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acteria was inoculated and the experimental groups wereivided. There were three experimental groups of 5 subjectsach treated for 1, 2 and 3 min; Group A: left at room temper-ture and hydrogen peroxide solution; Group B: microwavereated; Group C: specimens were left on the tissue cul-ure net (28 mm × 40 mm × 6 mm) in 20 mL hydrogen peroxideolution (3%, w/v, Songkwang Co., Bucheon, Korea). All micro-ial materials were spread on the selective media for S.utans and E. coli. After incubation (37 ◦C, 24 h), the numberf colony-forming units (CFU/mL) was counted. The data weretatistically analyzed by one-way ANOVA, followed by Tukey-est (p = 0.05).

Results: All the disinfection methods were shown to beffective on reducing CFU/mL for both S. mutans and E. coliompared to the control. Also, there was significant differencen CFU/mL of both S. mutans and E. coli between groups treatedith H2O2 only, microwave only and microwave + H2O2. The

ignificant reduction in CFU/mL of both bacteria was notedhen combination of microwave + H2O2 was used compared

o using microwave or H2O2 solely.Conclusions: The microwave irradiation was identified as

seful disinfection method for S. mutans and E. coli, especiallyhen combined with H2O2.

ttp://dx.doi.org/10.1016/j.dental.2012.07.060

4lexural strength of ceramics: Influence of ultrasonic bathfter etching

. Cotes 1,∗, V.C. Macedo 1, L.V. Zogheib 2, C.S.M. Martinelli 1,

.F. Carvalho 1, E.T. Kimpara 1

UNESP – Univ Estadual Paulista, BrazilUSC, Brazil

Objectives: The hydrofluoric etching (HF) generates a sig-ificant amount of crystalline debris, thus contaminatinghe porcelain surface (Magne, Cascione. J Prosthet Dent006;96:354), which may be eliminated. The purpose of thistudy was to compare the flexural strength of ceramic barstched and submitted to an ultrasonic bath after etching.

Materials and methods: Ceramic lithium disilicate blocksIPS e.max CAD, Ivoclar Vivadent) were sectioned in a cutting

achine. The bars were polished with sandpaper and sub-itted to an ultrasonic bath cleaning (5 min). After sintering

rocess, the bars had dimensions of 16 mm × 2 mm × 1.5 mm.hey were divided into three groups (n = 10): (C) control, with-ut any surface treatment; (S) etched with HF 10% for 90 s,ashed for 30 s, and silane (Monobond S, Ivoclar Vivadent)

pplication; and (U) etched with HF 10% for 90 s, washed for0 s, submitted to an ultrasonic bath (5 min) in distilled water,nd silane application. Then, all specimens received a layer ofuting agent (Variolink II, Ivoclar Vivadent). The three-pointexural test was performed in a universal testing machineith a speed of 0.5 mm/min and the values of flexural strengthere analyzed statistically by ANOVA one-way test.

Results: There was no statistical difference in the values of

exural strength (p = 0.163) for the three groups.

Conclusions: The ultrasonic bath did not influence the flex-ral strength of a lithium disilicate ceramic after etching when

( 2 0 1 2 ) e1–e70 e25

it was compared with the groups where no ultrasonic bath wasperformed.

http://dx.doi.org/10.1016/j.dental.2012.07.061

55Bi-axial flexural strength of experimental zirconia-based sys-tems

G.M.D. De Souza 1,∗, K. Monteiro 2, H.N. Yoshimura 3, P.F.Cesar 2

1 University of Toronto, Canada2 University of Sao Paulo, Brazil3 Federal University of ABC, Brazil

Objectives: There is a current necessity for more stablezirconia-based systems with high mechanical properties. Theaim of this study was to evaluate bi-axial flexural strengthof experimental Y-TZP (yttria–tetragonal zirconia polycrystal)and ZTA (zirconia toughened alumina) in comparison to acommercially available Y-TZP system.

Materials and methods: Experimental blocks(16 × 16 × 42 mm3) were produced with 28 g of 3-YSB powder(Tosoh Corporation) (Y-TZP blocks – EZ) or a mixture of3-YSB (15 vol%) and alumina CT-3000SDP (Almatis AC Inc.)(85 vol%) (ZTA blocks – ZA). Powder was pressed using bi-axialpressing technique and all the blocks were pre-sintered(Jung Company). Compressive load and pre-sintering cycleswere adjusted to match the density of the current systemsavailable. Pre-sintered commercial Y-TZP blocks (CZ) wereconsidered as control (Vita InCeram YZ, Vita Zahnfabrik).Blocks (n = 5) were cut with diamond saw to obtain 6 slicesfrom each, which were polished up to 1 �m diamond sus-pension and fully sintered before being submitted to bi-axialflexural strength (piston-on-three balls). Data was analyzed byone-way ANOVA and Tukey test at 5% significance level.

Results: Bi-axial flexural strength values were:EZ – 698.5 (±110.7) MPa; ZA – 534.4 (±125) MPa; CZ –865.1 (±147.6) MPa. One-way ANOVA evidenced significantdifference and Tukey test (˛ = 0.05) showed that CZ presentedhigher bi-axial flexural strength than EZ (p < 0.001) and ZA(p < 0.001). EZ also presented higher bi-axial flexural strengththan ZA (p < 0.001).

Conclusions: Commercial zirconia presented higher bi-axial flexural strength than experimental zirconia-basedsystems. To develop an experimental system, parameters suchas sintering shrinkage, marginal fit, mechanical propertiesand phase stability must all be considered together.

http://dx.doi.org/10.1016/j.dental.2012.07.062

56Flexural strength of rebased and fiber reinforced acrylic resins

F.C.P. Goncalves ∗, T.J.A. Paes Junior, A.L.S. Borges, R.N. Tango,I. Balducci

Universidade Estadual Paulista – UNESP-FOSJC, Brazil

Objectives: The aim of this study was to evaluate someproperties of acrylic resins when reinforced with a modifiednylon fiber.

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e26 d e n t a l m a t e r i a

Materials and methods: A microwave heat cured acrylicresin (RAAT) (Vipi-Wave) and a hard self-cured acrylic resinfor rebasing (Tokuso) were tested for flexural strength. Barshaped specimens 20 mm × 10 mm × 3 mm (n = 9) were testedas follows: G1: RAAT; G2: RAAT with nylon fiber; G3: RAAT withsilica modified nylon fiber; R1: RAAT rebased with hard liner;R2: RAAT rebased with hard liner and reinforced with nylonfiber; R3: RAAT rebased with hard liner reinforced with silicamodified nylon fiber. Three point bending test was used in auniversal testing machine after specimen storage in distilledwater at 37 ◦C for 48 h and the results for flexural strength wereobtained in MPa. Data were submitted to ANOVA and Tukeytest (5%).

Results: Mean and standard deviation for groups were: G1– 75.40 ± 3.11a, G2 – 109 ± 10.91b, G3 – 152.50 ± 14.84c, R1 –54.65 ± 2.99d, R2 – 79.30 ± 2.34a, R3 – 105.55 ± 6.02b (mean val-ues with different upper case letters represent statisticallysignificant differences). The higher flexural strength valueresults were obtained with silica modified nylon fiber rein-forcement, and lowest values in the group with relining withno reinforcement.

Conclusions: The use of a reinforcing fiber increased theflexural strength of acrylics resins. The use of liner decreasedstrength in all tested groups.

http://dx.doi.org/10.1016/j.dental.2012.07.063

57Effect of cleaning methods in the surface roughness of ceram-ics

E.T. Kimpara 1,∗, C. Cotes 1, V.C. Macedo 1, L.V. Zogheib 2,C.S.M. Martinelli 1, R.F. Carvalho 1

1 UNESP – Univ Estadual Paulista, Brazil2 USC, Brazil

Objectives: The hydrofluoric etching (HF) generates a sig-nificant amount of crystalline debris, thus contaminatingthe porcelain surface (Magne, Cascione. J Prosthet Dent2006;96:354). This precipitate may be eliminated and the effectof HF may be stopped. The purpose of this study was to eval-uate the surface roughness of ceramic bars etched and thensubmitted to an ultrasonic bath, or neutralized with two neu-tralizing powders.

Materials and methods: Ceramic lithium disilicate blocks(IPS e.max CAD, Ivoclar Vivadent) were sectioned in a cuttingmachine. The bars were polished with sandpaper and sub-mitted to an ultrasonic bath cleaning (5 min). After sinteringprocess, the bars had dimensions of 16 mm × 2 mm × 1.5 mm.They were etched with HF 10% for 90 s, washed for 30 s, anddivided into four groups (n = 10): (C), control, without anycleaning method; (U), submitted to an ultrasonic bath for5 min; (N), neutralized with calcium and sodium carbonate(IPS Ceramic kit, Ivoclar Vivadent); and (B), neutralized withsupersaturated solution of sodium bicarbonate (Portuense).After neutralization, specimens were washed with air-waterspray (10 s). The surface roughness was analyzed in a contact

profilometer, and the values of Ra were tabulated and analyzedstatistically by ANOVA one-way and Tukey’s test.

8 S ( 2 0 1 2 ) e1–e70

Results: The values of roughness were statistically differ-ent (p = 0.001). The roughness mean was statistically lowerfor (B) group (0.03 ± 0.01 �m) than for other groups ((C):0.06 ± 0.01 �m; (U): 0.08 ± 0.01 �m; and (N): 0.07 ± 0.00 �m).

Conclusions: The ultrasonic bath and the neutralizationwith calcium and sodium carbonate did not alter the rough-ness of a lithium disilicate ceramic after etching, when it wascompared with no neutralization, but the neutralization withsodium bicarbonate decreased the surface roughness.

http://dx.doi.org/10.1016/j.dental.2012.07.064

58The influence of disinfection on dimensional stability of tem-porary crowns

P.C.P. Komori ∗, L.M.R. Almedia, S.C.M. Cavalcanti, E.T.Kimpara, T.J.A. Paes Junior

Universidade Estadual Paulista Júlio de Mesquita Filho, Brazil

Objectives: The aim of this study was to evaluate theinfluence of different disinfection methods on dimensionalstability of temporary acrylic resin crowns.

Materials and methods: This study evaluated specimensof temporary acrylic resin crowns. A metallic die with twodifferent marks at the margin was used to prepare thespecimens. Two different resins were evaluated (bis-acrylicresin-Structure, acrylic resin-Dencrilay). They were dividedinto ten groups (n = 8) determined according to the disin-fection procedure (microwave, acetic acid, 1% hypochlorite,4% chlorhexidine). In the control group, the specimens wereimmersed in distilled water at 37 ◦C. The marginal adaptationof temporary crowns was examined comparing two differentmarks on the margin of the crowns. The crowns were eval-uated with a stereomicroscope at 2 points along the entirecircumferential margin for measuring the margin adaptationbefore and after disinfection procedures and the control.

Results: Results were compared statistically by ANOVA andTukey’s test (p ≤ 0.05). No significant differences were foundbetween the disinfection procedures and the control group,but all procedures affected the marginal stability. The mar-gin discrepancy varied with the resinous material. The acrylicresin exhibited significantly more discrepancy at the margin.

Conclusions: Within the limits of this in vitro study it couldbe concluded that all procedures affected the marginal stabil-ity of the samples. However, all values obtained for the acrylicresins showed more discrepancy.

http://dx.doi.org/10.1016/j.dental.2012.07.065

59Surface treatment on artificial tooth/acrylic resin bondstrength

R.A. Lara ∗, R.N. Tango, G.F.S.A. Saavedra

UNESP – Univ Estadual Paulista, Deparment of Dental Materialsand Prosthodontics, São José dos Campos, Brazil

Objectives: The aim of this study was to evaluate the effectof an adhesive bonding agent and thermocycling on artificialtooth bond strength to microwave-cured acrylic resin.