The Effect of Femtosecond Laser Irradiation and Plasmon Field on the Degree of Conversion of a UDMA-TEGDMA Copolymer Nanocomposite Doped with Gold Nanorods.

In this work, the effects of femtosecond laser irradiation and doping with plasmonic gold nanorods on the degree of conversion (DC) of a urethane dimethacrylate (UDMA)-triethylene glycol dimethacrylate (TEGDMA) nanocomposite were investigated. The UDMA-TEGDMA photopolymer was prepared in a 3:1 weight ratio and doped with dodecanethiol- (DDT) capped gold nanorods of 25 × 75 or 25 × 85 nm nominal diameter and length. It was found that the presence of the gold nanorods alone (without direct plasmonic excitation) can increase the DC of the photopolymer by 6-15%. This increase was found to be similar to what could be achieved with a control heat treatment of 30 min at 180 °C. It was also shown that femtosecond laser impulses (795 nm, 5 mJ pulse energy, 50 fs pulse length, 2.83 Jcm-2 fluence), applied after the photopolymerization under a standard dental curing lamp, can cause a 2-7% increase in the DC of undoped samples, even after thermal pre-treatment. The best DC values (12-15% increase) were obtained with combined nanorod doping and subsequent laser irradiation close to the plasmon resonance peak of the nanorods (760-800 nm), which proves that the excited plasmon field can directly facilitate double bond breakage (without thermoplasmonic effects due to the short pulse length) and increase the crosslink density independently from the initial photopolymerization process.

[Binding properties of components removable from dental base plate, analysed by Fourier-Transform Surface Plasmon Resonance (FT-SPR) method]. / Fogsor alaplemezbol kioldódó allergének kötodésének vizsgálata Fourier-Transzformációs Felületi Plazmon Rezonancia (FT-SPR) módszerrel.

In parallel with the emergence of new dental materials the number of allergic diseases is continuously increasing. Extremely small quantities of the allergens are capable to inducing an allergic reaction. Therefore it is particularly important to examine these materials as antigens and investigate their binding properties to proteins (e.g. formaldehyde, methacrylic acid, benzoyl-peroxide...). The Fourier Transform Surface Plasmon Resonance Spectroscopy (FT-SPR) is a suitable examination method for this type of procedure. FT-SPR measurement is performed at a fixed angel of incident light, and reflectivity is measured over a range of wavelength in the near infrared. The advantages of this method are the outstanding sensitivity, the label-free detection capability and the possibility of the real-time testing procedure. Formaldehyde and methacrylic acid are among the most common dental allergens. In our study we examined these molecules by FT-SPR spectroscopy. The aim of this work was to investigate the suitability of this method to the detection of these materials, with special focuses on the analysis and evaluation concentration-dependent measurements. Different concentrations (0.01 %-0.2%) of formaldehyde and methacrylic acid solutions were measured. The individual spectra were measured for all of the solutions, and calibration curves were calculated for the materials for the possibility of the determination of an unknown concentration. The results confirmed that the method is theoretically capable to detect hundred-thousandths scale concentration-changes in the solution flowing above the SPR-chip. The concentration-dependent studies had proved that the method capable to measure directly these materials and can provide appropriate calibration for quantitative determination. These experiments show the broad applicability of the FT-SPR method, which can greatly facilitate the mapping and understanding of biomolecular interactions in the future.

[Comparative study of polymerization shrinkage and related properties of flowable composites and an unfilled resin]. / Folyékony kompozitok és töltetlen kompozit gyanta polimerizációs zsugorodásának összehasonlító vizsgálata.

OBJECTIVES: The polymerization shrinkage and shrinkage stress of dental composites are in the center of the interest of researchers and manufacturers. It is a great challenge to minimize this important property as low as possible. Many factors are related and are in complicated correlation with each other affecting the polymerization shrinkage. Polymerization shrinkage stress degree of conversion and elasticity has high importance from this aspect. Our aim was to study the polymerization shrinkage and related properties (modulus of elasticity, degree of conversion, shrinkage stress) of three flowable composite (Charisma Opal Flow, SDR, Filtek Ultimate) and an unfilled composite resin. MATERIALS AND METHODS: Modulus of elasticity was measured using three point flexure tests on universal testing machine. The polymerization shrinkage stress was determined using bonded-disc technique. The degree of conversion measurements were performed by FT-IR spectroscopy. And the volumetric shrinkage was investigated using Archimedes principle and was measured on analytical balance with special additional equipment. RESULTS: The unfilled resin generally showed higher shrinkage (8,26%), shrinkage stress (0,8 MPa) and degree of conversion (38%), and presented the lowest modulus of elasticity (3047,02MPa). CONCLUSIONS: Highest values of unfilled resin correspond to the literature. The lack of fillers enlarges the shrinkage, and the shrinkage stress, but gives the higher flexibility and higher degree of conversion. Further investigations needs to be done to understand and reveal the differences between the composites.

Plasmonic Effect of Gold-Patchy Silica Nanoparticles on Green Light-Photopolymerizable Dental Resin.

A low ratio of polymerization is a major problem in resin-based composites. In this paper, the plasmonic effect of gold-covered silica nanoparticles on the physicochemical and mechanical properties of bisphenol A diglycidyl dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) green light-photopolymerizable dental resin was investigated at an intensity of 1.4 mW/cm2 for 40 s. Transmission electron microscopy (TEM) showed silica of about 350 nm covered with 12-15 nm gold nanoparticles (Au NPs) at 100% nominal coverage. Five different concentrations of bare and patchy silica particles were used; in the latter composite, the calculated Au wt% were 0.0052 wt%, 0.0104 wt%, 0.0208 wt%, 0.04160 wt%, and 0.0823 wt%. The plasmon peak of patchy silica-filled nanocomposite overlapped with the absorption of Irgacure 784 photoinitiator and green LED light emission peak. The effect of plasmon-enhanced polymerization achieved with green light illumination was analyzed using diametral tensile strength (DTS), differential scanning calorimetry (DSC), surface plasmon resonance imaging (SPRi), and degree of conversion (DC) based on Raman spectroscopy. The values of the Au NP with 0.0208 wt% was found to be maximum in all the measured data. Based on our result, it can be concluded that the application of patchy silica particles in dental resin can improve the polymerization ratio and the mechanical parameters of the composite.

Comparative Analysis of Bond Strength Durability of 10-Methacryloyloxydecyl Dihydrogen Phosphate-Containing Adhesives on a Low-Viscosity Bulk-Fill Composite Surface.

PURPOSE: To compare the bond durability of adhesives with 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) to low-viscosity bulk-fill composite. MATERIALS AND METHODS: Four 10-MDP-containing adhesives (Tokuyama Bond Force II [TBF II], Tokuyama; Scotchbond Universal [SU], 3M Oral Care; Clearfil Universal Bond Quick [CL], Kuraray Noritake; and G-Premio Bond [GP], GC) and one 10-MDP-free adhesive (Heliobond [HB] Ivoclar Vivadent) as a control were applied to polished, air-abraded surfaces of randomly assigned SureFil SDR flow low-viscosity bulk-fill composite blocks. The application of the adhesives was followed by applying Tetric EvoCeram universal nanohybrid composite in layers. Each layered composite block was sliced into stick specimens with a hard-tissue microtome. Half of the groups were randomly selected and tested for microtensile bond strength (immediate group); the other groups were aged in a thermocyling machine for 5000 cycles, followed by testing microtensile bond strength (aged group). The adhesive interface was evaluated with scanning electron microscopy (SEM). Failure modes were observed using light microscopy. The results were evaluated with Levene's test, ANOVA, Welch's ANOVA, Tukey's test and the Z-test as appropriate (significance: p < 0.05). RESULTS: There was a significant difference in the bond strength between 10-MDP-containing adhesives and the 10-MDP-free adhesive in all groups. Aging significantly decreased the bond strength in all adhesive groups. There was no significant difference in the bond strength durability among the 10-MDP-containing adhesives. CONCLUSION: Application of 10-MDP-containing adhesives has an advantageous effect on the air-abraded SDR composite surface compared with 10-MDP-free adhesive. The composition of 10-MDP-containing adhesives did not influence the bond strength. Aging diminishes the bond strength durability of 10-MDP-containing adhesives.

Effects of different surface treatments and adhesive self-etch functional monomers on the repair of bulk fill composites: A randomised controlled study.

OBJECTIVE: To evaluate the effect of different adhesive protocols on the microtensile bond strength (µTBS) and integrity of the repaired bulk fill composite interface. METHODS: Two hundred and seventy composite blocks made of bulk fill composites of different viscosity were randomly assigned to 18 surface conditioning groups (n = 15/group). The universal adhesive systems used were Heliobond™, Tokuyama bond force II™ and Scotchbond Universal™. A nanohybrid resin composite was applied as the repair material. Negative and positive control groups were included. Stick shape specimens of each group were subjected to µTBS testing. Representative samples from all test groups were subjected to microscopic, profilometric and SEM examination to determine their mode of failure. The data were analysed statistically using two-way ANOVA test, Tukey's test and the independent t-test (α = 0.05). RESULTS: The mean µTBS of all test groups ranged between 28.5 and 46.8 MPa and varied with the type of adhesive system employed. Significantly highest µTBS values were obtained when Tokuyama bond force II™ and Scotchbond Universal™ adhesives were used (p < 0.01) which were comparable to the coherent strength of the bulk fill resin composite in the positive control groups (p > 0.05). The viscosity of the bulk fill composite did not significantly influence repair bond strength. The microscopy and SEM examination of the failed interfaces revealed a mixture of adhesive and cohesive failures. CONCLUSIONS: Under the tested conditions, significantly greater µTBS of repaired bulk fill composite was achieved when the substrate surface was treated with adhesive systems containing a functional monomer. CLINICAL SIGNIFICANCE: Eff ;ecting a repair of a bulk fill resin composite restoration with the application of a functional monomer containing adhesive system, such as Tokuyama Bond Force II™ or Scotchbond Universal™, would seem to enhance the interfacial bond strength and integrity of the repaired resin composite interface.

Manufacturing and Examination of Vaginal Drug Delivery System by FDM 3D Printing.

Vaginal drug delivery systems can provide a long-term and constant liberation of the active pharmaceutical ingredient even for months. For our experiment, FDM 3D printing was used to manufacture the vaginal ring samples from thermoplastic polyurethane filament, which enables fast manufacturing of complex, personalized medications. 3D printing can be an excellent alternative instead of industrial manufacturing, which is complicated and time-consuming. In our work, the 3D printed vaginal rings were filled manually with jellified metronidazole or chloramphenicol for the treatment of bacterial vaginosis. The need for manual filling was certified by the thermogravimetric and heatflow assay results. The manufactured samples were analyzed by an Erweka USP type II Dissolution Apparatus, and the dissolution profile can be distinguished based on the applied jellifying agents and the API's. All samples were considered non-similar based on the pairwise comparison. The biocompatibility properties were determined by prolonged MTT assay on HeLa cells, and the polymer could be considered non-toxic. Based on the microbiological assay on E. coli metronidazole and chitosan containing samples had bactericidal effects while just metronidazole or just chitosan containing samples bacteriostatic effect. None of these samples showed a fungistatic or fungicide effect against C. albicans. Based on our results, we successfully manufactured 3D printed vaginal rings filled with jellified metronidazole.

Optimization of Plasmonic Gold Nanoparticle Concentration in Green LED Light Active Dental Photopolymer.

Gold nanoparticles (AuNPs) display surface plasmon resonance (SPR) as a result of their irradiation at a targeted light frequency. SPR also results in heat production that increases the temperature of the surrounding environment, affecting polymerization. The aim was to investigate the SPR effect of AuNPs on a dimethacrylate-based photopolymer system. The tested composites were designed to overlap the illumination required for the polymerization and the plasmon effect. The 5 nm-sized dodecanethiol capped AuNPs were applied in different concentrations in the matrix that were irradiated with green light (λ = 532 nm), where the Irgacure 784 photoinitiator also absorbs the light. The plasmonic effect was investigated for the refractive index change by surface plasmon resonance imaging (SPRi) supplemented by ellipsometry. Moreover, optical transmission and transmission electron micrographs (TEM), diametral tensile stress (DTS), and confocal Raman spectroscopy was performed to determine the degree of conversion (DC) at 1.0, 1.4, and 2.0 mW/cm2 light intensities. It was found that the optimal conditions were at 0.0208 wt% AuNPs concentration and 1.4 mW/cm2 light intensity at which the refractive index change, DTS, and DC data were all maximal. The study confirmed that AuNPs are applicable to improve the polymerization efficiency of dental composite resin.

A randomised controlled study on the effects of different surface treatments and adhesive self-etch functional monomers on the immediate repair bond strength and integrity of the repaired resin composite interface.

OBJECTIVES: To evaluate the effects of different surface conditioning methods on the immediate repair bond strength and integrity of the repaired composite interface. METHODS: One hundred and five resin composite blocks made of a nanohybrid resin composite were randomly assigned to one of the following surface conditioning groups (n = 15/group): Group 1: Gluma Self Etch™ adhesive system, Group 2: Tokuyama Bond Force II™ adhesive system, Group 3: non-roughened and non-conditioned surfaces, Group 4: sandblasting and Gluma Self Etch™, Group 5: sandblasting and Tokuyama Bond Force II™, Group 6: sandblasting only. A positive control group was also used. Resin composite identical to the substrate was applied and the repaired specimens were subjected to shear bond strength (SBS) testing. Representative samples from all groups were subjected to scanning electron microscopy and surface profilometry to determine their mode of failure. The data were analysed statistically using Analysis of Variance (ANOVA) and two independent sample t-test (α = 0.05). RESULTS: The mean SBS of all test groups ranged between 1.92 and 5.40 MPa and varied with the degree of composite surface roughness and the type of adhesive system employed. Significantly highest SBS values (5.40 ± 0.36 MPa) were obtained in Group 5 (p = 0.017) which were comparable to the coherent strength of the resin composite in the positive control group (p > 0.05). CONCLUSIONS: Under the tested conditions, significantly greater SBS of repaired resin composite was achieved when the substrate surface was conditioned by sandblasting followed by the application of the Tokuyama Bond Force II™ adhesive system. CLINICAL SIGNIFICANCE: Effecting a repair of a nanohybrid composite restoration with sandblasting and the application of TBF II would seem to enhance the interfacial bond strength and integrity of the repaired resin composite interface. Clinical trials are necessary to determine the usefulness of this technique.

[Modification of resin using reactive polymeric nanoparticles]. / Fogászati kompozitok gyantájának módosítása reaktiv polimer nanorészecskékkel.

Volumetric shrinkage during polymerization has always caused problems since polymer based composites are used as dental filling materials. This value has been reduced to 2-4 volume % with the improvement of dental filling materials and of suitable filling technique. The purpose of our study was to synthesize reactive polymeric nanoparticles which can be applied to modify the polymerization shrinkage of dental resin. It means that certain part of a commercial dental resin would be substituted with reactive polymeric nanoparticles as organic filler. According to our hypothesis the volume contraction would significantly be reduced by applying the modified resin with organic filler. Nanoparticles were prepared by free radical copolymerization from mono-, di- and trifunctional monomers in emulsion and organic solution. In emulsion their size distribution is narrow, but it is quite variable in solutions. The size, size distribution and reactivity of nanoparticles were examined, and these properties can be influenced by the mol ratio and concentration of the monomers. It was shown that the nanoparticles could be swollen by the matrix material and these build a unique structure that can be photo-polymerized. During polymerization the shrinkage of the copolymer can be considered zero, consequently the total contraction originates from the shrinkage of the matrix. In the modified resin the reactive groups of monomers and the pendant double bounds of nanoparticles were connected by covalent bond.