The surface treatment of glass-ceramic-based materials, namely, lithium disilicate glass (IPS e.max CAD), feldspar porcelain (VITABLOCS Mark II), and a polymer-infiltrated ceramic network (VITA ...ENAMIC), using aqueous fluoride solutions and their influence on luting agent bonding were investigated. Six experimental aqueous fluoride solutions were applied to these materials, and their effects were assessed by surface topological analysis. The obtained results were compared using non-parametric statistical analyses. Ammonium hydrogen fluoride (AHF) etchant demonstrated the greatest etching effect. Subsequent experiments focused on evaluating different concentrations of the AHF etchant for the bonding pretreatment of glass-ceramic-based materials with a luting agent (PANAVIA V5). AHF, particularly at concentrations above 5 wt%, effectively roughened the surfaces of the materials and improved the bonding performance. Notably, AHF at a concentration of 30 wt% exhibited a more pronounced effect on both etching and bonding capabilities compared to hydrofluoric acid.
This study was to evaluate the effect of different water amounts and hydrolysis times of silane coupling agent on shear bond strength between lithium disilicate glass ceramic (LDS) and composite ...resin. Fourteen groups (n=7) of different water amounts (90, 50 and 10%v/v) and hydrolysis times (5, 19, 75 and 300 s) of experimental silane coupling agent that were prepared for silanization, non-silanization and commercial silane coupling agent (CSC) groups. Two-way analysis of variance (ANOVA) revealed no interaction between water amounts and hydrolysis times of ESC on shear bond strength between LDS and composite resin. One-way ANOVA exhibited the highest shear bond strength and the highest mean percentage in mixed failure mode in the 50%v/v group. Molecular analysis of 13C and 29Si indicated that nuclear magnetic resonance spectra of M2 and M3 hydrolysis species were found in 50%v/v group. The presenting of M2 and M3 which was predominant factor contributing to the highest shear bond strength.
•Fast scanning calorimetry is used to measure Tf of melts up to 5000 K s − 1.•Universal shift factor is provided for strong and fragile glass-forming systems.•Viscosity of melts prone to crystallize ...is derived by DSC over 6 orders of magnitude.
A gap in viscosity data spreads between glass transition and liquidus temperature for glass compositions, which are prone to crystallization. Alternatively, differential scanning calorimetry (DSC) is used to calculate viscosity as both the cooling rate in a DSC experiment and the shear viscosity at the fictive temperature are related by a constant shift factor. However, the low cooling rate (≤ 30 K min−1) of conventional calorimeters limits the accessible range of viscosities around 1012 Pa s. This study reports on measurements using a Flash DSC (FDSC) with cooling rates up to 3 × 105 K min−1. Under such extreme conditions, the fictive temperature is shifted considerably to higher temperatures and viscosity is accessible down to the softening point (viscosity = 106.6 Pa s) without the occurrence of crystallization during measurements. We provide a composition-independent shift factor to retrieve the viscosity of silicate and fluorophosphate melts over six orders of magnitude.
Objectives
To compare the strength and translucency of CAD/CAM zirconia blocks, with traditional and high‐speed sintering, to lithium disilicate.
Materials and Methods
Three zirconia materials ...(Katana STML Block, Prettau Anterior, and Zpex Smile) were tested with either traditional (7 hours) or high‐speed (18 or 30 minutes in a SpeedFire furnace) sintering. A lithium disilicate material (IPS e.max CAD) was tested as a reference. Three‐point bend flexural strength specimens (16 mm × 4 mm × 1.2 mm, n = 10) were tested on 14‐mm‐separated supports and loaded to failure at 1 mm/min. Specimens (1 mm thick, n = 10) were measured in a Color‐i7 spectrophotometer against a black and white background to calculate translucency parameter. Zirconia specimens were thermally etched and a grain structure was observed with scanning electron microscopy. Data were analyzed with 1‐way ANOVA and Tukey's post hoc analysis (α = 0.05).
Results
There were significant differences between materials for flexural strength, translucency parameter, and grain size (P < .001). Grains became significantly larger and pores were present when two of the zirconia materials (Prettau Anterior and Zpex Smile) were sintered with a high‐speed sintering program.
Conclusions
Two of the zirconia materials (Prettau Anterior and Zpex Smile) became less translucent and less strong using a high‐speed sintering program, whereas another (Katana STML Block) was unaffected.
This study aims to investigate the influence of heat treatment temperatures on the mechanical properties and chemical solubility (CS) of lithium disilicate‐fluorcanasite glass‐ceramics and to develop ...new dental materials. The glasses and glass‐ceramics were prepared using CaF2‐SiO2‐CaO‐K2O‐Na2O‐Li2O‐Al2O3‐P2O5‐based glass system using a conventional melt quenching method followed by a two‐stage crystallization process. This two‐stage method involves two heating temperature steps: first at a constant temperature (TS1) of 600°C and second step at varying temperatures (TS2) of 650, 700, 750, and 800°C. The crystallization behavior, phase formation, microstructure, translucency characteristic, density, hardness, fracture strength, and CS were investigated. It was found that the lithium disilicate crystal acted as the main crystalline phase, and the crystalline phase of fluorcanasite occurred at the heat treatment temperatures of 750 and 800°C. In addition, it was found that density, hardness, fracture strength, and CS increased while the translucency values decreased with increasing heat treatment temperatures. Furthermore, the CS increased dramatically when the fluorcanasite phases occurred in the glass‐ceramic samples. The maximum density values, Vickers hardness, fracture toughness, and flexural strength are 2.56 g/cm3, 6.73 GPa, 3.38 MPa.m1/2, and 259 MPa, respectively. These results may offer a possibility to design a new material for dental applications based on lithium disilicate‐fluorcanasite glass‐ceramics.
•Effect of the annealing temperature and time on pre-nucleation stages of lithium disilicate glass was investigated.•The short and medium range-orders were affected by the annealing conditions.•After ...annealing at temperatures close to the Tg, local arrangements were identified with those corresponding to crystalline phases of lithium disilicate and lithium metasilicate.
Annealing of glasses at temperatures close to Tg is a usual procedure to reduce internal stresses induced by the conventional melting/quenching process. In this work, the effect of the annealing temperature and time on short-range order of lithium disilicate glass was investigated. The total structure factor and radial distribution function of annealed samples at distinct temperatures and times were derived from synchrotron XRD measurements. The results suggest that short and medium range-orders were affected by the annealing conditions, even for temperatures well below the glass transition temperature, Tg. After annealing at temperatures close to Tg, local arrangements were identified with those corresponding to crystalline phases of lithium disilicate and lithium metasilicate. For temperatures below Tg, the diffusion of lithium atoms was already taking place, while the rearrangements of the SiO4 tetrahedra from the network former started to happen for temperatures close to or higher than Tg.
•We examine the effect of SiO2/Li2O on the properties of lithium disilicate (LD) glass-ceramics containing lithium tantalate (LT).•The LT/LD ratio from X-ray diffraction peak counts increased in the ...material as SiO2/Li2O decreased, validating the proposed reaction equation.•Various properties were examined, and higher LT content led to increased radiopacity.
Our previous work proposed a phase reaction equation for the current lithium disilicate (LD) glass-ceramic system containing lithium tantalate (LT) as a secondary phase: 2(Li2SiO3) + Ta2O5 → Li2Si2O5 + 2(LiTaO3). The present study had a goal of finding support for the proposed equation by examining the effect of the ratio of SiO2 to Li2O on the phase assemblage and microstructure of this system. The study also examined the microstructural effects on several properties of this system. A 15-sample data set was created by designing three microstructures for each of the five compositions. It was found that the LT/LD ratio from X-ray diffraction peak counts, as well as from Rietveld refinement, increased in the material as SiO2/Li2O decreased, supporting the proposed reaction equation. As SiO2/Li2O decreased, bulk density and CTE increased, while L* (lightness vs darkness) and Knoop hardness values decreased. The microstructure had little effect on radiopacity, but the addition of extra Ta2O5 into the composition lead to increased radiopacity values.
Lithium disilicate glass-ceramics show great potential in the fabrication of anisotropic structures due to their high-strength needle-form crystalline phase subjective to processing-induced ...alignment. Here we explore this strategy by focusing on the mechanistic aspects of fracture. Through different variations of the fracture toughness test we demonstrate the effect of bulk crystal orientation on fracture energy, toughening mechanisms, crystal size and aspect ratio. Using the anisotropic Poisson's ratio of the Li2Si2O5 crystal phase obtained by Resonant Ultrasound Spectroscopy, we apply the new geometry factor developed by Strobl et al. to provide a more accurate insight into the anisotropic crack propagation behavior in LS2 glass-ceramics. Raman spectra and X-Ray Diffraction patterns are resolved for the Li2Si2O5 phase aligned at plane parallel, anti-plane and random orientations.
We show that Li2Si2O5 crystallites oriented perpendicular to the crack growth plane tended to induce large scale crack deflection unless the crack was forced into a straight path, thereby promoting crystallite fracture, increased KIc-values and accentuated R-curve behavior. Crystal aspect ratio and residual stresses in the glass have been identified as important influencing factors on crack growth behavior and toughening mechanisms.
•Lithium disilicate (LS2) glass-ceramics were used to demonstrate the effect of crystal alignment on mode-I fracture toughness;•Li2Si2O5 crystallites were aligned in different orientations to the crack plane by pressing the LS2 melt using two different pressing strategies;•The use of a variety of specimen geometries and loading conditions allowed an insight into their R-curve behaviors;•The effect of residual stresses in the glass and the crystallite aspect ratio was determined;•Crystallites oriented perpendicular to the crack plane showed increased fracture resistance.
Physical aging of lithium disilicate glass Lancelotti, Ricardo F.; Cunha, Thiago R.; Kurtovic, Marcelo A.C. ...
Journal of non-crystalline solids,
12/2023, Letnik:
622
Journal Article
Recenzirano
Refractive index measurements were used to probe the structural relaxation behavior during the physical aging of a lithium disilicate glass at temperatures below the glass transition. The structural ...relaxation process was recorded using a single sample, starting from 5 K below the initial fictive temperature (Tf) of 720 K and gradually lowering it by 5 K increments until reaching an impractical experimental time to obtain complete relaxation at Tf − 35 K. The aging curves exhibited a stretched exponential relaxation behavior characteristic of glassy systems and showed good reproducibility in relaxation kinetics at three temperatures. A long continuous aging experiment conducted at 705 K demonstrated that the interruptions between isothermal treatments and property determinations did not affect the results. Finally, it was impossible to complete all experiments with the same sample, as after several cycles of cumulative relaxation experiments, the glass began to crystallize with the appearance of a small fraction of lithium disilicate crystals. This result indicates a relationship between structural relaxation and crystallization, corroborating recent studies in the literature.
To evaluate retrospectively the longevity of lithium disilicate ceramic (LidiSi) vs. laboratory-processed resin-based composite (RBC) inlay/onlay/overlay restorations and risk factors associated with ...restoration deficiencies and failures.
Patients (n = 91) receiving LidiSi (73.1%) and RBC (36.9%) inlays/onlays/overlays between 2007 and 2017 were selected. The restorations were evaluated using the modified U.S. Public Health Service criteria. The survival of the restorations was analyzed using the Kaplan-Meier method and log rank test. Factors affecting the occurrence of deficiencies were examined by logistic regression analysis. This was performed with the use of the Generalized Estimating Equation model including Repeated measurements (GEER), with the consideration that the same patient had several teeth in the sample. Risk estimation was conducted for each evaluated criterion (p < 0.05).
The survival of LidiSi and RBC restorations were 96.8% and 84.9%, respectively after a mean observation period of 7.8 ± 3.3 years. The annual failure rate was 0.2% for LidiSi and 1.0% for RBC. The probability of survival was above 98% for both restorations in the first 6 years, however, it dropped to 60% for RBC by the end of the 15th year. For both materials the reasons for failure included secondary caries, restoration fracture, and endodontic complication. In addition, LidiSi also failed due to tooth fracture, while RBC due to marginal gap formation and loss of retention. Among the evaluated risk factors, material of restoration (OR=6.8, CI95%:3.1–14.9), oral hygiene (OR=8.0, CI95%: 2.9–22.1, and bruxism (OR=1.9, CI95%: 1.1–3.3) showed a significant impact on the evaluated criteria.
LidiSi and RBC restorations showed similarly excellent 6-year survival, however, in the long term significantly more failures should be expected for RBCs.
