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Dental Materials : Official Publication... Nov 2019Yttria Partially Stabilised Zirconia (YPSZ) is a high strength ceramic which has become widely used in porcelain veneered dental copings due to its exceptional...
Investigations into the interface failure of yttria partially stabilised zirconia - porcelain dental prostheses through microscale residual stress and phase quantification.
OBJECTIVES
Yttria Partially Stabilised Zirconia (YPSZ) is a high strength ceramic which has become widely used in porcelain veneered dental copings due to its exceptional toughness. Within these components the residual stress and crystallographic phase of YPSZ close to the interface are highly influential in the primary failure mode; near interface porcelain chipping. In order to improve present understanding of this behaviour, characterisation of these parameters is needed at an improved spatial resolution.
METHODS
In this study transmission micro-focus X-ray Diffraction, Raman spectroscopy, and focused ion beam milling residual stress analysis techniques have, for the first time, been used to quantify and cross-validate the microscale spatial variation of phase and residual stress of YPSZ in a prosthesis cross-section.
RESULTS
The results of all techniques were found to be comparable and complementary. Monoclinic YPSZ was observed within the first 10μm of the YPSZ-porcelain interface with a maximum volume fraction of 60%. Tensile stresses were observed within the first 150 μm of the interface with a maximum value of ≈300 MPa at 50 μm from the interface. The remainder of the coping was in mild compression at ≈-30MPa, with shear stresses of a similar magnitude also being induced by the YPSZ phase transformation.
SIGNIFICANCE
The analysis indicates that the interaction between phase transformation, residual stress and porcelain creep at YPSZ-porcelain interface results in a localised porcelain fracture toughness reduction. This explains the increased propensity of failure at this location, and can be used as a basis for improving prosthesis design.
Topics: Dental Porcelain; Dental Prosthesis; Dental Stress Analysis; Dental Veneers; Materials Testing; Stress, Mechanical; Surface Properties; Yttrium; Zirconium
PubMed: 31522759
DOI: 10.1016/j.dental.2019.08.098 -
Journal of Prosthodontics : Official... Feb 2021To evaluate the flexural strength, elastic modulus, microhardness, and surface roughness of monolithic zirconia, lithium disilicate ceramics, and feldspathic ceramics...
PURPOSE
To evaluate the flexural strength, elastic modulus, microhardness, and surface roughness of monolithic zirconia, lithium disilicate ceramics, and feldspathic ceramics after being exposed to different acidic solutions.
MATERIALS AND METHODS
Rectangular specimens (n = 180) were prepared from three different ceramic materials: lithium disilicate, monolithic zirconia, and feldspathic porcelain. Initial Surface roughness of ninety specimens (n = 30/material) was evaluated using an optical noncontact profilometer. Thirty specimens of each material were immersed in one of the following solutions (n = 10/group): citric acid; acidic beverage; and artificial saliva, which served as the control. Post immersion surface roughness, flexural strength, and elastic modulus were determined using an optical noncontact profilometer and three-point bending test. Another thirty specimens of each material were immersed in the aqueous solutions (n = 10/group) following the same protocol and subjected to microhardness test using a Vickers diamond microhardness tester. A scanning electron microscope (SEM) was used to examine the surface characteristics changes. ANOVA and Post-hoc Tukey's Kramer tests were used for data analysis (α = 0.05).
RESULTS
Immersion in different solutions did not affect the flexural strength and elastic modulus of lithium disilicate or zirconia. Microhardness and surface roughness were significantly affected in all groups (p < 0.05). For feldspathic porcelain groups, the flexural strength and elastic modulus were significantly decreased in the citric acid group (p = 0.045 and p = 0.019). Also, there were significant differences among all feldspathic porcelain groups (p = 0.001) in terms of microhardness and surface roughness values.
CONCLUSIONS
The tested acidic agents significantly affected the flexural strength, elastic modulus, surface roughness, and microhardness of feldspathic porcelain. However, the flexural strength and elastic modulus of evaluated lithium disilicate and zirconia did not change significantly.
Topics: Ceramics; Computer-Aided Design; Dental Porcelain; Flexural Strength; Materials Testing; Surface Properties; Zirconium
PubMed: 32744393
DOI: 10.1111/jopr.13232 -
Journal of Prosthodontics : Official... Dec 2019To investigate the effect of bonding agent on the bonding strength between Co-Cr dental alloy, prepared by selective laser melting (SLM), and feldspathic porcelain.
PURPOSE
To investigate the effect of bonding agent on the bonding strength between Co-Cr dental alloy, prepared by selective laser melting (SLM), and feldspathic porcelain.
MATERIALS AND METHODS
The experiments were conducted according to ISO 9693 and the conventional protocols for the production of metal-ceramic dental restorations. After Al O air-particle abrasion, metal substrates of Co-Cr dental alloy specimens were bonded, using bonding agent (25 specimens), with dental porcelain positioned in layers (opaque, dentin, enamel). Control specimens (25) were also produced without bonding agent. Bonding strength was measured using 3-point bending tests, and the results were statistically analyzed using the t-test and Weibull statistics. Elemental (by SEM/EDS) and crystallographic analyses (by XRD) were conducted on the bonding agent, along cross sections of alloy-porcelain interfaces, and on fracture surfaces.
RESULTS
Cohesive fracture occurred (on the porcelain side). The application of the bonding agent decreased the average bonding strength (from 42.27 ± 5.85 to 36.25 ± 3.26 MPa, P = 0.00006), attributed to the nonexisting reaction between the TiO -rich bonding agent and the Co-Cr alloy, but it increased the Weibull modulus (from 7.84 to 12.16), which reflects the reliability of the bond in the tested metal-ceramic specimens.
CONCLUSIONS
Although the application of bonding agent slightly decreased the bonding strength, all the measured values of the metal-ceramic specimens produced by the SLM technique, with or without the bonding agent, are markedly higher than the minimum value required by ISO 9693 (25 MPa). Moreover, the use of bonding agent favors the increase of the Weibull modulus.
Topics: Ceramics; Chromium Alloys; Dental Bonding; Dental Porcelain; Materials Testing; Metal Ceramic Alloys; Reproducibility of Results; Surface Properties
PubMed: 30912204
DOI: 10.1111/jopr.13058 -
The Journal of Prosthetic Dentistry May 2022Materials have been developed to reduce the chipping of ceramic veneer and improve the esthetics of anterior ceramic veneered restorations. However, studies of the...
STATEMENT OF PROBLEM
Materials have been developed to reduce the chipping of ceramic veneer and improve the esthetics of anterior ceramic veneered restorations. However, studies of the effects of material and substructure design on fracture resistance are sparse.
PURPOSE
The purpose of this in vitro study was to investigate the fracture resistance of metal-ceramic (MC), zirconia-feldspathic porcelain (ZC), and zirconia-lithium disilicate (ZL) anterior restorations and evaluate the effect of material and substructure design.
MATERIAL AND METHODS
After preparing and scanning artificial maxillary central incisor teeth, titanium abutments and restoration specimens (n=90) were fabricated. MC, ZC, and ZL materials were prepared with substructure designs A (two-third coverage of the palatal surface) and B (one-third coverage of the palatal surface). After cementation, the specimens were thermocycled (10 000 cycles, 5 and 55 °C). Fracture load measurements, failure mode analysis, energy dispersive X-ray spectroscopy (EDS), line scan analysis, fractography, finite element analysis (FEA), and Weibull analysis were performed. Two-way ANOVA was used to identify the effects of material and substructure design on fracture load. One-way ANOVA was used to identify significant differences of fracture load (α=.05).
RESULTS
MC and ZL showed significantly higher fracture load than ZC (P<.05). MC_A showed a significantly higher fracture load than MC_B (P<.05). ZC_A exhibited the lowest Weibull modulus. FEA revealed that the maximum principal stress occurred near the loading area of the veneer. ZL displayed the lowest maximum principal stress among all the materials.
CONCLUSIONS
ZL and MC_A exhibited more favorable fracture resistance. The substructure design of MC, with increased metal coverage of the palatal surface, improved fracture resistance significantly.
Topics: Ceramics; Crowns; Dental Porcelain; Dental Prosthesis Design; Dental Restoration Failure; Dental Stress Analysis; Esthetics, Dental; Materials Testing; Zirconium
PubMed: 33390272
DOI: 10.1016/j.prosdent.2020.09.056 -
Odontology Apr 2024This study aims at evaluating the effect of simulating porcelain firing on the microstructure, corrosion behavior and mechanical properties of a Co-Cr-Mo alloy...
This study aims at evaluating the effect of simulating porcelain firing on the microstructure, corrosion behavior and mechanical properties of a Co-Cr-Mo alloy fabricated by Metal Soft Milling (MSM). Two groups of Co-28Cr-5Mo specimens (25 × 20 × 3 mm) were prepared by MSM: The as-sintered (AS) specimens and the post-fired (PF) specimens that were subjected to 5 simulating porcelain firing cycles without applying the ceramic mass onto their surface. Phase identification by X-ray Diffraction (XRD), microstructure examination by optical microscopy and Scanning Electron Microscopy combined with Energy-Dispersive X-ray Spectroscopy (SEM/EDX), corrosion testing by cyclic polarization and chronoamperometry in simulated body fluid (SBF), the latter test accompanied by Cr and Cr detection in the electrolyte through the 1.5-diphenylcarbazide (DPC) method and UV/visible spectrophotometry, and mechanical testing by micro-/nano-indentation were conducted to evaluate the effect of the post-firing cycles on the properties of Co-Cr-Mo. The results were statistically analyzed by the t test (p < 0.05: statistically significant). All specimens had a mixed γ-fcc and ε-hcp cobalt-based microstructure with a dispersion of pores filled with SiO and a fine MC intergranular presence. PF led to an increase in the ε-Co content and slight grain coarsening. Both AS and PF alloys showed high resistance to general and localized corrosion, whereas neither Cr nor Cr were detected during the passivity-breakdown stage. PF improved the mechanical properties of the AS-alloy, especially the indentation modulus and true hardness (statistically significant differences: p = 0.0009 and 0.006, respectively). MSM and MSM/simulating-porcelain firing have been proven trustworthy fabrication methods of Co-Cr-Mo substrates for metal-ceramic prostheses. Moreover, the post-firing cycles improve the mechanical behavior of Co-Cr-Mo, which is vital under the dynamically changing loads in the oral cavity, whereas they do not degrade the corrosion performance.
Topics: Chromium Alloys; Metal Ceramic Alloys; Dental Porcelain; Corrosion; Silicon Dioxide; Surface Properties; Materials Testing
PubMed: 37642767
DOI: 10.1007/s10266-023-00849-2 -
British Dental Journal Jan 2022This is the first part of a six-part series exploring the main ceramic materials used for the fabrication of all-ceramic, indirect restorations to aid clinicians in...
This is the first part of a six-part series exploring the main ceramic materials used for the fabrication of all-ceramic, indirect restorations to aid clinicians in their selection. We have detailed the history of how dental ceramics were introduced and how they have been revolutionised with the help of improvements within technology and understanding of the material. Dental ceramics can be classified in a few ways. One way is according to their ratio of glass to crystalline content and the other is how it is processed. Having a good in-depth understanding of this will allow clinicians to make the best decision for their patients who require ceramic restorations. This article aims to explore all the above to aid clinicians in making that decision.
Topics: Ceramics; Dental Materials; Dental Porcelain; Glass; Humans
PubMed: 35031736
DOI: 10.1038/s41415-021-3818-x -
Layering of discolored substrates with high-value opaque composites for CAD-CAM monolithic ceramics.The Journal of Prosthetic Dentistry Jul 2021Severely discolored substrates have been shown to limit the use of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic blocks because they provide...
STATEMENT OF PROBLEM
Severely discolored substrates have been shown to limit the use of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic blocks because they provide insufficient color masking.
PURPOSE
The purpose of the in vitro study was to evaluate the effect of a layer of high-value opaque composite resin over discolored substrates to determine its masking ability with CAD-CAM ceramics.
MATERIAL AND METHODS
Six ceramic groups (n=10) were tested. A bilayer group of zirconia and porcelain served as the control. The CAD-CAM monolithic groups were translucent zirconia, zirconia-reinforced lithium silicate, lithium disilicate, leucite-reinforced glass-ceramic, and feldspathic ceramic. Five substrates were used: A1 (used as reference), A3.5, C4, and coppery and silvery metals. The substrates were separated as nonlayered or layered (with flowable or restorative opaque composite resins). The tested luting agents were white, opaque, and A1. Color differences (ΔE) were assessed with the CIEDE2000 formula. A 2-way ANOVA (α=.05) was used to detect significant differences in ΔE among the groups for each substrate. The results were compared with acceptability (1.77) and perceptibility (0.81) thresholds.
RESULTS
The flowable composite resin layer associated with A1 luting agent ensured ΔE lesser the than perceptibility thresholdwith the use of CAD-CAM monolithic ceramics, with the lowest values for zirconia-reinforced lithium silicate in substrates A3.5 (0.53) and C4 (0.32) and for leucite-reinforced glass-ceramic for coppery (0.49) and silvery (0.81) substrates (P<.001). The same benefit was observed when zirconia and porcelain was tested over the silvery substrate. The absence of substrate treatment only provided ΔE lesser than the acceptability threshold with CAD-CAM ceramics for the A3.5 background.
CONCLUSIONS
The application of a flowable opaque composite resin and the use of a shaded luting agent ensure masking with CAD-CAM monolithic ceramics.
Topics: Ceramics; Color; Computer-Aided Design; Dental Porcelain; Materials Testing; Surface Properties
PubMed: 34052029
DOI: 10.1016/j.prosdent.2021.03.034 -
Journal of Prosthodontic Research Oct 2020Porcelain fused to zirconia prostheses are widely used, but porcelain chipping, fracture, spalling and delamination are common clinical problems. Conventional bond...
PURPOSE
Porcelain fused to zirconia prostheses are widely used, but porcelain chipping, fracture, spalling and delamination are common clinical problems. Conventional bond strength testing is inherently unsuited for studying interfacial failure by cracking in brittle materials. Instead, fracture toughness is a more meaningful parameter because it can assess the robustness of the interface when subjected to loading, but fracture mechanics approaches have only rarely been used. Our purpose was to develop a novel, simple, 3-point flexural methodology and mathematical analysis to measure the fracture toughness of the porcelain to zirconia interface.
METHODS
Equations were derived to estimate the fracture toughness of the bond by computing the interfacial energy release rate for a novel simple 3-point flexural test model. The test was validated using two different configurations of layered zirconia/porcelain beams (n = 10), approximating the dimensions of a fixed dental prosthesis, fabricated from a tetragonal polycrystalline zirconium dioxide partially stabilized with yttria and a feldspathic dental porcelain.
RESULTS
Cracking along the bimaterial interface was produced and measured as a discrete event. Fracture toughness means (standard deviations) computed from the measured energy release rate, for the porcelain to zirconia interface in two different specimen configurations were 7.9 (1.3) and 5.3 (1.6) J/m.
CONCLUSIONS
Equations were derived to measure interfacial fracture toughness of brittle materials using a novel simple 3-point flexural test method. The test was then validated; estimates for the fracture toughness for the porcelain to zirconia bond, overlapped with previously published data derived from more complex 4-point notched tests.
Topics: Dental Porcelain; Dental Stress Analysis; Dental Veneers; Materials Testing; Stress, Mechanical; Surface Properties; Zirconium
PubMed: 32063538
DOI: 10.1016/j.jpor.2019.11.002 -
Clinical Oral Investigations Sep 2023Ceramic-sintering affects bond strength and longevity of metal-ceramic. This study investigated the effect of sintering temperatures and times on metal-ceramic bond...
OBJECTIVES
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.
MATERIALS AND METHODS
One hundred eighty rectangular-shaped (25 × 8 × 1 mm) 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 (1 min; (HN)), increased (2 min; (HI)), and extremely increased (3 min; (HE)) sintering time (n = 10/group). Pre-cracked was subjected to four loading-unloading cycles at 0.05 mm/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).
RESULTS
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.
CONCLUSIONS
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.
CLINICAL RELEVANCE
MA offers stronger bond than CA. Enhancing bond is suggested by extended sintering. Raising temperature can enhance bond for CA, not for MA.
Topics: Dental Porcelain; Metal Ceramic Alloys; Dental Bonding; Surface Properties; Ceramics; Chromium Alloys; Materials Testing
PubMed: 37462729
DOI: 10.1007/s00784-023-05157-1 -
Journal of Indian Prosthodontic Society 2021To find and compare the qualitative and quantitative change in color and surface texture of feldspathic ceramic, pressable ceramic and ceramic used in computer-aided...
A comparative study on the effect of polishing systems on the color and surface texture of different porcelain systems - feldspathic, pressable, and computer-aided design/computer-aided manufacturing.
AIM
To find and compare the qualitative and quantitative change in color and surface texture of feldspathic ceramic, pressable ceramic and ceramic used in computer-aided design/computer-aided manufacturing CAD/CAM after different surface treatments namely glazing, abrading and polishing. To compare the effectiveness of pearl finish polishing paste and Soflex polishing system used in the study.
SETTING AND DESIGN
In-vitro, comparative study.
MATERIALS AND METHODS
Disc-shaped feldsapathic, pressable, CAD/CAM ceramic specimens were fabricated. Surface roughness and color parameters Δ L*, Δa*, and Δ b* were measured before glazing, after glazing, after abrasion with 02 diamond bur and after polishing with two different polishing systems. Surface roughness was measured qualitatively using scanning electron microscopy and quantitatively using an optical profilometer. The value of color parameters was obtained using a colorimeter. Data were statistically analyzed with ANOVA.
STATISTICAL ANALYSIS USED
SPSS software 20.0 version (IBM, New York, United states of America).
RESULTS
Unglazed feldspathic, pressable and CAD/CAM porcelain specimens showed a mean surface roughness value of 2.73 ± 0.38, 3.54 ± 1.42, and 3 ± 1.74 specimens. After glazing and polishing, the surface roughness values decreased. After abrasion, surface roughness values increased. Polishing did not alter the color along the red green axis and yellow blue axis.
CONCLUSIONS
Abraded specimens of feldspathic, pressable and CAD/CAM after polishing using pearl finish polishing paste and Soflex disc became smoother than glazed specimens. When pearl finish polishing paste and Soflex discs were compared for their effectiveness the former appeared to be more superior but not to a significant level. Mechanically altering feldspathic, pressable, and porcelain used in CAD/CAM technology does not cause any change in shade.
Topics: Ceramics; Computer-Aided Design; Dental Porcelain; Humans; Materials Testing; Surface Properties
PubMed: 33938867
DOI: 10.4103/jips.jips_425_20