Dental Materials最新文献

Objective: The porous structure and gradient design of customized dental implants are crucial for the success of bone defect repair. This study aimed to optimize the design of titanium alloy (Ti-6Al-4V) dental implants using a three-period minimal surface (TPMS) structure, and to investigate the effects of its gradient structure on mechanical properties and biocompatibility.

Methods: Finite element analysis was employed to compare the mechanical properties of four typical TPMS structures (Schwarz, Diamond, SplitP, Gyroid), resulting in the selection of the Gyroid structure as having the best overall performance. Based on this structure, three Ti-6Al-4V implants were fabricated using 3D printing technology: G40 (gradient TPMS structure with 40% porosity), G50 (gradient TPMS structure with 50% porosity), and NG50 (TPMS structure with 50% porosity). The physicochemical properties of the materials were evaluated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), compression testing, and water contact angle measurements. Antibacterial experiments were conducted to investigate the antibacterial capabilities of the different groups. A mouse femoral defect model was established, and osseointegration was dynamically assessed at 4, 8 and 12 weeks post-surgery using micro-CT and histological staining.

Results: Finite element analysis showed that the Gyroid structure performed best in terms of stress distribution and displacement transfer. Experimental results indicated that the gradient structure G50 possessed the best mechanical compatibility, with its yield strength and compressive modulus most closely resembling those of natural bone, whilst effectively preventing brittle fracture. In terms of bioactivity, the G40 and G50 groups exhibited good hydrophilicity (contact angle < 90°) and excellent antibacterial rates (>94%). Experiments showed that, as the implantation period increased, the bone volume fraction (BV/TV) and bone mineral density (BMD) in the G50 group were significantly higher than those in the G40 and NG50 groups in vivo (P < 0.05). Histological staining and histomorphometric analysis showed significantly greater new bone and collagen area fractions in the G50 group than that in the G40 group at 8 weeks.

Conclusion: Within the conditions of this study, the G50 gradient Gyroid implant showed favorable mechanical behavior and greater peri-implant bone formation than the comparison groups. These findings support further investigation of gradient TPMS designs for customized bone implants.

Objectives: This study aimed to evaluate the effects of fluoride-calcium-phosphate (FCP) complexes with varying calcium concentrations on demineralization inhibition in sound enamel and dentin, and on mineral recovery and lesion depth in demineralized tissues.

Methods: Enamel and dentin blocks (5 × 3 × 2 mm³; n = 120 each) were prepared from bovine teeth. Specimens were assigned to sound or demineralized conditions and treated with Control, FCP0, FCP1, or FCP2 for 10 min, followed by 2 weeks of pH cycling. Demineralization inhibition and mineral recovery were assessed using swept-source optical coherence tomography (SS-OCT) and micro-computed tomography (micro-CT). Chemical changes were analyzed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and crystallographic characteristics were evaluated using wide-angle X-ray scattering (WAXS).

Results: FCP2 showed the strongest inhibition of demineralization in sound enamel and dentin, with minimal structural and mineral changes. In demineralized specimens, all FCP-treated groups enhanced mineral recovery compared with the Control. Among them, FCP2 generally showed the highest mineral recovery and the greatest reduction in lesion depth, particularly in dentin. FTIR analysis indicated compositional trends in enamel and dentin, with more pronounced patterns in enamel. WAXS indicated predominantly amorphous structures, with weak CaF₂-associated reflections detected only in FCP1 and FCP2.

Significance: Calcium-rich FCP complexes enhance both inhibition of demineralization and promotion of mineral recovery, demonstrating improved control of lesion progression compared with conventional fluoride conditions. These findings suggest that FCP-Complex represents a promising strategy for improving fluoride-based caries management through enhanced mineral dynamics and depth-oriented remineralization.

Objective: Clear aligners are widely used in digital orthodontics, but their clinical force delivery is governed by the time-dependent viscoelastic behavior of thermoplastic materials. Due to the thin-walled, curved, and geometrically irregular characteristics of clinical aligners, conventional tensile or bending tests and standard indentation analyses cannot reliably recover their intrinsic viscoelastic properties. Thus, the present study aimed to introduce and validate a geometry-independent indentation framework for characterizing the intrinsic viscoelastic response of clear aligners. In the present context, intrinsic viscoelastic properties refer to the reduced relaxation function and its characteristic relaxation spectrum after normalization removes time-independent geometric factors, rather than to the absolute instantaneous modulus.

Methods: The proposed method was derived from dimensional analysis and the elastic-viscoelastic correspondence principle. Its validity was examined by finite element simulations of a clinically realistic aligner geometry. Indentation experiments were further conducted on raw thermoplastic films, thermoformed films, as-fabricated aligners, and intraorally used aligners to track the viscoelastic evolution of materials during manufacturing and clinical service.

Results: Numerical simulations showed that the normalized creep and relaxation functions obtained from different aligner regions and indenter profiles agreed closely with the prescribed reference functions. Experimental measurements revealed pronounced differences between flat films and shaped aligners, together with position-dependent differences between two regions of the same appliance. These results show that the suggested method can suppress time-independent geometric contributions while retaining spatial variations in the local viscoelastic response.

Significance: The suggested indentation method enables minimally destructive, direct characterization of the reduced viscoelastic behavior of intact clear aligners without geometry-specific inverse analysis. By separating time-independent geometric effects from the normalized time-dependent response, the method can also reveal position-dependent viscoelastic characteristics associated with local forming history and clinical wear.

Objectives: To evaluate the effect of a borosilicate glass coating on the mechanical, surface and chemical properties of multilayer and 4Y-PSZ zirconia, after mechanical fatigue.

Methods: Disc-shaped (13 mm×1.2 mm) sintered specimens were obtained from two types of commercial dental zirconia: structural multilayer (4 / 5Y-PSZ) (ML) and 4Y-PSZ (4Y) (Sagemax Corp.). Specimens (n = 15) were assigned to four surface treatments: control (Ctrl - silane only), airborne-particle abrasion + silane (AL), tribochemical silica coating + silane (SI), and application of borosilicate-based glass + hydrofluoric acid + silane (BG). Surface roughness (Sa) was carried out. After dual-cure resin cement application, specimens underwent mechanical fatigue (1.2 ×10⁶ cycles, 295 N, 4 Hz). Microstructure and phase composition were analyzed using Scanning Electron Microscopy (SEM), Energy dispersive x-ray (EDS) and X-Ray Diffraction (XRD). The biaxial flexural strength (BFS) was evaluated. Data were analyzed using two-way ANOVA and Tukey's test (α=0.05).

Results: BFS was significantly affected by the surface treatments (p < 0.0001). BG showed the highest BFS (763.2 ^A MPa), followed by SI (688.4^B), AL (595.3 ^C), and Ctrl (583.0 ^C). Surface roughness (Sa, µm) ranged from AL (0.33 ^A), SI (0.26^B), Ctrl (0.08 ^C), BG (0.05^D) in both zirconia. EDS revealed increased Si and Ca in BG; fracture analysis showed more homogeneous crack propagation in BG and intergranular patterns in AL. XRD indicated predominant tetragonal/cubic phases with minor monoclinic content, slightly higher in ML.

Significance: The borosilicate glass coating improved the mechanical strength of both zirconia generations without significantly affecting their physical and surface properties under the conditions of this in vitro study. These findings support its potential as a surface treatment strategy, although further validation is required.

Objectives: To investigate how different combinations of base monomers, including diurethane dimethacrylate (DUDMA) and bisphenol A-glycidyl methacrylate (Bis-GMA), and diluent monomers, including trimethylolpropane trimethacrylate (TMPTMA) and triethylene glycol dimethacrylate (TEGDMA), as well as their mixing ratios, influence light attenuation behavior, degree of conversion (DC), mechanical properties, and cell viability in dental resins fabricated by layer-wise additive manufacturing.

Methods: Binary systems were formulated at 5:5 and 7:3 wt ratios. Their optical behavior was characterized using Jacob's working curve, while the degree of conversion (DC) was quantified via ATR-FTIR. Mechanical properties and biocompatibility were evaluated using three-point bending tests, Vickers hardness and CCK-8 assays with human gingival fibroblasts, respectively.

Results: All formulations exhibited linear working curve behavior. TEGDMA-containing systems showed significantly higher DC and flexural strength, whereas TMPTMA-containing systems demonstrated greater flexural modulus and Vickers hardness. Mixing ratio effects were system-dependent, with no direct correlation between curing behavior, DC, or mechanical properties. All formulations showed no cytotoxicity in human gingival fibroblasts.

Significance: This study provides a comprehensive understanding of how the interplay between base monomers (DUDMA, Bis-GMA) and diluents (TMPTMA, TEGDMA) dictates the performance of 3D-printed unfilled dental resins. By integrating Jacob's working curve analysis with mechanical and biological evaluations, we identified optimal formulations that balance high degree of conversion with clinical-level biocompatibility. These findings offer a precise chemical roadmap for developing next-generation additive manufacturing resins with tailored mechanical properties for restorative dentistry.

Objectives: To evaluate physicochemical properties, bioactivity and biocompatibility of experimental resin-modified calcium silicate cements (Rm-CSCs) formulated with BPA-free monomers (FUDMA and UDMA), in comparison with a BisGMA-based counterpart and commercial Rm-CSCs (TheraCal LC and BioCal-CAP).

Methods: Experimental FUDMA-, UDMA-, and BisGMA-based Rm-CSCs were synthesized at a 3:5:2 mass ratio (resin matrix: tricalcium silicate: zirconia oxide). Calcium ion release and pH changes were tested over 28 days. Degree of conversion, water sorption, and solubility were assessed. Apatite-forming ability was examined after 28-day immersion in simulated body fluid (SBF) or culture medium. Cytotoxicity was determined using a CCK-8 assay with human dental pulp cells, and initial pulp response was assessed using a vital human tooth model. Data were analyzed using one-way ANOVA or Kruskal-Wallis test followed by Tukey's HSD test (α = 0.05).

Results: All materials exhibited alkaline pH and sustained calcium ion release. Degree of conversion of FUDMA-, UDMA- and BisGMA-based formulations were 65.86%, 67.68% and 57.48%, respectively (p > 0.05). Water sorption of FUDMA- (36.22 μg/mm³) and UDMA-based cements (40.80 μg/mm³) were significantly lower than that of BisGMA-based counterpart (91.59 μg/mm³) (p < 0.05). Following SBF immersion, apatite-like calcium phosphate was formed for FUDMA-based version, other materials formed calcium carbonate as the main crystalline phase. Rm-CSCs were all cytocompatible, except TheraCal LC reduced cell viability to 42.60% (p < 0.05). Pulps capped with all Rm-CSCs maintained a well-organized morphology with no necrosis after 2 weeks.

Significance: Within the limitation of this study, the FUDMA-based formulation exhibited favorable physicochemical properties, biocompatibility and bioactivity.

Objectives: The aim of this study was to investigate the effect of solvents and storage time on the mechanical properties of 3D-printed resin composites for definitive crowns.

Methods: Three 3D-printed definitive crown resin composites: Permanent Crown (Formlab; PCR), VarseoSmile Crown plus (BEGO; VCP) and Crowntec (Saremco print; CT) and one milled resin composites: Grandio Blocs/ Disc (VOCO; Gr) were tested. A three-point bending test was used to measure flexural strength (FS) and flexural modulus (E_f) using a universal testing machine (Zwick/Roell Z020) (n = 10). Martens hardness (HM) and indentation modulus (E_IT) were measured using a Martens hardness instrument (Zwick/Roell Z2.5) (n = 18). Properties were evaluated on polished specimens 24 h after fabrication at room temperature in dry condition and then after 1 and 7 days of storage in either distilled water (DW D1/D7) or 75% ethanol/water (75% E/W D1/D7) at 37 °C. Data were analysed using two-way ANOVA and one-way repeated measure ANOVA (α = 0.05).

Results: At dry condition, mechanical properties for PCR, VCP, CT and Gr were; for FS 135.6, 120.3, 132.3 and 231.0 MPa, respectively; for E_f 4318, 3963, 4109 and 13500 MPa, respectively; for HM 218.6, 213.6, 219.7 and 858.5 N/mm², respectively; and for E_IT 6.0, 5.7, 5.8 and 22.7 kN/mm², respectively. Findings revealed a differential response to solvent exposure among the tested materials. For 75% E/W D7, there was a significant reduction (≈ 20%) in the FS of all materials (p < 0.001). Storage time in 75% E/W significantly affected the HM of all tested materials: CT (p = 0.002), VCP (p = 0.026), PCR, and Gr (p < 0.001). At 75% E/W D7, HM for PCR, VCP, CT and Gr was 157.1, 178.4, 183.6 and 699.3 N/mm², respectively; E_f and E_IT had a lower reduction.

Conclusion: This study demonstrated that the mechanical properties of both 3D-printed and milled resin composites for definitive crowns are adversely affected by solvent exposure, particularly in 75% ethanol/water. After seven days of immersion in 75% E/W, all tested materials showed a substantial reduction in flexural strength and Martens hardness. However, the changes in flexural modulus and indentation modulus were less pronounced.

Objective: Stress shielding and bacterial infection are among the main challenges associated with metallic implants. To address these limitations, a Ti-35Nb-4Ag alloy was produced by powder metallurgy, combining a low elastic modulus (67.9 ± 1.1 GPa) with silver incorporated in solid solution to provide antibacterial activity.

Methods: Compression testing was performed to determine the elastic modulus. Roughness, wettability, and surface free energy with its dispersive and polar components were determined. The cytocompatibility study was carried out in accordance with ISO 10993-5, using commercially pure grade 4 titanium as a control. Adhesion and proliferation studies were carried out with human fibroblast cells (hFFS) for 2, 4, 7, and 14 days. Antibacterial studies were performed on three Gram-positive bacterial strains: Streptococcus gordonii, Staphylococcus aureus, and Enterococcus faecalis. The colonies formed (CFU) and the metabolic activity were assessed.

Results: The results showed that there were no statistically significant differences in roughness between the different metals tested. However, the Ti-35Nb-4Ag alloy had a lower contact angle (46°) than titanium (62°), and the surface energy was higher for the alloy (58 mJ/m²) than for titanium (41 mJ/m²). The increase in the polar component of the alloy (29 mJ/m²) compared to pure titanium (16 mJ/m²) was noteworthy. The alloy also showed enhanced fibroblast adhesion and proliferation while maintaining excellent cytocompatibility. In addition, the Ti-35Nb-4Ag alloy exhibited significantly lower CFU counts and bacterial metabolic activity than commercially pure titanium.

Significance: The Ti-35Nb-4Ag alloy combines a low elastic modulus, favourable surface properties, good cytocompatibility, and antibacterial activity, making it a promising candidate for hard tissue replacement.

Objective: The biological performance of dental liner materials is commonly attributed to mineralizing ion release and presumed bioactivity. However, these materials represent complex chemical systems that may also release organic constituents with potential biological effects. While ion release has been characterized previously, quantitative data on co-released organic constituents and their cytotoxic thresholds in human dental pulp stem cells (hDPSCs) remain limited. This study aimed to identify and quantify organic substances released from six dental liner materials and to assess the cytotoxicity of selected organic and inorganic components in hDPSCs.

Methods: Specimens (n = 4 per material and elution medium) were prepared as standardized discs and incubated for 72 h in methanol or water. Organic substances released from six dental liner materials (an experimental liner/base (EXP), TheraCal LC® (TC), Dycal® (DY), Lime-Lite Enhanced™ (LL), Fuji Lining LC Paste Pak (FL), and Medcem MTA (MC)) were identified and quantified using gas chromatography-mass spectrometry (GC/MS). Based on the analytical findings and previously published ion release data, individual organic compounds and representative inorganic salts were subsequently tested separately in hDPSCs. Cytotoxicity after 24 h exposure was assessed using WST-1 assays, and EC₅₀ values were derived from four-parameter logistic (4PL) nonlinear regression with variable slope.

Results: GC/MS detected nine organic substances released into methanol, whereas no organic substances were detected in water eluates. FL showed the highest release of 2-hydroxyethyl methacrylate (HEMA, ≈0.30 mg/mL) and camphorquinone (CQ, ≈0.05 mg/mL). TC released the highest amounts of butylated hydroxytoluene (BHT, ≈0.009 mg/mL) and 4-(dimethylamino) benzoic acid ethyl ester (DMABEE, ≈0.10 mg/mL). In hDPSCs, sodium fluoride (NaF) exhibited the highest cytotoxicity (EC₅₀ ≈0.056 mg/mL), followed by CQ (≈0.068 mg/mL) and triethylene glycol dimethacrylate (TEGDMA, ≈0.475 mg/mL).

Significance: The biological performance of dental liner materials cannot be inferred from ion release alone. The integrated evaluation of organic substance release, inorganic ion elution, and substance-specific cytotoxicity provides a more comprehensive framework for the biological evaluation of so-called "bioactive" liner materials and supports substance-specific hazard characterization under standardized experimental conditions.

Objectives: Scale-dependent wetting analyses requires sophisticated generation of drops with adequate, variable drop sizes. Advanced drop shape analysis systems enable the generation of drops from micro- to picoliter range. This study investigates the influence of different drop generation techniques and measurement settings on wetting results on differently modified titanium surfaces.

Methods: Different titanium surfaces, thoroughly characterized by SEM, roughness, and XPS analyses, were included in this study: machined (M), etched (A), grit-blasted (SL), grit-blasted and acid-etched (SLA). To quantify wetting behavior, water drops were generated by three techniques yielding micro, nano and pico drops, respectively. In total, the drop volume varied from 0.3 nL to 1000 nL and the number of droplets added to generate a final drop volume from 1 to 200 drops.

Results: With smaller drop volumes, hydrophilicity increased on the A, SL and SLA surface. Furthermore, fewer droplets used to generate the same final volume resulted in increased hydrophilicity. In general, the drop volume has less impact than the droplet number. Additionally, the applied drop dispensing technique influences the contact angle results.

Significance: The study results suggest that multiscale topographies should be evaluated using multiscale wetting approaches. Since wetting analysis results depend on both surface properties and measurement conditions, such as drop application technique and size, careful interpretation of generated data is mandatory.