Search Results (394)

Background: This study investigated a new multi-acid-etching formulation for zirconia ceramics, containing hydrochloric, hydrofluoric, nitric, orthophosphoric, and sulfuric acids. The solution was tested on polycrystalline (5Y-TZP zirconia), lithium disilicate, hybrid ceramic, and feldspathic porcelain to assess compatibility, etching selectivity, and surface conditioning. Methods: Two-hundred-and-forty CAD/CAM specimens were etched for 20 s, 60 s, 30 min, or 1 h, and their surface roughness and etching patterns ware evaluated using 3D optical profilometry and scanning electron microscopy (SEM). Results: A positive correlation was observed between etching time and surface roughness (Ra values). The most pronounced changes were observed in lithium disilicate and feldspathic porcelain, with Ra values increasing from 0.733 ± 0.082 µm (Group 5) to 1.295 ± 0.123 µm (Group 8), and from 0.902 ± 0.102 µm (Group 13) to 1.480 ± 0.096 µm (Group 16), respectively. Zirconia increased from 0.181 ± 0.043 µm (Group 1) to 0.371 ± 0.074 µm (Group 4), and the hybrid ceramic from 0.053 ± 0.008 µm (Group 9) to 0.099 ± 0.016 µm (Group 12). Two-way ANOVA revealed significant effects of material and etching time, as well as a significant interaction between the two factors (p < 0.001). SEM observation revealed non-selective etching pattern for the lithium disilicate groups, indicating a risk of over-etching. Conclusions: The tested etching solution increased surface roughness, especially for the lithium disilicate and feldspathic porcelain specimens. In zirconia, one-hour etching improved surface characteristics with minimal observable damage. However, additional studies are necessary to validate the mechanical stability and bond effectives of this approach. Full article

Background/Objectives: Additive manufacturing (AM) technology has emerged as an innovative approach in dentistry. Recently, manufacturers have developed permanent resins engineered explicitly for the fabrication of definitive prostheses using AM techniques. This systematic review evaluated the mechanical and physical properties of 3D-printed permanent resins in comparison to milled resins and hybrid ceramics for the fabrication of indirect dental restorations. Methods: Three electronic databases—Scopus, Web of Science, and PubMed—were searched for English-language articles. Two independent researchers conducted study selection, data extraction, quality assessment, and the evaluation of the certainty of evidence. In vitro studies assessing the mechanical and physical properties of the permanent resins were included in this review. Results: A total of 1779 articles were identified through electronic databases. Following full-text screening and eligibility assessment, 13 studies published between 2023 and 2024 were included in this qualitative review. The investigated outcomes included physical properties (surface roughness, color changes, water sorption/solubility) and mechanical properties (flexural strength, elastic modulus, microhardness). Conclusions: Three-dimensionally printed permanent resins show promising potential for fabricating indirect dental restorations. However, the current evidence regarding their mechanical and physical properties remain limited and inconsistent, mainly due to variability in study methodologies. Full article

Cement-based building materials usually exhibit weak flexural behavior under high temperature or fire conditions. This paper develops a novel geopolymer with enhanced residual flexural strength, incorporating fly ash/metakaolin precursors and corundum aggregates based on our previous study, and further improves flexural performance using hybrid fibers. The flexural load–deflection response, strength, deformation capacity, toughness and microstructure are investigated by a thermal exposure test, bending test and microstructure observation. The results indicate that the plain geopolymer exhibits a continuously increasing flexural strength from 10 MPa at 20 °C to 25.9 MPa after 1000 °C exposure, attributed to thermally induced further geopolymerization and ceramic-like crystalline phase formation. Incorporating 5% wollastonite fibers results in slightly increased initial and residual flexural strength but comparable peak deflection, toughness and brittle failure. The binary 5% wollastonite and 1% basalt fibers in geopolymer obviously improve residual flexural strength exposed to 400–800 °C. The steel fibers show remarkable reinforcement on flexural behavior at 20–800 °C exposure; however, excessive steel fiber content such as 2% weakens flexural properties after 1000 °C exposure due to severe oxidation deterioration and thermal incompatibility. The wollastonite/basalt/steel fibers exhibit a positive synergistic effect on flexural strength and toughness of geopolymers at 20–600 °C. Full article

As a promising n-type semiconductor thermoelectric material, ZnO has great potential in the high-temperature working temperature range due to its advantages of abundant sources, low cost, high thermal stability, and good chemical stability, as well as being pollution-free. Sr-doped ZnO-based thermoelectric materials were prepared using the methods of room-temperature powder synthesis and high-temperature block synthesis. The phase composition, crystal structure, and thermoelectric performances of ZnO samples with different Sr doping levels were analyzed using XRD, material simulation software and thermoelectric testing devices, and the optimal doping concentrations were obtained. The results show that Sr doping could cause the Zn-O bond to become shorter; in addition, the hybridization between Zn and O atoms would become stronger, and the Sr atom would modify the density of states near the Fermi level, which could significantly increase the carrier concentration, electrical conductivity, and corresponding power factor. Sr doping could cause lattice distortion, enhance the phonon scattering effect, and decrease the lattice thermal conductivity and thermal conductivity. Sr doping can achieve the effect of improving electrical transport performance and decreasing thermal transport performance. The ZT value increased to ~0.418 at 873 K, which is ~4.2 times the highest ZT of the undoped ZnO sample. The Vickers hardness was increased to ~351.1 HV, which is 45% higher than the pristine ZnO. Full article

Background/Objectives: Full-arch implant-supported prostheses have become a widely accepted solution for edentulous patients, yet long-term biological and mechanical complications remain a clinical concern. Methods: This retrospective study included 70 fully edentulous patients (362 implants) rehabilitated with either fixed or removable implant-supported prostheses. Data were collected on demographics, medical status, type and location of prostheses, implant type, abutments, method of fixation, and complications. Statistical analysis included Fisher’s exact test, the Mann–Whitney U test, and chi-squared tests, with a significance level set at p < 0.05. Results: Mechanical complications occurred in 41.4% of patients (29 out of 70), with framework fractures reported in eight cases (27.6%), ceramic chipping in six cases (20.7%), and resin discoloration in four cases (13.8%). The prostheses were fabricated using monolithic zirconia, metal–ceramic crowns, zirconia on titanium bars, and hybrid resin/PMMA on cobalt–chromium frameworks. Gingival inflammation was also noted in 41.4% of cases (n = 29), predominantly in posterior implant regions. Younger patients and those without systemic diseases showed a significantly higher incidence of mechanical complications. Conclusions: Two years post-treatment, mechanical and biological complications appear to be independent phenomena, not significantly associated with most prosthetic variables. Patient-specific factors, particularly age and general health status, may have greater predictive value than prosthetic design. Limitations of the study include its retrospective design and the lack of radiographic data to assess peri-implant bone changes. Full article

The objective of this study was to evaluate the effect of morpholine on saliva-contaminated resin-based composite (RBC)-CAD/CAM material repaired with resin composite. Fifty RBC-CAD/CAM materials were fabricated and assigned to five groups and surface-treated with saliva, phosphoric acid (PHR), morpholine (MRL), and a universal adhesive agent (Scotchbond universal plus, SCP) based on the following techniques: group 1, saliva; group 2, SCP; group 3, saliva + SCP; group 4, saliva + PHR + SCP; and group 5, saliva + MRL + SCP. An ultradent model was placed on the specimen center, and then the resin composite was pressed and light-cured for 20 s. A mechanical testing device was used to evaluate the samples’ shear bond strength (SBS) scores. The debonded specimen areas were inspected under a stereomicroscope to identify the failure mechanisms. The data were analyzed using one-way ANOVA, and the significance level (p < 0.05) was set with Tukey’s test. The highest SBS values were in groups 2, 4 and 5, with values of 21.43 ± 1.93, 20.93 ± 1.46, and 22.02 ± 1.77 MPa, respectively. However, they were not statistically different (p > 0.05). Group 1 had the lowest SBS value by a significant amount (1.88 ± 1.01 MPa). All specimens in group 1 showed adhesive failures. Moreover, groups 2–5 found cohesive and mixed failures. In conclusion, morpholine and phosphoric acid effectively enhance bond strength. These results indicate that alternative surface modifications with morpholine for saliva-contaminated RBC-CAD/CAM materials can significantly improve the outcome. Full article

The growing demand for organic dyes across industries increases their environmental impact since wastewater containing organic dyes poses serious risks to aquatic life, human beings, and the environment. The removal of organic dye residues is a challenge for traditional wastewater treatment facilities, highlighting the need for advanced treatment techniques that balance cost-effectiveness and sustainability in the face of today’s strict environmental regulations. The use of low-cost starting materials in ceramic membrane technology has recently become more popular as a feasible option because of its affordability and effectiveness, leveraging the synergy of adsorption and filtration to improve dye removal. Recent developments in ceramic membranes derived from waste and natural materials are examined in this review paper, along with their types, mechanisms, and applications in eliminating organic dyes from wastewater. The various forms of ceramic membranes derived from waste and natural materials are classified as follows: those composed solely of inexpensive starting materials, composites of inexpensive materials, hybrids of inexpensive and commercial materials, and inexpensive materials functionalized with cutting-edge materials such as carbon nanotubes and nanoparticles. These membranes have shown promising results in lab-scale research, but their large-scale use is still limited. The factors that negate the commercialization of these membranes are also critically discussed. Finally, key challenges and future research opportunities in the development of sustainable ceramic membranes for highly efficient dye removal are highlighted. Full article

The existing scientific literature lacks comprehensive information regarding the influence of zirconia crown height on debonding and fracture of the ceramic restorations on titanium base abutments. Additionally, there is a lack of comparative studies evaluating different types of zirconia as restorative options for screw-retained restorations. Purpose: The purpose of this study was to assess the fracture strength and the failure modes of the zirconia crown/titanium abutment complex by investigating the impact of increasing the height of zirconia crown and comparing different types of zirconia (3 mol% yttria-stabilized zirconia and translucent 5 mol% yttria-stabilized zirconia). Materials and Methods: Six groups of 10 specimens in each group were fabricated. Three groups of specimens (groups # 1, 2, and 3) were fabricated from 3Y zirconia in corresponding heights of 8, 10, and 12 mm. Three more groups (groups # 4, 5, and 6) were fabricated from 5Y zirconia in the same heights (8, 10 and 12 mm). All copings were bonded to 4 mm high titanium base abutments using dual-polymerization resin cement. The specimens underwent load cycling of 100,000 cycles with a force of 100 N. Subsequently, the specimens were loaded to compression until fracture and the failure mode was visually evaluated. Results: Statistically significant differences in fracture strength were noted among all tested groups. Conclusions: 3Y zirconia showed increased strength compared to 5Y in all heights. Ceramic copings with lower height showed increased strength compared to higher copings in both tested zirconia materials. Full article

In recent days, aluminum-based hybrid composites have garnered more interest than monolithic alloys owing to their remarkable properties, encompassing a high strength-to-weight ratio, excellent corrosion resistance, and impressive wear durability. The present study attempts to optimize the multiple wear attribute characteristics of Al6061/SiC/Al₂O₃ hybrid composites using grey and entropy-based VIKOR techniques. The composites were produced by adding equal proportions of SiC/Al₂O₃ (0–12 wt.%) ceramics through the stir-casting process, using an ultrasonication setup. Dry sliding wear experiments were executed with tribometer variants, namely reinforcement content (wt.%), load (N), sliding velocity (v), and sliding distance (SD), following L₂₇ OA. The optimal combination of process variables for achieving high GRG values from grey analysis was found to be A₃-B₃-C₃-D₃. The S/N ratios and ANOVA results for GRG indicated that RF content (wt.%) is the predominant component determining multiple outcomes, followed by sliding distance, load, and sliding velocity. The multi-order regression model formulated for the VIKOR index (Q_i) displayed high significance and more accuracy, with a variance of 0.0216 and a coefficient of determination (R²), and adjusted R² values of 99.60% and 99.14%. Subsequent morphological studies indicated that plowing, abrasion, and adhesion mechanisms are the dominant modes of wear. Full article

This paper investigates the impact of sintering temperature on oxygen vacancy concentration and its subsequent effect on the microstructure and electrical properties of $B{i}_{4}T{i}_3{O}_{12}$ (BIT) ceramics. To further clarify these effects, VASP software was employed to simulate BIT ceramics with varying oxygen vacancy concentrations.The experimental results demonstrate that sintering temperature significantly influences the oxygen vacancy concentration. At the optimal sintering temperature of 1080 °C, the BIT ceramics exhibit a balanced microstructure with a grain size of 4.16 μm, the lowest measured oxygen vacancy concentration of 18.44%, and a piezoelectric coefficient ($d_{33}$) of 9.8 pC/N. Additionally, the dielectric loss ($tan\delta$) remains below 0.2 at 500 °C, indicating excellent thermal stability. VASP-based simulations reveal that increasing the oxygen vacancy concentration from 18.56% to 44.55% results in a significant collapse of the band gap (from 2.8 eV → 1.0 eV) and a transition in conductivity type from p-type to n-type. This shift induces a leakage current-dominated threshold effect, leading to a decrease in piezoelectric properties ($d_{33}$ reduced from 9.8 to 6.9 pC/N). Atomic-scale density of states (DOS) analyses indicate that the delocalization of $T{i}^{3+}$ and the weakening of Bi–O hybridization collectively induce lattice distortion and ferroelectric inconsistency. These changes are correlated with an increase in dielectric loss and a slight reduction in Curie temperature (from 620 °C → 618 °C). In conclusion, this study comprehensively elucidates the influence of oxygen vacancy concentration on the microstructure and electrical properties of BIT ceramics. The findings provide a theoretical foundation and practical insights for designing high-performance piezoelectric ceramics. Full article

This study investigates membrane fouling control in a submerged anaerobic ceramic membrane bioreactor (AnCMBR) treating high-strength food wastewater (chemical oxygen demand (COD): 10–30 g/L). A hybrid strategy combining mechanical cleaning via a moving rubber blade (MRB) (termed anaerobic ceramic blade MBR (AnCBMBR)) with intermittent salt-assisted backwash (SAB) was tested to manage transmembrane pressure (TMP) and sustain treatment performance. During more than 300 days of field operation, MRB alone maintained stable TMP below 0.15 kg_f/cm² without backwashing, achieving more than 90% COD removal at a very short hydraulic retention time (HRT) of 1–2 days. Introducing intermittent SAB further stabilized operations and enhanced total phosphorus (T-P) removal by facilitating struvite formation through the interaction of MgCl₂ and phosphorus in the reactor. The AnCBMBR system demonstrated reliable, long-term fouling control and treatment efficiency, even under high organic loads, proving its viability for small-scale facilities managing concentrated food wastewater. This study advances practical strategies for sustainable anaerobic MBR operation under challenging industrial conditions. Full article

Background: Prophylactic polishing pastes (PPPs) are widely used to clean teeth and dental restorations; however, their effects on restorative materials are crucial for clinical outcomes. This study investigates the impact of PPPs on the susceptibility of CAD/CAM restorative materials to staining and the relationship between surface roughness and discoloration. Methods: Samples of tested materials (resin nanoceramic, hybrid ceramic, feldspathic ceramic, and lithium disilicate-reinforced glass ceramic) were treated with various PPPs (Cleanic, CleanJoy, Detartrine, Proxyt). Surface roughness and color parameters were recorded before and after the PPP application and following coffee immersion for 12 days. Initial measurements of surface roughness (Ra1) and color were taken. The specimens were divided into groups based on the PPP applied. After PPP application, secondary roughness (Ra2) and color values were measured. Changes in roughness (ΔRa), color (ΔE*ab, ΔE00), and whiteness index (ΔWID) were calculated post-application and after coffee immersion. Data normality was tested with the Shapiro–Wilks test. Two-way ANOVA evaluated the effects of material type and PPP on ΔE, ΔWID, and ΔRa. One-way ANOVA, Tukey HDS test, and Pearson correlation were used for further analysis, with significance set at p < 0.05. Results: The Vita Enamic–Detartrine group showed the highest ΔEab 1 and ΔE001 values, while Cerasmart–control showed the lowest. The Vita Enamic–Proxyt group had the lowest ΔWID1, and Vita Enamic–Cleanjoy exhibited the highest values of ΔEab 2, ΔE002, and ΔWID2. The E.MAX–control group had the lowest values for these metrics. No significant correlation was found between ΔRa and color changes (ΔE*ab 2, ΔE002, ΔWID2); however, a moderate positive correlation was found between values of ΔE1 and ΔE2. Conclusions: These findings indicate that PPPs significantly affect the discoloration and surface features of CAD/CAM materials, with both types of PPPs and materials. Full article

The aim of this innovative study was to investigate the feasibility of a modified butt joint preparation with two grooves instead of a ferrule when root dentin tissue is limited in mandibular molars. It was also investigated to what extent the effect of these treatment options on marginal and internal fit and fracture strength (FS) varied according to the type of material and whether or not a fiber ribbon was used at the base. Marginal and internal fit were evaluated using the triple-scan protocol. Statistical analysis was conducted via a three-way analysis of variance (ANOVA). The absolute marginal discrepancy (AMD), marginal discrepancy, and overall fit values for the ceramic group were 127 μm, 108 μm, and 120 μm, respectively, while corresponding values for the hybrid ceramic group were 139 μm, 116 μm, and 130 μm (p < 0.05). The mean FS recorded for ceramic restorations was 662 N, whereas hybrid ceramic restorations demonstrated a significantly higher FS of 903 N (p < 0.001). When material type was assessed independently of preparation design and base configuration, both ceramic and hybrid ceramic exceeded the predefined clinical acceptability threshold for AMD; however, they remained within acceptable limits for the remaining parameters. Among the evaluated configurations, hybrid ceramic restorations incorporating ferrules and fiber-reinforced bases exhibited the highest FS values, whereas ceramic restorations with modified biological widths and lacking fiber reinforcement yielded the lowest FS values. Full article

Thermal runaway in microwave hybrid heating of ceramics is an unwanted phenomenon which damages the sintered products. The aim of the present study is to establish to what extent the pressing forces of 100, 200 and 300 MPa used in the compaction process and the optimization of the microwave heating mechanism can reduce the occurrence of thermal runaway. Modeling and simulation of temperature distributions alongside defects created by the compaction process are performed in order to evaluate their influence on the stability of MHH. Based on CT scanning, defects with dimensions from 110 to 515 μm are studied in terms of local overheating and how the thermal runaway can lead to internal arc discharge. The results show that samples compacted at 100 MPa and exposed at 600 W injected power reach temperatures peaks around 1010 °C and are affected by major cracks and large melted areas. The samples compacted at 200 and 300 MPa present similar behavior, without arc discharge, but are also affected by cracks. Based on these findings, the MHH process can be applied to sintering processes but with a reduced injected power below 300 W for samples compacted with pressing forces higher than 300 MPa. Full article

Minimizing the risk of secondary caries in dentistry is achieved by using adhesive systems that provide a strong bond between the natural hard tissue and the restorative material. Evaluating the effectiveness of these systems requires studying both their interaction with dentin and enamel and their behavior in environments with varying acidity. In this work, the interaction of a reactive monomer, 4-methacryloxyethyl trimellitic anhydride (4-META), used in adhesive systems with both dentin-like hydroxyapatite (HA) and hydroxyapatite ceramics, was investigated. Kinetic studies showed that under experimental conditions, 4-META was hydrolyzed and amorphized. Dentin-like HA possessed greater adsorption capacity to 4-META than ceramic HA. Immersion of HA into a solution of 4-META led to formation of an acidic calcium phosphate phase over time in both systems. Studies on the solubility of the synthetic nanosized hydroxyapatite and its derivative with 4-META in 0.1 mol/L lactic acid, also containing CaCl₂, Na₂HPO₄, and NaF (pH 4.5), and in distilled water (pH 6.3) indicated the occurrence of dissolution, complexation, and crystallization processes, causing changes in the liquid and solid phases. The total Ca²⁺ concentration upon dissolution of hybrid HA-4-META in a lactic acid solution was three times lower than the total Ca²⁺ concentration upon dissolution of pure HA. This suggested that 4-META-treated dentin-like surfaces demonstrate greater resistance to dissolution in acidic environments compared to untreated surfaces, highlighting the potential for these hybrids in dental applications. Full article