e34 d e n t a l m a t e r i a l s 2 9 S ( 2 0 1 3 ) e1–e96

(n = 10). The control group remained untreated, while theexperimental groups were tested for 3 HP concentrations

(10%, 35% and 50%). The solutions were applied, respec-tively, every 30 min to the enamel, and they were analyzedafter each application. The MC of the enamel was deter-mined before and after the bleaching using Fourier transform(FT-Raman) spectroscopy and micro energy-dispersive X-rayfluorescence spectrometry (�EDXRF). The calcium (Ca) lostfrom the bleached enamel was quantified with an atomicabsorption spectrometer (AAS). The data were statisticallyanalyzed by the ANOVA, Tukey and Dunnett’s test (p = 0.05).

Results: The FT-Raman showed a decrease in MC for allbleaching treatments, without influence of the three differentconcentrations of HP or the number of applications. �EDXRFdid not detect any changes in MC.

Conclusion: Ca loss was observed by the AAS, with no dif-ference among the 3 HP concentrations. The FT-Raman andAAS analysis detected reduction of MC and Ca loss after HPbleaching.

http://dx.doi.org/10.1016/j.dental.2013.08.071

71

Color stability of infiltrant resin exposed todifferent staining solutions

A.B. Borges ∗, T.M.F. Caneppele, M.A. Luz, C.R.Pucci, C.R.G. Torres

University Estadual Paulista – UNESP, Brazil

Purpose: The aim of this study was to investigate the stain-ing behavior of the demineralized enamel infiltrated by lowviscosity resin.

Methods and materials: Bovine enamel cylindrical sam-ples (3 mm × 2 mm) were assigned into four groups (n = 45)according to the treatment: sound enamel (control), white spotlesion (WSL) + artificial saliva, WSL + daily application of 0.05%NaF, WSL + resin infiltration (Icon®, DMG). Artificial WSL wereproduced in groups with demineralization. After treatments,color was assessed by spectrophotometry, using CIE L*a*b* sys-tem. The specimens (n = 15) were then immersed in deionizedwater, red wine or coffee for 10 min daily during 8 days. Colorwas measured again and the specimens were repolished withsandpaper discs. The final color was assessed. Data were ana-lyzed by two-way ANOVA and Tukey tests (a = 0.05). Pairedt-test was used for comparison between staining and repol-ishing conditions.

Results: The results are presented in the table.Conclusion: The exposure of specimens to colored solu-

tions resulted in significant color alteration. The white spotlesions treated with resin infiltration showed significantly

higher staining than all other tested groups, however, repol-ishing of the specimens minimized the staining effect.

Groups Sound enamel White spot lesion + AS White spot lesion + DF White spot lesion + RI

�Ea �E2b �E1a �E2b �E1a �E2b �E1a �E2b

Water 2.4 (1.3)a 2.2 (0.9)AB 2.9 (1.6)a 2.0 (1.3)AB 2.7 (2.2)a 1.6 (1.8)A 2.3 (1.7)a 2.1 (0.9)ABWine 14.4 (4.2)c cd 10.1 (2.2)c C 11.1 (5.1)c bc 9.3 (5.4)c C 14.2 (2.7)c cd 8.4 (3.2)c C 17.3 (2.7)c de 14.7 (4.7)c DCoffee 14.5 (4.4)cd 8.1 (4.5)c C 9.5 (5.9)c b 8.4 (5.7)c C 7.3 (2.3)c b 6.0 (1.4)c BC 21.3 (4.3)c e 16.6 (4.3)c D

a Different lower case letters mean significant differences among thegroups for �E1 (p < 0.05).

b Different capital letters mean significant differences among thegroups for �E2 (p < 0.05).

c Significant difference between �E1 and �E2 for each substrate con-dition, using paired t-test (p < 0.05).

http://dx.doi.org/10.1016/j.dental.2013.08.072

72

Multiwalled carbon nanotube/nylon-6nanofiber-reinforced dental composite

A.L.S. Borges 1,∗, A.C. Souza 1, T.J.A. PaesJunior 1, T. Yoshida 2, M.C. Bottino 2

1 University Est. Paulista – UNESP, Sao Jose DosCampos, Brazil2 Indiana University, IN, USA

Purpose: The aims of this study were (1) to synthe-size/characterize both random and aligned multiwalledcarbon nanotubes/nylon-6 (MWCNT/N6) nanofibers and (2) todetermine the effect of nanofiber incorporation on the flexuralstrength (FS) of a dental composite (C).

Methods and materials: MWCNT were functionalized(MWCNT) using 12N HCl for 5 min, washed in DI waterand dried for 24 h at RT. N6 was dissolved at 10% inhexafluoro-2-propanol. Then, two distinct MWCNT concen-trations (0.5 and 1.5 wt.%) were added to the N6 solution,stirred overnight and sonicated before use. N6 nanofibersboth non-aligned/NA and aligned/A with and without MWCNTwere processed via electrospinning, as follows: G1-N6/NA, G2-N6/A, G3-N6/NA + 0.5%MWCNT, G4-N6/NA + 1.5%MWCNT, G5-N6/A + 0.5%MWCNT and G6-N6/A + 1.5%MWCNT. Morpholog-ical (SEM/TEM), chemical, and mechanical (tensile strength,TS), studies were carried out after vacuum drying nanofibersat RT for 2 days. Nanofiber sheets (2 mm × 2 mm × 20 mm),of all groups, were cut and used to prepare the composite(GrandioSO®-VOCO) specimens (n = 6) for flexural testing. Datawere analyzed by ANOVA 2-way and Tukey’s test (5%).

Results: G2(18.4 ± 2.3 MPa) and G5(19.7 ± 2.5 MPa) showedsignificantly higher tensile strength than G1(5.8 ± 1.8 MPa)regardless the MWCNT content (Table). The incorporation ofthe synthesized nanocomposites fibers enhanced significantlythe composite flexural strength (Table) when compared to thecontrol (without MWCNT) with better results associated withaligned N6 + 0.5% MWCNT nanofibers (G5 = 142.3 ± 2.2 MPa).

Conclusion: Collectively, our findings support the conclu-sion that multiwalled carbon nanotube/nylon-6 electrospun