Search Results (154)

This in vitro study evaluated the effects of four surface treatments (no treatment, hydrofluoric acid [HF] etching, aluminum oxide [AlO] air abrasion, and tribochemical silica coating [TSC]) and two bonding agents (dedicated silane vs. silane-containing universal adhesive) on the microshear bond strength of four CAD/CAM glass-ceramic materials, including two zirconia-reinforced lithium silicate ceramics and two conventional glass-ceramics. Four CAD/CAM materials (Celtra Duo, IPS e.max CAD, IPS Empress CAD, and Vita Suprinity) were subjected to four surface treatments (no treatment, HF, AlO air abrasion, and TSC) and further divided according to bonding agent application: dedicated silane (Clearfil Ceramic Primer Plus) or silane-containing universal adhesive (Single Bond Universal). Microshear bond strength testing was performed after 24 h of water storage (n = 10). Failure modes were classified under stereomicroscopy, and surface topography was evaluated by SEM. Data were analyzed using three-way ANOVA and Tukey’s HSD test (α = 0.05). All three main factors and their interactions significantly affected bond strength values (p < 0.05; R² = 0.863). HF etching with silane produced the highest values for most materials. However, IPS Empress CAD treated with TSC and silane yielded the highest overall bond strength (25.2 MPa). Dedicated silane consistently outperformed the universal adhesive across all combinations. ZLS ceramics showed intermediate values with distinct etching patterns compared with conventional glass-ceramics. Optimal bonding protocols for CAD/CAM glass-ceramics are material-dependent. Dedicated silane application is recommended over silane-containing universal adhesives for maximum bond strength. Full article

This study extended a previously established intraoral scanning (IOS) and optical coherence tomography (OCT) dual-modality monitoring workflow for computer-aided design/computer-aided manufacturing (CAD/CAM) restorations to three additional crown material classes alongside a resin composite (RECO) reference. Four material classes were investigated ($n=8$ each): RECO, polymer-infiltrated ceramic network (PICN), lithium disilicate ceramic (LDSC), and zirconia-reinforced lithium silicate ceramic (ZLSC). Monolithic crowns were adhesively luted to standardized human molar abutment teeth and aged by cyclic loading (50500$\mathrm{N}$, 2$\mathrm{Hz}$, 37 2${}^{\circ }\mathrm{C}$, up to 1250000 cycles) in a mouth-motion simulator. IOS and handheld OCT were performed at baseline and after every 250000 cycles under phantom-head conditions; correspondence was assessed using Spearman’s rank correlation coefficient (exploratory, uncorrected for multiple comparisons). OCT consistently showed higher defect extents than IOS across all material classes and timepoints. While no significant IOS-OCT associations were found for RECO and the PICN, OCT detected full-thickness vertical subsurface damage propagation from the earliest timepoint in LDSC and ZLSC, with IOS-derived surface wear remaining markedly lower. Surface-based monitoring alone did not reliably reflect subsurface damage propagation, a dissociation most pronounced in the vertical dimension and silicate-based materials. Intraoral OCT may provide complementary, non-invasive subsurface information to support individualized recall scheduling and minimally invasive repair decisions. Full article

Objectives: In this in vitro study, we aimed to evaluate the effect of bur wear during grinding on the marginal gap of Zirconia Lithium Silicate (ZLS) single crowns. Methods: A single maxillary right canine typodont tooth, pre-prepared for a full ceramic crown, was scanned using an intra-oral scanner. A total of 32 ZLS crowns were ground using a four-axis grinding unit and divided into four equal groups (n = 8) based on the grinding sequence to represent progressive bur wear: Group 1 (crowns 1–8), Group 2 (crowns 9–16), Group 3 (crowns 17–24), and Group 4 (crowns 25–32). All crowns were ground consecutively using the same set of diamond burs. Each crown was temporarily cemented to the typodont tooth, and the marginal gap was measured at four reference points (buccal, palatal, mesial, distal) using scanning electron microscopy (SEM) at ×250 magnification. A Kolmogorov–Smirnov test performed on the study variables indicated a normal distribution (p > 0.05). Results: One-way ANOVA revealed no significant differences in the mean total marginal gap between the groups (p = 0.117), with values of 47.20 ± 5.16, 44.62 ± 7.23, 54.14 ± 10.02, and 48.53 ± 7.87 μm for Groups 1, 2, 3, and 4, respectively. Furthermore, no significant differences were found regarding a specific surface (distal, mesial, palatal, buccal) (p > 0.05). Conclusions: The cumulative wear of diamond burs after the consecutive grinding of 32 ZLS crowns did not significantly affect the marginal adaptation. All recorded marginal gaps were well within the clinically acceptable range (<120 μm). Full article

Increasing the durability and extending the lifespan of existing concrete structures are critical challenges in modern infrastructure maintenance. Lithium silicates have emerged as effective concrete densifiers due to their ability to improve surface hardness and resistance to degradation. However, their practical application is often hindered by difficulties in controlling the gelation process, which is crucial for their performance. This study explored the potential of alkali nitrates as gelation agents for lithium silicate systems. Multifaceted investigation of the gelation and ripening processes was conducted to provide deeper insights into the underlying mechanisms. Selected lithium silicate systems were then used to treat cementitious samples to evaluate their performance as concrete densifiers. Prepared silicate systems proved to be structurally stable and able to significantly reduce water penetration, especially in the early stages of water immersion. Full article

The aim of this study was to evaluate the influence of prosthetic substrate type, resin cement shade, and opaquer liner application on the translucency and color matching of translucent zirconia- and lithium-based ceramics. Four A2-shade zirconia materials (Katana HTML Plus, STML, UTML, and YML), with and without an opaquer liner, lithium disilicate ceramics (Amber Mill LT and HT), and zirconia-reinforced lithium silicate (Celtra Duo) were investigated. Monolithic crowns and standardized rectangular specimens were fabricated using CAD/CAM technology and cemented with neutral, warm-shade, and opaque try-in pastes onto A2-shade composite resin and cobalt–chromium substrates. Color measurements were performed using a digital colorimeter based on the CIE L*a*b* system. Translucency parameters (TPs) and color differences (ΔE) relative to the A2 reference shade were calculated. Lithium-based ceramics exhibited significantly higher translucency than zirconia materials. Application of the opaquer liner on intaglio surface of crowns reduced their translucency. On A2-shade substrates, translucent zirconia luted with neutral or warm-shade paste demonstrated the most favorable color compatibility. In contrast, opaque try-in paste resulted in clinically unacceptable color deviations and loss of optical depth. On metallic substrates, most materials exhibited pronounced gray discoloration and substantial color mismatch, particularly lithium disilicate ceramics. These findings indicate that ceramic type, substrate color, opaquer liner application, and resin cement shade significantly influence the optical performance and final color outcome of all-ceramic restorations. Full article

Deep brines represent important sources of strategic resources such as lithium and potassium, characterized by low exploration costs and high utilization rates. The Triassic strata in the Sichuan Basin contain abundant lithium- and potassium-rich brines, and understanding their origin is essential for exploring similar deposits. This study integrated field sampling and published data to systematically analyze the brines through hydrochemical testing, statistical methods, and water–rock reaction experiments, providing a comprehensive genetic interpretation based on hydrochemical features, element correlations, and characteristic coefficients. The results indicated that the brines are of the Cl–Na type, and both the sodium–chloride and chloride–bromide coefficients are consistent with a marine origin. Evapo-concentration was identified as the main controlling factor for ion enrichment, with subordinate influence from atmospheric precipitation. The common source of Ca²⁺ and Mg²⁺ likely includes the widespread marine carbonate rocks and/or the alteration of Ca–Mg-bearing silicate minerals (e.g., in green bean rocks or detrital layers) during brine–rock interaction. The desulfation coefficient indicated that lithium enrichment depends on a closed reducing environment, while potassium enrichment shows minimal correlation with brine confinement. Leaching experiments confirmed that green bean rocks serve as a key effective source rock for lithium and potassium, with elemental leaching efficiency positively correlated with fluid salinity. Based on these findings, a “dual-recharge” genetic model is proposed: paleo-marine brines undergoing deep circulation and meteoric water infiltrating along tectonic fractures collectively leached lithium and potassium from the green bean rocks, providing abundant lithium and potassium to the deep brines. This study refines the metallogenic mechanism of lithium- and potassium-rich brines in the Triassic Sichuan Basin and provides guidance for regional brine mineral exploration. Full article

Brines in playas and salt lakes provide crucial raw materials for potassium and lithium products in fertilizers and the energy sector. In this contribution, elemental and multiple H, O, Sr, B, and Li isotopic constraints were employed to determine the sources and origin of brines in the Bieletan Section (BLT) of Qarhan Salt Lake, northwestern China. The δD-δ¹⁸O results demonstrate that the brines of BLT mainly originated from river waters. The correlations of [Li] vs. [B], δ⁷Li vs. [Li] and δ¹¹B vs. [B]/[Cl] suggest that the original provenance and silicate weathering played important roles in the elemental and isotopic signatures of B and Li in these river waters, which had been obscured by evaporation and concentration of brines and the related precipitation and redissolution of salt minerals during the evolution of brines in the salt lake. Strontium isotopes rule out the recharge of CaCl₂ fluids from the northern fault zones for brines in BLT. Finally, the combination of elemental composition and Li, Sr, and B isotopes suggests that the current brine in BLT is mainly sourced from the Wutumeiren River and has experienced constant and intense evaporation to form the highly concentrated brine. By contrast, the contribution of the Golmud River/Tuolahai River and the CaCl₂ spring water from the north fault zone to the brines in BLT is negligible. Our results highlight that integrated elemental and multiple isotope analyses are more effective for achieving a precise and comprehensive understanding of the source-to-sink process in the river–salt lake system. Full article

The western region of the Tarim Basin is a typical deep and ultra-deep oil and gas reservoir with complex geological conditions in China. This area includes a thick salt–gypsum layer, high-pressure brine layers, and other formations with high pressures and a complex pressure system. These geological features present challenges such as a high risk of drilling fluid contamination by formation fluids, the deep burial of subsalt reservoirs, high temperatures, and difficulty in designing drilling fluids. In this paper, by systematically screening and optimizing key additives, a diesel oil-based drilling and completion fluid system resistant to 220 °C ultra-high temperatures with a density of 2.60 g/cm³ was developed. The overall performance was evaluated. Utilizing an independently developed high-temperature emulsifier (BZ-PSE), an organically modified lithium silicate viscosity modifier (BZ-CHT), and compounded fluid loss reducers (BZ-OLG/BZ-OSL), the system maintained excellent rheological stability (yield point > 4.3 Pa) and filtration control capacity (HTHP fluid loss < 4.8 mL) even after aging at 220 °C. The system demonstrated a resistance to contamination by 30–50% composite brines, 15% salt–gypsum cuttings, and 10% cement, proving its capability to effectively handle extremely thick mud shale, salt–gypsum layers, and high-pressure brine. Field tests were conducted in wells GL 3C, DB X, Boz 13X, and Boz 3X. The results indicated that the high-temperature, high-density diesel oil-based drilling fluids and completion fluids can effectively address the technical challenges posed by wellbore instability in thick salt–gypsum layers, high-pressure brine invasion, and performance degradation under ultra-high temperature conditions, providing reliable technical support for the safe and efficient drilling of similar complex formations. Full article

Background/Objectives: Marginal fit is a key determinant of the clinical performance of CAD/CAM (Computer-Aided DesignComputer-Aided Manufacturing) inlay restorations. This in vitro study compared the vertical marginal gap (VMG) of three chairside CAD/CAM inlay materials—VITA Enamic, CEREC Tessera, and Celtra Duo—using scanning electron microscopy (SEM) under a standardized digital workflow. Methods: Standardized Class I inlay preparations were performed in 15 extracted human molars (n = 5/material). Restorations were fabricated using a chairside workflow (Primescan intraoral scanning, CEREC 5.3 design, Primemill milling) followed by material-specific surface treatment and cementation with a self-adhesive resin cement. VMG was measured on SEM micrographs (500× for quantitative measurements; 200× for orientation) at three sites (mesial, central, distal), with three points per site (nine points/tooth; 135 point measurements). Triplicate points were averaged to site-level means and analyzed using a linear mixed-effects model (fixed effects: material, site, material × site; random intercept: tooth), Type II ANOVA, and Tukey-adjusted pairwise comparisons. Results: Mean VMG values were lowest for Celtra Duo (8.09 ± 1.98 µm), followed by VITA Enamic (27.90 ± 29.76 µm) and CEREC Tessera (32.72 ± 21.80 µm). The model indicated an overall effect of material (F(2,36) = 3.51, p = 0.040), whereas site and material × site effects were not significant. Tukey-adjusted pairwise comparisons did not reach statistical significance. Conclusions: Within the standardized chairside workflow evaluated, an overall material effect on VMG was detected, but pairwise separation was inconclusive in this sample with overlapping distributions. Celtra Duo showed smaller VMG values with narrower dispersion in overall per-tooth means, while VITA Enamic and CEREC Tessera showed wider and overlapping distributions; all group means were below commonly cited clinical acceptability ranges for marginal gap. Full article

Overlay restorations offer a conservative solution for teeth with substantial loss of tooth structure, but their success depends largely on the preparation design, material type, and fabrication technique. This study aimed to assess the effects of two different preparation designs and fabrication techniques on the fracture resistance and marginal adaptation of overlays fabricated from zirconia-reinforced lithium silicate (ZLS) and 3D-printed resin. Forty extracted human molars were randomly divided into two preparation design groups: occlusal reduction (O) and occlusal reduction with a round shoulder (OS). Each group was subdivided based on the material type: ZLS or 3D-printed resin (n = 10 per subgroup). Restorations were designed using CAD and manufactured using milling (ZLS) or additive manufacturing (3D-Printed). After cementation and thermomechanical aging (5500 cycles, 5–50 °C), marginal gaps were measured at 20 predefined points using scanning electron microscopy (SEM). The fracture resistance was tested using a universal testing machine. Data were analyzed using two-way ANOVA and post hoc tests (α = 0.05). The preparation design had a significant effect on both fracture resistance and marginal adaptation (p < 0.05). Group O showed significantly smaller marginal gaps than Group OS for both materials. The ZLS overlays exhibited a significantly higher fracture resistance than the 3D-printed resin overlays. All groups demonstrated marginal gaps within the clinically acceptable range (<120 μm). The fracture resistance and marginal adaptation of overlay restorations are significantly influenced by the preparation design and material type. A simpler occlusal reduction design results in better marginal adaptation, whereas round shoulder preparations provide a higher fracture resistance. Although the 3D-printed resin showed lower fracture resistance, its marginal adaptation was comparable to that of milled restorations, suggesting its potential as a conservative and cost-effective polymer composite alternative for digitally fabricated overlay restorations. Full article

This study investigated lithium beneficiation from nepheline syenite ore containing 242.57 ppm Li, identifying biotite as the primary lithium-bearing mineral. A high-intensity dry magnetic separation produced a pre-concentrate assaying at approximately 850–1000 ppm Li, and flotation tests were conducted on both the run-of-mine ore and this magnetic product. Flotation performance was systematically evaluated using two top sizes (−500 and −300 µm), six size fractions (−500 + 75, −500 + 53, −500 + 38, −300 + 75, −300 + 53, −300 + 38 µm), four pH values (2.5, 4.0, 6.5, 9.5), and three collectors (DAHC, Derna 7, and Der A4). Among the reagents, Der A4 yielded the most promising results. Optimization using sodium silicate as a depressant demonstrated that, at 20 g/t Der A4, 500 g/t Na₂SiO₃, and pH 4.0, the −300 + 75 µm fraction of the run-of-mine ore reached approximately 5300 ppm Li. Applying the same parameters to the magnetic pre-concentrate resulted in a 6326.46 ppm Li concentrate with roughly 80% of flotation recovery. Mineralogical characterization using MLA, XRD, modal mineralogy, and SEM-EDS confirmed that the optimized product consisted predominantly of biotite, accompanied by K-feldspar, nepheline, and albite. Liberation results showed high liberation levels and the free surface, supporting the efficiency of combining magnetic separation with flotation for upgrading nepheline syenite as a potential lithium resource. Full article

This study aimed to compare the translucency values of anterior crowns fabricated with ultra-high-translucent (UHT) zirconia, low-translucent (LT) lithium disilicate (LDS), and LT zirconia-reinforced lithium silicate (ZLS) glass-ceramics. In total, 48 central incisor crowns (n = 12) were fabricated from IPS e.max CAD LT (IPS), Celtra Duo LT (CD), and GC Initial UHT zirconia (GC, GC1). A standard of 1.5 mm labial thickness of the crowns was determined for three groups (IPS, CD, GC), and 1 mm labial thickness was determined for GC1. The crowns’ translucency values were assessed in terms of the contrast ratio (CR). One-way ANOVA and Tamhane tests were used for analyzing the data. The mean CRs of GC1, GC, IPS, and CD specimens were 0.13 ± 0.01, 0.22 ± 0.01, 0.22 ± 0.04, and 0.29 ± 0.04, respectively. The CD group had significantly higher CR values than the other groups. The difference between the CR values of GC and IPS groups was not statistically significant. The GC1 group’s CR was significantly lower than the GC group. It is critical to select monolithic materials in order to achieve esthetic restorations, particularly for anterior teeth. The translucency of monolithic restorative materials was influenced by the type and the thickness of the material used. Full article

The restoration of endodontically treated teeth remains a clinical challenge, particularly when substantial coronal tissue loss is present. Endocrowns fabricated using CAD/CAM technologies offer a conservative and esthetic alternative to conventional post-core systems; however, their long-term performance may be influenced by age-related mechanical and thermal stresses. This study evaluated the effect of thermomechanical aging on the marginal adaptation and fracture resistance of endocrowns fabricated from three CAD/CAM materials: zirconia-reinforced lithium silicate (ZLS), polyetherether ketone (PEEK), and 3D-printed resin. Sixty extracted human molars were endodontically treated and restored with endocrowns produced from these materials (n = 20 per group) and then subdivided into aged (n = 10) and control (n = 10) subgroups. Thermomechanical aging involved 5000 thermal cycles between 5 °C and 55 °C, and 75,000 mechanical loading cycles at 50 N. Marginal gaps were examined using scanning electron microscopy, and fracture resistance was tested under axial load at a crosshead speed of 0.5 mm/min. Data were analyzed using two-way ANOVA followed by Tukey’s post hoc test (α = 0.05). Thermomechanical aging significantly increased the marginal gaps in all materials (p < 0.05). The smallest marginal discrepancies were observed in the 3D-printed resin group, while the largest occurred in the ZLS after aging, likely due to dimensional changes during crystallization. Fracture resistance decreased in ZLS (−21.2%) and 3D resin (−20.9%) after aging (p < 0.05) but was not significantly affected in PEEK (−5.4%, p = 0.092). Thermomechanical aging adversely affects marginal adaptation across all materials, whereas its impact on strength is material-dependent. PEEK demonstrated the most stable mechanical performance and may represent a promising alternative for long-term endocrown restorations. Full article

The development of effective bone substitutes remains a central goal in regenerative medicine. In this study, lithium-modified bioglass-ceramics based on the 47.5S5 silicate oxide system were synthesized using the sol–gel method, followed by calcination and axial pressing to form cylindrical samples. These materials were sintered at 700 and 800 °C and subsequently examined to evaluate their structural, mechanical, and biological performance. Structural and microstructural analyses confirmed the presence of crystalline phases such as combeite (Na₆Ca₃Si₆O₁₈), NaLiSiO₄, Li₂SiO₃, and calcium silicates, indicating the successful incorporation of lithium within the glass-ceramic network. The bioceramics exhibited improved densification, deformability, and compressive strength with increasing sintering temperature. In vitro degradation in simulated body fluid revealed a consistent increase in mass loss with higher lithium content, suggesting enhanced resorbability linked to lithium oxide. Antibacterial testing indicated moderate antimicrobial activity, with slightly better results observed at higher sintering temperatures. Cell viability assays further supported the materials cytocompatibility. Taken together, these findings suggest that lithium substitution contributes positively to both mechanical robustness and biological behaviour, positioning these ceramics as promising bioresorbable bone substitutes with controlled degradation, suitable for bone tissue engineering where durability, bioactivity, and antimicrobial function are required. Full article

Lithium (Li) is a critical metal element in geothermal systems, yet its enrichment mechanism in coastal geothermal waters remains poorly understood. This study focuses on the Xiamen coastal geothermal system, located in the South China granitic reservoir at the front of the Pacific subduction zone. Self-organizing map (SOM) classification, hydrogeochemical analysis, hydrogen–oxygen isotopic constraints, and a three end-member mass balance model were applied to identify the sources and enrichment mechanisms of Li. The geothermal waters are classified into two types: inland low-TDS (Cluster-1) and coastal high-TDS (Cluster-2). Isotopic data indicate a mixture of meteoric water and seawater as the recharge source. The model shows that seawater and groundwater mixing accounts for 2–45% of Li concentration, with over 55% derived from the rock end-member. The leaching of 0.002–0.187 kg of granite per liter of geothermal water explains the observed Li levels. Elevated temperature and low pH enhance Li⁺ release from silicate minerals, and reverse cation exchange further amplifies this process. A strong positive correlation between the CAI-II index and Li⁺ concentration reveals a synergistic effect of ion exchange in high-salinity environments. Overall, the results provide a quantitative framework for understanding Li enrichment and evaluating resource potential in coastal geothermal systems. Full article