Search Results (164)

Ceramic materials have gained outstanding popularity in restorative and prosthetic dentistry due to their combination of high biocompatibility, mechanical durability, and natural esthetics. Among the most important developments in this field are the use of zirconia- and glass-based ceramics for various applications. Zirconia ceramics, especially yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), are famous for their high mechanical strength, transformation toughening, chemical stability, and great biocompatibility. Newer generations like 4Y/5Y-PSZ zirconia have addressed the demand for higher translucency, meeting esthetic requirements. Glass–ceramics, including lithium disilicate and leucite-reinforced systems, are preferred for their optical properties, etchability, and strong adhesive bonding. Their microstructure provides a balance between strength and esthetics, supporting minimally invasive restorations with long-term clinical success. Both zirconia and glass–ceramics exhibit favorable biological responses, including low plaque accumulation and soft tissue compatibility. The goal of ongoing research is to overcome limitations, such as low-temperature degradation, bonding limitations, and surface durability. Also, to improve mechanical performance and functional integration, new approaches include 3D printing, graded materials, nanostructuring, and bioactive coatings. This review aims to provide a comprehensive overview of the composition, properties, clinical applications, current limitations, and future perspectives of zirconia- and glass-based ceramics in restorative dentistry. Full article

Aim: This in vitro study aimed to evaluate the marginal and internal fit of three monolithic CAD/CAM zirconia ceramics with different Y-TZP contents, prepared with chamfer and rounded shoulder finish lines. Methods. Sixty monolithic zirconia crowns were fabricated and divided into three groups (n = 20) based on their yttria content: (1) multilayer zirconia consisting of a dentin layer of 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and an incisal layer of 5 mol% partially stabilized zirconia (5Y-PSZ), (2) shade-gradient zirconia fully composed of 3Y-TZP, and (3) shade-gradient zirconia containing 4 mol% partially stabilized zirconia (4Y-PSZ). Each group was further divided into two finish line configurations (chamfer and rounded shoulder). Marginal and internal gaps were measured using the silicone replica technique under a stereomicroscope by a single operator. Data were analyzed using three-way ANOVA followed by Tukey’s post hoc test (α = 0.05). Marginal and internal gaps were assessed using the silicone replica technique under a stereomicroscope by a single operator. Statistical analysis was performed with three-way ANOVA and Tukey’s post hoc test (p < 0.05). Results: The occlusal region exhibited the largest gap values, while the axial region showed the smallest across all groups. Mean marginal and internal gaps were 33.79 µm for chamfer and 43.37 µm for rounded shoulder finish lines. Zirconia with higher Y-TZP content demonstrated significantly greater gap values than those with lower percentages (p < 0.05). Significant interactions were found among finish line design, material type, and measurement region (p < 0.05), with rounded shoulder margins showing larger gaps (p = 0.001). Conclusions: Y-TZP content significantly affects marginal and internal adaptation, with higher percentages associated with increased gap values. Both finish line types produced clinically acceptable fits, although chamfer margins provided superior adaptation. Full article

The mechanical and microstructural properties of monolithic zirconia ceramics are significant factors for their long-term clinical performance. This study aims to investigate the effects of hydrothermal aging on these properties for the 3Y-TZP, 4Y-TZP, and 5Y-TZP formulations. Specimens were prepared from 3 different zirconia blocks: 3Y-TZP (HT), 4Y-TZP (ST), and 5Y-TZP (XT). Half of the specimens were aged in an autoclave (134 °C, 2 bar, 5 h) while the others remained as controls. Three-point flexural strength, Vickers hardness, and surface roughness tests, as well as XRD, AFM, and SEM/EDS analysis, were performed. The material type significantly affected the flexural strength, Vickers hardness, and surface roughness. Aging did not significantly affect the flexural strength or surface roughness but reduced the Vickers hardness in the 3Y-TZP sample. The 3Y-TZP and 5Y-TZP samples displayed the highest and lowest flexural strength, respectively. In the non-aged groups, 3Y-TZP and 5Y-TZP exhibited higher hardness than 4Y-TZP, and after aging, 3Y-TZP displayed the lowest hardness. Further, 5Y-TZP showed the highest surface roughness before and after aging. XRD revealed an increased monoclinic phase in the aged 3Y-TZP and 4Y-TZP. No monoclinic phase was observed in 5Y-TZP. According to AFM measurements, aging led to a smoother surface in 3Y-TZP but increased roughness in 4Y-TZP and 5Y-TZP. SEM/EDS revealed changes in the elemental compositions following aging. According to the results of this study, different material formulations affect the mechanical behavior and microstructural properties of monolithic zirconia ceramics. Further, hydrothermal aging displayed effects on the Vickers hardness and phase transformations. Full article

Surface treatments play a crucial role in modifying the surface properties and biological performance of dental ceramics. This study investigated the effects of surface conditions on the wettability, cytocompatibility, and bacterial resistance of 4 mol% Y₂O₃-stabilized tetragonal zirconia polycrystal (4Y–TZP) and two lithium disilicate (Li₂Si₂O₅) glass ceramics (Amber^® Mill (AM) and Amber^® Mill Abut-Crown (AC)). Human gingival fibroblast (HGF-1) responses and biofilm formation on the machined, polished, and glazed samples were evaluated. The polished 4Y–TZP sample exhibited the highest water contact angle (WCA; 71.3°), while that of the AC samples decreased as the sample was machined (58.4°), polished (46.8°), and glazed (14.0°). The wettability, cytocompatibility, and bacterial resistance of the dental ceramics were significantly influenced by material type and surface condition. Among the surface-treated samples, the glazed specimens exhibited the lowest WCA and bulk density; thus, wettability is an important factor for cell proliferation and bacterial resistance. Among all samples, HGF-1 cells adhered well to the glazed ceramics and significantly proliferated over time. Particularly, the 4Y–TZP and AC glazed samples exhibited the lowest biomass and strong resistance to biofilm formation and bacterial adhesion. Thus, the glaze dramatically affected HGF-1 cell growth and antibiofilm formation. Full article

In this study, the chemical solubility (stability) of yttria-partially stabilized zirconia (2.3Y-TZP) dental ceramics, both glazed (Group 2) and non-glazed samples (Group 1), was evaluated using a modified testing protocol based on ISO 6872:2024. Chemical stability was assessed by measuring ion release with inductively coupled plasma mass spectrometry (ICP-MS) and by analyzing phase composition with X-ray diffraction (XRD). While ISO 6872 prescribes chemical stability testing in a 4 wt.% aqueous acetic acid solution at 80 °C for 16 h, the exposure duration in this study was extended to 768 h (32 days) to allow a more accurate determination of long-term solubility behavior. Additionally, the surface roughness parameters (R_a, R_max, R_z, S_a, S_q) were analyzed and evaluated before and after solubility testing. Kinetic analysis revealed that degradation followed a near-parabolic rate law, with power-law exponents of n = 2.261 for Group 1 and n = 1.935 for Group 2. The corresponding dissolution rate constants were 3.85 × 10⁻⁵ µgⁿ·cm⁻²ⁿ·h⁻¹ for Group 1 and 132.3 µgⁿ·cm⁻²ⁿ·h⁻¹ for Group 2. XRD results indicated that the long exposure to acetic acid induced a partial phase transformation of zirconia from the tetragonal to the monoclinic phase. Under prolonged acetic exposure, the glaze layer on 2.3Y-TZP exhibited significantly higher dissolution, whereas the zirconia (polished, unglazed) showed low ion release. The temporal change in the total amount of dissolved ions was statistically analyzed for Group 1 and Group 2. The samples showed a strong correlation, but ANOVA confirmed significant differences between them. Full article

Objective: Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), a variant of zirconia (ZrO₂), has attracted interest as a substitute for titanium in dental and orthopedic implants, valued for its biocompatibility and aesthetics that resemble natural teeth. However, its bioinert surface limits osseointegration, making surface modifications such as calcium phosphate (CaP) coatings highly relevant. Materials and methods: The review process adhered to the PRISMA guidelines. Electronic searches of PubMed, Scopus, Web of Science, Embase, and Cochrane Library (July 2025) identified studies evaluating CaP-coated zirconia implants. Eligible studies included in vitro, in vivo, and preclinical investigations with a control group. Data on coating type, deposition method, and biological outcomes were extracted and analyzed. Results: A total of 27 studies were analyzed, featuring different calcium phosphate (CaP) coatings including β-tricalcium phosphate (β-TCP), hydroxyapatite (HA), octacalcium phosphate (OCP), and various composites. These coatings were applied using diverse techniques such as RF magnetron sputtering, sol–gel processing, biomimetic methods, and laser-based approaches. In multiple investigations, calcium phosphate coatings enhanced osteoblast attachment, proliferation, alkaline phosphatase (ALP) expression, and bone-to-implant contact (BIC) relative to unmodified zirconia surfaces. Multifunctional coatings incorporating growth factors, antibiotics, or nanoparticles showed additional benefits. Conclusion: CaP coatings enhance the bioactivity of zirconia implants and represent a promising strategy to overcome their inertness. Further standardized approaches and long-term studies are essential to verify their translational relevance. Full article

Objective: This retrospective study aimed to evaluate the two-year clinical performance of ultra-thin, no-prep Prettau^® Skin zirconia veneers placed in the anterior region of the maxilla and mandible. Materials and Methods: This single-cohort retrospective series did not include a conventional control group. A total of 201 veneers (Prettau^® Skin, 5Y-TZP zirconia) were placed in the anterior maxilla and mandible. Veneers were air-abraded with 50 µm Al₂O₃ (0.25 MPa, ~10 mm, 20 s) and bonded using an MDP-containing adhesive (Tokuyama Bond, Tokuyama Dental, Japan) and dual-cure resin cement (Estecem II, Tokuyama Dental, Japan) following enamel etching with 37% H₃PO₄ (Etching Gel, Cerkamed, Poland). Clinical performance was assessed using the modified FDI criteria after two years. Results: At 24 months, no debonding events were recorded. The survival rate was 99.5% (95% CI: 97.3–99.9). Fracture rate was 0.5% (95% CI: 0.1–2.8). Most veneers received “very good” scores for surface luster (81.6%, 95% CI: 75.6–86.4), color match (96.0%, 95% CI: 92.0–98.0), marginal adaptation (84.1%, 95% CI: 78.3–88.6), and anatomical form (100%, 95% CI: 98.1–100). Periodontal response was rated as “very good” or “good” in 90.0% (95% CI: 85.4–93.4) of cases. Patient satisfaction remained consistently high (100%, 95% CI: 98.1–100). Conclusions: Ultra-thin, no-prep Prettau^® Skin zirconia veneers show favorable short-term clinical outcomes, offering excellent esthetic results, mechanical stability, and biological compatibility. These findings support their use as a minimally invasive option in anterior restorative dentistry. However, further long-term studies are needed to confirm their durability and compare outcomes with conventional veneer techniques. Full article

Background: To evaluate the fracture resistance of 3D-printed 3-unit fixed dental prostheses (FDPs) made from tetragonal zirconia polycrystal (3Y-TZP). Methods: Based on a maxillary typodont model with a missing first molar and neighboring teeth with full crown preparations, FDPs differing in wall thickness (d = 0.6 mm / d = 0.8 mm / d = 1.0 mm) were designed. For all test groups, 12 samples were fabricated from 3Y-TZP by either 3D-printing or milling. For 3D-printing, pontic designs were modified by basal slots to enable regular firing times. After luting on CoCr dies, samples underwent artificial aging. Loads tilted by 30° were applied on the mesio-buccal cusp of the pontic, and fracture resistance F_u was assessed. Welch ANOVA and Dunnett-T3 tests were used for statistical evaluation. Results: Significant differences in F_u were identified (Welch ANOVA, p < 0.001). For milled FDPs, fracture originated from connector areas, and F_u increased with increasing wall thickness (d = 0.6 mm: 1536 ± 131 N, d = 0.8 mm: 2226 ± 145 N, d = 1.0 mm: 2686 ± 127 N, significant differences but for the comparison d = 0.8 mm vs. d = 1.0 mm). For 3D-printed FDPs, the loaded cusp fractured, and F_u did not change with FDP wall thicknesses (p > 0.779, F_u = 1110 ± 26 N for all PZ FDPs). Milled FDPs showed significantly higher F_u when compared to 3D-printed FDPs with identical wall thickness. Conclusions: Although 3D-printed zirconia FDPs still show lower fracture resistance values than their milled counterparts, all tested FDP configurations clearly exceed the clinical reference thresholds and can therefore be recommended for clinical use. Full article

Dental implant components are typically fabricated using subtractive manufacturing, often involving metal materials that can be costly, inefficient, and time-consuming. This study explores the use of additive manufacturing (AM) with zirconia for dental implant overdenture bars, focusing on mechanical performance, stress distribution, and fit. Solid and lattice-structured bars were designed in Fusion 360 and produced using LithaCon 210 3Y-TZP zirconia (Lithoz GmbH, Vienna, Austria) on a CeraFab 8500 printer. Post-processing included cleaning, debinding, and sintering. A 3D-printed denture was also fabricated to evaluate fit. Thermography and optical imaging were used to assess adaptation. Custom fixtures were developed for flexural testing, and fracture loads were recorded to calculate stress distribution using finite element analysis (ANSYS R2025). The FEA model assumed isotropic, homogeneous, linear-elastic material behavior. Bars were torqued to 15 Ncm on implant analogs. The average fracture loads were 1.2240 kN (solid, n = 12) and 1.1132 kN (lattice, n = 5), with corresponding stress values of 147 MPa and 143 MPa, respectively. No statistically significant difference was observed (p = 0.578; α = 0.05). The fracture occurred near high-stress regions at fixture support points. All bars demonstrated a clinically acceptable fit on the model; however, further validation and clinical evaluation are still needed. Additively manufactured zirconia bars, including lattice structures, show promise as alternatives to conventional superstructures, potentially offering reduced material use and faster production without compromising mechanical performance. Full article

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

The aim of translucency-enhancing liquids (TEL) is to locally influence the phase composition of zirconia in order to increase its translucency. This study aimed to determine the influence of TEL on 3Y- and 4Y-TZP zirconia concerning roughness, hardness, wear, flexural strength, dynamic stability and fracture force of fixed dental prostheses after thermal cycling and mechanical loading. Two zirconia materials (4Y-TZP; 3Y-TZP-LA, n = 8 per material and test) were investigated with and without prior application of TEL. Two-body wear tests were performed in a pneumatic pin-on-block design (50 N, 120,000 cycles, 1.6 Hz) with steatite balls (r = 1.5 mm) as antagonists. Mean and maximum vertical loss as well as roughness (Ra, Rz) were measured with a 3D laser-scanning microscope (KJ 3D, Keyence, J). Antagonist wear was determined as percent area of the projected antagonist area. Martens hardness (HM; ISO 14577-1) and biaxial flexural strength (BFS; ISO 6872) were investigated. The flexural fatigue limit BFSdyn was determined under cyclic loading in a staircase approach with a piston-on-three-ball-test. Thermal cycling and mechanical loading (TCML: 2 × 3000 × 5 °C/55 °C, 2 min/cycle, H₂O dist., 1.2 × 10⁶ force á 50 N) was performed on four-unit fixed dental prostheses (FDPs) (n = 8 per group) and the fracture force after TCML was determined. Statistics: ANOVA, Bonferroni test, Kaplan–Meier survival, Pearson correlation; α = 0.05. TEL application significantly influences roughness, hardness, biaxial flexural strength, dynamic performance, as well as fracture force after TCML in 3Y-TZP. For 4Y-TZP, a distinct influence of TEL was only identified for BFS. The application of TEL on 3Y- or 4Y-TZP did not affect wear. TEL application has a strong effect on the mechanical properties of 3Y-TZP and minor effects on 4Y-TZP. All effects of the TEL application are of a magnitude that is unlikely to restrict clinical application. Full article

This study examined the relationship between microhardness, morphology, and phase composition of dental yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), which directly impact their long-term clinical performance and durability. The primary objective was to investigate the effects of yttria content and polishing on the surface properties and hardness of these materials. Samples from ZirCAD Prime, Cercon ht ML, ZIRCONIA YML, and ZirCAD LT were analyzed using Vickers hardness testing, Powder X-ray Diffraction (PXRD), and Scanning Electron Microscopy (SEM). SEM analysis revealed a gradual increase in grain size and porosity with higher yttria content in unpolished samples. Polishing resulted in a relatively uniform surface morphology with observable striations across all samples, subsequently leading to similar Vickers hardness values for all polished samples. PXRD and SEM analyses identified that these similar hardness values were likely due to the predominant monoclinic phase on the surface, induced by polishing. These findings underscore the significant influence of yttria content and polishing on Y-TZP microstructure and surface hardness, highlighting their critical role in the long-term success and clinical applicability of dental restorations. Full article

To investigate the sintering shrinkage behavior of multigeneration, multilayer zirconia materials using geometrical measurements. Seven zirconia CAD/CAM materials were analyzed, comprising two mono-generation zirconia (HTML: Katana Zr, HTML Plus, 3Y-TZP; UTML: Katana Zr, UTML, 5Y-TZP) and five strength-gradient multilayer zirconia (AIDI: optimill 3D PRO Zir; PRIT: Priti multidisc ZrO₂ multicolor; UPCE: Explore Esthetic; ZCPC: IPS e.max ZirCAD Prime; ZYML: Katana YML) materials. Cubes (10 × 10 × 10 mm³) were milled in varying positions within the disks. Geometrical measurements were applied before and after dense sintering using a micrometer screw gauge, light microscopy, as well as surface scans and shrinkages were calculated. Data were analyzed using Kolmogorov–Smirnov, five-way ANOVA followed by the Scheffé post hoc test, and partial eta squared, as well as the Kruskal–Wallis test, including Bonferroni correction (p < 0.05). The highest influence on the shrinkage was exerted by the zirconia material (^η_P² = 0.893, p < 0.001), followed by the test method (^η_P² = 0.175, p < 0.001), while the vertical and horizontal position and measurement point showed no impact on the shrinkage results (p = 0.195–0.763) in the global analysis. Depending on the test method, the pooled shrinkage values of all tested zirconia materials varied between 17.7 and 20.2% for micrometer screw gauge, 17.7 and 20.1% for light microscopy, and 17.8 and 21.1% for surface scan measurements. The shrinkage values measured in the upper, middle, and lower multilayered vertical direction did not differ significantly in the global analysis for the multilayer materials. Therefore, a uniform shrinkage of these strength-gradient multilayer zirconia materials within clinically relevant restorations can be assumed. Full article

This work systematically investigates the influence of two spark plasma sintering (SPS) temperatures (1400 °C and 1600 °C) on the mechanical and tribological properties of two yttria-stabilized zirconia ceramics: 3 mol.% Y₂O₃ (3Y-TZP) and 1.5 mol.% Y₂O₃ (1.5Y-TZP). The ceramics’ microhardness, nanohardness, Young’s modulus, fracture toughness, and tribological performance were evaluated. The results show that 3Y-TZP maintains high hardness (Vickers hardness HV ~1300; nanohardness ~17.1 GPa) and stable fracture toughness (~4.2 MPa·m½), nearly independently of sintering temperature. In contrast, 1.5Y-TZP exhibits a critical trade-off: sintering at 1400 °C yields exceptional fracture toughness (~6.2 MPa·m½), but increasing the temperature to 1600 °C causes a sharp drop to ~4.5 MPa·m½. Tribologically, the highest wear resistance under a 5 N load was observed for the 3Y-TZP sample sintered at 1600 °C. These findings suggest that for low-yttria compositions, higher SPS temperatures can trigger detrimental microstructural changes that degrade toughness. The results provide crucial insights for tailoring SPS parameters and Y-TZP compositions for specific high-performance applications, balancing the competing requirements of hardness and fracture toughness. Full article

Aging of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) under wet conditions is known as low-temperature degradation (LTD), which is associated with phase change and decreasing mechanical strength. Herein, we studied the effects of different surface treatments on the LTD of three different commercial Y-TZP blocks utilizing CAD/CAM technology, namely, Cercon^®, e.max^® ZirCAD, and Vita In-ceram^® YZ. The blocks were immersed in 4% acetic acid at 80 °C for 0, 7, 14, and 28 days. The effects of surface treatments such as sandblasting and polishing were also examined. The results showed that the monoclinic phase increased with immersion time in all three brands. In Cercon^® blocks, a minimal amount of phase transformation was observed, with the smallest amount of degradation after immersion. Sandblasting and polishing both suppressed phase transformation. After immersion, the mechanical strength exhibited a small decrease with time. Accelerating the evaluation of the LTD of zirconia may effectively help with clinical applications. Full article