Ceramill Sintron Research Articles

Bond strength of ceramic veneered CAD-milled alloy upon prolonged sintering.

Ceramic-sintering affects bond strength and longevity of metal-ceramic. This study investigated the effect of sintering temperatures and times on metal-ceramic bond strength vis-a-vis interfacial fracture toughness. One hundred eighty rectangular-shaped (25 × 8 × 1mm) casting (Auriloy® (CA)) and CAD-milling (Ceramill Sintron® (MA)) alloys were prepared and randomly veneered with ceramic at normal (930°C; (TN)), increased (940°C; (TI)), and extremely increased (950°C; (TE)) sintering temperatures and normal (1min; (HN)), increased (2min; (HI)), and extremely increased (3min; (HE)) sintering time (n = 10/group). Pre-cracked was subjected to four loading-unloading cycles at 0.05mm/min speed to determine interfacial fracture toughness from strain energy release rate (G). Microstructures were examined with a scanning electron microscope (SEM), energy-dispersive X-ray (EDX), and atomic force microscopy (AFM). ANOVA and Tukey comparisons were determined for significant differences (α = 0.05). Significant differences in G due to the effect of alloy, sintering temperature, and time (p < 0.05) were indicated. MA revealed higher G than CA. Raising temperatures enabled increasing G for CA, not for MA. Extended sintering permitted increasing G for both alloys. Rougher surface of MA than CA was observed. Interfacial ion exchange was differently indicated between CA and MA. Bond strength was influenced by alloy, sintering temperature, and time. Ceramic has better adhesion to MA than CA. Enhancing bond for CA was succeeded through increasing sintering temperature and time, whereas through extended sintering for MA. MA offers stronger bond than CA. Enhancing bond is suggested by extended sintering. Raising temperature can enhance bond for CA, not for MA.

Effect of CAD-CAM Framework Design Fabricated from Sintered Cobalt-Chromium Alloy on Fracture Resistance of Metal-Ceramic Restorations.

Porcelain fracture is a common problem of metal-ceramic restorations (MCRs). One suggested strategy to prevent it is to modify the metal framework design; however, the available information regarding the effect of framework design on porcelain fracture is scarce. This study aimed to assess the effect of computer-aided design and computer-aided manufacturing (CAD-CAM) framework design fabricated from sintered cobalt-chromium (Co-Cr) alloy on fracture resistance of MCRs. Twenty premolar metal dies were fabricated for this in vitro study. Ten standard frameworks were designed with 0.5 mm thickness, and 10 customized frameworks were designed with 1 mm thickness at the lingual margin and 0.5 mm thickness in all other areas. All specimens were fabricated from sintered Co-Cr alloy (Ceramill Sintron) using soft metal milling technology. After porcelain application, the specimens underwent thermocycling and cyclic loading for 3,000 cycles between 5 and 55°C. The fracture resistance was measured by a universal testing machine. The failure mode was also determined. Data were statistically analyzed by independent t-test (α = 0.05). The mean fracture resistance of porcelain was 2,379 ± 531 N in the standard and 2,557 ± 448 N in the customized group. No significant difference was found in fracture resistance of the two groups (P > 0.05). All specimens in both groups showed mixed failure. The fracture resistance of porcelain and the failure mode were not affected by the framework design of MCRs fabricated from sintered Co-Cr alloy (Ceramill Sintron).

Investigation of the effect of bonding factors on strength of porcelain bond to soft metal alloys after application of thermal cycle

The chemical bond between the metal and the porcelain component is likely to fail in metal-porcelain restorations. This is due to the thick oxide layer that Cr-Co alloys create. This study aimed to investigate the effect of metal conditioner on controlling the oxide layer formed on the surface of the Sintron alloy and the strength of the metal-porcelain bond. In this in vitro study, 33 samples were divided into three groups based on surface treatment (n = 11). In all three groups, an oxide layer was created. In the first group, Shofu metal conditioner, in the second group, metal conditioner of Creation, and in the third group, no metal conditioner was applied. All samples were then subjected to 3000 heat cycles between 5° and 55°C with a stop time of 5 s. The specimens were then placed in a universal testing machine for shear bond testing. A force was applied between the alloy and the porcelain by a 5 kN load cell at the speed of 1 mm/min until a fraction occurred. Intergroup comparison was made by the one-way analysis of variance followed by the Tukey's multiple comparisons test (α = 0.05) . The mean shear bond strength of the first group was 34.93 MPa and the mean shear bond strength of the second group was 31.37 MPa. The mean shear bond strength of the first and the second group was significantly higher than the third group (23.37 MPa) (PV < 0.001). The use of metal conditioners between ceramill Sintron alloy and porcelain (Vita VMK MASTER) led to increasing the bond strength.

Effect of multiple firings on the shear bond strength of presintered cobalt-chromium alloy and veneering ceramic

Statement of problemHow multiple firing cycles may affect the oxide layer and, consequently, the shear bond strength of metal-ceramic restorations is unclear. PurposeThe purpose of this in vitro study was to determine the effect of multiple firings on the shear bond strength of porcelain to cobalt-chromium (Co-Cr) alloy. Material and methodsForty cylinders (Ø6.8×9 mm) of a representative presintered Co-Cr alloy (Ceramill Sintron) were prepared with computer-aided design and computer-aided manufacturing (CAD-CAM) technology. After airborne-particle abrasion and polishing, the specimens were ultrasonically cleaned of surface contaminants. A circular surface (Ø4×2 mm) was veneered on each specimen with porcelain (VM13) after 3 firings (wash opaque, opaque, and dentin). The specimens were then randomly divided into 4 groups (n=10). The normal group underwent 3 firings. The other groups underwent an additional porcelain firing: the one-plus firing group underwent 4 firings, the two-plus firing group underwent 5 firings, and the three-plus firing group underwent 6 firings. Next, the specimens were mounted in autopolymerized acrylic resin and tested in a universal testing machine and loaded at a crosshead speed of 0.5 mm/min at the metal-ceramic interface until fracture occurred. The average shear bond strength (MPa) was calculated by dividing the maximum fracture force (N) by the bonded surface of the specimens (mm2). The fracture patterns were observed microscopically and classified as adhesive, cohesive, or mixed. One-way ANOVA was used to determine differences between groups (α=.05). ResultsNo significant differences were found among the shear bond strengths of specimens after 3, 4, 5, and 6 porcelain firings (P>.05). The mean bond strength of all groups ranged from 30 to 34 MPa. The fracture pattern of all specimens was mixed, indicating that multiple firings had no significant effect on the failure pattern. ConclusionsMultiple porcelain firings under controlled conditions had no significant effect on the fracture pattern or shear bond strength of porcelain to a presintered Co-Cr alloy.

Comparison of Biocompatibility of Three Soft Milled Cobalt-Chromium Alloys.

In the context of biology and medicine, nanotechnology encompasses the materials, devices, and systems whose structure and function are relevant for small length scales, from nanometers through microns. The purpose of this study was to compare the microstructures and resultant biocompatibility of three commercially available soft milled cobalt-chromium (Co-Cr) alloys (Ceramill Sintron, CS; Sintermetall, SML; and Soft Metal, SM). Disc-shaped specimens were prepared by milling the soft blanks and subsequent post-sintering. The crystal and microstructures of the three different alloys were studied using optical microscopy, X-ray diffractometry (XRD), energy dispersive X-ray spectroscopy, and electron backscatter diffraction. The amounts of Co, Cr, and molybdenum (Mo) ions released from the alloys were evaluated using inductively coupled plasma-mass spectroscopy. The effect of ion release on the viability of L929 mouse fibroblasts was evaluated by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The SML alloy showed a finer grain size (approx. 5 μm) and a larger pore size (approx. 5 μm) than the CS and SM alloys, and its XRD pattern exhibited a slightly higher ε phase peak intensity than that of the γ phase. In the CS and SML alloys, the average crystallite sizes of the nano-sized Cr23C6 carbide were 21.6 and 19.3 nm, respectively. The SML alloy showed higher concentrations of Cr and Mo in the grain boundaries than the other two alloys. The SML alloy showed significantly higher Co and Mo ion releases (p < 0.001) and significantly lower cell viability (p < 0.05) than the CS and SM alloys. The combined results of this in vitro study suggest that the three soft milled Co-Cr alloys had different crystal and microstructures and, as a result, different levels of in vitro biocompatibility.

Effect of ceramic layering on the fit of cobalt-chromium alloy 3-unit fixed dental prostheses fabricated by additive, soft milling, and casting technologies

Statement of problemThe change in fit after ceramic layering of additively manufactured cobalt-chromium alloy frameworks has not been evaluated extensively. PurposeThe purpose of this in vitro study was to compare the fit of cobalt-chromium alloy fixed dental prostheses fabricated by different techniques before and after ceramic layering. Material and methodsA cobalt-chromium alloy master model was prepared to receive a 3-unit fixed dental prosthesis. Sixty cobalt-chromium alloy frameworks (N=60) were manufactured by using 3 manufacturing techniques (n=20): selective laser melting (Mediloy S-Co), soft milling (Ceramill Sintron), and conventional casting as the control group (Girobond NB). The replica technique was used to measure the marginal and internal discrepancies. The frameworks were then layered with ceramic, and the same fit measuring procedure was repeated. The results were compared before and after ceramic layering within each group. The data were analyzed using the Levene, ANOVA, and paired-samples t tests (α=.05). ResultsA significant difference was found within groups before and after ceramic layering for selective laser melting (P=.006) and soft milling (P=.009) but not for conventional casting (P>.05). No statistical difference was reported in the marginal region for conventional casting group (P=.155) in contrast with the soft milling and selective laser melting groups (P=.003). Soft milling showed increased gap values in the marginal (P=.006) and occlusal regions (P=.004). ConclusionsCeramic layering increased the discrepancy of the laser-sintered and milled frameworks, increasing the marginal discrepancy.

Comparison of microstructures and mechanical properties of 3 cobalt-chromium alloys fabricated with soft metal milling technology

Statement of problemAlthough several manufacturers market soft metal milling blanks and systems, comprehensive comparative studies of differences in properties across commercially available soft metal milling alloys are lacking. PurposeThe purpose of this in vitro study was to compare the microstructures and mechanical properties of 3 soft metal milling cobalt-chromium (Co-Cr) alloys (Ceramill Sintron, Soft Metal, and Sintermetall). Material and methodsDisk-shaped specimens (for surface characterization and hardness test) and dumbbell-shaped specimens (for tensile test as per International Organization for Standardization (ISO) 22674) were prepared by following each soft metal milling manufacturer’s instructions. The crystal structures and microstructures of the 3 alloys were evaluated with optical microscopy, X-ray diffractometry (XRD), and scanning electron microscopy with electron backscattered diffraction (EBSD). The mechanical properties were investigated with a tensile test and Vickers hardness test (n=6). The results of the mechanical (tensile and hardness) tests were analyzed with 1-way ANOVA and the post hoc Tukey multiple comparison test (α=.05). ResultsThe Sintermetall specimen showed a finer microstructure and more porosity than the other 2 alloys. The XRD and EBSD analyses showed that the γ (face-centered cubic, fcc) matrix phase was predominant in the Ceramill Sintron alloy and the ε (hexagonal close-packed, hcp) matrix phase was predominant in the Soft Metal alloy. The Sintermetall alloy showed a slightly higher amount of ε phase than γ phase, with more chromium carbide formation than the other 2 alloys. The Ceramill Sintron alloy showed a significantly higher tensile strength than the other 2 alloys (P<.05), but a significantly lower 2% offset yield strength than the other 2 alloys (P<.05). The highest elongation was found in the Ceramill Sintron alloy, followed by the Sintermetall and Soft Metal alloys. The elastic modulus was the highest in the Sintermetall alloy, followed by the Soft Metal and Ceramill Sintron alloys. No significant differences in Vickers hardness values were detected among the 3 alloys (P=.263). ConclusionsThe different commercially available soft metal milling blanks and systems produced dissimilar alloys in terms of crystal structures and microstructures and, as a result, different mechanical properties.

Evaluation of Marginal and Internal Fit of Presintered Co-Cr and Zirconia Three-Unit Fixed Dental Prosthesis Compared to Cast Co-Cr.

The precision of soft metal processing technologies is poorly documented. This study compared marginal and internal fit of presintered cobalt-chromium (Co-Cr) and zirconia three-unit fixed dental prostheses (FDPs) to cast Co-Cr. Three-unit FDPs were prepared on metal dies (N = 60) from typodont preparations of the maxillary right first premolar and molar. A standardized preparation of a metal-ceramic restoration was done on abutment teeth. The dies (N = 60) were scanned and divided into three groups (n = 20/group) to receive the FDP made of presintered Co-Cr (Ceramill Si), presintered zirconia (Ceramill Zi), and cast Co-Cr (Girobond NB). Each framework was seated on its specific cast. A replica technique was used for marginal and internal discrepancies measurements in mesiodistal and buccolingual planes. Data were analyzed using the Levene test, t-test, and analysis of variance (α = 0.05). When the overall mean discrepancy values were compared in the mesiodistal plane, a significant difference was found between Ceramill Sintron and Ceramill Zi groups (p = 0.026). No significant difference was detected between Girobond NB and Ceramill Sintron groups and between Girobond NB and Ceramill Zi groups (p = 0.537 and p = 0.569, respectively). In the buccolingual plane, there was no significant difference in the overall mean discrepancy between the three groups: CS/CZ (p = 1.000), GI/CS (p = 0.51), and GI/CZ (p = 0.87). Significant differences at several measurement points were found at the inter or intramaterial level. The increase in discrepancy values between marginal and occlusal measurements was evident for the three groups. Presintered three-unit FDPs fabricated from zirconia and Co-Cr exhibited internal and marginal discrepancy values similar to cast Co-Cr. A significant difference was reported between CS and CZ in mesiodistal planes. The axial and marginal differences in values for the three tested groups were below or around the 120 µm clinically acceptable threshold except for the occlusal area. When comparing first premolar to first molar, the internal and marginal discrepancies were similar with no apparent distortion of the framework after the sintering process.

Fitting accuracy of ceramic veneered Co-Cr crowns produced by different manufacturing processes.

PURPOSEThe purpose of this in vitro study was to evaluate the fitting accuracy of single crowns made from a novel presintered Co-Cr alloy prepared with a computer-aided design and computer-aided manufacturing (CAD/CAM) technique, as compared with crowns manufactured by other digital and the conventional casting technique. Additionally, the influence of oxide layer on the fitting accuracy of specimens was tested.MATERIALS AND METHODSA total of 40 test specimens made from Co-Cr alloy were investigated according to the fitting accuracy using a replica technique. Four different methods processing different materials were used for the manufacture of the crown copings (milling of presintered (Ceramill Sintron-group_cer_sin) or rigid alloy (Tizian NEM-group_ti_nem), selective laser melting (Ceramill NPL-group_cer_npl), and casting (Girobond NB-group_gir_nb)). The specimens were adapted to a resin model and the outer surfaces were airborne-particle abraded with aluminum oxide. After the veneering process, the fitting accuracy (absolute marginal discrepancy and internal gap) was evaluated by the replica technique in 2 steps, before removing the oxide layer from the intaglio surface of the crowns, and after removing the layer with aluminum oxide airborne-particle abrasion. Statistical analysis was performed by multifactorial analysis of variance (ANOVA) (α=.05).RESULTSMean absolute marginal discrepancy ranged between 20 µm (group_cer_npl for specimens of Ceramill NPL) and 43 µm (group_cer_sin for crowns of Ceramill Sintron) with the oxide layer and between 19 µm and 28 µm without the oxide layer. The internal gap varied between 33 µm (group_ti_nem for test samples of Tizian NEM) and 75 µm (group_gir_nb for the base material Girobond NB) with the oxide layer and between 30 µm and 76 µm without the oxide layer. The absolute marginal discrepancy and the internal gap were significantly influenced by the fabrication method used (P<.05).CONCLUSIONDifferent manufacturing techniques had a significant influence on the fitting accuracy of single crowns made from Co-Cr alloys. However, all tested crowns showed a clinically acceptable absolute marginal discrepancy and internal gap with and without oxide layer and could be recommended under clinical considerations. Especially, the new system Ceramill Sintron showed acceptable values of fitting accuracy so it can be suggested in routine clinical work.

Comparison of bond strength of two porcelains and two base metal alloys in metal-ceramic restorations

The purpose of this study was to evaluate the bond strength between two porcelains (VITA VMK Master and VITA VM13) and two types of base metal alloys (Ceramill Sintron and Verabond). In an experimental study, 20 rectangular strips (25 mm × 4 mm × 0.5 mm) of each base metal alloy (Ceramill Sintron and Verabond) were fabricated according to the manufacturer's instructions. After sandblasting and polishing, the samples were placed in an ultrasonic device to remove surface contaminants. A surface of 8 mm × 4 mm × 1 mm of samples was veneered with Vita VM13 and VITA VMK Master. The samples were divided into four groups (n = 10 each group; VM13/Ceramill, VMK Master/Ceramill, VM13/Verabond, and VMK Master/Verabond), and bond strength was evaluated by three-point bending test with a universal testing machine. Two-way ANOVA was used for comparison in each group, post hoc Scheffe's test was used for analyzing data between groups, and the Kolmogorov-Smirnov test was used for the normality (P < 0.05). The maximum bond strength was related to Verabond/VM13 (44.35 ± 7.9 MPa) and then the Ceramill Sintron/VM13 (39.33 ± 4.43 MPa), and the lowest was related to the Ceramill Sintron/VMK Master (29.75 ± 3.2 MPa). There was no significant difference between bond strength of VM13 with the two alloy groups (P > 0.05), and bond strength of VMK Master to Ceramill Sintron CAD/CAM alloy was less than the conventional Verabond alloy (P < 0.05); however, bond strength of all the groups was above the standard threshold (25 MPa). Based on the results of this study, the bond strength of the porcelain to Verabond was better, but the bond strength of the porcelain to Ceramill Sintron also was not less than the standard threshold; thus, this new CAD/CAM alloy can be an alternative to the conventional base metal alloys in the metal-ceramic restorations.

Comparative Study of the Fit Accuracy of Full-Arch Bar Frameworks Fabricated with Different Presintered Cobalt-Chromium Alloys.

Purpose This study was to measure the geometric discrepancies that occur during the sintering contraction of presintered Co-Cr alloys in a full-arch bar framework and to compare the variations between alloys from different manufacturers. Materials and Methods Eighteen implant-supported full-arch bar frameworks were fabricated through a soft-machining process using presintered Co-Cr alloy blocks: Ceramill Sintron (CS), Soft Metal (SM), and Sintermetall (SML) (n=6 for each group). The sintered frameworks were digitized using a structured light scanner, and the scan images were superimposed on the reference design. The geometric discrepancies of the sintered frameworks were three-dimensionally analyzed for horizontal, angular, and internal discrepancies. Kruskal-Wallis and Mann–Whitney U tests were used to compare the discrepancies among the groups (α=.05). Results Significant differences were found in the geometric discrepancy measurements among the groups. The CS group showed larger horizontal and angular discrepancies, followed by the SM and SML groups (P<.001). The root mean square (RMS) values for internal discrepancy were not statistically different among the groups (P=.778). Conclusion The geometric discrepancies of full-arch bar frameworks fabricated using the soft-machining process were affected by accuracies in sintering contraction of presintered alloys.

The evaluation and comparison of marginal adaptation in metal ceramic and all ceramic restorations fabricated by two methods: CAD/CAM and conventional

Introduction: Marginal fit is a key factor for long term clinical success through any dental restorations. Poor marginal adaptation causes cement dissolution. This can lead to dental caries, gingival irritation, periodontal diseases, and finally treatment failure. The aim of this study was measurement and comparison of marginal gap quantities in metal ceramic and all ceramic dental restorations fabricated by various methods. Methods & Materials: A total of 60 complete crowns in 6 groups (n=10) were fabricated as. Follows: Group A: Conventional metal-ceramic collarless restorations. Group B: Metal-ceramic collarless restorations with CAD/CAM wax copings and porcelain layering. Group C: Metal-ceramic collarless restorations with Ceramill Sintron metal copings and porcelain layering. Group D: All ceramic e-max. Press (lithium disilicate) restorations. Group E: All ceramic restorations with CAD/CAM zirconia copings and porcelain layering. Group F: All ceramic CAD/CAM translucent zirconia (Zolid). Replica technique and optical microscope (60 x magnifications) used to gap measurement. Mann whitney and kruskal-wallis tests used to analyze the data. Results: The lowest mean marginal gap seen in group C (29.12) and the highest mean marginal gap seen in group E(78.19)The mean marginal adaptation was better in metal ceramic restorations than all ceramic restorations and the difference was significant (P˂0.001). Conclusion: According to our study, marginal gap of metal ceramic and all ceramic restorations was clinically acceptable (less than 120 microns).

The Effect of Multiple Firings on the Shear Bond Strength of Porcelain to a New Millable Alloy and a Conventional Casting Alloy

This study compared the effect of multiple firings on the shear bond strength (SBS) of porcelain to the new millable alloy (Ceramill Sintron) and a conventional casting alloy (4-all). Thirty-six cylindrical cores (6.8 × 9 mm) were made of millable and castable alloy through CAD/CAM and casting techniques, respectively (n = 18). In the center of each bar, a 4 × 4 × 2-mm shot of porcelain was fused. Having divided each group into 3 subgroups based on the number of firing cycles (3, 5, 7), the specimens were fixed in a universal testing machine and underwent a shear force test (1.5 mm/min crosshead speed) until fractured. Then the SBS values (MPa) were calculated, and the failure patterns were microscopically characterized as adhesive, cohesive, or mixed. Two-way ANOVA statistical test revealed that the number of porcelain firings had no significant effect on the SBS of any of the metal groups (p = 0.1); however, it was statistically higher in the millable group than the castable group (p < 0.05). Moreover, detecting the mixed failure pattern in all the specimens implied that the multiple firings had no significant effect on the failure pattern. The multiple porcelain firings had no significant effect on the SBS of porcelain to neither the millable nor castable alloys.

Evaluation of dimensional accuracy of dental bridges manufactured with conventional casting technique and CAD/CAM system with Ceramill Sintron blocks using CMM.

Background. Recently, non-presintered chromium-cobalt (Cr-Co) blocks with the commercial name of Ceramill Sintron were introduced to the market. However, comprehensive studies on the dimensional accuracy and fit of multi-unit frameworks made of these blocks using the coordinate measuring machine (CMM) are lacking. This study aimed to assess and compare the dimensional changes and fit of conventional casting and milled frameworks using Ceramill Sintron. Methods. A metal model was designed and scanned and 5-unit frameworks were fabricated using two techniques: (I) the conventional casting method (n=20): the wax model was designed, milled in the CAD/CAM machine, flasked and invested; (II) the milling method using Ceramill Sintron blocks (n=20): the wax patterns of group 1 were used; Ceramill Sintron blocks were milled and sintered. Measurements were made on the original reference model and the fabricated frameworks using the CMM in all the three spatial dimensions, and dimensional changes were recorded in a checklist. Data were analyzed with descriptive statistics, and the two groups were compared using one-way ANOVA and Tukey test (α=0.05). Results. The fabricated frameworks in both groups showed significant dimensional changes in all the three dimensions. Comparison of dimensional changes between the two groups revealed no significant differences (P>0.05) except for transverse changes (arch) that were significantly greater in Ceramill Sintron frameworks (P<0.05). Conclusion. The two manufacturing processes were the same regarding dimensional changes and the magnitude of marginal gaps and both processes resulted in significant dimensional changes in frameworks. Ceramill Sintron frameworks showed significantly greater transverse changes than the conventional frameworks.

Comparison of Adhesion of a Novel Pre-sintered Cobalt-Chromium to Pre-sintered Zirconia and Cast Nickel–Chromium

This study compared the bond strength of pre-sintered Ceramill Sintron to pre-sintered zirconia and cast nickel-chromium (NiCr). Specimens (n = 60) (diameter: 15 mm; thickness: 2 mm) were prepared (n = 20/group) (Ceramill Sintron, Ceramill Zi, and Wirobond 99). Disks were layered with vita VM ceramic (4 mm). Specimens were randomly divided into two subgroups. Only one subgroup was thermocycled. Specimens were tested under shear strength. Energy-dispersive X-ray (EDX) mapping was done on one disk of each material before and after ceramic layering. Failure types were mostly mixed failures. Significant difference was found between the three materials for Y and Z failure types (p-values: 0.032 and 0.010 respectively). Thermocycling had no major effect on the results reported. Considering Fmax (force-inducing bonding failure) registered, significant difference was found between the control group and milled alloys groups. No significant difference was found between Ceramill Sintron and Zi. The EDX mapping showed a net increase in the control group oxide layer, whereas only slight increase and decrease were reported for Zi and Sintron respectively. When compared with cast NiCr, novel Ceramill Sintron has higher bond strength, comparable to Ceramill Zi. Thermocycling had no major effects on the results. Ceramic-alloy bonding is a primary factor in the prosthesis' longevity.

Marginal Discrepancy and Fracture Resistance of CAD/CAM Ceramill Sintron Metal Copings with Different Porcelain Materials

Background: This study was performed to compare the marginal fit changes and facture resistance of metal ceramic crowns constructed from Ceramill Sintron metal coping veneered with three different porcelain veneering materials (Vita Master Koromikos VMK, Willi Geller Creation CC and GC initial MC), also to evaluate the influence of thermocycling on load at fracture. Materials and Methods: Master brass die was scanned ,then metal coping was designed and milled from Ceramill Sintron blank to get 60 metal copings, then divided randomly into three groups(20 sample), then veneered with porcelain: VITA, Creation or GC. The marginal gaps were measured before and after porcelain veneering then marginal fit changes was calculated. Fracture resistance test was done by Instron®, the master die was duplicated to sixty analogs then each analog was fixed into acrylic base. After that each crown was cemented onto the corresponding die analog. Ten samples of each group were subjected to compressive loading to fracture and other ten subjected to thermocycling followed by compressive loading to fracture. Result and Conclusion: The result of marginal fit changes showed that GC group had the lowest marginal gap follow by VITA and Creation. While VITA group showed the highest fracture resistance follows by GC then Creation. Thermocycling process did not significantly reduce the load at fracture for all groups.

Influence of Different pH and Fluoride Addition on the Corrosion Behavior of the Sintered CoCr Alloy Ceramill Sintron Compared to the Cast Alloy Girobond NB

In addition to conventionally casting, dental metallic framework can be manufactured using different CAD/CAM technologies (selective laser melting, milling). The milling of porous CoCr blanks followed by sintering under protective gas is a new 2012 introduced dental technology called Ceramill Sintron. For this new material so far, there exist few studies on the corrosion behavior. The aim of this study was to investigate the influence of different pH values as well as fluoride additions on the corrosion behavior of the sintered CoCr alloy compared to the cast condition by electrochemical corrosion measurements according to ISO 10271.

PEEK Primary Crowns with Cobalt-Chromium, Zirconia and Galvanic Secondary Crowns with Different Tapers-A Comparison of Retention Forces.

In prosthetic dentistry, double crown systems have proved their suitability as retainers for removable partial dentures. However, investigations in this context, regarding polyetheretherketone, are scarce. Therefore, the aim of this study was to test the retention force (RF) between polyetheretherketone (PEEK) primary and cobalt-chromium (CoCr), zirconia (ZrO2) and galvanic (GAL) secondary crowns with three different tapers. Primary PEEK-crowns were milled with the tapers 0°, 1°, and 2° (n = 10/taper, respectively). Afterwards, 90 secondary crowns were fabricated: (i) 30 CoCr-crowns milled from Ceramill Sintron (AmannGirrbach, Koblach, Austria) (n = 10/taper), (ii) 30 ZrO2-crowns milled from Ceramill ZI (AmannGirrbach, Koblach, Austria) (n = 10/taper), and (iii) 30 GAL-crowns made using electroforming (n = 10/taper). RF was measured in a pull-off test (20 pull-offs/specimen) and data were analyzed using 2-/1-way Analysis of Variance (ANOVA) followed by the Tukey-Honestly Significant Difference (HSD) post hoc test and linear regression analyses (p < 0.05). The measured mean RF values ranged between 9.6 and 38.2 N. With regard to the 0°, 1°, and 2° tapered crowns, no statistically significant differences between CoCr and ZrO2 were observed (p > 0.141). At 0° taper, no differences in retention forces between GAL, CrCr, and ZrO2 crowns were found (p = 0.075). However, at 1° and 2° taper, lower RF for GAL-crowns were observed (p < 0.009, p < 0.001, respectively). According to this laboratory study, PEEK might be a suitable material for primary crowns, regardless of the taper and the material of secondary crown. Long-term results, however, are still necessary.

Shear bond strength of porcelain to a new millable alloy and a conventional castable alloy

Statement of problemA recently introduced presintered cobalt-chromium (Co-Cr) alloy for metal ceramic restorations can be efficiently processed with computer-aided design/computer-aided manufacturing (CAD/CAM) techniques. However, little or no reliable study data are available regarding the bonding ability of porcelain to milled Co-Cr alloys. PurposeThe purpose of this study was to evaluate the shear bond strength of veneering porcelain to the presintered Co-Cr alloy and to a conventional castable alloy. Material and methodsNinety-six cylindrical cores (6.8 mm in diameter, 9 mm in height) were made of millable alloy (Ceramill Sintron) and castable alloy (4-all) by means of CAD/CAM or casting, 48 cores for each alloy. Four types of veneering porcelain were fired or pressed to the cores; these specimens had dimensions of 4×4×3 mm. After firing, the specimens were put in resin molds, fixed in a universal testing machine, and subjected to a shear force test. Loading was applied to each specimen through the attached crosshead at a constant drive speed of 0.5 mm/min until fracture occurred. Shear bond strengths (MPa) were calculated by dividing the maximum failure force over the cross-sectional area of each specimen. Failure patterns of the specimens were also investigated and characterized as adhesive, cohesive, or mixed. One-way ANOVA and the Duncan post hoc test were used to analyze statistically significant differences between groups (α=.05). ResultsThe means of the shear bond strengths of (millable) Ceramill Sintron were similar to or higher than those of (castable) 4-all cores. The shear bond strength was significantly lower for Press-To-Metal veneer than for the other fired veneers in the test (P<.001). The pattern of failure in most specimens was mixed, except for Press-To-Metal veneer, where cohesive failure occurred. ConclusionsThe bonding ability of the traditional castable alloy was similar to that of the presintered millable Co-Cr alloy.