Ó 2015 Eur J Oral Sci

Eur J Oral Sci 2015; 123: 208–214 DOI: 10.1111/eos.12178 Printed in Singapore. All rights reserved

European Journal of Oral Sciences

Effects of barriers on chemical and biological properties of two dual resin cements Nocca G, Iori A, Rossini C, Martorana GE, Ciasca G, Arcovito A, Cordaro M, Lupi A, Marigo L. Effects of barriers on chemical and biological properties of two dual resin cements. Eur J Oral Sci 2015; 123: 208–214. © 2015 Eur J Oral Sci The aim of this study was to investigate the degree of conversion, monomer release, and cytotoxicity of two dual-cure resin cements (Cement-One and SmartCem2), light-cured across two indirect restorative materials in an attempt to simulate in vitro the clinical conditions. The results obtained show that the degree of conversion was influenced by both barriers, but the effect of the composite material was greater than that of the ceramic one. The amount of monomers released from the polymerized materials in the absence of barriers was significantly lower than that released in the presence of either the ceramic or the composite barrier. However, a higher amount of monomers was released in the presence of the ceramic barrier. All materials, in all the experimental conditions employed, induced slight cytotoxicity (5–10%) on human pulp cells. Our examinations showed that the two resin cements had similar chemical and biological properties. The decreased degree of conversion of the dual-curing self-adhesive composite showed that the light-curing component of these materials has an important role in the polymerization process. In clinical practice, it is therefore important to pay attention to the thickness of the material used for the reconstruction.

Indirect restorations are commonly used in dental practice because of their esthetic properties, less time-dependent degradation and polymerization shrinkage, and time-saving chairside features (1). However, the application of an indirect restoration manufactured in the dental laboratory still requires direct cementation in the oral cavity. Resin-based luting agents are routinely used for the cementation of indirect restorations or in other clinical applications that require cementation in the oral cavity, and these materials must undergo polymerization via chemical curing, light-curing, or dual-curing (2, 3). Dual-cure materials are formulated to polymerize also in the absence of a visible light source, but, in this case, their degree of conversion (DC) is altered with respect to the manufacturer’s declared information. Indeed, the aim of dual-cure luting cements is to provide an adequate DC beneath restorations where the opacity of the material may hinder the transmission of sufficient light energy to the cement (4, 5). In fact, the energy for the light-curing process decreases during passage through materials because of the ‘light scattering phenomenon’ (5). In such conditions, polymerization of the portion of luting cement that receives insufficient light for the lightcuring process to take place still occurs, via a catalyst that favors the auto-polymerization process (3, 6). This capability is very important in order for an adequate DC

Giuseppina Nocca1,2, Andrea Iori3, Carlo Rossini3, Giuseppe E. Martorana1, Gabriele Ciasca4, Alessandro Arcovito1, Massimo Cordaro3, Alessandro Lupi2, Luca Marigo3 1  di Medicina e Chirurgia, Istituto di Facolta  Biochimica e Biochimica Clinica, Universita Cattolica del Sacro Cuore, Rome; 2Istituto di Chimica del Riconoscimento Molecolare,  di Medicina e C.N.R., Rome; 3Facolta Chirurgia, Istituto di Clinica Odontoiatrica,  Cattolica del Sacro Cuore, Rome; Universita 4  di Medicina e Chirurgia, Istituto di Facolta  Cattolica del Sacro Cuore, Fisica, Universita Rome, Italy

Giuseppina Nocca, Istituto di Biochimica e  di Medicina e Biochimica Clinica, Facolta  Cattolica del Sacro Chirurgia, Universita Cuore, Largo Francesco Vito 1, 00168 Rome, Italy E-mail: [email protected] Key words: conversion degree; cytotoxicity; monomers leachability Accepted for publication January 2015

to be reached from which the mechanical and biological properties of the materials derive. A decrease of the DC could negatively influence the hardness of the resin layer by enhancing the leaching of monomers, with possible toxic effects on pulp cells. The amounts of bioactive molecules released and the degree of cytotoxicity are key parameters in the final evaluation of a biomaterial. In fact, many different harmful components can be leached from composite resins, in particular, uncured dimethacrylic monomers or oligomers that may cause, or at least contribute to, adverse biological effects (7), such as damage to the oral soft tissues, which has already been observed in vivo (8), and a remarkable in vitro cytotoxicity in primary and immortalized cultures (9, 10). Research on biocompatibility of dental materials revealed that different methacrylates were able to induce glutathione depletion (11) and mitochondrial damage with a consequent increase of reactive oxygen species (ROS) production (12, 13). The DC is evaluated most commonly by Fourier transform infrared spectroscopy (FTIR), an analytical technique capable of determining the signal of the unreacted aliphatic C = C double bonds present in a polymerized sample (14). Since mid-2000s, dual-cure cements with improved handling properties have become commercially available.

Evaluation of two dual resin cements

These materials are characterized by a self-adhesive capability that allows them to adhere to tooth structures, which eliminates the necessity of etching and for bonding materials, and thus reduces the time of the procedure (15, 16). Because of their self-adhesive capability, these types of resin cements are usually composed of phosphoric and/or carboxylic acid methacrylate monomers (15). Currently, dual-cure self-adhesive resin cements are used – as thin layers – mainly in luting indirect restorations and in cementation of root posts, bridges, inlays, and onlays, especially in situations in which the light-beam has some difficulties in reaching the material (17). Therefore, the purpose of the present study was to investigate the DC, release of monomers, and cytotoxicity of two dual-cure self-adhesive resin cements. These cements were light cured indirectly across two restorative materials in an attempt to reproduce – in vitro – the clinical conditions, in order to determine the best possible conditions of polymerization, focusing on the light transmission capability of the restorative materials, considering their different chemical nature (ceramic and composite) and their thickness.

Material and methods Preparation of ceramic and composite barriers Two blocks of a Cergo Kiss (Dentsply, York, PA, USA) ceramic material (10 mm 9 10 mm 9 2 mm; 10 mm 9 10 mm 9 4 mm) and two blocks of CeramX

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Duo (Dentsply) composite (10 mm 9 10 mm 9 2 mm; 10 mm 9 10 mm 9 4 mm) were prepared to mimic the restorations that are applied over luting cements. Sample preparation The luting cements Cement-One (Dentalica, Milan, Italy) and SmartCem2 (Dentsply) (described in Table 1) were injected through a syringe, containing the base and the catalyst components, into a stainless-steel mold with a diameter of 6.5 mm and a thickness of 0.6 mm (Fig. 1). A transparent, 0.05-mm-thick polyester strip (HaweNeos Dental, Bioggio, Switzerland) was placed both at the top and at the bottom of the composite materials to avoid oxygen inhibition during polymerization and to prevent direct contact between the cement and the barrier. The samples were divided into three groups: group A, group B, and the control group. In group A, the ceramic barriers (10 mm 9 10 mm 9 2 mm; 10 mm 9 10 mm 9 4 mm) were placed over the specimens; similarly, in group B, the barriers of composite (10 mm 9 10 mm 9 2 mm; 10 mm 9 10 mm 9 4 mm) were placed over the specimens. In the control group, no barrier was placed over the specimens. Materials were then subjected to photo-polymerization using a light-emitting diode (LED) lamp (ART-L3 Curing LightPro with 1,000 mW cm2 light intensity; Bonart, La Puente, CA, USA) according to the manufacturer’s instructions (40 s for SmartCem2 and 20 s for Cement-One). The hardened disks were easily removed from the molds and were used subsequently in the experiments.

Table 1 Manufacturer information for the materials tested in this study Material name

Company

Chemical composition

Composition (vol%)

Lot no.

Cement-One

Dentalica

UDMA TEGDMA Bis-GMA Camphorquinone Ethyl 4-(dimethylamino)benzoate 2,20 -(4-Methylphenylimino)diethanol silicon dioxide Titanium dioxide Barium boron fluoroaluminosilicate glass UDMA EBPADMA Di- and tri-methacrylate resins Phosphoric acid-modified acrylate resin DPP 4-META Camphorquinone Phosphene oxide photoinitiator Accelerators Butylated hydroxy toluene UV stabilizer Barium boron fluoroaluminosilicate glass Organic peroxide initiator Titanium dioxide Iron oxide Hydrophobic amorphous silicon dioxide

32.4 15.6 9 1

PR0062CMO

SmartCem2

Dentsply

1.6 40.0 10035686

46

4-META, 4-methacryloxyethyl trimellitate anhydride; bis-GMA, bisphenyl A glycidyl methacrylate; DPP, dipentaerythritol pentaacrylate phosphate; EBPADMA, Ethoxylated Bisphenol A dimethacrylate; TEGDMA, triethyleneglycol dimethacrylate; UDMA, urethane dimethacrylate.

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Nocca et al. Control A  Sample A  100: Control A Materials were rated as slightly, moderately, or severely cytotoxic when the toxic effects, relative to controls, were 60%, respectively (22). % Cell mortality ¼

Degree of conversion

Fig. 1. Specimen preparation in a stainless steel mold. (A) Composite specimen (0.6 mm high 9 6.5 mm Ø. (B) Stainless steel mold (0.6 mm high). (C) Transparent film. (D) Composite or ceramic block (2 or 4 mm high 9 10 mm long 9 10 mm wide).

Cell culture Unless otherwise specified, all chemicals and reagents used in this study (cell-culture grade) were from Sigma Chemical (Milan, Italy). Human pulp cells (HPCs) were retrieved (with informed consent) from a healthy patient undergoing extraction surgery of the third molars for orthodontic reasons. Tooth surfaces were separated to reveal the pulp chamber; pulp tissues were then harvested, cut into small pieces, digested in a solution of type I collagenase (3 mg ml1) and dispase (4 mg ml1) for 1 h at 37°C, and finally cultured in Dulbecco’s modified Eagle’s medium (DMEM), supplemented with 10% fetal calf serum (FCS), L-glutamine (2 mmol l1), sodium pyruvate (1 mmol l1), penicillin (50 UI ml1), and streptomycin (50 lg ml1), at 37°C in a 5% humidified CO2 atmosphere. Human pulp cells were used between the second and the fifth passages (18, 19). Cytotoxicity To evaluate the cytotoxic effects of the methacrylic monomers released by the materials analyzed in the present study, each specimen was submerged in DMEM (2.0 ml) for 24 h at 37°C. Human pulp cells (1 9 104 cells) in DMEM (0.20 ml) were seeded in individual wells of a 96well tissue culture plate (Costar, Cambridge, MA, USA) and cultured for 24 h until a subconfluent monolayer was achieved. Then, DMEM containing extracts of the disks (0.20 ml; undiluted, and diluted from 50% to 10%) was added to cell monolayers by changing the culture medium, and similar volumes of DMEM only were added to the control wells. After 24 h of incubation, cell viability was evaluated by the MTT test, according to WATAHA et al. (20), as follows: 20 ll of a solution of MTT in PBS (phosphate buffer, 5 mg ml1) was added to the medium (0.20 ml) and, after incubation for 4 h at 37°C, the intracellular formazan crystals produced were solubilized with a solution of HCl in isopropanol (4 9 102 M, 0.20 ml). The absorbance of the solution in each well was determined using an automatic microplate photometer (PackardSpectracount; Packard BioScience, Meriden, CT, USA) at a wavelength of 570 nm. Each experiment was performed in sextuplicate and repeated four times and the cytotoxicity was calculated according to the following equation (21):

The top and bottom surfaces of the disks, prepared as previously described, were analyzed immediately after the polymerization process using a Spectrum One FTIR spectrophotomer (Perkin Elmer, Norwalk, CT, USA) equipped with attenuated total reflection (ATR). All FTIR spectra were recorded under the following conditions: 650– 3,700 cm1 wavenumber range, 16 scans were averaged at a resolution of 4 cm1 resolution. Monomer DC values were determined according to the following equation: % DC ¼ 1 

Am ðcÞ  Aar ðuÞ  100; Am ðuÞ  Aar ðcÞ

where Am is the absorbance area of the signal related to the C = C bond of the methacrylic moiety (1,637 cm1) in the cured (c) or uncured (u) material, and Aar is the signal of the aromatic ring of Bis-GMA (1,609 cm1) in cured (c) and uncured (u) material. (23). Three specimens were used for each ratio of each material. Monomer leaching High-performance liquid chromatography was used to determine the amount of monomers that leached from cured samples. Three specimens were used for each material. Each specimen was prepared as described above, immersed in DMEM (2.0 ml), and incubated for 24 h at 37°C. The media were then centrifuged and filtered (0.45 lm syringe filter; Whatman, Maidstone, Kent, UK). Samples were finally diluted in acetonitrile (1:10, vol/vol; sample/acetonitrile) and analyzed using a JASCO (Easton, MD, USA) HPLC system (2 PU-980 pumps, UV-970 UV/VIS detector and AS-1555 autosampler). The analyses (50 ll injected volume) were performed at a wavelength of 214 nm with a C-18 (5 lm) Supelco reversed-phase column (250 mm 9 4.6 mm) using, as mobile phase (0.7 ml min1), a mixture of water (A) and acetonitrile (B), the gradient elution was: from 40% A to 20% A in 30 min. The triethylene glycol dimethacrylate (TEGDMA) concentration in samples was quantified, before and after each analysis, by comparison with a calibration line created using standard solutions (Sigma Aldrich, Milan, Italy). Optical characterization of barriers The optical properties of the four blocks of ceramic and composite material were investigated using a modified USBrad+XR1 spectrophotometer (Ocean Optics, Ostfilden, Germany). A schematic view of the optical set-up is shown in Fig. 2. The LED lamp (ART-L3 Curing LightPro) is fixed to a micromanipulator and mounted on an optical table. The emitted light passes through a circular 2-mmdiameter aperture and then crosses the sample. The transmitted light is collected by an optical fiber and analyzed by the spectrophotometer. Data from 10 repeated experiments are expressed as the total integrated intensity in the 460–470 nm wavelength range.

Evaluation of two dual resin cements polymerizaon lamp holder

sample

Opcal Fiber

Ocean spectrometer

Fig. 2. Schematic view of the optical set-up. The light-emitting diode (LED) lamp is fixed to a micromanipulator and mounted on an optical table. The emitted light first passes through a circular 2-mm-diameter aperture and then through the sample. The transmitted light is collected by an optical fiber and analyzed by spectrometry.

Statistical analysis

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of barrier thickness, being dependent only on the type of material (Fig. 3 and Table 3). The disks of group B released a smaller amount of TEGDMA than those of group A (P < 0.01); however, the concentration of TEGDMA released from both groups remained at subcytotoxic levels (24, 25). Regarding SmartCem2, it was not possible to identify any HPLC signals; even using the area under the curve (AUC) analysis of a chromatographic signal revealed at 8 min retention time, we deduced that there were no differences in the amount of component released from the specimens cured in the presence of different barriers (Fig. 4). Degree of conversion

Each result represents the mean of (at least) three experiments performed in sextuplicate. All results are expressed as mean  SD. The group means were compared by ANOVA followed by a multiple comparison of means using the Student–Newman–Keuls method. If necessary, comparison using the Student’s t-test was used: P < 0.05 was considered significant.

Results Cytotoxicity

Under the experimental conditions of our study, the cytotoxic effect induced by all materials tested was slight (5–10%). No statistical differences in cell mortality were observed among the study groups (Table 2). Monomer leaching

Specimens were analyzed by HPLC to evaluate monomer leaching. The results showed that for both Cement-One and SmartCem2, the amount of monomers released from the material cured in the absence of any physical barrier (control group) was significantly lower than the amount released from the samples polymerized in the presence of barriers (groups A and B) (Figs 3 and 4). TEGDMA (retention time 7 min) was detected in eluates derived from Cement-One samples; however, no cytotoxic effect was observed at any concentration of TEGDMA. The quantity of TEGDMA released by Cement-One disks did not increase with enhancement

The DC obtained for the top surfaces of both materials in the absence of any physical barrier (control group) was significantly higher than the DC obtained in the presence of a barrier (groups A and B) (Table 4). When bottom surfaces were considered, a different effect was found for ceramic barrier (group A) (2 mm thickness, only) compared with composite barrier (group B), in that the latter reduced the DC in both Cement-One and SmartCem2 samples (Table 4). There was no statistical difference in the DC of SmartCem2 and Cement-One when the same polymerization conditions were used (Table 5). Optical characterization of ceramic and composite barriers

In Fig. 5, the light transmitted through the barriers, expressed as the total integrated intensity in the 460– 470 nm wavelength range, is shown. As expected from the Lambert–Beer law, the intensity of the transmitted light decreases with increasing sample thickness. The two blocks of composite material showed a higher intensity of transmitted light with respect to the ceramic barriers of the same thickness (P < 0.001).

Discussion The aim of using dual-cured resin cements is to combine chemical polymerization with photo-polymerization in order to obtain a material with adequate physical and chemical properties able to polymerize under conditions

Table 2 Cytotoxicity on human pulpar cells (HPCs) of components eluted in each group Group A Luting cement

Control group

Cement-One SmartCem2

0.0 0.0

Group B

2 mm

4 mm

2 mm

4 mm

0.9  1.9 2.3  4.9

2.3  5.8 0.4  1.3

4.7  7.1 0.9  3.0

3.3  5.7 8.0  13.7

Values represent mean percentage cell mortality  SD, obtained from four independent experiments. No significant differences in cell mortality were observed between groups A and B compared with the control group, after 24 h of incubation with eluate. Group A, ceramic barriers were placed over specimens; group B, composite barriers were placed over the specimens; control group, no barrier was placed over the specimens. Two and 4 mm indicate the depth of the barrier used in groups A and B.

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Nocca et al. Table 3 Statistical analysis of amount of TEGDMA released from CO disks polymerized in presence or in absence of barriers P value

Fig. 3. Analysis of eluates derived from Cement-One disks. High-performance liquid chromatography (HPLC) identified triethyleneglycol dimethacrylate (TEGDMA) in eluates derived from Cement-One disks. The TEGDMA concentration was quantified from calibration curves created using standard solutions before each analysis. Bars represent mean values  SD from three repeated experiments. Group A, ceramic barriers were placed over the specimens; group B, composite barriers were placed over the specimens; control group, no barrier was placed over the specimens. The values 2 and 4 mm indicate the depth of the barrier used. *P < 0.05; **P < 0.01; ***P < 0.001; significantly different from the control group.

Fig. 4. High-performance liquid chromatography (HPLC) analysis of eluates derived from SmartCem2 disks. Bars represent mean values of area under the curve (AUC)  SD from three repeated experiments. Group A, ceramic barriers were placed over specimens; group B, composite barriers were placed over the specimens; control group, no barrier was placed over the specimens. The values 2 and 4 mm indicate the depth of the barrier used. *P < 0.05; **P < 0.01; significantly different from the control group.

of suboptimal light irradiation, as in deeper sites or under thicker restorations (26). It has been demonstrated that insufficient polymerization of resin-based luting cement results in a significant decrease in mechanical properties (2). Therefore, adequate polymerization of the luting agent is essential to ensure the longevity and biocompatibility of the restoration (27). The polymerization of a resin-based material depends on, and can be affected by, many factors, such as the monomer formulation of the materials or the intensity of irradiation afforded by the light source (28). Thus, this in vitro study measured the degree of conversion, the monomers release, and the cytotoxicity of a thin layer of two dual-cured self-adhesive resin

Control Group 0.018  0.002 Control Group 0.018  0.002 Control Group 0.018  0.002 Control Group 0.018  0.002 Group A (2 mm) 0.33  0.03 Group A (4 mm) 0.42  0.035 Group A (2 mm) 0.33  0.03 Group B (2 mm) 0.18  0.02

vs vs vs vs vs vs vs vs

Group A (2 mm) 0.33  0.03 Group A (4 mm) 0.42  0.035 Group B (2 mm) 0.18  0.02 Group B (4 mm) 0.19  0.02 Group B (2 mm) 0.18  0.02 Group B (4 mm) 0.19  0.02 Group A (4 mm) 0.42  0.035 Group B (4 mm) 0.19  0.02

** *** * * NS NS NS NS

Each value represents the mean  SD from three repeated experiments. TEGDMA concentration was quantified from calibration curves created using standard solutions before each analysis. Group A, ceramic barriers were placed over specimens; group B, composite barriers were placed over the specimens; control group, no barrier was placed over the specimens. Two and 4 mm indicate the depth of the barrier used in groups A and B. NS, non-significant. *P < 0.05; **P < 0.01; ***P < 0.001.

cements polymerized beneath a 2- or a 4-mm-thick barrier made of ceramic or composite materials to simulate clinical conditions. The behavior of the two materials was similar in the absence of the barriers: in fact, both cytotoxicity and release of monomers were lower than those found after curing across composite or ceramic barriers, whereas DC values were significantly higher in respect to those obtained in the presence of barriers. These data are in strong agreement with the literature (29) and depend both on the decrease of light intensity – when the distance between the lamp and cements increases – and on the interaction between the light and the barriers (lightscattering phenomenon) (5). Regarding DC analysis, the only exception to the above-reported results concerned the values obtained in the bottom surfaces polymerized under the ceramic barrier of 2 mm; under these experimental conditions, neither SmartCem2 nor Cement-One showed significant differences compared with the control. This outcome is unexpected considering that light is transmitted with lower efficiency across Cergo Kiss (ceramic barrier) than CeramX Duo (composite). Nevertheless, when monomer leachability is considered, Cement-One released – as expected – a higher amount of TEGDMA monomers when the polymerization occurred under ceramic barriers (Cergo Kiss) compared with composite barriers (CeramX Duo). The imperfect concordance of the data obtained following HPLC with those from FTIR measurements could be ascribed to the different sensitivity of the two analyti-

Evaluation of two dual resin cements

213

Table 4 Degree of conversion of disks Cement-One Group

Top surfaces

Control group Group A 2 mm Group A 4 mm Group B 2 mm Group B 4 mm

SmartCem2 Bottom surfaces

Top surfaces

Bottom surfaces

57.34  1.79 47.58  1.72**

58.20  1.74 53.49  1.20

55.51  2.11 40.32  6.80*

58.63  1.77 56.82  2.30

36.66  4.14***

42.00  5.23***

37.22  9.71**

38.92  12.22**

43.20  2.31**

43.08  1.86***

42.80  1.95**

43.75  2.91***

29.35  5.27***

29.10  3.3***

32.96  3.00***

42.37  5.07**

Values represent mean  SD from three repeated experiments. Group A, ceramic barriers were placed over specimens; group B, composite barriers were placed over the specimens; control group, no barrier was placed over the specimens. Two and 4 mm indicate the depth of the barrier used. *P < 0.05; **P < 0.01; ***P < 0.001, significantly different from the control group.

Table 5 Statistical analysis of degree of conversion (DC) values of Cement-One (CO) and SmartCem2 (SC) in the presence of barriers Group Group Group Group Group

A (2 mm) B (2 mm) A (4 mm) B (4 mm)

CO top vs. SC top

CO bottom vs. SC bottom

NS NS NS NS

NS NS NS NS

NS, non-significant. Group A, ceramic barriers were placed over specimens; group B, composite barriers were placed over the specimens; control group, no barrier was placed over the specimens. Two and 4 mm indicate the depth of the barrier used.

Fig. 5. Total integrated intensity transmitted through the sample in the range 460–470 nm. Bars represent mean values of area under the curve (AUC)  SD, from 10 repeated experiments. Group A, ceramic barriers were placed over specimens; group B, composite barriers were placed over the specimens; 2 and 4 mm indicate the depth of the barrier used. ***P < 0.001.

cal techniques and also to the fact that unpolymerized monomers may remain trapped in the polymeric network and not be released into the surrounding

medium. Therefore, the highest DC values may not always coincide with release of the lowest amounts of monomers. It is, in fact, possible to evaluate, through FTIR, the total amount of groups that have not reacted during the polymerization reaction, whereas HPLC analysis determines the amount of completely free dimethacrylate monomers released into the medium (30). Moreover, the HPLC technique analyzes simultaneously the compounds released from both the top and the bottom surfaces of each specimen; in contrast, FTIR analyzes the two surfaces separately. For all these reasons, the differences obtained with the two different analytical techniques are not surprising. The results on cytotoxicity showed that both cements had a slightly cytotoxic effect (5–10%) under all the experimental conditions. Cytotoxicity depends on exposure time, differences between cell lines in resistance to toxicity, cell–material contact, and biological target used to determine the cytotoxic effect (31); thus, it is not always possible to compare the results reported in the literature between different papers. In this study, human primary pulp cells were used because they are more representative models with respect to immortalized cell lines, and cytotoxicity was determined using the MTT assay (a well-known and largely consolidated test) (10). The results demonstrated that, despite the reduction of DC values and the increase of toxic substances released into the culture medium, the concentration reached by them – even in the presence of a poor light irradiation – always remained at subcytotoxic levels (24, 25). Lastly, the major clinical consideration that could be inferred from our data is that both barriers provoked similar alterations in both cements (regardless of their different chemical nature) without any significant change in cytotoxicity. Acknowledgements – The authors wish to thank the Universita Cattolica of Rome to the financial support. Conflicts of interest – The authors deny any conflicts of interest.

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References 1. LUTZ F, KREJCI I. Amalgam substitutes: a critical analysis. J Esthet Restor Dent 2000; 12: 146–159. 2. TEZVERGIL-MUTLUAY A, LASSILA LVJ, VALLITTU PK. Degree of conversion of dual-cure luting resins light-polymerized through various materials. Acta Odontol Scand 2007; 65: 201–205. 3. SHEN C. Dental cements. In: ANUSAVICE KJ, ed. Philips’ science of dental materials, 11th edn. San Francisco, CA: Saunders, 2003; 486–488. 4. MYERS ML, CAUGHMAN WF, RUEGGEBERG FA. Effect of restoration composition, shade, and thickness on the cure of a photoactivated resin cement. J Prosthodont 1994; 3: 149–157. 5. ACQUAVIVA PA, CERUTTI F, ADAMI G, GAGLIANI M, FERRARI M, GHERLONE E, CERUTTI A. Degree of conversion of three composite materials employed in the adhesive cementation of indirect restorations: a micro-Raman analysis. J Dent 2009; 37: 610–615. 6. PEUTZFELDT A. Dual-cure resin cements: in vitro wear and effect of quantity of remaining double bonds, filler volume, and light curing. Acta Odontol Scand 1995; 53: 29–34. 7. GEURTSEN W, LEHMANN F, SPAHL W, LEYHAUSEN G. Cytotoxicity of 35 dental resin composite monomers/additives in permanent 3T3 and three human primary fibroblast cultures. J Biomed Mater Res 1998; 41: 474–480. 8. GEURTSEN W. Biocompatibility of resin-modified filling materials. Crit Rev Oral Biol Med 2000; 11: 333–355. 9. BOUILLAGUET S, VIRGILLITO M, WATAHA J, CIUCCHI B, HOLZ J. The influence of dentine permeability on cytotoxicity of four dentine bonding systems, in vitro. J Oral Rehabil 1998; 25: 45–51. 10. BOUILLAGUET S, WATAHA JC, HANKS CT, CIUCCHI B, HOLZ J. In vitro cytotoxicity and dentin permeability of HEMA. J Endod 1996; 22: 244–248. 11. NOCCA G, RAGNO R, CARBONE V, MARTORANA GE, ROSSETTI DV, GAMBARINI G, GIARDINA B, LUPI A. Identification of glutathione-methacrylates adducts in gingival fibroblasts and erythrocytes by HPLC-MS and capillary electrophoresis. Dent Mater 2011; 27: e87–e98. 12. NOCCA G, DE PALMA F, MINUCCI A, DE SOLE P, MARTORANA GE, CALLA C, MORLACCHI C, GOZZO ML, GAMBARINI G, CHIMENTI C, GIARDINA B, LUPI A. Alterations of energy metabolism and metabolism and glutathione levels of HL-60 cells induced by methacrylates present in composite resins. J Dent 2007; 35: 187–194. 13. NOCCA G, MARTORANA GE, DE SOLE P, DE PALMA F, CALLA C, CORSALE P, ANTENUCCI M, GAMBARINI G, CHIMENTI C, GIARDINA B, LUPI A. Effects of 1,4-butanediol dimethacrylate and urethane dimethacrylate on HL-60 cell metabolism. Eur J Oral Sci 2009; 117: 175–181. 14. GALVAO MR, CALDAS SG, BAGNATO VS, DE SOUZA RASTELLI AN, DE ANDRADE MF. Evaluation of degree of conversion and hardness of dental composites photoactivated with different light guide tips. Eur J Dent 2013; 7: 86–93. 15. ILIE N, SIMON A. Effect of curing mode on the micro-mechanical properties of dual-cured self-adhesive resin cements. Clin Oral Invest 2012; 16: 505–512.

16. SENSAT ML, BRACKETT WW, MEINBERG TA, BEATTY MW. Clinical evaluation of two adhesive composite cements for the suppression of dentinal cold sensitivity. J Prosthet Dent 2002; 88: 50–53. 17. MORAES RR, BOSCATO N, JARDIM PS, SCHNEIDER LF. Dual and self-curing potential of self-adhesive resin cements as thin films. Oper Dent 2011; 36: 635–642. 18. CHANG HH, CHANG MC, HUANG GF, WANG YL, CHAN CP, WANG TM, LIN PS, JENG JH. Effect of triethylene glycol dimethacrylate on the cytotoxicity, cyclooxygenase-2 expression and prostanoids production in human dental pulp cells. Int Endod J 2012; 45: 848–858. 19. CHANG MC, CHEN YJ, TAI TF, TAI MR, LI MY, TSAI YL, LAN WH, WAN YL, JENG JM. Cytokine-induced prostaglandin E2 production and cyclooxygenase-2 expression in dental pulp cells: downstream calcium signaling via activation of prostaglandin EP receptor. Int Endod J 2006; 39: 819–826. 20. WATAHA JC, CRAIG RG, HANKS CT. Precision of new methods for testing in vitro alloy cytotoxicity. Dent Mater 1992; 8: 65–70. 21. HASHIEH IA, COSSET A, FRANQUIN JC, CAMPS J. In vitro cytotoxicity of one-step dentin bonding systems. J Endod 1999; 25: 89–92. 22. SLETTEN GB, DAHL JE. Cytotoxic effects of extracts of compomers. Acta Odontol Scand 1999; 57: 316–322. 23. AMIROUCHE-KORICHI A, MOUZALI M, WATTS DC. Effects of monomer ratios and highly radiopaque fillers on degree of conversion and shrinkage-strain of dental resin composites. Dent Mater 2009; 25: 1411–1418. 24. TESTARELLI L, NOCCA G, LUPI A, PACIFICI L, POMPA G, ROMEO U, GAMBARINI G. Biocompatibility of root canal filling materials: differences between vitality and functionality tests. Eur J Inflamm 2012; 10: 105–110. 25. NOCCA G, CALLA C, MARTORANA GE, CICILLINI L, RENGO S, LUPI A, CORDARO M, GOZZO ML, SPAGNUOLO G. Effects of dental methacrylates on oxygen consumption and redox status of human pulp cells. Biomed Res Int 2014; 2014: Article ID 956579. 26. MENG X, YOSHIDA K, ATSUTA M. Influence of ceramic thickness on mechanical properties and polymer structure of dualcured resin luting agents. Dent Mater 2008; 24: 594–599. 27. PAMEIJER CH. A review of luting agents. Int J Dent 2012; 2012: Article ID 752861. 28. RUEGGEBERG FA, CAUGHMAN WF. The influence of light exposure on polymerization of dual-cure resin cements. Oper Dent 1993; 18: 48–55. 29. CIUCCHI B, BOUILLAGUET S, DELALOYE M, HOLTZ J. Volume of the internal gap formed under composite restorations in vitro. J Dent 1997; 25: 305–312. 30. TARUMI H, IMAZATO S, EHARA A, KATO S, EBI N, EBISU S. Post-irradiation polymerization of composites containing bisGMA and TEGDMA. Dent Mater 1999; 15: 238–242. 31. SCHMALZ G. Use of cell cultures for toxicity testing of dental materials-advantages and limitations. J Dent 1994; 22(Suppl 2): S6–S11.

Effects of barriers on chemical and biological properties of two dual resin cements.

The aim of this study was to investigate the degree of conversion, monomer release, and cytotoxicity of two dual-cure resin cements (Cement-One and Sm...
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