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Acta Odontológica Latinoamericana

versión impresa ISSN 0326-4815versión On-line ISSN 1852-4834

Acta odontol. latinoam. vol.33 no.2 Buenos Aires set. 2020  Epub 01-Sep-2020



Effect of alternative solvent evaporation techniques on mechanical properties of primer–adhesive mixtures

Efeito de técnicas alternativas utilizando evaporação de solvente nas propriedades mecânicas da mistura primer-adesivo

Isabel Ferreira-Barbosa1 

Josué J Araújo-Pierote1 

Lívia Rodrigues de Menezes2 

Lucia Trazzi-Prieto1 

João V Frazão-Camara3 

Larissa Sgarbosa de Araújo-Matuda4 

Giselle M Marchi1 

Luis A Maffei Sartini-Paulillo1 

Cintia T Pimenta de Araujo5 

1Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba, Departmento de Odontologia Restauradora, Piracicaba, Brasil

2Universidade Federal do Rio de Janeiro, Instituto de Macromoléculas Professora Eloisa Mano, Departamento de Química, Rio de Janeiro, Brasil

3Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Ciências Biológicas, Bauru, Brasil

4Universidade do Oeste Paulista, Departamento de Odontologia Restauradora, Presidente Prudente, Brasil

5Universidade Federal dos Vales do Jequitinhonha e Mucuri, Faculdade de Ciências da Saúde, Departamento de Odontologia, Diamantina, Brasil


This study evaluated the influence of the mode and time of solvent evaporation on the tensile strength (TS), flexural strength (FS) and elastic modulus (EM) of two adhesive systems: Scotchbond Multipurpose (SBMP) and Clearfil SE (CSEB). For this purpose, rectangular samples (2x1x7 mm) were prepared with 10 μL of primer and the solvents were evaporated with air spray at (23±1) ºC, (40±1) ºC and negative control (without spray). For each temperature, the times of 5, 20, 30, and 60 seconds were investigated. The statistical results showed that evaporation at 40±1ºC resulted in better EM for the two adhesives tested and all the evaporation times evaluated. However, there were no significant differences between the times and modes of evaporation for TS. The results of this study indicate that evaporation at a temperature of (40±1) °C could improve the elastic modulus of both adhesives tested, regardless of the evaporating time.

Keywords: Dentin bonding agents; Tensile strength; Flexural strength


Este estudo avaliou a influência do modo e do tempo de evaporação do solvente na resistência à tração (RT), resistência à flexão (RF) e módulo de elasticidade (MR) de dois sistemas adesivos: Scotchbond Multipurpose (SBMP) e Clearfil SE (CSEB). Para isso, amostras retangulares (2x1x7 mm) foram preparadas com 10 μL de primer e os solventes foram evaporados com aerossol a (23±1) ºC, (40±1) ºC e controle negativo (sem aerossol). Para cada temperatura, foram avaliados os tempos de 5, 20, 30 e 60 segundos. Os resultados estatísticos mostraram que a evaporação a (40±1) ºC resultou em melhor MR para os dois adesivos testados e todos os tempos de evaporação avaliados. No entanto, não houve diferenças significativas entre os tempos e modos de evaporação na RT. Os resultados deste estudo indicam que a evaporação a uma temperatura de (40±1) °C poderia melhorar o módulo de elasticidade de ambos os adesivos testados, independentemente do tempo de evaporação.

Palavras-chave: Adesivos dentinários; Temperatura; Resistência à tração; Propriedades de flexão


Dentin hybridization through monomeric interdiffusion is an essential mechanism to obtain an effective, intimate bond to the dentin tissue1. However, the bond between the dental substrate and the restorative material is affected by the presence of residual water or excess solvent. The residual solvent in these systems may act as a polymeric matrix plasticizer, interfering with the mechanical properties of these materials and consequently with the bonding interface2,3.

The solvents in the composition of adhesive systems should be completely evaporated from the resin-infiltrated dentin matrix4-6. Excess water or other solvents from inadequate evaporation may negatively affect the physical-mechanical strength ofthe adhesion layer due to the inhibition of the polymerization of these materials and the plasticization of the adhesive structure by the presence of solvent molecules5-7.

The influence of excess solvent on the bond strength and mechanical properties of adhesive systems has been tested in several in vitro studies, which reported quick, standardized results establishing the behavior of materials in conditions similar to those in clinical practice3-7. However, these studies evaluated only the pure adhesive solutions, without primer addition. There is therefore a need to evaluate the primer/ adhesive mixture for better comparison with what actually happens in clinical practice.

It has been shown that mixing the adhesive with the primer solution decreases the mechanical resistance of adhesive systems because the polymerization process is inhibited by compounds in the primer8,9. It is therefore important to determine the effect of solvent evaporation on the mechanical properties of primer/adhesive mixtures.

Considering the adverse effect of excess solvent on the polymerization of adhesive systems9, the creation of alternative techniques for better evaporating these solvents can provide greater adhesive longevity. Thus, the aim of this study was to test the hypothesis that the evaporation of the solvent at high temperatures may improve the mechanical properties of Scotchbond Multipurpose Plus™ and Clearfil SE Bond™.


This study investigated two commercial adhesives: a conventional three-step adhesive system -

Scotchbond Multipurpose Plus™ (SBMP-3M ESPE, St. Paul, MN, USA) and a two-step selfetching adhesive - Clearfil SE Bond™ (CSEB-Kuraray Medical Inc., Okayama, Japan).

These adhesive systems were selected because they are both the gold standard of their classes and have repeatedly shown excellent results in clinical and laboratory studies10-12. Table 1 presents the composition of the adhesive systems and Fig. 1 shows the preparation of specimens for each adhesive.

Table 1 Composition of the bonding agents 

Fig. 1 Experimental design 

2.1 Sample preparation

Bar specimens (1 mm x 2 mm x 7 mm) were prepared in a rectangular silicone mold from the mixture of primer and adhesive of the two systems used. A total 360 specimens were obtained (n = 5 for modulus of elasticity and flexural strength and n = 10 for maximum tensile strength).

The solvent was evaporated by air spray at room temperature (23±1) °C and by heated air spray (40±1) °C using a device with pressure, airflow, and controlled power to provide airflow at a constant temperature. The temperature of the hot air at the spray outlet was approximately 100 °C. A standard distance of 5 cm was set between the air spray outlet and the mold surface to obtain a temperature of (40±1) °C in the sample drying process.

Initially, 10 pL of primer of each adhesive system investigated was inserted in the silicone mold, followed by the primer evaporation process according to the mode and time proposed in the experimental design. After that, 20 pL of adhesive were added and carefully mixed with the primer for 60 s to prevent the incorporation of bubbles (as far as possible). The primer/adhesive ratio by weight was 1:3, in accordance with the protocol established by Burchardt and Merz13. The samples were dried at different temperatures and photopolymerized using the Vip Bisco (Vip Curing Lights - BISCO Dental Products IL, USA) with 600 mw/cm2 of light intensity.

The light was activated with a holder coupled to the light sources to standardize a 4 mm distance between the light guide tip and the material, which simulated a medium cavity depth. The polymerized samples were removed from the silicon mold and stored in distilled water for 24 h at 37 °C.

2.2 Measurement of tensile strength (TS)

The dimensions of the specimens were measured with a digital caliper (Digimatic Caliper, Mitutoyo, Tokyo, Japan). Bar-shaped specimens were attached to a device with cyanoacrylate adhesive and tested under tension in a Universal Testing Machine (EMIC Ltda., Sao José dos Pinhais, SP, Brazil) at 0.5 mm/min speed until rupture. The TBS values were calculated in MPa by dividing the load at rupture by the cross-sectional area.

2.3 Measurement of flexural strength (FS) and elastic modulus (EM)

The specimens were subjected to a three-point bending flexural test to measure flexural strength (FS) and elastic modulus (EM). The three-point bending test was performed in a universal testing machine (Instron model 4411, Instron Corp., Canton, MA, USA) according to ISO 4049 specifications.

Before the test, the dimensions of each specimen were recorded with a caliper. The Bluehill 2 software (Instron Corp., Canton, MA, USA) was used to calculate EM (GPa) and FS (MPa) values according to the dimensions and tension in each case. The maximum loads were obtained and the flexural strength (σ) was calculated in megapascals (MPa) by using the formula:

σ = 3FL/(2BH2)

where F is the maximum load (in newtons); L is the distance between the supports (in millimeters); B is the width of the specimen (in millimeters) and H is the height (also in millimeters).

The modulus of elasticity (GPa) was calculated as:

E = FL3/4BH3d

where F is the maximum load; L is the distance between the supports; B is the width of the specimen, H is the height of the specimen, and d is the deflection (in millimeters) corresponding to the load F.

2.4 Statistical analysis

The data were analyzed with one-way ANOVA and Tukey's post-hoc test at a 99.5% confidence level. In addition, they were subjected to multivariate analysis of variance (MANOVA) with repeated measures and a Lambda Wilks test (p<0.05).


Based on the elastic modulus results (Table 2), the evaporation at ± 40°C resulted in a higher elasticity modulus, regardless of the time of application of the air spray and the adhesive system used. The use of the heated air spray led to 1.59 GPa mean modulus value, which was statistically higher than the value found for the groups where spray at room temperature (1.40 GPa) or evaporation without application of air spray (1.37 GPa) were used.

Table 2 Elastic modulus (EM) of the different solvent evaporation types 

As for the influence of time on the elastic modulus, the increase of the evaporation time did not affect the behavior of the adhesive systems investigated. There was an exception for the time of 5 s for the CSEB self-etching adhesive system, which showed a significant reduction in the elasticity modulus when compared to the time of 30 s for the same group (1.60 GPa) and 60 s for the conventional adhesive system (1.56 GPa). The specimens from the other groups presented EM with statistically similar results (Table 3).

Table 3 Elastic modulus (EM) of the different solvent evaporation times 

Flexural strength analysis showed that the change in the solvent evaporation regime did not lead to any significant results. However, comparing the systems evaluated, the CSEB self-etching adhesive system (84.04 MPa) was found to have better properties than the SBMP etch-and-rinse system (62.44 MPa) (Table 4).

Table 4 Flexural strength (FS) according to adhesive system interaction, time and type of solvent evaporation 

The interaction between adhesive system, mode, and evaporation time did not present statistical difference concerning maximum tensile strength (Table 5).

Table 5 Maximum tensile strength (TS) according to adhesive system interaction, time and type of solvent evaporation 


The solvent present in adhesive systems acts as a transport vehicle by decreasing the viscosity of the adhesive, thereby enabling the resinous monomers to penetrate the micropores formed by acid etching13,14. However, incomplete solvent evaporation significantly compromises adhesion efficacy3-7,14, considering that excess solvents can lead to a dilution of the components that prevent the collision of reactive components. This hinders the attainment of high cross-linking polymers inside the hybrid layer, which may result in a porous hybrid layer structure with less mechanical properties15. The results showed that both drying time and temperature had a significant effect on the mechanical properties of the two adhesive systems tested. The application of hot air spray (40 ± 1°C) produced better elasticity modulus values, regardless of the adhesive system used. The elastic modulus represents the relative stiffness of the material as well as its resistance to plastic deformation, which is directly related to the formation of more crosslinks in the polymer structure.2 The increase in the modulus as a result of the heated air spray is probably due to the efficient removal of the solvent, leading to a more efficient polymerization process3,4,14.

This phenomenon may be also explained based on the formulation ofthe two adhesive systems investigated in this study, in which the primer formulation contains HEMA and water. The presence of HEMA is important because it can expand the dried dentin collagen and improve adhesion. However, the presence of HEMA in these systems improves the retention of solvent and water in polymer networks due to its influence on resin polarity. The presence of HEMA provides the high number of OH groups in the polymeric chains and improves the hydrogen bonding sites between polymer and solvent, hindering solvent evaporation16. In this case, the use of temperature for solvent elimination is important to better evaporate the water in the system.

In these adhesives with HEMA/water mixtures, the water evaporates more rapidly than the HEMA, which is a relatively non-volatile component. Thus, the concentration of HEMA increases as the water evaporates, reducing the vapor pressure of the water and making the adhesive more viscous, which makes it difficult to remove the last remaining water16,17. The difference in the properties of the two adhesive systems compared in this study may be due to their composition. The primer in the self-etching adhesive system (CSEB) contains acid monomers, HEMA, and water, while the primer in the conventional three-step adhesive system (SBMP) contains only water and HEMA. The incorporation of acid monomers in the simplified adhesive systems is necessary to condition the dental structures. However, such monomers may increase the water absorption by these systems due to the interaction of monomers and water18.

The interaction between adhesive and time shows that the increase of water concentration results in an adhesive interface with loss of mechanical properties, higher water absorption, and a lower degree of conversion18,19. The increase in water concentration results in increased ionization of acid monomers, which may reduce their reactivity and the polymerization of the systems18,20. Thus, the lowest mechanical property exhibited at 5 s for all adhesives may be due to the high concentration of residual water that did not allow adequate polymerization of these monomers.

Tensile strength evaluates the cohesion in the polymer layer formed after polymerization. Thus, increasing cohesion indicates a formation of a hybrid layer with lower microporosity, which is consequently less susceptible to infiltration2. In this study, there was no statistical difference in tensile strength, indicating that the evaporation obtained was not sufficient to improve material cohesion. The result does not corroborate previous studies that show the increase of cohesive resistance against the change in solvent evaporation3-7,14. However, those studies did not use the primer/adhesive mixture, which may be responsible for the difference observed.

Similarly, the evaluation of flexural strength showed no statistical difference regarding the different times and modes of solvent evaporation. For flexural strength, it was observed that the CSEB adhesive system obtained better results than the SBMP. The evaluation of this property is important for clinical practice, considering that the adhesive layer must undergo the least flexing when submitted to masticatory loads and this mechanical property can evaluate the resistance of the material to deformity as well as the tensile strength2.

As mentioned above, the adhesive systems used have different primer compositions. The CBSE contains, along with HEMA and water, acidic monomers that are hydrophilic and favor higher water adsorption by the primer of the adhesive system, making it less viscous. The lower the viscosity of a fluid, the faster and more easily it will move and thus allow greater interaction among the monomers, resulting in a more complete polymerization reaction with a better quality of crosslinks and providing greater cohesion to the polymers14.

According to the results of this study, evaporation time did not provide a positive correlation between TBS and EM. The EM of the adhesives tested was increased with hot air evaporation, while flexural strength did not change. It is therefore believed that the evaporation of the solvent with heated air spray provides a greater number of crosslinks, but a better quality between these bonds could not be obtained.


The results of the present study show that:

- The different solvent evaporation modes and temperatures did not affect the flexural strength of the adhesives tested.

- The CSEB system obtained better results than CBMP regarding flexural strength.

- Hot air spray evaporation (40°C) obtained better results of elasticity modulus (relative rigidity of the material), i.e., a greater number of crosslinks regardless of the adhesive system and time of evaporation.


1 Ayyildiz S, Pak Tunc E, Emir F, Sen D. Microscopic evaluation of the thickness and structure of the cement and cement–dentin interdiffusion zone after luting posts with three different luting cements. Journal of Adhesion Science and Technology. 2016;30:1049-1058. doi:10.1080/01694243.2015.1137698 [ Links ]

2 Bersezio C, Toledo S, Letelier C, Werner A, Oliveira Jr OB, Haydar ZS, Fernández E. Influence of the Passive Evaporation of adhesive on the conductance of dentin. Rev. Clin. Periodoncia Implantol. Rehabil. Oral. 2017;10:38- [ Links ]

3 Burke FT, Lawson A, Green DJ, Mackenzie L. What’s new in dentine bonding?: universal adhesives. Dent update. 2017;44:328-330, 332, 335-338, 340 [ Links ]

4 Dhanpal PCKY, Yiu CKY, King NM, Tay FR, Hiraishi N. Effect of temperature on water sorption and solubility of dental adhesive resins. J Dent. 2009;37:122-132. [ Links ]

5 Giacomini MC, Casas-Apayco LC, Machado CM, Freitas MCCDA, Atta MT, Wang L. Influence of Erosive and Abrasive Cycling on Bonding of Different Adhesive Systems to Enamel: An In situ Study. Braz Dent J. 2016;27:548-555. [ Links ]

6 Ikeda T, De Munck J, Shirai K, Hikita K, Inoue S, Sano H, Van Meerbeek B. Effect of evaporation of primer components on ultimate tensile strengths of primer– adhesive mixture. Dent Mater. 2005;21:1051-1058. [ Links ]

7 Klein-Junior CA, Zander-Grande C, Amaral R, Stanislawczuk R, Garcia EJ, Baumhardt-Neto R, Reis A. Evaporating solvents with a warm air-stream: effects on adhesive layer properties and resin–dentin bond strengths. J Dent. 2016;36:618-625. [ Links ]

8 Loguercio AD, Loeblein F, Cherobin T, Ogliari F, Piva E, Reis A. Effect of solvent removal on adhesive properties of simplified etch-and-rinse systems and on bond strengths to dry and wet dentin. J Adhes Dent. 2009;11:51-55. [ Links ]

9 Luque-Martinez IV, Perdigão J, Muñoz MA, Sezinando A, Reis A. Effects of solvent evaporation time on immediate adhesive properties of universal adhesives to dentin. Dent Mater. 2014;30:1126-1135. [ Links ]

10 Manfroi FB, Marcondes ML, Somacal DC, Borges GA, Júnior LHB, Spohr AM. Bond strength of a novel one bottle multi-mode adhesive to human dentin after six months of storage. Open Dent J. 2016;10:268-275. [ Links ]

11 Menezes LR, Silva EO. The use of montmorillonite clays as reinforcing fillers for dental adhesives. Mat Res. 2016;19:236-242. [ Links ]

12 Mirzakhani M, Mousavinasab SM, Atai M. The effect of acrylate-based dental adhesive solvent content on microleakage in composite restorations. Dent Res J. 2016;13:515-522. [ Links ]

13 Burchardt BR, Merz PW, in Handbook of Adhesives and Sealants, 2006. [ Links ]

14 Niem T, Schmidt A, Wöstmann B. Bonding resin thixotropy and viscosity influence on dentine bond strength. J Dent. 2016;51:21-28. [ Links ]

15 Nunes TG, Garcia FCP, Osorio R, Carvalho R, Toledano M. Polymerization efficacy of simplified adhesive systems studied by NMR and MRI techniques. Dent Mater. 2016;22:963-972. [ Links ]

16 Reis A, Loguercio AD, Carvalho RM, Grande RMH. Durability of resin dentin interfaces: effects of surface moisture and adhesive solvent component. Dent Mater. 2004;20:669-676. [ Links ]

17 Rodríguez HA, Giraldo LF, Casanova H. Formation of functionalized nanoclusters by solvent evaporation and their effect on the physicochemical properties of dental composite resins. Dent Mater. 2015;31:789-798. [ Links ]

18 Saikaew P, Chowdhury AA, Fukuyama M, Kakuda S, Carvalho RM, Sano H. The effect of dentine surface preparation and reduced application time of adhesive on bonding strength. J Dent. 2016;47:63-70. [ Links ]

19 Yiu CK, Pashley EL, Hiraishi N, King NM, Goracci C, Ferrari M, Tay FR. Solvent and water retention in dental adhesive blends after evaporation. Biomaterials. 2015;26:6863-6872. [ Links ]

20 Bersebio C, Martin J, Xaus G, Vildosola P, Oliveira OB, Jr Moncada G, et al. Influence of type of bur and acid etching on dentin hydraulic conductance. Acta Odontol Latinoam. 2013;26:131-137. [ Links ]

Received: March 1, 2020; Accepted: July 1, 2020

CORRESPONDENCE Dr. João Victor Frazão Câmara: Alameda Doutor Octávio Pinheiro Brisolla, 6-65, Apartment 61, Zip code 17012-059, Vila Santa Teresa, Bauru, SP, Brasil.

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