Reliability of light microscopy and a computer-assisted replica measurement technique for evaluating the fit of dental copings

Abstract The aim of this in vitro study was to assess the reliability of two measurement systems for evaluating the marginal and internal fit of dental copings. Material and Methods: Sixteen CAD/CAM titanium copings were produced for a prepared maxillary canine. To modify the CAD surface model using different parameters (data density; enlargement in different directions), varying fit was created. Five light-body silicone replicas representing the gap between the canine and the coping were made for each coping and for each measurement method: (1) light microscopy measurements (LMMs); and (2) computer-assisted measurements (CASMs) using an optical digitizing system. Two investigators independently measured the marginal and internal fit using both methods. The inter-rater reliability [intraclass correlation coefficient (ICC)] and agreement [Bland-Altman (bias) analyses]: mean of the differences (bias) between two measurements [the closer to zero the mean (bias) is, the higher the agreement between the two measurements] were calculated for several measurement points (marginal-distal, marginal-buccal, axial-buccal, incisal). For the LMM technique, one investigator repeated the measurements to determine repeatability (intra-rater reliability and agreement). Results: For inter-rater reliability, the ICC was 0.848-0.998 for LMMs and 0.945-0.999 for CASMs, depending on the measurement point. Bland-Altman bias was −15.7 to 3.5 μm for LMMs and −3.0 to 1.9 μm for CASMs. For LMMs, the marginal-distal and marginal-buccal measurement points showed the lowest ICC (0.848/0.978) and the highest bias (-15.7 μm/-7.6 μm). With the intra-rater reliability and agreement (repeatability) for LMMs, the ICC was 0.970-0.998 and bias was −1.3 to 2.3 μm. Conclusion: LMMs showed lower interrater reliability and agreement at the marginal measurement points than CASMs, which indicates a more subjective influence with LMMs at these measurement points. The values, however, were still clinically acceptable. LMMs showed very high intra-rater reliability and agreement for all measurement points, indicating high repeatability

Effect of different impression materials on the marginal fit of frameworks: An in-vitro study

Objectives: The objective of this study was to compare the accuracy of three different impression materials with evaluating the marginal fits of metal frameworks using replica technique.Materials and Methods: A phantom premolar tooth was prepared with a 1 mm circumferential chamfer preparation. Four impression materials: two vinyl polysiloxane (VPS) (Affinis Precious, (Group A); Elite HD, (Group E)), one polyether (Impregum Penta Soft, (Group P)) and one vinyl siloxanether (Identium, (Group I)) were used for producing stone casts of this master model. Twelve measurements per replica were carried out using a light microscope X40 magnification by Leica software, to assess the vertical marginal gap (VMG). Data were analyzed using the analysis of variance followed by Tukey’s test (p=0.05).Results: Specimens of the Group A and I showed significantly lower VMG values than those of Group E and Group P (p<0.001). Differences were not significant between groups A and I, and E and P either (p>0.05).Conclusions: All impression materials were clinically acceptable. As well as composition of the impression materials, size of filler particles and fluid mechanics of flow into very small spaces can be effective on accuracy of the materials

O ajuste marginal de restaurações indiretas: fluxo digital versus convencional – revisão narrativa

Na Medicina Dentária atual, as restaurações indiretas são amplamente utilizadas para a recuperação da forma, estética e função da dentição em detrimento das restaurações diretas devido às várias vantagens que apresentam. As exigências estéticas, quer por parte dos pacientes quer por parte dos médicos dentistas, têm aumentado e com elas o desenvolvimento de materiais dentários que atendam à estética e à resistência mecânica necessárias para o sucesso de uma restauração. A longevidade das restaurações depende, em grande parte, do seu ajuste marginal. Na literatura, vários são os estudos debruçados sobre dos valores de gap marginal existentes nas restaurações. Para além disso, também é analisado a variabilidade desses valores quando é utilizado um fluxo de trabalho digital e convencional. O objetivo desta narrativa passa por avaliar a influência da técnica utilizada sobre o ajuste marginal e a variação desses valores, considerando os fatores que afetam o resultado final da restauração.In today’s dental medicine, indirect restorations are widely used to recover form, aesthetics and function, opposed to direct restorations due to their advantages. Aesthetic standards have been continuously enhanced by doctors to meet the patient’s demands. At the same time, new dental materials are being developed to attend those specifications, to meet both the aesthetic and mechanical demands, needed for a successful restoration. The longevity of restorations depends greatly on its marginal fit. In the literature, many studies report the ranges of marginal gaps, as well as the comparison of their variability when using digital and conventional workflows. The goal of this narrative is to evaluate the influence of the technique used on the marginal fit and its values, considering the factors that affect the final result of the restoration

Einfluss des High-Speed-Sinterprozesses auf Ermüdungsverhalten, Genauigkeit und Passgenauigkeit von 4Y-TZP

Problemstellung Die High-Speed-Sinterung ermöglicht die Herstellung von monolithischen Zirkonoxidrestaurationen in stark verkürzter Zeit. Neben der Behandlungsdauer sind vor allem die Materialeigenschaften entscheidend für die Patientenzufriedenheit. In Verbindung mit der 4. Generation von Y-TZP (4Y-TZP) können ästhetisch hochwertige Restaurationen ermöglicht werden. Bisher gibt es jedoch kaum Veröffentlichungen zum Ermüdungsverhalten, zur Genauigkeit und Passgenauigkeit von 4Y-TZP in-vitro. Antón X, Liebermann A, Hampe R, Joda T, Stawarczyk B. Impact of High-Speed Sintering and Choice of Preshaded Monochrome or Multilayered Blanks on Fatigue Behavior of 4 mol% Yttria-Stabilized Tetragonal Zirconia Polycrystal. J Prosthet Dent 2021;0022-3913(21):00627-2. (doi: 10.1016/j.prosdent.2021.11.006) Material und Methoden Für die Untersuchung des Dauerlastverhaltens von 4Y-TZP wurden 4-Punkt-Biegefestigkeits-Prüfkörper (N=405) hergestellt. Das Multilayer Material (Zolid DRS) wurde High-Speed gesintert (1580°C für etwa 20 min) (Zolid DRS) und das Multilayer Material (Zolid Gen-x) wurde konventionell gesintert (1450°C für etwa 10 h). Das monochrome Material (Ceramill Zolid HT+PS) wurde ebenfalls konventionell gesintert (1450°C für etwa 10 h). Das Ermüdungsverhalten wurde unter Verwendung von fünf Kraftprotokollen ermittelt. Es wurden drei Stufenprotokolle (P1: 50 N / 5000 Zyklen, P2: 10 N / 1000 Zyklen und P3: 5% / 5000 Zyklen), ein Protokoll mit einer konstanten Kraft von 720 N (P4) und ein weiteres Protokoll mit verschiedenen Kraftstufen (P5) verwendet. Die Kraftstufenprotokolle wurden mit Kaplan-Meier und Mantel-Cox Tests analysiert (α=.05). P4 wurde nicht-parametrisch mit Kolmogorov-Smirnov, Kruskal-Wallis und Mann-Whitney U Tests ausgewertet. Für P5 wurde ein Kraft-Zyklen Diagramm erstellt. Außerdem wurde eine Frakturanalyse durchgeführt. Ergebnisse Das konventionell gesinterte Multilayer Material ZMLC zeigte bei der Untersuchung mit allen drei Stufenprotokollen (P1-P3) bessere Kraftwerte als die beiden anderen Materialien ZMLH (P≤.006) und ZMOC (P≤.002). Diese zeigten vergleichbare Ergebnisse (P≥.285). In den anderen beiden Protokollen traten keine signifikanten Unterschiede auf (P=.163 für P4). Antón X, Stawarczyk B, Reymus M, Joda T, Liebermann A. Impact of High-Speed Sintering on Accuracy and Fit of 4 mol% Yttria-Stabilized Tetragonal Zirconia Polycrystals. Int J Prosthodont 2021;34(6):775-783. (doi: 10.11607/ijp.7428) Material und Methoden Zur Untersuchung von Genauigkeit (Richtigkeit und Reproduzierbarkeit) und Passgenauigkeit wurden Kronen, Freiendbrücken und Endpfeilerbrücken aus drei verschiedenen 4Y-TZP Materialien hergestellt. Wie bereits oben beschrieben, wurde das Multilayer Material (Zolid DRS) High-Speed gesintert, während die beiden anderen Materialien (Zolid Gen-x und Ceramill Zolid HT+PS) konventionell gesintert wurden. Die High-Speed-Sinterung wurde bei 1580°C für 20 min durchgeführt, die Sinterzeit der konventionellen Sinterung betrug bei 1450°C etwa 10 h. Im Anschluss wurden die Prüfkörper eingescannt und die Genauigkeit und Passgenauigkeit mit Hilfe einer 3D-Analyse Software (GOM Inspect 2019) bestimmt. Die Auswertung wurde nicht-parametrisch mit dem Kolmogorov-Smirnov, Kruskal-Wallis und Mann-Whitney U Test ausgeführt (α=.05). Ergebnisse Die Genauigkeit zeigte bei den Multilayer Materialien für die High-Speed-Sinterung signifikant schlechtere Werte als für die konventionelle (P≤.001-.008). Endpfeilerbrücken zeigten allgemein geringere Genauigkeitswerte als Freiendbrücken und Kronen. Auf die Passgenauigkeit von Kronen und dreigliedrigen Brücken hatte die Wahl des Sinterverfahrens keinen Einfluss (P=.154-.877). Schlussfolgerung Die High-Speed-Sinterung hat im Vergleich zur konventionellen Sinterung einen negativen Einfluss auf das Dauerlastverhalten und die Genauigkeit von 4Y-TZP in-vitro. Auf die Passgenauigkeit hatte die High-Speed-Sinterung keine klinisch relevanten Effekte. Die Multilayer-Technik hingegen führte zu einer Verbesserung des Dauerlastverhaltens, im Vergleich zum monochromen Material. Insgesamt zeigte das High-Speed gesinterte Multilayer-Material ähnliche Dauerlastwerte und Genauigkeiten wie das monochrome Material.Statement of problem High-speed sintering enables the fabrication of monolithic zirconia restorations in a greatly reduced time. In addition to the treatment time, the material properties are decisive for patient satisfaction. In combination with the 4th generation of Y-TZP (4Y-TZP), esthetically high-quality restorations can be achieved. To date, however, there are hardly any publications on the fatigue behavior, accuracy and fit of 4Y-TZP in vitro. Antón X, Liebermann A, Hampe R, Joda T, Stawarczyk B. Impact of High-Speed Sintering and Choice of Preshaded Monochrome or Multilayered Blanks on Fatigue Behavior of 4 mol% Yttria-Stabilized Tetragonal Zirconia Polycrystal. J Prosthet Dent 2021;0022-3913(21):00627-2. (doi: 10.1016/j.prosdent.2021.11.006) Material and Methods For the investigation of the fatigue behavior of 4Y-TZP, 4-point flexural strength test specimens (N=405) were fabricated. The multilayer material (Zolid DRS) was sintered high-speed (1580°C for about 20 min) (Zolid DRS) and the multilayer material (Zolid Gen-x) was sintered conventionally (1450°C for about 10 h). The monochrome material (Ceramill Zolid HT+PS) was also conventionally sintered (1450°C for about 10 h). Fatigue behavior was determined using five load protocols. Three step-stress protocols (P1: 50 N / 5000 cycles, P2: 10 N / 1000 cycles, and P3: 5% / 5000 cycles), one constant load protocol with 720 N (P4), and another protocol with different load levels (P5) were used. The load level protocols were analyzed with Kaplan-Meier and Mantel-Cox tests (α=.05). P4 was analyzed non-parametrically with Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests. For P5, a load-cycle diagram was drawn. A fracture analysis was performed. Results The conventionally sintered multilayer material ZMLC showed better load values than the other two materials ZMLH (P≤.006) and ZMOC (P≤.002) when tested with all three step-stress protocols (P1-P3). These showed comparable results (P≥.285). No significant differences occurred in the other two protocols (P=.163 for P4). Antón X, Stawarczyk B, Reymus M, Joda T, Liebermann A. Impact of High-Speed Sintering on Accuracy and Fit of 4 mol% Yttria-Stabilized Tetragonal Zirconia Polycrystals. Int J Prosthodont 2021;34(6):775-783. (doi: 10.11607/ijp.7428) Material and Methods To investigate accuracy (trueness and reproducibility) and fit, crowns, cantilever bridges and conventional bridges were fabricated from three 4Y-TZP materials. As described above, the multilayer material (Zolid DRS) was high-speed sintered, while the other two materials (Zolid Gen-x and Ceramill Zolid HT+PS) were conventionally sintered. The high-speed sintering was performed at 1580°C for 20 min, while the sintering time of the conventional sintering was about 10 h at 1450°C. Subsequently, the specimens were scanned, and the accuracy and fit were determined using 3D analysis software (GOM Inspect 2019). The evaluation was performed non-parametrically using the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests (α=.05). Results The accuracy showed significantly worse values for multilayer materials for high-speed sintering than for conventional (P≤.001-.008). Conventional bridges generally showed worse accuracy values than cantilever bridges and crowns. The choice of sintering method had no effect on the accuracy of fit of crowns and three-unit bridges (P=.154-.877). Conclusions Compared with conventional sintering, high-speed sintering showed a negative effect on the fatigue behavior and accuracy of 4Y-TZP in vitro. The multilayer technique, in contrast, resulted in an improvement of the fatigue behavior, compared to the monochrome material. Regarding fit of 4Y-TZP restorations, high-speed sintering and choice of blank had no clinically relevant effects. Overall, the high-speed sintered multilayer material showed similar fatigue values and accuracies as the monochrome material

Adaptação marginal e interna das infraestruturas em zircónio fabricadas pelos sistemas CAD/CAM

Dissertação para obtenção do grau de Mestre no Instituto Superior de Ciências da Saúde Egas MonizA adaptação marginal e interna das infraestruturas em zircónio são um dos fatores responsáveis pelo sucesso e a longevidade de uma coroa cerâmica. O objetivo deste trabalho foi verificar a influência do sistema CAD/CAM e os materiais utilizados pelos sistemas sobre o ajuste das infraestruturas. Foram fabricadas 2 infraestruturas de zircónio de marcas diferentes, Zenostar® T (Wieland, Ivoclar Vivadent©, Germany) e UPzir® (Upcera, China) utilizando o sistema CAD/CAM 3Shape™ (Wieland, Germany) e 1 infraestruturas de zircónio de Lava™ Zirconia (3M™ESPE, Germany)., utilizando o sistema CAD/CAM de Lava™ (3M™ ESPE, Germany). Foi feita uma réplica em polivinilsiloxano de cada infraestrutura aplicando uma pressão digital continua, e 3 réplicas aplicando uma pressão contínua de 4,5kg. As réplicas foram cortadas em 4 pedaços (um para cada face do dente) e cada pedaço foi observado pela lupa Leica®MZ6 (Leica®, Germany) com uma ampliação de 40 vezes. A medição das réplicas foi feita em 5 regiões: na região marginal, na linha de terminação, na parede axial, no angulo áxilo-oclusal e na face oclusal com o software Image J (National Institute of Health, USA) utilizando as imagens feitas pela máquina fotográfica Leica® DFC290 HD (Leica®, Germany). Foi calculada a média aritmética da cada região. Resultados: Os valores médios de desajuste marginal (4,825 μm) e oclusal (12,935 μm) da infraestrutura Lava eram mais baixos do que os valores médios das infraestruturas Zenostar T (7,275 μm; 27,998 μm) e UPzir (7,995 μm; 25,242 μm). Na região axial os valores médios do desajuste das infraestruturas Zenostar T (4,917 μm) e UPzir (3,815 μm) eram baixos do que a infraestrutura Lava (7,122 μm). Conclusão: O sistema CAD/CAM da Lava™ consegue realizar infraestruturas com uma maior precisão do que o Sistema 3Shape™. O tipo de pressão aplicada na técnica de replicação não afeita os valores de ajuste da infraestrutura

Influência de fatores clínicos na adaptação marginal de restaurações cerâmicas fixas com tecnologia CAD/CAM

Tese de mestrado, Medicina Dentária, Universidade de Lisboa, Faculdade de Medicina Dentária, 2017Introdução: A confeção de restaurações cerâmicas por via CAD/CAM é uma realidade cada vez mais abrangente na área da Medicina Dentária. Com o desenvolvimento tecnológico e o aparecimento de cerâmicas melhoradas, a realização de restaurações estéticas parece ter vindo a ser facilitada para o clínico. A adaptação marginal é um dos principais alvos do sucesso de uma reabilitação fixa e neste sentido, torna-se importante conhecer quais os fatores de envolvência clínica, inerentes à confeção de restaurações cerâmicas com sistemas CAD/CAM, que a podem influenciar. Objetivo: Realizar uma revisão da literatura atual, visando responder à questão PICO: “Na reabilitação de peças e/ou ausências dentárias com restaurações cerâmicas fixas, confecionadas com tecnologia CAD/CAM, quais os fatores de escolha clínica que podem influenciar a adaptação marginal?” Materiais e Métodos: Foi efetuada uma pesquisa na base de dados primária MEDLINE, por artigos em inglês e publicados desde 2006, com a seguinte sequência de palavras-chave: cad cam AND ceramic AND marginal AND (adaptation OR fit OR gap OR discrepancy) AND (fixed OR crown OR bridge) NOT implants. Dos 200 artigos obtidos, foram incluídos 49 nesta dissertação. Resultados: 11 estudos avaliaram o desenho do preparo, 13 a técnica de digitalização, 11 o material cerâmico, 19 o sistema CAD/CAM utilizado e 5 a cimentação. Dez destes artigos abordam múltiplos fatores, pelo que se encontram repetidos nesta descrição. Conclusões: Todos os fatores avaliados parecem ter alguma influência na adaptação marginal de restaurações cerâmicas confecionadas com tecnologia CAD/CAM, contudo a diversidade de protocolos adotados nos diferentes estudos limita a sua comparação. Em estudos futuros, é necessário que haja uma maior padronização para que se possam retirar conclusões mais fidedignas do ponto de vista de evidência científica.Introduction: The manufacture of ceramic restorations with CAD / CAM systems is an increasingly wide reality in Dentistry. With the technological development and the appearance of improved ceramics, the accomplishment of esthetic restorations seems to have been facilitated for the clinician. The marginal fit is one of the main predictors of a fixed rehabilitation success, thus, it is important to know which clinical factors, involved in the production of CAD / CAM ceramic restorations, can have an influence in it. Objective: To carry out a review of the current literature, in order to answer the PICO question: "In the rehabilitation of dental pieces and/or absences with fixed ceramic restorations, fabricated with CAD / CAM technology, which factors, of clinical choice, can influence the marginal adaptation?" Materials and Methods: A search was performed in the MEDLINE primary database for articles in English and published since 2006, with the following sequence of keywords: cad cam AND ceramic AND marginal AND (adaptation OR fit OR gap OR discrepancy) AND (fixed OR crown OR bridge) NOT implants. Of the 200 articles obtained, 49 were included in this dissertation. Results: 11 studies evaluated the design of the preparation, 13 the scanning technique, 11 the ceramic material, 19 the CAD / CAM system used and 5 the cementation. Ten of these articles address multiple factors, therefore they are repeated in this description. Conclusions: All the factors evaluated seem to have some influence on the marginal adaptation of ceramic restorations made with CAD / CAM technology. However, the diversity of protocols adopted in the different studies limits their comparison. In future studies, it is necessary to have a greater standardization so that more reliable conclusions can be drawn from the point of view of scientific evidence

Vergleichende Untersuchungen zur Randspaltdetektion

Die Zielsetzung der Studie war der Vergleich von zwei Verfahren der Abformung (optisch vs. konventionell) durch messtechnische Erfassung des Randspaltes bei CAD/CAM–gefertigten Vollkeramikkappen in Vitro. Eine präzise Erfassung der Präparationsgrenze am Pfeilerzahn ist in ihrer Genauigkeit essentiell für die Erstellung einer langlebigen Restauration. Die Vermessung der Randspaltgröße wurde gemäß der Nomenklatur von Holmes et.al. (1989) durchgeführt. Die optische Abformmethode zeigte statistisch signifikant genauere Ergebnisse im Vergleich zur konventionellen Doppelmischabformung

Dreidimensionale digitale Analyse der internen und marginalen Passung gepresster Lithiumdisilikat-Teilkronen in vitro

Die Qualität vollkeramischer Restaurationen wird maßgeblich durch ihre Passgenauigkeit bestimmt. In der vorliegenden In-vitro-Studie soll die Passung keramischer Teilkronen in Abhängigkeit zum verwendeten Abformverfahren digital untersucht werden. Ein zur Aufnahme einer Teilkrone präparierter Molar aus Kunststoff wurde in Monophasen-, Doppelmisch- und Korrekturtechnik unter standardisierten Bedingungen abgeformt. Anschließend wurden Präzisionsmodelle hergestellt und hierauf Kronen aus Lithiumdisilikat gepresst. Die dreidimensionale Digitalisierung der Teilkronen sowie des als Referenz dienenden präparierten Zahnes erfolgte mit einem Streifenlichtscanner. In einem für industrielle Vergleichsanalysen entwickelten Computerprogramm wurden die Kronen im „Best-Fit“-Verfahren virtuell auf den Stumpf aufgesetzt. Hierbei wurde sowohl die Passung auf der gesamten Präparation als auch die Passung isoliert auf den Bereich der Präparationsgrenzen betrachtet. Die Auswertung erfolgte qualitativ mit Hilfe von Farbdifferenzbildern während der quadratische Mittelwert aller Messpunkte die Passungsdiskrepanz quantifiziert. Zur statistischen Analyse diente eine einfaktorielle Varianzanalyse mit multiplen Vergleichen nach Scheffé (n = 7, α = 0,05).Es ergaben sich mittlere interne (marginale) Passungsdiskrepanzen in µm: Doppelmischtechnik 31 ± 14 (77 ± 18), Monophasentechnik 21 ± 8 (69 ± 13), Korrekturtechnik 52 ± 11 (112 ± 19). Unterschiede zwischen ein- und zweizeitigen Techniken waren statistisch signifikant. Qualitativ führen Kronenanteile mit ausgeprägten Kurvaturen zu stärkeren Passungsdifferenzen als solche mit weich gestalteten Übergängen. Es kann gefolgert werden, dass einzeitige Abformtechniken im Vergleich zum zweizeitigen Vorgehen zu signifikant geringeren marginalen und internen Passungsdifferenzen führen und daher in der zahnärztlichen Praxis bevorzugt angewandt werden sollten

Digital Workflows and Material Sciences in Dental Medicine

The trend of digitalization is an omnipresent phenomenon nowadays – in social life and in the dental community. Advancement in digital technology has fostered research into new dental materials for the use of these workflows, particularly in the field of prosthodontics and oral implantology.CAD/CAM-technology has been the game changer for the production of tooth-borne and implant-supported (monolithic) reconstructions: from optical scanning, to on-screen designing, and rapid prototyping using milling or 3D-printing. In this context, the continuous development and speedy progress in digital workflows and dental materials ensure new opportunities in dentistry.The objective of this Special Issue is to provide an update on the current knowledge with state-of-the-art theory and practical information on digital workflows to determine the uptake of technological innovations in dental materials science. In addition, emphasis is placed on identifying future research needs to manage the continuous increase in digitalization in combination with dental materials and to accomplish their clinical translation.This Special Issue welcomes all types of studies and reviews considering the perspectives of the various stakeholders with regard to digital dentistry and dental materials