l s 2

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.

2 8 S

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owaVptt–

ural

n (SD

(12.3(14.9(8.28(5.27(14.1(14.6(7.39(13.5

∗

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

Materials and methods: Thirty-two artificial molars (Vita-an,Vita) were ground flat at their base, and a bonding agent

Vitacol, Vita) was applied to the surface, prior to acrylic resinondensation (Lucitone 550, Dentsply). Control group receivedo treatment, was heat-cured in water, and was not submit-ed to thermal-cycling. Three factors were defined: surfacereatment, polymerization type (microwave or heat-curing),nd thermal-cycling (10,000 cycles – 5–55 ◦C, 30 s dwell time).fter acrylic resin polymerization, samples were sectioned

o obtain non-trimmed i-shaped specimens for micro-tensileond strength test, performed with Geraldeli’s JIG at cross-ead speed of 0.5 mm/min. Data (MPa) were submitted to-way ANOVA and to Tukey test, both with ˛ = 0.05.

Results: ANOVA showed no significance of isolated factorss well as for interactions between them.

Conclusions: The bond strength between artificial teethnd acrylic resin is not influenced by bonding agent. Polymer-zation type and thermal-cycling have also no effect on bondtrength.

ttp://dx.doi.org/10.1016/j.dental.2012.07.066

0ffect of thickness, processing technique and cooling oneramic strength

.M.C. Lima 1,∗, A.C.O. Souza 1, L.C. Anami 1, M.A. Bottino 1,.M. Melo 1, R.O.A. Souza 2

UNESP – Univ Estadual Paulista (FOSJC), BrazilFederal University of Paraiba (UFPB), Brazil

Objectives: To evaluate in vitro the influence of the appli-ation technique, thickness of veneering ceramic and coolingrotocol on the fracture strength of all-ceramic bilayered spec-

mens.Materials and methods: Sixty four bars (20 × 4 × 1 mm3)

f Y-TZP (Vita In-Ceram 2000 YZ Cubes, Vita Zahnfabrik)ere prepared and randomly divided into eight groups (n = 8)ccording to the factors “processing technique” (PM9 (PM9,ita Zahnfabrik) – pressed; and VM9 (VM9, Vita Zahnfabrik) –ower-liquid), “thickness” (1 mm and 3 mm) and “cooling pro-

Group Processingtechnique

Thickness(mm)

Cooling Flex

Mea

V1S VM9 1 Slow 68.9V1F VM9 1 Fast 66.8V3S VM9 3 Slow 48.0V3F VM9 3 Fast 55.0P1S PM9 1 Slow 68.8P1F PM9 1 Fast 72.1P3S PM9 3 Slow 51.2P3F PM9 3 Fast 52.7

ocol” (slow – the oven was not opened until 600 ◦C and fast –he oven was opened immediately after the firing cycle): V1SVM9, 1 mm, slow cooling; V1F – VM9, 1 mm, fast cooling; V3S

( 2 0 1 2 ) e1–e70 e27

– VM9, 3 mm, slow cooling; V3F – VM9, 3 mm, fast cooling; P1S– PM9, 1 mm, slow cooling; P1F – PM9, 1 mm, fast cooling; P3S– PM9, 3 mm, slow cooling; P3F – PM9, 3 mm, fast cooling. Allspecimens were subjected to 2 × 106 mechanical cycles with aload of 84 N, at a frequency of 3.4 Hz and temperature of 37 ◦C.The 4-point bending test was performed (1.0 mm/min, 1000 kgfload cell) with the porcelain under tensile and the maximumforce (N) for fracture was used to calculate the strength values(�, MPa). The failure mode was analyzed by optical microscopy(30×). The data were statistically analyzed using Analysis ofVariance (3-way) and Tukey test (5%).

Results:

strength Failure mode

)* (MPa) Cracking Delamination Catastrophic

4)AB 2 0 65)AB 6 2 0)C 5 2 1)ABC 3 5 02)AB 7 0 15)A 8 0 0)BC 4 1 33)BC 4 2 2

Values followed by similar letters did not present statistical difference(p > 0.05).

Conclusions: The increased thickness of the veneeringceramic significantly decreased the mechanical strength ofthe bilayered specimens, regardless of the application tech-nique and cooling protocol.

http://dx.doi.org/10.1016/j.dental.2012.07.067

61Lifetime of zirconia-veneer crowns under thermal residualstresses

U. Lohbauer 1,∗, R. Belli 1, R. Frankenberger 2, A. Petschelt 1

1 University of Erlangen-Nuremberg, Germany2 University of Marburg, Germany

Objectives: To investigate the effects of thermal residualstresses on the in vitro lifetime of zirconia-veneer crowns.

Materials and methods: Sixty-four second upper premo-lar zirconia-veneer crowns were manufactured for testingunder cyclic fatigue. Zirconia copings (YZ Cubes, CTE:˛c = 10.5 ppm/◦C) were milled and sintered to a final thicknessof 0.7 mm. The copings were veneered using two differentporcelains (VM9, VITA, CTE: ˛VM9 = 9.1 ppm/◦C; Lava Ceram,3MESPE, CTE: ˛Lava = 10.2 ppm/◦C) to result in crowns with bothhigh thermal mismatch (+1.4 ppm/◦C with VM9) and low ther-mal mismatch (+0.3 ppm/◦C with Lava Ceram). The porcelainswere applied by the same operator to a final thickness of

1.4 mm. After the last glaze firing the crowns were cooledfollowing a fast (600 ◦C/min) or a slow (30 ◦C/min) cooling pro-tocol. The glazed crowns were submitted to a sliding-motion(0.7 mm lateral movement) cyclic fatigue in a chewing simu-