Camphorquinone Research Articles

Color stability of experimental composites containing different photoinitiators

ObjectivesTo evaluate the color stability (ΔE) of experimental composites containing different photoinitiators when submitted to accelerated artificial ageing (AAA). Material and methodsThirty test specimens were made in a Teflon matrix (8mm×2mm), using an experimental composite (n=10) with the same monomer composition and particle size, but varying photoinitiator used: Group CQ (0.4% Camphorquinone), Group PPD (0.4% 1-Phenyl-1,2 Propanodione) and Group CQ+PPD (0.2% CQ+0.2% PPD). The samples were light activated (QTH – Ultralux – Dabi Atlante – 40s) and polished before performing the initial color readouts (EasyShade – Vita). Next, they were submitted to AAA for 300h, after which final color readouts were made. ResultsThe results (1-way ANOVA – Tukey – p<0.05) demonstrated that all the groups presented color alteration above the clinically acceptable level (ΔE≥3.3), however, with no statistically significant difference among them (p>0.05). Analysis of Δb demonstrated increase in the values of this coordinate, indicating yellowing in all groups. ConclusionsIt was concluded that the type of photoinitiator, which presented a tendency towards yellowing, did not interfere in the color stability of composites submitted to AAA. Clinical significanceAlternative photoinitiators have been extensively studied since Camphorquinone presents a yellowish color, which compromises the aesthetic performance of composites, especially the lighter-shade ones.

Polymerization kinetics and reactivity of alternative initiators systems for use in light-activated dental resins

ObjectivesThe purpose of this study was to evaluate the reactivity and polymerization kinetics behavior of a model dental adhesive resin with water-soluble initiator systems. MethodsA monomer blend based on Bis-GMA, TEGDMA and HEMA was used as a model dental adhesive resin, which was polymerized using a thioxanthone type (QTX) as a photoinitiator. Binary and ternary photoinitiator systems were formulated using 1mol% of each initiator. The co-initiators used in this study were ethyl 4-dimethylaminobenzoate (EDAB), diphenyliodonium hexafluorophosphate (DPIHFP), 1,3-diethyl-2-thiobarbituric acid (BARB), p-toluenesulfinic acid and sodium salt hydrate (SULF). Absorption spectra of the initiators were measured using a UV–Vis spectrophotometer, and the photon absorption energy (PAE) was calculated. The binary system camphorquinone (CQ)/amine was used as a reference group (control). Twelve groups were tested in triplicate. Fourier-transform infrared spectroscopy (FTIR) was used to investigate the polymerization reaction during the photoactivation period to obtain the degree of conversion (DC) and maximum polymerization rate (Rpmax) profile of the model resin. ResultsIn the analyzed absorption profiles, the absorption spectrum of QTX is almost entirely localized in the UV region, whereas that of CQ is in the visible range. With respect to binary systems, CQ+EDAB exhibited higher DC and Rpmax values. In formulations that contained ternary initiator systems, the group CQ+QTX+EDAB was the only one of the investigated experimental groups that exhibited an Rpmax value greater than that of CQ+EDAB. The groups QTX+EDAB+DPIHFP and QTX+DPIHFP+SULF exhibited values similar to those of CQ+EDAB with respect to the final DC; however, they also exhibited lower reactivity. SignificanceWater-soluble initiator systems should be considered as alternatives to the widely used CQ/amine system in dentin adhesive formulations.

Diastereospecific ring cleavage of bornane-2,3-dione in the Bucherer-Bergs reaction

A novel regio- and diastereospecific ring cleavage of bornane-2,3-dione (camphor quinone) under Bucherer-Bergs reaction conditions has been investigated. The simplicity of this transformation provides a novel and straightforward synthetic pathway to enantiopure derivatives of cyclopentane carboxylic acid as well as functionalized hydantoins in just two steps, starting from inexpensive and easily available camphor.

Polymerization of methacrylate resins photoinitiated by camphorquinone and bulky amine-functionalized silsesquioxanes

Polyhedral oligomeric silsesquioxanes (SSQO) functionalized with bulky amino groups were prepared by a two-stage synthesis procedure. In a first stage, a modified organotrimethoxysilane was synthesized by reacting 1 mol of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane with 3 mol of 1,2-epoxy-3-phenoxypropane. The second stage consisted of the hydrolytic condensation of the modified silane catalyzed by formic acid. Methacrylate resins were activated for visible light polymerization by the addition of camphorquinone (CQ) in combination with different mass fractions of SSQO. The progress of monomer conversion versus irradiation time showed that the CQ/SSQO pair is an efficient photoinitiator system because a fast reaction and high conversion results from 60 s irradiation at 600 mW/cm2. The SSQO were incorporated up to 22 wt% in the methacrylate resin without compromising the flexural or the compressive properties of the final material.

Iodonium salt improves the dentin bonding performance in an experimental dental adhesive resin

The aim of this study was to evaluate the influence of an iodonium salt on the immediate and long-term microtensile bond strength to dentin of an experimental dental two-step, self-etching adhesive system. A model dental adhesive resin was formulated using bisphenol A glicidyl dimethacrylate (Bis-GMA), triethylene glicol dimethacrylate (TEGDMA), and hydroxyethyl methacrylate (HEMA), which was polymerized using four combinations of photo-initiators and coinitiators. A group using only camphorquinone (CQ), two binary systems (CQ and ethyl 4-dimethylamine benzoate (CQ+EDAB), CQ and diphenyliodonium hexafluorphosphate (CQ+DPIHFP)) and a ternary system (CQ+EDAB+DPIHFP) was investigated. Clearfil SE Bond (CSEB) was used as a commercial reference. Bond strength to bovine dentin was assessed through microtensile bond tests measured in MPa in a universal testing machine. The beam specimens were stored in distilled water at 37°C for 24h and 1 year. Two-way ANOVA and Student–Newman–Keuls' post-hoc tests were used to compare means of groups (α=5%) and failure modes classified under magnification. After 24h, the ternary system showed a bond strength similar to that of the binary system CQ+EDAB and the commercial material. After 1 year of storage, the μTBS values of the group CQ+EDAB+DPIHFP showed a bond strength significantly higher (p<0.05) than those of the CQ, CQ+DPIHFP, and CQ+EDAB groups and no difference from that of the CSEB group. The ternary photo-initiator system with iodonium salt maintained increased bond strength to dentin of model self-etching adhesive systems after 1 year of aging.

Photoelastic evaluation of the effect of composite formulation on polymerization shrinkage stress

We compared polymerization stress in two commercial composites and three experimental composites made using camphorquinone (CQ) and/or phenylpropanedione (PPD) as photoinitiators. The internal surfaces of photoelastic resin discs with cylindrical cavities were roughened and treated with adhesive. Composites were divided into five groups: two commercial composites (Filtek Silorane and Filtek Z250) and three experimental composites with CQ/amine, CQ/PPD/amine, and PPD/amine. Composites were photopolymerized inside cavities, and subjected to photoelastic analysis immediately and at 24 hours and 7 days later using a plane polariscope. Stress created by Silorane (3.08 ± 0.09 MPa) was similar to that of Z250 (3.19 ± 0.13 MPa) immediately after photopolymerization (p > 0.05). After 24 hours and 7 days, Z250 (3.53 ± 0.15 and 3.69 ± 0.10 MPa, respectively) showed higher stress than Silorane (3.19 ± 0.10 and 3.16 ± 0.10 MPa, respectively). Qualitative analysis immediately after photopolymerization showed composite/CQ promoted higher stress than PPD, but stress levels at other evaluated times were statistically similar, varying between 3.45 ± 0.11 MPa and 3.92 ± 0.13 MPa. At 24 hours and 7 days, Silorane created the lowest stress. All photoinitiators created comparable tensions during polymerization.

Benzodioxoles as alternative coinitiators for radical polymerization in a model‐dental adhesive resin

AbstractThis study evaluated the effectiveness of benzodioxole derivatives as coinitiators of radical polymerization in a model‐dental adhesive resin. To compose the adhesive resin, a monomer mixture based on 50 wt % of Bis‐GMA, 25 wt % of TEGDMA, and 25 wt % of HEMA was used. Camphorquinone (CQ) 1 mol % was used as a photoinitiator to initiate polymerization. 1,3‐Benzodioxole (BDO) and piperonyl alcohol (PA) were used as coinitiators at 0.25, 0.5, 1, 2, 4, 8, and 16 mol % level. In addition, tertiary amine, ethyl 4‐dimethylamino benzoate (EDAB) was used as coinitiator in the control group. Some physical, chemical, and mechanical properties of the polymer formed in the experimental adhesives were evaluated using the kinetics of polymerization, sorption and solubility, flexural strength, and elastic modulus tests. The results indicated that BDO and PA were effective coinitiators in the photoinitiator system based on CQ. Comparisons between the benzodioxoles derivative coinitiators and EDAB showed similar performance in the kinetics of polymerization and flexural strength. For water sorption and solubility evaluation, BDO and PA demonstrated significantly more sorption of water and less solubility than the EDAB control group. The findings suggest that BDO and PA were feasible alternatives to conventional amine as coinitiator. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Synthesis and photooxidation of styrene copolymer bearing camphorquinone pendant groups

(±)-10-Methacryloyloxycamphorquinone (MCQ) was synthesized from (±)-10-camphorsulfonic acid either by a known seven-step synthetic route or by a novel, shorter five-step synthetic route. MCQ was copolymerized with styrene (S) and the photochemical behavior of the copolymer MCQ/S was compared with that of a formerly studied copolymer of styrene with monomers containing the benzil (BZ) moiety (another 1,2-dicarbonyl). Irradiation (λ > 380 nm) of aerated films of styrene copolymers with monomers containing the BZ moiety leads to the insertion of two oxygen atoms between the carbonyl groups of BZ and to the formation of benzoyl peroxide (BP) as pendant groups on the polymer backbone. An equivalent irradiation of MCQ/S led mainly to the insertion of only one oxygen atom between the carbonyl groups of camphorquinone (CQ) and to the formation of camphoric anhydride (11) covalently bound to the polymer backbone. While the decomposition of pendant BP groups formed in irradiated films of styrene copolymers with pendant BZ groups leads to crosslinking, only small molecular-weight changes in irradiated MCQ/S were observed.

Photopolymerization experiments and properties of some urethane/urea methacrylates tested in dental composites

Hydrophobic silyl-urea/urethane methacrylates (UHM-1, UHM-2) and a modified BisGMA derivative (BisGMA-UMA) were synthesized and used as photopolymerizable co-monomers in the preparation of dental composites, besides other urethane dimethacrylates containing oligoethylene oxide segments and carboxylic groups. The homo- and copolymerization behaviour of the synthesized monomers were investigated by FTIR spectroscopy using camphorquinone (CQ) and 4-(dimethylamino)-phenylacetic acid (DMPheAA) as a photoinitiating system, as well as by photo-DSC. The first hybrid monomethacrylate, N-(methacryloyloxyethyl-N’-diethoxymethylsilylpropyl)-urea showed the highest value for the maximum polymerization rate (0.117 s−1) followed by BisGMA analogue (0.085 s−1) and N-methacryloyloxyethyl-N’-bis(triethoxysilylpropylcarbamoyloxyethyl)-urea (0.069 s−1), whereas the degree of conversion decreased from 75.1% (UHM-2) to 41.6% (BisGMA-UMA). Polymerization shrinkage (PS) measured by picnometry for the mixture BisGMA-UMA/TEGDMA (4.78 vol.%) was lower than that exhibited of the control organic matrix BisGMA/TEGDMA (6.85 vol.%) at the same dilution. The addition of one of the obtained monomers into a mixture based on urethane oligomers led to a polymerization shrinkage varying between 8.33 and 6.97 vol.%. A number of properties of the composites formulated with our urethane methacrylates, a urethane dimethacrylate, BisGMA, and glass filler (Zr/Sr glass, quartz, and diatomite) were also determined including the surface damage caused by the Vickers indentation to establish their utility in dentistry.

Visible light crosslinkable chitosan hydrogels for tissue engineering

In situ gelling constructs, which form a hydrogel at the site of injection, offer the advantage of delivering cells and growth factors to the complex structure of the defect area for tissue engineering. In the present study, visible light crosslinkable hydrogel systems were presented using methacrylated glycol chitosan (MeGC) and three blue light initiators: camphorquinone (CQ), fluorescein (FR) and riboflavin (RF). A minimal irradiation time of 120s was required to produce MeGC gels able to encapsulate cells with CQ or FR. Although prolonged irradiation up to 600s improved the mechanical strength of CQ- or FR-initiated gels (compressive modulus 2.8 or 4.4kPa, respectively), these conditions drastically reduced encapsulated chondrocyte viability to 5% and 25% for CQ and FR, respectively. Stable gels with 80–90% cell viability could be constructed using radiofrequency (RF) with only 40s irradiation time. Increasing irradiation time up to 300s significantly improved the compressive modulus of the RF-initiated MeGC gels up to 8.5kPa without reducing cell viability. The swelling ratio and degradation rate were smaller at higher irradiation time. RF-photoinitiated hydrogels supported proliferation of encapsulated chondrocytes and extracellular matrix deposition. The feasibility of this photoinitiating system as in situ gelling hydrogels was further demonstrated in osteochondral and chondral defect models for potential cartilage tissue engineering. The MeGC hydrogels using RF offer a promising photoinitiating system in tissue engineering applications.

Effect of CQ-amine ratio on the degree of conversion in resin monomers with binary and ternary photoinitiation systems

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 (, , , ); Group B (, , , ); Group C (, , , ); Group D (, , , ); Group E (, , , ); Group F (, , , ). 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.

Synthesis of Silica Hybrid Nanoparticles and the Effect of Their Addition on the Hardness of the Dental Nanocomposites

The objective of this study is to investigate the effect of silica hybrid nanoparticles on the hardness of the dental nanocomposites. The silica hybrid nanoparticles were synthesized by sol-gel method. The powders were modified with 3-methacryloxy-propyltrimethoxy silane (γ-MPS) either by co-condensation method or one-pot method. The silanized silica were then mixed with a mixture of bisglycidyl methacrylate (BisGMA), triethylene glycol methacrylate (TEGDMA), camphorquinone (CQ) and dimethylaminoethyl methacrylate (DMAEMA) to form dental nanocomposites. The hardness of the nanocomposites were determined using vickers hardness. The results shown that hardness of the dental composites using silica hybrid nanoparticles synthesized via one-pot method was higher compared to the synthesized via co-condensation method. Transmission Electron Microscope (TEM), and Fourier Transform Infrared Spectroscopy (FTIR) were used for characterization.

Curing efficiency of dental resin composites formulated with camphorquinone or trimethylbenzoyl-diphenyl-phosphine oxide

ObjectivesSince photoinitiator systems for dental resins based on camphorquinone (CQ) present color disadvantages, trimethylbenzoyl-diphenyl-phosphine oxide (TPO) has been proposed as an alternative. However, there are remaining considerations about its curing efficiency. The aims of the present investigation were: to characterize the relationship between the photoinitiator absorption spectra and the light spectrum emitted from a QTH light (absorbed power density, PDabs); to evaluate the kinetics of polymerization, and the depth of cure for filled dimethacrylate resins formulated with different photoinitiator systems. MethodsCQ+EDMAB (control); TPO and TPO+EDMAB were used in 50:50 Bis-GMA/TEGDMA resins. Photoinitiator absorption and QTH-light emission were evaluated using a spectrophotometer and kinetics of polymerization with differential scanning calorimetry (DSC) (n=3). Depth of cure was analyzed by the scraping method (n=5), as recommended by ISO4049. One-way ANOVA/Tukey's (p<0.05) was used to analyze the results. ResultsCQ presented higher PDabs than TPO (364 and 223mW/cm3, respectively). The DSC revealed that TPO and TPO+EDMAB produced a faster reaction than CQ+EDMAB. Composite formulated with CQ+EDMAB produced higher depth of cure (6.3±0.4mm) than those with TPO (4.3±0.1) or TPO+EDMAB (4.2±0.3). SignificanceAlthough CQ presented higher PDabs than TPO, formulations containing TPO exhibited higher reactivity than that with CQ. On the other hand, materials formulated with TPO demonstrated lower depth of cure than that with CQ. Therefore, its use as an alternative photoinitiator requires further investigation, with higher concentrations.

Micro-Raman spectroscopic analysis of the degree of conversion of composite resins containing different initiators cured by polywave or monowave LED units

Objectives To determine the degree of conversion (DC) over 48 h post-curing of resin mixtures containing trimethylbenzoyl-diphenylphosphine oxide (TPO) initiator cured by a polywave or a monowave LED light-curing unit (LCU). Methods In resin mixtures based on equal weight percent (wt%) of BisGMA and TEGDMA the following initiators were added: 0.2 wt% camphorquinone (CQ) + 0.8 wt% ethyl-4-dimethylaminobenzoate (EDMAB) (Group 1); 1 wt% TPO (Group 2) and 0.1 wt% CQ + 0.4 wt% EDMAB + 0.5 wt% TPO (Group 3). Half of the samples in each group ( n = 5) were cured using a polywave (bluephase ® G2, Ivoclar Vivadent) or a monowave LED LCU (bluephase ®, Ivoclar Vivadent). The DC was measured using micro-Raman spectroscopy within 5 min and then 1, 3, 6, 24 and 48 h post-irradiation. The data were analysed using general linear model and two-way ANOVA for the factors ‘time’, ‘material’, ‘surface’ and ‘LCU’ at α = 0.05. Results The initial DC values obtained upon light curing remained similar over a 48 h period. bluephase ® G2 produced the highest DC in Group 2 followed by Group 3, and Group 1. bluephase ® resulted in the highest DC in Group 1, followed by Group 2 and Group 3 ( p < 0.05). Conclusions Unfilled resin materials containing both TPO– and CQ–amine initiators are effectively cured using bluephase ® G2. Resin mixture with the same wt% of initiators is better cured when TPO is the only initiator, compared to CQ–amine only or combined TPO and CQ–amine system. After initial light cure, no additional conversion of uncured monomers was detected in an unfilled resin material over 48 h at 37 °C.

Enhanced photopolymerization of dimethacrylates with ketones, amines, and iodonium salts: The CQ system

AbstractThe kinetics and mechanism of the photopolymerization of dimethacrylates using three‐component initiation systems consisting of camphorquinone (CQ), diphenyliodonium hexafluorophosphate (Ph2IPF6), and either N,N,3,5‐tetramethylaniline (TMA) or N,N‐dimethylbenzylamine or triethylamine were studied by photo‐DSC and UV‐visible spectroscopy. The effect of monomer structure on the curing kinetics and photobleaching were also investigated. Photo‐DSC studies showed fivefold increases in polymerization rate when all three components were present and the kinetics followed the trend: CQ/amine/Ph2IPF6 ≫ CQ/amine &gt; CQ/Ph2IPF6.. For both CQ/amine/Ph2IPF6 and CQ/amine systems, the CQ was rapidly photobleached during the photo‐DSC timescale but for the systems without amine there was an induction stage before CQ photobleaching was evident. Studies of the effect of monomer type on the photobleaching rate show that the photobleaching behavior was independent of monomer structure. Three photoinitiation mechanisms have been proposed. The reaction mechanism of the CQ/amine/Ph2IPF6 system involves the reduction of the excited CQ molecule by the amine to form ketyl and aminoalkyl radicals, followed by the irreversible oxidation of the amine, and to a lesser extent, the ketyl radical by the iodonium salt, to form an initiating radical. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Photooxidation of camphorquinone in polystyrene matrix

The photoreactivity of low molecular camphorquinone ( CQ) doped in aerated polystyrene matrix was studied. Irradiation at λ > 380 nm led mainly to the insertion of one oxygen atom between the carbonyl groups of camphorquinone ( CQ) and to the formation of camphoric anhydride ( 6). Minor products were cyclopentenecarboxylic acids ( 10a– c). Participation of the matrix on CQ photooxidation was negligible. The mechanism of photoconversion of CQ has been suggested.

Influence of silver nano-particles on monomer elution from light-cured composites

Objectives Silver containing materials have been used for years as antimicrobial materials. Silver particles were also added to experimental dental composites to reduce caries. The aim of our study was to show whether silver nanoparticles can lead to higher amounts of elutable substances. Methods 0.0125, 0.025, 0.05, 0.1 and 0.3% by weight silver nanoparticles were added to the commercial composite Tetric Flow ®. After light curing of the specimen, they were stored up to 7 days in methanol. The eluate was analyzed by gas chromatography/mass spectrometry. Results Compared to controls more camphorquinone (CQ), ethoxylated bisphenol-A-dimethacrylate (BisEMA) and triethylene glycol dimethacrylate (TEGDMA) will be eluted when silver nanoparticles were added to the composite. Twenty-four hours after the beginning of the experiment 132 μmol/l of CQ, 33.9 μmol/l BisEMA and 4.5 mmol/l TEGDMA were found in the eluate of the specimens containing 0.3% Ag. Significance Silver nanoparticles may influence the polymerization process in dental materials and lead to an increase in elutable substances. Four possible mechanisms of interaction are discussed: (1) reflection and scattering of the photons, (2) absorption of photons, (3) electron transfer from or to the silver nanoparticles and (4) formation of complexes with Ag +-ions.

Can phenyl-propanedione influence Knoop hardness, rate of polymerization and bond strength of resin composite restorations?

ObjectivesThe aim of this study was to evaluate the degree of conversion (DC), rate of polymerization (Rpmax), Knoop hardness (KHN) and bond strength between tooth/restoration of composite resins containing different photo-initiators photo-activated by different light-curing units (LCUs). Materials and methodsA mixture of BisGMA, UDMA, BisEMA and TEGDMA was prepared along with the following photo-initiators: camphorquinone (CQ), phenyl-propanedione (PPD) or the association (CQ/PPD) and 65wt% of silanated filler particles. The LCUs included a halogen lamp XL 2500 and two LEDs: UltraBlueIS and UltraLume5. The conversion profiles during photo-polymerization were investigated using middle-infrared spectroscopy (mid-IR). Bond strength was evaluated using push-out test in ninety teeth with prepared cavities. Before the push-out test, Knoop hardness (KH) was verified in the top and at the base of the restorations. ResultsPPD obtained lower Rpmax values, regardless of the LCU used. It also provided a greater bond strength than CQ when the LEDs LCUs were used. The degree of conversion after 40s of irradiation was the same for all composite resins, except PPD photo-activated for XL 2500, which showed lower DC values than CQ and CQ/PPD. In the top and at the base of the restorations, PPD showed the lowest KH values when photo-activated with XL 2500. XL 2500 produced higher KH values than UltraBlueIS when used with CQ or CQ/PPD photo-initiators. ConclusionBecause it increased the bond strength without compromising the properties of composite resins when photo-activated by an LED, PPD can be used as an alternative photo-initiator.

Properties of a new dental photocurable matrix resin with low shrinkage

In order to reduce the amount of volumetric shrinkage that occurs in dental composites as a result of curing, a new kind of dental matrix resin combining bisphenol-S-bis(3-meth acry late-2-hydroxy propyl)ether(BisS-GMA) with the expanding monomer unsaturated spiro orthoesters 2-methylene-1, 4, 6-trispiro[4, 4] nonane (SOE) was prepared, with triethylene glycol dimethacrylate (TEGDMA) as diluent. CQ (camphorquinone) of 1wt% and DMAEMA (2-(dimethylamino) ethyl meth acrylate) of 2wt% were used as photoinitiation system to initiate the copolymerization of the matrix resins. The performance including volumetric shrinkage, degree of conversion and condition of the ring-opening reaction of SOE, as well as curing time and the tensile bond strength were investigated respectively by the dilatometer, Fourier transfer infrared, the universal testing machine, and so on. The ring-opening polymerization of SOE occurred. Meanwhile, the obtain copolymers were crosslinked. The matrix resin containing BisS-GMA and SOE showed a reduced amount of volumetric shrinkage at 1.52%, which is a promising strategy for obtaining a polymer with a low amount of volumetric shrinkage. Furthermore, the other properties were not compromised.

Influence of DPSS Laser on Polymerization Shrinkage and Mass Change of Resin Composites

This study evaluated the effectiveness of the diode-pumped solid state (DPSS) laser as a light source for light-curing dental resin composites. A DPSS laser of 473 nm may be useful because of its match with the absorption peak of camphorquinone (CQ), the photoinitiator. A DPSS laser (LAS) of 473 nm and a quartz-tungsten-halogen (QTH) light-curing unit (OP) were used as the light sources for light curing six different resin composites (four nanocomposites and two hybrid composites). Polymerization shrinkage and mass change (water sorption and solubility) were measured during and after light curing to determine the degree of polymerization. Mass change was evaluated by following the ISO 4049 standard. According to the evaluation, the specimens light cured using LAS showed similar maximum polymerization shrinkage (12.3∼18.1 μm for LAS; 13.2∼16.2 μm for OP) and water sorption (11.4∼24.1 μg/mm(3) for LAS; 11.3∼22.8 μg/ mm(3) for OP) to the cases light cured using OP. The specimens light cured using LAS showed a significantly higher solubility than the cases light cured using OP (2.4∼6.6 μg/ mm(3) for LAS; 0.8∼1.6 μg/ mm(3) for OP). However, the maximum water sorption and solubility obtained from the specimens were lower than the values permitted by the ISO 4049 standard. The results may suggest that the DPSS laser with an emission wavelength of 473 nm can be used as a light source for light-curing dental resin composites.