Diphenyliodonium Hexafluorophosphate Research Articles

Stability of the Dentin-Bonded Interface Using Self-Etching Adhesive Containing Diacrylamide after Bacterial Challenge.

Purpose/Aim: Acrylamides are hydrolytically stable at pH lower than 2, and were shown to preserve bonded interface integrity with two-step, total etch adhesives. The objective of this study was to leverage those two characteristics in self-etching primers containing the acidic monomer 10-MDP and test the microtensile bond strength before and after incubation with S. mutans incubation. Materials and Methods: Acidic primers (10 wt % 10-methacryloyloxydecyl dihydrogen phosphate─10-MDP; 45 wt % N,N-diethyl-1,3-bis(acrylamido)propane─DEBAAP, or 2-hydroxyethyl methacrylate─HEMA; 45 wt %, glycerol-dimethacrylate─GDMA) and adhesives (DEBAAP or HEMA/10-MDP/UDMA 45/10/45 wt %) were made polymerizable by the addition of 0.2 wt % camphorquinone, 0.8 wt % ethyl-4-dimethylaminobenzoate, 0.4 wt % diphenyliodonium hexafluorophosphate, and 0.1 wt % butylhydroxytoluene. Nonsolvated materials were characterized for flexural strength (FS), modulus (E), toughness, water sorption/solubility (WS/SL), contact angle, and vinyl conversion (DC). Viscosity was evaluated after adding 20 and 40 vol % ethanol to the primer and adhesive, respectively. The experimental materials or Clearfil SE Bond (CC─commercial control) were used to bond a commercial composite (Filtek Supreme) to the flat surface of human dentin. Microtensile bond strength (MTBS) was tested in 1 mm2 sticks for the 5 primer/bond combinations: CC (Clearfil Bond Primer and Bond), HH (HEMA/HEMA), DD (DEBAAP/DEBAAP), HD (HEMA/DEBAAP), and DH (DEBAAP/HEMA). Prior to testing, sticks were stored in water or biofilm-inducing culture medium with S. mutans for 1 week. Confocal images and FTIR-ATR evaluation evaluated the hybrid layer of the adhesives. Results were analyzed using Student's t-test (WS, SL, DC, contact angle, FS, E, toughness), one-way ANOVA/Tukey's test for viscosity, and two-way ANOVA/Tukey's test for MTBS (95%). Results: HEMA-based materials had lower contact angle (p = 0.004), higher WS (p < 0.001), and similar SL values compared to DEBAAP (p = 0.126). FS (p = 0.171) and E (p = 0.065) dry values were similar, but after one week of water storage, FS/E dropped more significantly for HEMA materials. Dry and wet toughness was greater for DEBAAP (p < 0.001), but it also had the greatest drop (46%). Clearfil bonds had the highest viscosity, followed by DEBAAP and HEMA, respectively (p = 0.002). For the primers, HEMA had the lowest viscosity (p = 0.003). As far as MTBS, all groups tested in water were statistically different when compared with HH (p < 0.001). After storage in biofilm, DH had the highest MTBS value, being statistically different from HH (p = 0.002), CC (p = 0.015), and DD (p = 0.027). Conclusions: The addition of a diacrylamide and its association with HEMA in self-etching adhesive systems provided greater bonding stability after bacterial challenge.

Flexural strength of dental adhesives with different photoinitiator systems.

The aim of this study was to investigate the flexural strength of dental adhesives containing different combinations of photoinitiators systems. The organic matrix of the experimental adhesives was created using a blend of monomers: 50% by weight bisphenol-A glycidyl methacrylate (BisGMA) and 50% triethylene glycol dimethacrylate (TEGDMA). The photoinitiators utilized were camphorquinone (CQ) and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), with diphenyliodonium hexafluorophosphate (DPIHFP) and 2-(Dimethylamino)ethyl methacrylate (DMAEMA) as co-initiators. These photoinitiators and co-initiators were integrated into the organic matrix at a concentration of 0.5% by mass, resulting in the formation of 6 groups (n=12): CQ/DMAEMA (control); CQ/DMAEMA/DPIHFP; BAPO; BAPO/DMAEMA; BAPO/DPIHFP and BAPO/DMAEMA/DPIHFP. Samples measuring 7 mm in length, 2 mm in width, and 1 mm in height were prepared and subjected to a three-point flexural test. Data were analyzed using one-way ANOVA with Tukey's post-hoc test (α=0.05). Results indicated that groups incorporating BAPO and DPIHFP exhibited higher flexural strength compared to those with CQ and DMAEMA. The BAPO/DPIHFP group achieved the highest mean flexural strength values (p<0.001). These findings suggest that using adhesive systems with alternative photoinitiators and co-initiators can lead to superior flexural strength compared to conventional systems. Key words:Photoinitiators, Dentin-bonding agents, Light-curing.

Achieving property enhancements in dental resin composites via reduced concentrations of camphorquinone within a ternary initiator system

ObjectivesThe study aimed to assess the impact of diphenyliodonium hexafluorophosphate (DPI) on the physicochemical properties of experimental resin composites (ECRs) featuring reduced concentrations of camphorquinone (CQ)/amine. MethodsFive concentrations of CQ (0.125, 0.25, 0.5, 0.75, and 1 mol%) with dimethylaminoethyl amine benzoate (EDAB) in a 1:2 mol% ratio (CQ:EDAB) were incorporated into a 50:50 mass% monomer blend of bisphenol glycidyl methacrylate (BisGMA) and triethyleneglycol dimethacrylate (TEGDMA). An additional 5 groups with the same CQ:EDAB concentrations had 0.5 mol% DPI added. Each resin group contained 60 wt% of 0.7 µm barium-alumino-silicate glass. Light transmission (n = 3), real-time degree of polymerization (n = 3), temperature change during polymerization (n = 5), polymerization shrinkage strain (n = 3), flexural strength, and modulus (n = 12), as well as water sorption and solubility (n = 5), were evaluated. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (α = 0.05). ResultsLight transmission was reduced in groups containing 0.125 and 0.25 mol% of CQ without DPI. DPI increased temperature, degree and rate of polymerization, despite the reduction in CQ/amine concentration. Additionally, there was an increase in polymerization shrinkage strain, flexural strength and modulus, and a reduction in water sorption and solubility in ECRs with DPI, even with lower concentrations of CQ/EDAB. SignificanceDPI improved the assessed properties of composites across various concentrations of CQ/EDAB, showing the benefit of reducing the quantity of CQ used without compromising the properties and curing of the resin composites.

Greenness and whiteness evaluated triple divisor-continuous wavelet transform spectrophotometric and advanced chemometric methods for the simultaneous determination of four photoinitiators in saliva and intravenous injection solution

Migration of photoinitiators from packaging materials and dental products in saliva presents an extensive real damage, particularly that emerges from packed food and dental products in saliva or from polyethylene packaging of the intravenous solutions which is extremely dangerous to human health and to the environment. In line with this, environmentally evaluated, advanced and reliable triple divisor combined with continuous wavelet transform (CWT) spectrophotometric method and nine chemometric methods were established and validated for the concurrent determination of four photoinitiators: Benzophenone, 4-Hydroxyacetophenone, Benzoin, and Diphenyliodonium hexafluorophosphate in saliva and in intravenous injection solutions. To our knowledge, this is the first spectrophotometric method for the analysis of the cited photoinitiators as well as the primary white method for the examination of those photoinitiators. Also, in this paper, the triple divisor method is combined with continuous wavelet transform for the first time. Triple divisor–CWT peak amplitudes were defined at 260.0, 275.8, 262.2 and 231.2 nm over a linear dynamic range of 0.50–13.00, 0.80–10.00, 1.5–30.00 and 1.00–28.00 μg/mL for Benzophenone, 4-Hydroxyacetophenone, Benzoin and Diphenyliodonium hexafluorophosphate, respectively. The nine chemometric methods incorporate the application of principle component regression (PCR), orthogonal partial least square (OPLS), ridge regression (RR) and artificial neural networks (ANN) methods along with different variable selections including genetic algorithm (GA-PCR, GA-OPLS and GA-RR) and interval selections (Interval-PCR and Interval-OPLS). Regarding the adopted chemometrics models, a multivariate multifactor experimental design based on the calibration curve range of the studied photoinitiators was considered to construct a calibration set consisting of eighteen mixtures while using seven mixtures for the validation set. The proposed methods were demonstrated to be sensitive, accurate, precise and reproducible throughout the validation process. The acquired results revealed that the proposed spectrophotometric and chemometric approaches could be effectively applied for the regular analysis of the cited photoinitiators in biological fluids as saliva and in intravenous solutions. The greenness of the proposed methods was assessed using two green metric tools enclosing Analytical Eco-scale & Analytical Greenness Assessment (AGREE), and a White Analytical Chemistry tool (WAC).

Lifetime-configurable soft robots via photodegradable silicone elastomer composites.

Developing soft robots that can control their own life cycle and degrade on-demand while maintaining hyperelasticity is a notable research challenge. On-demand degradable soft robots, which conserve their original functionality during operation and rapidly degrade under specific external stimulation, present the opportunity to self-direct the disappearance of temporary robots. This study proposes soft robots and materials that exhibit excellent mechanical stretchability and can degrade under ultraviolet light by mixing a fluoride-generating diphenyliodonium hexafluorophosphate with a silicone resin. Spectroscopic analysis revealed the mechanism of Si─O─Si backbone cleavage using fluoride ion (F-) and thermal analysis indicated accelerated decomposition at elevated temperatures. In addition, we demonstrated a robotics application by fabricating electronics integrated gaiting robot and a fully closed-loop trigger disintegration robot for autonomous, application-oriented functionalities. This study provides a simple yet novel strategy for designing life cycle mimicking soft robotics that can be applied to reduce soft robotics waste, explore hazardous areas, and ensure hardware security with on-demand destructive material platforms.

Preparation and properties of visible light-cured strippable film for radioactive decontamination

In this research, solutions of styrene-butadiene-styrene block copolymer (SBS) in 2-ethoxyethyl methacrylate (EOEMA) were used to prepare strippable films via rapid visible-light curing, where the mixture of camphorquinone (CQ), diphenylsilane (DPS) and diphenyliodonium hexafluorophosphate (Iod) was employed as the photoinitiating system, LED@405 nm, sunlight or household LED panel light as the light source and no any solvent was involved. The double bond conversion for pure EOEMA under LED@405 nm was firstly monitored by real-time FTIR and it reached 72% within 300 s. The rapid-curing of SBS/EOEMA solutions were systematically investigated and it was found that the solution with 16 wt% SBS became completely dried at the presence of 2.16 mol% crosslinker and 3.6 wt% photoinitiating system after 240 s irradiation under LED@405 nm. The tensile strength, elongation at break and glass transition temperature of the resultant strippable film were determined to be about 4.4 ± 0.5 MPa, 130 ± 11.2% and 6.9 °C, respectively, by mechanical properties testing and DSC measurements. Also, the decontamination efficiencies (DE) of household LED panel light/sunlight cured-strippable film for uranium nitrate on stainless steel, glass, and ceramic surface were evaluated to be higher than 90%. These results indicate that this rapid-curing strippable films would be a good candidate material for large-scale radioactive decontamination.

Development of the P-Arylation of Dithieno[3,2-b : 2',3'-d]phosphole with Aryl Iodonium Salts.

P-Arylation of dithieno[3,2-b : 2',3'-d]phosphole toward cationic phenyl phospholium species using diaryliodonium reagents was explored. Multiple conditions were tested to optimize the reaction, including variation of solvent, temperature, stoichiometry, time, and aryliodonium species employed. Initial use of diphenyliodonium chloride led to an unexpected dithienophosphole Cu(I) chloride complex that was characterized crystallographically. Alternatively, the use of diphenyliodonium hexafluorophosphate in ethanol under microwave conditions led to the successful isolation of the P-arylated target. The phenyl dithienophospholium species exhibits blue luminescence with a quantum yield of 100 % in solution that is considerably red-shifted in the solid state. The photophysics and solid-state organization of the new species were compared with those of a related methyl congener, showing distinct differences that are assigned to the nature of the carbon-based substituent at the phosphorus center, which was also confirmed by DFT calculations, and the supramolecular organization in the solid state.

Photoinitiated Cationic Ring-Opening Polymerization of Octamethylcyclotetrasiloxane.

Photochemical techniques have recently been revitalized as they can readily be adapted to different polymerization modes to yield a wide range of complex macromolecular structures. However, the implementation of the photoinduced cationic methods in the polymerization of cyclic siloxane monomers has scarcely been investigated. Octamethylcyclotetrasiloxane (D4) is an important monomer for the synthesis of polydimethylsiloxane (PDMS) and its copolymers. In this study, the cationic ring-opening polymerization (ROP) of D4, initiated by diphenyl iodonium hexafluorophosphate (DPI), has been studied. Both direct and indirect initiating systems acting at broad wavelength using benzophenone and pyrene were investigated. In both systems, photochemically generated protonic acids and silylium cations are responsible for the polymerization. The kinetics of the polymerization are followed by viscosimetry and GPC analyses. The reported approach may overcome the problems associated with conventional methods and therefore represents industrial importance for the fabrication of polysiloxanes.

Influence of bioactive particles and onium salt on the physicochemical properties of experimental infiltrants.

This study evaluated physicochemical properties of experimental infiltrants after addition of hydroxyapatite nanoparticles (HAp) or 58S bioactive glass (BAG) and diphenyliodonium hexafluorophosphate (DPI). The resin matrix was composed of TEGDMA/Bis-EMA (3:1), 0.5 mol% CQ, and 1 mol% EDAB. The blends received or not 0.5 mol% DPI and 10% wt BAG or HAp. Icon was used as commercial control. The groups were characterized by XRD, FT-IR spectrometry, and SEM before and after simulated body fluid (SBF) immersion for up to 7 days. Polymerization kinetics (n =3 ), water sorption and solubility (n=10), and viscosity (n = 3) were surveyed. For polymerization kinetics, the samples were polymerized for 5 min and the data were obtained from 40 s and 5 min. Statistical analysis was made using ANOVA and Tukey's test (a = 0.05). After 7 days of SBF immersion, XRD and FT-IR showed that the HAp crystalline phase was present only in the HAp groups. A lower degree of conversion (DC) and polymerization rate were observed for the Icon and BAG groups, whereas HAp showed higher values. For the BAG group, DPI increased polymerization rate and DC in 40 s. After 5 min, all groups presented DC above 80%. In groups with particles, the HAp groups exhibited higher viscosity, whereas DPI groups showed a decrease in viscosity. Icon had the highest water sorption. To conclude, BAG neither improved the physicochemical properties studied, nor did it show bioactive properties. The addition of DPI reduced viscosity caused by particle addition and also attenuated the DC decrease caused by BAG addition. The addition of bioactive particles to infiltrants should be seen with caution because they increase viscosity and may not bring major clinical improvements that justify their use. DPI might be indicated only if any component is added to the infiltrant to act as a compensation mechanism.

3 - Effect of Diphenyliodonium Hexafluorophosphate on Polymerization of Ion Releasing Glass

3 - Effect of Diphenyliodonium Hexafluorophosphate on Polymerization of Ion Releasing Glass

Sequential and Simultaneous Photoinduced Radical and Step-Growth Polymerizations of Carbazole Functional Styrene

Photoinduced radical and step-growth polymerizations of carbazole functional styrene (vinyl phenyl carbazole, VPC) by sequential and one-pot strategies have been investigated. The obtained polymers were characterized by FTIR, 1H-NMR, GPC, UV–Vis, PL, CV, and BET analyses. The theoretical charge distribution and HOMO–LUMO calculation by DFT were well-matched with those obtained from optical and electrochemical measurements. In the sequential approach, visible light-induced free-radical photopolymerization of VPC by using bisacyl phosphineoxide results in the formation of linear polymers with side-chain carbazole moieties. The resulting polymers exhibit a smooth surface as a consequence of decreasing crystallinity. As evidenced by TEM analysis, the subsequent photoiniated step-growth polymerization of the carbazole groups by using diphenyliodonium hexafluorophosphate (DPI) yields hyperbranched and cross-linked polymers with the microspheres on the surface. In the one-pot approach, concomitant photoinitiated free-radical and step-growth polymerizations by using DPI results in the formation of cross-linked polymers with dispersed distribution. The total nitrogen uptake of VPC-based polymers by using Brunauer–Emmett–Teller (BET) surface area was found to be between about 150 and 190 m2/g at 77 K.

Colorless phenanthroimidazole photoinitiators featuring tunable D-π-A configuration by frontier molecular orbital engineering

In this work, we employ phenanthroimidazole (PAI), a chromophore with high energy gap and superior light-absorbing ability as a building block to construct photoinitiators (PIs). Four PAI-based PIs, PAI-DBF, PAI-DBT, PAI-TPA and PAI-tCz, are designed and modulated by a frontier molecular orbital engineering by combining groups with different electron push-pull abilities to PAI moiety, leading to the highest occupied molecular orbital (HOMO) distribution localized on the PAI and arylamine, respectively. The new PIs can initiate free radical and cationic photopolymerization with diphenyl iodonium hexafluorophosphate under 365/405 nm LED irradiation. It is found that PAI-DBF and PAI-DBT show much higher photoinitiating performance because the PAI moiety is the main light absorber and electron-donating (HOMO-controlling) segment, leading to much higher photon utilization efficiency. In particular, the new PAI-based PIs are of large energy gaps without using a strong pull-push structure, which can be used to fabricate high-optical-quality products via photolithography. This work provides a guideline for constructing novel PIs for free radical and cationic photopolymerization.

Physicochemical properties of experimental resin-based composites using tris(trimethylsilyl)silane associated with diphenyl iodonium hexafluorophosphate (DPIHP) salt

The purpose was to evaluate the effect of tris(trimethylsilyl)silane (TTMSS) associated with diphenyl iodonium hexafluorophosphate (DPIHP) on the polymerization shrinkage stress (PSS), mechanical properties, color change (CC), and degree of conversion (DC) of resin-based composites (RBCs). Experimental RBCs containing 35 wt% of organic matrix (10.2 wt% BisGMA, 11.1 wt% BisEMA10 and UDMA and 2.1 wt% TEGDMA) and 65 wt% filler (13 wt% fumed silica and 52 wt% BaBSiO2) were assigned to six groups: control (0.2 wt% CQ, 0.5 wt% DMAEMA); TD05 (0.2 wt% CQ, 0.5 wt% TTMSS, 0.5 wt% DPIHP); TD10 (0.2 wt% CQ, 1 wt% TTMSS, 0.5 wt% DPIHP); DTD (0.2 wt% CQ, 0.25 wt% of DMAEMA, 0.25 wt% TTMSS, 0.5 wt% DPIHP); DT (0.2 wt% CQ, 0.25 wt% DMAEMA, 0.25 wt% TTMSS); and T05 (0.2 wt% CQ, 0.25 wt% TTMSS). The experimental formulations were submitted to the following tests: DC; PSS; CC; rate of polymerization (Rp); depth of cure by Knoop hardness; flexural strength; and flexural modulus. TTMSS showed no effect on the DC, Rp, and mechanical properties of the RBCs. DMAEMA reacted with TTMSS and reduced the Rp; the RBCs containing no DMAEMA showed no reduction in CC. DT showed the lowest PSS mean value among the groups. TTMSS differed from DMAEMA only when used in combination with DPIHP, which significantly improved the DC, maximum Rp, and mechanical properties of the RBCs tested. Based on the artificial ageing results, TTMSS was ineffective in reducing CC in the RBCs tested.

Photopatterning of Carbon Dots in Poly(vinyl alcohol) with Photoacid Generators.

Carbon dots (CDs) have drawn considerable attention owing to their attractive photoluminescence, advantageous chemical tolerance, good biocompatibility, and so on. However, it remains challenging to tune their photoluminescence spatially and temporally due to their high photostability. Herein, a viable approach to in-situ dialing the photoluminescence of CDs by using light in the presence of a photoacid generator (PAG, e.g., diphenyliodonium hexafluorophosphate) is demonstrated. Fluorescence quenching occurs upon light irradiation due to the protonation of pyridine and amino nitrogen atoms of CDs according to X-ray photoelectron spectroscopy and cyclic voltammetry. As such, blue, green, and red color fluorescent patterns of CDs are ready to form in poly(vinyl alcohol) by light irradiation under photomask. These patterns not only show a controlled preservation time under room light, but also can be erased on demand by flood UV irradiation, which are promising for advanced anti-counterfeiting such as shelf-life based security and erasable encryption.

Effect of MDP concentration and addition of iodonium salt on the dentin bond strength of experimental adhesives

Objective: The aim was to evaluate the bond strength of six experimental adhesives containing binary or ternaryphotoinitiator systems, associated with three different MDP concentrations (0-12wt%) after 12 months ofstorage in distilled water. Material and Methods: Experimental adhesives were prepared with: bis-GMA, UDMA,bis-EMA, TEGDMA, HEMA, BHT, and ethanol, containing binary (CQ/amine) or ternary (CQ/amine/DPIHFP(diphenyliodonium hexafluorophosphate) – 0.5wt%) photoinitiator systems. It was added to this composition0wt%, 6wt%, or 12wt% of MDP. The adhesive systems were applied following the etch-and-rinse protocol.Transparent cylindrical molds were placed on the hybridized dentin, filled with composite resin and light-cured.The specimens were stored in distilled water at 37oC for 24h or 12 months and submitted to a microshear bondstrength test (n=6). Data were analyzed by three-way ANOVA and Tukey’s test (a =5%). Results: For the binarysystem, after 12 months of storage, all bond strength values were similar. Regarding bond strength degradationover time, 6wt% and 12wt% MDP formulations showed more stable bond strength than 0wt% MDP. For the ternarysystem, all formulations (0wt%, 6wt% and 12wt%) showed stable bond strength over time. Conclusion: For thebinary photoinitiator system, the 6wt% and 12wt% MDP concentrations were able to keep bond strength stableover time, while for the ternary system, bond strength stability was achieved regardless the MDP concentration. KEYWORDSDental bonding; Dental photoinitiators; Dentin-bonding agents; MDP.

Incorporation of a polymerization catalyst for improved mechanical behavior and physicochemical characteristics of a light-cured pulp capping material

Objective: To evaluate the influence of the incorporation of a polymerization catalyst to a light-cured pulpcapping material on mechanical behavior and physicochemical characteristics. Material and Methods: Differentpercentages (2 wt%, and 4 wt%) of diphenyliodonium hexafluorophosphate (DPI) were incorporated into theUltra-Blend Plus, a resin-modified calcium-based cement. The material without incorporation of DPI (0 wt%)served as control. Degree of Conversion (DC), Flexural Strength (FS), Elastic Modulus (EM), Water Sorption(WSp), Solubility (Sl), and pH of eluate at 24-h, 72-h, and 7-day storage times were measured. One-way ANOVA/Tukey posthoc tests were used to analyze the data (p &lt;0.05). Results: For DC, FS, and EM, materials withdifferent % of DPI showed statistically significant differences, so that 0% provided the lowest values and 2% thehighest values. Materials with 0% and 2% of DPI provided statistically the lowest WSp, whilst material with 0%of DPI showed statistically the highest Sl. Conclusion: All materials provided statistically similar pH to eluatesregardless of storage time, although only materials with DPI at 2% and 4% maintained pH of eluates statisticallysimilar from 72 h to 7 days storage times. KEYWORDSLight-cured pulp capping material; Polymerization catalyst; Pulp capping.

Influence of TiO2 and ZrO2 Nanoparticles on Adhesive Bond Strength and Viscosity of Dentin Polymer: A Physical and Chemical Evaluation.

The present study aimed to formulate an experimental adhesive (EA) and reinforce it with 5 wt.% titanium dioxide (TiO2) or zirconium oxide (ZrO2) to yield 5% TiO2 and 5% ZrO2 adhesives, respectively, and then analyze the impact of this reinforcement on various mechanical properties of the adhesives. The EA contained a blend of monomers such as bisphenol A glycol dimethacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA), and ethyl 4-dimethylamino benzoate and camphorquinone. The EA included ethyl 4-dimethylamino benzoate and camphorquinone photo-initiators, and diphenyliodonium hexafluorophosphate (DPIHP) was also included to act as an electron initiator. The TiO2 and ZrO2 nanoparticles were incorporated into the EA post-synthesis. To characterize the filler nanoparticles, scanning electron microscopy (SEM) and line-energy dispersive X-ray (EDX) spectroscopy were performed. The adhesives were characterized by analyzing their rheological properties, shear-bond strength (SBS), and interfacial failure types. Further, the resin–dentin interface was also analyzed via SEM. The TiO2 nanoparticles were spherically shaped on the SEM micrographs, while the ZrO2 nanoparticles were seen as non-uniformly shaped agglomerates. The EDX mapping demonstrated the presence of Ti and oxygen for TiO2 and Zr and oxygen for the ZrO2 nanoparticles. Both 5% TiO2 and 5% ZrO2 adhesives revealed decreased viscosity as compared with the EA. The 5% TiO2 adhesive demonstrated higher SBS values for both non-thermocycled (NTC) and thermocycled samples (NTC: 25.35 ± 1.53, TC: 23.89 ± 1.95 MPa), followed by the 5% ZrO2 adhesive group (NTC: 23.10 ± 2.22, TC: 20.72 ± 1.32 MPa). The bulk of the failures (>70%) were of adhesive type in all groups. The SEM analysis of the resin–dentin interface revealed the development of a hybrid layer and resin tags (of variable depth) for the EA and 5% TiO2 groups. However, for the 5% ZrO2 group, the hybrid layer and resin tag establishment appeared compromised. Reinforcement of the EA with TiO2 or ZrO2 caused an increase in the adhesive’s SBS (with the 5% TiO2 group demonstrating the highest values) in comparison with the EA (without nanoparticles). However, both nanoparticle-containing adhesives revealed decreased viscosity compared with the EA (without nanoparticles). Further studies investigating the impact of diverse filler concentrations on the properties of adhesives are suggested.

Improvement on properties of experimental resin cements containing an iodonium salt cured under challenging polymerization conditions

ObjectiveThe use of resin cements in clinical practice entails photopolymerization through prosthetic devices, which precludes light penetration. The objective of this study was to modify experimental resin cements (ERCs) with diphenyliodonium hexafluorophosphate (DPI) in an attempt to improve chemical and mechanical properties of materials cured with reduced irradiance and final radiant exposure. MethodsA co-monomer base containing a 1:1 mass ratio of 2.2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bis-GMA) and triethyleneglycol dimethacrylate (TEGDMA) was prepared, with 1mol% of camphorquinone and 2mol% of ethyl 4-(dimethylamino)benzoate as initiator system. The resin was divided into 4 fractions according to the DPI concentrations (0, 0.5, 1 and 2mol%). The challenging polymerization condition was simulated performing the light activation (12, 23 and 46s) through a ceramic block (3mm thick). The irradiance was assessed with a calibrated spectrometer (1320mW/cm2), resulting in three levels of radiant exposure (0.58, 1.1 and 2.2J/cm2). The polymerization kinetics was evaluated in real-time using a spectrometer (Near-IR). Water sorption and solubility was analyzed and the cohesive strength of resins obtained through the microtensile test. Polymerization stress was assessed by Bioman method. ResultsResins containing DPI had higher degree of conversion and rate of polymerization than the control (without DPI). The use of DPI reduced water sorption and solubility, and led to higher cohesive strength compared to resins without the iodonium salt. However, the stress of polymerization was higher for experimental resins with DPI. SignificanceEven under remarkably reduced irradiance, cements containing a ternary initiating system with an iodonium salt can present an optimal degree of conversion and chemical/mechanical properties.

Positive Synergistic Effect of Adhesives and Resin Cements Containing an Iodonium Salt on Bonding of Fiber Posts.

To evaluate the push-out bond strength (PBS) of glass-fiber posts (GFP) in different root canal zones (cervical, middle, and apical), bonded with experimental simplified adhesives (ESAs) containing different initiator systems (camphorquinone [CQ] or phenylpropanodione [PPD]) with or without diphenyl iodonium hexafluorophosphate (DPI), in combination with a DPI-containing composite cement. ESA blends were prepared with bisphenol glycidyl methacrylate (bis-GMA), triethylene glycol dimethacrylate (TEG-DMA), 1,3-glycerol dimethacrylate (GDMA), 2-hydroxyethyl methacrylate (HEMA), and ethanol, then divided into 12 experimental groups (n = 10) according to the initiator systems (CQ, PPD, or CQ + PPD) and the presence or absence of DPI. The roots of 120 extracted bovine incisors were prepared with #5 Largo drills and the GFP were cemented with each ESA and experimental composite cements containing 0.05 mol% of DPI. The push-out bond strength (PBS) test was performed after 24 h of storage. Failure patterns were analyzed under a stereomicroscope. Data were analyzed with split-plot two-way ANOVA and Tukey's test (α = 0.05). PBS was significantly higher for DPI-containing ESAs in all regions evaluated, with the group containing 0.5 CQ + 1 PPD + 0.5 DPI exhibiting the highest PBS. There was no statistically signficant difference among groups without DPI. Most failures were classified as adhesive at the cement-dentin interface. The combination of an adhesive and a composite cement containing DPI salt can improve GFP bonding to root dentin, even in the apical region.

An initiating system with high efficiency for PEGDA photopolymerization at 532 nm

Nanogels based Polyethylene glycol diacrylate (PEGDA) attracted much attention due to their promising application in drug delivery and tissue engineering. Here, PEGDA photopolymerization at 532 nm with different initiating systems was investigated. Nanogels can be obtained using single 2′,4′,5′,7′-tetrabromofluorescein disodium salt (EY) as the photoinitiator. To increase the polymerization rate, EY, triethanolamine (TEOA), and diphenyl iodonium hexafluorophosphate (DPI) were investigated as a three-component initiating system. With that initiating system, the conversion of PEGDA double bond was higher than 90 % in 1 min at extremely low irradiation energy density (P= 0.95 mW/cm2). However, the conversion of PEGDA double bond was only 51.5 % in 1 min at the same irradiation energy density when using EY and TEOA as two-component initiating system. Subsequently, the corresponding mechanism of the three-component (EY-TEOA-DPI) initiating system was illustrated. DPI might participate in two ways of photooxidation and reduction, which dramatically improved the polymerization rate. The EY-TEOA-DPI initiating system is promising to be applied in the preparation of multifunctional hydrogels.