Dental Materials最新文献

Objectives: Monolithic 3 mol% Yttria-stabilized tetragonal zirconia polycrystal or 3Y-TZP exhibits transformation toughening phenomena which is suitable for dental restorations with minimizing the risk of fracture and to decrease reduction of natural tooth. However, the staining/glazing or layering is required to achieve of a match with the optical properties of natural dentition. The hypothesis under examination is that the physical, chemical, and structural aspects of the 3Y-TZP grain boundaries after the staining/glazing or layering.

Methods: The three sintering temperatures of 1400 °C, 1500 °C, and 1600 °C were considered followed by vacuum annealed at 750 °C for 1 min; and air post-annealed at 750 °C for 1 min RESULTS: The initial sintering step in the fabrication of zirconia restorations plays a critical role in the outcomes of the subsequent stages of glazing and layering.

Significance: The current study revealed for first time the advantage of vacuum annealing by the presence of ferroelastic domain switching toughening mechanism.

Objective: Stress concentration and excessive wear on the opposite jaw teeth are the main problems that lead to the failure of all-ceramic crown restoration. The objectives of this study were to: (1) Synthesize the biomimetic gradient zirconia/resin composites. (2) Control the porosity and structure so that the mechanical properties of the biomimetic gradient zirconia/resin composites are close to enamel and dentin.

Methods: Biomimetic uniform zirconia scaffolds with different widths (1.6 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.2 mm) and Biomimetic gradient (1.6 mm-2.2 mm) zirconia scaffolds were designed using 3DMax and Magics, fabricated by digital light processing 3D printing, and then infiltrated into dental resin for mechanical testing, finite element simulation and cytotoxicity testing.

Results: Results show that the ceramic-polymer composites exhibit a significant enhancement in strength (1.37-fold increase) and toughness (2.08-fold increase) compared to zirconia ceramic scaffold (P < 0.05), highlighting the effectiveness of our structural design. In addition, the gradient design further improves the mechanical strength of the composites. Notably, the gradient composite crown exhibits a bending strength of 138.3 (±16.7) MPa, a toughness of 9.0 (±0.5) MJ/m³, and a compressive strength of 113.7 (±2.6) MPa, values that are comparable to those of natural enamel and dentin, and shows good biosafety.

Conclusion: Biomimetic gradient zirconia/dental resin materials were precisely fabricated through a series of studies, which is expected to further improve the clinical treatment effect. At the same time, the strategic design also provides new ideas for the performance improvement of other dental materials.

Significance: Gradient zirconia/resin composite materials with mechanical properties matching natural teeth were precisely fabricated, and are expected to significantly improve clinical treatment outcomes. Additionally, the strategic design provides new insights for enhancing the performance of other dental materials.

Objectives: This study aimed to estimate the number of distinct tooth colors using a large dataset of in-vivo CIELAB measurements. It further assessed the coverage error (CE) and coverage error percentage (CEP) of commonly used shade guides and determined the number of shades needed for an ideal guide, using the Euclidean distance (ΔEab) and thresholds for clinical perceptibility (PT) and acceptability (AT) as evaluation criteria.

Methods: A total of 8153 untreated maxillary and mandibular anterior teeth were measured in vivo using calibrated dental photography. Cardinality was applied to determine the number of unique natural tooth colors. The CE and CEP were calculated for the Vita Classical and Vita 3D-Master shade guides, while the cardinality method was also used to estimate the number of shades required to adequately cover the estimated gamut of natural tooth colors.

Results: The cardinality analysis revealed 1173 unique natural tooth colors. The CE for the Vita Classical shade guide was 4.1 ΔEab, with a CEP of 75 % beyond AT, while the 3D-Master shade guide had a CE of 3.3 ΔEab and a CEP of 70 % beyond AT. Based on cardinality computation, 92 discrete shades are required to adequately cover the estimated gamut of natural tooth colors with a CE of 1.2 ΔEab and CEP of 0.3 % beyond AT.

Conclusions: Cardinality computations estimated 1173 unique tooth colors while 92 discrete shades are estimated for full coverage. Such a number is impractical for physical shade guides, but new digital tools and 3D printing may offer future solutions. Both, the Vita Classical and 3D-Master shade guides do not fully represent the range of natural tooth colors.

Clinical significance: This study highlights the limitations of existing shade guides and underscores the potential for new developments.

Background: Orthodontic treatment with transparent aligners is popular with patients. Any alteration of the plastic material, as subjected to the oral environment, could influence the treatment's durability, the aligner's aesthetic appearance, and the patient's safety.

Purpose: This study concerns the physicochemical properties of ClearCorrect® aligners before and after intraoral use, focusing on transparency, surface topography, leachable, polymer glass transition temperature, and viscoelastic properties.

Methods: Aligners were collected after two weeks of intraoral use. Unused samples were obtained from the manufacturers. Transparency was measured by UV-visible spectroscopy. Chemical modifications were studied using infrared and Raman spectroscopies. Thermal degradation, glass transition (T_g), and storage modulus (E') were characterized by thermal analysis (DSC, TGA, DMA). Surface morphology and roughness were studied thanks to SEM and AFM. Aligners were immersed in water-based solutions to identify and quantify organic leachable by HPLC chromatography and trace elements by atomic absorption spectroscopy.

Results: ClearCorrect® aligners have a three-layer structure (outer PETG/inner PU layers). Slight chemical alterations occurred after aging. There was also no significant evolution in T_g and thermal degradation temperatures and only a minimal evolution of E'. Surface and transparency alterations occurred. A difference in organic compound and trace element release levels between new and used aligners was evidenced, suggesting an intraoral release during use.

Significance: Intra-oral aging mainly impacts the aligner transparency and surface. The leachable study suggests significant ingestion of organic and non-organic compounds by the patient: investigations are needed to assess the impact of the long-term use of trays on patient health.

Objective: To evaluate the impact of sterilization methods on the structural integrity and antimicrobial properties of graphene nanocoating on titanium (GN).

Methods: GN was transferred to titanium using wet (WT) or dry transfer (DT) techniques and sterilized using an autoclave (AC), glutaraldehyde (GA), or ethylene oxide (EtO). The GN structure was characterized using Raman spectroscopy before and after sterilization. Additional specimens were characterized by Raman after AC and water jetting. Biofilm formation was assessed before and after AC using colony-forming units (CFU), biofilm biomass, and SEM (uncoated titanium was the control). Three independent samples were used for structural characterization and biofilm quantification. Statistical analyses were conducted using one-way analysis of variance (ANOVA) and Tukey's test (α = 0.05).

Results: WT and DT demonstrated high structural stability after sterilization and water jetting, with negligible coating quality or coverage loss. GN exhibited lower biofilm formation even after AC sterilization, as shown by the reduction in CFU counts, biofilm biomass, and SEM images compared to the control.

Significance: GN demonstrated high resistance to the stresses imposed by all sterilization methods tested, maintaining its structural integrity, resistance to water-jet cleaning, and antibiofilm potential. The findings suggest that standard industrial practices can effectively sterilize highly resilient GN on titanium implants and possibly other biomaterials.

Objectives: This study aimed to clarify the effect of metal elements in the coloring liquids used in the infiltration method on the physical properties of zirconia.

Methods: Two types of zirconia discs 5Y-PSZ (SHOFU Disc ZR Lucent FA, SHOFU, Kyoto, Japan) were used: with monolayer shades from W2 to W3 (Pearl White) and 5Y-PSZ with multilayer shades from A3 to A4 (L). Five kinds of coloring liquid were used to infiltrate into semi-sintered Pearl White (T-glass [CT], A4 [CA], White-Opaque [CW], Gingiva 1 [CG], and Blue X [CB]). In addition, uncolored Pearl White set to as the control (C). These specimens were analyzed using a three-point bending test (3PBT), and the fracture surface after the test was analyzed by scanning electron microscopy, elemental analysis, and crystal structure analysis. In addition, from the polished surface part of the after the 3PBT specimens, the elemental composition was analyzed using X-ray fluorescence spectroscopy (XRF).

Results: The flexural strength of CB and CG were lower than that of C (p < 0.05). XRF results showed that the Erbium (Er) content of CG was significantly greater than that of C (p < 0.05). CB exhibited a significantly higher Yttrium (Y) content compared with C (p < 0.05), and numerous pores were observed in the micrographs of the fracture surface of CG and CB.

Significance: In zirconia, where the content of Y and Er was significantly increased by infiltration with a coloring liquid, pores were observed between the zirconia crystals, and the mechanical strength decreased.

Objective: Guided tissue/guided bone regeneration (GTR/GBR) membranes are widely used for periodontal bone regeneration, but their success depends on a bacteria-free environment. Systemic antibiotic treatment often proves inadequate, moreover, the increasing prevalence of antibiotic resistance in oral infections exacerbates this challenge. This study aimed to fabricate antibacterial membranes using a new class of antibiotics for local drug delivery, to eradicate infections and promote tissue regeneration.

Methods: Membranes loaded with nitazoxanide (NTZ) were fabricated via electrospinning using poly(ε-caprolactone) (PCL) with varying concentrations of NTZ (0 %, 2.5 %, and 5 % w/w) relative to the polymer weight. Morphochemical of NTZ-loaded membranes were assessed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Fourier Transform Infrared spectroscopy (FTIR). Mechanical properties were evaluated using universal testing machine and NTZ release profile from membranes was determined by spectrophotometer (λ_max = 444) for 14 days. Antimicrobial efficacy against periodontal pathogens, cell compatibility and mineralization were evaluated using periodontal ligament stem cells (PDLSCs).

Results: Optimized spinning parameter maintained a uniform fiber diameter and successful loading of NTZ was confirmed by SEM-EDS and FTIR. NTZ incorporation did not significantly affect mechanical properties, whereas the drug release kinetics showed an initial burst, followed by sustained release over 14 days. NTZ-loaded membranes demonstrated antibacterial activity against Aggregatibacter actinomycetemcomitans (Aa) and Fusobacterium nucleatum (Fn). Importantly, the presence of NTZ showed minimal cell toxicity; however, it reduced the mineralization potential compared with that of the pure PCL membrane, which increased over time.

Significance: Taken together, these findings established that NTZ-loaded membranes could be promising barrier membrane to counteract microbial environment and aid periodontal bone regeneration.

Objective: Investigate the effect of solvent-storage on surface hardness and bulk creep of fast photo-cured bulk-fill resin-based composite (RBC) compared to conventionally irradiated bulk-fill RBCs.

Methods: Three bulk-fill RBCs were studied: Tetric® PowerFill (fast photo-cured bulk-fill RBC) (TPF), Tetric EvoCeram® (EVO), and GrandioSO® x-tra (GSOx) (conventional). Disk-shaped specimens of clinically realistic thickness (4 mm) were prepared from each material for: Group A: surface measurements (18 mm diameter) and Group B: 4 mm diameter for bulk compressive creep measurements. Group A disks were light-cured from the upper 'occlusal' surface for either 3 s or 20 s according to the manufacturer's recommendation. Martens hardness (H_M) of both top and bottom surfaces of each specimen were measured. Group B: 4 × 4 mm cylindrical specimens were fully cured to measure bulk creep (C_B). A 20 MPa static compressive stress was applied for 2 h, followed by 2 h of unloading. Strain deformation was recorded continuously for 4 h. Both Martens and bulk creep studies were performed under the following storage conditions at 37 °C: (i) dry at 24 h post curing (baseline), and (ii) after 7 and 30 d of storage in two different media: distilled water (DW) and 75 % ethanol/water (75 % E/W).

Results: At baseline, H_M for all materials ranged from 587 to 439 N/mm² (top) and 398 to 342 N/mm² (bottom). After 30 d of solvent-storage, more pronounced H_M changes were observed, with the bottom surface being more affected. Normalised H_M for TPF decreased by 44 % after 30 d in 75 % E/W. Maximum creep strain ranged from 1.1 % to 2.1 % at baseline, and after 30 d in 75 % E/W this increased from 1.9 % to 2.9 %. Depending on the material and storage condition, the percentage creep strain recovery after 30 d ranged between 65.2 % and 80 %. Increased filler loading in the bulk-fill RBCs decreased the creep strain magnitude and increased the surface hardness.

Significance: Solvent storage decreased the Martens hardness of both upper and lower surfaces and increased the bulk creep characteristics of bulk-fill RBCs. Nevertheless, there was a similar relative stability in surface hardness and viscoelastic stability of fast-cured PowerFill compared to conventionally irradiated RBCs.

Dental caries continues to be a public health issue, especially more evident in underserved populations throughout the U.S. Unfortunately, especially with an aging population, hundreds of thousands of resin composite restorations are replaced each year due to recurring decay and fracture. According to several cohort studies, the average life span of this type of restoration is 10 years or less, depending on the caries risk level of the patient and the complexity of the restorative procedure. Any new material development must depart from the simple restoration of form paradigm, in which the filling is simply inert/biocompatible. This review will discuss novel antibiofilm structures, based on a targeted approach specifically against dysbiotic bacteria. Biofilm coalescence can be prevented by using glycosyl transferase - GTF inhibitors, in a non-bactericidal approach. On the tooth substrate side, MMP-inhibiting molecules can improve the stability of the collagen in the hybrid layer. This review will also discuss the importance of testing the materials in a physiologically relevant environment, mimicking the conditions in the mouth in terms of mechanical loading, bacterial challenge, and the presence of saliva. Ultimately, the goal of materials development is to achieve durable restorations, capable of adapting to the oral environment and resisting challenges that go beyond mechanical demands. That way, we can prevent the unnecessary loss of additional tooth structure that comes with every re-treatment. CLINICAL SIGNIFICANCE: While proper restorative technique and patient education in terms of diet and oral hygiene are crucial factors in increasing the longevity of esthetic direct restorations, materials better able to resist and interact with the conditions of the oral environment are still needed. Reproducing the success of dental amalgams with esthetic materials continues to be the Holy Grail of materials development.

The goal of this study was to develop a new poly(methyl methacrylate) (PMMA)-based conjugate with enhanced mucoadhesive features for gingiva. Five MMA-based conjugates with varying amounts of hydroxyethyl maleimide (HEM) and poly(ethylene glycol) (PEG) were synthesized and characterized using infrared spectroscopy and proton nuclear magnetic resonance. Quantification of attached HEM and PEG was performed using assay kits and established protocols. Mucoadhesiveness was tested through rheological measurements, retention time, and tensile strength studies. Results showed successful unification of MMA with HEM and PEG, with varying degrees of modification and no toxic effects. Dynamic viscosity was enhanced up to 13-fold for MMA-100Mal, decreasing incrementally for MMA-75Mal, MMA-50Mal, MMA-25Mal, and MMA-0Mal. Retention time improved up to 120-fold for MMA-100Mal, decreasing to 37.5-fold for MMA-0Mal. Mucoadhesiveness followed the order: MMA-100Mal > MMA-75Mal > MMA-50Mal > MMA-25Mal > MMA-0Mal. In conclusion, the novel modification of MMA with increased mucoadhesive features to buccal gingiva suggests its potential as a long-term total denture base material, paving the way for more patient-friendly prostheses.