Microtensile bond strength of a filled vs unfilled adhesive to dentin ...
Microtensile bond strength of a filled vs unfilled adhesive to dentin ... Microtensile bond strength of a filled vs unfilled adhesive to dentin ...
284 Introduction Resin composites with adhesive materials have been available on the dental market for about four decades and are widely used for both anterior and posterior restorations due to the esthetic demands of patients, however they still have some undesirable properties. One is the polymerization shrinkage which produces contraction stresses generally concentrate at the bonding interface. 1 If these stresses exceed the bond strength to dentin, an interfacial gap will be formed, leading to bacterial infiltration, sensitivity, secondary caries and possible pulpal damage. 2 Thicker adhesive layers or liners may act as an elastic intermediate layer (elastic cavity wall) between the cavity walls and the adjacent composite. That is, they could resist the polymerization shrinkage stress of the resin composites 1 and absorb the shock produced by occlusal loads and thermal cycling. 3 Using unfilled adhesives, thicker layers are not recommended because these materials have lower mechanical properties and usually provide no radioopacity which could mislead clinicians to interprete the adhesive radiotransparency as gap formation or recurrent caries at the margin of the restoration. 4 Based on this idea, filled adhesives have been introduced, 5–7 which have included various types of fillers; such as conventional glass, ion leachable glass, silica and nanometer-sized aerosil silica fillers. 8–10 They have been reported to improve marginal and internal seal of composite restorations 6,11–13 and have sufficient radioopacity to be discernible on dental X-ray films. 7 Current adhesive systems employ two simplified application procedures to achieve the goal of micromechanical retention between resin and dentin. The first method attempts to remove the smear layer completely via acid etching and rinsing, followed by the application of an adhesive agent on a wet dentin surface; the total-etch technique. 14 The second category is the self-etch technique, which simultaneously demineralizes dentin and infiltrates it with adhesive monomers. 15 The strong versions of self-etch adhesives can completely dissolve or disperse smear layers, forming thick hybrid layers in intact dentin that approach those Conclusion: The filled adhesive One-Step Plus did not show any beneficial effect than the unfilled adhesive One-Step on the mTBS to dentin with total-etch and self-etch techniques. Irrespective from the adhesive type, self-etch technique revealed lower bond strengths than the total-etch technique. Q 2005 Elsevier Ltd. All rights reserved. achieved with conventional total-etch technique. Conversely, intermediate strong and mild versions incorporate smear layers as part of the bonded interface, forming only thin hybrid layers. 16 Both total and self-etch approaches rely on the impregnation and polymerization of the monomers into the exposed collagen of the demineralized dentin surfaces, creating a hybrid layer and the stabilization of the hybrid layer was established by the adhesive. 17 Recently, in comparison to the totaletch adhesives two-step self-etch adhesives are becoming increasingly popular, because of the reduced post-operative 18 and technique sensitivity. 16 In addition to these, they are less likely to result in a discrepancy between the depth of demineralization and the depth of resin infiltration 19 since both processes occur simultaneously. 15 Using total-etch systems, fillers incorporated in adhesive resins may increase the adhesive viscosity, resulting in a reduction in adhesive penetration into the demineralized dentin and bonding to dentin. 20,21 There is however, less information on the effect of the filled adhesives on the bonding of two-step self-etch systems to dentin. The purpose of this study was to evaluate the effect of a filled adhesive (One-Step Plus; Bisco) versus an unfilled adhesive (One-Step; Bisco) on the microtensile bond strength (mTBS) to dentin using total-etch (Uni-etch; Bisco) and self-etch (Tyrian SPE; Bisco) techniques. Material and methods E. Can Say et al. The materials and their compositions used in this study are listed in Table 1. Twenty non-carious extracted human third molars, stored in isotonic saline with thymol crystals at 4 8C, were ground flat using 180-grit silicon carbide (SiC) abrasive paper under running water to expose occlusal dentin. After the superficial dentin surfaces were polished with 600-grit SiC to standardize the smear layer, the teeth were randomly assigned to four groups according to the type of adhesive (One-Step Plus; One-Step) and technique (totaletch; self-etch) being used. Bonding procedures were performed according to the manufacturer’s
Microtensile bond strength of adhesive to dentin using self-etch and total-etch technique 285 Table 1 Materials used in the study. Materials Composition Manufacturer One-Step Plus Bis-GMA, BPDM, HEMA, CQ, p-dimethylaminobenzoic acid (co-initiator), acetone, 8.5% glass fillers Bisco Inc, USA One-Step Bis-GMA, BPDM, HEMA, acetone Bisco Inc, USA Tyrian SPE Primer A: thymol blue, ethanol, water Primer B: AMPS, BisMEP, TPO, ethanol Bisco Inc, USA Uni-etch 32% Phosphoric acid, BAC Bisco Inc, USA Clearfil AP-X Bis-GMA, TEGDMA, filler (Barium, SiO2) Kuraray Co, Japan BPDM, Biphenyl-dimethacrylate; HEMA, 2-hydroxyethyl-methacrylate; Bis-GMA, Bisphenyl-glysidyl-methacrylate; AMPS, 2- Acrylamido-2-methylpropanesulfonic acid; BisMEP, Bis(2-(methacryloyloxy)ethyl)phosphate; TEGDMA, Triethylene glycol-dimethacrylate TPO:2,4,6 (trimethylbenzoyldiphenylphosphine) oxide; BAC, Benzalkonium chloride. instructions and summarized in Table 2. Then a resin composite (Clearfil AP-X; Kuraray Medical Co, Ltd, Tokyo, Japan) was built up incrementally. Each of the three resin composite increments was light cured for 20 s using a light-curing unit (XL 3000, 3MESPE, St Paul MN, USA) with the intensity at 600 mW/cm 2 . Following storage in distilled water at 37 8C for 24 h, the bonded specimens were serially sectioned into 0.7 mmthick slabs using a low-speed diamond saw (Isomet; Buehler Ltd, Lake Bluff, IL 60044) and then trimmed with a superfine diamond bur to form hour-glass shapes with approximately 1 mm 2 cross-sectional areas (nZ20) using a digital micrometer. The specimens were attached to a table-top material tester (EZ-test, Shimadzu Co, Kyoto, Japan) with a cyanoacrylate glue (Zapit, DVA, Anaheim, CA, USA) and subjected to microtensile testing at a crosshead speed of 1 mm/min until they fractured. All of the bonded specimens were capable of being tested. In order to observe the failure modes, the debonded specimens were fixed for at least 8 h in 10% neutral buffered formalin, placed on stubs followed by room desiccation, gold sputter-coated and observed with a scanning electron microscopy (JXA-5400, JEOL, Tokyo, Japan). Failure modes were classified into one of four categories: adhesive if debonding occured between resin and dentin, mixed if it exhibited partially adhesive, partially cohesive failure in bonding resin or in hybrid layer, or cohesive in resin or cohesive in dentin. Two-way ANOVA was performed to evaluate the effect of two experimental factors: adhesive type and application technique, and the interaction of these two factors on mTBS. Multiple comparisons were performed by Tukey’s post hoc test at a significance level of 0.05 using a computer software (SPSS 11, SPSS Inc Chicago IL). Failure modes of the specimens were analyzed using chi-square test. Scanning electron microscopy Four non-carious third molars (one per group) were used for SEM examination of the resin-dentin interfaces after argon ion etching. The teeth were prepared in the same manner as the bonding procedure and then sectioned longitudinally to the bonding surface under running water using a lowspeed diamond saw (Isomet, Buehler Ltd, Lake Bluff IL, USA) and stored for 24 h in neutral formalin. The specimens were then embedded in epoxy resin (Epon 815, NISSIN EM Co Ltd, Tokyo, Table 2 Bonding procedures. Groups Application procedures One-Step Plus total-etch Apply etchant for 15 s, rinse etchant, slightly dry, leaving moist, apply adhesive in two coats, air dry adhesive, light cure adhesive for 10 s One-Step Plus self-etch Air dry dentin for 5 s, apply Tyrian SPE in two coats, air dry primer, apply adhesive in two coats, air dry adhesive, light cure adhesive for 10 s One-Step total-etch Apply etchant for 15 s, rinse etchant, slightly dry, leaving moist, apply adhesive in two coats, air dry adhesive, light cure adhesive for 10 s One-Step self-etch Air dry dentin for 5 s, apply Tyrian SPE in two coats, air dry primer, apply adhesive in two coats, air dry adhesive, light cure adhesive for 10 s
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<strong>Microtensile</strong> <strong>bond</strong> <strong>strength</strong> <strong>of</strong> <strong>adhesive</strong> <strong>to</strong> <strong>dentin</strong> using self-etch and <strong>to</strong>tal-etch technique 285<br />
Table 1 Materials used in the study.<br />
Materials Composition Manufacturer<br />
One-Step Plus Bis-GMA, BPDM, HEMA, CQ, p-dimethylaminobenzoic acid<br />
(co-initia<strong>to</strong>r), ace<strong>to</strong>ne, 8.5% glass fillers<br />
Bisco Inc, USA<br />
One-Step Bis-GMA, BPDM, HEMA, ace<strong>to</strong>ne Bisco Inc, USA<br />
Tyrian SPE Primer A: thymol blue, ethanol, water<br />
Primer B: AMPS, BisMEP, TPO, ethanol<br />
Bisco Inc, USA<br />
Uni-etch 32% Phosphoric acid, BAC Bisco Inc, USA<br />
Clearfil AP-X Bis-GMA, TEGDMA, filler (Barium, SiO2) Kuraray Co, Japan<br />
BPDM, Biphenyl-dimethacrylate; HEMA, 2-hydroxyethyl-methacrylate; Bis-GMA, Bisphenyl-glysidyl-methacrylate; AMPS, 2-<br />
Acrylamido-2-methylpropanesulfonic acid; BisMEP, Bis(2-(methacryloyloxy)ethyl)phosphate; TEGDMA, Triethylene glycol-dimethacrylate<br />
TPO:2,4,6 (trimethylbenzoyldiphenylphosphine) oxide; BAC, Benzalkonium chloride.<br />
instructions and summarized in Table 2. Then a<br />
resin composite (Clearfil AP-X; Kuraray Medical<br />
Co, Ltd, Tokyo, Japan) was built up incrementally.<br />
Each <strong>of</strong> the three resin composite increments<br />
was light cured for 20 s using a light-curing<br />
unit (XL 3000, 3MESPE, St Paul MN, USA) with the<br />
intensity at 600 mW/cm 2 . Following s<strong>to</strong>rage in<br />
distilled water at 37 8C for 24 h, the <strong>bond</strong>ed<br />
specimens were serially sectioned in<strong>to</strong> 0.7 mmthick<br />
slabs using a low-speed diamond saw<br />
(Isomet; Buehler Ltd, Lake Bluff, IL 60044) and<br />
then trimmed with a superfine diamond bur <strong>to</strong><br />
form hour-glass shapes with approximately 1 mm 2<br />
cross-sectional areas (nZ20) using a digital<br />
micrometer.<br />
The specimens were attached <strong>to</strong> a table-<strong>to</strong>p<br />
material tester (EZ-test, Shimadzu Co, Kyo<strong>to</strong>,<br />
Japan) with a cyanoacrylate glue (Zapit, DVA,<br />
Anaheim, CA, USA) and subjected <strong>to</strong> microtensile<br />
testing at a crosshead speed <strong>of</strong> 1 mm/min until they<br />
fractured. All <strong>of</strong> the <strong>bond</strong>ed specimens were<br />
capable <strong>of</strong> being tested. In order <strong>to</strong> observe the<br />
failure modes, the de<strong>bond</strong>ed specimens were fixed<br />
for at least 8 h in 10% neutral buffered formalin,<br />
placed on stubs followed by room desiccation, gold<br />
sputter-coated and observed with a scanning<br />
electron microscopy (JXA-5400, JEOL, Tokyo,<br />
Japan). Failure modes were classified in<strong>to</strong> one <strong>of</strong><br />
four categories: <strong>adhesive</strong> if de<strong>bond</strong>ing occured<br />
between resin and <strong>dentin</strong>, mixed if it exhibited<br />
partially <strong>adhesive</strong>, partially cohesive failure in<br />
<strong>bond</strong>ing resin or in hybrid layer, or cohesive in<br />
resin or cohesive in <strong>dentin</strong>.<br />
Two-way ANOVA was performed <strong>to</strong> evaluate the<br />
effect <strong>of</strong> two experimental fac<strong>to</strong>rs: <strong>adhesive</strong> type<br />
and application technique, and the interaction <strong>of</strong><br />
these two fac<strong>to</strong>rs on mTBS. Multiple comparisons<br />
were performed by Tukey’s post hoc test at a<br />
significance level <strong>of</strong> 0.05 using a computer s<strong>of</strong>tware<br />
(SPSS 11, SPSS Inc Chicago IL). Failure modes <strong>of</strong> the<br />
specimens were analyzed using chi-square test.<br />
Scanning electron microscopy<br />
Four non-carious third molars (one per group)<br />
were used for SEM examination <strong>of</strong> the resin-<strong>dentin</strong><br />
interfaces after argon ion etching. The teeth were<br />
prepared in the same manner as the <strong>bond</strong>ing<br />
procedure and then sectioned longitudinally <strong>to</strong> the<br />
<strong>bond</strong>ing surface under running water using a lowspeed<br />
diamond saw (Isomet, Buehler Ltd, Lake<br />
Bluff IL, USA) and s<strong>to</strong>red for 24 h in neutral<br />
formalin. The specimens were then embedded in<br />
epoxy resin (Epon 815, NISSIN EM Co Ltd, Tokyo,<br />
Table 2 Bonding procedures.<br />
Groups Application procedures<br />
One-Step Plus <strong>to</strong>tal-etch Apply etchant for 15 s, rinse etchant, slightly dry, leaving moist, apply <strong>adhesive</strong><br />
in two coats, air dry <strong>adhesive</strong>, light cure <strong>adhesive</strong> for 10 s<br />
One-Step Plus self-etch Air dry <strong>dentin</strong> for 5 s, apply Tyrian SPE in two coats, air dry primer, apply <strong>adhesive</strong><br />
in two coats, air dry <strong>adhesive</strong>, light cure <strong>adhesive</strong> for 10 s<br />
One-Step <strong>to</strong>tal-etch Apply etchant for 15 s, rinse etchant, slightly dry, leaving moist, apply <strong>adhesive</strong><br />
in two coats, air dry <strong>adhesive</strong>, light cure <strong>adhesive</strong> for 10 s<br />
One-Step self-etch Air dry <strong>dentin</strong> for 5 s, apply Tyrian SPE in two coats, air dry primer, apply <strong>adhesive</strong><br />
in two coats, air dry <strong>adhesive</strong>, light cure <strong>adhesive</strong> for 10 s
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