e162 d e n t a l m a t e r i a l s 3 0 S ( 2 0 1 4 ) e1–e180

For compressive strength determination, cylinders of 1.5 cmin diameter and 3.0 cm in height (n = 5) were produced. Thewet strength was measured 1 h after the mixing started; anddry strength was obtained after one week storage at 37 ◦C,at cross-head speed of 0.5 mm/min. Linear expansion wasdetermined using a device containing mobile opposing wallscoupled to dial gages. Compressive strength data were ana-lyzed by ANOVA and Tukey test (alpha = 5%).

Results: No microbiological zone of inhibition was observedfor the control, whereas average halos of 12 and 15 mm weremeasured for the discs prepared with the solution of 65 and330 ppm, respectively. For both the wet and dry conditions,all experimental groups containing Ag showed a significantincrease in compressive strength (p = 0.001) in relation to con-trol. For the wet condition, the average strength increase incomparison to the control (49 ± 4 MPa) was 90%, and the groupshowing the highest strength was that containing 330 ppm(123 ± 8 MPa). For the dry condition, the average strengthincrease in comparison to the control (106 ± 3 MPa) was 50%,and the group showing the highest strength values werethose containing 65 and 330 ppm (respectively, 170 ± 8 and174 ± 5 MPa). There was no significant effect of Ag additionon the liner expansion of the tested specimens (p > 0.05); themean expansion values varied around 0.07%.

Conclusion: The addition of Ag nanoparticles to gypsumtype IV in concentrations of 65 and 330 ppm was able to signif-icantly inhibit the growth of microorganisms and increase thecompressive strength of the specimens; therefore this modifi-cation to the gypsum composition can be useful for infectioncontrol.

Keywords: Silver nanoparticles; Gypsum strength; Infectioncontrol

http://dx.doi.org/10.1016/j.dental.2014.08.328

328

Effect of adhesive/Nd:YAG laser associationon enamel erosive/abrasive wear

E. Crastechini 1, A.B. Borges 1,∗, K. Becker 2,T. Attin 2, C.R.G. Torres 1

1 UNESP, Brazil2 University of Zurich, Switzerland

Purpose: The aim of this study was to evaluate the effi-cacy of different self-etching adhesive systems associated or

not with the Nd:YAG laser on the protection against enamelerosive and abrasive wear.

Methods and materials: Bovine enamel specimens wereprepared, polished and subjected to initial erosion in 0.3%citric acid solution (5 min). The initial profiles of the enamelsurface were measured using a stylus profilometer. The spec-imens were randomly assigned into eight groups (n = 20): SB -Single Bond Universal (3M/ESPE); SB+L - Single Bond Univer-sal followed by laser irradiation (80 mJ−10 Hz); FB - FuturabondU (Voco); Group FB+L - Futurabond U followed by laser irra-diation; GEN - G-aenial Bond (GC); GEN+L - G-aenial Bondfollowed by laser irradiation; L - laser irradiation; C - No treat-ment (control). In the adhesive/laser association groups, thelaser was applied before light curing. After treatments, spec-imens were subjected to erosive/abrasive challenges, using0.3% citric acid (pH 2.6/2 min) and tooth brushing (40 cycles- 200 g load), 4× day/5 days. Surface loss was recovered pro-filometrically by comparison of baseline and final profiles.Adhesive layer thickness was also calculated profilometrically.Adhesive retention rates were analyzed with optical micro-scope at the end of the experiment (40×). Microhardness ofenamel surfaces treated with the adhesives was measured(Knoop indentation - 10 g/10 s). Data were analyzed using one-way ANOVA and Tukey’s test (5%).

Results: ANOVA showed significant difference for sur-face wear (p = 0.0001), layer thickness (p = 0.0001), retention(p = 0.0001) and microhardness (p = 0.0001). Mean values (±SD)and results of the Tukey’s test are presented in Table 1.

Conclusion: The application of the adhesive systemsFuturabond U and G-aenial Bond on enamel surface, as wellas the Nd:YAG laser irradiation alone, were able to reduceenamel wear. The use of laser after the adhesive systemsdid not improve their protective effect against enamel ero-sion/abrasion.

Keywords: Erosion; Enamel; Self-etching adhesives

http://dx.doi.org/10.1016/j.dental.2014.08.329

Table 1 – Means (±SD) of enamel wear, adhesive layer thickness, adhesive retention and microhardness analysis.

Groups* Wear Thickness Retention Microhardness

G-aenial 4.88 (±1.09)a 15.27 (±8.63)c 68.89 (±20.62)c 9.27 (±1.75)cLaser 5.04 (±0.99)a – – –Futurabond U 5.32 (±0.93)ab 5.06 (±1.96)a 54.53 (±24.80)abc 6.99 (±0.89)bG-aenial + Laser 5.46 (±1.27)abc 13.96 (±7.07)bc 59.90 (±19.79)abc 6.22 (±0.87)abSingle Bond U + Laser 5.78 (±1.12)abc 4.24 (±2.68)a 63.37 (±19.30)bc 15.48 (±2.51)dFuturabond U + Laser 6.23 (±1.25)bc 9.03 (±13.02)abc 42.23 (±17.68)a 10.67 (±1.58)cSingle Bond U 6.36 (±1.11)c 7.49 (±2.80)ab 47.78 (±18.29)ab 5.00 (±1.60)aControl 6.46 (±0.61)c – – –

∗ The sets followed by the same letters do not show significant differences in columns.