Influence of the Number of Adhesive Layers on Adhesive Interface Properties Under Cariogenic Challenge Using Streptococcus Mutans Nashalie Andrade de Alencara / Tatiana Kelly da Silva Fidalgob / Marlus Roberto Rodrigues Cajazeirac / Lucianne Cople Maiad

Purpose: To test the hypothesis that the number of adhesive layers influences the adhesive interface properties under cariogenic challenge conditions using a Streptococcus mutans model. Materials and Methods: Bovine teeth (n = 90) were sectioned into blocks of 5 mm and divided into two groups for microleakage testing (n = 60) and tensile bond strength testing (n = 30). In each group, the samples were subdivided into subgroups according to the number of adhesive layers applied on the dentin: one (SB1), two (SB2), and three adhesive layers (SB3). The samples of the control groups were placed in BHI broth medium supplemented with 2% sucrose without microorganisms, and the experimental groups were submitted to Streptococcus mutans American Type Culture Collection (ATCC) for 5 days. For the tensile strength test, samples were sectioned into 1-mm-thick slices and submitted to a constant load of 0.5 mm/min in a universal testing machine. Fractured surfaces were analyzed and characterized as adhesive, cohesive, or mixed. The microleakage test was performed with silver nitrate solution. Results: In experimental groups, the tensile test revealed a statistically signifcant difference between the one- (18.59 ± 5.3) and three-layer (11.28 ± 5.0) groups (p < 0.001; ANOVA and Tukey’s test). The adhesive failure mode was slightly more frequent in the one- (60%) and three-layer (80%) adhesive application groups. On the other hand, the microleakage levels of all experimental groups were statistically similar (Kruskal-Wallis; p > 0.05). Conclusion: The experimental conditions influenced tensile properties and failure modes of different adhesive interfaces; however, they did not influence microleakage. Keywords: dentin bonding agent, tensile strength, dental leakage, Streptococcus mutans, dental caries. J Adhes Dent 2014; 16: 339–346. doi: 10.3290/j.jad.a32569

a

Graduate Student, Department of Pediatric Dentistry and Orthodontics, School of Dentistry, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. Performed the experiments, performed statistical analysis, wrote the manuscript.

b

Postdoctoral Fellow, Department of Pediatric Dentistry and Orthodontics, School of Dentistry, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. Performed the experiments, proofread the manuscript, performed statistical evaluation, contributed substantially to discussion.

c

PhD Student, Associate Professor, Department of Specific Formation, School of Dentistry, Universidade Federal Fluminense – Nova Friburgo, Rio de Janeiro, Brazil. Experimental design, proofread the manuscript, performed statistical evaluation, and contributed substantially to discussion.

d

Full Professor, Department of Pediatric Dentistry and Orthodontics, School of Dentistry, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. Idea, hypothesis, experimental design, proofread the manuscript, performed statistical evaluation, and contributed substantially to discussion.

Correspondence: Professor Lucianne Cople Maia, Disciplina de Odontopediatria da FO-UFRJ, Caixa Postal: 68066, Cidade Universitária, CCS, CEP 21941971, Rio de Janeiro, RJ, Brazil. Tel: +55-21-2562-2101. e-mail: [email protected]

Vol 16, No 4, 2014

Submitted for publication: 27.06.13; accepted for publication: 14.02.14

T

he hybrid layer is an important structure for the adhesion of composite resins to dentin.25 It is formed by the replacement of dissolved hydroxyapatite crystals with adhesive monomers that infiltrate in dentin and copolymerize in intimate contact with the collagen fiber network.9 Typically, the etch-and-rinse technique is based on an acid conditioner, usually phosphoric acid at concentrations from 30% to 40%, for removal of smear layer and superficial demineralization of the underlying dentin. After rinsing off the phosphoric acid, the conditioned surface is prepared to receive the primer and adhesive, which may be in separate containers or together in the same vial.9 Some demineralized dentin remains that is not completely infiltrated by the adhesive during etching, resulting in a persistent area of unprotected collagen located under the hybrid layer.17,35 The existence of this unprotected 339

de Alencar et al

90 bovine incisors

Microleakage 60 blocks

SB 1 20 blocks

SB 2 20 blocks

SB 3 20 blocks

Tensile bond strength 30 blocks

Cariogenic challenge BHI + sucrose + S. mutans (30 blocks)

Cariogenic challenge BHI + sucrose + S. mutans (15 blocks)

Control BHI + sucrose (30 blocks)

Control BHI + sucrose (15 blocks)

SB 1 10 blocks

SB 2 10 blocks

SB 3 10 blocks

Fig 1 Design of cariogenic challenge experiments.

area is considered an important drawback of the etchand-rinse technique, and it may present a risk to bonding longevity, since unprotected collagen fibers can be hydrolyzed15,16 or degraded by endogenous metalloproteinases in the dentin.10,27 However, the monomer infiltration level into dentin may be increased by the technique with which the adhesive is applied. Some authors suggest increasing the application time,32 applying friction during application,8 and using a consecutive multilayer adhesive approach.18,19 The multilayer application increases the bond strength with dentin and produces a less porous hybrid layer which is less susceptible to degradation.19 The long-term maintenance of adhesive interface integrity is still a challenge in adhesive dentistry.9 This difficulty usually occurs in clinical practice, since failure due to marginal leakage23 and secondary caries20,23 are directly associated with the adhesive interface degradation process. Simple changes to bonding technique can improve resin-dentin bond strengths and keep the restoration intact.11 Therefore, the effect of multilayer adhesive application on bonding and the quality of the resin/dentin interface is of crucial interest in clinical practice. Adhesive interface deterioration in vivo is a complex phenomenon, occurring as a result of a combination of physical factors, such as chewing stress26 and dimensional changes resulting from thermal alterations,10 chemical enzymatic action,14,27 hydrolytic effects,10 and microbiological effects.5 Knowledge about the effects of cariogenic challenge on the adhesive interface is still limited.2 Cariogenic challenge consists of longer exposure to demineralizing conditions (acid exposure) than to remineralization (neutral exposure). To simulate cariogenic challenge, previous 340

laboratory studies have largely been performed using chemical models such as pH cycling.30,38 Collagen unprotected by the adhesive is susceptible to enzymatic degradation by microorganisms.21,35 However, microbiological methods to induce cariogenic challenge are still rarely applied. Thus, the aim of this study was to determine whether the different experimental hybridization protocols based on the number of adhesive layers influence the adhesive interface properties under cariogenic challenge conditions using a Streptococcus mutans microbiological model. The hypothesis was that different numbers of adhesive layers alter the tensile bond strength and the microleakage after submission to cariogenic challenge.

MATERIALS AND METHODS Sample Preparation and Groups Ninety bovine incisors without signs of hypoplasia, cracks, or fractures were selected for this study. The central portions of the buccal surfaces of the teeth were sectioned into blocks of 25 mm2 surface area (5 mm x 5 mm) and a thickness that varied as a function of enamel and dentin layer thickness, using a double-faced diamond saw under water cooling (Isomet, Buehler; Lake Bluff, IL, USA). Then the 90 enamel-dentin blocks were divided into two main groups according to the test performed (Fig 1): the tensile bond strength test (n = 60; 10 control and 10 submitted to the cariogenic challenge for each subgroup) and the microleakage test (n = 30; 5 control and 5 submitted to the cariogenic challenge for each subgroup). The Journal of Adhesive Dentistry

de Alencar et al

Sample preparation sequence for microitensile bond strength test

1.0 mm

3.5  mm 5.0 mm

1.0 mm 0.5  mm

2.0 mm

Tensile load (0.5 mm/min)

Enamel Dentin

5.0  mm

Score 0

5.0 mm

Test solution Control solution BHI + sucrose + S. mutans BHI + sucrose

Score 1 Score 2 Score 3

Microleakage analysis Sample preparation sequence for microleakage test

Fig 2 Sample preparations and experimental design.

Cavity Preparations Figure 2 illustrates the sample preparations and experimental design. For tensile bond strength specimens, a groove 5 mm wide, 5 mm long, and approximately 0.5 mm deep into the dentin was prepared on the enamel surface of the blocks using a cylindrical bur (#4103, KG Sorensen; São Paulo, SP, Brazil) mounted in a high-speed handpiece under copious water cooling. For the microleakage test, cavities with a diameter of 10 mm and a depth of 0.5 mm in dentin were prepared with cylindrical diamond burs (#4103, KG Sorensen) mounted in a high-speed handpiece under copious water cooling (Fig 2). Adhesive Application Techniques For both tensile bond strength and microleakage specimens, the enamel margins of the prepared cavities were conditioned with a 37% phosphoric acid gel (Dentsply; Petrópolis, RJ, Brazil) for 30 s and dentin walls for 15 s. After the conditioner was rinsed off for 30 s, excess moisture was removed with a cotton pellet. The adhesive used was Adper Single Bond 2 (3M ESPE; St Paul, MN, USA), applied in one, two, or three layers as follows: y One coat, subgroup SB1: One thin layer of Adper Single Bond 2 adhesive was passively applied to dentin using a microbrush (KG Sorensen). After thinning with a slow air stream for 5 s, the adhesive was polymerized for 10 s using a halogen light-curing unit set at 600 mW/cm2 (Elipar Highlight, 3M ESPE). y Two coats, subgroup SB2: The first thin layer of Adper Single Bond 2 adhesive was passively applied to dentin using a microbrush (KG Sorensen). An air stream Vol 16, No 4, 2014

was briefly applied to the first adhesive layer, and then a second layer was applied in the same manner as the first. These adhesive layers were polymerized for 10 s using the same halogen light-curing unit set at 600 mW/cm2. y Three coats, subgroup SB3: After the application of the second layer as described for subgroup SB2, a third thin adhesive layer was applied and polymerized for 10 s using the same light-curing unit set at 600 mW/cm2. Cavities were restored with Filtek Z350 composite resin (3M ESPE) according to the incremental technique. Each increment was polymerized for 20 s using the halogen light-curing unit set at 600 mW/cm2 (Elipar Highlight). For tensile bond strength specimens, the resin-composite buildups were standardized using a caliper rule to a height of 3.5 mm. Resin composite buildups were constructed above the top of the restored groove. After restoration of the samples for both tensile bond strength and microleakage testing, a layer of nail varnish was applied to the tooth to prevent demineralization of other areas, leaving only the buccal surface exposed. Microbiological Cariogenic Challenge Each prepared sample was placed into a well and sterilized in ethylene-oxide gas at 25°C to preserve the organic phase. After restoration, half of the specimens of each group were immersed in the test solution to simulate cariogenic challenge, while the other half was immersed in the control solution. For both groups, the incubation period was 7 days. For the control groups (C), each well was filled with 1.5 ml of BHI broth medium (Brain Heart Infusion, Difco; 341

de Alencar et al

a

b

c

Fig 3 Illustration of fracture modes. a: Detail of adhesive fracture showing exposed collagen fibers; b: adhesive fracture; c: cohesive fracture.

Franklin Lakes, NJ, USA) supplemented with 2% sucrose without microorganisms. For the experimental groups (E), inoculation was performed with American Type Culture Collection (ATCC) specimens of Streptococcus mutans ATCC 25175. Bacteria were kept at -20°C in tryptic soy broth (TSB; Oxoid, Hampshire, England) with 20% glycerol and activated by transfer into BHI agar. They were incubated under microaerophilic conditions at 37°C for 48 h in a candle jar. Bacterial cells were suspended according to the 0.5 McFarland protocol22 and the 0.5 scale in BHI broth medium supplemented with 2% sucrose. The absorbance was determined at 625 nm (A625) in a spectrophotometer (Bioespectro model SP-220; Curitiba, PR, Brazil). The A625 was set at 0.10, which is within the range (A625 = 0.08 to 0.14, corresponding to 1.5 x 108 CFU/ml) that corresponds to 0.5 on the McFarland scale. Then the cells were diluted to approximately 5.0 x 106/ml (1.5 ml/well). Subsequently, the experimental group was placed in contact with the S. mutans cells and the culture was incubated at 37°C under microaerophilic conditions for 5 days. The BHI broth medium supplemented with 2% sucrose of all samples was replaced twice throughout the experimental period. At the end of this period, the pH of the BHI medium (with and without inocula) was analyzed (pH-Fix test strips, Macherey-Nagel; Bethlehem, PA, USA) in both control and experimental groups. Tensile Bond Strength Test After a storage period in control or test solution, the specimens were sectioned into 6 sticks. The outer 2 sticks were discarded to avoid overexposure to Streptococcus mutans. The sticks, with dimensions of 2.0 mm (wide) x 1.0 (long) x 3.5 mm (deep), were fixed in special devices with a cyanoacrylate adhesive (Super Bonder, Loctite; São Paulo, SP, Brazil) and submitted to a tensile load at a crosshead speed of 0.5 mm/min in a universal testing machine (EMIC; São José dos Campos, SP, Brazil), as shown in Fig 2. The tensile bond strength values obtained were expressed in MPa (N/mm2). After bond strength measurement, the fracture modes were viewed at 20X magnification under an optical micro342

scope (Olympus SZ-ST stereomicroscope; Tokyo, Japan) by two independent examiners, and were classified as adhesive, cohesive, or mixed. Microleakage Test After the storage period, the samples were immersed in a 50% aqueous silver nitrate solution for 24 h in a light-proof container. Next, the blocks were rinsed thoroughly in tap water and immersed in a vial containing radiographic developing solution to reveal the silver nitrate and allow the visualization of the tracer-penetrated areas. The samples were sectioned longitudinally through the center of the restorations (Fig 2) using a diamond saw (Isomet, Buehler) under water coolant. The sectioned blocks were viewed at 20X magnification with an optical microscope (Olympus SZ-ST stereomicroscope) by two independent examiners who scored the extent of tracer penetration at the resin/dentin interface according to the following scoring system:33 0 = absence of dye penetration; 1 = dye penetration up to one-half of the extension of the wall; 2 = dye penetration up to onehalf of the extension of the wall without reaching the axial angle; 3 = dye penetration to the whole extent of the wall. Scanning Electronic Microscopy Fractured specimens of dentin were dried in a vial at room temperature for 24 h. The specimens were rinsed with deionized water to remove debris, dehydrated in ascending concentrations of ethanol (50%, 70%, and 95% for 10 min each; 100% for 30 min), and critical-point dried. The samples were positioned on a double-faced piece of adhesive tape on a sample chamber whose sequence was carefully recorded, and were then sputtercoated with gold-palladium. The samples were analyzed using an SEM (JEOL 2000 FX; Tokyo, Japan) operating at 20 kV and 2000X to 10,000X magnification (Fig 3). Statistical Analysis The microleakage scores, tensile bond strength values, and fracture mode were entered in the the statistical program SPSS 16.0 (SPSS; Chicago, IL, USA). Microleakage scores were statistically analyzed using non-parametric Kruskal-Wallis and Mann-Whitney tests. The Journal of Adhesive Dentistry

de Alencar et al

Table 1 Resin-dentin bond strength means and standard deviations (MPa) of control and experimental groups by number of layers

Tensile bond strength data were analyzed statistically by one-way ANOVA followed by Tukey’s test. All the tests were set at a significance level of 5%.

Layer Cariogenic challenge

RESULTS The proposed system was able to induce white spot lesions in all experimental groups. The pH in the BHI medium of the control group was 7.0 for all groups; in the BHI medium with microorganisms, the pH was 4.0 for all experimental groups, demonstrating that 5 days in contact with S. mutans supplemented with 2% sucrose produced a cariogenic challenge. Table 1 presents the bond strength values for the adhesive application protocols and cariogenic challenge. The statistical analyses revealed a significant difference among groups (p < 0.001; ANOVA). The highest mean tensile strength was obtained with single application in the control group (SB1-C). There was a reduction in the tensile strength values of the one- and two-layer experimental groups (p < 0.05), while in the three-layer group, this reduction was not statistically significant (p > 0.05). The three-layer group showed a tendency to have the lowest values under both conditions. The failure analysis of debonded specimens (Table 2, Fig 3) revealed that, in the SB1-C specimens, the adhesive and mixed failures were distributed equally (50%), while after cariogenic challenge, SB1-E reached adhesive (60%) and cohesive (30%) failures. The remaining 10% of failures were mixed. All SB2-C specimens (100%) fractured adhesively, but after the cariogenic challenge, the adhesive fractures decreased (43%) and the cohesive failures increased (43%). All cohesive failures occurred in dentin, probably due to demineralization after cariogenic challenge. SB3-C specimens predominantly showed failure in the adhesive layer (75%), while after the cariogenic challenge, the adhesive failures increased (80%). Thus,

Table 2

SB1

SB2

SB3

Control (C)

18.59 ± 5.3aC 12.55 ± 4.2abE 11.28 ± 5.0bG

Experimental (E)

7.28 ± 3.0aD

6.86 ± 2.8abF

5.99 ± 3.9bG

Superscript small letters indicate same statistical group (p > 0.05) by number of layers (SB1, SB2, and SB3) and superscript capital letters indicate same statistical group (p > 0.05) by cariogenic challenge (C and E).

after cariogenic challenge, the adhesive failure mode was slightly higher in the one- and three-layer adhesive groups. In the microleakage test, none of the scores of any of the experimental groups differed significantly from one another (Kruskal-Wallis; p > 0.05). The results showed extensive penetration (score 3) of silver nitrate in both control and experimental groups (Table 3), indicating that the experimental conditions did not influence the microleakage profile.

DISCUSSION The quality of the hybrid layer is crucial to the longevity of composite restorations.9 However, the literature has shown that hybrid layers produced from the etch-andrinse technique are not uniform. Experimental studies have demonstrated the existence of a zone located below the hybrid layer where the adhesive monomers do

Percentage (%) of failure

Failure

SB1-C

SB2-C

SB3-C

SB1-E

SB2-E

SB3-E

Adhesive (%)

50

100

75

60

43

80

Cohesive (%)

-

-

-

30

43

-

50

-

25

10

14

20

Mixed (%)

Table 3

Percentage (%) of microleakage distribution

Microleakage

SB1-C

SB2-C

SB3-C

SB1-E

SB2-E

SB3-E

Score 0 (%)

-

10

20

30

-

10

Score 1 (%)

10

20

-

10

-

10

Score 2 (%)

20

10

10

-

-

20

Score 3 (%)

70

60

70

60

100

60

Vol 16, No 4, 2014

343

de Alencar et al

not infiltrate the collagen.35,34 The presence of this area is a potential risk for failure of the restoration, as the unprotected collagen fibrils are more susceptible to hydrolysis and the combined action of metalloproteinases, such as collagenase, that are inactive in dentin but can be activated by acid etching.10,15,18 In this study, the initial hypothesis was accepted for tensile bond strength, since different numbers of adhesive layers influenced the tensile bond strength, and rejected for microleakage, since microleakage was not influenced by different protocols. The current protocol using multiple consecutive layers of adhesive has been previously assessed, showing a progressive increase of adhesive resistance values and reduced nanoleakage in hybrid layers proportional to the increase in the number of adhesive layers applied.18,19 However, contrary to the previous findings, the present study found bond strength values to decrease proportionally to the number of adhesive layers applied. Considering the high proportion of adhesive failures in both control and experimental conditions observed in groups SB1 and SB2, the decrease of the bond strength may have been related to the thickness of the adhesive layer located above the hybrid layer. Similar results were found in other studies.7,40 The formation of thicker adhesive layers due to successive application of adhesive can hinder the evaporation of solvents present in the adhesive composition, consequently decreasing monomer conversion and providing undesirable physical properties.40 This was probably the cause of reduced bond strength values. Thus, more studies evaluating other solvent-drying protocols in relation to monomer conversion rates should be performed. Regarding the effects of cariogenic challenge, all groups exhibited reduced bond strengths, especially SB1E. This may have been related to the lower infiltration through the conditioned dentin when only one adhesive layer was applied.18,19 The existence of an unprotected collagen zone has been associated with poly-HEMA hydrogel formation inside the collagen fibrils exposed by etching, resulting from a mixture of HEMA monomers and water molecules present in the interfibrillar spaces.36 The presence of the poly-HEMA hydrogel can allow the penetration of acids into the hybrid layer and promote its degradation.38 The reduction in bond strength may be related to the decreased cohesive strength of dentin that occurs as a result of the demineralization caused by cariogenic challenge.30 This could explain, for example, the fact that the highest percentages of failures were cohesive in groups SB1-E and SB2-E. However, in contrast to the findings of Peris et al,30 the present study found that the groups submitted to the cariogenic challenge did not demonstrate an increase in the occurrence of cohesive or mixed failures. This discrepancy may be related to the different method used in the two studies. Peris et al30 used pH cycling, whereas the present study employed a microbiological model, which maintained the pH below the critical value throughout the experimental period. The greatest advantage of the microbiological model is that it creates conditions similar to those that occur in the oral environment.37 The formation 344

of white spot lesions around all restorations submitted to microbiological cariogenic challenge demonstrated the effectiveness of this model, corroborating results by other authors.11 In this study, microleakage was not affected by the number of adhesive layers, emphasizing the poor sealing ability of restorations made by combining a nanocomposite (Filtek Z350) and a one-bottle adhesive (Adper Single Bond 2), as reflected in the relatively high proportion of score 3. The bond between composite resin and tooth substrate was not strong enough to withstand the stresses generated by polymerization shrinkage, considered the main disadvantage associated with the composite resins based on bis-GMA. In addition, the possibility should also be considered that these effects are exacerbated in class V cavities, which present a high C-factor.6 The C-factor is a coefficient related to contraction stress and is obtained from the ratio of the number of restored to free surfaces. The C-factor and the polymerization shrinkage of the composite are directly related.12 Thus, the contraction that the composite underwent may have been high enough to cause disruptions in the adhesive interface and, consequently, the formation of gaps in the restoration margins, allowing the massive penetration of silver nitrate into the adhesive interface, where the bond strength to enamel is higher than to dentin for etch-and-rinse systems.39 Comparing the levels of microleakage between groups submitted or not to cariogenic challenge, only for the two consecutive adhesive application groups (SB2C and SB2E) was a significant increase found in the level of infiltration in the cariogenic challenge condition. This was expected, since the degradation of the restoration margins should increase the penetration of silver nitrate. To the best of our knowledge, this is the first study that has assessed the adhesive interface properties formed by the application of one, two, and three adhesive layers after being submitted to cariogenic conditions with Streptococcus mutans cells. To increase acid production and potentiate cariogenic challenge, the sucrose supply was kept continuous and at a high concentration. Contrary to many studies that are conducted without microorganisms,13,28,29,31 the present study used Streptococcus mutans as a cariogenic challenge. The proteinases of this bacterial species cause secondary destruction of the tooth protein, contributing to a faster expansion of white spots,24 as observed with a stereomicroscope. This study demonstrates that the number of adhesive layers and cariogenic challenge do not influence the level of microleakage. This could be explained by the similar polymerization shrinkage of the composite in all groups. Although the cariogenic challenge model induced white spot lesions at restoration margins, it did not interfere with the marginal sealing ability of the different adhesive layers. In the tensile bond strength tests, the SB1-C and SB2-C groups presented higher bond strength in comparison to SB1-E and SB2-E, which were submitted to cariogenic challenge. This indicated that the cariogenic processes influenced the results. However, no significant difference between the control (SB3-C) and experimental conditions (SB3-E) was found. The thicker adhesive layer probably The Journal of Adhesive Dentistry

de Alencar et al

produced a better marginal seal, preventing the penetration of acid from Streptoccus mutans colonization. However, the thicker adhesive layer induced a reduction in tensile values, probably because of its poor adhesion to the dentin substrate. These results are in accordance with the fractographic analysis of the sticks. A larger number of cohesive failures in dentin were found in the SB1-E and SB2-E groups than in the SB1-C and SB2-C groups. We propose that the penetration of acid along the margins of the restoration demineralized the dentin adjacent to the hybrid layer, reducing its cohesive resistance. In addition, multiple adhesive applications may remove more water from the demineralized dentin after acid attack, permitting increased resin penetration into the collagen fibril network.1,4,19 The use of multiple applications of adhesives also allows more time for removal of water by inward diffusion of adhesive monomers and subsequent solvent evaporation from the interfibrillar spaces.18,19 In the current study, irrespective of the number of adhesive layers in the control groups, the highest bond strengths were observed when fewer layers of adhesive were applied. Hashimoto et al18,19 found that increasing the number of adhesive applications resulted in the desired tensile bond strength. In contrast, D’Arcangelo et al1 demonstrated that multiple adhesive coats significantly negatively affected the bond strength to dentin; an excess of adhesive layer thickness reduced the strength and the quality of adhesion, corroborating the present findings. Multiple adhesive layers probably promote excessive retention of water and organic solvents, resulting in inadequately converted polymers and unsatisfactory tensile bond strengths. Furthermore, it is important to emphasize that most studies have assessed mechanical properties under nonphysiological conditions.3,7,18,19 The present study was conducted to simulate a biological system. It seems that the cariogenic challenge using a Streptococcus mutans model affected the adhesive quality of the single and double layers, but the triple application was not influenced by the cariogenic challenge.

4.

5.

6.

7.

8.

9.

10.

11.

12. 13.

14. 15.

16.

17.

18.

19.

20.

21.

CONCLUSION 22.

The different experimental hybridization protocols based on the number of adhesive layers influenced the tensile bond strength and failure mode of adhesive interfaces submitted to cariogenic challenge. However, the number of adhesive layers did not influence the microleakage.

REFERENCES 1.

2.

3.

Albaladejo A, Osorio R, Toledano M, Ferrari M. Hybrid layers of etchand-rinse versus self-etching adhesive systems. Med Oral Patol Oral Cir Bucal 2010;15:112-118. Amaral FL, Colucci V, Palma-Dibb RG, Corona SA. Assessment of in vitro methods used to promote adhesive interface degradation: a critical review. J Esthet Restor Dent 2007;19:340-353. Arisu HD, Eliguzeloglu E, Uctasli MB, Omurlu H. Effect of multiple consecutive applications of one-step self-etch adhesive on microtensile bond strength. J Contemp Dent Pract 2009;10:67-74.

Vol 16, No 4, 2014

23.

24.

25.

26.

27.

28.

Arisu HD, Eliguzeloglu E, Uctasli MB, Omurlu H, Turkoz E. Effect of multiple consecutive adhesive coatings on microleakage of class v cavities. Eur J Dent 2009;3:178-184. Breschi L, Mazzoni A, Ruggeri A, Cadenaro M, Di Lenarda R, De Stefano Dorigo E. Dental adhesion review: aging and stability of the bonded interface. Dent Mater 2008;24:90-101. Choi KK, Condon JR, Ferracane JL. The effects of adhesive thickness on polymerization contraction stress of composite. J Dent Res 2000;79:812-817. D’Arcangelo C, Vanini L, Prosperi GD, Di Bussolo G, De Angelis F, D’Amario M, Caputi S. The influence of adhesive thickness on the microtensile bond strength of three adhesive systems. J Adhes Dent 2009; 11:109-115. Dal-Bianco K, Pellizzaro A, Patzlaft R, de Oliveira Bauer JR, Loguercio AD, Reis A. Effects of moisture degree and rubbing action on the immediate resin-dentin bond strength. Dent Mater 2006;22:1150-1156. De Munck J, Van Landuyt K, Peumans M, Poitevin A, Lambrechts P, Braem M, van Meerbeek B. A critical review of the durability of adhesion to tooth tissue: methods and results. J Dent Res 2005;84:118-132. De Munck J, Van den Steen PE, Mine A, Van Landuyt KL, Poitevin A, Opdenakker G, van Meerbeek B. Inhibition of enzymatic degradation of adhesive-dentin interfaces. J Dent Res 2009;88:1101-1106. Espejo LC, Simionato MR, Barroso LP, Netto NG, Luz MA. Evaluation of three different adhesive systems using a bacterial method to develop secondary caries in vitro. Am J Dent 2010;23:93-97. Feilzer AJ, De Gee AJ, Davidson CL. Setting stress in composite resin in relation to configuration of the restoration. J Dent Res 1987;66:1636-1639. Fidalgo TKS, Pithon MM, Santos RL, Alencar NA, Abrahão AC, Maia LC. Influence of topical fluoride application on mechanical properties of orthodontic bonding materials under pH cycling. Angle Orthod 2012;82:1071-1077. Finer Y, Santerre JP. Salivary esterase activity and its association with the biodegradation of dental composites. J Dent Res 2004;83:22-26. Hashimoto M, Ohno H, Endo K, Kaga M, Sano H, Oguchi H. The effect of hybrid layer thickness on bond strength: demineralized dentin zone of the hybrid layer. Dent Mater 2000;16:406-411. Hashimoto M, Ohno H, Kaga M, Endo K, Sano H, Oguchi H. In vivo degradation of resin-dentin bonds in humans over 1 to 3 years. J Dent Res 2000;79:1385-1391. Hashimoto M, Ohno H, Kaga M, Sano H, Endo K, Oguchi H. The extent to which resin can infiltrate dentin by acetone-based adhesives. J Dent Res 2002;81:74-78. Hashimoto M, De Munck J, Ito S, Sano H, Kaga M, Oguchi H, Van Meerbeek B, Pashley DH. In vitro effect of nanoleakage expression on resindentin bond strengths analyzed by microtensile bond test, SEM/EDX and TEM. Biomaterials 2004;25:5565-5574. Hashimoto M, Sano H, Yoshida E, Hori M, Kaga M, Oguchi H, Pashley DH. Effects of multiple adhesive coatings on dentin bonding. Oper Dent 2004;29:416-423. Inoue S, Vargas MA, Abe Y, Yoshida Y, Lambrechts P, Vanherle G, Sano H, Van Meerbeek B. Microtensile bond strength of eleven contemporary adhesives to dentin. J Adhes Dent 2001;3:237-245. Liu Y, Tjäderhane L, Breschi L, Mazzoni A, Li N, Mao J, Pashley DH, Tay FR. Limitations in bonding to dentin and experimental strategies to prevent bond degradation. J Dent Res 2011;90:953-968. McFarland J. Nephelometer. An instrument for estimating the number of bacteria in suspensions used for calculating the opsonic index and for vaccines. JAMA 1907;14:1176–1178. Mjör IA, Shen C, Eliasson ST, Richter S. Placement and replacement of restorations in general dental practice in Iceland. Oper Dent 2002;27:117-123. Mo SS, Bao W, Lai GY, Wang J, Li MY. The microfloral analysis of secondary caries biofilm around Class I and Class II composite and amalgam fillings. BMC Infect Dis 2010;10:241. Nakabayashi N, Takeyama M, Kojima K, Masuhara E. Studies on dental self-curing resins (20) - adhesion mechanism of 4-META/MMA-TBB resin to dentine [in Japanese]. Shika Rikogaku Zasshi 1982;23:34-39. Nikaido T, Kunzelmann KH, Ogata M, Harada N, Yamaguchi S, Cox CF, Hickel R, Tagami J. The in vitro dentin bond strengths of two adhesive systems in class I cavities of human molars. J Adhes Dent 2002;4:31-39. Pashley DH, Tay FR, Yiu C, Hashimoto M, Breschi L, Carvalho RM, Ito S. Collagen degradation by host-derived enzymes during aging. J Dent Res 2004;83:216-221. Passalini P, Fidalgo TK, Caldeira EM, Gleiser R, Nojima Mda C, Maia LC. Mechanical properties of one and two-step fluoridated orthodontic resins submitted to different pH cycling regimes. Braz Oral Res 2010;24:197-203.

345

de Alencar et al 29. Passalini P, Fidalgo TKS, Caldeira EM, Gleiser R, Nojima MCG, Maia LC. Preventive effect of eluoridated orthodontic resins subjected to high cariogenic challenges. Braz Dent J 2010;21:211-215. 30. Peris AR, Mitsui FH, Lobo MM, Bedran-Russo AK, Marchi GM. Adhesive systems and secondary caries formation: Assessment of dentin bond strength, caries lesions depth and fluoride release. Dent Mater 2007;23:308-316. 31. Queiroz CS, Hara AT, Paes Leme AF, Cury JA. pH-cycling models to evaluate the effect of low fluoride dentifrice on enamel de- and remineralization. Braz Dent J 2008;19:21-27. 32. Reis A, de Carvalho Cardoso P, Vieira LC, Baratieri LN, Grande RH, Loguercio AD. Effect of prolonged application times on the durability of resin-dentin bonds. Dent Mater 2008;24:639-644. 33. Retief DH, Woods E, Jamison HC. Effect of cavosurface treatment on marginal leakage in class V composite resin restorations. J Prosthet Dent 1982;47:496-501. 34. Sano H, Takatsu T, Ciucchi B, Russell CM, Pashley DH. Tensile properties of resin-infiltrated demineralized human dentin. J Dent Res 1995; 74:1093-1102. 35. Spencer P, Swafford JR. Unprotected protein at the dentin-adhesive interface. Quintessence Int 1999;30:501-507.

346

36. Spencer P, Wang Y, Walker MP, Wieliczka DM, Swafford JR. Interfacial chemistry of the dentin/adhesive bond. J Dent Res 2000;79:1458-1463. 37. Totiam P, Gonzalez-Cabezas C, Fontana MR, Zero DT. A new in vitro model to study the relationship of gap size and secondary caries. Caries Res 2007;41:467-473. 38. Tsuchiya S, Nikaido T, Sonoda H, Foxton RM, Tagami J. Ultrastructure of the dentin-adhesive interface after acid-base challenge. J Adhes Dent 2004;6:183-190. 39. Yazici AR, Celik C, Ozgunaltay G, Dayangac B. Bond strength of different adhesive systems to dental hard tissues. Oper Dent 2007;32:166-172. 40. Zheng L, Pereira PN, Nakajima M, Sano H, Tagami J. Relationship between adhesive thickness and microtensile bond strength. Oper Dent 2001;26:97-104.

Clinical relevance: This study shows the efficacy of different hybridization protocols based on the number of adhesive layers, with one layer providing better tensile bond strength than three.

The Journal of Adhesive Dentistry

Influence of the number of adhesive layers on adhesive interface properties under cariogenic challenge using streptococcus mutans.

To test the hypothesis that the number of adhesive layers influences the adhesive interface properties under cariogenic challenge conditions using a S...
192KB Sizes 0 Downloads 6 Views