Replacing HEMA with Alternative Dimethacrylates in Dental Adhesive Systems: Evaluation of Polymerization Kinetics and Physicochemical Properties Eliseu Aldrighi Münchowa / Cesar Henrique Zanchib / Fabrício Aulo Ogliaric / Manuela Gonçalves Souza e Silvaa / Isadora Rubin de Oliveirad / Evandro Pivab Purpose: To evaluate the mechanical and physical properties of experimental HEMA-containing and HEMA-free resin adhesives. Materials and Methods: Experimental HEMA-free adhesives containing alternative dimethacrylates (bis-EMA 10 [B10], bis-EMA 30 [B30], PEG 400 [P400], PEG 1000 [P1000], PEG 400 UDMA [UP400]) were formulated and compared with a HEMA-containing adhesive (control). The adhesives were characterized by rheological analysis, polymerization kinetics (PK), water sorption (WS), and solubility (SL) tests. Flexural strength (FS) and flexural modulus (E) tests were performed under dry or wet conditions (distilled water or 70% ethanol solution). One-way and two-way ANOVA as well as Tukey’s test were used to evaluate differences between groups (p < 0.05). Results: The control group showed the lowest viscosity and was the only one with a degree of conversion lower than 50%. The control and the P1000 adhesive showed the statistically significantly highest WS (p < 0.05). The control and the UP400 adhesive showed the highest FS and E, and the dry-stored specimens showed more improved mechanical strength than did the wet-stored specimens (p < 0.05). Conclusion: The physicomechanical properties of some of the HEMA-free adhesives were substantially improved when compared with those of the control, indicating that they could be potential monomers for the development of HEMA-free adhesive systems. Keywords: dental adhesives, HEMA, hydrophilicity, cross linking, FTIR, mechanical properties. J Adhes Dent 2014; 16: 221–227. doi: 10.3290/j.jad.a31811

T

he monomer 2-hydroxyethyl methacrylate (HEMA) is extensively present in dental adhesive systems. It is an excellent adhesion-promoting agent, participating as co-solvent and allowing a homogeneous mixture of hydrophobic and hydrophilic monomers.15,29 However, HEMA presents some biological concerns, such as cytotoxicity and allergenic potential,10,20-21 as well as the ability to penetrate through conventional gloves,2

a

PhD Student, Operative Dentistry Department, School of Dentistry, Federal University of Pelotas, RS, Brazil. Performed experiments, wrote and proofread manuscript.

b

Assistant Professor, Operative Dentistry Department, School of Dentistry, Federal University of Pelotas, RS, Brazil. Wrote manuscript, performed statistical evaluation.

c

Assistant Professor, Polymeric Materials Department, Materials Engineering School, Federal University of Pelotas, RS, Brazil. Study idea, supervised experiments.

d

PhD student, Biotechnology Department, Technical Development Center (CDTec), Federal University of Pelotas, RS, Brazil. Performed experiments.

Correspondence: E. Piva, Rua Gonçalves Chaves, 457 – Developmental and Controlling Center of Biomaterials (CDC-Bio), Pelotas, RS, Brazil 96015-560. Tel: +55-53-3222-6690. e-mail: [email protected]

Vol 16, No 3, 2014

Submitted for publication: 25.02.13; accepted for publication: 25.09.13

leading to the development of contact dermatitis in dental professionals.30 Furthermore, its high hydrophilicity intensifies the hydrolysis of the polymer network by enhancing the hygroscopic and hydrolytic phenomena of degradation.7,11,28 Consequently, HEMA-free dental adhesives began to be developed in an attempt to improve their physical, chemical and mechanical characteristics. The replacement of HEMA (mono-functional) with dimethacrylates would be important because the latter present two polymerizable extremities capable of forming cross-linked polymers, which are less susceptible to hydrolysis,7,26 improving the stability of the material during contact with the oral environment.8 In view of the above considerations, there are several types of dimethacrylates available for this purpose, as has been stated by two recent studies that developed five experimental HEMA-free adhesive systems with good adhesive characteristics.33,34 In fact, the latter studies demonstrated satisfactory immediate and long-term microtensile bond strength to dentin using dimethacrylate monomers instead of HEMA. Thus, considering the possible advantages of replacing HEMA with alternative dimethacrylates, the objective of this study was to test the hypothesis that 221

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Table 1 Alternative monomers used in this study and their molecular weight (MW), formula (MF) and structure (MS) (information provided by the supplier) Alternative monomer (respective group)

MW (g/mol)

MF

PEG 400 (P400)

550-594

C26-28 H46-50 O12-13

PEG 1000 (P1000)

1124-1168

C52-54 H98-102 O25-26

Bis-EMA 10 (B10)

805

C43H64O14

MS

n+m=10 Bis-EMA 30 (B30)

1686

C83H144O34

n+m=30 PEG 400 UDMA (UP400)

1139

C54H98N4O21 (x=1)

HEMA (AH) control

130

C6H10O3

PEG 400: polyethyleneglycol (400) dimethacrylate; PEG 1000: polyethyleneglycol (1000) dimethacrylate; bis-EMA 10: ethoxylated bisphenol A diglycidyl ether dimethacrylate with 10 ethylene oxide units; bis-EMA 30: ethoxylated bisphenol A diglycidyl ether dimethacrylate with 30 ethylene oxide units; PEG 400 UDMA: polyethyleneglycol (400) extended urethane dimethacrylate; HEMA: 2-hydroxiethyl methacrylate; bis-GMA: 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropyl) phenyl]-propane.

experimental HEMA-free resin adhesives containing alternative dimethacrylates would present improved mechanical and physical properties when compared with a HEMAcontaining adhesive.

MATERIALS AND METHODS

eneglycol (400) extended urethane dimethacrylate (PEG 400 UDMA); and AH: HEMA (control). The monomers were purchased from Esstech (Essington, PA, USA) and used as received. Quantities of 0.4 wt% of camphorquinone (CQ, Esstech) and 0.8 wt% of ethyl 4-dimethylaminebenzoate (EDAB, Fluka; Milwalkee, WI, USA) were dissolved in the mixtures and ultrasonicated for 15 min.

Adhesive Formulations Six experimental resin adhesives were formulated by mixing 50 wt% of 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropyl)phenyl]-propane (bis-GMA), 25 wt% of triethyleneglycol dimethacrylate (TEG-DMA), and 25 wt% of a variable monomer (Table 1), as follows: B10 and B30: ethoxylated bisphenol A diglycidyl dimethacrylate, with 10 and 30 ethylene oxide units (bis-EMA 10 and bisEMA 30, respectively); P400: polyethyleneglycol (400) dimethacrylate (PEG 400); P1000: polyethyleneglycol (1000) dimethacrylate (PEG 1000); UP400: polyethyl-

Rheological Analysis All monomers and their respective adhesives were evaluated in a viscometer (Brookfield, model DV-II+Pro; Middleboro, MA, USA) with a SC4-18 spindle. Six milliliters of each sample were introduced into the adapter and coupled to the spindle, then accelerated from 0 to 15 rpm at 20°C and recorded in triplicate. The viscometer was unable to obtain data from bis-GMA and PEG 1000, since they exceeded the measuring capacity of the spindle. A rheogram of shear stress x shear rate was generated using the Rheocalc software program (Brookfield).

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Table 2 Water sorption (WS) and solubility (SL), standard deviation (SD), degree of conversion (DC) and viscosity of the alternative monomers (VAM) and of the resin adhesives (VRA) evaluated in this study Resin adhesives

WS (g/mm3)

SL (μg/mm3)

DC (%) (at 20 s)

VAM (mPa s)

VRA (mPa s)

P400

69.5 (1.2)C

7.1 (3.1)A

53.5 (3.2)AB

49.1

484.2E

P1000

89.4 (2.2)A

1.8 (1.6)B

49.9 (3.0)B

-

817.5D

B10

51.4 (2.8)E

-0.4 (1.2)B

53.5 (4.1)AB

567.5

1037.1C

B30

79.4 (2.4)B

1.2 (0.7)B

57.9 (3.5)A

821.3

1490.4B

UP400

59.3 (2.7)D

0.4 (2.0)B

49.5 (3.7)B

6878

1671.8A

AH

85.9 (3.1)A

4.3 (2.4)AB

35.9 (3.8)C

14.9

171.9F

TEG-DMA viscosity = 15.8 mPa s. Different superscript capital letters in the same column represent statistical differences between the resin adhesive groups (p < 0.001).

Polymerization Reaction Analysis The polymerization kinetics (PK) and degree of conversion (DC) were evaluated in quintuplicate using real-time Fourier transform infrared spectroscopy (RT-FTIR) with a Prestige-21 spectrometer (Shimadzu; Columbia, MD, USA) equipped with an attenuated total reflectance device, composed of a horizontal zinc selenide crystal. The IRsolution software program (Shimadzu; Columbia, MD, USA) was used in monitoring scan mode with the Happ-Genzel appodization, within the range of 1750 to 1550 cm-1, at a resolution of 8 cm-1 and mirror speed of 2.8 mm/s. One scan per second was acquired during photoactivation (60 s) with an LED light-curing unit (Radii, SDI; Bayswater, VIC, Australia) emitting an irradiance of 900 mW/cm2, at a controlled room temperature of 23ºC (±2ºC) and 60% (±5%) relative humidity. The DC was calculated as previously described;17 the data were plotted and curve fitting performed by non-linear regression (Hill plots). The rate of polymerization was calculated as the DC at time t subtracted from DC at time t - 1.16 The coefficient of determination was greater than 0.98 for all curves. Water Sorption and Solubility Seven disk-shaped specimens (6 x 1 mm)12 were prepared and photoactivated with the LED unit for 40 s on both top and bottom surfaces. Then, specimens were placed in a desiccator containing freshly dried silica gel and calcium chloride. After 24 h, they were removed, stored in a desiccator at 23ºC for 1 h, and weighed on a precision balance with 0.01 mg accuracy (AUW 220D, Shimadzu; Kyoto, Japan). This cycle was repeated until a constant mass (m1) was obtained. Thickness and diameter were randomly measured to calculate the specimen volume (V) (in mm3). The specimens were immersed in distilled water at 37ºC for 7 days, then removed, blotted dry, and weighed (m2). The weight of each specimen was recorded. After that, the specimens were dried inside the desiccators and the weight was recorded daily in order to obtain a third constant mass (m3), as previously described. For each sample, the data of water sorption (WS) and solubility (SL) were calculated using the following formulae: Vol 16, No 3, 2014

WS =

(m2-m3) V

and

SL = (m1-m3) V

Flexural Strength and Modulus Thirty bar-shaped specimens (12 x 2 x 2 mm) were prepared and photoactivated with the LED unit for 40 s on both top and bottom surfaces and at two adjacent points. The specimens were randomly allocated to three groups according to the storage method: dry for 24 h, 7 days in distilled water, or 7 days in 70% ethanol solution at 37ºC. All the specimens were submitted to the three-point bending test in a universal testing machine (DL-500, Emic; São José dos Pinhais, Brazil) at a crosshead speed of 1 mm/ min. Flexural strength (FS) was calculated in MPa and flexural modulus (E) in GPa using the following formulae: FS =

3Fl (2bh2)

and

E=

F1l3 4bh3d

where F is the peak load (N), l is the span length (mm), b is the width of the specimen (mm), h is the thickness of the specimen (mm), and d is the deflection of the specimen at load F1 during the straight line portion of the load-displacement curve. Statistical Analysis Data of the adhesive viscosities, DC, WS, SL, and the FS and E dry-storage tests were analyzed using one-way ANOVA, and data of FS and E tests after wet storage were analyzed using two-way ANOVA (adhesive and solution factors); for both, Tukey’s post-hoc test was used (p < 0.05).

RESULTS Rheological Behavior The viscosities of the experimental resin adhesives ranged from 171.9 mPa s (control) to 1671.8 mPa s, where UP400 > B30 > B10 > P1000 > P400 > AH (p < 0.001) (Table 2). Figure 1 shows the adhesive rheogram of shear stress x shear rate, which demonstrated Newtonian behavior. 223

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Polymerization Reaction Figure 2 shows the kinetics and rate of polymerization data. The DC of adhesives ranged from 35.9% (AH) to 57.9% (B30) after 20 s of light activation (Fig 2a). B30, B10, and P400, which showed similar DC values (p>0.05), demonstrated higher conversion than the control (p < 0.001) (Table 2). The HEMA-free adhesives presented an improved, faster polymerization reaction than the control (Fig 2b).

350 B10 B30 AH P400 P1000 UP400

300

Shear stress (Pa)

250 200 150 100 50 0 0

5

10

15

20

Shear rate (1/s) Fig 1 Shear stress x shear rate of the experimental adhesives.

70

Degree of conversion (%)

60 50 40 30

B10 B30 AH P400 P1000 UP400

20 10 0

0

10

20

30

40

50

60

Water Sorption and Solubility Table 2 shows the water sorption (WS) and solubility (SL) data. P1000 and AH adhesives presented higher WS than the others and B10 showed the lowest WS (p < 0.001). With regard to SL, P400 and AH had higher values than P1000, B30, B10, and UP400 (p < 0.001), which presented similar SL to each other (p > 0.05). Flexural Strength and Modulus The dried specimens were not statistically compared with the wet ones because the storage period between these two conditions differed. AH and UP400 presented similar FS in dry storage and had higher FS values than the others; P1000 and B30 showed the lowest FS values. After wet storage, the specimens immersed in distilled water showed higher FS than those immersed in ethanol, whereas within the water storage, FS results were B10 = UP400 > AH = P400 > B30 = P1000, and within the ethanol storage, B10 = UP400 = P400 > AH = P1000 = B30 (Table 3). As regards the flexural modulus (E) data, the control showed the highest value, followed by UP400 > B10 ≥ P400 = P1000 ≥ B30. In the wet storage group, all the adhesives immersed in water showed a higher E value than those immersed in ethanol, but within the water storage group, AH = UP400 ≥ B 10 > P400 > B30 = P1000, and within the ethanol storage group, P400 = B10 = UP400 > AH ≥ P1000 = B30.

Times (s)

a

DISCUSSION Rate of polymerization (Rp%.s)

20 B10 B30 AH P400 P1000 UP400

15

10

5

0 0

b

5

10

15

20

Times (s)

Fig 2 Polymerization kinetics (a) and rate of polymerization (b) of the experimental resin adhesives after 60 s of photoactivation.

224

Considering that dimethacrylates are longer molecules than HEMA, a rheological analysis was performed in an attempt to identify the viscosity achieved with each monomer and adhesive tested. As expected, the alternative dimethacrylates were more viscous than HEMA (Table 2) and they resulted in materials showing Newtonian behavior, which means that their viscosity is proportionally affected by the shear stress and the shear rate applied to the material (Fig 1).4,24 Moreover, a material’s viscosity is directly influenced by its intermolecular forces;23 therefore, considering that bis-GMA has two pendant hydroxyl groups (strong hydrogen bonding) in its molecular structure, and that PEG 1000 is a waxy solid at room temperature, these two monomers could not be measured. Nevertheless, their mixture with a less viscous monomer (eg, TEG-DMA) allowed rheological analysis of the adhesives. Furthermore, all the HEMA-free adhesives evaluated were more viscous than the HEMA-containing one, with The Journal of Adhesive Dentistry

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Table 3 Flexural strength (FS) and Young’s modulus (E) mean and standard deviations (SD) of the experimental resin adhesives after dry or wet storage Mechanical property FS

E

Type of storage

Resin adhesives P400 (10.5)BC

P1000 85.5

(7.3)C

B10 97.8

(2.8)B

B30 84.7

(6.6)C

UP400 110.9

AH

(13.9)A

111.3 (8.0)A

Dry 24 h

95.0

Distilled water

59.2 (11.5)aB

38.8 (5.6)aC

72.8 (4.3)aA

39.6 (6.4)aC

70.6 (12.2)aA

61.6 (7.7)aB

Ethanol solution

35.8 (5.2)bA

18.4 (3.6)bB

40.9 (1.9)bA

18.1 (3.6)bB

36.3 (3.3)bA

21.6 (2.9)bB

Dry 24 h

9.9 (1.9)CD

9.6 (1.6)CD

10.1 (0.6)C

8.3 (0.8)D

11.5 (1.5)B

13.5 (1.4)A

Distilled water

6.6 (0.6)aC

3.9 (0.7)aD

7.3 (0.7)aB

4.2 (0.3)aD

7.7 (0.3)aAB

7.9 (0.8)aA

Ethanol solution

3.5 (0.4)bA

1.7 (0.3)bBC

3.4 (0.2)bA

1.3 (0.1)bC

3.2 (0.2)bA

2.0 (0.3)bB

The statistical differences between groups stored dry for 24 h are represented by different superscript capital letters in the same row (p < 0.001). Differences between groups immersed for 7 days in distilled water or 70% ethanol solution are indicated by superscript uppercase letters (differences between resin adhesives in the same row) and superscript lowercase letters (differences among storage solutions in the same column) (p < 0.001).

UP400 showing a viscosity almost 10 times higher than the control (Table 2). Considering this, it could be expected that the HEMA-free adhesives would not hybridize the dentin effectively;19 nevertheless, two recent studies using a similar formulation demonstrated that those adhesives were effective as adhesion-promoting agents.32,34 In addition, a higher viscosity has been related to a higher rate of polymerization and higher monomer conversion, probably due to the decrease in polymer chain termination and the reduction in mobility of the polymer radicals in viscous situations, thereby increasing the free-radical propagation (Trommsdorff effect).19,25 Moreover, the Trommsdorf effect is associated with the increase in temperature in some polymer systems, which may also affect the polymerization kinetics of the material.27 The degree of conversion (DC) is directly related to better physicochemical stability7 and mechanical properties of polymers,25 thus an effective polymerization reaction is essential.13 With regard to the polymerization reaction, the HEMA-free adhesives presented DC values higher than or close to 50% at 20 s of photoactivation, whereas the control presented a mean DC of 35.9% (Table 2). In a chemical analysis, the only difference between these adhesives was the type of the variable monomer (monofunctional or dimethacrylates), causing the differences in reactivity achieved in the present study,19 although under certain conditions, monomethacrylated monomers can present reactivity similar to dimethacrylated monomers.1 Dimethacrylates present two unsaturations when compared with HEMA, and this characteristic might have allowed them to form a crosslinked network system, which may have especially increased the conversion of monomers.18,22 According to Fig 2a, B30 showed the highest DC. Nevertheless, P1000 and UP400 adhesives showed lower DC than B30 (Table 2), probably because they were very reactive, showing an improved rate of polymerization over the other adhesives (Fig 2b). A high rate of polymerization is related to an auto-acceleration of the polymerVol 16, No 3, 2014

ization reaction, and if this only occurs at the beginning of the reaction, less conversion could be expected before gelation and vitrification of the polymer, causing the decrease in the monomer mobility,18 and consequently, a limited degree of conversion (around 50% for P1000 and UP400). In this study, the control presented the lowest DC and rate of polymerization of this study (Fig 2), confirming that the mono-functional nature of HEMA resulted in lower reactivity and conversion of monomers (below to 40% at 20 s of photoactivation). Water sorption (WS) and solubility (SL) tests expose the material to degradation processes that may simulate the oral environment, causing the hygroscopic and hydrolytic phenomena. A recent study that investigated the effect of different HEMA content on the DC, WS, and SL of experimental resin adhesives showed that the higher the HEMA concentration, the higher was the sorption and solubility effects, causing faster degradation processes.6 In our study, as expected, the control presented the highest WS (Table 2), probably because of the pendant hydroxyl present in the HEMA molecules. Additionally, P1000 also showed a high WS value, due to the high repetition of ethylene oxide units in the PEG 1000 monomer, which are also polar chemical groups with affinity for water molecules.6,9,12,31 Moreover, the alternative monomers present a different polar:non-polar unit ratio, which affects the intensity and hydrophilicity of the WS and SL phenomena. Bis-EMA 10, for example, is the most hydrophobic compared to the other monomers, because it presents aromatic C=C bonds and few ethylene oxide units.18 In contrast, PEG 400 has a similar number of ethylene oxide units, but lacks aromatic C=C bonds in its structure, leading to a higher WS value (Table 2). Nevertheless, the bisEMA monomers, which are truly more hydrophobic than HEMA and other hydrophilic monomers, are still partly hydrophilic (amphiphilic),17 as confirmed by the WS results achieved with the adhesives containing bis-EMA 10 and bis-EMA 30 (51.4 and 79.4 μg/mm3, respectively). 225

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Within the solubility analysis, the P400 and AH adhesives showed the highest SL (Table 2). Nevertheless, all the SL data were close to zero, indicating that little solubility phenomena had occurred, probably due to the formation of dense polymers.7 However, the water uptake can affect the mechanical properties of dental restoratives due to hygroscopic and hydrolytic phenomena. Thus, flexural strength (FS) and flexural modulus (E) tests were carried out under dry and wet conditions. In the dry subgroup, it could be observed that the control and the UP400 showed the highest values, except for the E test, in which the control showed a higher E mean value (Table 3). While HEMA is a small mono-functional monomer with flexible characteristics and mobility,3 the PEG 400 UDMA is formed by the urethane linkage, which is also a flexible group that may have resulted in high FS for UP400.23 Furthermore, considering that the HEMA monomer can link to the polymer network by only one extremity, and that its unbonded extremity is formed by a hydroxyl group (polar), it could be expected that this polar group would form strong hydrogen bonds with other HEMA molecules linked into the network system formed. This could also explain why the HEMA-containing adhesive demonstrated high FS and E properties. The other HEMAfree adhesives were less flexible, and they were unable to form strong hydrogen bonds the way HEMA does, leading to lower mechanical properties (Table 3). As opposed to the dry-storage specimens, wet storage negatively affected all the experimental adhesives, probably due to the water uptake that may have caused chemical degradation and some physical changes in the polymer matrix, reducing the mechanical properties evaluated.7 In addition, the ethanol solution was shown to be more aggressive than water because of its solubility parameter is closer to that of polymeric materials, intensifying the hygroscopic and hydrolytic effects on resin-based dental materials.14 An interesting finding was that the same adhesives that presented the highest WS values also demonstrated a greater reduction in their mechanical properties after wet storage. Nevertheless, the FS and E properties of all the experimental adhesives were reduced; however, some of the HEMA-free materials (P400, B10, and UP400) demonstrated higher strength than the control, mainly after storage in ethanol (Table 3).

control group. Nevertheless, in spite of only being able to interpret the present results as preliminary data, the above-mentioned monomers show potential for the development of HEMA-free adhesive systems. Therefore, further studies evaluating the performance of HEMA-free adhesives containing these monomers are necessary.

ACKNOWLEDGMENTS The authors are grateful to CAPES/MEC (Brazilian Government) for granting the scholarship (Process – 1145-09-6) and to Esstech Inc. for donating the reagents.

REFERENCES 1.

2.

3. 4.

5.

6.

7. 8.

9.

10.

11.

12.

13.

CONCLUSION Polymers formulated with mono-functional or long-chain dimethacrylates may have their mechanical properties compromised when maintained in wet conditions (eg, the oral environment).5 Thus, not all dimethacrylate monomers are suitable for composing a dental adhesive. Therefore, the hypothesis that the alternative dimethacrylates would improve the mechanical and physical characteristics of the experimental adhesives when compared with a HEMA-containing adhesive as tested in the present study can be only partially accepted, because in terms of some of the properties evaluated, they did not result in better characteristics than those of the 226

14.

15. 16.

17.

18.

Andreani L, Silva LL, Witt MA, Meier MM, Joussef AC, Soldi V. Development of dental resinuous systems composed of bisphenol A ethoxylated dimethacrylate and three novel methacrylate monomers: synthesis and characterization. J Appl Polym Sci 2012;128:725-734. Andreasson H, Boman A, Johnsson S, Karlsson S, Barregard L. On permeability of methyl methacrylate, 2-hydroxyethyl methacrylate and triethyleneglycol dimethacrylate through protective gloves in dentistry. Eur J Oral Sci 2003;111:529-535. Andrzejewska E. Photopolymerization kinetics of multifunctional monomers. Prog Polym Sci 2001;26:605-665. Beun S, Bailly C, Dabin A, Vreven J, Devaux J, Leloup G. Rheological properties of experimental Bis-GMA/TEGDMA flowable resin composites with various macrofiller/microfiller ratio. Dent Mater 2009;25:198-205. Cheng L, Zhang K, Melo MA, Weir MD, Zhou X, Xu HH. Anti-biofilm Dentin Primer with Quaternary Ammonium and Silver Nanoparticles. J Dent Res 2012;91:598-604. Collares FM, Ogliari FA, Zanchi CH, Petzhold CL, Piva E, Samuel SM. Influence of 2-hydroxyethyl methacrylate concentration on polymer network of adhesive resin. J Adhes Dent 2011;13:125-129. Ferracane JL. Hygroscopic and hydrolytic effects in dental polymer networks. Dent Mater 2006;22:211-222. Guo X, Spencer P, Wang Y, Ye Q, Yao X, Williams K. Effects of a solubility enhancer on penetration of hydrophobic component in model adhesives into wet demineralized dentin. Dent Mater 2007;23:1473-1481. Hosaka K, Nakajima M, Takahashi M, Itoh S, Ikeda M, Tagami J, Pashley DH. Relationship between mechanical properties of one-step selfetch adhesives and water sorption. Dent Mater 2010;26:360-367. Krifka S, Hiller KA, Spagnuolo G, Jewett A, Schmalz G, Schweikl H. The influence of glutathione on redox regulation by antioxidant proteins and apoptosis in macrophages exposed to 2-hydroxyethyl methacrylate (HEMA). Biomaterials 2012;33:5177-5186. Liu Y, Tjäderhane L, Breschi L, Mazzoni A, Li N, Mao J, Pashley DH, Tay RF. Limitations in bonding to dentin and experimental strategies to prevent bond degradation. J Dent Res 2011;90:953-968. Malacarne J, Carvalho RM, de Goes MF, Svizero N, Pashley DH, Tay FR, Yiu CK, Carrilho MR. Water sorption/solubility of dental adhesive resins. Dent Mater 2006;22:973-980. Moraes RR, Faria-e-Silva AL, Ogliari FA, Correr-Sobrinho L, Demarco FF, Piva E. Impact of immediate and delayed light activation on selfpolymerization of dual-cured dental resin luting agents. Acta Biomater 2009;5:2095-2100. Moraes RR, Schneider LF, Correr-Sobrinho L, Consani S, Sinhoreti MA. Influence of ethanol concentration on softening tests for cross-link density evaluation of dental composites. Mater Res 2007;10:79-81. Nakabayashi N, Takarada K. Effect of HEMA on bonding to dentin. Dent Mater 1992;8:125-130. Ogliari FA, de Sordi ML, Ceschi MA, Petzhold CL, Demarco FF, Piva E. 2,3-Epithiopropyl methacrylate as functionalized monomer in a dental adhesive. J Dent 2006;34:472-477. Ogliari FA, Ely C, Lima GS, Conde MC, Petzhold CL, Demarco FF, Piva E. Onium salt reduces the inhibitory polymerization effect from an organic solvent in a model dental adhesive resin. J Biomed Mater Res B Appl Biomater 2008;86:113-118. Ogliari FA, Ely C, Zanchi CH, Fortes CB, Samuel SM, Demarco FF, Petzhold CL, Piva E. Influence of chain extender length of aromatic dimethacrylates on polymer network development. Dent Mater 2008;24: 165-171.

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Münchow et al 19. Oguri M, Yoshida Y, Yoshihara K, Miyauchi T, Nakamura Y, Shimoda S, Hanabusa M, Momoi Y, Van Meerbeek B. Effects of functional monomers and photo-initiators on the degree of conversion of a dental adhesive. Acta Biomater 2012;8:1928-1934. 20. Paranjpe A, Bordador LC, Wang MY, Hume WR, Jewett A. Resin monomer 2-hydroxyethyl methacrylate (HEMA) is a potent inducer of apoptotic cell death in human and mouse cells. J Dent Res 2005;84:172-177. 21. Rathke A, Alt A, Gambin N, Haller B. Dentin diffusion of HEMA released from etch-and-rinse and self-etch bonding systems. Eur J Oral Sci 2007;115: 510-516. 22. Scranton AB, Bowman CN, Klier J, Peppas NA. Polymerization reaction dynamics of ethylene glycol methacrylates and dimethacrylates by calorimetry. Polymer 1992;33:1683-1689. 23. Sideridou I, Tserki V, Papanastasiou G. Effect of chemical structure on degree of conversion in light-cured dimethacrylate-based dental resins. Biomaterials 2002;23:1819-1829. 24. Silikas N, Watts DC. Rheology of urethane dimethacrylate and diluent formulations. Dent Mater 1999;15:257-261. 25. Sulca NM, Munteanu AV, Popescu RG, Lungu A, Stan R, Iovu H. Dibenzylidene sorbitol derivatives for improving dental materials properties. U P B Sci Bull 2010;72:25-36. 26. Takahashi M, Nakajima M, Hosaka K, Ikeda M, Foxton RM, Tagami J. Long-term evaluation of water sorption and ultimate tensile strength of HEMA-containing/-free one-step self-etch adhesives. J Dent 2011;39: 506-512. 27. Tulig TJ, Tirrell M. Molecular theory of the Trommsdorff effect. Macromolecules 1981;14:1501-1511. 28. Van Landuyt KL, Snauwaert J, De Munck J, Peumans M, Yoshida Y, Poitevin A, Coutinho E, Suzuki K, Lambrechts P, Van Meerbeek B. Systematic review of the chemical composition of contemporary dental adhesives. Biomaterials 2007;28:3757-3785.

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29. Van Landuyt KL, Yoshida Y, Hirata I, Snauwaert J, De Munck J, Okazaki M, Suzuki K, Lambrechts P, Van Meerbeek B. Influence of the chemical structure of functional monomers on their adhesive performance. J Dent Res 2008;87:757-761. 30. Wallenhammar LM, Ortengren U, Andreasson H, Barregard L, Bjorkner B, Karlsson S, Wrangsjö K, Meding B. Contact allergy and hand eczema in Swedish dentists. Contact Dermatitis 2000;43:192-199. 31. Yiu CK, King NM, Carrilho MR, Sauro S, Rueggeberg FA, Prati C, Carvalho RM, Pashley DH, Tay FR. Effect of resin hydrophilicity and temperature on water sorption of dental adhesive resins. Biomaterials 2006;27:1695-1703. 32. Zanchi CH, Munchow EA, Ogliari FA, Chersoni S, Prati C, Demarco FF, Piva E. Development of experimental HEMA-free three-step adhesive system. J Dent 2010;38:503-508. 33. Zanchi CH, Munchow EA, Ogliari FA, de Carvalho RV, Chersoni S, Prati C, Demarco FF, Piva E. Effects of long-term water storage on the microtensile bond strength of five experimental self-etching adhesives based on surfactants rather than HEMA. Clin Oral Investig 2013;17:833-839. 34. Zanchi CH, Munchow EA, Ogliari FA, de Carvalho RV, Chersoni S, Prati C, Demarco FF, Piva E. A new approach in self-etching adhesive formulations: replacing HEMA for surfactant dimethacrylate monomers. J Biomed Mater Res B Appl Biomater 2011;99:51-57.

Clinical relevance: Adhesive systems formulated without HEMA can be an alternative means of bonding resin composite restorations.

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Replacing HEMA with alternative dimethacrylates in dental adhesive systems: evaluation of polymerization kinetics and physicochemical properties.

To evaluate the mechanical and physical properties of experimental HEMA-containing and HEMA-free resin adhesives...
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