Purpose
The aim of this in vitro study was to assess the efficacy of fiber reinforcement to enhance flexural strength of the transitional implant‐supported fixed dental prosthesis (TISFDP).
Materials ...and methods
One hundred and forty denture acrylic resin plates (64 mm × 12 mm × 5 mm) with two 7 mm diameter holes were fabricated using heat‐polymerized type (Lucitone 199) and CAD‐CAM prepolymerized type (AvaDent) materials to simulate a chair‐side reconstruction of the TISFDP. Specimens were divided into 7 groups (n = 10) according to the airborne‐particle abrasion of titanium cylinder (Straumann) surface and locations of fiber reinforcement ribbons (Ribbond‐ULTRA). No cylinder surface abrasion and no fiber added acrylate specimens were used as the controls. The prosthetic screws were hand‐tightened on a custom fixture with analogs. Specimen hole and cylinder were joined using a 50:50 mixture of chemically polymerized resin (QYK‐SET; Holmes Dental) and repair resin (Dentsply Sirona). Ten acrylate specimens with no holes were fabricated from each tested material and assigned as positive controls. A modified four‐point bending test (ASTM standard‐D6272) was conducted using a universal testing machine and a custom fixture with a crosshead speed 1 mm/min. The maximum failure loads were recorded. Data were statistically analyzed using 2‐way ANOVA and the Tukey tests at α = 0.05.
Results
The flexural strength values ranged from 55.4 ±8.3 to 140.9 ±15.4 MPa. The flexural strength decreased significantly when fiber was attached on the titanium cylinder surface (p < 0.05). There were no statistically significant differences in flexural strength values between specimens with and without titanium cylinder surface abrasion (p > 0.05). Statistically significant improvement in flexural strength was observed in specimens with fibers attached around the specimen holes (p < 0.05) buccally and lingually. The obtained values were not statistically significantly different from the positive controls (p > 0.05). Some fixation screw fractures were observed before catastrophic failure of specimens during testing.
Conclusions
Fiber reinforcement significantly improved the flexural strength of denture acrylic resins only if placed around the specimen holes on the tension side at the site of initiation of crack propagation. Even when the specimens underwent catastrophic failure, the segments remained attached to each other with the attached fibers.
The antimicrobial activity of resin acid derivatives was studied. The highest inhibitory activity
Escherichia coli
and
Bacillus subtilis
was found to be characteristic of isomerized rosin and ...12-bromodehydroabietic acid, as well as their potassium salts. Potassium 12-sulfodehydroabietate only slightly inhibits growth of
Candida tropicalis
cells. PASS online calculation showed that all of the resin acids derivatives and their potassium salts have high mucosal (
P
a
93‒98%) and pronounced antiviral (influenza) protective activities (
P
a
70‒80%).
A glass fiber/polypropylene semi-impregnated lamina was added to an epoxy laminate, prior to the resin infusion, to overcome its limited weldability. Ultrasonic welding of the hybrid composite was ...conducted by varying welding pressure, time, and vibration amplitude, and using the thermoplastic layer as adjoining surface. Welded joints were analyzed by visual inspection, X-ray tomography, and lap shear testing. Welding time significantly influenced the lap-shear strength, the weld interface quality, and the process stability, promoting the proper intermixing of the thermoplastic layer and the formation of a weld area with strong adhesion. Amplitude and pressure, on the other hand, mostly affected the power absorption. Lower pressure, intermediate amplitude, and longer duration led to an improvement in the lap-shear strength (approximately 5 MPa in the best case). High strength was linked to high exposed-fiber surface area in the fracture surface, while its reduction was attributed to the presence of unwelded areas within the polypropylene interface. X-ray tomography highlighted the correlation between the occurrence of defects in the weld interface and the power profiles, where multiple peaks indicated the material friction and a progressive intermixing of the polymeric interlayer, while flattened profiles and lower peaks are associated to discontinuous and poorly adherent interfaces.
The aim of this study was to observe the resin/dentin interfaces of universal adhesives by using scanning electron microscopy (SEM), and to compare their morphologies with conventional etch & rinse ...(ER) and self-etch (SE) adhesive systems.
Two three-step and one two-step ER adhesives and two two-step and two single-step SE adhesives were used for comparison with seven universal adhesives in ER mode and SE mode, respectively. Bonded surfaces with bovine teeth were longitudinally sectioned and mirror-polished. Half of the samples were treated with HCl and NaOCl solutions. The interfaces were subjected to argon ion beam etching and then observed by scanning electron microscopy.
The thickness of the adhesive layer (AL) of most of the seven universal adhesives and single-step SE adhesives was similar. Universal adhesives in SE mode formed a hybrid smear layer as a high-density zone between the AL and dentin. The thickness of the hybrid layer (HL) of the universal adhesives in ER mode was ∼1–2μm, with a high-density zone (reaction layer RL) below the HL.
The morphological features of most universal adhesives in SE mode and single-step SE adhesives are similar. Although resin–dentin interfaces of universal adhesives in ER mode resemble those of ER adhesives, universal adhesives have a distinctive feature, an RL.
The RL might be a sign of chemical bonding even when using universal adhesives in ER mode.
Epoxy resin (EP) exhibits excellent electrical and mechanical properties, which make it a promising material for insulation in high-voltage power modules. However, prolonged exposure to high ...temperatures can lead to thermo-oxidative aging of EP, ultimately resulting in irreparable damage to the insulation. This study aims to analyze the impact of aging on EP dielectric properties and establish a model for assessing the aging state. Firstly, the surface morphology of EP before and after thermo-oxidative aging was observed, followed by testing the frequency domain spectroscopy (FDS) curves of the sample. Subsequently, the electric field stress distribution and overall dielectric loss characteristics of the power module were studied under different aging degrees and voltage frequencies. Through decomposing FDS curves, the study revealed how thermo-oxidative aging affects the dielectric properties, and an evaluation model of aging state was constructed. The results indicate that aging can significantly increase the total dielectric loss and space charge polarization loss of the power module. The dielectric characteristic parameters corresponding to the space charge polarization were selected to establish an aging evaluation model, and the evaluation error is less than 0.064.
•PF/DCPD microcapsules were prepared via in situ polymerization.•The mean diameter and size distribution of microcapsules could be controlled.•The microcapsules possess good chemical stability in ...cementitious materials.•XCT was used to visualize the distribution and rupture process of microcapsules.•The microcapsules have a good dispersibility and trigger sensitivity to the cracks.
This paper presents work towards development of a new type of polymeric microcapsule with phenol–formaldehyde (PF) resin as shell and dicyclopentadiene (DCPD) as healing agent for self-healing microcracks in cementitious materials. The PF/DCPD microcapsules were synthesized via in-situ polymerization and characterized by means of optical microscope (OM), scanning electron microscope (SEM) and thermal analysis (TGA). The chemical stability of synthesized microcapsules and the trigger performance were studied respectively in simulated concrete pore solution and hardened cement paste specimens. The results revealed that the synthesized microcapsules possessed excellent stability in both simulated pore solution and real cement environment. X-ray computed tomography (XCT) was applied to observe the status and fracture behavior of microcapsules inside cement paste matrix. Further segmentation and 3D rendering of the reconstructed data obtained from XCT showed that the microcapsules had a good dispersibility with desired trigger sensitivity. The OM investigation of a fractured surface of a cement paste incorporated with microcapsules confirmed that the self-healing function of the microcapsules could be triggered by cracking and the healing agent could be released simultaneously to heal the cracks.
In this study, bisphenol A epoxy resin, 1,6‐Hexanediol diacrylate (HDDA), and 2,4,6‐Trimethylbenzoyl‐diphenylphosphine oxide (TPO) were utilized as a prepolymer, diluent, and photoinitiator, ...respectively, to prepare a light curing system with different amount of phosphor, which was used in place of conventional inorganic fillers. Phosphor was utilized to improve the precision of the material molded parts during the light curing process and enhance the mechanical properties of the molded parts owing to the ultraviolet (UV) absorption properties of phosphor, which prevented UV damage to the material, thus improving the light aging resistance and stability of the molded parts. Results revealed that the addition of 3% phosphor optimized the mechanical properties of the material (a maximum tensile strength of 42.43 MPa). Additionally, the material achieved the lowest linear (4.1%) and volumetric (0.58%) shrinkage at a phosphor content of 6%. This study provides a new insight into three‐dimensional (3D) printing resin for stereolithography and provides a reference for the improvement of 3D printing products.
3D printing resin molding process.
To synthesize and characterize a novel dentin adhesive containing Beta-Tricalcium Phosphate (β-TCP) nanoparticles and test its ability to reduce dentin permeability (dP).
Experimental adhesives were ...prepared by mixing Bis-GMA, TEGDMA, HEMA (50/25/25 wt.%), photo-initiators, and inhibitors. The following groups were tested: Experimental adhesives without β-TCP (Exp.); with 10 wt.% β-TCP (Exp.10 wt.% β-TCP); with 15 wt.% β-TCP (Exp.15 wt.% β-TCP), Scotchbond Multi-Purpose (SBMP) and Clearfil SE Protect Bond (CFPB). Degree of conversion (DC%, 10 and 20 s); Flexural Strength (FS), Knoop Hardness (KHN), and Cell Viability (OD%) tests were performed. dP was evaluated by hydraulic conductance, using human dentin disks (n=12), at three-time intervals: post-EDTA (T
); post-treatment (T
); and post-erosion/abrasion cycling (T
). Data were statistically analyzed (α=0.05).
For all groups, exposure time for 20 s presented a higher DC% than for 10 s. For FS, filled adhesives did not differ from unfilled and from CFPB. Experimental adhesives did not differ among them and showed lower KHN than the commercial products. Cell viability did not differ among adhesives, except Exp. 15 wt.%, which showed lower OD% than Exp., Exp. 10% and, CFPB. For dP, only Exp.10 and 15 wt.% β-TCP did not present difference between the times T
and T
. After cycling, Exp.10 wt.% β-TCP presented lower permeability than Exp. and CFPB.
The incorporation of 10 wt.% β-TCP nanoparticles into the resin-based dental material did not affect its mechanical properties and biocompatibility, and promoted the greatest reduction in dentin permeability, sustaining this effect under erosive/abrasive challenges.
A novel resin-based dental material containing β-TCP nanoparticles was able to reduce dentin permeability, maintaining its efficacy after erosive/abrasive challenges. The synthesized material did not affect dental pulp cell viability and might be promising for other conditions that require dental remineralization, such as tooth wear and dental caries.
Diterpene resin acids in conifers Keeling, Christopher I.; Bohlmann, Jörg
Phytochemistry (Oxford),
11/2006, Letnik:
67, Številka:
22
Journal Article
Recenzirano
A short review of the recent developments in understanding the genomics, molecular biology, biochemistry, and biological importance of diterpene resin acids in conifers.
Diterpene resin acids are a ...significant component of conifer oleoresin, which is a viscous mixture of terpenoids present constitutively or inducibly upon herbivore or pathogen attack and comprises one form of chemical resistance to such attacks. This review focuses on the recent discoveries in the chemistry, biosynthesis, molecular biology, regulation, and biology of these compounds in conifers.
To evaluate the effect of argon plasma treatment (PLA) when combined with sandblasting (SAN), silanization (SIL), and hydrophobic bonding resin (HBR) on the shear bond strength (SBS) of a two-year ...water-aged resin composite bonded to a newly placed composite after 24 hours and one year of water-storage.
Thirty-six light-cured composite plates (20mm x 20mm x 4mm thick) were obtained and stored at 37°C in distilled water for 2 years. These aged plates were distributed into 6 groups (n=6) according to the surface treatment: no treatment (Negative Control); SAN+SIL+HBR (Positive Control); SAN+PLA+SIL+HBR; PLA+ SIL+HBR; PLA+SIL; PLA+HBR. Fresh resin composite cylinders were built up using silicone molds (hole: 1.5 mm high x 1.5 mm diameter) positioned over the aged plates. Half of the SBS samples were stored in distilled water for 24 hours and loaded until failure, while the other half were stored for 1 year before being tested. Data were submitted to two-way analysis of variance and post-hoc Tukey Test (preset alpha of 0.05).
Positive Control, SAN+PLA+SIL+HBR and PLA+SIL+HBR groups presented higher SBS means at the 24 hour evaluation. After 1 year of water storage, all groups demonstrated significant SBS reduction, with the SAN+PLA+SIL+HBR group presenting the highest SBS.
Resin plasma treatment in combination with other surface treatments can improve the SBS of composite repairs after one year of water storage. The SBS of the composite repair was not stable over time regardless of the surface treatment.
