The Effect of Optical Conditioning of Preparations with Scan Spray on Preparation Form

Svrha rada: Za primjenu sustava CAD/CAM u ordinacijama dentalne medicine potrebno je odabrati sprej za skeniranje. Njegovom primjenom mijenja se prekrivena preparacija, što može nepovoljno utjecati na rubno zatvaranje i interno prianjanje restauracije. Zadaća ovog istraživanja bila je odrediti utjecaj spreja na preparacijsku formu procjenom morfologije i debljine triju različitih sprejeva za skeniranje. Materijali i metode: Određivala se površinska morfologija prekrivanja triju (A, B, C) različitih sprejeva za skeniranje uz pomoć konfokalnoga laserskog mikroskopa. Debljina sprejem nanesenog premaza mjerila se na staklenoj pločici i u simuliranim kliničkim uvjetima profilometrom i uređajem za digitalizaciju površine. Podaci su analizirani jednosmjernim testom ANOVA (α = .05). Rezultati: Konfokalni laserski mikroskop prikazao je grubu i nepravilnu sprejem pokrivenu površinu nakon uporabe svih sprejeva, te se od spreja A preko spreja B do spreja C broj malih zrnaca povećavao. Srednja debljina prekrivanja na staklenoj pločici iznosila je za sprej A 25,3 Μm, za B 18,9 Μm i za C 19,2 Μm. Statistički značajne razlike bile su između sprejeva A i B (p=0,017). U simuliranim kliničkim uvjetima srednja debljina prekrivanja iznosila je za sprej A 15,5 Μm, za B 15,0 Μm i za C 13,3 Μm. Razlika je bila statistički značajna samo između sprejeva A i C (p=0,033). Zaključak: Premazi nakon korištenja različitih sprejeva imali su drugačije površinske morfologije i različite debljine. Posljedično tome primjena spreja za skeniranje utječe i na konačnu CAD/CAM restauraciju, premda se kliničkim korištenjem postigla prihvatljiva debljina prekrivanja.Objective: CAD/CAM systems require scan spray for chairside sampling of tooth surfaces. However, this leads to alterations of the sprayed preparation and may affect marginal and internal adaption of the restoration. The aim of this study was to define the effect of scan spray on preparation form by evaluating the morphologies and the thicknesses of three different scan sprays. Materials and Methods: The surface morphology of the coatings of different scan sprays (A, B, C) was evaluated by use of a confocal laser scanning microscope. The thicknesses of spray coatings were measured on a glass plate as well as under simulated clinical conditions using a profilometer and a surface digitalisation device. The data were analysed by a 1-way ANOVA (α = .05). Results: The confocal laser scanning microscopy showed rough and irregular formed coating surfaces of all sprays, whereas an increasing numbers of small spray particles were seen from spray A over spray B to spray C. Mean coating thicknesses on the glass plate were: spray A 25.3 Μm, spray B 18.9 Μm and spray C 19.2 Μm. Significant differences were detected between spray A and B (P = .017). Under simulated clinical conditions median coating thicknesses were: spray A 15.5 Μm, spray B 15.0 Μm and spray C 13.3 Μm. A statistically significant difference could be detected only between spray A and C (P = .033). Conclusions: The coatings of the used scan spray systems showed different surface morphologies and exhibited different thicknesses. Consequently, the application of scan sprays affects the precision of the final CAD/CAM restorations. However, the scan sprays under investigation showed acceptable coating thicknesses for clinical use

In Vitro Compressive Fracture Resistance Of The Human Maxillary First Premolar With Different Mod Cavity Design And Restorative Materials

Cuspal failures of MOD (mesial-occlusal-distal) restored teeth have been constantly observed in clinic especially those restored with amalgam. As the pulpal depth and isthmus width of the preparation increases, the strength decreases. A number of studies have investigated the adhesive technique which is intended to increase the fracture resistance by bonding the tooth structure. The results of the studies are controversial because of the differences of research design among studies. The purpose of this study is to evaluate the fracture resistance of the human maxillary first premolar restored with condensable composite (Surefil, Dentsply) and CEREC 3D ProCAD leucite-reinforced ceramic inlays with a variety of MOD cavity preparations with different pulpal depths and isthmus widths. METHODS: Ninety, freshly extracted intact maxillary first premolars were selected and divided into 9 groups, consisting of 10 premolars each. The teeth were prepared with a high speed handpiece to create different widths and depths of the MOD cavities. Subsequently, the ii teeth were restored with condensable composite resin or ceramic inlays. The specimens were then subjected to a compressive axial loading in a Universal testing machine at 0.5mm/minute by means of a steel ball, 4.82mm in diameter. All pressures were against only tooth structure, and the special head did not contact any restorative material. The final result was analyzed with Two-way ANOVA and Tukey post-hoc testing RESULTS AND CONCLUSIONS: 1. A bonded ceramic restoration restores a tooth to the same fracture resistance as a natural tooth. A ceramic inlay restored tooth has significantly higher cuspal fracture resistance as compared to a composite restored tooth. (P = 0.0007). 2. Mean fracture resistance of teeth restored with Surefil and a 3mm cavity width was higher than groups with a 2mm cavity width due to the dramatic transition of the outline form between the occlusal aspect and proximal boxes. 3. Cavity pulpal floor depth is not a significant factor of cuspal fracture resistance in a tooth restored with either a ceramic inlay or composite resin

Retention Of Cad/Cam Crowns Luted With Resin Cements And Rmgi

Objectives: To measure retention of lithium disilicate (IPS e.max CAD, Ivoclar Viva-dent) and zirconia reinforced lithium disilicate (CELTRATM DUO, Dentsply) copings luted using resin cements and resin-modified glass ionomer cement. Methods: 110 Extracted human, non-carious mandibular 2nd premolars (n=10) were embedded in PVC cylinders with acrylic resin and placed into a lathe to produce a uni-form crown preparation (22°-convergence & 3mm-height). Following the orientation groove placement (69L bur), preparations were scanned and milled using a CEREC 3D/Sirona machine to produce e.max and CELTRATM DUO crowns. Preparations were imaged with a digital microscope (Keyence/VHX-600-20X) and the surface area of each crown was calculated. IPS e.max crowns and CELTRATM DUO crowns were cemented using the cements as in Tables 1 & 2. Specimens were stored (distilled water/37°C/24h) and thermocycled (10,000cycles/5-50°C/30secs) before debonding in tension at crosshead speed-5mm/min (INSTRON Model/5565). The bond strength was calculated by dividing the failure load with preparation surface area. The CELTRATM DUO and e.max data were compared separately with 1-way ANOVA and Tukey post-hoc analysis (alpha=0.05). Results: The simulated crown strength test results for e.max were: Calibra=4.89±2.35a; ExpE(TE)=3.70±2.08a,b; ExpSE=3.18±2.03a,b RelyXLP=3.11±1.99a,b; ExpE(Self-Etch)=2.74±1.23a,b; Multilink=2.66±1.72a,b; RelyXU=2.65±1.46a,b; Re-lyXLP/HF=1.91±0.70b. For CELTRATM: Exp/S=4.73±2.45a; Exp/S/E=4.40±1.76a,b; Re-lyXLP/HF=3.34±1.65a,b,c; Exp=1.79±0.70b,c; and RelyXLP=0.95±0.58c. The ANOVA showed some significant differences between groups (p=0.01) where the same letter denotes similar groups. Conclusions: The Calibra material resulted in significantly higher retention with the than RelyXLP/HF for the coping fabricated from emax. The experimental resin cement with silane when compared to Exp and RelyXLP resulted in significantly higher test retention strength for the CELTRATM DUO

Untersuchung zur Genauigkeit von scanbaren Bissnahmematerialien bei Verwendung mit dem Cerec 3D-System

Bei der Herstellung von Restaurationen mit dem Cerec 3D®-System (Sirona Dental Systems GmbH, Bensheim) besteht die Möglichkeit, die antagonistischen Kauflächen in die Konstruktion über den Scan eines Bissregistrats mit einzubeziehen. Durch Berücksichtigung der Informationen des Registrats bei der Herstellung der vollkeramischen Restauration sollen umfangreiche Einschleifmaßnahmen am Patienten entfallen. Die vorgestellte Untersuchung hat das Ziel festzustellen, mit welcher Präzision das Registrat Informationen an das Cerec 3D®-System übergibt. Untersucht wurde die Genauigkeit für die simulierte klinische Situation im Mund sowie die Labor-Situation am Gipsmodell. Es wurden neun scanbare Materialien verschiedener Hersteller im Vergleich untereinander bzw. im Vergleich zu einem primär nicht-scanbaren Material, dessen Oberflächen konditioniert wurde, vermessen. Die Registratherstellung erfolgte an stilisierten antagonistischen Teil-Kiefermodellen, die zur Simulation der Mundsituation in einem Artikulator montiert wurden. Diese Modelle wurden zunächst mechanisch vermessen. Zur Beurteilung der Registrate dienten die Cerec®-internen Höhenangaben, aus denen mit einem eigens dafür entwickelten Algorithmus die Wiedergabegenauigkeit durch Vergleich mit den mechanisch gewonnenen Daten berechnet wurde. Es wurden verschiedene Vorgehensweisen bei der Herstellung und Vermessung der Registrate durchgeführt. Das präziseste Vorgehen bei der Simulation der chairside-Behandlung ist durch möglichst geringe Manipulationen am Registrat charakterisiert. Das Einkürzen des Registrats auf Randleistenlänge sollte ohne Abnahme des Registrats von den Zähnen erfolgen. Das Konditionieren der Nachbarzähne mittels Scanspray wird in einem Arbeitsschritt auch auf die Registratoberfläche ausgeweitet. Dann betragen die Abweichungen zur Oberfläche des Originalmodells im Mittel 1 bis 14 µm, je nach Material. Die Abweichungen beim Umsetzen der Registrate auf ein Gipsmodell liegen hingegen im Mittel zwischen 36 und 98 µm

Evaluating Conventional and Digital Impressions of Single Unit Restorations, and Conventional vs. Digital Impressions from the Laboratory Technicians’ Perspective

Objectives: To Evaluate the quality of Digital Impressions and Conventional Impressions sent to commercial dental labs and to compare Conventional impressions vs. Digital impressions from the Laboratory Technicians’ Perspective. Background: The literature lacks studies that evaluate the quality of final impressions of indirect restorations, particularly in the USA, additionally there is a direct relation between impressions accuracy and produced restoration quality, which makes it impossible to produce high quality restoration from poor impression. Methods: 259 PVS impressions were evaluated for their quality by a calibrated examiner using a specific evaluation form. Type of tray, arch and required restoration were recorded. Impressions were evaluated for the following: defects related to prepared tooth and finish line (i.e. bubbles, voids, tears, clarity of finish line, and retraction cord left in impression) also, defects in material setting and distortion. Quality of tooth preparation was not assessed. Impressions were then ranked using 3-point Likert scale: Satisfactory, Questionable, and Unsatisfactory. Similarly, 74 Digital impressions were evaluated using a specific evaluation form by a calibrated examiner. Digital system brand, arch and required restoration were recorded. Impressions were evaluated for the following: inadequate scanned data, unclear margins, improper moisture control, improper powder application, improper occlusal registration, and presence of obstructions. Impressions were ranked using a 2-point Likert scale: Satisfactory or Unsatisfactory. Data was analyzed using Chi Square and Fisher’s exact test. Furthermore, a comparison between Conventional impressions and Digital impressions sent to lab was done through a survey answered by dental lab technicians’. Results: A total of 57.9% Conventional impressions were satisfactory and a significant difference was noted between tray type groups and impression ranking c2(4, n= 257)=17.36, p \u3c 0.001. A total of 78.4% of Digital impressions were satisfactory. Most frequent types of errors in Conventional impressions were the existence of tears, bubbles, and voids at the finish line resulting in unclear preparation margins at 36.3%, where the most frequent error in Digital impressions was inadequate scanned data at 18.9%. Regarding the Survey, 57.69% of technicians determined that number of errors in Digital impressions are less than Conventional impressions, and that the frequency of remakes in Digital impressions are also less than Conventional impressions by 63.46%. The results indicated that a total of 51.92% of the lab technicians advised for a shift to Digital impressions. The study concludes that Digital impression is a better option than Conventional impressions as a measure of its reduced errors and ease of use. Conclusion: Within the limitations of this study, when it comes to single unit restorations, dentists have to reconsider their impression taking methods and techniques

Influência de diferentes métodos de captura de imagem na adaptação marginal e interna de restaurações cerâmicas fabricadas pelo sistema CAD/CAM - CEREC 3D: um estudo in vitro

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Programa de Pós-Graduação em Odontologia, Florianópolis, 2010O objetivo desta pesquisa foi avaliar in vitro a influência de diferentes métodos de captura de imagem na adaptação marginal e interna de restaurações cerâmicas do tipo inlay, fabricadas com o sistema Cerec 3. Para isso, utilizaram-se 10 dentes molares humanos hígidos. Nestes foram realizados preparos MOD. Formaram-se quatro grupos: o IVD, em que foi utilizada a câmera de captura de imagem intraoral Cerec 3 sobre o dente preparado; o IVG, no qual foi utilizada a mesma câmera intraoral, porém a leitura foi realizada sobre o modelo de gesso; o IG, em que a leitura foi feita com o escâner InEos sobre o modelo de gesso; e o LG, no qual a leitura foi realizada com a máquina Cerec Scan sobre o modelo de gesso. Logo, para cada um dos 10 dentes, foram confeccionadas 4 peças cerâmicas. As análises das adaptações marginal e interna foram realizadas antes e após o ajuste interno das restaurações. Para a análise da adaptação marginal, cada peça era colocada sobre o dente, e esse conjunto era levado a um microscópio óptico com aumento de 70 vezes. Para a análise da adaptação interna, utilizou-se a técnica da réplica, na qual foi usado um silicone para simular o cimento resinoso. Após a análise estatística, pôde-se concluir que o ajuste interno das peças é fundamental para que elas apresentem um valor da adaptação marginal clinicamente aceitável e que, quando o escaneamento foi realizado sobre o modelo de gesso, o escâner InEos foi o que apresentou melhor adaptação

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

Influence of variations in ceramic thickness and bonding substrate on the fracture resistance of lithium disilicate restorations

Magister Scientiae Dentium - MSc(Dent)Restorative dentistry aims to replace lost or damaged tooth structure with durable and life-like alternatives. To accommodate the inherent limitations and weakness of the restorative materials, preparation techniques often require the sacrifice of healthy tooth structure to create enough restorative space. This can lead to weakening of the remaining tooth structure, with subsequent damage or catastrophic failure. When using indirect restoratives, the development of adhesive luting agents (adhesive cements) and stronger allporcelain restorations (lithium disilicate) has contributed to the development of “minimally invasive” preparation techniques and concepts such as cavity design optimization (CDO) and bio-substitution. With these techniques, resin materials are combined with ceramic restoratives in an attempt to not only produce strong restorations, but also increase the longevity of the remaining tooth. The clinician needs to therefore find the ideal preparation design that combine such materials to produces a clinically performing restoration while increasing the strength and longevity of the underlying tooth

Dental zirconia: in-vitro comparison and outcome of methods for veneering, glazing, and chipping repairs

OBJECTIVE: The purpose of this study is to evaluate the experimental properties of zirconia-based ceramics. METHODS: Zirconia bars were veneered to 2mm total thickness. Veneering-method groups included: 1.Hand-layered feldsparthic porcelain (VM=VitaVM9,Vident) and fluorapatite glass-ceramic (CR=IPSe.maxCeram,IvoclarVivadent); 2.Pressed feldspathic porcelain (PM=VitaPM9,Vident) and fluorapatite glass-ceramic (ZP=IPSe.maxZirPress,IvoclarVivadent); 3.CAD/CAM milled feldspathic ceramic (TF=VitablocsTriluxeForte,Vident) and lithium-disilicate glass-ceramic (CAD=IPSe.maxCAD,IvoclarVivadent). CAD/CAM veneers were either cemented with resin cements (P=Panavia21,KurarayDental), (R=RelyXUltimate,3M ESPE), (M=MultilinkAutomix,IvoclarVivadent) or fused with fusion glass-ceramic (C=CrystalConnect,IvoclarVivadent). A Three-point-bending test was performed. For group VM,PM,TF-M,TF-C,CAD-M,CAD-C, ten more bars were prepared and aged with cyclic loading and thermocycling before testing. Zirconia bars (PrettauZirconia,Zirkonzahn;inCorisTZI,Sirona;ZirluxFC,PentronCeramics) specimens were prepared and polished. The specimens were divided into 3 groups: control, self-glaze fired, and glazed groups. A Three-point bending test was performed. Veneered zirconia crowns were made. Feldspathic porcelain was applied to zirconia coping. Bevel cut on porcelain was made to simulate porcelain chipping. The crowns were then divided into 4 different groups according to repair materials including: 1.Conventional-resin composite (TetricEvoCeram,IvoclarVivadent) 2.Flowable-resin composite (G-aenialUniversalFlo,GCamerica) 3.Cemented CAD/CAM milled feldspathic ceramic (VitaTriluxForte,Vident) 4.Cemented CAD/CAM milled lithium-disilicate glass-ceramic (IPSe.maxCAD,IvoclarVivadent). Each crown underwent thermocycling. The test was performed by loading force on the center of repaired part to record load-to-failure. RESULTS: There were significant differences in the failure loads of non-aged bilayered veneer-zirconia bars. Aging experiment revealed a significant difference in failure load between non-aged and aged bars in groups VM and PM, but not in the groups with CAD/CAM milled veneers. There was significant influence of surface treatments on flexural strength of zirconia specimens. Post-hoc test showed that glazed group had significant lower flexural strength than other groups. Crowns repaired with CAD/CAM ceramics showed significant higher failure load than resin composite. Repairing with lithium-disilicate glass ceramic yielded the highest load-to-failure of the specimens. CONCLUSIONS: - Veneer materials, veneering methods, and cement materials have a significant effect on the failure load of bilayered veneer- zirconia. CAD/CAM veneer-zirconia is not susceptible to aging performed in this study. - Glazing decreased the flexural strength of high translucent zirconia. - Veneered zirconia crowns repaired with CAD/CAM ceramic materials have significantly higher load-to-failure than veneered crowns repaired with resin composite.2018-09-28T00:00:00