the identification and quantification of MIs.

Performance of stereolithography and milling in fabricating monolithic zirconia crowns with different finish line designs

Subtractive manufacturing has become the dominant method in fabricating zirconia dental restorations while additive manufacturing is emerging as a potential alternative. The aim of this in vitro study was to investigate the performance of stereolithography (SLA) and milling in fabricating monolithic zirconia crowns with different finish line designs. Full-contour crowns with three finish lines (chamfer, rounded shoulder, knife-edge) were designed and fabricated by SLA and milling. Fabrication accuracy was accessed by 3D deviation analysis and margin quality was characterized under microscopes. The obtained root mean square value was significantly influenced by finish line design (P < 0.05) but not by fabrication method (P＞0.05). However, the color-difference map showed crowns fabricated by SLA and milling had different error distribution in external surfaces. SLA-printed crowns exhibited margins of rounded line angle and without small flaws, although large chippings were found in knife-edged crowns. In milling group, crowns showed margins of sharp line angle and with separate chippings. More and larger margin chippings were found in knife-edged crowns by milling. The results indicate that SLA and milling can fabricate monolithic zirconia crowns of comparable accuracy and knife-edged crowns are prone to large margin chippings by either of the two manufacturing methods.

A paper-based colorimetric sensor array for discrimination of monofloral European honeys based on gold nanoparticles and chemometrics data analysis.

A sensitive and simple nanomaterial based colorimetric sensor array (NBCSA) was developed for discrimination of monofloral honey from various European countries based on three botanical origins as Acacia, Canola and Honeydew. The NBCSA was designed by spotting gold (AuNPs) and silver (AgNPs) nanoparticles synthesized using six different reducing and/or capping agents. The colour intensity of AuNPs represented differential changes when interacting with volatile organic compounds appeared in the headspace of the honey samples. The color difference maps, which are calculated as the difference between color intensity of the sensor before and after exposing to the sample vapors, were used as a fingerprint to discriminate the honey samples based on botanical origin. Classification was achieved utilizing data pre-processing and chemometrics data analysis. Fitting accuracies of 88% and 86% were obtained by partial least squares discriminant analysis and linear discriminant analysis whereas 100% was achieved using support vector machine.

Preliminary study on three digital analysis methods for analyzing the distribution and area of occlusal contacts

Objective To analyze the distribution and area of occlusal contacts of clinical dental model using three kinds of digital analysis methods, to compare the results of these methods and traditional occlusal analysis and to further analyze the characteristics of each digital analysis Methods A set of plaster models of normal subjects was selected. The models were by lab scanner 3shape E4 and the files were exported in a stereolithography file format. In analysis software Geomagic Studio 2013 and Geomagic Qualify 2013, the corresponding results of occlusal contact distribution and occlusal contact area were obtained through three digital analysis methods: 3D color difference map method, cloud analysis method, and articulating paper method. The occlusal contact distribution and occlusal contact area were also obtained by two traditional occlusal analysis methods: interocclusal recording material and scanned articulating paper mark method. A threshold of 100 μm was used to analyze the occlusal contacts and 100 μm was also the thickness of articulating paper used in this study. The results of these five different occlusal analysis methods were evaluated qualitatively and quantitatively. Results The results of occlusal contact distribution obtained by the above five methods were basically consistent. The total occlusal contact area obtained by color difference map point cloud analysis virtual articulating paper silicone interocclusal recording material method and articulating paper mark method were 133.10 mm², 142.08 mm², 128.95 mm², 163.31 mm², and 100.55 mm² respectively. There was little difference between the results of three digital analysis methods. The results of occlusal contact area obtained by the digital methods and the traditional methods were different. Conclusion The three digital analysis methods can provide reliable and accurate analysis results of occlusal contact distribution and occlusal contact area of dental model. The results obtained by these methods can serve as references for the digital occlusal surface design of dental prosthesis and clinical occlusal analysis.

Three-Dimensional Evaluation on Accuracy of Conventional and Milled Gypsum Models and 3D Printed Photopolymer Models.

The aim of this study was to evaluate the accuracy of dental models fabricated by conventional, milling, and three-dimensional (3D) printing methods. A reference model with inlay, single crown, and three-unit fixed dental prostheses (FDP) preparations was prepared. Conventional gypsum models (CON) were manufactured from the conventional method. Digital impressions were obtained by intraoral scanner, which were converted into physical models such as milled gypsum models (MIL), stereolithography (SLA), and digital light processing (DLP) 3D printed photopolymer models (S3P and D3P). Models were extracted as standard triangulated language (STL) data by reference scanner. All STL data were superimposed by 3D analysis software and quantitative and qualitative analysis was performed using root mean square (RMS) values and color difference map. Statistical analyses were performed using the Kruskal–Wallis test and Mann–Whitney U test with Bonferroni’s correction. For full arch, the RMS value of trueness and precision in CON was significantly smaller than in the other groups (p < 0.05/6 = 0.008), and there was no significant difference between S3P and D3P (p > 0.05/6 = 0.008). On the other hand, the RMS value of trueness in CON was significantly smaller than in the other groups for all prepared teeth (p < 0.05/6 = 0.008), and there was no significant difference between MIL and S3P (p > 0.05/6 = 0.008). In conclusion, conventional gypsum models showed better accuracy than digitally milled and 3D printed models.

Influence of inlay preparation design on the trueness of different impression techniques

Statement of problem. Limited data is available on the effect of inlay preparation design on the trueness of digital impressions obtained by intra-oral scanners and conventional impressions. Purpose. The purpose of this study was to evaluate the influence of inlay preparation design on the trueness of different impression techniquesMaterial and methods. Two typodont resin teeth representing maxillary first premolars were prepared for disto-occlusal inlay preparations with two different divergent angels (6° and 12°). The prepared teeth were mounted in two typodont dental models and were used as reference models. Each reference model was scanned using an extra-oral scanner. A total of 40 digital impressions of the reference models were obtained using two different intra-oral scanners (3Shape Trios and Cerec Omnicam). For the conventional impressions, each reference model was duplicated 10 times for each preparation design (n=10) using a stock metal-tray and a vinyl polysiloxane impression material to obtain a total of 20 conventional impressions. Then, all impressions were scanned using the previously used extra-oral scanner. Subsequently, all impressions were poured with modified dental stone, then each cast was scanned 10 times for each preparation design (n=10) using the same extra-oral scanner to obtain a total of 20 working casts. Both reference models and all (STL) files (n=80) were loaded into a 3D reverse engineering software. For the trueness measurement, color difference maps and reports (n=80) were obtained by superimposing the digital data sets of the scans from the two intra-oral scanners onto the reference model, then (3D) deviation analysis was performed with the best-fit algorithm method. By using this method, for each superimposition, the root mean square (RMS) of the amount of deviation at each measurement point was recorded.Results. Two-way ANOVA revealed statistically significant differences between the taper, impression technique, and significant interaction. 12° taper showed statistically significant higher trueness values when compared to 6° taper. As for impression technique, the impression scan and the cast scan were statistically significantly better than the intra-oral scan. However, there was no statistically significant difference either between the impression scan and the cast scan or between the Omnicam and the 3Shape Trios scan.Conclusion. Inlay preparation with 12 degrees axial wall divergence is significantly better than the 6 degrees axial wall divergence, in terms of trueness.Clinical implications. Special care should be considered during capturing the image while using intra-oral scanners for inlay restorations.

Robust Stereoscopic Crosstalk Prediction

We propose a new metric to predict perceived crosstalk using the original images rather than both the original and ghosted images. The proposed metrics are based on color information. First, we extract a disparity map, a color difference map, and a color contrast map from original image pairs. Then, we use those maps to construct two new metrics ( $V_{\mathrm{ dispc}}$ and $V_{\mathrm{ dlogc}}$ ). Metric $V_{\mathrm{ dispc}}$ considers the effect of the disparity map and the color difference map, while $V_{\mathrm{ dlogc}}$ addresses the influence of the color contrast map. The prediction performance is evaluated using various types of stereoscopic crosstalk images. By incorporating $V_{\mathrm{ dispc}}$ and $V_{\mathrm{ dlogc}}$ , the new metric $V_{\mathrm{ pdlc}}$ is proposed to achieve a higher correlation with the perceived subject crosstalk scores. Experimental results show that the new metrics achieve better performance than previous methods, which indicate that color information is one key factor for crosstalk visible prediction. Furthermore, we construct a new data set to evaluate our new metrics.

Trueness and precision of scanning abutment impressions and stone models according to dental CAD/CAM evaluation standards.

PURPOSEThe purpose of the present study was to compare scanning trueness and precision between an abutment impression and a stone model according to dental computer-aided design/computer-aided manufacturing (CAD/CAM) evaluation standards.MATERIALS AND METHODSTo evaluate trueness, the abutment impression and stone model were scanned to obtain the first 3-dimensional (3-D) stereolithography (STL) file. Next, the abutment impression or stone model was removed from the scanner and re-fixed on the table; scanning was then repeated so that 11 files were obtained for each scan type. To evaluate precision, the abutment impression or stone model was scanned to obtain the first 3-D STL file. Without moving it, scanning was performed 10 more times, so that 11 files were obtained for each scan type. By superimposing the first scanned STL file onto the other STL files one by one, 10 color-difference maps and reports were obtained; i.e., 10 experimental scans per type. The independent t-test was used to compare root mean square (RMS) data between the groups (α=.05).RESULTSThe RMS±SD values of scanning trueness of the abutment impression and stone model were 22.4±4.4 and 17.4±3.5 µm, respectively (P<.012). The RMS±SD values of scanning precision of the abutment impression and stone model were 16.4±2.9 and 14.6±1.6 µm, respectively (P=.108).CONCLUSIONThere was a significant difference in scanning trueness between the abutment impression and stone model, as evaluated according to dental CAD/CAM standards. However, all scans showed high trueness and precision.

Chemical nose for discrimination of opioids based on unmodified gold nanoparticles

Considering the need for detection of opioids, a colorimetric sensor array based on unmodified gold nanoparticles (AuNPs) was developed for the first time in order to sensitively detect and identify multiple structurally similar opioids including morphine, codeine, oxycodone, noroxycodone, thebaine, tramadol and methadone in aqueous media. Size dependency of assembly process encouraged us to employ AuNPs with four distinct particle sizes as sensing elements and visual differentiation tools to construct a colorimetric nanoarray. The target opioids seem to act as “molecular bridges”, shortening the interparticle distance and inducing the aggregation of AuNPs. This aggregation produces changes in both the color and UV–vis spectra of AuNPs generating a visual molecular fingerprint of each analyte. The cumulative array responses were differentiated by principal component analysis (PCA) and hierarchical cluster analysis (HCA) with 100% classification accuracy demonstrating the versatility of this simple nanoarray platform. Furthermore, color difference maps were created to provide a visual tool for classifications and semi-quantitative analysis without exploiting any statistical techniques. Finally, we demonstrated the ability of the constructed array to identify the various opioids in urine sample. The obtained results suggest that the proposed colorimetric nanoarray has promising perspective in the clinical toxicology and forensic cases for the on-spot detection of illegal drugs.