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Effects of moisture degree and rubbing action on the immediate resin–dentin bond strength
d e n t a l m a t e r i a l s 2 2 ( 2 0 0 6 ) 1150–1156
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Effects of moisture degree and rubbing action on the immediate resin–dentin bond strength Karen Dal-Bianco a , Arlete Pellizzaro a , Rafael Patzlaft a , Jos´e Roberto de Oliveira Bauer b , Alessandro Dourado Loguercio a , Alessandra Reis a,∗ a
´ Vargas, 2125 Joac¸aba, Department of Dental Materials and Operative Dentistry, University of Oeste de Santa Catarina, Rua Getulio CEP 89600-000 SC, Brazil b Department of Dental Materials, University of Sao ˜ Paulo, Sao ˜ Paulo, SP, Brazil
a r t i c l e
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a b s t r a c t
Article history:
Objectives. To compare the effects of moisture and rubbing action on the microtensile bond
Received 31 March 2005
strength (BS) of an ethanol/water-based (Single Bond [SB]) and an acetone-based system
Received in revised form
(One-Step [OS]) to dentin.
10 September 2005
Methods. On 60 human molars, a flat superficial dentin surface was exposed by wet abra-
Accepted 18 October 2005
sion. Two coats of the adhesives were applied on either a dry (D) or rewetted surface (W), under no rubbing action (NRA), slight (SRA) or vigorous rubbing action (VRA). After light curing (600 mW/cm2 /10 s), composite build-ups were constructed incrementally and specimens
Keywords:
were stored in water (37 ◦ C/24 h). They were longitudinally sectioned in the “x” and “y” direc-
Adhesives systems
tions to obtain bonded sticks (0.8 mm2 ) to be tested in tension at 0.5 mm/min. Resultant BS
Solvent
was expressed as an index that includes bond strength values of the different fracture pat-
Rubbing action
terns and the specimens that failed during preparation for testing. The data were analyzed
Moisture
by a three-way ANOVA and Tukey’s multiple comparison tests (95%).
Microtensile bond strength
Results. The interactions moisture/agitation and adhesive/agitation were statistically significant (p < 0.05). In D groups, the highest BS was obtained under VRA (37.11 ± 7.3). In W groups, the BS at SRA (41.82 ± 8.4) and VRA (38.89 ± 8.2) were similar. For SB system, the SRA (33.6 ± 8.3) and VRA groups (41.26 ± 5.9) yielded similar BS while for OS the VRA was essential to reach high BS (34.2 ± 8.4). Significance. High BS to dentin can be obtained, under dry conditions, when ethanol/water and acetone-based systems, are vigorously agitated in the surface. On wet dentin, slight agitation seems to be enough to provide high BS to dentin. © 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
The development of etch&rinse adhesive systems leads to important improvements in restorative procedures. However, a high failure rate of retention [1–3], marginal discoloration [4] and post-operative sensitivity have been reported with etch&rinse systems [5]. Etch&rinse adhesive
∗
systems require previous dentin demineralization with phosphoric acid and the demineralized dentin must be kept moist in order to maintain interfibrillar porosity for resin monomer infiltration [6,7]. If demineralized dentin matrix is air-dried, collagen fibrils are brought closer together resulting in a demineralized zone with reduced permeability to resin monomers [8] leading to lower immediate
Corresponding author. Tel.: +55 49 9985 9985; fax: +55 49 3551 2004. E-mail addresses: reis [email protected], reis [email protected] (A. Reis). 0109-5641/$ – see front matter © 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.dental.2005.10.010
d e n t a l m a t e r i a l s 2 2 ( 2 0 0 6 ) 1150–1156
bond strengths with current etch&rinse adhesive systems [9,10]. However, the management of adequate moisture is not easily accomplished. The discrimination of the proper moisture degree for different solvent-based adhesive systems is still a challenge, since it depends on the solvent composition [11], overall instructions’ interpretation, the drying time, tooth–air syringe distance [12] and operator skills or handling by the operator [13]. Another challenge is that the residual water and solvent from the adhesive systems should be completely removed prior to polymerization, since its entrapment within the hybrid layer may compromise the quality of the polymer within hybrid layer [14,15]. Thus, any attempt to produce an increased rate of water and solvent evaporation, such as increased application times [16], delayed polymerization [17] and adhesives’ rubbing [18], can improve the strength of the polymer formed within the collagen fibrils and allow high bond strength values. The behavior of acetone- and waterbased systems may be different depending on the clinical approach, as their vapor pressure is relatively different (ca. 200 and 47.1 mmHg, respectively) [19]. While it is clear that immediate bond strength of waterbased, three-step, etch&rinse adhesive systems to dentin can be improved by rubbing the primer into the surface [18], there is no information regarding this having any effect on the bond strength of two-step, etch&rinse adhesive systems. Therefore, the aim of the present study was to compare the effects of moisture degree and rubbing action on the microtensile bond strength of simplified etch&rinse adhesives of different solvent composition.
2.
Materials and methods
Forty-five extracted, caries-free human third molars were used. The teeth were collected after the patient’s informed ˜ Paulo Institutional Review consent. The University of Sao Board approved this study. Teeth were disinfected in 0.5% chloramine, stored in distilled water [21] and used within 6 months after extraction. A flat and superficial dentin surface was exposed on each tooth after wet grinding the occlusal enamel on #180-grit SiC paper. The enamel-free, exposed dentin surfaces were further polished on wet #600-grit silicon-carbide paper for 60 s to standardize the smear layer. An adhesive tape with a hole in its center (radius [r] = 4.1 mm) was bonded on the dentin surface before adhesive application. The area for bonding (r2 ) was calculated, being approximately 52 mm2 . Two different solvent-based, etch&rinse adhesive systems were tested: Single Bond (SB—3M ESPE, St. Paul, MN, USA), an ethanol/water-based system and One-Step (OS—Bisco, Schaumburg, IL, USA), an acetone-based system. Their composition, application mode and batch number are given in Table 1. The acid etching was performed with the respective acids of the different adhesives (Table 1). Then, contrary to the manufacturer’s instructions, the surfaces were rinsed with distilled water for 15 s and air-dried for 30 s with oil-free compressed air to collapse the collagen fibers. The adhesives
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were applied on the surface that was either kept dried or rewetted for 10 s with different amounts of distilled water (1.5 or 3.5 l, for SB and OS, respectively), measured with a micropipette (Pipetman, Gilson, NY, USA) [11]. These differences in the amount of water used to rewet the collapsed demineralized dentin are due to differences in the vapor pressure and Hansen’s solubility parameters from the solvents employed in each adhesive system [11]. The adhesives were applied on the dentin surfaces as follows: (1) No rubbing action (NRA): In this group, the adhesive only was spread over the entire surface for approximately 3 s and left undisturbed for 7 s. Then, an air stream was applied for 10 s at a distance of 20 cm. (2) Slight rubbing action (SRA): The adhesive was lightly spread on the entire surface for approximately 10 s; however, no intentional manual pressure was exerted on the microbrush. Before performing the adhesive application, the operator trained on the surface of an analytical balance to determine the equivalent manual pressure that would be placed on the surface of the demineralized dentin (Mettler, type H6; Columbus, OH, USA). For this group, the pressure was equivalent to approximately 4.0 ± 1.0 g. An air stream was applied for 10 s at a distance of 20 cm. (3) Vigorous rubbing action (VRA): The adhesive was rigorously agitated on the entire dentin surface for approximately 10 s. The microbrush was scrubbed on the dentin surface under manual pressure (equivalent to approximately 34.5 ± 6.9 g). An air stream was applied for 10 s at a distance of 20 cm. In all these three groups, a second coat of adhesive layer was applied in the same manner as for the first layer. The time lapse from the beginning of the adhesive application and light curing (VIP, Bisco; 600 mW/cm2 ) was approximately 40 s. The light curing was performed for the respective recommended time (10 s). Resin composite build-ups (Z250, 3M ESPE) were placed on the bonded surfaces (1 mm increments) that were individually light activated for 30 s each. All bonding procedures were carried out by a single operator at 24 ◦ C and 50% relative humidity [23], since variations on relative humidity and temperature can affect the bond strength values. Five teeth were used for each combination of adhesive system and surface moisture. After storage of the bonded teeth in distilled water at 37 ◦ C for 24 h, they were longitudinally sectioned in both “x” and “y” directions across the bonded interface with a diamond saw in a Labcut 1010 machine (Extec Corp., Enfield, CT, USA), under water cooling at 300 rpm [20] to obtain bonded sticks with a cross-sectional area of approximately 0.8 mm2 . The number of premature debonded sticks (D) per tooth during specimen preparation was recorded. The crosssectional area of each stick was measured with the digital caliper to the nearest 0.01 mm and recorded for subsequent calculation of the BS (Absolute Digimatic, Mitutoyo, Tokyo, Japan). Individual bonded sticks were attached to a modified device for microtensile testing [24] with cyanoacrylate resin (Zapit, Dental Ventures of North America, Corona, CA, USA) and sub˜ Jose´ dos Pinhais, PR, Brazil) jected to a tensile force (Emic, Sao
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Table 1 – Adhesive systems: composition, application mode and batch number Adhesive systems
Composition
Single Bond (3M ESPE)
Application mode
1. Scotchbond—35% phosphoric acid 2. Adhesive—Bis-GMA, HEMA, dimethacrylates, polyalquenoic acid copolymer, initiators, water and ethanol 1. Uni-etch—32% phosphoric acid 2. Adhesive—Bis-GMA, BPDM, HEMA, initiator and acetone
One-Step (Bisco)
Batch number
a, b, c, d, e, f, e, f, g
9CX
a, b, c, d, e, f, e, f, g
CE0459
a: acid-etch (15 s); b: rinse (15 s); c: air-dry (30 s); d: dentin kept dry or rewetted with water (1.5 l for SB and 3.5 l for OS); e: one coat of adhesive; f: air-dry for 10 s at 20 cm; g: light-cure (10 s, 600 mW/cm2 ).
Table 2 – Percentage of specimens (%) from the Single Bond adhesive distributed according to the fracture pattern mode and the premature debonded specimens Rubbing action
NRA SRA VRA
Dry
Wet
A/M
C
Debonded
A/M
C
Debonded
49.1 92 100
0 0 0
50.9 8 0
69.4 94.7 100
0 0 0
30.6 5.3 0
A/M: adhesive/mixed fracture mode; C: cohesive failure within dentin or composite resin.
at 0.5 mm/min. The failure modes were evaluated at 400× (HMV-2, Shimadzu, Tokyo, Japan) and classified as cohesive (C, failure exclusive within dentin or resin composite), adhesive (A, failure at resin/dentin interface), or adhesive/mixed (A/M, failure at resin/dentin interface that included cohesive failure of the neighboring substrates). The experimental unit in this study was the tooth [22]. A bond strength index (BS) was calculated for each tooth used per group as described by Reis et al. [20]. The BS index is a weighted mean assuming the relative contribution of the possible mode of failures. The cohesive strength of the resin composite and the cohesive strength of dentin are considered as the average value of all the specimens (from a single tooth) that failed in that manner. The prematurely debonded specimens were included in the BS index. The average value attributed to specimens that failed prematurely during preparation is arbitrary, and corresponds to approximately half of the minimum bond strength value that could be measured in this study (ca. 7.6 MPa). The microtensile BS indexes were subjected to a three-way repeated measures analysis of variance (adhesive/moisture degree/rubbing action) and a post hoc test (Tukey’s test at ˛ = 0.05) was used for pair-wise comparisons.
3.
Results
Approximately 25–30 sticks could be obtained per tooth, including those with premature debonding. The mean crosssectional area ranged from 0.78 to 0.89 mm2 and no differences among the groups were detected (p > 0.05). The percentage of specimens that showed premature debonding during specimen preparation and the frequency of each fracture pattern mode are shown in Tables 2 and 3. Regardless of the moisture condition, SB showed a very low percentage of premature debonded specimens when the adhesive was rubbed on the surface (Table 2). OS showed a similar pattern after rubbing action; however, SB had a lower rate of pre-testing failure than OS (Table 3). No cohesive fracture either in composite resin or dentin was observed in this study; therefore, only the premature debonded specimens were included in the bond strength indexes. The overall microtensile bond strength indexes are demonstrated in Table 4. The interaction adhesive/moisture degree/rubbing action and the subject factor adhesive were not significant (p > 0.05). The interaction moisture degree/rubbing action and adhesive/rubbing action was
Table 3 – Percentage of specimens (%) from the One-Step adhesive distributed according to the fracture pattern mode and the premature debonded specimens Rubbing action
NRA SRA VRA
Dry
Wet
A/M
C
Debonded
A/M
C
53 85 87.3
0 0 0
47 15 12.7
25.9 70.7 63.5
0 0 0
A/M: adhesive/mixed fracture mode; C: cohesive failure within dentin or composite resin.
Debonded 74.1 29.3 36.5
d e n t a l m a t e r i a l s 2 2 ( 2 0 0 6 ) 1150–1156
Table 4 – Overall microtensile bond strength indexes and the respective standard deviations (MPa) obtained in each experimental condition Adhesive
Moisture
Rubbing action NRA
SRA
VRA
SB
Wet Dry
10.2 [2.1] 8.5 [1.8]
41.7 [6.2] 25.4 [0.9]
42.5 [2.3] 40.4 [2.5]
OS
Wet Dry
11.1 [4.1] 21.2 [2.3]
40.7 [4.5] 18.4 [1.1]
35.3 [5.0] 33.3 [2.6]
Table 5 – Means and standard deviations of resin–dentin bond strength indexes (MPa) under different conditions of moisture degree and rubbing action Moisture
Dry Moist
Rubbing action NRA
SRA
VRA
14.11 [7.8]c,b 10.58 [6.1]c
21.94 [4.3]c,b 41.22 [8.4]a
37.11 [7.3]a 38.89 [8.2]a
Same superscript letters (a–c) indicate no significant difference between means (p > 0.05).
Table 6 – Means and standard deviations of resin–dentin bond strength indexes (MPa) under different conditions of adhesive and rubbing action Adhesive
Rubbing action NRA
SB OS
9.3 [4.1]c 16.1 [8.2]c
SRA
VRA
33.6 [8.3]a,b 29.6 [8.9]b,c
41.26 [5.9]a 34.2 [8.4]a,b
Same superscript letters (a–c) indicate no significant difference between means (p > 0.05).
statistically significant (p = 0.015 and <0.0001, respectively). The means and the respective standard deviations of the bond strength indexes (BS) for the mentioned significant interactions are shown in Tables 5 and 6. Referring to Table 5, one can observe that in dry groups, the highest bond strength values were obtained when the adhesive was vigorously rubbed on dentin. When the dentin was kept moist, both the light and the vigorous rubbing action provided high resin–dentin bond strength values (p < 0.05). The results presented in Table 6 demonstrate that for SB, both light and vigorous rubbing actions increase the resin–dentin microtensile bond strength, while for OS, an increase to the level reached for SB is only accomplished with vigorous rubbing action.
4.
Discussion
It was recently demonstrated that the amount of water required to maximize BS was different among the adhesive systems available in the market. While the acetone-based adhesive (OS) required a wetter surface (ca. 3.5 l of water), the water-based systems obtained higher BS on a drier sur-
1153
face (ca. 1.5 l of water) [11]. When dentin is air-dried and collapsed, collagen fibrils contact each other and establish hydrogen bonds (H-bonds), reducing the permeability to adhesive resins [25]. This condition was created in this study by altering the manufacturer’s directions after the phosphoric acid etching step, in which the demineralized dentin was severely air-dried for 30 s. To recreate the interfibrillar spaces for resin infiltration, the monomer/solvent combination of the adhesive must be able to break such interpeptide Hbonds and permit the matrix to re-expand [26]. Only solvents with a solubility parameter for hydrogen bonding (␦h) higher than 19.0 (J/cm3 )1/2 are capable of breaking the interpeptide H-bonds and re-expand the matrix [27]. Water has a ␦h of 37.3 (Hansen’s solubility parameter, while acetone has a ␦h of only 7.0 [28]). This explains why a higher amount of water was used to re-hydrate the air-dried, demineralized dentin for the acetone-based system. The results of this study indicate that the light or vigorous rubbing action of water/alcohol and acetone adhesives is essential to provide a high immediate bond strength to dentin. Good infiltration in total-etched, wet bonding specimens can be obtained if the adhesive resin replaces all the water within the demineralized matrix that was previously occupied by mineral, without collapse of the collagen matrix. Defects in resin impregnation and imperfect polymerization of the adhesive resin can create water-rich and stress concentration zones that might reduce the resin–dentin bonds and leave the interface susceptible to water degradation over time [29,30]. Under a moist condition, the demineralized dentin preserves the nanospaces within collagen fibrils [25], into which the adhesive monomers must diffuse to envelope the collagen fibrils prior to polymerization. Using manufacturers’ protocols, resin monomers, mainly those with high molecular weight from simplified etch&rinse adhesives, have limited diffusion into the wet demineralized dentin [31–33]. It is likely that a slight and vigorous rubbing action can increase the moieties kinetics and allow better monomer diffusion inward, while solvents are diffusing outward. The removal of residual water or solvents increases the mechanical properties of the resin inside the hybrid layer [14,34]. For instance, a water-free HEMA-based adhesive resin had its degree of conversion reduced by 50% when as little as 20 l/ml of water was added to the adhesive [15]. Probably, the presence of residual water during polymerization precludes the formation of a high cross-linked polymer resulting in poor polymerized bonding resin [14]. This is the same mechanism underlying the improvements in bond strengths that occur after the application of multiple coats of etch&rinse simplified adhesives before light curing [35] or after prolonged adhesive application time [16,17]. These three clinical approaches might allow removal of more water from the interfibrillar spaces and increase the inward diffusion of hydrophilic and hydrophobic adhesive monomers. When demineralized dentin is air-dried, the water within the collagen matrix is removed and collagen fibrils are brought into close contact. They form weak interpeptide bonds that render the matrix to shrink, stiffen [36,27] and become practically impermeable to resin adhesives [6–8,37]. In fact, the infiltration ratio of the bonding resin within the hybrid layer for acetone-based systems is reduced by 50% when applied
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to dry instead of wet dentin [31]. This is responsible for the low resin–dentin bond strengths observed when adhesives are applied on air-dried, demineralized dentin [10,11]. It is thought that the only way to revert such an undesirable situation is by applying a solution that can break such interpeptide bonds and re-expand the collagen matrix. Acetone and resin monomers are not capable of re-expanding airdried dentin under static conditions [26,27], since they have a solubility parameter for hydrogen bonding lower than the binding forces of collagen fibrils in a dried condition. Interestingly, this study showed that the vigorous rubbing action increased the BS for both adhesives. Although Pashley et al. [27] have observed that the percentage of re-expansion of shrunk, demineralized dentin with HEMA/solvents mixtures is rather lower than with water, these mixtures were left undisturbed for approximately 8 min. The authors of this study believe that if the solutions in the study of Pashley et al. [27] had been rubbed on the demineralized dentin specimens, a higher re-expansion percentage could have been observed. This hypothesis is based on the assumption that the Hansen’s solubility for hydrogen bonding is not a property of a solution, since this solubility parameter is dependent on the entropy of the mixture. In other words, it can be said that the higher the disorder (entropy) of the mixture, the higher are Hansen’s solubility parameters. The entropy of the solution can be increased by increasing heat, polymer concentration [28] and also by agitation of the solution provided in this study by rubbing action of the adhesive on the demineralized surface. Other factors however could have played a role in the results mentioned. The mechanical pressure applied to the demineralized dentin surface during the rubbing action might compress the collagen network like a sponge. As the pressure is relieved the compressed collagen expands and the adhesive solution may be drawn into the collapsed collagen mesh [18]. This hypothesis, however, should be further investigated. Contrary to results of the current study, Jacobsen and ¨ Soderholm [18] reported low dentin-bond strength when an acetone-based primer was rubbed on demineralized dentin. The authors claimed that the rubbing action could increase the acetone evaporation rate to such a degree that adhesive liquid would drastically reduce its flow and form a HEMA jelly-like structure, not capable of infiltrating the nanospaces within collagen fibrils. Surprisingly, the present investigation demonstrated a significant improvement in bond strength values when an acetone-based system was rubbed on the dentin surface, mainly under pressure (vigorous rubbing action). Differences in the methods employed and testing adhesives can be blamed for this controversy and further studies are necessary to reach a consensus on this matter. Cho and Dickens [34] observed that the higher the amount of acetone concentration in an adhesive solution, the lower are the resin–dentin bond strengths. For instance, an experimental primer with 67% of acetone showed a 27% decrease in the bond strength values when compared with a primer containing 27% of acetone. The amount of acetone in the experimental ¨ primer in the study of Jacobsen and Soderholm [18] was 65% which is higher than the amount of acetone present in the One-Step system used in this study. Although the relation between acetone concentration and adhesive application is
not clear, this fact is another evidence of differences between ¨ the Jacobsen and Soderholm study [18] and this one. The wet bonding technique has been recommended for dentin bonding for more than 10 years [9,38]. The rationale behind this is that, as long as dentin is kept fully hydrated, the dentin matrix does not collapse and free space is available for resin infiltration [8,39]. Based on such rationale and on immediately higher bond strengths obtained under wet-bonding conditions [10,11], more hydrophilic monomers and solvents were included in the composition of most adhesive systems currently available on the market, turning dental adhesives into permeable membranes that are highly susceptible to the degrading effects of water [40–43]. This phenomenon of increased adhesive permeability is similar to what was previously reported for single-step self-etch adhesives [44] and appears to be a characteristic of simplified adhesives. This is probably caused by the absence of a more hydrophobic bonding resin layer that is employed in three-step etch&rinse and two-step self-etch adhesives. In fact, in a recent systematic review of the literature, Peumans et al. [45] demonstrated that simplified adhesive systems appear to induce loss of effectiveness. The results of this study show that bonding to demineralized and air-dried dentin can be an option in order to reduce the amount of water entrapped within the hybrid layer. As long as adhesives are rubbed on to the dentin surface, high immediate bond strengths, similar to the ones obtained under wet bonding, can be obtained. Moreover, it was recently demonstrated that the bonding of etch&rinse two-step systems over demineralized, air-dried dentin seems to be more stable over time [46] which can be attributed to the lower content of water entrapped within the hybrid layer. In the long run this can reduce the observable degradation to which the current adhesive systems are prone [46–50]. In summary, it may be concluded that high bond strength to dentin can be obtained under dry conditions when ethanol/water and acetone-based systems are vigorously rubbed on the demineralized dentin surface. On wet dentin, a light-rubbing action seems to be enough to provide high bond strength to dentin.
Acknowledgements This study was partially supported by School of Dentistry, University of Oeste de Santa Catarina, and also by CNPq grants 302552/2003-0 and 305870/2004-1.
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[26] Pashey DH, Carvalho RM, Tay FR, Agee KA, Lee KW. Solvation of dried dentin matrix by water and other polar solvents. Am J Dent 2002;15:97–102. [27] Pashley DH, Agee KA, Nakajima M, Tay FR, Carvalho RM, Terada RS, et al. Solvent-induced dimensional changes in EDTA-demineralized dentin matrix. J Biomed Mater Res 2001;56:273–81. [28] Barton AFM. Handbook of solubility parameters and other cohesion parameters. Boca Raton, FL: CRC Press Inc.; 1983. [29] Sano H, Yoshikawa T, Pereira PNR, Kanemura N, Morigami M, Tagami J, et al. Long-term durability of dentin bonds made with a self-etching primer, in vivo. J Dent Res 1999;78:906–11. [30] Tay FR, Pahsley DH, Yoshiyama M. Two modes of nanoleakage expression in single-step adhesives. J Dent Res 2002;81:472–6. [31] Hashimoto M, Ohno H, Kaga M, Sano H, Endo K, Sano H, et al. The extent to which resin can infiltrate dentin by acetone-based adhesives. J Dent Res 2002;81:74–8. [32] Miyasaki M, Onose H, Moore BK. Analysis of the dentin–resin interface by use of laser Raman spectroscopy. Dent Mater 2002;18:576–80. [33] Wang Y, Spencer P. Hybridization efficiency of the adhesive/dentin interface with wet bonding. J Dent Res 2003;82:141–5. [34] Cho B, Dickens SH. Effects of the acetone content of single solution dentin bonding agents on the adhesive layer thickness and the microtensile bond strength. Dent Mater 2004;20:107–15. [35] Hashimoto M, Sano H, Yoshida E, Hori M, Kaga M, Oguchi H, et al. Effects of multiple adhesive coatings on dentin bonding. Oper Dent 2004;29:416–23. [36] Maciel KT, Carvalho RM, Ringle RD, Preston CD, Russel CM, Pashley DH. The effects of acetone, ethanol, HEMA, and air on the stiffness of human decalcified dentin matrix. J Dent Res 1996;11:1851–8. [37] Eick JD, Robinson SJ, Chappell RP, Cobb CM, Spencer P. The dentinal surface: its influence on dentinal adhesion. Part III. Quintessence Int 1993;24:571–82. [38] Gwinnett AJ. Moist versus dry dentin: its effect on shear bond strength. Am J Dent 1992;5:127–9. [39] Carvalho RM, Yoshiyama M, Brewer PD, Pashley DH. Dimensional changes of demineralized human dentine during preparation for scanning electron microscopy. Arch Oral Biol 1996;41:379–86. [40] Tay FR, Pashley DH, Suh BI, Carvalho RM, Itthagarun A. Single-step adhesives are permeable membranes. J Dent 2002;30:371–82. [41] Tay FR, Pashley DH. Water treeing—a potential mechanism for degradation of dentin adhesives. Am J Dent 2003;16:6–12. ¨ [42] Carrilho MRO, Tay FR, Pashley DH, Tjaderhane L, Carvalho RM. Mechanical stability of resin–dentin bond components. Dent Mater 2005;21:232–41. [43] Tay FR, Frankenberger R, Krejci I, Bouillaguet S, Pashley DH, Carvalho RM, et al. Single bottle adhesives behave as permeable membranes after polymerisation. I. In vivo evidence. J Dent 2004;32:611–21. [44] Tay FR, Pashley DH, Suh B, Carvalho R, Miller M. Single-step, self-etch adhesives behave as permeable membranes after polymerisation. Part I. Bond strength and morphologic evidence. Am J Dent 2004;17:271–8. [45] Peumans M, Kanumilli P, De Munck J, Van Landuyt K, Lambrechts P, Van Meerbeek B. Clinical effectiveness of contemporary adhesives: a systematic review of current clinical trials. Dent Mater 2005;21:864–81. [46] Reis A, Loguercio AD, Carvalho RM, Grande RHM. Durability of resin–dentin interfaces: effects of moisture and adhesive solvent component. Dent Mater 2004;20:669–76.
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available at www.sciencedirect.com
journal homepage: www.intl.elsevierhealth.com/journals/dema
Effects of moisture degree and rubbing action on the immediate resin–dentin bond strength Karen Dal-Bianco a , Arlete Pellizzaro a , Rafael Patzlaft a , Jos´e Roberto de Oliveira Bauer b , Alessandro Dourado Loguercio a , Alessandra Reis a,∗ a
´ Vargas, 2125 Joac¸aba, Department of Dental Materials and Operative Dentistry, University of Oeste de Santa Catarina, Rua Getulio CEP 89600-000 SC, Brazil b Department of Dental Materials, University of Sao ˜ Paulo, Sao ˜ Paulo, SP, Brazil
a r t i c l e
i n f o
a b s t r a c t
Article history:
Objectives. To compare the effects of moisture and rubbing action on the microtensile bond
Received 31 March 2005
strength (BS) of an ethanol/water-based (Single Bond [SB]) and an acetone-based system
Received in revised form
(One-Step [OS]) to dentin.
10 September 2005
Methods. On 60 human molars, a flat superficial dentin surface was exposed by wet abra-
Accepted 18 October 2005
sion. Two coats of the adhesives were applied on either a dry (D) or rewetted surface (W), under no rubbing action (NRA), slight (SRA) or vigorous rubbing action (VRA). After light curing (600 mW/cm2 /10 s), composite build-ups were constructed incrementally and specimens
Keywords:
were stored in water (37 ◦ C/24 h). They were longitudinally sectioned in the “x” and “y” direc-
Adhesives systems
tions to obtain bonded sticks (0.8 mm2 ) to be tested in tension at 0.5 mm/min. Resultant BS
Solvent
was expressed as an index that includes bond strength values of the different fracture pat-
Rubbing action
terns and the specimens that failed during preparation for testing. The data were analyzed
Moisture
by a three-way ANOVA and Tukey’s multiple comparison tests (95%).
Microtensile bond strength
Results. The interactions moisture/agitation and adhesive/agitation were statistically significant (p < 0.05). In D groups, the highest BS was obtained under VRA (37.11 ± 7.3). In W groups, the BS at SRA (41.82 ± 8.4) and VRA (38.89 ± 8.2) were similar. For SB system, the SRA (33.6 ± 8.3) and VRA groups (41.26 ± 5.9) yielded similar BS while for OS the VRA was essential to reach high BS (34.2 ± 8.4). Significance. High BS to dentin can be obtained, under dry conditions, when ethanol/water and acetone-based systems, are vigorously agitated in the surface. On wet dentin, slight agitation seems to be enough to provide high BS to dentin. © 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
The development of etch&rinse adhesive systems leads to important improvements in restorative procedures. However, a high failure rate of retention [1–3], marginal discoloration [4] and post-operative sensitivity have been reported with etch&rinse systems [5]. Etch&rinse adhesive
∗
systems require previous dentin demineralization with phosphoric acid and the demineralized dentin must be kept moist in order to maintain interfibrillar porosity for resin monomer infiltration [6,7]. If demineralized dentin matrix is air-dried, collagen fibrils are brought closer together resulting in a demineralized zone with reduced permeability to resin monomers [8] leading to lower immediate
Corresponding author. Tel.: +55 49 9985 9985; fax: +55 49 3551 2004. E-mail addresses: reis [email protected], reis [email protected] (A. Reis). 0109-5641/$ – see front matter © 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.dental.2005.10.010
d e n t a l m a t e r i a l s 2 2 ( 2 0 0 6 ) 1150–1156
bond strengths with current etch&rinse adhesive systems [9,10]. However, the management of adequate moisture is not easily accomplished. The discrimination of the proper moisture degree for different solvent-based adhesive systems is still a challenge, since it depends on the solvent composition [11], overall instructions’ interpretation, the drying time, tooth–air syringe distance [12] and operator skills or handling by the operator [13]. Another challenge is that the residual water and solvent from the adhesive systems should be completely removed prior to polymerization, since its entrapment within the hybrid layer may compromise the quality of the polymer within hybrid layer [14,15]. Thus, any attempt to produce an increased rate of water and solvent evaporation, such as increased application times [16], delayed polymerization [17] and adhesives’ rubbing [18], can improve the strength of the polymer formed within the collagen fibrils and allow high bond strength values. The behavior of acetone- and waterbased systems may be different depending on the clinical approach, as their vapor pressure is relatively different (ca. 200 and 47.1 mmHg, respectively) [19]. While it is clear that immediate bond strength of waterbased, three-step, etch&rinse adhesive systems to dentin can be improved by rubbing the primer into the surface [18], there is no information regarding this having any effect on the bond strength of two-step, etch&rinse adhesive systems. Therefore, the aim of the present study was to compare the effects of moisture degree and rubbing action on the microtensile bond strength of simplified etch&rinse adhesives of different solvent composition.
2.
Materials and methods
Forty-five extracted, caries-free human third molars were used. The teeth were collected after the patient’s informed ˜ Paulo Institutional Review consent. The University of Sao Board approved this study. Teeth were disinfected in 0.5% chloramine, stored in distilled water [21] and used within 6 months after extraction. A flat and superficial dentin surface was exposed on each tooth after wet grinding the occlusal enamel on #180-grit SiC paper. The enamel-free, exposed dentin surfaces were further polished on wet #600-grit silicon-carbide paper for 60 s to standardize the smear layer. An adhesive tape with a hole in its center (radius [r] = 4.1 mm) was bonded on the dentin surface before adhesive application. The area for bonding (r2 ) was calculated, being approximately 52 mm2 . Two different solvent-based, etch&rinse adhesive systems were tested: Single Bond (SB—3M ESPE, St. Paul, MN, USA), an ethanol/water-based system and One-Step (OS—Bisco, Schaumburg, IL, USA), an acetone-based system. Their composition, application mode and batch number are given in Table 1. The acid etching was performed with the respective acids of the different adhesives (Table 1). Then, contrary to the manufacturer’s instructions, the surfaces were rinsed with distilled water for 15 s and air-dried for 30 s with oil-free compressed air to collapse the collagen fibers. The adhesives
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were applied on the surface that was either kept dried or rewetted for 10 s with different amounts of distilled water (1.5 or 3.5 l, for SB and OS, respectively), measured with a micropipette (Pipetman, Gilson, NY, USA) [11]. These differences in the amount of water used to rewet the collapsed demineralized dentin are due to differences in the vapor pressure and Hansen’s solubility parameters from the solvents employed in each adhesive system [11]. The adhesives were applied on the dentin surfaces as follows: (1) No rubbing action (NRA): In this group, the adhesive only was spread over the entire surface for approximately 3 s and left undisturbed for 7 s. Then, an air stream was applied for 10 s at a distance of 20 cm. (2) Slight rubbing action (SRA): The adhesive was lightly spread on the entire surface for approximately 10 s; however, no intentional manual pressure was exerted on the microbrush. Before performing the adhesive application, the operator trained on the surface of an analytical balance to determine the equivalent manual pressure that would be placed on the surface of the demineralized dentin (Mettler, type H6; Columbus, OH, USA). For this group, the pressure was equivalent to approximately 4.0 ± 1.0 g. An air stream was applied for 10 s at a distance of 20 cm. (3) Vigorous rubbing action (VRA): The adhesive was rigorously agitated on the entire dentin surface for approximately 10 s. The microbrush was scrubbed on the dentin surface under manual pressure (equivalent to approximately 34.5 ± 6.9 g). An air stream was applied for 10 s at a distance of 20 cm. In all these three groups, a second coat of adhesive layer was applied in the same manner as for the first layer. The time lapse from the beginning of the adhesive application and light curing (VIP, Bisco; 600 mW/cm2 ) was approximately 40 s. The light curing was performed for the respective recommended time (10 s). Resin composite build-ups (Z250, 3M ESPE) were placed on the bonded surfaces (1 mm increments) that were individually light activated for 30 s each. All bonding procedures were carried out by a single operator at 24 ◦ C and 50% relative humidity [23], since variations on relative humidity and temperature can affect the bond strength values. Five teeth were used for each combination of adhesive system and surface moisture. After storage of the bonded teeth in distilled water at 37 ◦ C for 24 h, they were longitudinally sectioned in both “x” and “y” directions across the bonded interface with a diamond saw in a Labcut 1010 machine (Extec Corp., Enfield, CT, USA), under water cooling at 300 rpm [20] to obtain bonded sticks with a cross-sectional area of approximately 0.8 mm2 . The number of premature debonded sticks (D) per tooth during specimen preparation was recorded. The crosssectional area of each stick was measured with the digital caliper to the nearest 0.01 mm and recorded for subsequent calculation of the BS (Absolute Digimatic, Mitutoyo, Tokyo, Japan). Individual bonded sticks were attached to a modified device for microtensile testing [24] with cyanoacrylate resin (Zapit, Dental Ventures of North America, Corona, CA, USA) and sub˜ Jose´ dos Pinhais, PR, Brazil) jected to a tensile force (Emic, Sao
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d e n t a l m a t e r i a l s 2 2 ( 2 0 0 6 ) 1150–1156
Table 1 – Adhesive systems: composition, application mode and batch number Adhesive systems
Composition
Single Bond (3M ESPE)
Application mode
1. Scotchbond—35% phosphoric acid 2. Adhesive—Bis-GMA, HEMA, dimethacrylates, polyalquenoic acid copolymer, initiators, water and ethanol 1. Uni-etch—32% phosphoric acid 2. Adhesive—Bis-GMA, BPDM, HEMA, initiator and acetone
One-Step (Bisco)
Batch number
a, b, c, d, e, f, e, f, g
9CX
a, b, c, d, e, f, e, f, g
CE0459
a: acid-etch (15 s); b: rinse (15 s); c: air-dry (30 s); d: dentin kept dry or rewetted with water (1.5 l for SB and 3.5 l for OS); e: one coat of adhesive; f: air-dry for 10 s at 20 cm; g: light-cure (10 s, 600 mW/cm2 ).
Table 2 – Percentage of specimens (%) from the Single Bond adhesive distributed according to the fracture pattern mode and the premature debonded specimens Rubbing action
NRA SRA VRA
Dry
Wet
A/M
C
Debonded
A/M
C
Debonded
49.1 92 100
0 0 0
50.9 8 0
69.4 94.7 100
0 0 0
30.6 5.3 0
A/M: adhesive/mixed fracture mode; C: cohesive failure within dentin or composite resin.
at 0.5 mm/min. The failure modes were evaluated at 400× (HMV-2, Shimadzu, Tokyo, Japan) and classified as cohesive (C, failure exclusive within dentin or resin composite), adhesive (A, failure at resin/dentin interface), or adhesive/mixed (A/M, failure at resin/dentin interface that included cohesive failure of the neighboring substrates). The experimental unit in this study was the tooth [22]. A bond strength index (BS) was calculated for each tooth used per group as described by Reis et al. [20]. The BS index is a weighted mean assuming the relative contribution of the possible mode of failures. The cohesive strength of the resin composite and the cohesive strength of dentin are considered as the average value of all the specimens (from a single tooth) that failed in that manner. The prematurely debonded specimens were included in the BS index. The average value attributed to specimens that failed prematurely during preparation is arbitrary, and corresponds to approximately half of the minimum bond strength value that could be measured in this study (ca. 7.6 MPa). The microtensile BS indexes were subjected to a three-way repeated measures analysis of variance (adhesive/moisture degree/rubbing action) and a post hoc test (Tukey’s test at ˛ = 0.05) was used for pair-wise comparisons.
3.
Results
Approximately 25–30 sticks could be obtained per tooth, including those with premature debonding. The mean crosssectional area ranged from 0.78 to 0.89 mm2 and no differences among the groups were detected (p > 0.05). The percentage of specimens that showed premature debonding during specimen preparation and the frequency of each fracture pattern mode are shown in Tables 2 and 3. Regardless of the moisture condition, SB showed a very low percentage of premature debonded specimens when the adhesive was rubbed on the surface (Table 2). OS showed a similar pattern after rubbing action; however, SB had a lower rate of pre-testing failure than OS (Table 3). No cohesive fracture either in composite resin or dentin was observed in this study; therefore, only the premature debonded specimens were included in the bond strength indexes. The overall microtensile bond strength indexes are demonstrated in Table 4. The interaction adhesive/moisture degree/rubbing action and the subject factor adhesive were not significant (p > 0.05). The interaction moisture degree/rubbing action and adhesive/rubbing action was
Table 3 – Percentage of specimens (%) from the One-Step adhesive distributed according to the fracture pattern mode and the premature debonded specimens Rubbing action
NRA SRA VRA
Dry
Wet
A/M
C
Debonded
A/M
C
53 85 87.3
0 0 0
47 15 12.7
25.9 70.7 63.5
0 0 0
A/M: adhesive/mixed fracture mode; C: cohesive failure within dentin or composite resin.
Debonded 74.1 29.3 36.5
d e n t a l m a t e r i a l s 2 2 ( 2 0 0 6 ) 1150–1156
Table 4 – Overall microtensile bond strength indexes and the respective standard deviations (MPa) obtained in each experimental condition Adhesive
Moisture
Rubbing action NRA
SRA
VRA
SB
Wet Dry
10.2 [2.1] 8.5 [1.8]
41.7 [6.2] 25.4 [0.9]
42.5 [2.3] 40.4 [2.5]
OS
Wet Dry
11.1 [4.1] 21.2 [2.3]
40.7 [4.5] 18.4 [1.1]
35.3 [5.0] 33.3 [2.6]
Table 5 – Means and standard deviations of resin–dentin bond strength indexes (MPa) under different conditions of moisture degree and rubbing action Moisture
Dry Moist
Rubbing action NRA
SRA
VRA
14.11 [7.8]c,b 10.58 [6.1]c
21.94 [4.3]c,b 41.22 [8.4]a
37.11 [7.3]a 38.89 [8.2]a
Same superscript letters (a–c) indicate no significant difference between means (p > 0.05).
Table 6 – Means and standard deviations of resin–dentin bond strength indexes (MPa) under different conditions of adhesive and rubbing action Adhesive
Rubbing action NRA
SB OS
9.3 [4.1]c 16.1 [8.2]c
SRA
VRA
33.6 [8.3]a,b 29.6 [8.9]b,c
41.26 [5.9]a 34.2 [8.4]a,b
Same superscript letters (a–c) indicate no significant difference between means (p > 0.05).
statistically significant (p = 0.015 and <0.0001, respectively). The means and the respective standard deviations of the bond strength indexes (BS) for the mentioned significant interactions are shown in Tables 5 and 6. Referring to Table 5, one can observe that in dry groups, the highest bond strength values were obtained when the adhesive was vigorously rubbed on dentin. When the dentin was kept moist, both the light and the vigorous rubbing action provided high resin–dentin bond strength values (p < 0.05). The results presented in Table 6 demonstrate that for SB, both light and vigorous rubbing actions increase the resin–dentin microtensile bond strength, while for OS, an increase to the level reached for SB is only accomplished with vigorous rubbing action.
4.
Discussion
It was recently demonstrated that the amount of water required to maximize BS was different among the adhesive systems available in the market. While the acetone-based adhesive (OS) required a wetter surface (ca. 3.5 l of water), the water-based systems obtained higher BS on a drier sur-
1153
face (ca. 1.5 l of water) [11]. When dentin is air-dried and collapsed, collagen fibrils contact each other and establish hydrogen bonds (H-bonds), reducing the permeability to adhesive resins [25]. This condition was created in this study by altering the manufacturer’s directions after the phosphoric acid etching step, in which the demineralized dentin was severely air-dried for 30 s. To recreate the interfibrillar spaces for resin infiltration, the monomer/solvent combination of the adhesive must be able to break such interpeptide Hbonds and permit the matrix to re-expand [26]. Only solvents with a solubility parameter for hydrogen bonding (␦h) higher than 19.0 (J/cm3 )1/2 are capable of breaking the interpeptide H-bonds and re-expand the matrix [27]. Water has a ␦h of 37.3 (Hansen’s solubility parameter, while acetone has a ␦h of only 7.0 [28]). This explains why a higher amount of water was used to re-hydrate the air-dried, demineralized dentin for the acetone-based system. The results of this study indicate that the light or vigorous rubbing action of water/alcohol and acetone adhesives is essential to provide a high immediate bond strength to dentin. Good infiltration in total-etched, wet bonding specimens can be obtained if the adhesive resin replaces all the water within the demineralized matrix that was previously occupied by mineral, without collapse of the collagen matrix. Defects in resin impregnation and imperfect polymerization of the adhesive resin can create water-rich and stress concentration zones that might reduce the resin–dentin bonds and leave the interface susceptible to water degradation over time [29,30]. Under a moist condition, the demineralized dentin preserves the nanospaces within collagen fibrils [25], into which the adhesive monomers must diffuse to envelope the collagen fibrils prior to polymerization. Using manufacturers’ protocols, resin monomers, mainly those with high molecular weight from simplified etch&rinse adhesives, have limited diffusion into the wet demineralized dentin [31–33]. It is likely that a slight and vigorous rubbing action can increase the moieties kinetics and allow better monomer diffusion inward, while solvents are diffusing outward. The removal of residual water or solvents increases the mechanical properties of the resin inside the hybrid layer [14,34]. For instance, a water-free HEMA-based adhesive resin had its degree of conversion reduced by 50% when as little as 20 l/ml of water was added to the adhesive [15]. Probably, the presence of residual water during polymerization precludes the formation of a high cross-linked polymer resulting in poor polymerized bonding resin [14]. This is the same mechanism underlying the improvements in bond strengths that occur after the application of multiple coats of etch&rinse simplified adhesives before light curing [35] or after prolonged adhesive application time [16,17]. These three clinical approaches might allow removal of more water from the interfibrillar spaces and increase the inward diffusion of hydrophilic and hydrophobic adhesive monomers. When demineralized dentin is air-dried, the water within the collagen matrix is removed and collagen fibrils are brought into close contact. They form weak interpeptide bonds that render the matrix to shrink, stiffen [36,27] and become practically impermeable to resin adhesives [6–8,37]. In fact, the infiltration ratio of the bonding resin within the hybrid layer for acetone-based systems is reduced by 50% when applied
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to dry instead of wet dentin [31]. This is responsible for the low resin–dentin bond strengths observed when adhesives are applied on air-dried, demineralized dentin [10,11]. It is thought that the only way to revert such an undesirable situation is by applying a solution that can break such interpeptide bonds and re-expand the collagen matrix. Acetone and resin monomers are not capable of re-expanding airdried dentin under static conditions [26,27], since they have a solubility parameter for hydrogen bonding lower than the binding forces of collagen fibrils in a dried condition. Interestingly, this study showed that the vigorous rubbing action increased the BS for both adhesives. Although Pashley et al. [27] have observed that the percentage of re-expansion of shrunk, demineralized dentin with HEMA/solvents mixtures is rather lower than with water, these mixtures were left undisturbed for approximately 8 min. The authors of this study believe that if the solutions in the study of Pashley et al. [27] had been rubbed on the demineralized dentin specimens, a higher re-expansion percentage could have been observed. This hypothesis is based on the assumption that the Hansen’s solubility for hydrogen bonding is not a property of a solution, since this solubility parameter is dependent on the entropy of the mixture. In other words, it can be said that the higher the disorder (entropy) of the mixture, the higher are Hansen’s solubility parameters. The entropy of the solution can be increased by increasing heat, polymer concentration [28] and also by agitation of the solution provided in this study by rubbing action of the adhesive on the demineralized surface. Other factors however could have played a role in the results mentioned. The mechanical pressure applied to the demineralized dentin surface during the rubbing action might compress the collagen network like a sponge. As the pressure is relieved the compressed collagen expands and the adhesive solution may be drawn into the collapsed collagen mesh [18]. This hypothesis, however, should be further investigated. Contrary to results of the current study, Jacobsen and ¨ Soderholm [18] reported low dentin-bond strength when an acetone-based primer was rubbed on demineralized dentin. The authors claimed that the rubbing action could increase the acetone evaporation rate to such a degree that adhesive liquid would drastically reduce its flow and form a HEMA jelly-like structure, not capable of infiltrating the nanospaces within collagen fibrils. Surprisingly, the present investigation demonstrated a significant improvement in bond strength values when an acetone-based system was rubbed on the dentin surface, mainly under pressure (vigorous rubbing action). Differences in the methods employed and testing adhesives can be blamed for this controversy and further studies are necessary to reach a consensus on this matter. Cho and Dickens [34] observed that the higher the amount of acetone concentration in an adhesive solution, the lower are the resin–dentin bond strengths. For instance, an experimental primer with 67% of acetone showed a 27% decrease in the bond strength values when compared with a primer containing 27% of acetone. The amount of acetone in the experimental ¨ primer in the study of Jacobsen and Soderholm [18] was 65% which is higher than the amount of acetone present in the One-Step system used in this study. Although the relation between acetone concentration and adhesive application is
not clear, this fact is another evidence of differences between ¨ the Jacobsen and Soderholm study [18] and this one. The wet bonding technique has been recommended for dentin bonding for more than 10 years [9,38]. The rationale behind this is that, as long as dentin is kept fully hydrated, the dentin matrix does not collapse and free space is available for resin infiltration [8,39]. Based on such rationale and on immediately higher bond strengths obtained under wet-bonding conditions [10,11], more hydrophilic monomers and solvents were included in the composition of most adhesive systems currently available on the market, turning dental adhesives into permeable membranes that are highly susceptible to the degrading effects of water [40–43]. This phenomenon of increased adhesive permeability is similar to what was previously reported for single-step self-etch adhesives [44] and appears to be a characteristic of simplified adhesives. This is probably caused by the absence of a more hydrophobic bonding resin layer that is employed in three-step etch&rinse and two-step self-etch adhesives. In fact, in a recent systematic review of the literature, Peumans et al. [45] demonstrated that simplified adhesive systems appear to induce loss of effectiveness. The results of this study show that bonding to demineralized and air-dried dentin can be an option in order to reduce the amount of water entrapped within the hybrid layer. As long as adhesives are rubbed on to the dentin surface, high immediate bond strengths, similar to the ones obtained under wet bonding, can be obtained. Moreover, it was recently demonstrated that the bonding of etch&rinse two-step systems over demineralized, air-dried dentin seems to be more stable over time [46] which can be attributed to the lower content of water entrapped within the hybrid layer. In the long run this can reduce the observable degradation to which the current adhesive systems are prone [46–50]. In summary, it may be concluded that high bond strength to dentin can be obtained under dry conditions when ethanol/water and acetone-based systems are vigorously rubbed on the demineralized dentin surface. On wet dentin, a light-rubbing action seems to be enough to provide high bond strength to dentin.
Acknowledgements This study was partially supported by School of Dentistry, University of Oeste de Santa Catarina, and also by CNPq grants 302552/2003-0 and 305870/2004-1.
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