Camphorquinone Research Articles

Sesamin as a co-initiator for unfilled dental restorations

A natural component, sesamin (SA), was used to replace conventional amine as co-initiator for dental composite. A combination of camphorquinone (CQ) and SA was employed to initiate the photopolymerization of 2-2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl] propane/triethylene glycol dimethacrylate (70/30 wt.%). The kinetics was recorded by real-time Fourier transform infrared spectroscopy. The mechanical properties were measured by dynamic mechanical analysis, the cell toxicity was investigated by MTT assay and a mixture of CQ and ethyl 4- N, N-dimethylaminobenzoate (EDMAB) was used as control in the same photocuring condition. The results indicated that the addition of SA as co-initiator greatly improved the rate of polymerization and final double-bond conversion (DC) when compared with the system initiated by CQ alone. Compared with EDMAB, the final DC of the CQ/SA system (71%) was slightly lower than that of CQ/EDMAB (76%); SA resulted in approximately the same storage modulus at around 37 °C, but a slightly higher glass transition temperature. SA produced lower yellowing effect and good in vitro biocompatibility. The water sorption and solubility for two mixtures were very close and within the range of the ISO 4049 specification. These results suggest that SA is an effective alternative co-initiator to conventional amine. The natural compound characteristics of SA make it more promising than amine in dental resin formulations.

Preparation and characterization of a water soluble methylated β‐cyclodextrin/camphorquinone complex

AbstractA water soluble methylated β‐cyclodextrin/camphorquinone (MCD/CQ) complex, based on methylated β‐cyclodextrin (MCD) and camphorquinone (CQ), was prepared and its structure was characterized by FTIR, 1H‐NMR, and UV–vis spectra. The photopolymerization kinetics of MCD/CQ in the water soluble monomer system was studied by Real‐time Infrared spectroscopy (RT‐IR). Compared to the photopolymerization carried out under nearly identical conditions but without MCD, the polymerization rate and final conversion initiated by a CQ‐triethanolamine photoinitiator system were slightly lower. The effects of different MCD/CQ concentration, triethanolamine concentration, and light intensity were also studied. Copyright © 2009 John Wiley & Sons, Ltd.

The effect of the mixtures of photoinitiators in polymerization efficiencies

AbstractThe photoinitiated polymerization of methyl methacrylate using the mixtures of camphorquinone (CQ) and acylphosphine oxides (monoacylphosphine oxide, MAPO, or bisacylphosphine oxide, BAPO) was studied to determine the possible synergistic effects. The addition of the acylphosphines to CQ resulted in an increase of the polymerization rate compared with CQ alone. On the other hand, a significant decrease of the polymerization quantum yield is observed for the mixtures compared with the pure acylphosphines. Therefore, the increase in the polymerization efficiency of the two mixtures studied, MAPO/CQ and BAPO/CQ (compared with CQ) can be traced to the larger light absorption range, rather than to the onset of new mechanisms. The presence of the coinitiator ethyl 4‐dimethylaminobenzoate, EDB, always present in CQ formulations, has no effect at all on the rates of polymerization photoinitiated by the acylphosphine oxides. From the point of view of photopolymerization quantum yields, an antagonistic effect is observed because of the energy transfer of the more efficient initiator (MAPO or BAPO) to the less efficient one (CQ). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Photoinitiation rate profiles during polymerization of a dimethacrylate-based resin photoinitiated with camphorquinone/amine. Influence of initiator photobleaching rate

The photodecomposition of camphorquinone (CQ)/amine during the photo polymerization of a dimethacrylate-based resin under continuous irradiation was investigated in thick samples. The global CQ photoconsumption was measured by monitoring the decrease in light absorption as a function of irradiation time and the kinetics were satisfactory fitted to a first order expression where the rate constant of photobleaching was proportional to the irradiation intensity. In a thick sample, the photobleaching of the photoinitiator is accompanied by a deeper penetration of the light through the underlying layers. These gradients of photoinitiator concentration, light intensity and photoinitiation rate along the path of irradiation were calculated. The photodecomposition reaction was spatially inhomogeneous and the degree of nonuniformity increased with increased initial sample absorbance. The influence of the photobleaching process on the polymerization reaction was examined. The photobleaching rate of CQ was much slower than the polymerization rate and only 20% of the initial amount of CQ was consumed before the polymerization reaction had almost ceased. Results obtained in this research highlight the inherent interlinking of light attenuation and photobleaching rate in bulk polymerizing systems.

A visible light photochemical route to silver–epoxy nanocomposites by simultaneous polymerization–reduction approach

The in situ synthesis of silver–epoxy nanocomposite by visible light photoinduced processes was described. The visible light photoinitiator, camphorquinone (CQ) (2,3-bornanedione), was used to generate electron-donating radicals upon photolysis. Subsequent oxidation of these radicals to the corresponding cations in the presence of silver hexafluoroantimonate (AgSbF6) leads to the simultaneous formation of silver nanoparticles and initiation of cationic polymerization of epoxy resin, 1,3-bis(3,4-epoxycyclohexylethyl)tetramethyldisiloxane (EPOX) present in the formulation. The cured nanocomposites were characterized by FT-IR, DSC and TEM measurements.

Effect of co-initiator ratio on the polymer properties of experimental resin composites formulated with camphorquinone and phenyl-propanedione

Objectives To evaluate the effect of amine ratio (ethyl 4-dimethylaminobenzoate, EDMAB) on the maximum rate of polymerization ( R p max ), degree of conversion (DC), Knoop hardness (KH), water sorption (Wsp), water solubility (Wsl) and color changes (Δ E) over time of resin composites formulated with the photoinitiators camphorquinone (CQ), phenylpropanedione (PPD) and CQ-PPD in combination. Materials and methods Experimental resin composites were made with photoinitiator:amine ratios of 2:1, 1:1, 1:1.5 and 1:2 by weight. R p max was evaluated with differential scanning calorimetry (DSC), DC with DSC and Fourier transformed infrared (FTIR) spectroscopy, KH with Knoop indentation, Wsp and Wsl adapted from ISO 4049; and color with a chromameter. The results were analyzed with two-way ANOVA/Tukey’s multiple comparison test ( p < 0.05). Results The higher the amine ratio in the composite, the higher was DC, R p max , and KH, and the lower was Wsl, regardless of the photoinitiator type. The use of PPD alone resulted in poorer properties than CQ and CQ-PPD. Many factors seem to affect the color changes and the b-axis data revealed that the higher the amine ratio, the higher was the + b value (yellowing) for CQ and CQ-PPD formulations. Conclusions Higher amine ratios led to improved polymer properties, but also produced more yellowing in resin composites with CQ and CQ-PPD. The use of PPD alone was not advantageous for producing good final properties when compared to CQ and CQ-PPD.

Effect of initiator on photopolymerization of acidic, aqueous dental model adhesives

This study evaluated different initiator systems in self-etching model adhesives, in which camphorquinone (CQ) or [3-(3,4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy)-2-hydroxylpropy] trimethylammonium chloride (QTX) was employed as a photoinitiator (dye). N-phenylglycine (NPG), ethyl 4-dimethylaminobenzoate (4E) or 2-(dimethylamino) ethyl methacrylate (DMAEMA) was used as the coinitiator (CI). The role of diphenyliodonium hexafluorophosphate (DPIHP) in the polymerization process was also studied. The concentrations of dye, CI, and DPIHP in model adhesives were all maintained at 0.022 mmol per gram monomer. The model adhesive contained two monomers: (bis[2-(methacryloyloxy)ethyl] phosphate) (2MP) and 2-hydroxyethyl methacrylate (HEMA) whose mass ratio was 1:1, thus representing an acidic and hydrophilic formulation. The polymerization rate and the degree of conversion (DC) of the model adhesives with 5, 15, or 25% water content were determined using FTIR/ATR with a time-based spectrum analysis. The results indicated that with CQ as the photoinitiator, 4E appeared to be the most efficient CI, whereas the CQ-DMAEMA combination led to very low radical generation efficiency (DC < 5%). DPIHP exhibited little effect on the polymerization process. With QTX as the photoinitiator, however, DPIHP played an essential role. Without DPIHP, all three QTX-CI systems failed to initiate polymerization (DC < 5%). The QTX-DPIHP combination, on the other hand, was found to be a viable initiator system. The above results provide the critical information for the development of self-etching adhesive systems.

Influence of thermal expansion on shrinkage during photopolymerization of dental resins based on bis-GMA/TEGDMA

Objective The aim of this study was to assess volume changes that occur during photopolymerization of unfilled dental resins based on bis-GMA-TEGDMA. Methods The resins were activated for visible light polymerization by the addition of camphorquinone (CQ) in combination with dimethylamino ethylmethacrylate (DMAEMA) or ethyl-4-dimethyl aminobenzoate (EDMAB). A fibre-optic sensing method based on a Fizeau-type interferometric scheme was employed for monitoring contraction during photopolymerization. Measurements were carried out on 10 mm diameter specimens of different thicknesses (1 and 2 mm). Results The high exothermic nature of the polymerization resulted in volume expansion during the heating, and this effect was more pronounced when the sample thickness increased. Two approaches to assess volume changes due to thermal effects are presented. Due to the difference in thermal expansion coefficients between the rubbery and glassy resins, the increase of volume due to thermal expansion was greater than the decrease in volume due to thermal contraction. As a result, the volume of the vitrified resins was greater than that calculated from polymerization contraction. The observed trends of shrinkage versus sample thickness are explained in terms of light attenuation across the path length during photopolymerization. Significance Results obtained in this research highlight the inherent interlinking of non-isothermal photopolymerization and volumetric changes in bulk polymerizing systems.

Avaliação da atividade herbicida de algumas quinonas

Six commercial quinones (2,5 - dihydroxy-1,4-benzoquinone [1], camphorquinone [2], phenantrequinone [3], anthrarufin [4], sodium sulfonate anthraquinone [5] and lapachol [6]) were tested as for their phytotoxic potential. The compounds were tested on Sorghum bicolor , Cucumis sativus , and Desmodium tortuosum cultivated in washed sand in Petri dishes and on Lactuca sativa , Cucumis sativus , Desmodium tortuosum , Hyptis suaveolens and Euphorbia heterophylla , cultivated in pots, containing washed sand, for 20 days. In the tests in Petri dishes, quinone 2 caused a little inhibition (25.62%) to the development of S. bicolor . Quinones 1, 2, 3 and 5 caused a very little effect on C. sativus . None of the tested quinones caused a significant inhibition effect to D. tortuosum . In the bioassays in pots, quinones 2, 3, 4 and 6 caused a significant inhibition (9.52 to 71.43%) to the root system of H. suaveolens

Influence of photoinitiator type on the rate of polymerization, degree of conversion, hardness and yellowing of dental resin composites

Objectives To evaluate the degree of conversion (DC), maximum rate of polymerization ( R p max ), Knoop hardness (KHN) and yellowing ( b-value) of resin composites formulated with phenylpropanedione (PPD), camphorquinone (CQ), or CQ/PPD at different concentrations. The hypotheses tested were (i) PPD or CQ/PPD would produce less R p max and yellowing than CQ alone without affecting DC and KHN, and (ii) R p max , DC, and KHN would be directly related to the absorbed power density (PD abs). Methods CQ/amine, PPD/amine and CQ/PPD/amine were used at low, intermediate and high concentrations in experimental composites. Photoinitiator absorption and halogen-light emission were measured using a spectrophotometer, R p with differential scanning calorimetry (DSC), DC with DSC and FTIR, KHN with Knoop indentation; and color with a chromameter. The results were analyzed with two-way analysis of variance (ANOVA)/Student–Newman–Keul's test ( p < 0.05). Correlation tests were carried out between PD abs and each of DC, R p max and KHN. Results The PD abs increased with photoinitiator concentration and PPD samples had the lowest values. In general, maximum DC was comparable at intermediate concentration, while R p max and KHN required higher concentrations. DC was similar for all photoinitiators, but R p max was lower with PPD and CQ/PPD. PPD produced the lowest KHN. Yellowing increased with photoinitiator concentration. PPD did not reduce yellowing at intermediate and/or high concentrations, compared to CQ-formulations. PD abs showed significant correlations with DC, R p max and KHN. Conclusion PPD or CQ/PPD reduced R p max in experimental composites without affecting the DC. The use of PPD did not reduce yellowing, but reduced KHN. DC, R p max and KHN were dependent on PD abs.

Cure width potential for MOD resin composite molar restorations

Objectives To investigate the capability of modern light-curing units exhibiting differences in emission spectra and light source exit window dimensions, for “one-shot” full-width curing of extensive (molar MOD) resin composite restorations. Method Specimens of Tetric (TT), Tetric Ceram HB (TC), Tetric Evoceram (TE) and Tetric Ceram Bleach (TB) resin composites containing varying ratios of Lucirin (TPO) and/or camphorquinone (CQ) photoinitiators were packed into a bar-shaped mould (12 mm length × 2 mm width × 2 mm thickness). Each product was irradiated using a halogen (Optilux 401; QTH), a conventional LED (LEDemetron; LED) and two so-called “third generation” oval-footprint LED light-curing units (LCUs) of the same model. The latter featured bimodal emission spectra (blue and ultraviolet diodes) with either high (unmodified output) and approximately 50% (modified output) blue light intensity (UltraLume-5; ULs, ULm, respectively). Vickers hardness number was obtained across the lateral extent of the bar at 1 mm increments from the centre point on both upper and lower surfaces of the specimens. Results Significant linear relationships ( R 2 = 0.71–0.98) for each distance from the central position of all LCUs were identified between measured light intensity and corresponding upper and lower surface hardness values for each product ( P < 0.05). No significant differences ( P > 0.05) were recorded in total upper surface hardness of TC or TE cured with LED (68.7 ± 3.2 and 70.5 ± 2.5) or ULm (56.8 ± 2.0 and 57.7 ± 2.0). However, upper surface hardness of TT (CQ only) cured with ULm was significantly decreased ( P < 0.05) compared with other LCUs. When the ratio of hardness at the edge to central positions of the bar-shaped specimens for either surface was calculated, no significant difference ( P > 0.05) was identified for TB (containing TPO and decreased CQ) cured with either ULs or ULm ( P > 0.05) and was significantly increased (P < 0.05) when cured with ULs compared with LED and QTH. Significance Variability in light intensity across the curing-tip face, spectral output of dental light-curing units and differences in product photoinitiator chemistry all influence curing efficiency significantly across the width of extensive resin composite geometries.

Synthesis and Characterization of UV‐Curable Poly(dimethylsiloxane) Dimethacrylate

AbstractThis paper presents a new route to the synthesis of UV‐curable poly(dimethylsiloxane) dimethacrylate (PDMSDMA). PDMSDMA was essentially prepared by modification of poly(dimethylsiloxane), bis(3‐aminopropyl) terminated (PDMS‐NH2) with methacrylic anhydride (MAA). The synthesized products were cured under UV in the presence of camphorquinone (CQ) used as a photoinitiator. The chemical structure of PDMSDMA samples was analyzed by FT‐IR and 1H‐NMR spectroscopy. The 1H‐NMR spectrum of PDMSDMA revealed new peaks at 3.20 ppm, corresponding to methylene protons in CH2NH, and 5.25 and 5.65 ppm, corresponding to vinylic protons in NHCOCCH3CH2. The chemical structure of the cured products and the degree of curing were determined by solid state 13C CP/MAS NMR and FT‐IR (Micro‐ATR) spectroscopy. Various parameters, such as concentration of methacrylic anhydride, amount of camphorquinone, and curing time, were studied.

The effect of using mixed initiator systems on the efficiency of photopolymerization of dental resins

A study was performed in order to determine the efficiency of the simultaneous use of the photoinitiators phenylpropanedione (PPD) and camphorquinone (CQ) in the polymerization of acrylic polymers and evaluate possible mechanisms leading to synergism or antagonism. It was found that efficiencies of both initiators taken individually are higher than that of their mixture, indicating that when both dyes are used simultaneously there will be an energy transfer from the more efficient initiator (CQ) to the less efficient one (PPD). Also, there was no proof of any reaction between the amine present in the CQ formulation and the PPD excited state.

Effects of visible light-irradiated camphorquinone and 9-fluorenone on murine oral mucosa

The purpose of this study was to evaluate the histopathological effects of camphorquinone (CQ) and 9-fluorenone (9F) with or without visible light (VL) irradiation on the oral mucous membranes of mice. VL irradiation resulted in a higher degree of tissue damage after CQ or 9F application, particularly the latter. Necrosis and apoptosis were responsible for the tissue damage after application of either agent in the presence of VL irradiation.

Benzoyl germanium derivatives as novel visible light photoinitiators for dental materials

Objectives The objective of this study was to investigate the use of benzoyl germanium derivatives as a novel visible light photoinitiator of resin-based dental composites. Selected mechanical properties, such as flexural strength and flexural modulus, setting time, storage stability, and UV light stability, of the composites based on the novel photoinitiators benzoyltrimethylgermane (BTMGe) or dibenzoyldiethylgermane (DBDEGe) were investigated and compared to the properties of materials that are cured with a mixture of camphorquinone (CQ) and ethyl 4-( N, N-dimethylamino)benzoate (EMBO). Methods The flexural strength and flexural modulus of elasticity were determined according to ISO 4049. For this purpose, test specimens (2 mm × 2 mm × 25 mm) of the composites investigated were prepared in stainless steel moulds and light-cured (150 mW/cm 2, 2 s × 180 s). The flexural strength and flexural modulus of elasticity were measured after immersing the cured specimens in water for 24 h at 37 °C and in certain cases, after they had been boiled for 24 h in water. In addition, the setting time, curing depth, storage and UV stability of selected composites were determined. Results The novel photoinitiators BTMGe or DBDEGe can be used to substitute the binary photoinitiator CQ/EMBO in visible light-cured restorative composites. Especially, DBDEGe showed a significantly higher photocuring activity in composites with a filler load of about 60 wt. % in comparison to that of CQ/EMBO. In addition, composites based on BTMGe or DBDEGe showed an improved UV stability and a storage stability comparable to that of CQ/EMBO-based composites.

Onium salt reduces the inhibitory polymerization effect from an organic solvent in a model dental adhesive resin

This study evaluated the effect of organic solvent concentration on the polymerization kinetics for a model dental 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, which was polymerized using a binary system [camphorquinone (CQ) and ethyl 4-dimethylamine benzoate (EDAB)] and a ternary system [CQ, EDAB, and diphenyliodonium hexafluorphosphate (DPIHFP)]. Additionally, these blends had 0, 10, 20, 30, and 40 wt % ethanol added. Real-time Fourier transform infrared spectroscopy was used to investigate the polymerization reaction over photoactivation time. Data were plotted, and Hill's three-parameter nonlinear regression was performed for curve fitting. The addition of a solvent to the monomer blends decreased the polymerization kinetics, directly affecting the rate of polymerization, delaying vitrification, and attenuating the Trommsdorf effect. The introduction of DPIHFP displayed a strong increase in reaction kinetics, reducing the solvent inhibition effect. After 10 s of photoactivation, the binary system obtained in 0, 10, 20, 30, and 40% of ethanol, a degree of conversion of 44.6, 26.3, 13.4, 1.15, and 0.0%, respectively, whereas when a ternary system was used, the values were 54.6, 40.5, 27.4, 14.5, and 3.4%. An improvement was observed in the polymerization kinetics of a model dental adhesive resin when using a ternary photoinitiation system, making the material less sensitive to the residual presence of a solvent before photoactivation.

New Photocleavable Structures, 4

AbstractAs highly reactive acylphosphine oxide‐based photoinitiators (PIs) are limited in the application for dental materials by their absorption behavior, we were interested to prepare acylgermane 1. UV‐Vis absorption maximum of the important n–π* transition was red shifted about 30 nm compared to monoacylphosphine oxides. Photo‐DSC results with a dental LED lamp showed nearly the same reactivity for 1 compared to camphorquinone (CQ), while monoacylphosphine oxides are not reactive. In broadband irradiation experiments, significantly higher reactivity compared to CQ was found. Application‐oriented tests showed sufficient storage stability of the formulation and excellent photobleaching behavior.magnified image

Effects of water content and initiator composition on photopolymerization of a model BisGMA/HEMA resin

Aims The purpose of this study was to evaluate the effects of photoinitiator type and water content on the polymerization rate ( R p) and degree of conversion (DC) of a model BisGMA/HEMA-based resin. Materials and methods The comonomer mixture consisted of BisGMA/HEMA (60/40 by weight). Different two- or three-component photoinitiator systems were incorporated. Two-component systems were 0.5% CQ (camphorquinone) and 0.5% DMAEMA (2-(dimethylamino) ethyl methacrylate) or 0.5% CQ and 0.5% 4E (ethyl 4-dimethylaminobenzoate). The three-component systems were added 1% DPIHP (diphenyliodonium hexafluorophosphate) to the above systems. Each system was tested as made, or after addition of 5, 10, 15 wt% water. When cured under a conventional dental light, the R p and DC of each formulation was determined using time-resolved attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopy. Results For mixtures containing two-component initiator systems, when the hydrophobic initiator CQ was used in combination with hydrophilic DMAEMA, R ps and DCs were dramatically decreased as a function of water content. The R ps and DCs of the hydrophobic CQ/4E system were higher than those of the CQ/DMAEMA system in the presence of water. For three-component initiator systems, incorporation of DPIHP enhanced the polymerization of all mixtures in the presence of water compared to their counterpart two-component initiators. Interestingly, the CQ/DMAEMA caused greater DC and R p when DPIHP was used. Significance The hydrophobicity/hydrophilicity of photoinitiator components significantly affects both the DC as well as R p when in the presence of water. The results indicate that formulation of photoinitiator components should be based on the effectiveness of the bonding systems under both dry and wet conditions.

A comparison of efficiency of two photoinitiators for polymerization of light‐cure dental composite resins

AbstractThe purpose of the study was to compare the effect of two photoinitiators, (−)camphorquinone (CQ) and 1‐phenyl‐1,2‐propanedione (PPD) on curing performance of light‐cure dental composite resins. Bisphenol A‐glycidyl methacrylate (BisGMA)/triethylene glycol dimethacrylate (TEGDMA) monomer mixture was used as the resin matrix. The resin matrix was mixed with CQ and/or PPD along with 0.25% of 4‐(dimethyl amino) phenethyl alcohol (DMAPEA) catalyst. The effect of photoinitiator on curing performance was evaluated and compared in terms of properties such as depth of cure, diametral tensile strength (DTS), flexural strength (FS), flexural modulus (FM), vickers hardness number (VHN), water sorption (WS), and solubility of cured composite. Statistical evaluation using Analysis of Variance (single factor) showed that the photosensitization efficiency of CQ and PPD are comparable. However, their combination showed synergistic effect for properties such as DTS and solubility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Photopolymerization of N, N-dimethylaminobenzyl alcohol as amine co-initiator for light-cured dental resins

Objective The present study was carried out in order to assess the suitability of N, N-dimethylaminobenzyl alcohol (DMOH) as co-initiator of camphorquinone (CQ) and 1-phenyl-1,2-propanedione (PPD) in light-cured dental resins. Methods DMOH was synthesized and used as co-initiator for the photopolymerization of a model resin based on {2,2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl]propane} (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA). Experimental formulations containing CQ or PPD in combination with DMOH at different concentrations were studied. The photopolymerization was carried out by means of a commercial light-emitting diode (LED) curing unit. The evolution of double bonds consumption versus irradiation time was followed by near-infrared spectroscopy (NIR). The photon absorption efficiency (PAE) of the photopolymerization process was calculated from the spectral distribution of the LED unit and the molar absorption coefficient distributions of PPD and CQ. Results DMOH is an efficient photoreducer of CQ and PPD resulting in higher polymerization rate and higher double bond conversion compared with dimethylaminoethylmethacrylate. The PAE for PPD was higher than that for CQ. However, the polymerization initiated by PPD progressed at a lower rate and exhibited lower values of final conversion compared with the resins containing CQ. This observation indicates that the lower polymerization rate of the PPD/amine system should be explained in terms of the mechanism of generating primary radicals by PPD, which is less efficient compared with CQ. Significance The DMOH/benzoyl peroxide redox system, has recently been proposed as a more biocompatible accelerator for the polymerization of bone cements based on poly(methyl methacrylate), because cytotoxity tests have demonstrated that DMOH possesses better biocompatibility properties compared with traditional tertiary amines. The results obtained in the present study reveal the suitability of the CQ/DMOH initiator system for the polymerization of light-cured dental composites.