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Properties of 2,3-butanedione and 1-phenyl-1,2-propanedione as new photosensitizers for visible light cured dental resin composites
Abstract
Two 1,2-diketones, 1-phenyl-1,2-propanedione (PD) and 2,3-butanedione (BD) were investigated as new visible light photosensitizers for formulating a dental resin composite of bis-GMA in order to improve the physical properties of the resin composite. The results were then compared with those of camphorquinone (CQ), the most widely used photosensitizer. Photodecomposition of the photosensitizers with and without amine was studied through UV absorption spectroscopy. The photopolymerization efficiency of bis-GMA containing the photosensitizer increased with irradiation time and with the amount of photosensitizer. The increase was in the order: BD<CQ<PD. The experimental resin composite of bis-GMA containing BD or PD showed better mechanical properties than that which contained CQ. The reason for the higher mechanical properties of the resin composite containing BD or PD as compared with that containing CQ is discussed through the study of a model reaction. It was observed that BD or PD serves not only as a photosensitizer but also as a crosslinking agent.
... In the recent studies, several types of new photo initiators such as 2,3 butanedione, 1-phenyl-1,2-propanedione and hexafluoroantimonate p-octyloxy-phenyl iodonium have been evaluated [15,16]. CQ is the most commonly used photo initiator in light-cure composite resins [15]. ...
... In the recent studies, several types of new photo initiators such as 2,3 butanedione, 1-phenyl-1,2-propanedione and hexafluoroantimonate p-octyloxy-phenyl iodonium have been evaluated [15,16]. CQ is the most commonly used photo initiator in light-cure composite resins [15]. CQ is naturally yellow causing problems in color matching. ...
... CQ is naturally yellow causing problems in color matching. This limits the application of its higher concentrations and consequently, the DC and curing depth [15]. The 2,3 butanedione (Diketone BD) is a viscous liquid. ...
... Currently, the most used photoinitiator for odontological resinous materials is camphorquinone (CQ), although it has some disadvantages, such as its intense yellow color, which affects the incorporation of the brightly colored resins that are widely used in whitened teeth. Additionally, it exhibits a low polymerization efficiency [17]. Other photoinitiators, such as phenyl propanedione (PPD), which is less dependent on tertiary amines to generate free radicals, are being tested to bypass such problems. ...
... Other photoinitiators, such as phenyl propanedione (PPD), which is less dependent on tertiary amines to generate free radicals, are being tested to bypass such problems. In addition to its bright yellow color, PPD is a liquid at room temperature, which aids in incorporating higher quantities into composite resins [17][18][19][20]. ...
... Some studies report better DC for resins containing only PPD than for resins with CQ [5,13,17,18]. According to Park et al. [18] and Sun and Chae [17], there may be a synergic effect to combining CQ + PPD due to a second form of free radical generation via the abstraction of photons and photocleavage. ...
This study aimed to analyze the kinetic parameters of two monomers using attenuated total reflectance Fourier transform infrared (ATR-FTIR): 2,2-bis-[4-(2-hydroxy-3-methacryloxypropyl-1-oxy)-phenyl] propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA). The following were calculated to evaluate the kinetic parameters: maximum conversion rate ( R p m a x ), time at the maximum polymerization rate ( t m a x ), conversion at R p m a x , and total conversion recorded at the maximum conversion point after 300 s. Camphorquinone (CQ) and phenyl propanedione (PPD) were used in this study as photoinitiators, whereas N,N-dimethyl-p-toluidine (DMPT) amine was used as a coinitiator. LED apparatus and halogen lamp were used in turn to evaluate the effect that light source had on the monomer kinetics. The mass concentration ratio for the three resin preparations was 0.7 : 0.3 for Bis-GMA and TEGDMA: R1 (CQ + DMPT), R2 (PPD + DMPT), and R3 (PPD + CQ + DMPT). The PPD association with the CQ photoinitiator altered the polymerization kinetics compared to a resin containing only the CQ photoinitiator. The light sources exhibited no significant differences for t m a x of R1 and R3. Resins containing only the PPD initiator exhibited a higher t m a x than those containing only CQ. However, the R p m a x decreased for resins containing the PPD photoinitiator.
... However, the two carbonyl radicals in CQ are structurally connected to each other and the probability of their recombination in CQ is great. 18 The consequent low polymerization efficiency of CQ results in relatively low mechanical properties without relatively high CQ concentrations and/or relatively long exposure times, as well as possible toxic effects from unreacted residual monomers. 17 Meanwhile, the type of amine directly affects the generation of free radicals. ...
... 22 Therefore, there has been substantial effort to improve these binary photoinitiation systems by the use of alternative photosensitizers, and various amine reducing agents. 18,[23][24][25] In addition, the claim of synergistic effects when two or more initiators are used together has also been reported. Park et al., observed that equal amounts of CQ and PPD produced a higher DC than the sum of the effects of CQ and PPD used separately. ...
... Compounds derived from acylphosphine oxides (monoacylphosphine oxide [MAPO] and bisacylphosphine oxide [BAPO]) and α-diketones (PPD) were used in adhesives and composite resin formulations to improve the polymerization kinetics and lessen the photoyellowing effects. 18,26 Unlike CQ, the absorption peak of these compounds is in the near UV region and extends slightly into the visible. 16,27 Shin and Rawls reported that dental resin with ternary system of CQ/OPPI/CQ accelerate cure rate, increase conversion, reduce initial color and increase color stability. ...
Objectives
This study evaluated the effect of camphorquinone (CQ)-amine ratio on the C=C double bond conversion of resins with binary and ternary photoinitiation systems.
Materials and Methods
Two monomer mixtures (37.5 Bis-GMA/37.5 Bis-EMA/25 TEGDMA) with binary systems (CQ/DMAEMA in weight ratio, group A [0.5/1.0] and B [1.0/0.5]) and four mixtures with ternary system (CQ/OPPI/DMAEMA, group C [0.1/1.0/0.1], D [0.1/1.0/0.2], E [0.2/1.0/0.1] and F [0.2/1.0/0.2]) were tested: 1 : 2 or 2 : 1 CQ-amine ratio in binary system, while 1 : 1 ratio was added in ternary system. The monomer mixture was cured for 5, 20, 40, and 300 sec with a Demetron 400 curing unit (Demetron). After each exposure time, degree of conversion (DC) was estimated using Fourier transform infrared (FTIR) spectrophotometer (Nicolet 520, Nicolet Instrument Corp.). The results were analyzed by ANOVA followed by Scheffe test, with p = 0.05 as the level of significance.
Results
DC (%) was expressed in the order of curing time (5, 20, 40, and 300 sec). Group A (14.63 ± 10.42, 25.23 ± 6.32, 51.62 ± 2.69, 68.52 ± 2.77); Group B (4.04 ± 6.23, 16.56 ± 3.38, 37.95 ± 2.79, 64.48 ± 1.21); Group C (16.87 ± 5.72, 55.47 ± 2.75, 60.83 ± 2.07, 68.32 ± 3.31); Group D (23.77 ± 1.64, 61.05 ± 1.82, 65.13 ± 2.09, 71.87 ± 1.17); Group E (28.66 ± 2.92, 56.68 ± 1.33, 60.66 ± 1.17, 68.78 ± 1.30); Group F (39.74 ± 6.31, 61.07 ± 2.58, 64.22 ± 2.29, 69.94 ± 2.15).
Conclusion
All the monomers with ternary photoinitiation system showed higher DC than the ones with binary system, until 40 sec. Concerning about the effect of CQ-amine ratio on the DC, group A converted into polymer more than group B in binary system. However, there was no significant difference among groups with ternary system, except group C when cured for 5 sec only.
... Free-radical polymerisation of methacrylate monomers used in dental RBCs is initiated by the excitation of suitable photoinitiator systems by light despite the monomer itself being capable of forming reactive species although this is deemed inefficient (Sun and Chae, 2000;Shin and Rawis, 2009). The photoinitiator chemistry affects light transmission, polymerisation kinetics and overall conversion of monomer to polymer thus affecting material properties (Yoshida and Greener, 1994;Rueggeberg et al., 1997;Ogunyinka et al., 2007;Musanje et al., 2009). ...
... These radical pairs can undergo cage escape (where the radical site moves around the structure) to form photo-decomposed products which results in a decrease in the concentration of the active camphoroquinone molecules thus decreasing absorbance and the b-value of the CIELAB coordinates. However, the two carbonyl radicals in camphoroquinone remain structurally connected to each other and the probability of recombination to reform camphoroquinone molecules is great (Sun and Chae, 2000). ...
... Irradiation leads to the decomposition of the photoinitiator system over time until the photoinitiator is consumed (Figure 3.1.4). The amine accelerator serves to increase the rate of photodecomposition (Sun and Chae, 2000) although the rate of decomposition is much slower than in Lucirin TPO (Figure 3.1.5). The rate of decomposition and absorbance for both photoinitiator is proportional to their concentrations as the likelihood of excitation is greatly increased when the molar concentrations of absorbing species (photoinitiator) are increased. ...
... Some studies have shown that the PPD molecule is more efficient when it forms free radicals by photocleavage, which is independent of the addition of a co-initiator 3,24,26 . When a co-initiator is added, such as the DMAEMA, the decomposition of the initiator molecule decreases, reducing its molar extinction coefficient and diminishing the polymerization potential 27 . In the other hand, the DC od PPD was higher than the control and CQ groups, probable due to the fact that it has a higher decomposition rate in comparison to the champhorquinone, favoring the production of free radicals 27 . ...
... When a co-initiator is added, such as the DMAEMA, the decomposition of the initiator molecule decreases, reducing its molar extinction coefficient and diminishing the polymerization potential 27 . In the other hand, the DC od PPD was higher than the control and CQ groups, probable due to the fact that it has a higher decomposition rate in comparison to the champhorquinone, favoring the production of free radicals 27 . ...
Purpose: The aim of this study was to evaluate the physical-mechanical properties of experimental orthodontic resins, containing different photoinitiators systems and photoactivated through a ceramic bracket, using a high irradiance and wide spectrum light emitting diode curing unit. Methods: Experimental resin composites (50:50 BisGMA/TEGDMA: 60% feldspar silanized particles) were formulated with different photoinitiators according to the following groups: phenylpropaneamine + amine DMAEMA (PPD), camphorquinone + amine DMAEMA (CQ) or bisacylphosphinic oxide (BAPO). A commercial orthodontic resin composite (Transbond XT) was used as control. The materials were then distributed into two groups, according to the photoactivation condition: directly or through a ceramic bracket, for 20s at 1200 mW/cm2. In the sequence, fifteen composite disks, 5mm of diameter and 1mm of thickness, were made for each of the eight groups. The degree of conversion (DC) was determined by means of Raman spectroscopy. Knoop hardness (KHN) was measured immediately after confection and after 24 hours of storage in 100% ethanol for indirect crosslink density (CLD) evaluation. Data were analyzed using two-way ANOVA followed by Tukey's test (α = 0.05). Results: The DC of the BAPO composite was significantly higher in comparison to the other materials, regardless of the photoactivation condition. The KHN was significantly different between the composite groups in the following sequence: BAPO> Transbond XT> CQ> PPD. The direct photoactivation presented higher KHN values, regardless the type of material. Regarding the CLD, there was statistical difference only for the material factor, as follow: PPD> BAPO = CQ = Transbond XT. Conclusion: The photoinitiator type and the photoactivation condition had a significant influence on the physical-mechanical properties of the evaluated materials.
... Related to these observations, bimolecular photoinitiator systems comprised of an αdiketone and a tertiary amine have been used as dental restorative materials [17,18]. A mechanism involving a triplet exciplex has been suggested to be the reactive intermediate preceding an electron transfer [17,18], although no specific evidence for such a complex has been shown. ...
... Related to these observations, bimolecular photoinitiator systems comprised of an αdiketone and a tertiary amine have been used as dental restorative materials [17,18]. A mechanism involving a triplet exciplex has been suggested to be the reactive intermediate preceding an electron transfer [17,18], although no specific evidence for such a complex has been shown. Regardless, electron transfer from the tertiary nitrogen lone-pair to the α-dicarbonyl group is the most plausible mechanism for the initial step. ...
Three structurally related gelators, each containing octadecyl chains, an α-diketo group at the 9,10 positions, and each with a different N-amide group—isobutyl (DIBA), isopentyl (DIPA) or N-(2-(dimethylamino)ethyl) (DMEA)—have been synthesized. Their neat structures as well as the thermal mechanical, and photophysical properties in their gel states with various liquids have been investigated. The gelator networks of DIBA and DIPA in octane, hexylbenzene and silicone oil consist of bundles of fibers. These gels are partially thixotropic and mechanically, thermally (to above their melting or silicone oil gelation temperatures), and photophysically stable. They are mechanically and thermally stronger than the gels formed with DMEA, the gelator with a tertiary amine group. The lone pair of electrons of the tertiary amine group leads to an intra-molecular or inter-molecular charge-transfer interaction, depending on whether the sample is a solution, sol, or gel. Neat, solid DMEA does not undergo the charge-transfer process because its amino and diketo groups are separated spatially by a large distance in the crystalline state and cannot diffuse into proximity. However, the solution of DIPA upon the addition of triethylamine becomes unstable over time at room temperature in the dark or (more rapidly) when irradiated, which initiates the aforementioned charge-transfer processes. The eventual reaction of the gelators in the presence of a tertiary amine group is ascribed to electron transfer from the lone-pair on nitrogen to an α-diketo group, followed by proton transfer to an oxygen atom on the anion radical of the α-diketo group from a methyl or methylene group attached to the nitrogen atom of the cation radical. Finally, the formation of an α-diketyl radical leads to irreversible electronic and structural changes that are observed over time.
... The max of PPD, BD, and CQ are, respectively, 393 nm, 419 nm, and 468 nm. [36]. max of CQ is in range of the light curing units output leading to the higher degree of polymerization, and consequently higher shrinkage strain, in CQ-A containing adhesives. ...
... Photoinitiators exhibiting higher E, will result in an increased yield of free radicals, ultimately leading to an improved curing efficiency of the polymerization system [37]. Sun and Chae [36] reported values of 20, 50 and 80 (Lmol −1 cm −1 ), respectively, for molar extinction coefficients of PPD, BD and CQ. Therefore, the higher shrinkage strains, and consequently higher degree of polymerization conversions, of CQ and BD containing adhesives may also be attributed to their higher molar extinction coefficient. ...
The aim of this study was to prepare and characterize eugenol-loaded oligochitosan nanoparticles (Eu/Oc) via sol–gel and emulsion/sol–gel methods using tripolyphosphate (TPP) as cross-linking agent. The effect of different parameters on the particle size of nanoparticles was investigated. Purified oligochitosan (Oc) was first characterized by FT-IR and TGA methods. The increase in TPP concentration, Oc concentration, the mass ratio of Oc to TPP, and diameter of the reactor resulted in larger particles while increasing the stirring rate decreased the particle size down to a minimum level. The rate of the addition of TPP solution showed no significant effect on the particle size. The yield of nanoparticle formation was calculated as 52 ± 3%. The stability of the dispersion containing the produced nanoparticles was also investigated. The optimum particle size and the loading yield of eugenol in nanoparticles were calculated as 270 ± 45 nm and 10%, respectively. In emulsion method, emulsifier and cross-linker concentration play important roles in nanoparticles’ size and should be optimized. The results showed that particle size increases at concentrations lower and higher than the optimum value. The optimum particle size in this method was obtained as 123 ± 23 nm.
... When a compound absorbs light at a particular wavelength, in addition to λ max , it also exhibits a dip or "trough" in the plot of absorbance versus wavelength [64]. The dip or trough is a decrease in absorbance after the maximum absorbance point (λ max ) of the compound [65]. This information can also be used to identify the compound and to determine its concentration in a sample [42]. ...
Aims
This study investigates the composition of tattoo pigments to ensure their safe application in tattoo art, evaluating the viability of UV-Vis and FT-IR spectroscopy, coupled with chemometrics, for predicting pigment contents in tattoo inks.
Background
Analyzing pigments in tattoo inks poses challenges in maintaining quality. This study addresses the difficulties by proposing the use of UV-Vis and FT-IR spectroscopy, along with chemometrics, as potential solutions for effective monitoring.
Objective
The aim of this study was to determine the content of red (PR) 170/254 and pigment blue (PB) 15:3 in tattoo inks from diverse suppliers and examine the distinct chemical structures and existing impurities in the samples using UV-Vis and FT-IR spectroscopy, employing regression models for data analysis.
Method
We collected UV-Vis and FT-IR spectra from the tattoo ink samples and utilized regression models for data analysis. We assessed correlations across spectrum areas, emphasizing coefficients of determination for cross-validation. Subsequently, we compared the results obtained from both spectroscopic methods in terms of pigment identity and evaluated the suitability of UV-Vis spectroscopy for analyzing changes in pigment concentration and structural evolution. Finally, we employed chemometric modeling to enhance predictions of FT-IR parameters, particularly in the functional group and fingerprint region of the spectra.
Results
Significant correlations were observed across both UV-Vis and FT-IR spectrum areas, with coefficients of determination for cross-validation exceeding 0.7 for most parameters. Both spectroscopic methods yielded nearly identical results regarding pigment identity. UV-Vis spectroscopy proved to be a suitable method for analyzing changes in pigment concentration and structural evolution. Chemometric modeling enhanced predictions of FT-IR parameters, particularly in the functional group and fingerprint region of the spectra.
Conclusion
The study underscores the significance of utilizing UV-Vis and FT-IR wavelengths from various suppliers to determine pigment structures in tattoo inks. The consistent and comparable results from both spectroscopic methods highlight their efficacy in characterizing pigments. UV-Vis spectroscopy, in particular, emerged as a valuable tool for assessing changes in pigment concentration and structural evolution. The improved predictions through chemometric modeling further emphasize the utility of these analytical approaches in ensuring the safe use of tattoo inks in the art of tattooing.
... where the vinyl methacrylate and aromatic internal standard absorptions are represented before (A 0 vinyl , A 0 aromatic ) and after (A ′ vinyl , A ′ aromatic ) cure [39]. ...
Objective
: Composites with remineralizing and antibacterial properties are favorable for caries inhibition. The objectives of this study were to develop a new bioactive nanocomposite with remineralizing and antibiofilm properties by incorporating dimethylaminohexadecyl methacrylate (DMAHDM) and nano-calcium fluoride (nCaF2).
Methods
: nCaF2 was produced via a spray-drying method and integrated at 15% mass fraction into composite. DMAHDM was added at 3% mass fraction. Mechanical properties and F and Ca ion releases were assessed. Colony-forming units (CFU), lactic acid and metabolic activity of biofilms on composites were performed.
Results
: The new composites had flexural strengths of (95.28±6.32) MPa and (125.93±7.49) MPa, which were within the ISO recommendations. Biofilm CFU were reduced by 3-4 log (p<0.05). The composites achieved high F releases of (0.89±0.01) mmol/L and (0.44±0.01) mmol/L, and Ca releases of (1.46±0.05) mmol/L and (0.54±0.005) mmol/L.
Conclusions
: New nanocomposites were developed with good mechanical properties, potent antibacterial activity against salivary biofilms, and high F and Ca ion releases with potential for remineralization.
Clinical Significance
: Novel nanocomposites using nCaF2 and DMAHDM were developed with potent antibacterial and remineralizing effects and high F and Ca ion releases. They are promising to inhibit recurrent caries, promote remineralization, and possess long-term sustainability.
... Top photoinitiators, because in both tests several factors influence the results, besides the degree of monomer conversion, such as cross-link density [12,13,17]. Despite PPD photoinitiator promotes slow polymerization of composite resins, and therefore low cross-link density [20], it is considered a cross-link density agent creating more cross-linked polymer structure in composite resins [22]. This could explain the similar results of the PPD-and CQ-based experimental composite resins in diametral tensile strength and Young modulus tests. ...
This study evaluated the physico-mechanical properties of experimental composite resins made with different resin matrix and light-curing units. Experimental composite groups were divided according to monomers (BisGMA + TEGDMA-BT and BisGMA + BisEMA + UDMA + TEGDMA-BBUT) and photoinitiator system (camphorquinone-CQ and 1-phenyl-1,2-propanedione-PPD). A quartz tungsten halogen (QTH) or light-emitting diode (LED) were used to light cure all materials. Knoop microhardness (n = 10) was determined using Knoop microhardness test. Compressive strength, diametral tensile strength, and Young modulus (n = 7) were obtained using a universal testing machine at crosshead speed of 1.0 mm/min. The data were submitted to a three-way ANOVA and the Tukey post-hoc test (α = 0.05). QTH presented the highest total irradiance values and similar total radiant exposure to LED. For the compressive strength test, BT-PPD light-cured with LED group showed the lowest mean value. BT-CQ light-cured with LED group exhibited the lowest diametral tensile strength results. The BBUT-composite resins presented lowest Young modulus values, with no statistical difference between light-curing units (QTH and LED) and photoinitiators system (CQ and PPD). Application of QTH or LED in BT-based composite resins with PPD photoinitiator generated suitable results regarding the physico-mechanical properties.
... Therefore, PPD is an alternative to camphorquinone/amine systems initiating radical photopolymerization processes. The research proved that the higher mechanical properties of the model resin composite containing PPD compared with that containing CQ are obtained [138,139]. Moreover, the study shows that PPD is useful not only for photosensitizers but also for photocrosslinking agents for dental composite resins with similar efficiency to CQ [140]. ...
The photoinduced polymerization of monomers is currently an essential tool in various industries. The photopolymerization process plays an increasingly important role in biomedical applications. It is especially used in the production of dental composites. It also exhibits unique properties, such as a short time of polymerization of composites (up to a few seconds), low energy consumption, and spatial resolution (polymerization only in irradiated areas). This paper describes a short overview of the history and classification of different typical monomers and photoinitiating systems such as bimolecular photoinitiator system containing camphorquinone and aromatic amine, 1-phenyl-1,2-propanedione, phosphine derivatives, germanium derivatives, hexaarylbiimidazole derivatives, silane-based derivatives and thioxanthone derivatives used in the production of dental composites with their limitations and disadvantages. Moreover, this article represents the challenges faced when using the latest inventions in the field of dental materials, with a particular focus on photoinitiating systems based on iodonium salts. The beneficial properties of dental composites cured using initiation systems based on iodonium salts have been demonstrated.
... 7-10 Single-wave and polywave light-curing units range from 2,000 up to 3,200 mW/cm 2 ; single-wave LEDs emit a single wavelength emission peak, 11 which is different than polywave units that emit a multiplewavelength emission, polymerizing camphorquinone and other types of photoinitiators, 12 such as ivocerin and phenylpropanedione. 13 However, studies have shown that not all light-curing units in dental practices emit a sufficient intensity to ensure adequate polymerization of resin material. This unsatisfactory light intensity can be caused by various factors, such as contamination of the light guide, damage to the fiber optic bundle, reduced light output after repeated sterilizations, and dwindling battery power. 1 This study aimed to evaluate the influence of different intensities of light-curing units and distinct shades of the composite resin on the color stability and microhardness of resin materials. ...
The purpose of this study was to evaluate the intensity of light-curing units and its relationship with the color stability and microhardness of composite resins with different shades subjected to a thermocycling procedure. Eighty blocks (5.0 × 2.0 mm) of TPH Spectrum composite resin (Dentsply Sirona) were produced and distributed into four groups according to the light-curing units (EC 450, ECEL; Valo, Ultradent) and color of the resin material (A3; C3) (n = 20). Within each group, color stability was measured on half the sample (n = 10) using a UV-2450 visible UV spectrophotometer (Shimadzu), and Knoop hardness was measured on the other half (n = 10) using an HMV 2000 microhardness tester (Shimadzu) before and after thermocycling (12,000 cycles, 5°C and 55°C). Mann-Whitney test was performed on the color stability data; the microhardness data were analyzed using a three-way analysis of variance (ANOVA) and Tukey test (α = .05). The ANOVA results showed that thermocycling, distinct light intensity, and different colors of resin materials influenced the microhardness of the composite resins, which was evidenced by the A3 composite resin light-cured with a Valo polywave showing higher hardness values. There was no statistical difference in the color stability of the A3 composite resin; however, the C3 composite resin light-cured with an EC 450 singlewave light-curing unit showed higher color alteration values. In general, the Valo polywave light-curing unit imparted better mechanical property and color stability to both shades of the composite resins. The different shades of resin material influenced the hardness of the composite resins. Therefore, the light intensity of the light-curing units should be evaluated and monitored, as the amount of light intensity will interfere in the quality and longevity of resin restorations.
... 32,[43][44][45][46][47][48] Later on, a different photo-initiator (monoacylphosphine oxide (Lucirin TPO)) system has been introduced that is designed to improve polymerization kinetics and reduce photo-yellowing effects. 45,[49][50][51][52][53] The use of Lucirin eliminated the amine group, thereby increasing color stability upon aging. 25,45,48,[54][55][56] IPS Empress Direct (Ivoclar Vivadent, Schaan, Liechtenstein), a resin-based material, was introduced to the market. ...
Introduction
Exceptional optical properties characterize teeth. As such, an esthetic restorative material should enable the dental professional to imitate the optical properties of natural teeth accurately. IPS Empress Direct was introduced to the market with the claim that it can mimic optically dental tissues with superior clinical performance.
Aim
To evaluate the ability of IPS Empress Direct to mimic tooth appearance and color and resist staining.
Materials and methods
Three disc specimens were prepared for each shade of enamel and dentin of Lucirin-based composite, IPS Empress Direct (Ivoclar Vivadent) (A1, A2, A3, B1, and B2) (total of 60). The specimens were submitted to colorimetric evaluation in comparison after immersion in 10 different solutions (coffee, coffee with sugar, coffee with milk, red tea, red tea with sugar, red tea with milk, tomato juice, pomegranate juice, coke, and distilled water as a control group) for 4 weeks using spectrophotometric analysis.
Results
After plotting the data and conducting linear regression analyses, IPS Empress showed high potential in mimicking the optical properties of natural tooth color according to the CIE color space. Three solutions showed a change in color higher than 3, coffee, coffee with sugar, and red tea. All other solution showed changes in color that are acceptable clinically.
Conclusion
IPS Empress Direct can satisfactory mimic teeth appearance and color while manifesting high stability of color resisting staining upon clinical aging.
... The photoinitiator 1-Phenyl-1, 2-Propanedione (PPD) was developed to solve the yellowing effect and improve the polymerization process (Park et al., 1999;Sun and Chae, 2000;Asmussen and Peutzfeldt, 2002).This photo initiator could be used alone or in combination with CQ. The absorption peak of these molecules is at shorter wavelengths within the ultraviolet spectrum the (maximum wavelength ≈ 410 nm) (Stansbury, 2000;Uhl et al., 2003). ...
... We performed additional experiments to prove that UVIStar resin is optimized regarding both mechanical and optical properties. For example, we replaced DPTBP with three other commonly used VIS light-curable photoinitiators (1-phenyl-1,2-propanedione (PPD), camphorquinone (CQ), and phenylbis (2,4,6-trimethylbenzoyl)phosphine oxide (PTBP)) at concentrations of 4 mg mL −1 , 2 mg mL −1 , and 4 mg mL −1 , respectively 27,28 . The results showed that all the resin formulations obtained after replacing the UVIStar photoinitiator (PPD, CQ, and PTBP) exhibited a nontransparent yellow color (Supplementary Fig. S1). ...
Herein, a new polymeric resin for stereolithography (SLA) three-dimensional printing (SLA-3DP) is reported. An ultraviolet (UV) or visible (VIS) light source is critical for SLA printing technology. UV light can be used to manufacture 3D objects in SLA-3DP, but there are significant occupational safety and health issues (particularly for eyes). These issues prevent the widespread use of SLA-3DP at home or in the office. Through the use of VIS light, the safety and health issues can largely be solved, but only non-transparent 3D objects can be manufactured, which prevents the application of 3DP to the production of various common transparent consumer products. For these reasons, we developed a VIS light-curable yet visibly transparent resin for SLA-3DP, which also retains UV curability. The key was to identify the photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (DPTBP). DPTBP was originally designed as a UV photoinitiator, but we found that VIS light irradiation is sufficient to split DPTBP and generate radicals due to its slight VIS light absorption up to 420 nm. The cured resin displays high transparency and beautiful transparent colors by incorporating various dyes; additionally, its mechanical properties are superior to those of commercial resins (Arario 410) and photoinitiators (Irgacure 2959). [Figure not available: see fulltext.]
... Several methods have been proposed to determine the efficacy of the light polymerization of dental resins, such as the use of nuclear magnetic resonance, FTIR, and highperformance liquid chromatography. In the current study, FTIR was used because this method is highly efficient for the molecular detection and assessment of chemical reactions and because this method provides a better interpretation of changes that occur in a polymer matrix (24,25). This method was also used by Solhi et al. (14), Park et al. (26), and Shin et al. (27) for the assessment of the efficacy of the polymerization of bis-GMA composites. ...
Background
Experimental dentin bonding systems containing nanoclay fillers have shown high microleakage, which may be due to the high concentration of hydroxyethylmethacrylate (HEMA) in their composition.
Objectives
This study sought to assess the effect of using different concentrations of HEMA in an experimental dentin bonding system containing PAA-g-nanoclay on the degree of conversion and microleakage of class V composite restorations.
Methods
This in vitro experimental study was conducted on 60 class V cavities prepared in the buccal and/or lingual surfaces of sound-extracted premolar teeth. The cavities were restored using an experimental dentin bonding agent containing PAA-g-nanoclay and a light-cure composite in three groups (n = 20) with a HEMA concentration of 15% (group 1), 20% (group 2), and 30% (group 3) in the adhesive. After thermocycling, microleakage was assessed at the occlusal and gingival margins of the restorations using the dye penetration method. The degree of conversion of the dentin bonding agent was calculated using Fourier transform infrared spectroscopy. The data was analyzed using SPSS version 16 and the Kruskal-Wallis, Fisher’s exact, Wilcoxon, and Mann-Whitney tests (α = 0.05).
Results
Microleakage at the occlusal and gingival margins was not significantly different between the three groups (P > 0.05), but the difference in microleakage between the occlusal and gingival margins was significant within each group (P < 0.001). The three groups were not significantly different in terms of degree of conversion (P > 0.05).
Conclusions
Based on the results, HEMA concentrations of 15%, 20%, and 30% in our experimental bonding agent had no effect on the microleakage of class V restorations. They were not significantly different in terms of degree of conversion either.
... Several methods have been proposed to determine the efficacy of the light polymerization of dental resins, such as the use of nuclear magnetic resonance, FTIR, and highperformance liquid chromatography. In the current study, FTIR was used because this method is highly efficient for the molecular detection and assessment of chemical reactions and because this method provides a better interpretation of changes that occur in a polymer matrix (24,25). ...
... Thus far, an evaluation of the physical and mechanical properties of the adhesives has been considered prior to the adaptation. One solution could be a change in the photoinitiators used in dentin adhesives, which in turn can affect the physical and mechanical aspects in the improvement of clinical performance [11,13,20,21]. ...
This study evaluated the physical and mechanical properties of resin matrices in dental adhesives with two photoinitiator systems. Resin matrix specimens were made with five different kinds of photoinitiators. Neat resin consisted of 60% 2,2-bis[4-2(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (Bis-GMA) and 40% hydroxyethyl methacrylate (HEMA) by weight, along with camphorquinone (CQ, 1 mol %) and additional components (1 mol % each) as follows: Group 1, 2-(dimethylamino)ethyl methacrylate (DMAEMA); Group 2, ethyl-4-(dimethylamino) benzoate (EDMAB); Group 3, diphenyliodonium hexafluorphosphate (DPIHFP); Group 4, DMAEMA+DPIHFP; Group 5, EDMAB+DPIHFP. The degree of conversion (DC), flexural strength, flexural modulus, microhardness, and ultimate tensile strength were tested. The contribution of each photoinitiator to the DC in a selected group was analyzed with contour plots. One-way ANOVA and Tukey tests (p < 0.05) were used for statistical analyses. The DC of Groups 2, 4, and 5 was similar. The flexural strength was similar in all groups, but flexural modulus was significantly different. Group 3 had the lowest values for all physical and mechanical properties. Among all methods, the microhardness test revealed the greatest degree of difference among the five specimens. CQ, EDMAB, and DPIHFP were the most effective photoinitiators and CQ was the most influential factor for the DC rate.
... An important characteristic of PPD is that this sensitizer can improve crosslinking by monomers in the network. The increased crosslinking improves the physicochemical properties of the resultant polymer [4,6,7]. ...
Objectives:
To evaluate the effects of the diphenyliodonium hexafluorophosphate (DPI) on the physical and mechanical properties of solvated dental adhesive resins containing camphorquinone (CQ) and/or 1-phenyl-1,2-propanedione (PPD) as initiators.
Methods:
Model solvated resins containing bisphenol glycidyl methacrylate (BisGMA); triethyleneglycol dimethacrylate (TEGDMA); 1,3-glycerol dimethacrylate (GDMA); 2-hydroxyethyl methacrylate (HEMA); dimethylaminoethyl amine benzoate (EDAB) and ethanol were prepared. The resins were divided in 24 test groups according to the incorporated initiator systems (CQ-0.5 or 1mol%; PPD-0.5 or 1mol%; CQ+PPD-0.5 or 1mol%) as well the presence of DPI (0, 0.5 or 1mol%). Degree of conversion (using Fourier-transformed near infra-red spectroscopy), flexural strength and modulus by three point bending, cohesive strength and water sorption and solubility were measured. Data were statistically analyzed by one and two way ANOVA and Tukey's test (α=0.05).
Results:
DPI increased the degree of conversion of all materials tested. Camphorquinone promoted higher degree of conversion than resins containing only PPD or CQ+PPD. Generally, the resins containing PPD+CQ with DPI presented higher flexural strength and modulus, cohesive strength, as well lower water sorption and solubility.
Significance:
The use of PPD combined with CQ can increase the physical properties of the solvated resins. DPI improved the monomer conversion of all experimental materials and can positively modulate most of the physical properties of the solvated resins.
... Moreover, camphorquinone requires the presence of a photo-reducer (or co-initiator) such as a tertiary amine. Because of these drawbacks, other visible light photo-initiators have emerged such as bis(acyl)phosphine oxides (BAPO) [35][36][37][38][39]. These are classed as Norrish Type-I photo-initiators as they do not need any co-initiator since their homolytic ˛-cleavage is sufficient to produce two radical species both capable of initiating polymerization (Fig. 1) [40][41][42][43][44]. ...
Objective:
This paper investigates the photo-co-polymerization behavior of a blend of a diacrylamide (DEBAAP) with a phosphonylated acidic monomer using either bis(acyl)phosphine oxide or camphorquinone/amine as photo-initiator and studies the effect of variation of the structure of the phosphonylated acidic monomer on the shear bond strength to human dentin.
Methods:
Photopolymerization kinetics has been assessed through the use of photo-DSC with either initiating system and with and without a phosphonic acid monomer, while the shear bond strengths (SBS) of dentin bonding agents formulated with several phosphonylated acidic monomers have been evaluated by macro SBS testing on human dentin.
Results:
Photo-DSC results show that bis(acyl)phosphine oxide initiates a faster polymerization than camphorquinone/amine and that both photopolymerizations are accelerated by the phosphonic acid monomer. Similar results were obtained between adhesives based on camphorquinone/amine and a commercial adhesive (AdheSE, Ivoclar-Vivadent, Schaan, Liechtenstein). The best performances were obtained when BAPO was used as the initiator, in many cases far better than the commercial adhesive. Adhesive SEA6 based on difluoromethylphosphonic acid C demonstrated the best adhesion results of this study. Significance The bis(acyl)phosphine oxide photo-initiator causes faster photopolymerization of two-step self-etching dental adhesive, and its use could yield better bonding performance.
... A prominent initiator is 1-phenyl-1,2-propanedione (PPD) which has an aromatic group on one side of the dicarbonyl and a methyl group on the other ( Fig. 6.4) and l max ª410 nm. Recent experiments showed that PPD would be an efficient visible light photo-sensitiser, comparable with camphorquinone, for the initiation of the dental resin polymerisation [60], and that resins initiated with PPD showed better mechanical properties than those initiated with CQ [61]. Furthermore, PPD can act synergistically with CQ to increase the monomer conversion to polymer and/or reduce the photo-sensitiser concentration (and, hence, colour). ...
Photo-polymerisation is now a widely accepted initiation mode for the clinical hardening processes required with a wide range of biomaterials including dental adhesives and restoratives. As we discuss in detail, there is a strong relationship between the progressive phenomenon of photo-polymerisation, with attendant network formation, and shrinkage stresses and strains set up in the material and its host environment.Molecular densification during the polymerisation process of dental restoratives, and the macroscopic effects of shrinkage strain and/or shrinkage stress, continue to attract widespread international research interest [113]. This is pursued at several levels. There is the need to characterise these properties of both candidate monomer molecules, synthesised with the aim of attaining reduced shrinkage materials [14], and also resin-composite materials-either commercially available or formulated experimentally [10]. In addition, different light-curing units and modes of operation require investigation with representative materials in the context of shrinkage phenomena [3, 15, 16]. These properties are strongly coupled and are controlled especially by the degree of conversion (DC) of the network [3]; thus, there are numerous variables associated with the photo-polymerisation process, and an understanding of these is important for the dentist and the dental scientist.
... Previous studies have demonstrated the polymerization efficiency of TPO and BAPO [7][8][9][10]. These photonitiators require a modification of the existing dental lights to extend the emission profile beyond blue light wavelengths for better curing. ...
Objective:
To establish the relationship between photoinitiator system and nanofiller size on the optical properties and cure efficiency of model composites.
Methods:
Model composites based on BisGMA/TEGDMA (60:40mol%) were loaded with 40wt% of 7nm or 16nm-sized filler particles. One of the following photoinitiator systems was added: camphorquinone (CQ) associated with an amine (EDMAB), monoacylphosphine oxide (TPO), or bysacylphosphine oxide (BAPO). The optical properties of disk-shaped specimens were measured 24h after curing and repeated after storage in water for 90 days and coffee for 15 days. A large spectrum LED unit (Bluephase G2, Ivoclar Vivadent) was used for photoactivation. CIE L*a*b* parameters, color difference (ΔE), and translucency parameter (TP) were calculated. Knoop hardness readings were taken at top and bottom composite surfaces. Cure efficiency was determined by bottom/top hardness ratio. Data were statistically analyzed at α=0.05 significance level.
Results:
Composites formulated with 16nm particles had higher CIE L* than those with 7nm particles in all storage conditions. BAPO-based composites generally had lower CIE a* than the other composites. The group TPO+16nm before storage and all groups with 16nm-sized particles after storage had lower CIE b* (i.e. lower degree of yellowing) than the other groups. TPO-based materials had higher color stability. The cure efficiency was not significantly affected by photoinitiator system or particle size. CQ+7nm had the lowest and BAPO+16nm the highest hardness values.
Significance:
Combination of photoinitiator system and filler particle size might affect the optical properties of composites, with low influence on cure efficiency.
... Sistemas binários formados pelo associação de um fotoiniciador (CQ) e um co-iniciador (amina terciária) são os sistemas de fotoiniciação mais frequentemente utilizados para a polimerização de monômeros metacrilatos, como os adesivos odontológicos. As espécies reativas geradas pela CQ possuem uma curta vida útil, o que a torna inefetiva para desencadear a polimerização quando utilizada isoladamente [23] . Por isso, um eficiente doador de hidrogênio é utilizado, como as aminas terciárias (EDAB) promovendo a estabilização da canforoquinona [11] . ...
This study evaluated the effect of organic solvent concentration on the tensile strength for an experimental adhesive resin containing a ternary photoinitiator system. A monomer blend based on the Bis-GMA, TEGDMA and HEMA was used as a model dental adhesive resin. Two photoinitiation systems were used: a binary system camphorquinone (CQ) and ethyl 4-dimethylamine benzoate (EDAB)] and a ternary system CQ, EDAB and diphenyliodonium hexafluorphosphate (DPIHFP)]. Varied ethanol concentrations were added to the resins, viz. 0, 5, 10, 20, 30, 40 wt%. The ultimate tensile strength test was used to investigate the influence of the solvent amount on the resistance of resins. Furthermore, the use of iodonium salt in photoinitiation system increased the cohesive strength when compared with the binary system. Regardless of solvent concentration, the cohesive strength of polymers containing diphenyliodonium was higher than for the binary photoinitiator system.
... A significant lower photoreactivity of CQ was observed at higher concentrations (Schneider et al., 2008). To address these disadvantages of CQ, alternative photoinitiators such as phenyl propane-dione (PPD) or acrylphosphine dioxides (APO), which absorb light at lower wavelengths than CQ have been studied (Schneider et al., 2008;Schroeder et al., 2008;Sun and Chae, 2000). PPD showed a lower rate of polymerization without affecting the final degree of conversion compared to CQ (Ogunyinka et al., 2007). ...
Camphorquinone (CQ) is by far the most widely used visible-light photoinitiator in biomedical applications. Despite the fact that CQ is well established and has a good clinical acceptance, photoinitiating systems based on CQ have some drawbacks in particular poor water solubility and low photoreactivity. Here the synthesis and testing of a new camphorquinone derivative are described. Carboxylated-camphorquinone (CQCOOH) was synthesized using ketopinic acid as starting material. The chemical structure of CQCOOH was verified by 1H-NMR, 1H-13C-COSY-NMR, FT-IR, mass spectroscopy, and UV-visible spectrophotometry. CQCOOH was used with an amine coinitiator and diphenyliodonium chloride (DPIC) accelerator as visible light induced photoinitiating system for the preparation of hydrogels. CQCOOH exhibits a significant higher photoreactivity compared to CQ with the same amine-DPIC system. Already after 5 seconds exposure time, the polymer crosslinked with the CQCOOH-amine-DPIC system formed a hydrogel. Furthermore, higher crosslink density and better mechanical properties are observed compared to those hydrogels prepared with the CQ-amine-DPIC system. Experiments measuring the activity or integrity of cells (MTT and LDH assay respectively) were performed to investigate the compatibility of the photoinitiating system components with human gingival fibroblast (HGF). According to these experiments neither CQCOOH, L-arginine nor N-phenylglycine as amine coinitiators do have toxic effects even in high concentrations. In contrast, HGF cell viability is considerably decreased at DPIC-concentrations higher than 0.25%.
... CQ is a a-dicarbonyl compound that becomes a reactive species after light absorption. When used alone, the reactive species from CQ can easily recombine, leading to the cage effect due to molecule regeneration [14]. Therefore, polymers formed using CQ have only a low degree of conversion [3], which could explain the low immediate bond strength of CQ group, since the degree of conversion is strongly related to the mechanical properties of the polymer formed [15]. ...
... Especially in dental fillings skin damage can be avoided using visible light as the source (4). For instance, 1,2-diketones, 1-phenyl-1,2-propanedione and 2,3-butanedione are the visible light photosensitizers for dental resin composites (5). ...
Two benzotriazole derivatives, 2-benzyl-4,7-di(thiophen-2-yl)-2H-benzo[d][1,2,3]triazole (BBTS) and 2-benzyl-4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2H-benzo[d] [1,2,3]triazole (BBTES) were employed as photosensitizers for diaryliodonium salt photoinitiators in photoinitiated cationic polymerization of various epoxide and vinyl ether monomers. Diphenyliodonium hexafluorophosphate (Ph2IPF6 ) salt was used as the photoinitiator in this study. Extended conjugation and electron-rich moieties of the photosensitizers enabled the use of long wavelength UV and visible light emitting light sources in cationic photopolymerizations. Having low oxidation potentials and good solubility in cationically polymerizable monomers make them efficient photosensitizers for the diphenyliodonium salt in the photoinitiated cationic polymerization. Polymerizations were achieved at room temperature and monitored by optical pyrometry. Moreover, photopolymerization of a diepoxide monomer with ambient solar irradiation in the presence of BBTES and BBTS were examined.
Applications of photochemistry are becoming very popular in modern‐day life due to its operational simplicity, environmentally friendly and economically sustainable nature in comparison to thermochemistry. In particular photoinduced radical polymerisation (PRP) reactions are finding more biological applications and especially in the areas of dental restoration processes, tissue engineering and artificial bone generation. A type‐II photoinitiator and co‐initiator‐promoted PRP turned out to be a cost‐effective protocol, and herein we report the design and synthesis of a new efficient co‐initiator for a PRP reaction via a barrierless sequential conjugate addition reaction. Experimental mechanistic observations have been further complemented by computational data. Time for newly synthesised 1,2‐benzenedithiol (DTH) based co‐initiator promoted polymerisation of urethane dimethacrylate (UDMA, 70 %) and triethylene glycol dimethacrylate (TEGDMA, 30 %) in presence of 450 nm LED (15 W) under the aerobic conditions is 38 seconds. Polymeric material has high glass transition temperature, improved mechanical strength (860 BHN) and longer in‐depth polymerisation (3 cm).
During the past decades, visible light photoinitiators have been extensively studied due to the development of cheap and energy-saving irradiation sources, namely light-emitting diodes (LEDs). With aim at developing chromophores with absorption perfectly fitting the emission of LEDs, triphenylamine has been identified as a versatile building block for designing Type I and Type II photoinitiators of polymerization. In this review, an overview of different photoinitiators comprising a triphenylamine unit is presented. To evidence the interest of these structures, comparisons with benchmark photoinitiators is presented.
Composites in Biomedical Applications presents a comprehensive overview on recent developments in composites and their use in biomedical applications. It features cutting-edge developments to encourage further advances in the field of composite research.
Highlights a completely new research theme in polymer-based composite materials
Outlines a broad range of different research fields, including polymer and natural fiber reinforcement used in the development of composites for biomedical applications
Discusses advanced techniques for the development of composites and biopolymer-based composites
Covers fatigue behavior, conceptual design in ergonomics design application, tissue regeneration or replacement, and skeletal bone repair of polymer composites
Details the latest developments in synthesis, preparation, characterization, material evaluation, and future challenges of composite applications in the biomedical field
This book is a comprehensive resource for advanced students and scientists pursuing research in the broad fields of composite materials, polymers, organic or inorganic hybrid materials, and nano-assembly.
Finding novel photoinitiators with photobleaching properties suitable for long-wavelength LED light sources is important for their potential use in the photocuring ceramic suspensions containing acrylate resin. Two D-π-A-π-D conjugated benzylidene ketones with visible light absorption (TPAK and CZK) were synthesized and evaluated as photoinitiators in the photocuring of acrylate resin and ceramic suspension under blue (460 nm)/green (520 nm) LED sources. Results showed that the two photoinitiators have high photoinitiating activity and can effectively produce thick-layer curing in acrylate resin and ceramic suspension due to their quick photobleaching properties under 460 nm and 520 nm LED light sources. The curing depth of the ceramic suspensions was measured as a function of the concentration of TPAK and CZK and the energy level of the LED light source. Jacob's equation was used to determine the critical energy Ec and depth sensitivity Dp of every suspension with different concentrations of benzylidene ketones.
Amaç: Bu çalışmanın amacı farklı ışık kaynakları ile farklı kalınlıkta polimerize
edilmiş ve yapay yaşlandırma işlemine maruz bırakılmış 5 farklı bulk-fill kompozit rezinden (Filtek Bulk Fill Flowable, Sonic Fill 2, Surefil SDR Flow, Venus Bulk Fill, Tetric N-Ceram Bulk Fill) ve 1 adet konvansiyonel kompozit rezinden (Filtek Z250) açığa çıkan monomer miktarının incelenmesi ve elde edilen monomerlerin kompozit materyaller arasında karşılaştırılmasıdır. Materyal ve Metot: LED (Light Emitting Diode) ya da QTH (Quartz Tungsten
Halogen) ışık cihazı kullanılarak 5 mm çapında hem 2 mm hem de 4 mm kalınlıkta kompozit diskler hazırlandı. Üretilen kompozit örnekler %75 etanol/su solüsyonu içeren cam viyallere aktarıldı ve sonra cam viyaller iki gruba ayrıldı. Kontrol grubunda olan cam viyaller üç farklı zaman diliminde (0-1 gün, 1-3 gün ve 3-7 gün) 37 0C'de etüvde bekletildi. Termal siklus grubunda bulunan örnekler kontrol grubunda belirlenen üç zaman dilimine denk gelecek süre kadar termal siklusa maruz bırakıldı (0-1 gün: 1500; 1-3 gün: 3000; 3-7 gün: 6000). Her bir zaman diliminde alınan ekstraksiyon örneklerindeki monomerler HPLC cihazında ölçüldü. Elde edilen veriler tekrarlanan ölçümlü varyans analizi ve tukey çoklu karşılaştırma testi (p<0,05) ile analiz edildi. Bulgular: Bis-GMA, TEGDMA, UDMA ve Bis-EMA monomerleri sırasıyla
Tetric N Ceram Bulk Fill, Sonic Fill 2, SDR ve Venus Bulk Fill kompozitlerinden en fazla miktarda açığa çıktı. 1. gün en yüksek seviyede monomer elüsyona uğrarken, zamanla monomer elüsyonunun azaldığı tespit edildi. Termal siklus uygulaması artık monomer elüsyonunu artırdı ve bazı zaman periyotlarında monomerlerin sitotoksik düzeye ulaştığı belirlendi. İlk 24 saat hariç ışık kaynakları arasında anlamlı bir farklılık görülmedi. Artan kalınlıkla birlikte açığa çıkan Bis-GMA, TEGDMA, Bis-EMA monomer miktarındaki en fazla artış Sonic Fill 2 kompozitte, UDMA monomer miktarındaki en fazla artış ise Filtek Z250 kompozitinde tespit edildi. Sonuç: Monomer elüsyonunun büyük bir kısmı ilk 24 saatte gerçekleşti ve
zamanla açığa çıkan monomer miktarı azaldı. Kompozit örneklerin kalınlığı 2 mm’den 4 mm’ye çıkartıldığı zaman açığa çıkan monomer miktarının oranı kullanılan kompozite göre değişkenlik gösterdi. Termal siklus işleminden sonra elde edilen monomer miktarı kompozit materyalin kalınlığı ve yapısına bağlıydı. Farklı ışık kaynakları kompozitlerden açığa çıkan monomer miktarını genellikle etkilemedi.
Anahtar Kelimeler: Artık monomer, Bulk-fill kompozit, HPLC, Termal siklus
Statement of problem
The color stability and mechanical properties of luting agents influence the esthetics and longevity of ceramic restorations. However, studies evaluating the color changes and mechanical properties of luting agents under ceramic laminates activated by using different methods are lacking.
Purpose
The purpose of this in vitro study was to evaluate the effects of different modes of photoactivation on the nanohardness and elastic modulus of resin cements and dental adhesives and on the color stability of ceramic laminate veneers.
Material and methods
Forty-four lithium disilicate blocks (7×8×0.6 mm) were cemented onto bovine enamel and divided into 4 groups according to the polymerization light (Radii-Cal or Valo) used and the mode of activation of the dental adhesive (no previous photoactivation or previous photoactivation). Single Bond Universal dental adhesive and RelyX Veneer resin cement were used in all experimental groups. Color stability was measured using a UV-2450 ultraviolet-visible spectrophotometer before and after ultraviolet-B artificial accelerated aging (n=8). The nanohardness and the elastic modulus of the adhesive and resin cement were measured using a nanohardness tester (n=3). The color stability and mechanical properties were measured and analyzed using ANOVA and the Tukey least significant difference test (α=.05).
Results
No difference in color stability or mechanical properties of the resin cement among the polymerization lights was detected (P>.05). Specimens that underwent previous photoactivation of the adhesive using the Valo polywave unit exhibited higher elastic modulus values than those that did not undergo previous photoactivation (P<.001).
Conclusions
The Valo polywave polymerization light improved mechanical properties and color stability more than the Radii-Cal unit. Previous activation of the dental adhesive in the dental enamel with the Valo polywave polymerization light yielded more satisfactory results.
This chapter describes photochemical processes of polymers including photopolymerization and photocrosslinkable polymerization. Photoinitiators are key components in photopolymerization that generate reactive species of free radicals or ions via Norrish type I or Norrish type II reactions. Visible-light photoinitiators are fascinating compounds, because visible-light curing is a challenging issue due to high demands in diverse applications such as dental restoration, reprography, and three-dimensional printing. Photo-iniferters are also attractive photoinitiators that yield high-reactive free radicals, leading to a living radical polymerization with narrow polydispersity. Photoreactive polymers including the photoinitiators have functional properties for biological applications, for example, the photo-induced micropatterned surfaces in synthetic polymers for immobilization of cells, and photo-cross-linking in biopolymers for tissue engineering. We also describe photolabile compounds, photodegradation of chemical structures, for development of a mild chemical approach for dealing with sensitive biomolecules against acids and bases.
Objectives:
This is a confirmatory study to evaluate the effect of photoinitiator type and concentration, matrix monomer chemical structure, and nanoparticle incorporation on the physical and mechanical properties of an experimental dentin bonding agent.
Materials and methods:
Different concentrations of camphorquinone-amine (CQ-A) system, butanedione (BD), and phenylpropanedione (PPD), as photoinitiator, BTDMA, as a comonomer containing carboxylic acid groups, and silica nanoparticles as reinforcing inorganic filler were incorporated into a methacrylate base experimental dental adhesive. The effect of these ingredients, as independent variables, on the shrinkage kinetics, flexural strength and modulus, and microshear bond strength of the adhesives were then investigated. The results were analyzed using one-way ANOVA and Tukey's post-hoc test at the significance level of 0.05.
Results:
The results indicate that the efficiency of CQ-A initiator system is diminished in the presence of the acidic monomer BTDMA while the photopolymerization is efficiently progressed with BD as initiator. PPD shows the lowest efficiency in the photopolymerization of the adhesives. BTDMA as a monomer with the capability of interaction with tooth structure provides adhesive with improved microshear bond strength to dentin. Incorporation of silica nanoparticles at low concentrations enhances the flexural and microshear strength of the dentin bonding agent.
Significance:
Understanding the structure-property relationship in dental adhesives may help the material selection in clinical dentistry. The study elucidates the relationship between monomer structure, initiator type, and nanofiller and physical and mechanical properties in dental adhesives.
1,2-Diketones, camphorquinone and 1-phenyl-1,2-propanedione, are converted to the corresponding α-hydroxyketones in moderate to good yields by TiO2-catalyzed photochemical reactions in deoxygenated alcoholic media. The reduction yield for 1-phenyl-1,2-propanedione is considerably increased by addition of water or triethylamine.
Purpose: The purpose of this study was to know the availability of two photosensitizers, PD, DA, as a photosensitizer instead of CQ in UDMA dental composite resin. We want to know photopolymerization effect of UDMA unfilled resin and surface hardness of composite resin containing PD and DA were compared with those of CQ, most widely used photosensitizer for dental composite resins. Methods: The photopolymerization effect of UDMA studied by FT-IR spectroscopy increased with irradiation time and the amount of photosensitizer. Knoop hardness of experimental composite resins prepared by the addition of the photosensitizer content and irradiation time. Results: The relative photopolymerization effect of UDMA increased in the order of PD > CQ > DA. The composite resin of UDMA containing DA or PD, which shows better Knoop hardness than that containing CQ. Conclusion: PD and DA show as effective photosensizers, suitable for UDMA dental composite resin compare with a higher efficiency than CQ.
In our study we aimed to identify the individual influence of the main components of wine on the studied composites. The samples were immersed in water, wine, alcohol, tartaric acid solution, at 370C. We measured the reflectance of the surfaces of the composite materials with UNICAM 4 UV-VIS spectrophotometer after 24 h, 7 days and 28 days. The t test results for delta %(xnm)ts of the dental composite material at the same moment in time and different solutions (within the group test) identified a single group which revealed no statistical significant difference. The studied materials at the same moment in time (between group tests) will respond statistically different to the immersing solution. We expect that the changes in the composition of composite materials, including activation systems, inorganic fillers, resin matrix, silane will change the response of the composite materials to the immersion solutions.
The violet laser diode was developed in 1996, and is now widely used as a light source for high-speed multilayer recording systems such as Blu-ray discs and HD-DVD systems. These lasers also show promise for medical applications, such as cutting soft tissue, laser acupuncture, tooth whitening, and detection of dental caries. The wavelength of the violet laser diode (approx. 405nm) may be suitable for hardening light-cured dental materials combined with some alternative photo-initiators. This article examines the light-curing efficiency of some commercial and three experimental dental resins by GaN-based violet laser diode determined in terms of ultimate micro-tensile strength, in comparison with curing by various commercial LED light-curing units. The spectral characteristics of the transmittance of contemporary dental adhesives and the emission of several commercially available light-curing units are also presented. The results revealed that violet laser diodes can be used as a light-curing source to initiate the polymerization of light-cured dental resins.
Purpose: The purpose of this study was to know the availability of three photosensitizers, CQ, PD, DA, as a photosensitizer of dental resin composite. We want to know abortion band around visible light region for the using potential possibility as a photosensitizer for visible light cured dental composite resin. And I studied to know the relative photodecomposition ratio of three photosensitizers with or without photoinitiator, DAEM. Methods: The photodecomposition of three photosensitizers were studied by UV absorption spectroscopy in ethanol and determined by same instrument with irradiation time for relative photodecomposition. In order to study the effect of amine on photodecomposition was added the DAEM in the photosensitizer solution and the relative rate was measured by the same procedure with aove mentioned. Results: The all of three photosensitizers are absorbed around visible light region. The relative rate of decrease in absorbance incereased in the order: CQ < BD < PD. The effect of DAEM on the photodecomposition of the photosensitizers was appeared different results without DAEM. The photodecomposition rate of PD and DA decreased somewhat with the addition of amine, while that of CQ increased. The rtealtive photodecomposition rate increased in the oprder: BD CQ < PD with the addition of amine, but the differnce was not significant. Conclusion: PD and DA like CQ gives to the possibility of use as a photosensitizer for visible light cured dental composite resin by absorption around visible light region and photodecomposition in the maximum absorption wavelength. And it is showed that PD and DA are not effective decomposed with amine initiator, DAEM but CQ decomposed with DAEM effectively. This result may be due to a different mechanism operating for the decomposition of photosensitizers in the presence of amine.
Purpose: The purpose of this study was to know the physical properties of UDMA dental composite resins containing two photosensitizers, PD, DA, as a photosensitizer instead of CQ. We want to know Remaining Double Bond(RDB) of UDMA unfilled resin and diametral tensile strength and flexural strength of composite resin containing PD and DA were compared with those of CQ, most widely used photosensitizer for dental composite resins. Methods: The RDB of UDMA studied by FT-IR spectroscopy increased with irradiation time. The composite resins were tested for their physical properties. The dental composite resins were made with UDMA as a monomer, silanized silica as filler, N,N-dimethylaminoethyl methacrylate (DAEM) as amine initiator, and one of the two kinds of new photosensitizers. Results: The relative RDB of UDMA was in the order: DA > CQ > PD but the physical properties of the composite resins show PD and DA with higher results compared with that containing CQ. The reason for the results is that PD and DA serve not only as a photosensitizer but also as a photo-crosslinking agent. Conclusion: PD and DA show as effective photosensizers, suitable for UDMA dental composite resin compare with a higher efficiency than CQ.
Photocurable systems, which offer advantages such as microfabrication and in situ fabrication, have been widely used as dental restorative materials. Because the visible light-curable (VLC) system causes no biological damage, it is popular as a dental material and is being investigated by many researchers for other medical applications. Here, the principle of the VLC system is explained and recent progress in key components including photoinitiators, monomers, macromers, and prepolymers is discussed. Finally, biomedical applications for drug delivery and soft tissue engineering are reviewed. Considering the recent development of VLC systems, its importance in the field of medical applications is expected to continue to increase in the future.
Two novel aliphatic amine-containing dimethacrylate monomers were synthesized from the ringopening reaction of hexamethylene
diamine and ethylenediamine with glycidyl methacrylate. The UV-curable and heat-curable formulations were prepared with amine-containing
dimethacrylate and active diluents. The curing process was controlled by Fourier transform infrared analysis. The mechanical,
physical, and thermal characterizations of the UV-cured films and the UV-heat-cured films were investigated. Thermo-gravimetric
analysis of the cured films revealed that the thermo-oxidative stability of the UV-heat-cured films was higher than that of
the UV-cured samples. An increase in the cross-linker content caused an increase both in tensile strength and in the elongation
values of the UV-heat-cured films. It was also found that the water absorption capacities and gel content of the UV-heat-cured
dimethacrylated films depended on the amount of the active diluents.
The purpose of this article is to review the fundamentals of photocuring with various types of lamps in orthodontics. Information on the characteristics of lamps, photopolymerization, from the perspective of both the material composite resin adhesive and source (lamp) are discussed, with reference to light scattering, optimum filler size, extent of polymerization, and the degree of cure of resins irradiated with different lamps. This discussion is followed by a review of the clinically useful listing of properties of lamps and their application to orthodontic bonding as these are reflected in 4 key properties of the material, such as polymerization efficiency (degree of cure), mechanical properties (bond strength), clinical performance (failure rate), and biological properties of blue light.
A new α-diketoporphyrin and the corresponding Pd complex were prepared from the monoanthroporphyins and their photochemical properties were investigated by measurements of absorption and emission spectra, fluorescence lifetimes, laser flash photolysis, cyclic voltammetry, and theoretical calculations. Intramolecular electron transfer from the porphyrin singlet excited state to the diketone moiety was observed for the free base α-diketoporphyrin in benzonitrile, but this was not observed in toluene. Photoreactivity of the α-diketoporphyrins was also examined by irradiation at the Soret and Q bands. When the Soret band of the freebase α-diketoporphyrin was irradiated, cleavage of the diketone moiety occurred to afford the monoanthroporphyrin with the release of two CO molecules quantitatively in both benzonitrile and toluene. When the Q band of the freebase α-diketoporphyrin was irradiated, no photocleavage reaction occurred in toluene. In contrast to the freebase α-diketoporphyrin, the photocleavage reaction of the Pd complex occurred with irradiation at the Q band as well as the Soret band to afford the monoanthroporphyrin quantitatively in toluene. The photocleavage reaction proceeded much more effectively in toluene than in benzonitrile. The occurrence of rapid photoinduced electron transfer from the singlet excited state porphyrin to the diketone moiety, which was detected by femtosecond laser flash photolysis measurements, results in a significant decrease in the singlet excited state lifetime, prohibiting the photocleavage reaction in benzonitrile. Thus, the Pd α-diketoporphyrin can act as an excellent precursor for the corresponding acene in toluene. The photocleavage process provides a convenient and inexpensive method to make the thin film.
A polymeric photobase generator containing oxime–urethane groups was prepared by copolymerization of methyl methacrylate and methacryloxyethyl benzophenoneoxime urethane, and its photo and thermal crosslinking reaction after irradiation was examined from the measurement of UV and IR absorption spectral changes, insoluble fraction, and molecular weight changes. The photo-crosslinking reaction of the copolymer film was more efficient when irradiations were carried out with 310 nm UV light in the presence of benzophenone than with 254 nm UV light without the addition of benzophenone. The crosslinking reaction increased after postexposure baking (PEB), and this thermal crosslinking reaction mechanism was studied from the identification of the photolysis products of a model compound, benzophenoneoxime phenylurethane, by a high-performance liquid chromatography. The results indicate that the thermal crosslinking reaction of the copolymer after PEB is due to the formation of urea-type chemical bonds. Resist properties of the copolymer were examined from the measurement of normalized thickness and micropattern development. A negative tone image with a resolution of 2 μm was obtained with this copolymer, having a sensitivity (D) of 1200 mJ/cm2 and contrast (γn) of 1.31, when irradiation was carried out with 310 nm UV light in the presence of benzophenone following chloroform development. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 975–984, 2004
Objectives:
The aim of this study was to evaluate the thermal and mechanical properties of the composite resins containing the photo-initiators camphorquinone (CQ) and/or phenyl-propanodione (PPD) when photoactivated with halogen lamp (XL2500/3M-ESPE), monowave (UltraBlueIS/DMC) and polywave (UltraLume5/Ultradent) LED units.
Materials and methods:
A blend of BisGMA, UDMA, BisEMA and TEGDMA was prepared with the same wt% of photo-initiators CQ and/or PPD and 65wt% of silaneted filler particles. Compression strength (CS), diametral tensile strength (DTS) and diametral modulus (DM) were tested. Thermogravimetric analysis (TGA) was made and the lost residual monomer were verified. Dynamic mechanical thermal analysis (DMTA) was used for to analyze the glass transition temperature (Tg) and the storage modulus in 37°C. Degree of conversion (DC) was accomplished in the same samples of DMA using middle-infrared spectroscopy (mid-IR).
Results:
CQ, CQ/PPD and PPD obtained the same results for all mechanical properties (CS, DTS and DM), lost residual monomer and storage modulus in 37°C, regardless LCU used. The results of Tg showed that the combination PPD-UltraLume5 produced the highest values. DC showed that the combination CQ-UltraLume5 resulted in the highest values and PPD-XL2500 in the lowest DC values.
Conclusion:
The study shows that PPD is not only effective photosensitizers, but also photocrosslinking agents for dental composite resins with a similar efficiency to CQ.
Objectives:
This study evaluates the effect of incorporation of an acrylate polyhedral oligomeric silsesquioxane nanostructure (APOSS) on the physical and mechanical properties and hydrolytic stability of octyl cyanoacrylate (CA) adhesives.
Materials and methods:
CA was photopolymerized under irradiation of visible light using 1-phenyle-1,2-propandione (PPD), and 2,3-botanedione (BD) as photoinitiators. Following the polymerization shrinkage kinetics of the adhesives, the initiator concentration was optimized. Mechanical properties of the bulk CA-APOSS nanocomposites, including flexural strength and modulus, were investigated. Miroshear bond strength of dental composite bonded to human dentin applying the CA-APOSS adhesives was also determined. The effect of APOSS on the stability of CA adhesive against hydrolysis studied performing solubility, water uptake, and aging tests.
Results:
The results revealed higher efficiency of BD in comparison to PPD. A 3% (mol/mol) of BD was obtained as the optimum photoinitiator concentration. The incorporation of APOSS increased the polymerization shrinkage rate of the CA adhesives. The flexural strength of CA adhesive was significantly improved incorporating less than 20 wt.% APOSS while an increasing trend was observed in the flexural modulus with the nanostructures loading. The microshear bond strength to dentin was also enhanced using 10 wt.% APOSS as reinforcing/crosslinking nanofillers. A decrease in the solubility and water sorption was the result of incorporation of APOSS in CA adhesives. Degradation due to the hydrolysis in water was diminished in the specimens containing APOSS nanostructures, revealed after aging in water at 37°C.
Significance:
CA adhesives are good soft tissue adhesives which their low mechanical properties and lack of hydrolytic stability has made them less interesting in the applications deal with hard tissues. The study shows that the incorporation of POSS nanostructures into CA could reduce the drawbacks.
Triethyleneglycol acrylate methacrylate (A-M) was prepared by reaction of triethyleneglycol with methacryloyl chloride and then with acryloyl chloride, to create a new monomer with both excellent photopolymerization ability and mechanical properties of the wet photocured polymer. The visible light polymerization ability of A-M was compared with the corresponding dimethacrylate (M-M), the diacrylate (A-A) having a triethyleneglycol chain, and an equimolar mixture of M-M and A-A with attention to the amounts of residual monomers and pendant C=C double bonds in the polymers. The polymerization rate of A-M was the lowest. When irradiation was extended, the amount of residual A-M became comparable to M-M and the concentration of pendant C=C double bonds in poly (A-M) became lower than that in poly (M-M). The polymerization rate of A-A was faster than that of M-M in homophotopolymerization. M-M was incorporated into polymer chain preferentially in the equimolar mixture of M-M and A-A and the concentration of A-A became higher in residual monomers.
A method is reported for the surface grafting of polyvinyl acetate (PVAc) onto modified, nonporous silica. The silica surface was modified by silylation with vinyl(triethoxy) silane followed by graft polymerization of vinyl acetate. The graft yield was measured by thermogravimetric analysis and the monomer conversion was monitored by UV spectral analysis. The rate of the graft polymerization and the graft yield were proportional to the initial monomer concentration. Vinyl acetate conversion followed first-order kinetics and displayed a trend of increasing initial rate with increasing monomer concentration.
The present study investigated whether propanol, a monofunctional aldehyde, was able to improve the mechanical properties of dental polymers. The underlying hypothesis was that a cross-linking reaction is possible between various functional groups of different polymers. Propanol was added to monomer mixtures, which were then made light-curing and loaded with filler. The monomer mixtures were varied with respect to monomer composition and content of aldehyde. Four mechanical properties of the experimental resin composites were determined. Addition of propanol gave rise to significant improvements in mechanical properties, which may be indicative of a cross-linking ability of monofunctional aldehydes. With the exception of modulus of elasticity, the mechanical properties of resin composites based on UEDMA/HEMA were superior to those of BISGMA/TEGDMA-based materials, even though the improvements in flexural strength and modulus of resilience were most pronounced for the BISGMA/TEGDMA-based resin composites.
The present study investigated a concept for additional cross-linking of dental polymers, by which resistance to wear of resin composites might be increased. Bifunctional ketones were added to monomer mixtures, which were then made light-curing and loaded with filler. The monomer mixtures were varied with respect to type and ratio of monomer and ketone. For measurement of possible effects of the cross-linking agents added, four mechanical properties of the experimental resin composites were determined. Addition of the bifunctional ketone diacetyl resulted in the following increases in mechanical properties: diametral tensile strength, 11%; flexural strength, 29%; modulus of elasticity, 19%; and modulus of resilience, 50%.
The visible-light (VL) polymerizing resin system with photoinitiators (photosensitizer and reducing agent) is widely used in modern dentistry. In this system, polymerization is initiated by photochemical reactions between the photosensitizers (aromatic or aliphatic ketones) and reducing agents (tertiary amines) during VL irradiation.
In order to simulate the VL resin-induced toxicity in dental pulps, the present investigation was conducted to determine whether hemolysis of dog erythrocytes and lipid peroxidation of their components occur on exposure to a VL resin system containing aromatic (9-fluorenone, benzil) or aliphatic ketones (camphoroquinone) plus tertiary amine [2-(dimethylamino) ethyl methacrylate].
It was demonstrated that the hemolysis and lipid peroxidation with aromatic ketones were markedly higher than with those of aliphatic ketones, even when the latter were used at higher concentrations. It was clear that peroxidation-induced hemolysis occurred and, further, that surface-active complexes between photosensitizers and reducing agents, which are formed by irradiation, promote hemolytic activity due to their hydrophobic interactions. VL resin-induced responses to dental pulps are probably promoted due to the double effects of unpolymerized monomers and of both radicals and surface-active complexes formed during irradiation.
The present study determined the effect of diacetyl addition on the quantity of remaining double bonds of dental resins. Diacetyl was added to monomer mixtures, which were then made light-curing. The monomer mixtures were varied with respect to monomer composition and content of diacetyl. The quantity of remaining double bonds was determined by means of transmission infrared spectra of the resins recorded before and after wet or dry storage for one wk. Addition of diacetyl resulted in a decrease in the quantity of remaining double bonds by as much as 78% as compared with the mixtures without diacetyl. Negative correlations of statistical significance were found between content of diacetyl and quantity of remaining double bonds in BISGMA: TEGDMA-based as well as in UEDMA: HEMA-based resins for both modes of storage. Significant negative correlations were found between quantity of remaining double bonds and the previously determined mechanical properties.
To optimize the improvements by diketones of the mechanical properties of resin composites, diacetyl was added to two different monomer mixtures in different quantities. There was a positive correlation between content of diacetyl and tensile strength, flexural strength, and modulus of elasticity, respectively, of both the BISGMA/TEGDMA- and the UEDMA/ HEMA-based materials. Addition of diacetyl did not influence the modulus of resilience significantly. Addition of diacetyl resulted in increases in mechanical properties which were of the same relative size for BISGMA/TEGDMA-based materials as for UEDMA/HEMA-based materials. However, because of higher control values, except for modulus of elasticity, the properties of UEDMA/HEMA-based composites were superior to those of the BIGSMA/ TEGDMA-based materials. A content of approximately 24 mole% diacetyl seemed to have optimum effect on mechanical properties, giving a mean increase of 25% in tensile strength, flexural strength, and modulus of elasticity. □ Dental materials; diketones; mechanical properties; resin composites
Polymer networks applied in clinical dentistry can be divided into two groups: (i) hard, solid two-and threedimensional crosslinked structures formed during photo-curing of dental polymeric filling compositions, and (ii) soft, hydrogel-type of networks based on polymeric ionic complexes, used for the tightening of microchannels in teeth.
The first group is based on crosslinked di- and trifunctional monomers, and on solid poly(acrylic acid) - inorganic glasses (“glass - ionomer cements”) This group has found wide clinical applications, in spite of many disadvantages such as susceptibility towards hydrolytic, mechanical. bio- and enzymatic degradations, and contents of toxic, allergenic and mutagenic components.
The second group, the soft-hydrogel type of networks, has been investigated and developed at our institute in order to tighten channels in teeth. The microchannels, with a diameter of 30–200Å in enamel and 1–3 μm in dentine, are filled with a loose, native bio-hydrogel of protein origin. Hydrogels have the ability to swell in water of biological fluids present in the oral cavity, and can retain a significant fraction of fluid within the structure. Decreasing pH below 5.5 causes a slow dissolution of the hydroxyapatite crystals in the walls of the microchannels with a consequent widening of their lumens. Metabolites and toxins from microorganisms, which are always present in the oral cavity, can penetrate into these enlarged channels and cause inflammatory reactions in the underlying pulp tissue. In order to decrease fluid flow and inhibit penetration of microorganisms, but still allow diffusion of ions and water, we have developed and tested polymeric hydrogels based on poly(acrylic acid) and metal salts, and chitosan, which can be formed directly in the micro-channels of dental hard tissues.
The synthesis of bisphenol A–glycidyl methacrylate (BIS–GMA), the resin component in most dental composite restorative materials, catalyzed by different tertiary amine accelerators such as N,N′-dimethyl-p-toluidine (DMPT), N,N′-dimethylamino phenethyl alcohol (DMAPEA), and N,N′-dimethylamino ethyl methacrylate (DMAEMA) is reported in this work. The effect of varying concentrations of accelerators and the reaction conditions of the synthesis as a function of time is studied in detail. The kinetics of the reaction between epoxide and carboxyl group during the formation of BIS–GMA is monitored using infrared (IR) and chemical techniques. The reaction is found to follow first-order and zero-order kinetics with respect to epoxide and acid, respectively. The degree of epoxide and acid conversion has been calculated as a function of time. The percentages of various isomers, formed under different reaction conditions have been reported. Characterization procedures for BIS–GMA have been developed.
Composite restorative material has undergone gradual change in composition since its introduction in the 1960's. Early commercial resins were mixtures of BIS-GMA and TEGDMA. Today, these mixtures are still present, but urethane dimethacrylates and large oligomeric structures of BIS-GMA-urethanes exist. Because of these changes in composition, the past methods of calculating monomer conversion by means of infrared spectroscopy may need modification. This research investigates different methods used to formulate calibration curves for determination of monomer conversion by infrared spectroscopy of contemporary commercial composites containing aromatic structures. Conversion calibration procedures using various baseline methods with BIS-GMA, Bisphenol-A/TEGDMA, and a hydrogenated bonding resin were established. Both peak and area infrared absorptions were determined. One particular baseline method proved the best fit to the Beer-Lambert law. Bisphenol-A was found unsuitable as an infrared calibration model for resin composites. The BIS-GMA/TEGDMA calibration model closely simulates conversion values obtained when a hydrogenated commercial resin model was used.
The objective of this study was to investigate whether water storage causes permanent damage to composites by determining how the tensile strength of nine different composite materials changes with both water storage and water storage followed by dehydration. Eighteen samples (ASTM-D Specification 1708-66) of each of the nine materials were prepared and divided into three groups of six samples each. Group I was stored dry at 60 degrees C, while Groups II and III were stored in distilled water at 60 degrees C. After six months, Groups I and II were subjected to tensile testing, while Group III was transferred to a desiccator and dehydrated for two weeks at 60 degrees C before this group was tested in tension. Mean values, pooled by storage group independent of material, revealed a significant (p less than 0.05) reduction in strength for both Groups II and III relative to Group I. These findings prove that water has an irreversible effect on most dental composites. A comparison of Group II with Group III data revealed that the samples which were aged in water and tested (Group II) were significantly (p less than 0.05) weaker than the dehydrated samples (Group III). However, some products within Group III did not show any tendency to recover their strength after dehydration.
The purpose of this investigation was to determine the composition, as well as the conversion after polymerization, of some dental composite materials. Eight posterior composites and two anterior composites were investigated. The weight and volume fractions of inorganic fillers were determined by combustion and pycnometric analyses. The monomers were analyzed qualitatively and quantitatively by high performance liquid chromatography, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Infrared multiple internal reflection spectroscopy was applied for determination of conversion of the methacrylate groups. The conversion in light activated materials was examined at shallow depths, that is, the level of optimal conversion. This investigation demonstrated that the conversion can be correlated with the composition of monomers and oligomers used in the materials.
The purpose of this study was to develop a methodology whereby the monomer conversion of dental restorative resins which contain no functional group acting as an internal standard can be easily determined using infrared spectroscopy.
Calibration solutions of MMA were made from which the quantification of weight percent methacrylate groups (CH2 = C(CH3)C = O) (termed WPMG) could be determined using infrared spectroscopy. The extent of resin cure using the WPMG method consisted of calculating the changes in WPMG pre- and post-cure. The extent of cure of a commercial unfilled bonding resin was calculated using infrared methods utilizing the internal aromatic standard, and also by means of WPMG.
WPMG had an identical optical constant for a wide range of monomers: MMA, TEGDMA, EGDMA, HEMA: The extent of monomer conversion using both methods of analysis indicated statistically equivalent results: 75.2 +/- 1.0% using an internal standard, and 76.0 +/- 1.1% using WPMG.
The methods developed in this study using infrared spectroscopic methods facilitate the determination of cure of dental resins which do not have functional groups to serve as internal standards.
To choose the most suitable composite for the clinical challenge, the clinician must consider a number of issues. This paper examines those issues, as well as how the selected material can best be manipulated to obtain optimum results. It is intended to help the clinician select this material, and to provide information on the clinical relevance of the different compositions and filler sizes of composite materials, proper techniques for light curing--including the effects of light to resin distance and light angulation--and methods that can be used to evaluate the effectiveness of the light-curing unit. The effect of surface finish on wear is also discussed, along with suggestions on proper finishing techniques.
Previous studies have examined the relationship between total filler content in hybrid restorative composites and some of their mechanical properties. This investigation evaluated the effect of varying the amount of microfiller in an experimental hybrid composite on fracture toughness (single edge-notch technique) and diametral tensile strength. The microfiller content in the experimental hybrid composite was varied from 0-44 wt% for seven specimen groups, while the total filler content ranged from 77-84 wt%. It was found that 9 wt% microfiller loading produced the highest mean fracture toughness (1.33 MPa.m(1/2)) and 44 wt% loading produced the lowest mean value (0.80 MPa.m(1/2)). Only the 9 wt% microfiller content group differed significantly in fracture toughness from the other specimen groups. The diametral tensile strength displayed only small differences for the range of microfiller content studied with mean values ranging from 42.1-49.6 MPa. Additional research on the viscoelastic properties of these heavily filled hybrid composites may provide some insight into the differences for the fracture toughness and diametral tensile strength results.
The aim of the present study was to determine the effect of propanal and diacetyl addition on the quantity of remaining double bonds of chemically cured dental resins. Propanal (propionaldehyde) or diacetyl (2,3-butanedione) was added to monomer mixtures, which were then made chemically curable. The monomer mixtures were varied with respect to content of propanal or diacetyl. Addition of propanal or diacetyl to chemically curable resins resulted in a decrease in the quantity of remaining double bonds from 19.6% to 1.9% and from 19.6% to 11.4%, respectively. A negative correlation of statistical significance was found between content of propanal and quantity of remaining double bonds, while the relationship between content of diacetyl and quantity of remaining double bonds was found not to be linear. Propanal was equally effective in reducing the quantity of remaining double bonds in chemically cured and in the light cured resins studied previously. As regards diacetyl, a more pronounced effect on quantity of remaining double bonds was noted for light cured resins as compared with chemically cured resins. The most likely common reaction mechanism of propanal and diacetyl seemed to be that of chain transfer reactions. Furthermore, analysis of the data indicated a possible additional photoinitiating function of diacetyl.
This study was conducted to determine the effect of diacetyl or propanal activities: 1) on the in vitro wear of 22 experimental resin composites; and 2) on the Wallace indentation hardness of the unfilled resins. The objective was to examine the correlation between wear, hardness, and quantity of remaining double bonds (determined previously).
Diacetyl or propanal agents were added in varying concentrations to monomer mixtures. The resins were made light-curing and those used for measurement of wear were loaded with filter. The results were analyzed by ANOVA and Newman-Keuls' multiple range tests.
In the composite systems, adding diacetyl or propanal resulted in decreased in vitro wear. The quantity of remaining double bonds in the dental polymers with these additives was also reduced. Their effect on Wallace indentation depth was less clear-cut. Low concentrations of additives decreased indentation depth of the unfilled materials, whereas high concentrations increased indentation depth. If it assumed that differences in the polymer have a major influence on the wear when the filter content and particle matrix interface are kept constant, then the hardness data on the unfilled resin can be used to correlate property changes of the polymer in the composite. A three-dimensional regression analysis found that in vitro wear decreased with decreasing Wallace indentation depth and decreasing quantity of remaining double bonds.
Addition of diketone or monoaldehyde to resin monomers may provide a means of increasing wear resistance of composites and allow their use in stress-bearing areas.
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