fluorapatite and feldspar

The aims of this study were to investigate the effects of two surface-conditioning methods on the shear bond strength (SBS) of metal brackets bonded to three different all-ceramic materials, and to evaluate the mode of failure after debonding. Twenty feldspathic, 20 fluoro-apatite, and 20 leucite-reinforced ceramic specimens were examined following two surface-conditioning methods: air-particle abrasion (APA) with 25 μm Al(2)O(3) and silica coating with 30 μm Al(2)O(3) particles modified by silica. After silane application, metal brackets were bonded with light cure composite and then stored in distilled water for 1 week and thermocycled (×1000 at 5-55°C for 30 seconds). The SBS of the brackets was measured on a universal testing machine. The ceramic surfaces were examined with a stereomicroscope to determine the amount of composite resin remaining using the adhesive remnant index. Two-way analysis of variance, Tukey's multiple comparison test, and Weibull analysis were used for evaluation of SBS. The lowest SBS was with APA for the fluoro-apatite ceramic (11.82 MPa), which was not significantly different from APA for the feldspathic ceramic (13.58 MPa). The SBS for the fluoro-apatite ceramic was significantly lower than that of leucite-reinforced ceramic with APA (14.82 MPa). The highest SBS value was obtained with silica coating of the leucite-reinforced ceramic (24.17 MPa), but this was not significantly different from the SBS for feldspathic and fluoro-apatite ceramic (23.51 and 22.18 MPa, respectively). The SBS values with silica coating showed significant differences from those of APA. For all samples, the adhesive failures were between the ceramic and composite resin. No ceramic fractures or cracks were observed. Chairside tribochemical silica coating significantly increased the mean bond strength values.

Topics: Adhesiveness; Aluminum Oxide; Aluminum Silicates; Apatites; Ceramics; Dental Alloys; Dental Bonding; Dental Etching; Dental Porcelain; Dental Stress Analysis; Humans; Materials Testing; Microscopy, Electron, Scanning; Orthodontic Brackets; Potassium Compounds; Resin Cements; Shear Strength; Silanes; Silicon Dioxide; Stress, Mechanical; Surface Properties; Temperature; Time Factors; Water

To evaluate the microhardness and surface elemental compositions of ceramics immersed in acidic agents.. Thirty-five ceramic disc specimens were made from each of four types of ceramic (VMK 95, Vitadur Alpha, Empress Esthetic and IPS e.max Ceram). Before immersion, baseline data of Vicker's microhardness and elemental composition were recorded. Four groups of discs (seven per group) were then immersed in acidic agents (citrate buffer solution, pineapple juice and green mango juice) and deionized water (as a control) for 168 h at 37 degrees C. One group was immersed in 4% acetic acid at 80 degrees C for 168 h. After immersion, specimens were evaluated and data were analyzed using two-way ANOVA with repeated measurements and a paired t-test at a significance level of 0.05.. The microhardness values of four types of ceramic significantly decreased after being immersed in acidic agents (p < 0.05). The elemental compositions of ceramics mainly comprise silicon, aluminium and potassium. These compositions also decreased after immersion (p < 0.05).. The acidic agents used in this study affected the microhardness and elemental dissolution of ceramics. The main elemental compositions of ceramics (silicon, aluminium and potassium) decreased after being immersed in acidic agents.

Topics: Acetic Acid; Acids; Aluminum; Aluminum Oxide; Aluminum Silicates; Ananas; Apatites; Beverages; Buffers; Citric Acid; Dental Porcelain; Hardness; Humans; Hydrogen-Ion Concentration; Immersion; Mangifera; Materials Testing; Potassium; Potassium Compounds; Silicon; Solubility; Spectrometry, X-Ray Emission; Surface Properties; Temperature; Time Factors; Water

Understanding the translucency of ceramic materials is important to achieve good esthetics. Ceramic thickness is related to translucency; however, less information about core-veneer thickness in combination is available.. The purpose of this study was to investigate the translucency parameters of core-veneer thicknesses in 2 different ceramic materials.. A total of 56 ceramic disks of different thickness were fabricated as cores according to the manufacturer's recommendations and divided into groups (n=7). Each was veneered with its compatible veneer ceramic with a different thickness (0.2, 0.5, 0.7 mm). One group of each ceramic type was left without veneer. The groups were named according to core names (group IPS e.max Press [EP], group IPS Empress Esthetic [EE]), and numbers were given according to thickness combination: 1=(1.00+0.5); 2=(0.8+0.7); 3=(1.00); 4=(0.8+0.2). All surfaces were measured by profilometry to ensure consistency within the groups. A glass disk (1.5 mm) positive control (group P) and a metal core (1.5 mm) negative control (group N) were prepared. The translucency parameter values were calculated by using spectrophotometry to calculate the color differences of the specimens over black and white backgrounds.. A 1-way ANOVA found significant differences among the translucency parameter values of the ceramic groups (P<.01). A 1-sample t test determined thickness consistency, and 1-way analysis was performed to ensure surface roughness consistency within the groups (P>.05).. Total ceramic thickness affected the translucency; higher combined ceramic thickness resulted in lower translucency parameter values. When total thickness decreases, the translucency of core material has more effect than that of veneer material on translucency parameter values.

Topics: Aluminum Silicates; Apatites; Ceramics; Color; Dental Alloys; Dental Porcelain; Dental Veneers; Esthetics, Dental; Glass; Humans; Light; Materials Testing; Nanostructures; Potassium Compounds; Spectrophotometry; Surface Properties

The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics.. The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed.. The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p < 0.05). However, the mean bond strengths significantly decreased in the connector groups (CE and CV) after thermal cycling (p < 0.05). The elemental analysis suggested diffusion of ceramic substances into the zirconia surface.. A glass-ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

Topics: Aluminum Silicates; Apatites; Ceramics; Chromium Alloys; Dental Bonding; Dental Materials; Dental Porcelain; Dental Stress Analysis; Dental Veneers; Diffusion; Humans; Materials Testing; Metal Ceramic Alloys; Microscopy, Electron, Scanning; Potassium Compounds; Shear Strength; Spectrometry, X-Ray Emission; Stress, Mechanical; Surface Properties; Temperature; Time Factors; Yttrium; Zirconium

To investigate the effect of surface polishing and finishing methods on the surface roughness of restorative ceramics.. Disk specimens were prepared from feldspar-based, lithium disilicate-based, fluorapatite leucite-based and zirconia ceramics. Four kinds of surface polishing/finishing methods evaluated were: Group 1:. carborundum points (CP); Group 2: silicon points (SP); Group 3: diamond paste (DP); Group 4: glazing (GZ). Surface roughness was measured using an interferometer and the parameters of Sa (average height deviation of the surface) and St (maximum peak-to-valley height of the surface) were evaluated. Data were statistically analyzed using two-way ANOVA (P < 0.05) followed by post-hoc test. The mean values were also compared by Student's t-test. Specimen surfaces were evaluated by 3-D images using an interferometer.. The zirconia showed the least surface roughness (Sa and St) values after grinding with carborundum points. The significantly lowest Sa values and St values were obtained for lithium disilicate and zirconia ceramics surfaces finished with DP and GZ. The fluorapatite leucite ceramic showed significantly reduced Sa and St values from DP to GZ. The feldspathic porcelain showed the highest surface roughness values among all types of ceramics after all of the polishing/finishing procedures.

Topics: Aluminum Silicates; Apatites; Carbon Compounds, Inorganic; Ceramics; Dental Materials; Dental Polishing; Dental Porcelain; Diamond; Humans; Interferometry; Materials Testing; Potassium Compounds; Silicon; Surface Properties; Zirconium

The purpose of this study is to evaluate the effects of multiple firings on the mechanical properties and microstructure of veneering ceramics used with zirconia frameworks.. Five different veneering ceramics for zirconia frameworks were used: Vintage ZR (ZR), Cerabien ZR (CZR), Vita VM9 (VM9), Cercon ceram KISS (KISS), IPS e.max ceram (e.max), and one veneering ceramic used for PFM frameworks: Vintage MP (MP). Twenty specimens were fabricated of each veneering ceramic. Ten specimens were fired twice and another ten specimens were fired ten times. Three-point flexural strength following the ISO 6872 and Vickers hardness were measured, and fracture toughness (K(IC)) was calculated. Density and porosity were determined. Specimens were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM).. For all materials, density increased and porosity decreased after 10 firings. Significant differences in density and porosity were observed between 2 and 10 firings, with the exception of VM9 (P<0.05). There were no significant differences in flexural strength between 2 and 10 firings except for MP. The Vickers hardness of ZR, VM9, KISS and MP increased significantly after 10 firings (P<0.001). There were no significant differences in fracture toughness for ZR, CZR, VM9 and MP between 2 and 10 firings. However, e.max underwent a significant increase in fracture toughness (P=0.000), and there was a significant decrease in the toughness of KISS after 10 firings (P=0.007).. Multiple firings could be effective for improving the densification and the hardness of veneering ceramics for zirconia restorations.. By 10 firings, the density and hardness of the veneering ceramics used with zirconia frameworks were raised, and porosity was reduced. However, no significant changes occurred in flexural strength, fracture toughness or microstructure.

Topics: Aluminum Oxide; Aluminum Silicates; Apatites; Ceramics; Crystallization; Dental Casting Technique; Dental Materials; Dental Porcelain; Dental Veneers; Elastic Modulus; Hardness; Hot Temperature; Humans; Materials Testing; Mechanical Phenomena; Microscopy, Electron, Scanning; Pliability; Porosity; Potassium Compounds; Silicon Dioxide; Stress, Mechanical; Surface Properties; Thermodynamics; X-Ray Diffraction; Zirconium

The objective of this study was to compare the effect of veneering porcelain (monolithic or bilayer specimens) and core fabrication technique (heat-pressed or CAD/CAM) on the biaxial flexural strength and Weibull modulus of leucite-reinforced and lithium-disilicate glass ceramics. In addition, the effect of veneering technique (heat-pressed or powder/liquid layering) for zirconia ceramics on the biaxial flexural strength and Weibull modulus was studied.. Five ceramic core materials (IPS Empress Esthetic, IPS Empress CAD, IPS e.max Press, IPS e.max CAD, IPS e.max ZirCAD) and three corresponding veneering porcelains (IPS Empress Esthetic Veneer, IPS e.max Ceram, IPS e.max ZirPress) were selected for this study. Each core material group contained three subgroups based on the core material thickness and the presence of corresponding veneering porcelain as follows: 1.5 mm core material only (subgroup 1.5C), 0.8 mm core material only (subgroup 0.8C), and 1.5 mm core/veneer group: 0.8 mm core with 0.7 mm corresponding veneering porcelain with a powder/liquid layering technique (subgroup 0.8C-0.7VL). The ZirCAD group had one additional 1.5 mm core/veneer subgroup with 0.7 mm heat-pressed veneering porcelain (subgroup 0.8C-0.7VP). The biaxial flexural strengths were compared for each subgroup (n = 10) according to ISO standard 6872:2008 with ANOVA and Tukey's post hoc multiple comparison test (p≤ 0.05). The reliability of strength was analyzed with the Weibull distribution.. For all core materials, the 1.5 mm core/veneer subgroups (0.8C-0.7VL, 0.8C-0.7VP) had significantly lower mean biaxial flexural strengths (p < 0.0001) than the other two subgroups (subgroups 1.5C and 0.8C). For the ZirCAD group, the 0.8C-0.7VL subgroup had significantly lower flexural strength (p= 0.004) than subgroup 0.8C-0.7VP. Nonetheless, both veneered ZirCAD groups showed greater flexural strength than the monolithic Empress and e.max groups, regardless of core thickness and fabrication techniques. Comparing fabrication techniques, Empress Esthetic/CAD, e.max Press/CAD had similar biaxial flexural strength (p= 0.28 for Empress pair; p= 0.87 for e.max pair); however, e.max CAD/Press groups had significantly higher flexural strength (p < 0.0001) than Empress Esthetic/CAD groups. Monolithic core specimens presented with higher Weibull modulus with all selected core materials. For the ZirCAD group, although the bilayer 0.8C-0.7VL subgroup exhibited significantly lower flexural strength, it had highest Weibull modulus than the 0.8C-0.7VP subgroup.. The present study suggests that veneering porcelain onto a ceramic core material diminishes the flexural strength and the reliability of the bilayer specimens. Leucite-reinforced glass-ceramic cores have lower flexural strength than lithium-disilicate ones, while fabrication techniques (heat-pressed or CAD/CAM) and specimen thicknesses do not affect the flexural strength of all glass ceramics. Compared with the heat-pressed veneering technique, the powder/liquid veneering technique exhibited lower flexural strength but increased reliability with a higher Weibull modulus for zirconia bilayer specimens. Zirconia-veneered ceramics exhibited greater flexural strength than monolithic leucite-reinforced and lithium-disilicate ceramics regardless of zirconia veneering techniques (heat-pressed or powder/liquid technique).

Topics: Algorithms; Aluminum Silicates; Apatites; Ceramics; Computer-Aided Design; Crystallization; Dental Porcelain; Dental Prosthesis Design; Dental Veneers; Elastic Modulus; Hot Temperature; Humans; Materials Testing; Pliability; Post and Core Technique; Potassium Compounds; Stress, Mechanical; Surface Properties; Yttrium; Zirconium

To determine the slow crack growth (SCG) and Weibull parameters of five dental ceramics: a vitreous porcelain (V), a leucite-based porcelain (D), a leucite-based glass-ceramic (E1), a lithium disilicate glass-ceramic (E2) and a glass-infiltrated alumina composite (IC).. Eighty disks (Ø 12 mm × 1.1mm thick) of each material were constructed according to manufacturers' recommendations and polished. The stress corrosion susceptibility coefficient (n) was obtained by dynamic fatigue test, and specimens were tested in biaxial flexure at five stress rates immersed in artificial saliva at 37 °C. Weibull parameters were calculated for the 30 specimens tested at 1 MPa/s in artificial saliva at 37 °C. The 80 specimens were distributed as follows: 10 for each stress rate (10(-2), 10(-1), 10(1), 10(2)MPa/s), 10 for inert strength (10(2)MPa/s, silicon oil) and 30 for 10(0)MPa/s. Fractographic analysis was also performed to investigate the fracture origin.. E2 showed the lowest slow crack growth susceptibility coefficient (17.2), followed by D (20.4) and V (26.3). E1 and IC presented the highest n values (30.1 and 31.1, respectively). Porcelain V presented the lowest Weibull modulus (5.2). All other materials showed similar Weibull modulus values, ranging from 9.4 to 11.7. Fractographic analysis indicated that for porcelain D, glass-ceramics E1 and E2, and composite IC crack deflection was the main toughening mechanism.. This study provides a detailed microstructural and slow crack growth characterization of widely used dental ceramics. This is important from a clinical standpoint to assist the clinician in choosing the best ceramic material for each situation as well as predicting its clinical longevity. It also can be helpful in developing new materials for dental prostheses.

Topics: Algorithms; Aluminum Oxide; Aluminum Silicates; Apatites; Ceramics; Crystallography; Dental Porcelain; Dental Stress Analysis; Elastic Modulus; Humans; Lithium Compounds; Materials Testing; Microscopy, Electron, Scanning; Pliability; Potassium Compounds; Saliva, Artificial; Spectrometry, X-Ray Emission; Stress, Mechanical; Surface Properties; Temperature; Tensile Strength; X-Ray Diffraction

This in vitro study investigated the null hypothesis that metal-free crowns induce fracture loads and mechanical behavior similar to metal ceramic systems and to study the fracture pattern of ceramic crowns under compressive loads using finite element and fractography analyses.. Six groups (n = 8) with crowns from different systems were compared: conventional metal ceramic (Noritake) (CMC); modified metal ceramic (Noritake) (MMC); lithium disilicate-reinforced ceramic (IPS Empress II) (EMP); leucite-reinforced ceramic (Cergogold) (CERG); leucite fluoride-apatite reinforced ceramic (IPS d.Sign) (SIGN); and polymer crowns (Targis) (TARG). Standardized crown preparations were performed on bovine roots containing NiCr metal dowels and resin cores. Crowns were fabricated using the ceramics listed, cemented with dual-cure resin cement, and submitted to compressive loads in a mechanical testing machine at a 0.5-mm/min crosshead speed. Data were submitted to one-way ANOVA and Tukey tests, and fractured specimens were visually inspected under a stereomicroscope (20×) to determine the type of fracture. Maximum principal stress (MPS) distributions were calculated using finite element analysis, and fracture origin and the correlation with the fracture type were determined using fractography.. Mean values of fracture resistance (N) for all groups were: CMC: 1383 ± 298 (a); MMC: 1691 ± 236 (a); EMP: 657 ± 153 (b); CERG: 546 ± 149 (bc); SIGN: 443 ± 126 (c); TARG: 749 ± 113 (b). Statistical results showed significant differences among groups (p < 0.05) represented by different lowercase letters. Metal ceramic crowns presented fracture loads significantly higher than the others. Ceramic specimens presented high incidence of fractures involving either the core or the tooth, and all fractures of polymer crown specimens involved the tooth in a catastrophic way. Based on stress and fractographic analyses it was determined that fracture occurred from the occlusal to the cervical direction.. Within the limitations of this study, the results indicated that the use of ceramic and polymer crowns without a core reinforcement should be carefully evaluated before clinical use due to the high incidence of failure with tooth involvement. This mainly occurred for the polymer crown group, although the fracture load was higher than normal occlusal forces. High tensile stress concentrations were found around and between the occlusal loading points. Fractographic analysis indicated fracture originating from the load point and propagating from the occlusal surface toward the cervical area, which is the opposite direction of that observed in clinical situations.

Topics: Aluminum Oxide; Aluminum Silicates; Animals; Apatites; Bisphenol A-Glycidyl Methacrylate; Cattle; Chromium Alloys; Composite Resins; Crowns; Dental Porcelain; Dental Stress Analysis; Dentin-Bonding Agents; Finite Element Analysis; Glass Ionomer Cements; Lithium Compounds; Materials Testing; Metal Ceramic Alloys; Polyethylene Glycols; Polymethacrylic Acids; Post and Core Technique; Potassium Compounds; Resin Cements; Silicate Cement; Stress, Mechanical; Tooth Fractures; Zinc Phosphate Cement

Acidic food and sour fruits and drinks have been investigated for their destructive effects on enamel. However, their effect on porcelain restorations has not been widely examined.. The purpose of this study was to evaluate the ion leaching of porcelains immersed in acidic agents.. Fifty-five discs (12.0 mm in diameter and 2.0 mm in thickness) were made from each of 4 types of porcelain (VITA VMK 95, Vitadur Alpha, IPS Empress Esthetic, and IPS e.max Ceram). Baseline data of elemental compositions of all storage agents were recorded. Four groups of discs (n=10) were then immersed in acidic agents (citrate buffer solution, pineapple juice, and green mango juice) and deionized water (control) at 37 degrees C for 168 hours. One group was immersed in 4% acetic acid at 80 degrees C for 168 hours. After immersion, fluids from all specimens for each acidic agent were measured for ion leaching with an inductively coupled plasma optical emission spectroscopy. Surface characteristics of specimens were examined using scanning electron microscopy (SEM). Data were analyzed using 3-way repeated ANOVA and Tukey HSD multiple comparisons (alpha=.05).. This study revealed that each type of porcelain had significantly leached the various ions to varying degrees after being immersed in acidic agents (P<.001 for all comparisons). SEM photomicrographs showed surface destruction of all porcelains.. Acidic agents used in this study affected elemental dissolution of the 4 types of porcelains evaluated.

Topics: Acetic Acid; Acids; Aluminum Oxide; Aluminum Silicates; Ananas; Apatites; Citric Acid; Dental Porcelain; Drug Storage; Hydrogen-Ion Concentration; Ions; Mangifera; Materials Testing; Potassium Compounds; Surface Properties

A wide variety of dental ceramics compositions have been introduced in dental clinical practice in order to combine desired aesthetics with superior mechanical performance. The aim of the present study was to investigate the microstructural changes in three dental ceramics after their sintering according to manufacturers' instructions and to comparatively evaluate some of their physical, mechanical and biological properties.. The analysis of the phases present in each material before and after sintering was performed with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD). The thermal properties of ceramic specimens were evaluated with differential thermal and thermogravimetric analysis (TG-DTA). The mechanical properties evaluated were fracture toughness, Young's modulus and microhardness with the Vickers indentation method. MTT assay was used for cell proliferation assessment. One-way analysis of variance (ANOVA) with Bonferroni multiple comparisons tests was used to determine statistically significant differences (significance level of p<0.05).. Results showed a remarkable variation among the three ceramic compositions of leucite content in the starting unheated ceramic powders ranging between 14 and 32 wt.% and in the respective sintered powders ranging between 15 and 41 wt.% The low fusing glass-ceramic and the high fusing leucite-based ceramic presented significantly higher fracture toughness (p<0.001) and microhardness and lower modulus of elasticity (p<0.05) compared to the low fusing feldspathic ceramic. The three ceramics were almost equivalent concerning their in vitro biological behavior.. Variations in crystal structure, distribution and composition are related to differences concerning mechanical properties of dental ceramics.

Topics: Aluminum Silicates; Apatites; Biocompatible Materials; Cell Proliferation; Cells, Cultured; Coloring Agents; Dental Porcelain; Dental Prosthesis Design; Differential Thermal Analysis; Elasticity; Fibroblasts; Glass; Hardness; Hot Temperature; Humans; Materials Testing; Metal Ceramic Alloys; Microscopy, Electron, Scanning; Periodontium; Potassium Compounds; Spectroscopy, Fourier Transform Infrared; Stress, Mechanical; Surface Properties; Tetrazolium Salts; Thermogravimetry; Thiazoles; X-Ray Diffraction