Factors influencing the accuracy of intraoral impression in implant restoration / 口腔疾病防治

@#Due to advances in digital technology, intraoral impressions have been increasingly used to fabricate implant restorations because of its simplicity, high efficiency, comfortableness and convenience. In clinical practice, the accuracy of intraoral impressions depends on various factors, including scanner technique, status of dentition and implants, auxiliary devices, materials and environment, which might influence its accuracy and limit its application. When applied to patients missing more teeth, its accuracy may be insufficient. It is suggested that intraoral impressions be used cautiously when there are multiple and far apart implants and that the scan body not be tightened excessively and that maintain appropriate environmental conditions. In this article, we have reviewed recent relevant literature and the factors affecting the accuracy of intraoral impressions for implant restoration.

Accuracy of photogrammetric technologies for the scanning of dental models: A systematic review / Precisión de las tecnologías fotogramétricas para el escaneo de modelos dentales: Una revisión sistemática

Background:Traditional dental scanners require a heavy investment, representing a high barrier of entry into digital dentistry. Photogrammetric-based scanners may represent an affordable cost-effective alternative to traditional dental scanners used for the digitalization of plaster models. Photogrammetry is the science of extracting 3D information from photographs. The process involves taking overlapping photographs of an object or space and converting them into 2D or 3D digital models. Objective:This review aimedto identify and appraise the reported accuracy of photogrammetric-generated digital dental models.Materials and methods:A search strategy was applied in 3 databases (Medline, Web of Science and Scopus), from Feb 1 2021 to Dec 1 2021, the search was limited to articles in English published in the last 5 years about studies evaluating the dimensional accuracy of 3-dimensional digital models acquired by the scanning of plaster models with photogrammetric technologies.Results:Two independent reviewers screened 75 records on basis of titles and abstracts for assessment against the inclusion criteria for the review, 4 articles were deemed eligible, the risk of bias for the selected articles was measured, data extraction was performed by only one author.Conclusion:With today's technology, based on the four studies evaluated, we conclude that photogrammetric-generated digital models while lacking accuracy for incorporation into the treatment flow, in the future it could be used for diagnostic, planning, and achieving.

Antecedentes:Los escáneres dentales tradicionales requieren una gran inversión, lo que representa una gran barrera de entrada a la odontología digital. Los escáneres basados en fotogrametría pueden representar una alternativa asequible y rentable a los escáneres dentales tradicionales utilizados para la digitalización de modelos de yeso. La fotogrametría es la ciencia de extraer información 3D de fotografías. El proceso implica tomar fotografías superpuestas de un objeto o espacio y convertirlas en modelos digitales 2D o 3D.Objetivo:esta revisión tuvo como objetivo identificar y evaluar la precisión informada de los modelos dentales digitales generados fotogramétricamente.Materiales y métodos:Se aplicó una estrategia de búsqueda en 3 bases de datos (Medline, Web of Science y Scopus), del 1 de febrero de 2021 al 1 de diciembre de 2021, la búsqueda se limitó a artículos en inglés publicados en los últimos 5 años sobre estudios que evalúan la dimensión precisión de modelos digitales tridimensionales adquirida por el escaneo de modelos de yeso con tecnologías fotogramétricas.Resultados:dos revisores independientes examinaron 75 registros sobre la base de títulos y resúmenes para evaluarlos según los criterios de inclusión para la revisión, 4 artículos se consideraron elegibles, se midió el riesgo de sesgo de los artículos seleccionados, la extracción de datos fue realizada por un solo autor.Conclusión:con la tecnología actual, con base en los cuatro estudios evaluados, concluimos que los modelos digitales generados por fotogrametría si bien carecen de precisión para incorporarlos al flujo de tratamiento, en el futuro podrían usarse para el diagnóstico, la planificación y el logro.

Impact of different scan strategies and implant angulation on impression accuracy of full arch multiple implant: an in vitro study / Impacto de diferentes estratégias de escaneamento e angulação dos implantes na acurácia da moldagem de implantes múltiplos em arco completo: um estudo in vitro

Objective: to evaluate the impact of three different scan strategies and implant angulation on impression accuracy of an intraoral scanner for full-arch multiple implant scan. Material and Method: A maxillary edentulous model with six implant analogs served as a reference model. The four anterior analogs were positioned parallel to each other, the distal right and the distal left was placed with an angulation of 15o and 20o, respectively. Thirty impression were performed using an intraoral scanner (CEREC Primescan). The master cast was digitalized with an industrial reference scanner (ATOS Core 80). All scans were converted to standard tessellation language (STL), superimposed on the reference scan with a 3d inspection software (GOM Inspect Professional 2019) and then analyzed. Results: All linear distances presented equivalence [p<0.01] to those found on the reference scan for all scan strategies. All scan strategies presented a tendency of negative means for linear distances except for d4 in strategy C. All angular distances did not present equivalence [p=0.05] to those found on the reference scan. Significant 3D deviations [p<0.05] were found between strategy B (0.02 ± 0.01) and C (0.05 ± 0.04) for d1. In all others linear and angular distances no statistically significant difference was found between strategies A, B and C. Conclusions: There was no statistically significant difference between strategies A, B and C except for d1 in strategy B and C; Implant angulation did not affect the accuracy of the CEREC Primescan IOS (AU)

Objetivo: avaliar o impacto de três diferentes estratégias de escaneamento e angulação do implante na acurácia da moldagem de um scanner intraoral na moldagem de múltiplos implantes em arco completo. Material e Métodos: Um modelo edêntulo de maxila contendo seis análogos de implante serviu como modelo de referência. Os quatro análogos anteriores foram posicionados paralelos entre si, o distal direito e o distal esquerdo foram posicionados com angulação de 15o e 20o, respectivamente. Trinta moldagens foram realizadas usando um scanner intraoral (CEREC Primescan). O modelo mestre foi digitalizado com um scanner de referência industrial (ATOS Core 80). Todas as escaneamentos foram convertidas para a linguagem de mosaico padrão (STL), sobrepostas ao escaneamento de referência com um software de inspeção 3D (GOM Inspect Professional 2019) e, em seguida, analisadas. Resultados: Todas as distâncias lineares apresentaram equivalência [p <0,01] àquelas encontradas na escaneamento de referência para todas as estratégias. Todas as estratégias de escaneamento apresentaram tendência de médias negativas para distâncias lineares, exceto para d4 na estratégia C. Todas as distâncias angulares não apresentaram equivalência [p = 0,05] às encontradas no escaneamento de referência. Desvios 3D significativos [p <0,05] foram encontrados entre a estratégia B (0,02 ± 0,01) e C (0,05 ± 0,04) para d1. Em todas as outras distâncias lineares e angulares, nenhuma diferença estatisticamente significativa foi encontrada entre as estratégias A, B e C. Conclusões: Não houve diferença estatisticamente significante entre as estratégias A, B e C, exceto para d1 na estratégia B e C; A angulação do implante não afetou a precisão do CEREC Primescan. (AU)

Accuracy of Intraoral Scanners and Conventional pressions in Full-Arches: A Systematic Review

ABSTRACT: The aim of this study was to evaluate intraoral scanners accuracy in full-arches, comparing them with conventional impressions. A scientific research performed in MEDLINE, EBSCOhost, and SciELO databases was conducted to analyze articles published between 2015 and 2020. Clinical and in vitro studies that evaluated accuracy (precision and trueness) from intraoral scanners and conventional impressions in full-arches were included. Two tests were applied to evaluate the methodological bias from the studies. Out of the 191 articles found, seven of them were selected for a qualitative analysis. In clinical studies,intraoral scanners CEREC Omnicam and 3Shape TRIOS Colorhad the highest precision compared to conventional irreversible hydrocolloid impressions. In in vitro studies, conventional polyvinyl siloxane impressions showed the highest accuracy, followed by intraoral scanners Cadent iTero and CEREC Omnicam, while irreversible hydrocolloid impressions showed the lowest accuracy. Digital intraoral impression systems do not show superior accuracycompared to highly accurate conventional impression techniques. However, they provide excellent clinical results and both methods are clinically accepted.

RESUMEN: El objetivo de este estudio fue evaluar la exactitud de escáneres intraorales en impresiones digitales de arco completo en comparación con las impresiones convencionales. Se realizó una revisión sistemática en las bases de datos MEDLINE, EBSCOhost y SciELO para analizar artículos publicados entre los años 2015 y 2020. Se incluyeron estudios clínicos e in vitro que evaluaran exactitud (precisión y/o veracidad) de escáneres intraorales impresiones convencionales en arcos completos. Dos pautas se aplicaron para evaluar el riesgo de sesgo de los estudios. De 191 artículos encontrados, 7 fueron seleccionados para un análisis cualitativo. En los estudios clínicos, los escáneres intraorales CEREC Omnicam y 3Shape TRIOS Color presentaron la mayor precisiónen comparación con las impresiones convencionales de hidrocoloide irreversible. En los estudios in vitro, las impresiones de polivinil siloxano presentaron la mayor exactitud seguido por los escáneres intraorales CadentiTero y CEREC Omnicam, mientras quelas impresiones de hidrocoloide irreversible presentaron la menor exactitud. Los sistemas de impresión digital intraoral no mostraron tener una exactitud superior comparados con las técnicas de impresión convencional de gran exactitud. Sin embargo, proveen excelentes resultados clínicos y ambos métodos son clínicamente aceptables.

Evaluation of the influence of the impression technique, scanning direction and type of scanner on the accuracy of the final model / Avaliação da influência da técnica de impressão, direção de digitalização e tipo de scanner na precisão do modelo final

Objective: The purpose of this study is to evaluate the influence of the type of scanner and scanning direction on the accuracy of the final cast. Material and Methods: A partial master cast was used as a reference. A total of 128 scans were obtained and divided into two groups: the conventional method and the digital method. The digital group was divided into three groups: TRIOS 3, Omnicam and CS 3600. Each of these groups was subdivided according to the scanning direction, and each scan was overlaid on the digital reference cast to measure the trueness and precision of the procedures. Results: The overall precision values for the type of impression were 59.89 ± 13.08 µm for conventional and 13.42 ± 4.28 µm for digital; the values for trueness were 49.37 ± 19.13 µm for conventional and 53.53 ± 4.97 µm for digital; the scanning direction trueness values were 53.05 ± 4.36 µm for continuous and 54.03 ± 5.52 µm for segmented; and the precision values were 14.18 ± 4.67 µm for continuous and 12.67 ± 3.75 µm for segmented (p> 0.05). For the scanner type, the trueness values were 50.06 ± 2.65 µm for Trios 3, 57.45 ± 4.63 µm for Omnicam, and 52.57 ± 4.65 µm for Carestream; and those for precision were 11.7 ± 2.07 µm for Trios 3, 10.09 ± 2.24 µm for Omnicam, and 18.49 ± 2.42 µm for Carestream (p <0.05). Conclusions: The digital impression method is the most favorable method regarding precision; in terms of trueness, there are no differences between the types of impressions. (AU)

Objetivo: O objetivo deste estudo é avaliar a influência do tipo de técnica de moldagem, tipo de escâner intraoral e direção do escaneamento na precisão do modelo final. Material e Métodos: Um modelo parcial mestre foi usado como referência. Um total de 128 escaneamentos foi obtido e dividido em dois grupos: o método convencional (n = 32) e o método digital (n = 96). O grupo digital foi dividido em três grupos: TRIOS 3 (n = 32), Omnicam (n = 32) e CS 3600 (n = 32). Cada um desses grupos foi subdividido de acordo com a direção do escaneamento (n = 16), e cada escaneamento foi sobreposto ao modelo de referência digital para medir a veracidade e precisão dos procedimentos. Resultados: Os valores gerais de precisão para o tipo de impressão foram 59,89 ± 13,08 µm para convencional e 13,42 ± 4,28 µm para digital; os valores de veracidade foram 49,37 ± 19,13 µm para convencional e 53,53 ± 4,97 µm para digital; os valores de veracidade para a direção de digitalização foram 53,05 ± 4,36 µm para contínua e 54,03 ± 5,52 µm para segmentada; e os valores de precisão foram 14,18 ± 4,67 µm para contínua e 12,67 ± 3,75 µm para segmentada (p> 0,05). Para o tipo de scanner, os valores de veracidade foram 50,06 ± 2,65 µm para Trios 3, 57,45 ± 4,63 µm para Omnicam e 52,57 ± 4,65 µm para Carestream; e os de precisão foram 11,7 ± 2,07 µm para Trios 3, 10,09 ± 2,24 µm para Omnicam e 18,49 ± 2,42 µm para Carestream (p <0,05). Conclusões: O método de moldagem digital é o método mais favorável em relação à precisão; em termos de veracidade, não há diferenças entre os tipos de impressão (AU)

Trueness and precision of the reproduction of dental casts by the conventional, milling and 3D printing techniques / Fidelidade e precisão de modelos de trabalho reproduzidos pelas técnicas convencional, de fresagem e de impressão 3D

Objective: To compare the reproduction trueness and precision of dental casts made by the conventional, milling and 3D printing techniques. Material and Methods: From an upper right side half-arch reference model (RM), 72 models were obtained and divided into three groups: conventional (CM), milled (MM) and printed (PM). All models were scanned and converted into standard tessellation language (.STL) files. The files were superimposed using 3D analysis software, and statistical analysis was performed using the root mean square (RMS) values obtained. The Shapiro-Wilk test was used to assess normality, and the Kruskal-Wallis test was used to compare groups (ρ < ⍺; ⍺ = 0.05). The Mann-Whitney U test was used for multiple comparisons among groups (ρ < ਕ; ਕ = 0.017). Results: There were significant differences in trueness (ρ = 0.000; ρ <0.001) and precision (ρ = 0.000; ρ < 0.001) among the three dental cast groups. Regarding trueness, CM presented better results, followed by MM and PM. Regarding precision, MM showed better results, followed by PM and CM, which did not show significant differences. Conclusions: For dental cast reproduction the conventional technique has the best trueness and the milling technique has the best precision.(AU)

Objetivo: Comparar a fidelidade e precisão de reprodução de modelos de trabalho pelas técnicas convencional, de fresagem e de impressão 3D. Material e Métodos: A partir de um modelo de referência (MR) de uma hemi-arcada superior direita, foram obtidos 72 modelos divididos em três grupos: convencionais (MC), fresados (MF) e impressos (MI). Todos foram digitalizados e convertidos sob a forma de ficheiros .STL (standard tesselation language). Os ficheiros foram sobrepostos utilizando um software de análise 3D, e através dos valores RMS (raiz do valor quadrático médio) obtidos foi realizada a análise estatística. Para avaliação da normalidade foi utilizado o teste Shapiro Wilk e para a comparação entre grupos foi utilizado o teste Kruskal-Wallis (ρ < ⍺; ⍺ = 0.05). Para as comparações múltiplas entre grupos, foi utilizado o teste U de Mann-Whitney (ρ < ਕ; ਕ = 0.017). Resultados:Existem diferenças significativas de fidelidade (ρ = 0.000; ρ <0.001) e precisão (ρ = 0.000; ρ < 0.001) entre os três grupos. Em relação à fidelidade, MC apresentou melhores resultados, seguido por MF e MI. Em relação à precisão, MF apresentou melhores resultados, seguido por MI e MC, que não apresentaram diferenças significativas entre si. Conclusão: Para reprodução de modelos de trabalho, a técnica convencional é a que apresenta maior fidelidade e a técnica de fresagem a que apresenta maior precisão.(AU)

Influence of trueness for local finish lines of a full crown preparation on that of complete finish line / 北京大学学报(医学版)

OBJECTIVE@#To investigate the factors affecting the trueness of finish lines of full crown preparations in digital impressions.@*METHODS@#A full crown preparation of the right maxillary molar was prepared on the standard resin dentition model, the trueness of the finish lines, the full crown preparation in the whole dentition and the isolated full crown preparation were measured respectively. Detection of scanning trueness of the finish lines of the full crown preparation in the whole dentition: (1) Using Imetric scanner to scan the full crown preparation, obtaining STL (Stereo lithographic) format data as the reference true value; (2) Using CEREC Omnicam oral scanner and 3Shape TRIOS oral scanner to scan the full crown preparation, obtaining all the STL format data, import Geomagic Studio 2013 software, extraction of images and data of the complete finish lines or local finish lines (mesial, distal, buccal, lingual) of the full crown preparation, then using the data to 3D Compare Analysis with the reference true value, outputting RMS (root mean square) values which could evaluate the scanning trueness, the lower RMS value was, the lower the trueness was. The detection of scanning trueness of the finish lines of the isolated full crown preparation: (1) the anterior and posterior adjacent teeth of the preparation were removed to establish the model of the isolated full crown preparation; (2) CEREC Omnicam oral scanner and 3Shape TRIOS oral scanner were used to scan the isolated preparations, and each group was repeated 6 times. Data collection and analysis were the same as the first part, that is, detection of scanning trueness of finish lines of the full crown preparation in the whole dentition.@*RESULTS@#In the whole dentition, (1) the RMS value [(44±7) μm] of CEREC Omnicam oral scanner scanning complete finish lines was greater than that of 3Shape TRIOS oral scanner [(35±6) μm](P < 0.05). (2) the RMS values of the mesial [(45±9) μm], buccal [(38±3) μm] and lingual [(40±3) μm] finish lines in CEREC Omnicam oral scanner scanning were all lower than that in distal [(63±7) μm](P < 0.05), and the RMS values in mesial were higher than that in buccal and lingual (P>0.05). The RMS values of 3Shape TRIOS oral scanner scanning mesial and distal finish lines were significantly higher than those of the buccal and lingual side (P>0.05), in which:(45±8) μm in mesial, (50±10) μm in the distal, (33±8) μm in the buccal and (33±6) μm in the lingual side. The RMS value of CEREC Omnicam oral scanner scanning distal finish line was greater than that of 3Shape TRIOS oral scanner (P < 0.05). Without adjacent teeth, (1) the RMS values of the complete finish lines of CEREC Omnicam oral scanner and 3 Shape TRIOS oral scanner were significantly reduced (P < 0.05), including CEREC Omnicam oral scanner (34±3) μm and 3 Shape TRIOS oral scanner (26±4) μm; (2) the RMS values of the buccal and lingual finish lines of CEREC Omnicam oral scanner and 3Shape TRIOS oral scanner showed no significant changes (P>0.05), among which, CEREC Omnicam oral scanner buccal (44±7) μm, lingual (43±3) μm, 3Shape TRIOS oral scanner buccal (29±5) μm, lingual (40±7) μm. The RMS values of CEREC Omnicam oral scanner and 3Shape TRIOS oral scanner were significantly reduced and there was no significant difference between them (P>0.05). CEREC Omnicam oral scanner (32±8) μm and 3Shape TRIOS oral scanner (32±6) μm. The RMS values of the distal finish lines of CEREC Omnicam oral scanner and 3 Shape TRIOS oral scanner also decreased significantly (P < 0.05), and CEREC Omnicam oral scanner (38±3) μm decreased more significantly, similar to 3Shape TRIOS oral scanner (36±1) μm, P>0.05.@*CONCLUSION@#When adjacent teeth exist in the full crown preparation, the mesial and distal parts of the finish line will be blocked by adjacent teeth, which will affect the trueness of the local finish line, and ultimately reduce the trueness of the complete finish line.

Research progress on the precision of digital impressions used in implant-supported fixed prostheses / 口腔疾病防治

@#Since the digital impression technique has already been widely used in dental therapy, it has grown into a popular option among implant practitioners. The advantages of the digital impression technique are as follows: better experience for patients during the treatment; less chair-side time consumption; and reliability in making the precise impression. Thus, we reviewed the relevant factors that impact the precision of the digital impression technique and introduced its influence mechanism through an evidence-based method that was based on analyzing in vitro and in vivo literature published within the previous 5 years, with a focus on such considerations as relevant factors to dentists, digital impression systems, patients, and the environment. A review of the literature showed that the main factors that have a large influence on impression precision are imaging techniques and the software for the impression system. However, due to the development of impression systems that are restricted at scientific and technological levels, impression precision is affected by multiple factors, such as scanning techniques, dentist operation proficiency, material and contours of scanbodies, patient conditions, and ambient light. Dentists are advised to scientifically choose the impression system, limit ambient light and adopt direct techniques that could enhance impression precision. In the future, the development of impression systems could reduce the systematic errors, decrease the operating complexity of dentists, and improve impression precision.

Accuracy of casts produced from conventional and digital workflows: A qualitative and quantitative analyses

PURPOSE: Comparing the accuracy of casts produced from digital workflow to that of casts produced from conventional techniques. MATERIALS AND METHODS: Whole arch alginate (ALG) and polyvinyl siloxane (PVS) impressions were taken with stock trays and custom trays, respectively. The ALG impressions were poured with type III dental stone, while the PVS impressions were poured with type IV dental stone. For the digital workflow, IOS impressions were taken and physical casts were produced by 3D printing. In addition, 3D printed casts were produced from images obtained from a laboratory scanner (LS). For each technique, a total of 10 casts were produced. The accuracies of the whole arch and separated teeth were virtually quantified. RESULTS: Whole arch cast accuracy was more superior for PVS followed by LS, ALG, and IOS. The PVS and ALG groups were inferior in the areas more susceptible to impression material distortion, such as fossae and undercut regions. The LS casts appeared to have generalized errors of minor magnitude influencing primarily the posterior teeth. The IOS casts were considerably more affected at the posterior region. On the contrary, the IOS and LS casts were more superior for single tooth accuracy followed by PVS and ALG. CONCLUSION: For whole arch accuracy, casts produced from IOS were inferior to those produced from PVS and ALG. The inferior outcome of IOS appears to be related to the span of scanning. For single tooth accuracy, IOS showed superior accuracy compared to conventional impressions.

A new method to measure the accuracy of intraoral scanners along the complete dental arch: A pilot study

PURPOSE: The purpose of this study is to assess the accuracy of three intraoral scanners along the complete dental arch and evaluate the feasibility of the assessment methodology for further in vivo analysis.MATERIALS AND METHODS: A specific measurement pattern was fabricated and measured using a coordinate measuring machine for the assessment of control distances and angles. Afterwards, the pattern was placed and fixed in replica of an upper jaw for their subsequent scans (10 times) using 3 intraoral scanners, namely iTero Element1, Trios 3, and True Definition. 4 reference distances and 5 angles were measured and compared with the controls. Trueness and precision were assessed for each IOS: trueness, as the deviation of the measures from the control ones, while precision, as the dispersion of measurements in each reference parameter. These measurements were carried out using software for analyzing 3-dimensional data. Data analysis software was used for statistical and measurements analysis (α=.05).RESULTS: Significant differences (P<.05) were found depending on the intraoral scanner used. Best trueness values were achieved with iTero Element1 (mean from 10 ± 7 µm to 91 ± 63 µm) while the worst values were obtained with Trios3 (mean from 42 ± 23 µm to 174 ± 77 µm). Trueness analysis in angle measurements, as well as precision analysis, did not show conclusive results.CONCLUSION: iTero Element1 was more accurate than the current versions of Trios3 and True Definition. Importantly, the proposed methodology is considered reliable for analyzing accuracy in any dental arch length and valid for assessing both trueness and precision in an in vivo study.

Investigation on the trueness and precision of routine clinical biochemistry tests in the third-grade class-A hospitals of Chongqing City / 临床检验杂志

Objective@#To investigate the trueness and precision of routine clinical biochemistry tests in the third-grade class-A hospitals of Chongqing city. @*Methods@#The fresh frozen serum samples were assigned the target values with reference methods, and then allocated to the clinical laboratories of the third-grade class-A hospitals in Chongqing city for testing. The trueness and precision were analyzed and evaluated. @*Results@#The pass rates of trueness of creatinine (Cr), total protein (TP), total bilirubin (T-Bil), uric acid (UA) and glucose (Glu) in 33 clinical laboratories were below 50%. The pass rate of trueness of UA (33%) in the closed detection system was lower than that in the opening detection system (79%, P=0.033). In the opening detection system, the pass rate of trueness of Cr in the mode with the same brand of reagents and calibration materials was higher than that with different brands (P=0.014). The precisions of level 1 of T-Bil and Urea in the closed detection system were better than that in the opening detection system (P=0.043 for T-Bil; P=0.031 for Urea). @*Conclusion@#The trueness of clinical biochemistry tests in the third-grade class-A hospitals of Chongqing city needs to be further improved. There is no significant difference in trueness and precision between the opening detection system and the closed detection system, even the performance of some tests in the opening detection system is better than that in the closed detection system.

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

PURPOSE: The 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 METHODS: To 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). RESULTS: The 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). CONCLUSION: There 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.

Comparison of the accuracy of digital impressions and traditional impressions: Systematic review / 대한치과보철학회지

PURPOSE: This study systematically examines literatures on the suitability of prostheses and accuracy of obtained impressions to see if digital impressions using intraoral scanners can replace traditional impressions. MATERIALS AND METHODS: A MEDLINE/PubMed search and manual search was performed for studies written in English about accuracy of digital impression published in dental journals from August 1, 1997, to July 31, 2017. Depending on criteria, the data for the selected articles were independently organized into standardized spreadsheets by 2 reviewers. RESULTS: Among the total 35 studies met the inclusion criteria, there were 26 studies comparing the suitability of prostheses, and 9 studies comparing the accuracy of impressions through scan data without prostheses. Most studies used prostheses to compare the accuracy of impression techniques. CONCLUSION: This review suggests that making single crown or mesio-distally short prostheses with digital impressions is clinically reliable in natural teeth. However, there is still a limit to making mesio-distally long prostheses with digital impressions from the lack of related studies. Digital impression cannot fully replace traditional impressions in implant prostheses yet.

Pragmatic Approach of Verification of Examination Procedures in Clinical Laboratory for Imprecision,Trueness and Diagnostic Accuracy / 现代检验医学杂志

Objective To propose a practice model for implementing procedures employed for the verification of validated ex-amination procedures already used for at least 2 years in their laboratory,in agreement with the ISO 15189 requirement at the Section 5.5.1.2.Methods In order to identify the operative procedure to be used,approved documents were identified, together with the definition of performance characteristics to be evaluated for the different methods;the examination proce-dures used in laboratory were analyzed and checked for performance specifications reported by manufacturers.Then,opera-tive flow charts were identified to compare the laboratory performance characteristics with those declared by manufacturers. Results The choice of performance characteristics for verification was based on approved documents used as guidance,and the specific purpose tests undertaken,a consideration being made of:imprecision and trueness for quantitative methods;diag-nostic accuracy for qualitative methods;imprecision together with diagnostic accuracy for semi-quantitative methods.Conclu-sion The described approach,balancing technological possibilities,risks and costs and assuring the compliance of the funda-mental component of result accuracy,appears promising as an easily applicable and flexible procedure helping laboratories to comply with the ISO 15189 requirements.

Investigations on the effect of measuring value transfer for human serum samples assigned by the reference laboratory network / 临床检验杂志

Objective To investigate the effect of measuring value transfer for human serum samples assigned by the reference laboratory network on improving the trueness of seven enzyme activities in clinical laboratories,such as ALT,AST,GGT,LDH,CK,AMY and ALP.Methods Depending on the medical imtitutions at all levels contacted by 5 reference laboratories in North China,South China,East China and Southwest China,the corresponding clinical laboratory measuring value transfer/traceability network was established.The frozen human serum samples with good interehangeability and standard material characteristics,including calibrator,sample 1 and sample 2,were provided by Beijing Aerospace General Hospital,and were assigned by 5 reference labotatories in four regiom.These samples were sent to 48 clinical laboratories.These clinical laboratories measured sample 1 and sample 2 according to their standard operating procedures,and then measured.the two samples again after adjusting their measurement system by using the supplied calibrator.The changes of trueness of detection results in these laboratories were evaluated according to the WS/T 403-2012 standard,and the changes of consistency for ALT and AST before and after measuring value tramfer were investigated.Results The results of AMY,ALP,GGT,CK and LDH calibrator,sample 1 and sample 2 assigned by the established network were 138.7 U/L,278.5 U/L and 68.3 U/L,265.3 U/L,94.5 U/L and 134.4 U/L,195.8 U/L,89.0 U/L and 158.9 U/L,393.7 U/L,260.0 U/L and 645.3 U/L,and 302.0 U/L,250.0 U/L and 452.7 U/L,respectively.The percentages of sample 1 and sample 2 which met the bias requirements of the WS/T 403-2012 standard before measuring value transfer for AMY,ALP and GGT were 65.9％ and 61.0％,76.6％ and 78.7％,and 66.7％ and 70.8％,respectively,while after measuring value transfer,they were 89.2％ and 83.8％,86.7％ and 80.0％,and 85.4％ and 91.7％,respectively.The percentages of sample 2 which met the bias requirements of the WS/T 403-2012 standard before measuring value transfer for CK and LDH were 64.6％ and 58.3％,respectively,while after measuring value trander,they were 93.5％ and 84.8％,respectively.The coefficients of variation (consistency) of sample 1 and sample 2 for ALT and AST before measuring value tramfer were 12.9％ and 11.3％,and 10.2％ and 8.9％,respectively,while after measuring value transfer,they were 9.3％ and 8.2％,and 5.6％ and 5.9％,respectively.Conclusion The calibration of routine measurement systems based on the measuring value transfer for human serum samples assigned by the reference laboratory network may improve the comparability of 7 enzyme actvities measurement results in chnical laboratories at all levels obviously,which deserves to be further spread.

Performance verification of precision, trueness, and accuracy of self-developed detection system in ;clinical chemistry / 中华检验医学杂志

Objective To investigate the precision, trueness, and accuracy of self-developed detection system in clinical chemistry.Methods This was a methodological evaluation.Take serum creatine kinase( CK) for instance, 6 serum sampleswith different leves ( on the upper or lower limit of the reference range or close to the medicine decide levels ( MDLs) , were collected for within-run precision( repeatability) and within-laboratory precision ( intermediate precision ) experiments.5 proficiency testing ( PT ) samples, 5 samples assigned value by reference method, and 40 fresh-frozen serums were measured and compared with reference method for trueness verification.Drawing method evaluation decision chart, calculating total errors and sigma level evaluation experiment based on the CV, bias, and allowed total errors(TEa)were used to evaluate the accuracy performance.The precision, trueness, and accuracy were compared with the quality indicators.Results The within-run precision and within-laboratory precision were less than the highest requirement of Chinese industrial standard.The mean bias was -8.96%, didn′t reachthe required standard (5.5%).After taking corrective actions, all samples but one ( -5.8%) met the required standard. Compared with the reference method, the mean bias on the MDLs was less than TEa.The performance points of the method evaluation decision chart indicated excellence performance.The total errors on MDLs were 14.2%, 10.4% and 7.6%, less than 15%.The sigma levels on MDLs were 5.9, 7.5 and 15, also achieved excellent level. Conclusions The precision, trueness, and accuracy performance of CK measured by self-developed detection system achieved excellent level of the Chinese industry standard, and the same results were found from different evaluation methods.

Trueness Controls of Clinical Laboratory to Assess Bias / 现代检验医学杂志

Precision controls monitor assay random error (reproducibility),accuracy controls assess total error,both random error and systematic error,and trueness (bias)of an assay represents systematic error.A trueness control should be metro-logical traceable,ideally with a target value determined by use of a reference material or a reference method,without metro-logical traceable to a reference measurement system,patient test results for the same patient from different laboratories may not be comparable.A trueness control should be commutable and its analytical response to a reference method and a routine field method should be equivalent to that of a patient sample.And trueness control values should generally be set at medical decision levels and be prepared by the providers of reference materials and manufactured in the same fashion as a calibrator.

Comparative analysis on reproducibility among 5 intraoral scanners: sectional analysis according to restoration type and preparation outline form

PURPOSE: The trueness and precision of acquired images of intraoral digital scanners could be influenced by restoration type, preparation outline form, scanning technology and the application of power. The aim of this study is to perform the comparative evaluation of the 3-dimensional reproducibility of intraoral scanners (IOSs). MATERIALS AND METHODS: The phantom containing five prepared teeth was scanned by the reference scanner (Dental Wings) and 5 test IOSs (E4D dentist, Fastscan, iTero, Trios and Zfx Intrascan). The acquired images of the scanner groups were compared with the image from the reference scanner (trueness) and within each scanner groups (precision). Statistical analysis was performed using independent two-samples t-test and analysis of variance (α=.05). RESULTS: The average deviations of trueness and precision of Fastscan, iTero and Trios were significantly lower than the other scanners. According to the restoration type, significantly higher trueness was observed in crown and inlay than in bridge. However, no significant difference was observed among four sites of preparation outline form. If compared by the characteristics of IOS, high trueness was observed in the group adopting the active triangulation and using powder. However, there was no significant difference between the still image acquisition and video acquisition groups. CONCLUSION: Except for two intraoral scanners, Fastscan, iTero and Trios displayed comparable levels of trueness and precision values in tested phantom model. Difference in trueness was observed depending on the restoration type, the preparation outline form and characteristics of IOS, which should be taken into consideration when the intraoral scanning data are utilized.

Evaluación de los parámetros de desempeño de un contador hematológico / Evaluation of performance parameters of an automated hematology analyzer / Avaliação dos parâmetros de desempenho de um analisador da hematologia

El primer paso para obtener seguridad en los resultados emitidos por el laboratorio clínico es confirmar que los procedimientos de medida utilizados tienen un desempeño analítico aceptable. Para conseguirlo se verificó el contador hematológico Beckman Coulter LH 750 de acuerdo con las especificaciones del fabricante y con los requisitos de calidad de este laboratorio. Los parámetros de desempeño evaluados, tanto en modo manual como automático, fueron: porcentaje de arrastre, según protocolo CLSI H26-A2, precisión en condiciones de repetibilidad, precisión en condiciones de precisión intermedia y veracidad, según protocolo CLSI EP15-A2 utilizando controles BIO-RAD, intervalo de medición, según protocolo CLSI EP6-A, límite de cuantificación, según protocolo CLSI EP17-A2 e intervalos de referencia, según protocolo CLSI EP28-A3C. Los datos se analizaron mediante LinChecker y GraphPad 5. En los ensayos realizados se cumplió con las especificaciones estipuladas por el fabricante, como así también con el requisito de calidad de este laboratorio que es variabilidad biológica mínima. También se verificaron los intervalos de referencia para individuos adultos. De esta manera, se logró realizar la verificación del contador hematológico, evidenciando que los parámetros analíticos evaluados tienen un desempeño aceptable.

The first step for safety in the results issued by the clinical laboratory is to confirm that all analytical measurement procedures have shown an acceptable analytical performance. A quality performance evaluation of automated hematology analyzer Beckman Coulter LH 750 was performed according to the quality requirements of our laboratory and manufacturer's specifications. The performance parameters evaluated by both manual and automatic mode were: carryover according to CLSI H26-A2 protocol; repeatability, intermediate precision and trueness according to CLSI EP15-A2 protocol and using BIO-RAD controls; linearity according to CLSI EP6-A protocol; quantification limits according to CLSI EP17-A2 protocol; and reference intervals according to CLSI EP28-A3C protocol. Data were analyzed using LinChecker and GraphPad5 programs. The tests performed complied with the requirements stipulated by the manufacturer and the quality requirements of our laboratory like minimal biological variability. Reference intervals for adult individuals were also checked. Consequently, performance evaluation of the automated hematology analyzer showed that the assessed laboratory parameters have acceptable performance.

O primeiro passo para obter segurança nos resultados emitidos pelo laboratório clínico é confirmar que os processos de medição utilizados tenham um desempenho analítico aceitável. Para obtê-los foi verificado o analisador hematológico Beckman Coulter LH 750 de acordo com as especificações do fabricante e os requisitos de qualidade deste laboratório. Os parâmetros de desempenho avaliados, tanto em modo manual quanto automático, foram: percentual de arrastamento, de acordo com o protocolo CLSI H26-A2, em condições de repetitibidade, precisão em condições de precisão intermediária e veracidade, conforme o protocolo CLSI EP15-A2 usando controles Bio-Rad, intervalo de medição segundo o protocolo CLSI EP6-A, limite de quantificação, de acordo com CLSI EP- 17-A2 e intervalos de referência, de acordo com o protocolo CLSI EP28-A3C. Os dados foram analisados através de LinChecker e GraphPad 5. Nos ensaios realizados foram obsevadas as especificações estabelecidas pelo fabricante, bem como a exigência de qualidade deste laboratório que é variabilidade biológica mínima. Os intervalos de referência para indivíduos adultos também foram verificados. Desta forma, foi possível realizar a verificação do analisador hematológico, que demonstra que os parâmetros analíticos avaliados têm um desempenho aceitável.

Accuracy of 3D white light scanning of abutment teeth impressions: evaluation of trueness and precision

PURPOSE: This study aimed to evaluate the accuracy of digitizing dental impressions of abutment teeth using a white light scanner and to compare the findings among teeth types. MATERIALS AND METHODS: To assess precision, impressions of the canine, premolar, and molar prepared to receive all-ceramic crowns were repeatedly scanned to obtain five sets of 3-D data (STL files). Point clouds were compared and error sizes were measured (n=10 per type). Next, to evaluate trueness, impressions of teeth were rotated by 10degrees-20degrees and scanned. The obtained data were compared with the first set of data for precision assessment, and the error sizes were measured (n=5 per type). The Kruskal-Wallis test was performed to evaluate precision and trueness among three teeth types, and post-hoc comparisons were performed using the Mann-Whitney U test with Bonferroni correction (alpha=.05). RESULTS: Precision discrepancies for the canine, premolar, and molar were 3.7 microm, 3.2 microm, and 7.3 microm, respectively, indicating the poorest precision for the molar (P<.001). Trueness discrepancies for teeth types were 6.2 microm, 11.2 microm, and 21.8 microm, respectively, indicating the poorest trueness for the molar (P=.007). CONCLUSION: In respect to accuracy the molar showed the largest discrepancies compared with the canine and premolar. Digitizing of dental impressions of abutment teeth using a white light scanner was assessed to be a highly accurate method and provided discrepancy values in a clinically acceptable range. Further study is needed to improve digitizing performance of white light scanning in axial wall.